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The length of file names in early Unix

Posted: 2025-05-25 07:37:27

Early Unix's file system imposed significant limitations on filenames. Initially, the Version 1 file system only supported 6-character filenames with a 2-character extension, totaling 8. Version 2 extended this to 14 characters, but still without any directory hierarchy support. The move to a hierarchical file system with Version 5 further restricted filenames to 14 characters total, without separate extensions. This 14-character limit persisted for a surprisingly long time, even into the early days of Linux and BSD. The restrictions stemmed from the structure of the i-node, which held file metadata, and a focus on simplicity and efficient use of limited storage capacity. Later versions of Unix and its derivatives gradually increased the limit to 255 characters and beyond.

This blog post delves into the historical evolution of filename length limitations in early versions of the Unix operating system. The author, Chris Siebenmann, meticulously examines how these limitations arose, changed over time, and the underlying technical reasons behind them.

Initially, the very first versions of Unix, specifically Version 1 and Version 2, imposed a strict 14-character limit on filenames. This constraint stemmed from the structure of the directory entries themselves, which allocated a fixed 14-byte field for the filename. This 14-byte field not only held the filename itself but also included an inode number, making efficient storage and retrieval possible within the limitations of the then-current hardware.

As Unix progressed to Version 3, a seemingly minor yet significant change occurred. The filename length, while still fundamentally limited by the 14-byte field, could now effectively accommodate longer filenames—specifically, those up to 14 characters including the terminating null character. This meant that practical filenames were still capped at 13 characters. This modification was likely driven by the desire for slightly more flexibility in naming files, while still adhering to the underlying data structure limitations.

Siebenmann goes on to discuss the implications of this change and how it affected the user experience. While the single additional character might appear trivial, it provided slightly more breathing room for descriptive filenames, a growing need as the system and its usage evolved. He further clarifies that the often-cited 14-character limit is generally understood to refer to the practical limit after accounting for the null terminator, not the raw size of the allocated field. This distinction is crucial for accurately understanding the historical context and the actual limitations experienced by users.

The post highlights how these early constraints were a direct product of the hardware limitations and design choices of the time. Limited memory and storage capacity necessitated efficient data structures, and the 14-byte filename field represented a pragmatic compromise between functionality and resource utilization. The evolution from a hard 14-character limit to a 13-character limit (plus null terminator) reflects a continuous striving for improvement within the existing technical constraints. Understanding this historical context provides valuable insights into the development of Unix and the factors that shaped its early design philosophy.

Summary of Comments ( 36 )
https://news.ycombinator.com/item?id=44086219

HN commenters discuss the historical context of early Unix filename limitations, with some pointing out that PDP-11 directories were effectively single-level and thus short filenames were less problematic. Others mention the influence of punched cards and teletypes on early computing conventions, including filename length. Several users shared anecdotes about working with these older systems and the creative workarounds employed to manage the restrictions. The technical reasons behind the limitations, such as inode structure and memory constraints, are also explored. One commenter highlights the blog author's incorrect assertion about the original ls command, clarifying its actual behavior with early Unix versions. Finally, the discussion touches on the evolution of filename lengths in later Unix versions and other operating systems.

The Hacker News post titled "The length of file names in early Unix" (https://news.ycombinator.com/item?id=44086219) sparked a discussion with several interesting comments. The conversation revolves around the historical context of filename length limitations in early Unix systems and the reasons behind those limitations.

Several commenters delve into the technical constraints of the era. One points out the limited memory capacity of early hardware and the impact this had on data structure design. They explain how the i-node structure, with its fixed-size array for storing filenames, directly influenced the maximum filename length. Another commenter adds to this by mentioning the trade-off between filename length and overall filesystem performance. Longer filenames would have required more complex data structures and algorithms, potentially slowing down other file operations.

The discussion also touches upon the evolution of Unix and how these limitations were addressed in later versions. One commenter notes that the initial restrictions were less of a practical problem in the early days of Unix, as systems were typically used by a small group of technically savvy users who were accustomed to such constraints. As Unix became more widespread, the need for longer filenames became apparent, leading to changes in the filesystem architecture.

A few comments provide anecdotal evidence of working with these early systems. One commenter recounts their experience with a PDP-11, highlighting the challenges posed by the short filename limitations. Another commenter shares a story about how the limitations sometimes led to creative filename conventions and abbreviations.

One compelling thread explores the broader implications of these early design choices. A commenter argues that the constraints imposed by limited resources often forced developers to be more creative and efficient, leading to elegant and minimalist solutions. They suggest that the early Unix philosophy of "doing one thing well" was partly a consequence of these limitations.

The comments section also features some technical debates. One such debate revolves around the specific details of the i-node structure and how filename lengths were stored. Different commenters offer varying interpretations based on their understanding of the historical documentation and source code.

Overall, the comments on the Hacker News post provide a valuable glimpse into the history of Unix and the factors that influenced its development. They offer a mix of technical explanations, personal anecdotes, and philosophical reflections on the impact of early design choices. The discussion showcases the collective knowledge and diverse perspectives of the Hacker News community, offering insights that go beyond the original blog post.

What were the MS-DOS programs that the moricons.dll icons were intended for?

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Posted: 2025-05-13 11:06:58

The moricons.dll file in Windows contains icons originally designed for Microsoft's abandoned "Cairo" operating system project. These icons weren't repurposed from existing applications but were newly created for Cairo's planned object-oriented filesystem and its associated utilities. While some icons depict generic concepts like folders and documents, others represent specific functionalities like object linking and embedding, security features, and mail messaging within the Cairo environment. Ultimately, since Cairo never shipped, these icons found a home in various dialogs and system tools within Windows 95 and later, often used as placeholders or for functionalities not explicitly designed for.

Raymond Chen's blog post, "What were the MS-DOS programs that the moricons.dll icons were intended for?", delves into the historical mystery surrounding a set of 16x16 pixel icons found within the moricons.dll file, a component of older versions of Windows. These icons, depicting various graphical elements like scissors, a pencil, an airbrush, and musical notes, never seemed to appear anywhere in the Windows user interface, prompting the question of their intended purpose.

Chen's investigation begins by acknowledging the community speculation that these icons were potentially destined for an unreleased or abandoned project. He explains that Windows 95 and its contemporaries allowed MS-DOS programs to specify custom icons within their program executable files. However, a common challenge was the limited disk space available on floppy disks, the primary distribution medium for software at the time. Including many icons, especially color icons, could significantly increase the size of a program's executable, making distribution on floppy disks more difficult.

To address this, Microsoft developed the concept of shared icon libraries. These libraries, like moricons.dll, would store collections of icons that MS-DOS programs could reference, thus avoiding the need to embed the icons directly within their executables. An MS-DOS program could then specify the desired icon by referencing its index within the shared library, keeping the program's size smaller.

Chen highlights how the Windows 95 resource compiler, the tool used to create program resources like icons, facilitated this process. Developers could define an icon resource and point it to the shared library, specifying the icon's index within the library. This mechanism enabled MS-DOS programs to utilize visually rich icons while minimizing their footprint.

However, the mystery of the unused moricons.dll icons deepens with the realization that the icons appear to be specifically designed for multimedia applications, a domain not typically associated with MS-DOS programs. Chen postulates that these icons were likely created in anticipation of, or perhaps in conjunction with, a multimedia-focused extension or shell for MS-DOS. This hypothetical extension might have leveraged these icons to provide a more graphical interface for interacting with multimedia content under MS-DOS.

Despite the lack of concrete evidence, the blog post concludes that the most plausible explanation is that these icons were indeed intended for such a multimedia extension or shell for MS-DOS. While the exact nature and fate of this potential project remain unknown, the icons serve as a tantalizing glimpse into a possible, yet unrealized, direction for the evolution of the MS-DOS environment. They stand as a testament to the rapidly changing technological landscape of the time and the various paths explored by Microsoft in the early days of Windows.

Summary of Comments ( 61 )
https://news.ycombinator.com/item?id=43971616

Hacker News users discuss the mystery surrounding the unused icons in moricons.dll, speculating about their purpose and the development process at Microsoft. Some suggest the icons were placeholders for future features or remnants of abandoned projects, possibly related to Cairo or object linking and embedding (OLE). One commenter links to a blog post claiming the icons were for a "Mac-on-DOS" environment called "Cougar," intended to make porting Macintosh software easier. Other comments focus on the general software development practice of leaving unused resources in code, attributing it to factors like time constraints, changing priorities, or simply forgetting to remove them. A few users recall encountering similar unused resources in other software, highlighting the commonality of this phenomenon.

The Hacker News post "What were the MS-DOS programs that the moricons.dll icons were intended for?" generated a moderate amount of discussion, with several commenters providing insights and speculation.

One of the most compelling threads revolved around the purpose of these icons and why they seemed somewhat out of place for MS-DOS programs. Several commenters suggested that these icons were likely intended for a hypothetical or planned GUI environment for MS-DOS, which never fully materialized. They pointed to other similar initiatives from Microsoft around that time, like the short-lived "DOS Shell," as evidence that Microsoft was exploring graphical interfaces even before Windows 3.0 gained widespread adoption. This theory was supported by the more modern and detailed appearance of the icons compared to the simpler, character-based graphics typical of MS-DOS applications.

One commenter specifically hypothesized that the icons might have been intended for a "Windows-like" file manager for MS-DOS, perhaps even a precursor to the later Windows File Manager. This idea resonated with others, who noted the resemblance of some icons to later Windows icons.

Another user posited that these icons might have been utilized within the "MS-DOS Editor," suggesting they could have represented different file types or actions within the editor itself. However, this theory didn't gain much traction, with no other users confirming seeing icons in this context.

A few commenters focused on the technical aspects, discussing the format of the icons and the tools used to extract them. They mentioned the resource hacker utility and the internal structure of DLL files. This discussion, while technical, offered insight into how these icons were discovered and examined.

Finally, some comments simply expressed appreciation for the historical curiosity of the topic, enjoying the glimpse into a potential alternative path in the evolution of personal computing. They reflected on the rapid pace of technological change during that era and how these seemingly forgotten artifacts can offer fascinating glimpses into what might have been.

While there wasn't a definitive answer regarding the intended use of the moricons.dll icons, the prevailing theory pointed towards a planned, but ultimately abandoned, graphical interface for MS-DOS. The comments collectively offered a blend of technical analysis, historical context, and informed speculation, painting a picture of Microsoft's experimentation in the transition from the command-line world of MS-DOS to the graphical world of Windows.

Can you trust that permission pop-up on macOS?

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Posted: 2025-05-12 18:26:44

macOS's Transparency, Consent, and Control (TCC) pop-ups, designed to protect user privacy by requesting permission for apps to access sensitive data, can be manipulated by malicious actors. While generally reliable, TCC relies on the accuracy of the app's declared bundle identifier, which can be spoofed. A malicious app could impersonate a legitimate one, tricking the user into granting it access to protected data like the camera, microphone, or even full disk access. This vulnerability highlights the importance of careful examination of TCC prompts, including checking the app's name and developer information against known legitimate sources before granting access. Even with TCC, users must remain vigilant to avoid inadvertently granting permissions to disguised malware.

The blog post "Can you trust that permission pop-up on macOS?" delves into the intricacies of the Transparency, Consent, and Control (TCC) framework in macOS, which governs how applications access sensitive resources like the camera, microphone, location, and files. The author argues that while TCC presents a seemingly straightforward interface for user consent, the underlying mechanisms are complex and can be manipulated, leading to potential security and privacy risks.

The core issue revolves around the concept of TCC databases. These databases store the granted permissions for each application. Crucially, these databases are not solely controlled by the system. Applications themselves, using the TCC API, can programmatically add entries to their own databases, essentially granting themselves permissions without explicit user interaction through the familiar pop-up dialog. This self-granted permission isn't absolute; it's limited to the specific application making the request and doesn't extend system-wide. However, it allows an application to bypass the standard user authorization flow, potentially raising concerns if a malicious actor gains control of a legitimate application.

The post further explains that the reliance on application bundles plays a role in this dynamic. Because permissions are tied to the bundle identifier, a malicious actor modifying an application's bundle can potentially inherit pre-existing permissions granted to the original, legitimate application. This can be particularly problematic if an application's update mechanism is compromised, allowing a malicious update to assume existing permissions without prompting the user.

The author emphasizes that this isn't necessarily a "vulnerability" in the traditional sense, but rather a design characteristic of TCC that can be exploited. The flexibility afforded to applications for managing their own permissions can be beneficial in legitimate use cases, streamlining certain workflows. However, this same flexibility creates an attack surface that can be leveraged for malicious purposes. The post concludes by highlighting the need for users to be vigilant about the applications they install and run, especially from untrusted sources, given the potential for bypassing the standard permission prompts. The inherent trust placed in application bundles and the potential for their manipulation underscores the importance of secure software distribution and update mechanisms to mitigate the risks associated with TCC's design.

Summary of Comments ( 225 )
https://news.ycombinator.com/item?id=43966089

Hacker News users discuss the trustworthiness of macOS permission pop-ups, sparked by an article about TinyCheck. Several commenters express concern about TCC's complexity and potential for abuse, highlighting how easily users can be tricked into granting excessive permissions. One commenter questions if Apple's security theater is sufficient, given the potential for malware to exploit these vulnerabilities. Others discuss TinyCheck's usefulness, potential improvements, and alternatives, including using tccutil and other open-source tools. Some debate the practical implications of such vulnerabilities and the likelihood of average users encountering sophisticated attacks. A few express skepticism about the overall threat, arguing that the complexity of exploiting TCC may deter most malicious actors.

The Hacker News post "Can you trust that permission pop-up on macOS?" (linking to an article about TCC, the Transparency, Consent, and Control framework in macOS) generated a moderate amount of discussion with several insightful comments.

Several users discussed the complexities and nuances of TCC. One user highlighted the "security vs. usability" trade-off inherent in such systems, pointing out that while TCC is designed for security, it can lead to frustrating user experiences, especially for power users or those working with complex setups. This prompted further discussion about how Apple could potentially improve the user experience without compromising security, with suggestions like more granular permissions or better explanations of why certain permissions are required.

Another commenter brought up the issue of "TCC bypasses," explaining how some applications have found ways to circumvent the TCC framework, raising concerns about the effectiveness of the system in truly protecting user privacy. They also mentioned the "cat-and-mouse game" between Apple and developers seeking to bypass these restrictions.

The topic of sandboxing apps also emerged. A commenter explained how sandboxing, combined with TCC, forms a layered defense mechanism. They noted that even if an app manages to bypass TCC, the sandbox can still restrict its access to sensitive data and system resources. Another commenter elaborated on the concept of "entitlements," which grant specific privileges to sandboxed apps. This led to a discussion about the potential risks associated with overly permissive entitlements.

One user shared a personal anecdote about a frustrating experience with TCC, where they had difficulty granting an app the necessary permissions to access files on an external drive. This highlighted the practical challenges users can face with TCC in real-world scenarios.

A few comments touched on the differences between TCC and similar permission systems on other operating systems, with some suggesting that Apple's approach is generally more robust.

Finally, there was a brief discussion about the technical details of TCC, including how it uses a database to store permission grants and how this database can be inspected by users.

Overall, the comments section provides valuable insights into the strengths and weaknesses of TCC, highlighting the ongoing tension between security and usability, and offering various perspectives on how the system could be improved. While no single comment is overwhelmingly compelling on its own, the collection of comments paints a comprehensive picture of the complexities and challenges associated with managing permissions in a modern operating system.

RIP Usenix ATC

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Posted: 2025-05-12 16:29:05

Bryan Cantrill laments the decline of the USENIX Annual Technical Conference (ATC), attributing it to a shift away from its core focus on systems research towards more mainstream, less technically rigorous topics. He argues that this broadening scope, driven by a desire for larger attendance and influenced by the "open source" movement, has diluted the conference's identity and diminished its value for hardcore systems researchers. Consequently, he suggests the "golden age" of USENIX ATC, characterized by deep dives into operating systems, filesystems, and networking, has likely passed.

Bryan Cantrill's blog post, "RIP Usenix ATC," delivers a heartfelt lament for the Usenix Annual Technical Conference (ATC), as he perceived it, arguing that the conference has irrevocably lost its distinctive character and essential value. He contends that ATC, once a vibrant hub of cutting-edge systems research and intimate collaboration among experts, has succumbed to the pressures of growth and mainstream appeal, transforming into a diluted, less technically rigorous event. He portrays the earlier iterations of ATC as a haven for deeply technical discussions, characterized by a strong sense of community and shared intellectual curiosity. This atmosphere fostered open dialogue and the free exchange of ideas, often leading to significant advancements in the field. The smaller scale and focused audience, according to Cantrill, enabled a level of engagement and interaction that is now absent.

He posits that the conference's expansion, while potentially beneficial in terms of broader reach, has come at the cost of this unique intimacy and technical depth. The increased number of attendees, he argues, has created a more impersonal and less focused environment, hindering the kind of in-depth conversations and spontaneous collaborations that once defined the ATC experience. He also expresses concern about a perceived shift in the conference's focus, suggesting that it has drifted away from its core strength in systems research towards more general computer science topics, further diluting its specialized identity. This shift, in his view, reflects a broader trend of homogenization within the technical conference landscape, where specialized events lose their distinct character in pursuit of a wider audience and broader appeal.

Cantrill uses specific examples, like the evolution of the conference's Birds-of-a-Feather (BoF) sessions, to illustrate this decline. He describes how these informal gatherings, once a cornerstone of ATC's collaborative spirit, have become increasingly structured and less spontaneous, diminishing their value as platforms for organic discussion. He also laments the perceived decline in the quality of presentations and the increasing presence of corporate influence, further contributing to the sense of loss he expresses. The post concludes with a tone of resignation, suggesting that the ATC he knew and valued is gone, perhaps irrevocably, replaced by a larger, more generic conference that, while potentially successful on other metrics, no longer serves the specific needs and interests of the systems research community he represents. He implies a sense of mourning for this loss, using the "RIP" in the title to emphasize the finality of this transformation.

Summary of Comments ( 1 )
https://news.ycombinator.com/item?id=43964827

Commenters on Hacker News largely echoed Bryan Cantrill's sentiments about the decline of Usenix ATC, lamenting the loss of its unique character and technical depth. Several attributed this shift to the increasing influence of corporate interests and the rise of "sanitized" presentations focused on product pitches rather than groundbreaking research. Some argued that the conference's prestige had waned, with top researchers opting for venues perceived as more impactful. A few commenters suggested potential remedies, such as stricter review processes prioritizing novel research and limiting corporate influence, but overall, the prevailing tone was one of nostalgia for a bygone era of more rigorous and academically focused technical conferences. The shift towards more general conferences was also mentioned, alongside the proliferation of specialized conferences that may now be better suited for specific research areas.

The Hacker News post titled "RIP Usenix ATC" discussing Bryan Cantrill's blog post about the declining relevance of the Usenix Annual Technical Conference generated a fair amount of discussion, with several commenters sharing their perspectives and experiences.

A significant thread emerged around the changing nature of academic conferences in general. One commenter lamented the corporatization of conferences, suggesting that the focus has shifted from pure technical exchange to networking and recruitment, diluting the original purpose. They pointed to the increased presence of corporate sponsors and recruiting booths as evidence of this shift. Another commenter echoed this sentiment, highlighting the perceived decline in the quality of presentations, attributing it to a pressure to publish for career advancement rather than genuine contribution to the field.

Several commenters discussed the specific changes within Usenix ATC that may have contributed to its decline. One posited that the rise of specialized conferences and workshops, offering more focused discussions within specific niches, has drawn attention away from broader conferences like Usenix ATC. The increasing availability of preprints and online publications was also mentioned as a factor, allowing researchers to disseminate their work more quickly and broadly, potentially reducing the incentive to present at conferences.

Another commenter offered a different perspective, arguing that the perception of decline might be a result of the natural evolution of the field. They suggested that as technologies mature and become more established, the nature of innovation and research changes, leading to a shift in the types of presentations and discussions at conferences.

Some commenters expressed nostalgia for the "golden age" of Usenix ATC, recalling it as a vibrant hub for cutting-edge research and stimulating discussions. They reminisced about the close-knit community and the opportunities for in-depth technical exchange.

The discussion also touched upon the role of online platforms and communities in disseminating technical knowledge. One commenter suggested that online forums and platforms like Hacker News itself have become valuable alternatives to traditional conferences, providing a more accessible and dynamic space for technical discussion.

Finally, there was some debate about the future of technical conferences. Some commenters expressed pessimism about the ability of traditional conferences to adapt to the changing landscape, while others argued that conferences still hold value, particularly for networking and building connections within the community. The possibility of hybrid or online conference formats was also mentioned as a potential avenue for evolution.

Why not object capability languages?

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Posted: 2025-05-11 18:57:07

The blog post argues against the widespread adoption of capability-based programming languages, despite acknowledging their security benefits. The author contends that capabilities, while effective at controlling access to objects, introduce significant complexity in reasoning about program behavior and resource management. This complexity arises from the need to track and distribute capabilities carefully, leading to challenges in areas like error handling, memory management, and debugging. Ultimately, the author believes that the added complexity outweighs the security advantages in most common programming scenarios, making capability languages less practical than alternative security approaches.

The blog post "Why not object capability languages?" by Drew DeVault explores the reasons why object capability languages, despite their theoretical advantages in security and modularity, haven't achieved widespread adoption. The author begins by acknowledging the compelling security model offered by capability-based systems. They operate on the principle of least privilege, granting programs access only to the specific resources they need to function, thereby limiting the potential damage from bugs or malicious code. This is achieved by using capabilities as unforgeable tokens of authority, rather than relying on ambient authority like traditional access control lists (ACLs). He specifically cites the robust security guarantees this provides against confused deputy problems.

However, DeVault argues that the practical implementation of capability security introduces complexities that hinder broader adoption. One major hurdle is the inherent difficulty in composing capability-secure libraries. Unlike traditional systems where libraries can freely utilize any globally available function, in a capability-based system, each library must explicitly receive the necessary capabilities to perform its operations. This can lead to verbose and cumbersome API designs, where capabilities have to be meticulously propagated throughout the call stack. The author illustrates this with an example involving a logging library, demonstrating how the requirement to explicitly pass capabilities can quickly become unwieldy.

The article goes on to discuss the performance implications of capability-based security. While not inherently slow, capability systems often introduce overhead related to capability checking and management. Furthermore, the author contends that capability-based programming can lead to less efficient data structures and algorithms, as developers must navigate the constraints imposed by capability-based access control.

Another point of concern raised by the author is the lack of mature tooling and ecosystem surrounding capability languages. Debugging, profiling, and other development tasks can be more challenging in capability-based environments due to the restricted access patterns. This, combined with the relative scarcity of libraries and frameworks tailored for capability security, makes it less attractive for mainstream developers.

Finally, DeVault addresses the argument that capability security is inherently more complex for programmers. He concedes that the initial learning curve might be steeper, but argues that this complexity arises from addressing a real and significant security problem. He suggests that the long-term benefits of improved security and modularity outweigh the initial investment in understanding capability-based programming. However, he acknowledges that this perceived complexity, combined with the other practical challenges discussed, contributes to the limited adoption of capability languages. In essence, the author presents a nuanced perspective on the trade-offs inherent in capability-based security, acknowledging its strengths while frankly outlining the practical obstacles that have prevented it from becoming the dominant paradigm.

Summary of Comments ( 55 )
https://news.ycombinator.com/item?id=43956095

Hacker News users discuss capability-based security, focusing on its practical limitations. Several commenters point to the difficulty of auditing capabilities and the lack of tooling compared to established access control methods like ACLs. The complexity of reasoning about capability propagation and revocation in large systems is also highlighted, contrasting the relative simplicity of ACLs. Some users question the performance implications, specifically regarding the overhead of capability checks. While acknowledging the theoretical benefits of capability security, the prevailing sentiment centers around the perceived impracticality for widespread adoption given current tooling and understanding. Several commenters also suggest that the cognitive overhead required to develop and maintain capability-secure systems might be too high for most developers. The lack of real-world, large-scale success stories using capabilities contributes to the skepticism.

The Hacker News post "Why not object capability languages?" with ID 43956095 has generated several comments discussing various aspects of capability-based security and its practical implications.

Several commenters delve into the complexities of implementing and adopting capability-based systems. One commenter highlights the difficulty of retrofitting capabilities into existing systems, suggesting that a complete rewrite is often necessary. They also point out the learning curve associated with capability-based programming, which can be steep for developers accustomed to traditional access control models. Another commenter emphasizes the scarcity of tools and libraries designed for capability systems, making development more challenging compared to established environments. The challenges of debugging capability-based systems are also mentioned, with a commenter noting the difficulty of tracing authority and identifying the source of errors.

The performance implications of capabilities are also a topic of discussion. One commenter mentions the potential overhead associated with capability checks, especially in performance-sensitive applications. Another commenter counters this argument by suggesting that the fine-grained control offered by capabilities can actually improve performance by reducing unnecessary access checks. However, they acknowledge the need for careful design and implementation to avoid performance bottlenecks.

Some commenters explore alternative approaches to security, such as using type systems for access control. One commenter argues that type systems can provide similar benefits to capabilities while being more familiar to developers. Others point out that type systems and capability-based security are not mutually exclusive and can be used in conjunction to enhance overall system security.

The discussion also touches upon the social and economic factors influencing the adoption of capability systems. One commenter suggests that the lack of widespread adoption stems from the network effects of existing systems, making it difficult for new paradigms to gain traction. They also note the inertia within organizations, where switching to a new security model can be disruptive and costly. The discussion also delves into the challenges of explaining the benefits of capabilities to non-technical stakeholders, highlighting the need for better communication and advocacy within the broader software community.

Several commenters express support for the potential of capability-based security, while acknowledging the practical hurdles that need to be overcome. They emphasize the need for more research, development, and education to make capability systems more accessible and practical for mainstream adoption. One commenter suggests that focusing on specific use cases and demonstrating tangible benefits could help drive adoption.

Finally, there's a brief discussion about specific capability-based languages and systems, with mentions of Pony and Joe-E as examples of promising approaches. These comments provide pointers for readers interested in exploring existing implementations of capability-based security.

Ash (Almquist Shell) Variants

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Posted: 2025-05-10 08:01:30

The Almquist shell (ash) has spawned numerous variants over the years, each with its own focus and features. These range from minimal, resource-constrained versions like BusyBox ash, suitable for embedded systems, to enhanced shells like ksh, dash, and zsh that prioritize performance, portability, or extended functionality. The post provides a comprehensive list of these ash derivatives, briefly describing their key characteristics and intended use cases, along with links to their respective projects. This serves as a valuable resource for understanding the ash lineage and selecting the appropriate shell for a given environment.

This webpage, titled "Ash (Almquist Shell) Variants," provides a comprehensive overview of various forks, derivatives, and implementations of the Almquist Shell (ash), a lightweight and portable Unix shell known for its speed and small footprint. The author meticulously catalogs a diverse range of ash-based shells, emphasizing their individual characteristics and historical context.

The core of the document is a structured list, categorizing the different ash variants. This categorization includes "Direct ash derivatives," comprising shells like the original ash itself, maintained by Kenneth Almquist, as well as prominent forks such as BusyBox ash, the default shell in many embedded systems. Another category, "Shells based on ash," encompasses projects like dash (Debian Almquist shell), which serves as the /bin/sh in Debian and Ubuntu systems, and other shells that borrowed heavily from ash's design but have since diverged significantly. Furthermore, the document identifies "Shells inspired by ash," acknowledging shells that share philosophical similarities or design principles with ash, even if their codebases are not directly related. Finally, there's a category for "Discontinued projects," documenting shells that were once based on or inspired by ash but are no longer actively maintained.

For each listed shell, the webpage offers a concise description, outlining its key features, target platforms, and its relationship to the original ash. It often includes links to the project's homepage, source code repository, or related documentation, facilitating further exploration for interested readers. The document also highlights the historical lineage of these shells, tracing their evolution and branching from one another, showcasing the influence of ash on the broader landscape of Unix shells. This detailed record provides valuable insights into the development and proliferation of ash-based shells within various operating systems and embedded environments, illustrating their importance in the Unix ecosystem.

The meticulous organization and extensive information provided on this page make it a valuable resource for anyone interested in understanding the history, diversity, and ongoing development of shells derived from the Almquist Shell. It serves as a central repository of knowledge for researchers, developers, and users alike who seek to navigate the complex world of ash and its numerous descendants.

Summary of Comments ( 2 )
https://news.ycombinator.com/item?id=43943984

HN users discuss various Ash-derived shells, primarily focusing on their size and suitability for embedded systems. Some highlight BusyBox's ash implementation as a popular choice due to its configurability, allowing developers to tailor its feature set and size. Others mention alternative shells like dash, praising its speed and adherence to POSIX standards, while acknowledging it lacks some features found in Bash. Several users express interest in smaller, more specialized shells, including ksh and hush, and discuss the trade-offs between size, features, and compliance. The thread also touches upon licensing considerations, static linking, and the practicality of using different shells for various tasks within a system.

The Hacker News post "Ash (Almquist Shell) Variants" sparked a discussion thread with several insightful comments. The conversation primarily revolves around the different ash-derived shells, their performance characteristics, and suitability for various use cases.

One commenter highlights the popularity of dash as the /bin/sh on Debian and its derivatives, emphasizing its role as a POSIX-compliant shell optimized for speed and small size. They further elaborate on the distinction between dash as a system shell and interactive shells like bash and zsh, which offer richer features for interactive use but come with a performance overhead. This distinction reinforces the rationale behind using a leaner shell like dash for system scripts where speed and resource efficiency are critical.

Another comment delves into the history of ash and its evolution, mentioning Kenneth Almquist's original creation and its subsequent adoption and modification in various projects like BSD and Debian. They explain that dash is essentially a maintained version of NetBSD's ash, indicating a lineage that ensures ongoing development and bug fixes. This historical context provides a deeper understanding of the relationships between the different ash variants.

Further discussion touches upon the resource consumption of shells, with one commenter observing that dash consumes considerably less memory compared to bash. This observation reinforces the argument for using dash in resource-constrained environments or for scripts where minimizing overhead is paramount.

The practical implications of shell choice are also discussed, with a comment suggesting that using dash can significantly speed up boot times and improve overall system responsiveness. This comment is particularly relevant for users seeking to optimize their system's performance.

A comment also explores the licensing aspects of different shells, mentioning the switch from the original Almquist Shell license to a BSD license. This provides relevant information for developers concerned about licensing compatibility.

The discussion also touches upon the trade-offs between functionality and performance, acknowledging that while bash offers a wider range of features, dash excels in speed and efficiency. This highlights the importance of choosing the right shell based on the specific requirements of the task at hand.

Finally, a commenter shares personal experiences with dash, highlighting its value in situations where strict POSIX compliance is necessary. This anecdote further emphasizes the practical benefits of using dash in certain contexts.

Overall, the comments provide valuable insights into the history, features, and trade-offs of the various ash-derived shells, offering practical advice for choosing the right tool for different use cases.

Usenix ATC Announcement

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Posted: 2025-05-09 03:18:03

USENIX has announced the cancellation of the in-person component of the 2024 ATC conference in Boston due to escalating costs, primarily venue and hotel expenses exceeding initial projections. While disappointed about this change, USENIX remains committed to holding a high-quality virtual conference experience during the original dates of July 17-19, 2024. Accepted papers will still be published in the conference proceedings, and authors will have the opportunity to present their work virtually. USENIX is exploring ways to potentially organize smaller, in-person gatherings focused on specific technical tracks during the same timeframe, but details are yet to be finalized. They are actively seeking alternative solutions for future ATCs and look forward to returning to a hybrid format in subsequent years.

The USENIX Association, a renowned non-profit organization dedicated to supporting and advancing advanced computing systems research, has announced significant changes to the structure and operation of their highly regarded Annual Technical Conference, commonly known as USENIX ATC. These alterations, set to take effect in 2025, aim to streamline the conference experience, enhance inclusivity, and broaden the scope of research presented while maintaining the conference's established prestige and rigorous standards.

Historically, USENIX ATC has functioned as an umbrella event, encompassing several co-located, specialized conferences covering diverse areas within systems research, such as file and storage technologies (FAST), operating systems design and implementation (OSDI), networked systems design and implementation (NSDI), and security symposia. This structure, while offering a rich and varied program, has led to logistical complexities and scheduling challenges for attendees wishing to participate in sessions across multiple sub-conferences. Furthermore, the distinct deadlines and review processes for each sub-conference have placed a substantial burden on both authors and the program committees.

To address these concerns, the USENIX Association has decided to consolidate all the previously co-located conferences under a single, unified USENIX ATC banner. This consolidation entails a harmonized review process with a single submission deadline and a unified program committee that will evaluate all submissions across the spectrum of systems research. This streamlined approach is anticipated to simplify the submission process for authors, allowing them to target their work to the most appropriate audience within the broader ATC scope without needing to navigate multiple conference-specific requirements. Moreover, the unified program will facilitate cross-disciplinary interaction and collaboration among attendees, fostering a more cohesive and integrated conference experience.

This transition, while significant, will not compromise the high standards of technical rigor and peer review that have long been the hallmark of USENIX ATC and its constituent conferences. The unified program committee will be composed of leading experts across all areas of systems research, ensuring that each submission receives thorough and expert evaluation. The USENIX Association emphasizes its commitment to maintaining the quality and reputation of the conference while striving to create a more inclusive, accessible, and integrated experience for all participants. The goal is to further strengthen USENIX ATC’s position as a premier venue for disseminating cutting-edge research in advanced computing systems. The changes are scheduled for implementation in 2025, providing ample time for the community to adapt to the new structure and contribute to shaping the future of USENIX ATC.

Summary of Comments ( 8 )
https://news.ycombinator.com/item?id=43933511

The Hacker News comments express disappointment and frustration with USENIX's decision to hold their Advanced Technical Conference (ATC) in Boston, citing high costs, difficult visa processes for international attendees, and Massachusetts' generally unfriendly political climate (particularly regarding abortion access). Some commenters suggest alternative, more accessible locations and question the conference organizers' rationale. Several point out the hypocrisy of USENIX's stated commitment to diversity and inclusion while choosing a location that presents barriers for many. There's a sense of betrayal among long-time attendees, with some vowing to boycott the event. A few commenters offer counterpoints, mentioning Boston's strong technical scene and suggesting that USENIX might have negotiated favorable rates. However, these comments are largely overshadowed by the negative sentiment.

The Hacker News post titled "Usenix ATC Announcement" (linking to a blog post about the USENIX Annual Technical Conference) has a modest number of comments, sparking a brief discussion around the conference and USENIX in general. No single comment stands out as overwhelmingly compelling, but a few recurring themes and noteworthy points emerge.

Several comments focus on the high cost of USENIX conferences. One user laments the expense, particularly for students and those from developing countries, suggesting it creates a barrier to entry. Another concurs, pointing out the high cost of membership and wondering if it's truly worthwhile. This concern about inclusivity and accessibility underscores a potential issue with the conference's pricing model.

Another thread discusses the quality and relevance of USENIX conferences, specifically ATC. One commenter notes the conference's historical prestige and influence within the systems research community, but expresses some uncertainty about its current standing. They question whether ATC remains a top-tier venue for cutting-edge systems research or if its importance has diminished. Another comment emphasizes the conference's consistently high-quality program and the valuable networking opportunities it provides. This exchange reflects a nuanced perspective on the conference's ongoing role in the field.

A couple of comments mention the unique culture and atmosphere of USENIX events. One user praises the "single track" format, highlighting the benefit of having all attendees focused on the same presentations, fostering a sense of shared experience and deeper engagement. Another commenter appreciates the community's emphasis on rigorous technical discussions and in-depth analysis. These comments shed light on the aspects that distinguish USENIX conferences from other technical gatherings.

Finally, one commenter raises a practical point about the location of the conference (Boston), noting the city's high hotel costs and suggesting attendees book accommodations early. This provides a helpful tip for anyone considering attending.

In summary, the comments on the Hacker News post offer a mixed bag of perspectives on the USENIX ATC announcement. While some express concerns about the conference's cost and relevance, others affirm its value, highlighting its historical significance, strong technical program, and unique community atmosphere. The discussion, while not extensive, provides a glimpse into the varied opinions within the tech community regarding USENIX and its conferences.

Memory-safe sudo to become the default in Ubuntu

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Posted: 2025-05-06 11:22:55

Ubuntu is switching its default sudo implementation to a memory-safe version written in Rust. This change, starting with Ubuntu 23.10 "Mantic Minotaur", significantly improves security by mitigating vulnerabilities related to memory corruption, such as buffer overflows and use-after-free bugs, which are common targets for exploits. This Rust-based sudo is developed and maintained by the OpenSSF's Secure Software Supply Chain project, and represents a major step towards a more secure foundation for the widely-used system administration tool.

The Trifacta Tech blog post "Memory-safe sudo to become the default in Ubuntu" details the upcoming transition in Ubuntu to a memory-safe version of sudo, the ubiquitous command-line utility that allows users to execute commands with elevated privileges. This change, a significant step towards enhancing system security, is being implemented by switching the default sudo implementation from the traditional C version to a rewritten version leveraging Rust, a modern programming language renowned for its memory safety guarantees.

The blog post highlights the inherent vulnerability of C code to memory-related bugs, such as buffer overflows and use-after-free errors. These vulnerabilities can be exploited by malicious actors to gain unauthorized access to a system, potentially escalating privileges and compromising security. Rust's ownership and borrowing system, along with its strict compile-time checks, effectively prevents these types of memory-related vulnerabilities, making it a compelling choice for security-sensitive applications like sudo.

Ubuntu's adoption of the Rust-based sudo is part of a broader industry trend towards embracing memory-safe languages for system programming. This movement is driven by the increasing awareness of the prevalence and severity of memory-related vulnerabilities in C and C++ codebases. By switching to Rust, Ubuntu aims to significantly reduce the attack surface of sudo and enhance the overall security posture of its systems.

The post explains that the transition will be gradual and transparent to most users. The new Rust-based sudo will be installed alongside the existing C version initially, and users will be able to choose which version to use. Eventually, the Rust version will become the default, providing enhanced security by default for all Ubuntu users. This phased approach allows for thorough testing and ensures compatibility with existing systems and workflows.

The blog post emphasizes the importance of this change in the context of modern security threats, where exploiting memory-related vulnerabilities remains a common attack vector. By adopting a memory-safe implementation of sudo, Ubuntu is taking a proactive step towards mitigating these risks and bolstering the security of its users. The post concludes by highlighting the potential for this transition to serve as a catalyst for wider adoption of memory-safe languages in critical system software.

Summary of Comments ( 69 )
https://news.ycombinator.com/item?id=43903853

Hacker News commenters generally expressed approval for Ubuntu's move to a memory-safe sudo, viewing it as a positive step towards improved security. Some questioned the significance of the change, pointing out that sudo itself isn't a frequent source of vulnerabilities and suggesting that efforts might be better directed elsewhere. A few expressed concerns about potential performance impacts, while others highlighted the importance of addressing memory safety issues in widely used system utilities like sudo to mitigate even rare but potentially impactful vulnerabilities. The discussion also touched upon the broader trend of adopting Rust for system programming and the trade-offs between memory safety and performance. Several commenters shared anecdotes about past vulnerabilities related to sudo and other core utilities, reinforcing the argument for enhanced security measures.

The Hacker News post "Memory-safe sudo to become the default in Ubuntu" generated several comments discussing the implications of switching to a memory-safe version of sudo.

Several commenters expressed strong approval for the move, emphasizing the importance of memory safety in a critical utility like sudo. They highlighted how sudo's privileged position makes it a prime target for exploitation, and how memory safety mitigations can significantly reduce the risk of successful attacks. One commenter specifically mentioned how this change aligns with a broader industry trend towards prioritizing memory safety.

Some discussion revolved around the choice of Rust as the language for the rewritten sudo. While generally praised for its memory safety features, a few commenters raised concerns about the potential performance overhead and the learning curve for developers accustomed to C. One commenter pointed out that the performance impact is likely negligible for a tool like sudo, which isn't typically performance-critical. Another countered that while Rust's performance is often comparable to C, achieving optimal performance in Rust can require more effort.

A few comments delved into the technical details of the rewrite, including the challenges of integrating Rust code with existing C codebases. One commenter mentioned the use of bindgen to create safe bindings, acknowledging the complexities involved in such integrations.

Several commenters expressed hope that other distributions would follow Ubuntu's lead in adopting a memory-safe sudo. The discussion also touched upon the wider adoption of memory-safe languages in system programming, with some suggesting that this move by Ubuntu could signal a significant shift in the industry.

A couple of comments inquired about the timeline for the transition and the testing procedures in place to ensure a smooth rollout. There was also a brief discussion about the potential impact on existing scripts and configurations, with one commenter suggesting that the changes are unlikely to cause significant disruption.

Overall, the comments reflect a generally positive reception to the news, with many commenters acknowledging the importance of memory safety in system utilities and praising Ubuntu for taking the lead in this area. While some concerns were raised regarding performance and the learning curve associated with Rust, the overall sentiment leaned towards the long-term benefits of increased security.

Why Flatpak Apps Use So Much Disk Space on Linux

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Posted: 2025-05-04 14:57:59

Flatpaks consume significant disk space because they bundle all their dependencies, including libraries and runtimes, within each application. This avoids dependency conflicts but leads to redundancy, especially when multiple Flatpaks share common libraries. While deduplication efforts exist at the file system level with OSTree, and some shared runtimes are used, many applications still ship with their own unique copies of common dependencies. This "bundling everything" approach, while beneficial for consistent performance and cross-distribution compatibility, contributes to the larger storage footprint compared to traditional package managers that leverage shared system libraries. Furthermore, Flatpak stores multiple versions of the same application for rollback functionality, further increasing disk usage.

The article "Why Flatpak Apps Use So Much Disk Space on Linux" on OSTechnix explores the reasons behind the seemingly large disk space consumption of Flatpak applications compared to traditional Linux packages. It begins by acknowledging the user perception of Flatpak's disk usage, explaining that while a Flatpak application might appear to be significantly larger than its traditional counterpart, the reality is more nuanced.

The core of Flatpak's disk usage lies in its fundamental design principle: application isolation. Unlike traditional packages that often share libraries and dependencies system-wide, Flatpaks bundle almost everything an application needs to run within its own self-contained environment. This includes libraries, runtimes, and other dependencies, leading to a larger initial download and installation size. The article explains that while this approach appears redundant – having multiple copies of the same library on the system – it provides key benefits like enhanced security and stability by preventing conflicts between applications and the host system, and ensuring consistent execution across different Linux distributions.

The article then delves into the concept of runtimes, which are pre-built sets of common libraries bundled together. Applications built for the same runtime can share these libraries, thus minimizing redundancy and reducing overall disk space usage. This mechanism is analogous to a foundation upon which multiple applications can be built. While the initial download of a runtime can be substantial, subsequent applications utilizing that same runtime only need to download the application-specific components, minimizing the incremental disk space impact.

The concept of deduplication is also explained, highlighting that while multiple applications may install the same runtime or libraries, the underlying file system often employs mechanisms to avoid storing multiple physical copies of these identical files. Instead, hard links or similar techniques are used to point multiple applications to the same physical data blocks on the disk, significantly reducing the actual disk space consumed.

Furthermore, the article contrasts Flatpak's approach with traditional package managers, which often scatter dependencies across the file system. It argues that while Flatpak's self-contained bundles appear large, they actually offer a more organized and manageable approach to dependencies, simplifying updates and removal. With Flatpak, uninstalling an application removes all its associated files completely, leaving no orphaned dependencies behind, unlike traditional package management where leftover dependencies can accumulate over time.

Finally, the article touches on the trade-off between disk space and the benefits offered by Flatpaks. While acknowledging the larger initial download size, it emphasizes the advantages of isolation, security, cross-distribution compatibility, and cleaner application management, concluding that the extra disk space usage is often a reasonable price to pay for these benefits in the modern Linux ecosystem.

Summary of Comments ( 1 )
https://news.ycombinator.com/item?id=43887073

HN commenters generally agree that Flatpak's disk space usage is a valid concern, especially for users with limited storage. Several point out that the deduplication system, while theoretically efficient, doesn't always work as intended, leading to redundant libraries and inflated app sizes. Some suggest that the benefits of Flatpak, like sandboxing and consistent runtime environments, outweigh the storage costs, particularly for less experienced users. Others argue that alternative packaging formats like .deb or .rpm are more space-efficient and sufficient for most use cases. A few commenters mention potential solutions, such as improved deduplication or allowing users to share runtimes across different distributions, but acknowledge the complexity of implementing these changes. The lack of clear communication about Flatpak's disk usage and the absence of easy tools to manage it are also criticized.

The Hacker News post "Why Flatpak Apps Use So Much Disk Space on Linux" generated a robust discussion with several compelling comments. Many users chimed in with their perspectives and experiences regarding Flatpak disk usage.

A significant number of commenters agreed with the article's premise, noting the often-redundant nature of runtime dependencies leading to wasted space. Some users shared anecdotes of surprisingly large disk space consumption by seemingly small applications. The observation about separate runtimes for even minor version differences between dependencies was a recurring theme, with many echoing the frustration of having multiple copies of essentially the same libraries.

Several commenters delved into the tradeoffs inherent in Flatpak's design. While acknowledging the disk space issue, they highlighted the benefits of application isolation and predictable execution environments provided by Flatpak. The discussion touched upon the advantages of this approach for software distribution and maintenance, especially regarding dependency management and avoiding conflicts. Some argued that the disk space tradeoff is acceptable in exchange for the stability and ease of use Flatpak offers.

Some users offered potential solutions and mitigating factors. The potential for deduplication of runtime files was mentioned, as was the relatively low cost of storage these days. Others suggested that the issue might be less pronounced with more widespread adoption of Flatpak, as more applications would share common runtimes.

A few commenters compared Flatpak to other packaging formats like Snaps, drawing parallels and highlighting differences in their approaches to dependency management and disk usage. The relative merits and drawbacks of each system were debated, with no clear consensus emerging.

A smaller subset of the comments questioned the article's methodology or argued that the issue was exaggerated. They pointed out that the disk space used by runtimes is often shared between multiple applications, mitigating the overall impact. Others suggested that the article focused on extreme cases and didn't represent typical Flatpak usage.

VMOS – Virtual Android on Android

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Posted: 2025-05-03 04:08:22

VMOS is an app that lets you run a virtual Android instance on your Android device. This creates a separate, isolated environment where you can install and run apps, including rooted apps, and modify system settings without affecting your main operating system. It's marketed towards users who want to run multiple accounts of the same app, test potentially risky apps in a safe sandbox, or experiment with different Android versions and customizations. VMOS Pro, a paid version, offers enhanced features like floating windows and improved performance.

VMOS presents itself as a revolutionary application that empowers users to run a fully functional virtual Android operating system on their existing Android device. This effectively creates a "phone within a phone" scenario, offering a separate and isolated Android environment independent of the host device's operating system. This virtual environment operates as a complete Android instance, capable of running apps, games, and accessing the internet, all within its own contained space.

VMOS highlights its root access capability as a key feature. This provides users with extensive control over the virtual Android system, enabling advanced customization and experimentation. This level of access is particularly attractive to developers, security researchers, and power users who require deep system manipulation.

The application's website emphasizes the benefits of using a virtual Android environment. It suggests using VMOS for running multiple accounts of the same app simultaneously, a useful feature for those managing multiple social media profiles or gaming accounts. It also promotes the security aspects of isolating potentially risky apps within the virtual machine, shielding the host device from potential malware or privacy breaches. Furthermore, VMOS suggests its utility in testing applications in a safe, sandboxed environment before installing them on the primary operating system.

The site further emphasizes the seamless user experience provided by VMOS, claiming a "smooth and lag-free" performance. It also highlights the platform's compatibility with a wide range of Android devices and versions, ensuring accessibility for a broad user base. The virtual machine is portrayed as highly customizable, allowing users to adjust parameters such as resolution, CPU cores, and RAM allocated to the virtual device for optimal performance based on their device's capabilities. This tailor-made experience is meant to ensure a smooth and responsive virtual environment.

Finally, VMOS promotes its use as a tool for developers, specifically for debugging and testing applications in different Android environments. It also pitches itself as a convenient platform for running older Android versions for compatibility testing or accessing legacy applications. This positions VMOS not just as a tool for casual users, but also as a valuable resource for developers and technical users.

Summary of Comments ( 15 )
https://news.ycombinator.com/item?id=43876798

HN users express skepticism and concern about VMOS. Several commenters point to its closed-source nature and potential security risks, particularly regarding data collection and privacy. Some suspect it might be malware or spyware given its request for extensive permissions and the lack of transparency about its inner workings. Others mention the performance limitations inherent in running a virtual machine on a mobile device and question its practical use cases. A few users suggest alternative solutions like Genymotion or running a dedicated Android emulator on a desktop. The overall sentiment is cautious, with a strong recommendation to avoid VMOS unless one understands the potential implications and risks.

The Hacker News post "VMOS – Virtual Android on Android" discussing the VMOS app generated a moderate number of comments, most of which expressed skepticism and concern about the security implications of running a virtual Android environment on a physical Android device.

Several commenters questioned the trustworthiness of the VMOS app itself, pointing out its closed-source nature and the potential for malicious activity. They highlighted the risk of the app accessing sensitive data on the host device, including personal information, financial details, and authentication credentials. Some users voiced concern about the lack of transparency regarding the app's permissions and data handling practices, making it difficult to assess the actual security risks.

The discussion also touched upon the potential performance impact of running a virtual machine on a mobile device. Commenters speculated about the drain on battery life, processing power, and storage space, suggesting that the performance overhead might outweigh the benefits for many users.

Some commenters mentioned alternative solutions for achieving similar functionality, such as using work profiles or dedicated apps for specific tasks. They argued that these alternatives might offer a better balance between functionality and security compared to a full-fledged virtual machine.

A few commenters shared their personal experiences with VMOS, reporting issues with stability and performance. These anecdotes further fueled the general skepticism surrounding the app's practicality and reliability.

While some users expressed interest in potential legitimate use cases, such as testing apps or isolating potentially risky software, the overall sentiment in the comments leaned heavily towards caution. The lack of trust stemming from the closed-source nature of the app and the potential security risks dominated the conversation. No commenters offered strong endorsements of VMOS, and the majority advised against using it, particularly for handling sensitive information.

Linux Kernel Exploitation: Attack of the Vsock

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Posted: 2025-04-30 19:03:04

The article details a vulnerability discovered in the Linux kernel's vsock implementation, a mechanism for communication between virtual machines and their hosts. Specifically, a use-after-free vulnerability existed due to improper handling of VM shutdown, allowing a malicious guest VM to trigger a double free and gain control of the host kernel. This was achieved by manipulating vsock's connection handling during the shutdown process, causing the kernel to access freed memory. The vulnerability was ultimately patched by ensuring proper cleanup of vsock connections during VM termination, preventing the double free condition and subsequent exploitation.

The article "Linux Kernel Exploitation: Attack of the Vsock" delves into a vulnerability discovery and exploit development process targeting the vsock interface within the Linux kernel. Vsock, designed for communication between a host operating system and its virtual machines, presented an attractive attack surface due to its relative obscurity and potential for privilege escalation. The author systematically breaks down their approach, starting with identifying a potential weakness.

The identified vulnerability lies within the VSOCK_OP_RW operation handler, specifically in how it manages memory allocation and access. When a guest VM requests a write operation larger than the pre-allocated buffer on the host, the kernel attempts to resize this buffer dynamically. However, a race condition exists. If the guest issues a new write request before the kernel finishes processing the previous one and before the buffer resize is complete, the kernel might use a stale buffer size, leading to a heap out-of-bounds (OOB) write. This vulnerability is further exacerbated by the fact that the guest has significant control over the size and timing of these write requests.

The author then details the intricate process of crafting an exploit to leverage this OOB write. This involved careful manipulation of heap metadata to achieve a controlled overwrite. The objective was not simply to crash the system but to gain arbitrary code execution within the kernel. This is achieved by meticulously manipulating heap structures, specifically the slub allocator, aiming to overwrite specific function pointers within kernel objects. The author discusses the challenges encountered during this process, including the intricacies of heap feng shui (arranging heap allocations in a predictable manner) and the need to bypass various kernel security mitigations, like KASLR (Kernel Address Space Layout Randomization) and SMAP (Supervisor Mode Access Prevention).

The exploitation strategy revolves around overwriting a function pointer within a tty struct, a kernel structure associated with terminals. By redirecting execution flow to a controlled location, the exploit gains control of the kernel. The article further explains the technique used to gain root privileges after successfully hijacking the kernel execution flow. This is done by overwriting a cred structure, which contains the user's security credentials, effectively promoting the attacker's process to root.

Finally, the article concludes by highlighting the potential impact of such a vulnerability, particularly in cloud environments where vsock is commonly used. It emphasizes the importance of responsible disclosure and the subsequent patching efforts that addressed the vulnerability. The author also provides a brief overview of the patch implemented in the Linux kernel, which introduced stricter bounds checking and improved synchronization to prevent the race condition and subsequent OOB write.

Summary of Comments ( 65 )
https://news.ycombinator.com/item?id=43849373

Hacker News users discussed the potential attack surface introduced by vsock, generally agreeing with the article's premise but questioning the practicality of exploiting it. Some commenters pointed out that the reliance on shared memory makes vsock vulnerable to manipulation by a compromised host, mitigating the isolation benefits it ostensibly provides. Others noted that while interesting, exploiting vsock likely wouldn't be the easiest or most effective attack vector in most scenarios. The discussion also touched on existing mitigations within the hypervisor and the fact that vsock is often disabled by default, further limiting its exploitability. Several users highlighted the obscurity of vsock, suggesting the real security risk lies in poorly understood and implemented features rather than the protocol itself. A few questioned the article's novelty, claiming these vulnerabilities were already well-known within security circles.

The Hacker News post titled "Linux Kernel Exploitation: Attack of the Vsock" (https://news.ycombinator.com/item?id=43849373) has generated several comments discussing the vulnerability and its implications.

Several commenters express concern about the potential impact of this vulnerability, particularly in cloud environments where vsock is commonly used for communication between virtual machines and their hosts. One commenter points out that exploiting this vulnerability could allow attackers to escape containers and gain access to the host system. Another echoes this, emphasizing the risk to cloud providers and the need for prompt patching.

Discussion also revolves around the technical details of the vulnerability. One commenter questions the specific nature of the vulnerability and asks for clarification on how the memory corruption occurs. Another delves into the complexities of exploiting such vulnerabilities, noting the challenges in achieving reliable exploitation due to factors like KASLR.

The use of vsock itself is a topic of conversation. One commenter mentions using virtio-serial as an alternative, highlighting its relative simplicity compared to vsock. Another discusses the performance benefits of vsock in certain scenarios, but acknowledges the security trade-offs that may come with it.

Some commenters discuss the broader implications for security in virtualized environments. The prevalence of vulnerabilities like this highlights the ongoing challenge of securing complex systems. One commenter expresses a general sense of unease about the complexity of modern systems and the potential for undiscovered vulnerabilities.

There is some discussion of the responsible disclosure process and the timeline for patching. One commenter asks about the availability of patches, while another expresses appreciation for the researcher's responsible disclosure.

Finally, a few commenters share links to related resources, such as the original vulnerability report and other articles discussing the topic. This provides further context and allows readers to delve deeper into the technical details.

Bare metal printf – C standard library without OS

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Posted: 2025-04-26 21:32:37

This blog post details how to implement a simplified printf function for bare-metal environments, specifically ARM Cortex-M microcontrollers, without relying on a full operating system. The author walks through creating a minimal version that supports basic format specifiers like %c, %s, %u, %x, and %d, bypassing the complexities of a standard C library. The implementation utilizes a UART for output and includes a custom integer to string conversion function. By directly manipulating registers and memory, the post demonstrates a lightweight printf suitable for resource-constrained embedded systems.

This blog post, titled "Bare metal printf – C standard library without OS," delves into the intricacies of implementing the standard C library function printf in a bare-metal environment, specifically targeting an ARM Cortex-M microcontroller. The author's primary goal is to understand how printf operates at a low level, without relying on an operating system's abstractions. This necessitates a deep dive into the inner workings of the function and the construction of the supporting infrastructure required for its proper execution.

The core challenge addressed is the lack of an operating system to handle system calls, particularly those related to input/output. In a typical OS environment, printf relies on the OS to write formatted output to a console or file. However, in a bare-metal setting, the programmer must directly interact with the hardware to achieve this. The post meticulously documents the process of crafting these low-level routines.

The implementation journey begins with understanding the variadic nature of printf, meaning it accepts a variable number of arguments. This characteristic necessitates parsing the format string to determine the types and number of arguments to be processed. The author carefully explains this parsing logic, which involves iterating through the format string and identifying format specifiers (like %d, %f, %s, etc.). These specifiers dictate how subsequent arguments are interpreted and formatted.

A critical aspect of this bare-metal printf implementation is handling floating-point numbers. The standard C library typically provides support for floating-point operations, but in a bare-metal environment, this must be implemented manually or linked in explicitly. The author details the decision-making process behind selecting a suitable floating-point library and integrating it into their solution.

The output of printf ultimately needs to be directed somewhere. The author chooses to target the microcontroller's UART peripheral, a common serial communication interface. This involves configuring the UART and implementing a low-level character output function that transmits individual characters over the serial connection. This function is then leveraged by the custom printf implementation to send the formatted output string to the UART.

The post doesn't merely present the final code but meticulously walks the reader through the development process, highlighting key decisions and their rationale. This includes discussing code organization, memory management considerations, and the challenges associated with working in a resource-constrained environment. The author provides code snippets demonstrating crucial parts of the implementation, such as parsing format strings and handling various data types. The ultimate result is a functional printf implementation that operates directly on the hardware without relying on an operating system, shedding light on the normally hidden complexities of this fundamental C function.

Summary of Comments ( 61 )
https://news.ycombinator.com/item?id=43807404

HN commenters largely praised the article for its clear explanation of implementing printf in a bare-metal environment. Several appreciated the author's focus on simplicity and avoiding unnecessary complexity. Some discussed the tradeoffs between code size and performance, with suggestions for further optimization. One commenter pointed out the potential issues with the implementation's handling of floating-point numbers, particularly in embedded systems where floating-point support might not be available. Others offered alternative approaches, including using smaller, more specialized printf implementations or relying on semihosting for debugging. The overall sentiment was positive, with many finding the article educational and well-written.

The Hacker News post titled "Bare metal printf – C standard library without OS," linking to an article on implementing printf without an operating system, has generated a modest number of comments discussing various aspects of the implementation and its implications.

Several commenters delve into the complexities and nuances of implementing core C library functions in bare-metal environments. One user highlights the surprising amount of work required to create a seemingly simple function like printf, especially when considering features like floating-point support and different format specifiers. They point out the significant effort involved in correctly handling all the edge cases and formatting rules defined by the C standard.

The discussion also touches upon the trade-offs between using a fully-featured printf and opting for a smaller, more specialized version tailored to the specific needs of a bare-metal project. A commenter suggests that in many embedded systems, a simpler output function might suffice, avoiding the overhead of a full printf implementation. They advocate for considering the specific requirements of the project and choosing the appropriate level of complexity.

Further discussion explores the challenges of handling string formatting and memory management in resource-constrained environments. One user questions the wisdom of dynamically allocating memory within printf in a bare-metal setting, suggesting potential issues if memory allocation fails. This raises the broader topic of robust error handling in such environments.

Another commenter notes the differences between the provided implementation and the behavior of glibc's printf. They specifically point out the article's implementation doesn't use the heap and bypasses the need for dynamic memory allocation. This highlights the flexibility and potential for customization when implementing these functions in a bare-metal context.

The comments also briefly touch upon the educational value of such projects, emphasizing the importance of understanding how fundamental library functions work at a low level. The process of implementing these functions from scratch can provide valuable insights into the inner workings of C and the complexities of bare-metal programming.

While not a highly active discussion thread, the comments provide valuable insights into the practical challenges and considerations involved in implementing standard C library functions in bare-metal environments, touching upon topics like memory management, code size, and error handling. They also highlight the potential trade-offs and the importance of tailoring the implementation to the specific needs of the project.

MinC Is Not Cygwin

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Posted: 2025-04-23 10:21:57

MinC is a compact, self-contained POSIX-compliant shell environment for Windows, distinct from Cygwin. It focuses on providing a minimal but functional core of essential Unix utilities, prioritizing speed, small size, and easy integration with native Windows programs. Unlike Cygwin, which aims for a comprehensive Unix-like layer, MinC eschews emulating a full environment, making it faster and lighter. It achieves this by leveraging existing Windows functionality where possible and relying on busybox for its core utilities. This approach makes MinC particularly suitable for tasks like scripting and automation within a Windows context, where a full-fledged Unix environment might be overkill.

The blog post, titled "MinC Is Not Cygwin," emphatically distinguishes the MinC project from Cygwin, another popular approach to bringing Unix-like utilities to Windows. The author, frustrated by perceived misconceptions, meticulously outlines the fundamental differences in philosophy and implementation between the two projects.

MinC, short for Minimalist GNU for Windows, prioritizes providing a lean, carefully curated selection of core GNU utilities compiled natively for Windows. This focus on minimalism results in a significantly smaller footprint and faster execution compared to Cygwin, which aims for a more comprehensive, POSIX-compliant environment. MinC explicitly avoids introducing a compatibility layer like Cygwin's DLL, which translates POSIX system calls to Windows API calls. Instead, MinC utilities are directly compiled against the standard Windows API, leading to improved performance and tighter integration with the native Windows ecosystem. The author highlights that this native compilation approach eliminates the runtime dependencies inherent in Cygwin, simplifying deployment and reducing the risk of conflicts with other software.

The post underscores that MinC is not intended to be a complete POSIX environment. It consciously omits features deemed unnecessary for its core purpose, contributing to its smaller size and enhanced performance. This selective inclusion of utilities is presented as a strength, allowing users to obtain only the specific tools they need without the overhead of a larger system. The post further emphasizes the importance of native compilation for achieving optimal performance, arguing that Cygwin's translation layer introduces an unavoidable performance penalty. This difference in approach is portrayed as a key differentiator between MinC and Cygwin, catering to users who prioritize speed and efficiency.

The post concludes by reiterating that MinC is tailored for users seeking a minimal, high-performance set of GNU utilities compiled natively for Windows, starkly contrasting with Cygwin's goal of providing a comprehensive POSIX-compatible environment. The author stresses that understanding this fundamental distinction is crucial for choosing the right tool for specific needs and avoiding unrealistic expectations.

Summary of Comments ( 121 )
https://news.ycombinator.com/item?id=43770445

Several Hacker News commenters discuss the differences between MinC and Cygwin, primarily focusing on MinC's smaller footprint and simpler approach. Some highlight MinC's benefit for embedded systems or minimal environments where a full Cygwin installation would be overkill. Others mention the licensing differences and the potential advantages of MinC's more permissive BSD license. A few commenters also express interest in the project and its potential applications, while one points out a typo in the original article. The overall sentiment leans towards appreciation for MinC's minimalist philosophy and its suitability for specific use cases.

The Hacker News post "MinC Is Not Cygwin" (https://news.ycombinator.com/item?id=43770445) discussing the MinC project (a minimalist Cygwin-like environment for Windows) has several comments exploring its purpose, benefits, and drawbacks compared to Cygwin and other similar solutions.

One commenter highlights MinC's value proposition: providing a smaller, simpler alternative to Cygwin, particularly for those needing only a limited set of Unix utilities on Windows. They acknowledge that Cygwin offers broader compatibility but emphasize that MinC caters to users who prioritize a lighter footprint and faster execution for specific tasks.

Another comment delves into the technical differences, pointing out that MinC uses native Windows executables where possible, unlike Cygwin, which relies on a compatibility layer. This approach reportedly contributes to MinC's performance advantage. However, the commenter also notes the limitations arising from this design, such as the challenges in handling fork() system calls, a fundamental aspect of Unix-like operating systems.

The discussion also touches upon alternative solutions like MSYS2 and Windows Subsystem for Linux (WSL). Commenters suggest that these options might offer a more robust and complete Unix-like environment, though potentially at the cost of increased complexity and resource usage. The original author of MinC joins the conversation, clarifying their motivation for creating the project: a dissatisfaction with the perceived "bloat" of Cygwin for their specific needs. They emphasize MinC's role as a highly specialized tool, acknowledging its unsuitability as a full Cygwin replacement.

The thread explores the implications of MinC's design choices, including its handling of file paths and its compatibility with native Windows programs. One commenter raises a potential concern about the maintainability of MinC due to its reliance on specific Windows versions and the possibility of future compatibility issues. Others appreciate the project's minimalist philosophy, viewing it as a practical solution for targeted tasks.

Overall, the comments offer a balanced perspective on MinC, acknowledging its strengths in providing a lightweight, performant alternative to Cygwin for limited use cases, while also recognizing its limitations and suggesting alternative solutions for users requiring a more comprehensive Unix-like environment on Windows.

Reworking 30 lines of Linux code could cut power use by up to 30 percent

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Posted: 2025-04-21 07:34:07

A tiny code change in the Linux kernel could significantly reduce data center energy consumption. Researchers identified an inefficiency in how the kernel manages network requests, causing servers to wake up unnecessarily and waste power. By adjusting just 30 lines of code related to the network's power-saving mode, they achieved power savings of up to 30% in specific workloads, particularly those involving idle periods interspersed with short bursts of activity. This improvement translates to substantial potential energy savings across the vast landscape of data centers.

The IEEE Spectrum article "Reworking 30 Lines of Linux Code Could Cut Power Use by Up to 30 Percent" discusses a potential energy-saving breakthrough within the Linux kernel, specifically targeting the energy consumption of data centers. Researchers from the University of California, San Diego, discovered inefficiencies in how the Linux kernel manages the transfer of data between a computer's memory and its storage drives – a process known as "writeback." Currently, the system prioritizes rapid data transfer, frequently flushing small amounts of data to the drives. While this approach maximizes performance, it comes at the expense of energy efficiency because the drives are frequently activated from their low-power idle state.

The researchers proposed a modification to the Linux kernel's writeback mechanism, involving a mere 30 lines of code. This alteration implements a more strategic approach to data transfer. Instead of continually flushing small amounts of data, the modified system allows data to accumulate before writing it to the storage drives. This consolidated writing process minimizes the number of times the drives are activated, allowing them to remain in their low-power state for longer durations.

Testing this revised code on several different workloads, including video streaming, web servers, and financial modeling, yielded promising results. The researchers observed a significant reduction in energy consumption, reaching up to 30% in certain scenarios. Importantly, these energy savings came without any noticeable performance degradation. In some cases, the revised code even slightly improved performance due to reduced overhead from constantly managing small write operations. This finding suggests that the existing performance-centric approach might not always be the most optimal strategy, even from a pure performance standpoint.

The article highlights the significant impact this seemingly minor code change could have on the global scale, considering the substantial energy footprint of data centers worldwide. By implementing this optimization, a considerable amount of energy could be saved, translating to reduced operational costs and a smaller environmental impact. The article concludes by noting the potential for broader application of this principle, suggesting similar optimizations could be explored in other operating systems and software to achieve further energy efficiency gains.

Summary of Comments ( 16 )
https://news.ycombinator.com/item?id=43749271

HN commenters are skeptical of the claimed 5-30% power savings from the Linux kernel change. Several point out that the benchmark used (SPECpower) is synthetic and doesn't reflect real-world workloads. Others argue that the power savings are likely much smaller in practice and question if the change is worth the potential performance trade-offs. Some suggest the actual savings are closer to 1%, particularly in I/O-bound workloads. There's also discussion about the complexities of power measurement and the difficulty of isolating the impact of a single kernel change. Finally, a few commenters express interest in seeing the patch applied to real-world data centers to validate the claims.

The Hacker News post, titled "Reworking 30 lines of Linux code could cut power use by up to 30 percent," linking to an IEEE Spectrum article about data center energy consumption, sparked a discussion with several insightful comments.

Many commenters focused on the specifics of the Linux kernel change mentioned in the title. Some expressed skepticism about the claimed 30% power savings, questioning the methodology used to arrive at that figure and pointing out that such a dramatic reduction likely applies only to very specific workloads or configurations. Others delved into the technical details of the code change, discussing the trade-offs involved and potential performance implications. There was a healthy dose of technical debate about how significant this change actually is and whether the headline accurately reflects the impact.

Several commenters broadened the discussion to the larger issue of data center energy consumption. They highlighted the importance of optimizing software for energy efficiency, not just relying on hardware improvements. Some pointed out that seemingly small code changes can have a significant cumulative impact when deployed across massive data centers. Others discussed the environmental impact of data centers and the need for greater sustainability efforts.

A few commenters mentioned related efforts to reduce energy consumption in other areas of computing, such as web browsers and mobile devices. This broadened the scope beyond just server-side Linux optimization.

Some questioned the practicality of applying these changes broadly, considering the potential for instability or unforeseen consequences in different system configurations. This brought a dose of realism to the discussion, reminding readers that potential gains need to be weighed against risks in complex systems.

Overall, the comments section reflects a mix of cautious optimism, technical scrutiny, and a broader awareness of the importance of energy efficiency in the computing world. Commenters engage with the specific code change mentioned in the headline while also connecting it to larger trends and concerns surrounding data center energy consumption. There's no outright dismissal of the proposed changes, but a healthy amount of critical analysis and questioning of the presented figures.

The Joy of Linux Theming in the Age of Bootable Containers

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Posted: 2025-04-20 13:56:06

The blog post explores the renewed excitement around Linux theming, enabled by the flexibility of bootable containers like Distrobox. Previously, trying different desktop environments or themes meant significant system upheaval. Now, users can easily spin up containerized instances of various desktops (GNOME, KDE, Sway, etc.) with different themes, icons, and configurations, all without affecting their main system. This allows for experimentation and personalization without risk, making it simpler to find the ideal aesthetic and workflow. The post walks through the process of setting up themed desktop environments within Distrobox, highlighting the ease and speed with which users can switch between dramatically different desktop experiences.

The blog post "The Joy of Linux Theming in the Age of Bootable Containers" by Drew DeVault explores the resurgence of desktop customization and theming within the Linux ecosystem, specifically highlighting how containerization technologies like Distrobox have simplified the process and expanded its possibilities. DeVault argues that while the "golden age" of Linux theming, characterized by extensive customization options and vibrant communities, waned due to factors like the standardization brought about by GNOME 3 and KDE Plasma 5, as well as the shift towards web technologies and cross-platform compatibility, a new era of theming is dawning, facilitated by containerized systems.

The author explains how tools like Distrobox allow users to run virtually any Linux distribution within a container on their main system, effectively granting them access to the distinct theming capabilities and desktop environments of those distributions without requiring a full system reinstall or dual-booting. This offers a significant advantage for users who desire a highly personalized desktop experience, enabling them to experiment with different themes, window managers, and even entire desktop environments without compromising the stability or configuration of their primary system. DeVault emphasizes the ease with which users can switch between these containerized environments, making it trivial to test and utilize various themes optimized for specific desktop environments.

The post further details DeVault's personal journey in exploring this renewed approach to theming. He describes setting up a dedicated container for running older versions of Enlightenment, a window manager known for its extensive theming capabilities, and another container for a customized Sway setup. This demonstrates the practical application of containerization for reviving and enjoying older desktop environments and their associated themes without the complexities of managing dependencies and compatibility issues on the host system. He highlights the benefit of isolating these environments, allowing him to fully embrace the unique aesthetics and functionalities of each without interference.

Furthermore, DeVault touches upon the modularity this approach introduces, suggesting that users can leverage containers to separate specific applications with particular theming requirements from their primary desktop environment. He illustrates this with an example of running a game within a container configured with appropriate libraries and visual settings, emphasizing the granular control this provides over the user experience.

Finally, the post celebrates the renewed enthusiasm for theming, attributing it to the convenience and flexibility offered by containerization. DeVault concludes by encouraging readers to rediscover the joy of customizing their Linux desktops, empowered by the tools and technologies now readily available. He portrays this containerized approach as not just a technical solution, but a catalyst for creativity and personalization within the Linux desktop landscape, ushering in a new era of accessible and powerful theming possibilities.

Summary of Comments ( 69 )
https://news.ycombinator.com/item?id=43743784

Hacker News users discussed the practicality and appeal of extensively theming Linux, particularly within containers. Some found the author's pursuit of highly customized aesthetics appealing, appreciating the control and personal expression it offered. Others questioned the time investment versus the benefit, especially given the ephemeral nature of containers. The discussion also touched on the balance between aesthetics and functionality, with some arguing that excessive theming could hinder usability. A few commenters shared their own theming experiences and tools, while others expressed a preference for minimal, distraction-free environments. The idea of containers as disposable environments clashed with the effort involved in detailed theming for some, prompting discussion on whether this approach was sustainable or efficient.

The Hacker News post "The Joy of Linux Theming in the Age of Bootable Containers" generated a moderate discussion with several interesting points raised in the comments section.

Several commenters discussed the benefits and drawbacks of using containers for theming, particularly in comparison to traditional methods. One user pointed out the advantage of containerized theming for easy experimentation and switching between different themes without affecting the base system. They also highlighted the potential for using pre-built, themed container images, simplifying the process for less technical users. However, another commenter countered this by mentioning the increased complexity and resource overhead that can come with containerization, especially for users unfamiliar with container technologies. This led to a small thread discussing the practicality of containers for simple theming tasks, with some arguing that the added complexity might outweigh the benefits for many users.

The discussion also touched upon the broader topic of Linux desktop customization and the challenges involved. One commenter expressed nostalgia for the days of easier theming and customization in older desktop environments, lamenting the increasing complexity and fragmentation in modern Linux desktops. Another user brought up the issue of maintaining consistent theming across different applications and desktop environments, suggesting that containerization could potentially offer a solution to this problem.

Some comments focused on the specific tools and techniques mentioned in the linked article, with users sharing their own experiences and preferences. One commenter mentioned their preferred method of theming using configuration files and scripts, while another expressed interest in exploring the container-based approach described in the article.

Finally, a few comments drifted slightly off-topic, discussing related subjects such as the overall state of Linux desktop usability and the challenges of attracting new users. One commenter argued that the focus on advanced features and customization often comes at the expense of user-friendliness, potentially alienating less technical users.

In summary, the comments section offers a diverse range of perspectives on the topic of Linux theming, with particular emphasis on the potential benefits and drawbacks of using containers. The discussion also touches upon broader issues related to Linux desktop customization and usability.

Let's give PRO/VENIX a barely adequate, pre-C89 TCP/IP stack, featuring Slirp-CK

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Posted: 2025-04-20 06:07:57

The blog post details the integration of a limited, pre-C89 compliant TCP/IP stack into the PRO/VENIX operating system using Slirp-CK, a small footprint networking library. This allows PRO/VENIX, a vintage Unix-like system, to connect to modern networks for tasks like downloading files. The implementation focuses on simplicity and compatibility with the system's older C compiler, intentionally avoiding more complex and modern networking features. While functional, the author acknowledges its limitations and describes it as "barely adequate," prioritizing the demonstration of networking capability over robust performance or complete standards compliance.

This blog post details the author's endeavor to implement a functional, albeit rudimentary, TCP/IP stack on the PRO/VENIX operating system, specifically targeting a pre-C89 standard compliant environment. Recognizing the limitations imposed by this older C standard, the author opted to utilize Slirp-CK, a compact and portable TCP/IP stack emulator designed for embedded systems. Slirp-CK itself is a fork of the popular Slirp user-mode networking project, chosen for its smaller footprint and compatibility with resource-constrained systems. The author emphasizes the "barely adequate" nature of the implementation, prioritizing functionality over performance or completeness.

The post walks through the process of integrating Slirp-CK with PRO/VENIX, outlining the necessary modifications and configurations. This involves adapting Slirp-CK's build process to conform to the pre-C89 compiler and linker toolchain available on PRO/VENIX. The author highlights specific challenges encountered during this adaptation, such as dealing with differences in header file availability and the absence of standard library functions present in later C revisions. These challenges necessitated modifications to both Slirp-CK's source code and the PRO/VENIX build environment.

The author's primary objective was to enable basic network connectivity within the PRO/VENIX environment, allowing for tasks such as transferring files via FTP or accessing remote systems through Telnet. While acknowledging that the resulting implementation lacks the performance and feature richness of modern TCP/IP stacks, the author considers it a successful proof-of-concept, demonstrating the feasibility of network communication even on a system as constrained as PRO/VENIX. The post concludes with a brief demonstration of the implemented stack, showcasing its ability to handle simple network operations. It also subtly hints at the possibility of future improvements and enhancements to the integration, although no concrete plans are outlined.

Summary of Comments ( 2 )
https://news.ycombinator.com/item?id=43741849

Hacker News users discuss the blog post about porting a TCP/IP stack (Slirp-CK) to the PRO/VENIX operating system. Several commenters express excitement and nostalgia for PRO/VENIX, sharing personal anecdotes about using it in the past. Some question the practical use cases, while others suggest potential applications like retro gaming or historical preservation. The technical details of the porting process are discussed, including the challenges of working with older hardware and software limitations. There's a general appreciation for the effort involved in preserving and expanding the capabilities of vintage systems. A few users mention interest in contributing to the project or exploring similar endeavors with other older operating systems.

The Hacker News post titled "Let's give PRO/VENIX a barely adequate, pre-C89 TCP/IP stack, featuring Slirp-CK" sparked a small but interesting discussion with a few compelling points.

One commenter expressed excitement about the project, particularly the use of Slirp-CK and its potential to bring TCP/IP networking to older systems. They also raised the question of whether this implementation could be adapted to other historical operating systems, specifically mentioning DEC RT-11/TSX, which predates even PRO/VENIX. This comment highlights the wider implications of the project beyond just PRO/VENIX and the potential interest in networking capabilities for vintage systems.

Another commenter, seemingly familiar with PRO/VENIX, discussed the challenges of running TCP/IP on the system due to its limited resources. They pointed out that while the original PRO/VENIX could technically run TCP/IP, it struggled to do much beyond basic telnet and FTP. They mentioned that later versions of PRO/VENIX, running on more powerful hardware like the 80386, were better suited for networking. This comment provides valuable context about the historical challenges of running TCP/IP on resource-constrained systems like the original PRO/VENIX.

The discussion also touched upon the practical limitations of using older hardware. One commenter mentioned the scarcity of suitable hardware, such as PDP-11 systems with working Ethernet controllers, and the difficulty of maintaining such systems. This practical consideration underscores the challenges involved in reviving and working with these older technologies, even with advancements like the Slirp-CK implementation.

Finally, a commenter shared a personal anecdote about their experience working with a PDP-11/70 running BSD UNIX in the late 1980s, noting the significant performance limitations even on that relatively powerful hardware compared to modern systems. This comment reinforces the point about the resource constraints of older systems and provides a historical perspective on the evolution of networking performance.

While the number of comments is limited, they provide valuable insights into the challenges and potential benefits of bringing modern networking capabilities to vintage operating systems like PRO/VENIX. They highlight the enthusiasm for such projects, the practical limitations of older hardware, and the historical context surrounding the development of TCP/IP on resource-constrained systems.

Android phones will soon reboot themselves after sitting unused for three days

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Posted: 2025-04-19 12:14:13

Android phones will soon automatically reboot if left unused for 72 hours. This change, arriving with Android 14, aims to improve security by clearing out temporary data and mitigating potential vulnerabilities that could be exploited while a device is powered on but unattended. This reboot occurs only when the phone is locked, encrypted, and not connected to a charger, minimizing disruption to users. Google notes that this feature can also help preserve battery life.

In a forthcoming update to the Android operating system, Google is introducing a new feature designed to enhance the security and privacy of devices left inactive for extended periods. Specifically, Android phones and tablets that remain powered on but unused for a duration of 72 hours, equivalent to three days, will automatically initiate a system reboot. This measure aims to mitigate potential security vulnerabilities that could arise from prolonged uptime, particularly when devices are lost or stolen.

This automatic reboot functionality operates on the premise that a device left untouched for three days is likely not in the immediate possession of its owner. By rebooting, the system clears any active sessions and temporary files, thereby reducing the window of opportunity for malicious actors to exploit potential vulnerabilities or gain unauthorized access to sensitive data. This is particularly relevant for devices without screen locks or with easily bypassed security measures.

The change will be implemented as part of a future Google Play system update, a mechanism that allows Google to distribute updates to core system components independently of full operating system updates. This approach ensures a broader and more timely rollout across a wide range of Android devices, irrespective of the manufacturer or specific Android version running on the device, as long as it supports Google Play Services. This bypasses the often lengthy and fragmented update process typical of the Android ecosystem, allowing for a more consistent and rapid deployment of critical security enhancements.

While the article does not specify the exact timeline for the rollout of this feature, it is characterized as "soon," suggesting that users can anticipate this change in the near future. The automatic reboot is positioned as a proactive security measure that adds an additional layer of protection for users in situations where their devices might be misplaced or compromised. It leverages the principle of least privilege, minimizing the potential attack surface by regularly clearing volatile memory and terminating potentially vulnerable processes.

Summary of Comments ( 88 )
https://news.ycombinator.com/item?id=43735902

Hacker News users largely criticized the proposed Android feature of automatic reboots after 72 hours of inactivity. Many considered it an unnecessary intrusion, arguing that users should have control over their devices and that the purported security benefits were minimal for average users. Several commenters suggested alternative solutions like remote wipe or enhanced lock screen security. Some questioned the actual security impact, suggesting a motivated attacker could simply wait out the 72 hours. A few users pointed out potential downsides like losing unsaved progress in apps or missing time-sensitive notifications. Others wondered if the feature would be optional or forced upon users, expressing a desire for greater user agency.

Walled Gardens Can Kill

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Posted: 2025-04-18 10:27:39

The blog post "Walled Gardens Can Kill" argues that closed AI ecosystems, or "walled gardens," pose a significant threat to innovation and safety in the AI field. By restricting access to models and data, these closed systems stifle competition, limit the ability of independent researchers to identify and mitigate biases and safety risks, and ultimately hinder the development of robust and beneficial AI. The author advocates for open-source models and data sharing, emphasizing that collaborative development fosters transparency, accelerates progress, and enables a wider range of perspectives to contribute to safer and more ethical AI.

The author, Anees Iqbal, posits in their blog post, "Walled Gardens Can Kill," a deeply concerning hypothesis regarding the potential ramifications of increasingly closed technological ecosystems, often referred to as "walled gardens." Mr. Iqbal argues that these digitally restricted environments, while seemingly offering convenience and curated experiences, pose a significant, and perhaps even life-threatening, risk to innovation, competition, and ultimately, to the very fabric of a free and open society.

Iqbal meticulously lays out the argument that walled gardens, by their very nature, stifle the cross-pollination of ideas and the serendipitous discoveries that often arise from the interconnectedness of open systems. He illustrates this point by drawing parallels to biological ecosystems, where isolated environments tend towards fragility and vulnerability, lacking the resilience and adaptability fostered by diverse interactions and genetic exchange. Within the digital realm, this translates to a stagnation of technological advancement, as developers are confined to the limitations imposed by the proprietary frameworks and APIs of the controlling entity. This, in turn, limits consumer choice and can lead to an over-reliance on a single provider, creating a potential single point of failure.

The author further elaborates on the dangers of these closed systems by highlighting the potential for censorship and control of information flow. He argues that the entities governing these walled gardens wield immense power over the narratives and perspectives presented to their users, effectively shaping public discourse and potentially suppressing dissenting voices. This control can extend to manipulating algorithms to prioritize certain content, thereby influencing user behavior and even shaping political outcomes. In a world increasingly reliant on these platforms for communication, commerce, and access to information, this concentration of power poses a grave threat to democratic principles and individual autonomy.

Furthermore, Iqbal underscores the economic repercussions of walled gardens, suggesting that they create an uneven playing field, favoring established players and hindering the emergence of new competitors. This can lead to monopolies or oligopolies that stifle innovation and extract excessive rents from consumers. The lack of interoperability between these closed systems further exacerbates the problem, creating artificial barriers to entry and limiting consumer choice.

Ultimately, Iqbal's argument culminates in the stark warning that the unchecked proliferation of walled gardens could have dire consequences, not only for the technological landscape, but also for the very future of society. He implores readers to consider the long-term implications of embracing these seemingly benign conveniences and to advocate for open standards and interoperability to ensure a more vibrant, resilient, and democratic digital future. He emphasizes the importance of fostering an environment that encourages innovation and competition, allowing for the free exchange of ideas and information, and safeguarding the fundamental principles of an open society.

Summary of Comments ( 57 )
https://news.ycombinator.com/item?id=43726672

HN commenters largely agree with the author's premise that closed ecosystems stifle innovation and limit user choice. Several point out Apple as a prime example, highlighting how its tight control over the App Store restricts developers and inflates prices for consumers. Some argue that while open systems have their downsides (like potential security risks), the benefits of interoperability and competition outweigh the negatives. A compelling counterpoint raised is that walled gardens can foster better user experience and security, citing Apple's generally positive reputation in these areas. Others note that walled gardens can thrive initially through superior product offerings, but eventually stagnate due to lack of competition. The detrimental impact on small developers, forced to comply with platform owners' rules, is also discussed.

The Hacker News post "Walled Gardens Can Kill" (https://news.ycombinator.com/item?id=43726672) discussing the linked article about the potential dangers of closed ecosystems has generated a moderate number of comments, exploring various facets of the issue.

Several commenters agree with the premise of the article, highlighting the stifling of innovation and competition that can occur within walled gardens. They point to examples of platforms leveraging their dominance to extract excessive rents or prioritize their own services, ultimately harming consumers and smaller developers. The control exerted over data within these ecosystems is also a recurring concern, with commenters worried about the implications for user privacy and the potential for misuse of information.

One compelling comment thread discusses the historical precedent of seemingly invincible walled gardens eventually being disrupted. Commenters mention examples like AOL and CompuServe, arguing that new technologies and changing user preferences can erode the walls over time. This perspective offers a counterpoint to the article's concerns, suggesting that while walled gardens pose a current threat, they are not necessarily permanent fixtures.

Another interesting discussion revolves around the trade-offs between convenience and openness. Some commenters acknowledge the user-friendly nature of integrated ecosystems, particularly for less tech-savvy individuals. They argue that the seamless experience offered by walled gardens can outweigh the potential downsides for many users. This raises the question of whether users are willing to sacrifice some control and openness for ease of use.

The issue of regulation is also touched upon. Some commenters advocate for government intervention to prevent the formation of overly dominant walled gardens. Others express skepticism about the effectiveness of regulation and the potential for unintended consequences.

Finally, a few commenters offer more nuanced perspectives, suggesting that the "walled garden" metaphor is not always accurate. They argue that some platforms exhibit characteristics of both open and closed systems, making it difficult to categorize them definitively. These commenters advocate for a more granular analysis that considers the specific features and policies of each platform.

While there isn't an overwhelming number of comments, the discussion provides valuable insights into the complexities of walled gardens, exploring both the potential risks and the counterarguments. The comments demonstrate a range of opinions and perspectives, highlighting the ongoing debate surrounding the balance between open and closed ecosystems in the digital world.

Unikernel Linux (UKL) (2023)

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Posted: 2025-04-18 08:11:45

Unikernel Linux (UKL) presents a novel approach to building unikernels by leveraging the Linux kernel as a library. Instead of requiring specialized build systems and limited library support common to other unikernel approaches, UKL allows developers to build applications using standard Linux development tools and a wide range of existing libraries. This approach compiles applications and the necessary Linux kernel components into a single, specialized bootable image, offering the benefits of unikernels – smaller size, faster boot times, and improved security – while retaining the familiarity and flexibility of Linux development. UKL demonstrates performance comparable to or exceeding existing unikernel systems and even some containerized deployments, suggesting a practical path to broader unikernel adoption.

The paper "Unikernel Linux (UKL)" introduces a novel approach to building unikernels, specialized single-address-space operating system images optimized for a specific application. Traditional unikernels, while offering advantages in terms of performance and security due to their minimized footprint, often necessitate porting applications to specialized libraries and frameworks, which can be a significant undertaking. UKL addresses this limitation by providing a compatibility layer that allows unmodified Linux applications to run directly within a unikernel environment.

The core innovation of UKL lies in its adaptation of the Linux kernel to function as a library operating system within a single address space. This is achieved by selectively including necessary kernel components and adapting them for the unikernel environment, including networking, file systems, and drivers. The paper details how the Linux kernel's internal structures and dependencies are managed within this context, including syscalls, memory management, and process scheduling. Specifically, UKL modifies the kernel's build system to create a custom library containing only the required kernel components, effectively emulating a POSIX-compliant environment. This approach significantly reduces the complexity of porting applications, as they can utilize familiar Linux system calls and libraries without modification.

UKL leverages the existing Linux driver ecosystem, allowing developers to include necessary drivers within the unikernel image. This is a significant advantage over other unikernel systems, which often require specialized driver implementations. The paper explains how UKL integrates drivers into the single-address-space environment and manages resource allocation.

Performance evaluations presented in the paper demonstrate that UKL achieves comparable performance to traditional Linux systems for various applications, while maintaining the benefits of a smaller footprint and improved security posture associated with unikernels. The authors benchmark UKL against standard Linux in several scenarios, including web serving and database operations, highlighting the performance trade-offs and benefits of their approach. The results show that while there might be a slight performance overhead in some cases due to the emulation layer, the overall performance is competitive, particularly given the ease of application porting.

Furthermore, the paper discusses the security implications of UKL, noting that the reduced attack surface inherent in unikernels contributes to a more secure execution environment. By including only the essential components necessary for the target application, UKL minimizes the potential vulnerabilities present in a full-fledged operating system.

In conclusion, UKL presents a compelling approach to unikernel development by enabling the execution of unmodified Linux applications within a unikernel environment. This approach significantly reduces the development effort required to create unikernels while retaining the performance and security advantages typically associated with them. The compatibility with the vast Linux ecosystem, including drivers and libraries, further enhances the practicality and appeal of UKL for a wide range of applications.

Summary of Comments ( 9 )
https://news.ycombinator.com/item?id=43726037

Several commenters on Hacker News expressed skepticism about Unikernel Linux (UKL)'s practical benefits, questioning its performance advantages over existing containerization technologies and expressing concerns about the complexity introduced by its specialized build process. Some questioned the target audience, wondering if the niche use cases justified the development effort. A few commenters pointed out the potential security benefits of UKL due to its smaller attack surface. Others appreciated the technical innovation and saw its potential for specific applications like embedded systems or highly specialized microservices, though acknowledging it's not a general-purpose solution. Overall, the sentiment leaned towards cautious interest rather than outright enthusiasm.

The Hacker News post titled "Unikernel Linux (UKL) (2023)" has generated several comments discussing the linked research paper. Several commenters express interest and enthusiasm for the concept of unikernels and their potential benefits, particularly in terms of security and performance.

One compelling thread discusses the tradeoffs between using UKL versus existing containerization technologies like Docker. A commenter points out that UKL aims to provide a more secure and performant environment by eliminating unnecessary components of a general-purpose OS, as opposed to containerization, which still carries the baggage of the underlying OS kernel. This leads to a discussion about the practical implications of adopting UKL, with commenters raising questions about the maturity of the technology and its compatibility with existing tools and workflows. The feasibility of running complex applications within UKL is also questioned, with one user pointing out potential challenges related to supporting various system calls and libraries.

Another user highlights the specific advantages of UKL's approach to library operating systems, suggesting that it offers a more streamlined and efficient way to build and deploy applications compared to traditional methods. They praise the innovative nature of the project and its potential to improve resource utilization.

Several commenters delve into the technical details of UKL, discussing its implementation and its relationship to other unikernel projects. One commenter expresses curiosity about the performance implications of using a single address space, a key characteristic of UKL. Others discuss the potential security benefits of using a more minimal kernel, reducing the attack surface compared to a traditional OS.

Some commenters express skepticism about the practical applicability of unikernels in general, questioning their ability to truly replace containers in the near future. They cite the limitations of unikernels in terms of device driver support and the challenges of porting existing applications. However, even skeptical commenters acknowledge the potential advantages of UKL's approach, particularly in niche use cases where security and performance are paramount. One commenter also points out the value of the research in potentially influencing the design of future containerization technologies, even if UKL itself doesn't become widely adopted.

Overall, the comments reflect a mixture of excitement, curiosity, and healthy skepticism about the potential of UKL and unikernels in general. The discussion highlights the tradeoffs involved in adopting this new technology, emphasizing the need for further development and evaluation before it can become a mainstream solution.

RNG and Cosine in Nix

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Posted: 2025-04-13 00:30:22

This post explores the challenges of generating deterministic random numbers and using cosine within Nix expressions. It highlights that Nix's purity, while beneficial for reproducibility, makes tasks like generating unique identifiers difficult without resorting to external dependencies or impure functions. The author demonstrates various approaches, including using the derivation name as a seed for a pseudo-random number generator (PRNG) and leveraging builtins.currentTime as a less deterministic but readily available alternative. The post also delves into the lack of a built-in cosine function in Nix and presents workarounds, like writing a custom implementation or relying on a pre-built library, showcasing the trade-offs between self-sufficiency and convenience.

This blog post explores the intricacies of generating random numbers and calculating the cosine of an angle within the Nix functional package manager, a tool used for building and deploying software. The author begins by highlighting the deterministic nature of Nix, emphasizing that even seemingly random operations must be reproducible given the same inputs. This presents a challenge for incorporating randomness, which by definition is non-deterministic. The post then details how Nix addresses this by using a derivations feature for introducing controlled randomness. Derivations are pure functions that produce build instructions, and they can include a special randomSeed attribute. This seed acts as the starting point for a pseudorandom number generator (PRNG), ensuring consistent results for a given derivation. The author demonstrates this with a practical example, showcasing how to generate a random floating-point number between 0 and 1 within a derivation. This is achieved using the lib.randomFloat function from Nixpkgs, which internally utilizes the Xoshiro256** PRNG. The author further elaborates on how one might seed the derivation with a specific value to reproduce the same "random" result across different builds or machines, illustrating the predictable nature of pseudorandomness.

Moving beyond simple random number generation, the post then tackles the seemingly unrelated topic of calculating the cosine of an angle. The author explains that Nix, prioritizing purity and reproducibility, does not directly offer a cos function in its standard library. Instead, the approach involves leveraging the stdenv.mkDerivation function to build a small C++ program that calculates the cosine. This C++ program utilizes the standard cmath library for the cosine calculation and outputs the result. The Nix derivation packages this process, ensuring that the compilation and execution steps are captured and reproducible. The post provides a detailed example of how to construct this derivation, including the necessary C++ code and Nix expressions. This illustrates how Nix can incorporate external tools and libraries for computations that aren't directly available within its core functionality, while still maintaining its core principles of determinism and reproducibility. The author emphasizes the advantages of this approach: by encapsulating the cosine calculation within a derivation, Nix ensures that the result is always consistent for a given input angle, regardless of the build environment. The post concludes by showcasing how to combine these two concepts – random number generation and cosine calculation – to generate a random point on the unit circle, demonstrating the power and flexibility of Nix derivations for managing complex computations within a reproducible framework.

Summary of Comments ( 0 )
https://news.ycombinator.com/item?id=43669057

Hacker News users discussed the blog post about reproducible random number generation in Nix. Several commenters appreciated the clear explanation of the problem and the proposed solution using a cosine function to distribute builds across build machines. Some questioned the practicality and efficiency of the cosine approach, suggesting alternatives like hashing or simpler modulo operations, especially given potential performance implications and the inherent limitations of pseudo-random number generators. Others pointed out the complexities of truly distributed builds in Nix and the need to consider factors like caching and rebuild triggers. A few commenters expressed interest in exploring the cosine method further, acknowledging its novelty and potential benefits in certain scenarios. The discussion also touched upon the broader challenges of achieving determinism in build systems and the trade-offs involved.

The Hacker News post titled "RNG and Cosine in Nix" sparked a discussion with several interesting comments.

One commenter questioned the practicality of the approach, pointing out that using a hash function directly would likely be simpler and more efficient than the proposed cosine-based method. They also expressed concern about potential bias introduced by using cosine and suggested that a more rigorous statistical analysis would be necessary to validate the randomness quality.

Another commenter echoed this sentiment, emphasizing the importance of proper statistical testing for random number generation. They recommended using established test suites like TestU01 to thoroughly evaluate the randomness properties of the generated sequence.

One user focused on the security implications, warning that the proposed method might not be suitable for cryptographic purposes due to potential predictability. They advised against using custom RNG solutions in security-sensitive contexts and recommended relying on well-vetted cryptographic libraries instead.

A further commenter offered a different perspective, suggesting that the approach might be useful for generating deterministic random values based on a seed. They envisioned applications in procedural generation, where consistent results are desirable.

Another individual highlighted the importance of understanding the underlying distribution of the generated random numbers. They noted that different applications may require different distributions (uniform, normal, etc.) and that simply generating seemingly random numbers without considering the distribution could lead to incorrect results.

Several commenters discussed the mathematical properties of the cosine function and its suitability for RNG. Some expressed skepticism, while others defended its potential, albeit with the caveat that careful analysis and testing are crucial.

Finally, some comments touched on the specific use case within Nix, the package manager mentioned in the title. They speculated about the potential benefits and drawbacks of using this method for generating unique identifiers or other random values within the Nix ecosystem. However, no definitive conclusions were drawn regarding its practical application in Nix.

Fedora change aims for 99% package reproducibility

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Posted: 2025-04-11 13:40:26

Fedora is implementing a change to enhance package reproducibility, aiming for a 99% success rate. This involves using "source date epochs" (SDE) which fixes build timestamps to a specific point in the past, eliminating variations caused by differing build times. While this approach simplifies reproducibility checks and reduces false positives, it won't address all issues, such as non-deterministic build processes within the software itself. The project is actively seeking community involvement in testing and reporting any remaining non-reproducible packages after the SDE switch.

The Linux Weekly News article titled "Fedora change aims for 99% package reproducibility" details a proposed and largely implemented shift in the Fedora Linux distribution's build system to prioritize and significantly enhance the reproducibility of software packages. Reproducibility, in this context, means that building a given package version from source code, regardless of the build environment or time, should result in bit-for-bit identical binary packages. This has significant implications for security and trust, allowing independent verification of builds and ensuring that malicious modifications haven't been introduced during the build process.

The article explains that Fedora has been working towards this goal for several years, making incremental improvements to their build infrastructure and tooling. This latest effort focuses on tackling the remaining 1% of packages that are not currently reproducible. These problematic packages often encounter issues stemming from embedded timestamps, build paths leaking into binaries, and non-deterministic behavior in build tools or libraries.

The proposed solution involves implementing stricter build rules and utilizing techniques like build sandboxing and source date epoch (SDE) usage. Build sandboxing isolates the build process within a controlled environment, minimizing the influence of external factors. SDE sets a consistent timestamp for all files within the build environment, effectively eliminating time-based variations in the resulting binaries.

The Fedora project aims to achieve 99% package reproducibility by enforcing these practices and systematically addressing the issues in the remaining non-reproducible packages. This ambitious goal necessitates close collaboration between package maintainers and the Fedora build system team. Maintainers will need to adapt their build scripts and potentially modify their software to comply with the new reproducibility requirements. The article highlights the importance of tooling and automation to assist maintainers in this transition, mentioning the development of automated rebuild and comparison tools to identify and diagnose reproducibility issues.

While the ultimate goal is 100% reproducibility, the article acknowledges the inherent challenges in achieving this for all packages. Some software might rely on inherently non-deterministic processes, making perfect reproducibility impossible. Nevertheless, reaching 99% reproducibility represents a significant milestone in improving the security and trustworthiness of the Fedora distribution. The article concludes by emphasizing the ongoing nature of this work and the community's commitment to continually improving the build process and enhancing package reproducibility.

Summary of Comments ( 195 )
https://news.ycombinator.com/item?id=43653672

Hacker News users discuss the implications of Fedora's push for reproducible builds, focusing on the practical challenges. Some express skepticism about achieving true reproducibility given the complexity of build environments and dependencies. Others highlight the security benefits, emphasizing the ability to verify package integrity and prevent malicious tampering. The discussion also touches on the potential trade-offs, like increased build times and the need for stricter control over build processes. A few commenters suggest that while perfect reproducibility might be difficult, even partial reproducibility offers significant value. There's also debate about the scope of the project, with some wondering about the inclusion of non-free firmware and the challenges of reproducing hardware-specific optimizations.

The Hacker News post "Fedora change aims for 99% package reproducibility" generated a moderate discussion with several insightful comments. Many commenters expressed support for the initiative, viewing reproducible builds as a crucial step towards enhancing software security and trustworthiness.

One compelling comment highlighted the significance of reproducibility in verifying the integrity of downloaded packages, ensuring they haven't been tampered with. This resonates with the broader security concerns around supply chain attacks, where malicious actors compromise software during the build process. Reproducibility offers a mechanism to verify the authenticity of builds by independently recreating them and comparing the results.

Another commenter delved into the technical challenges of achieving full reproducibility, particularly with aspects like timestamps and build paths embedded within binaries. They emphasized the need for careful consideration of these details to ensure consistent build outputs. This point underscores the complexity of implementing reproducible builds and the meticulous effort required by package maintainers.

Some users questioned the practicality of aiming for 99% reproducibility, wondering about the remaining 1% and the potential difficulties in achieving perfect reproducibility. This prompted a discussion about the trade-offs between striving for ideal reproducibility and the pragmatic limitations imposed by certain software components or build processes.

Furthermore, a comment mentioned the importance of tools and infrastructure for verifying reproducibility, suggesting that simply rebuilding packages isn't sufficient. Robust verification mechanisms are essential for ensuring the integrity and consistency of the reproduced builds.

Several comments also touched upon the broader benefits of reproducible builds beyond security, such as easier debugging, improved transparency, and greater community involvement in the software development lifecycle. These comments showcase the wide-ranging impact of reproducible builds on the software ecosystem.

Overall, the comments on Hacker News generally demonstrate a positive reception towards Fedora's initiative for reproducible builds, recognizing its potential to improve software security and reliability. The discussion also acknowledges the technical complexities and the need for robust tooling to effectively implement and verify reproducible builds.

Show HN: I built a Rust crate for running unsafe code safely

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Posted: 2025-04-06 13:28:48

mem-isolate is a Rust crate designed to execute potentially unsafe code within isolated memory compartments. It leverages Linux's memfd_create system call to create anonymous memory mappings, allowing developers to run untrusted code within these confined regions, limiting the potential damage from vulnerabilities or exploits. This sandboxing approach helps mitigate security risks by restricting access to the main process's memory, effectively preventing malicious code from affecting the wider system. The crate offers a simple API for setting up and managing these isolated execution environments, providing a more secure way to interact with external or potentially compromised code.

The Hacker News post titled "Show HN: I built a Rust crate for running unsafe code safely" introduces mem-isolate, a new Rust library designed to mitigate the risks associated with executing potentially unsafe code. The core concept behind mem-isolate is compartmentalization. It achieves this by leveraging Rust's ownership system and memory safety guarantees to create isolated memory regions, effectively sandboxing the execution of untrusted or volatile code.

This sandboxing prevents potential memory corruption or other undefined behavior from affecting the primary application. If the isolated code attempts an illegal memory access or performs another unsafe operation that would typically lead to a crash or vulnerability, the effects are confined within the isolated memory region. The main application remains unaffected, enhancing overall system stability and security.

The crate provides a mechanism to execute a given function within this confined environment. It works by forking the current process and establishing the isolated memory space within the child process. The target function then runs solely within this isolated child process. Any memory violations or crashes are isolated to the child process, preventing them from propagating to the parent and compromising the main application. The parent process can then continue operating normally.

The developer highlights that while mem-isolate focuses on memory safety, it doesn't address all potential security concerns. For example, it doesn't inherently protect against issues like infinite loops or excessive resource consumption within the isolated code. These aspects would require additional monitoring and control mechanisms.

Essentially, mem-isolate offers a way to run potentially dangerous code within a controlled environment, significantly reducing the risks associated with executing untrusted code within a Rust application, particularly focusing on preventing memory-related vulnerabilities from impacting the core application's integrity.

Summary of Comments ( 5 )
https://news.ycombinator.com/item?id=43601301

Hacker News users discussed the practicality and security implications of the mem-isolate crate. Several commenters expressed skepticism about its ability to truly isolate unsafe code, particularly in complex scenarios involving system calls and shared resources. Concerns were raised about the performance overhead and the potential for subtle bugs in the isolation mechanism itself. The discussion also touched on the challenges of securely managing memory in Rust and the trade-offs between safety and performance. Some users suggested alternative approaches, such as using WebAssembly or language-level sandboxing. Overall, the comments reflected a cautious optimism about the project but acknowledged the difficulty of achieving complete isolation in a practical and efficient manner.

The Hacker News post "Show HN: I built a Rust crate for running unsafe code safely" (linking to the mem-isolate crate) generated a moderate amount of discussion, mostly focused on the complexities and nuances of memory safety in Rust, and whether the crate truly offers a "safe" solution for running unsafe code.

Several commenters express skepticism about the claim of "safely" running unsafe code. One points out the inherent contradiction, suggesting the term is an oxymoron. Another argues that true safety requires formal verification, and anything short of that is merely reducing the attack surface rather than eliminating it. This sentiment is echoed by another commenter who highlights the difficulty in proving the soundness of the approach and the potential for subtle bugs to undermine the isolation.

A few comments delve into the specifics of mem-isolate's implementation. One user questions its practicality for real-world scenarios, suggesting that the overhead of serialization and deserialization, coupled with the limitations on system call access, could severely limit its usefulness. They also mention the potential performance impact and the challenge of managing data dependencies between isolated processes.

The discussion also touches upon alternative approaches to isolating unsafe code, such as WebAssembly. One commenter mentions Wasmtime as a more mature and robust solution, although they acknowledge that Wasmtime might not be suitable for all use cases. Another suggests using language-level sandboxing features provided by some languages.

Some users discuss the trade-offs between security and performance. One commenter notes that while complete memory safety is desirable, it often comes at a cost to performance. They suggest that in certain situations, a calculated risk with less strict isolation might be acceptable if performance is a critical factor.

Finally, a few comments express general interest in the project and commend the author for tackling a challenging problem. They acknowledge the difficulty of achieving true memory safety in systems programming and appreciate the effort to improve the security of Rust code. However, even these positive comments maintain a cautious tone, reflecting the overall skepticism towards the claim of absolute safety.

Introduction to System Programming in Linux (Early Access)

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Posted: 2025-03-30 19:22:36

This book, "Introduction to System Programming in Linux," offers a practical, project-based approach to learning low-level Linux programming. It covers essential concepts like process management, memory allocation, inter-process communication (using pipes, message queues, and shared memory), file I/O, and multithreading. The book emphasizes hands-on learning through coding examples and projects, guiding readers in building their own mini-shell, a multithreaded web server, and a key-value store. It aims to provide a solid foundation for developing system software, embedded systems, and performance-sensitive applications on Linux.

This forthcoming book, "Introduction to System Programming in Linux" by Kaiwan N Billimoria, offers a comprehensive exploration of the foundational concepts and practical skills required for system-level programming within the Linux environment. The book promises a deep dive into the intricacies of the Linux kernel and its interaction with user-space programs, aiming to equip readers with the knowledge to develop robust, efficient, and secure system software. It caters to both novice programmers seeking an entry point into lower-level development and experienced programmers looking to solidify their understanding of Linux internals.

The book begins by establishing a solid bedrock of fundamental concepts, covering crucial topics such as the operating system's role as a resource manager, process management, including process creation, termination, and inter-process communication, memory management encompassing dynamic memory allocation and virtual memory, and file system operations involving file manipulation and input/output operations. Furthermore, it delves into the critical area of concurrency and synchronization, addressing the challenges of managing multiple threads and processes within the Linux environment and techniques for ensuring data consistency and preventing race conditions.

Building upon these foundational elements, the book proceeds to explore more advanced system programming paradigms. It provides an in-depth look at inter-process communication (IPC) mechanisms, covering various techniques like pipes, sockets, and shared memory for enabling efficient data exchange between processes. It explores the intricacies of signal handling, explaining how programs can respond to asynchronous events and handle exceptions gracefully. Additionally, the book delves into timers and timing facilities within Linux, which are essential for real-time applications and scheduling tasks. Furthermore, it examines the complex topic of synchronization primitives such as mutexes, semaphores, and condition variables, equipping readers with the tools to manage concurrent access to shared resources effectively.

The book also provides a comprehensive treatment of the Linux system call interface, offering a practical understanding of how user-space programs interact with the kernel to perform system-level operations. It elucidates the intricacies of working with the command-line interface and shell scripting, providing valuable tools for system administrators and developers alike. The book emphasizes practical application through numerous code examples and hands-on exercises, reinforcing theoretical concepts and enabling readers to develop real-world system programming skills. It adopts a progressive approach, starting with fundamental concepts and gradually introducing more advanced topics, ensuring a clear and structured learning path.

Finally, "Introduction to System Programming in Linux" promises to empower readers to create efficient, reliable, and secure system software within the Linux operating system, bridging the gap between theoretical understanding and practical implementation. It is being published by No Starch Press, known for their high-quality technical books, and is currently available for early access, allowing readers to engage with the material as it is being developed and provide valuable feedback.

Summary of Comments ( 6 )
https://news.ycombinator.com/item?id=43526763

Hacker News users discuss the value of the "Introduction to System Programming in Linux" book, particularly for beginners. Some commenters highlight the importance of Kay Robbins and Dave Robbins' previous work, expressing excitement for this new release. Others debate the book's relevance given the wealth of free online resources, although some counter that a well-structured book can be more valuable than scattered web tutorials. Several commenters express interest in seeing more practical examples and projects within the book, particularly those focusing on modern systems and real-world applications. Finally, there's a brief discussion about alternative learning resources, including the Linux Programming Interface and Beej's Guide.

The Hacker News post for "Introduction to System Programming in Linux (Early Access)" has a modest number of comments, generating a brief discussion around the book and system programming resources in general.

One commenter expresses excitement about the book, specifically mentioning their interest in the chapter on memory mapping. They also highlight the author's previous work, "The Linux Programming Interface," as a valuable resource, implying a positive expectation for this new book.

Another commenter questions the necessity of yet another book on Linux system programming, given the existing abundance of online resources and the classic "Advanced Programming in the Unix Environment" (APUE) by Stevens. They acknowledge the potential value of a more modern approach, but seem unconvinced of its unique contribution. This sparks a small thread where another user counters that while online resources are helpful, a well-structured book offers a more comprehensive and pedagogical approach. They argue that books provide a curated path through the material, which can be more beneficial for learning than piecing together fragmented information online. This commenter also points to the potential value of having up-to-date information specifically regarding newer system calls and best practices, differentiating the new book from the older, though still respected, APUE.

Another comment simply provides a link to the author's website, offering an additional avenue for information about the book and the author's other work.

Finally, a commenter asks about the book's coverage of eBPF, a technology relevant to modern Linux system programming. Unfortunately, this question remains unanswered in the thread.

In summary, the comments section reflects a mixed reception. Some express enthusiasm for a new resource on Linux system programming, especially one by a respected author, while others question its value proposition in a field already saturated with information. The discussion touches upon the benefits of structured learning offered by books compared to online resources and the desire for up-to-date coverage of modern technologies like eBPF.

Paged Out #6 [pdf]

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Posted: 2025-03-29 18:12:03

Paged Out #6 explores the growing complexity in software, focusing on the challenges of debugging. It argues that traditional debugging methods are becoming inadequate for modern systems, which often involve distributed architectures, asynchronous operations, and numerous interacting components. The zine dives into various advanced debugging techniques like reverse debugging, using eBPF for observability, and applying chaos engineering principles to uncover vulnerabilities. It highlights the importance of understanding system behavior as a whole, rather than just individual components, advocating for tools and approaches that provide a more holistic view of execution flow and state. Finally, it touches on the psychological aspects of debugging, emphasizing the need for patience, persistence, and a structured approach to problem-solving in complex environments.

Paged Out #6, subtitled "Systems We Love," explores the profound appreciation software developers have for particular systems, tools, and technologies. It delves into the reasons behind this affection, often stemming from a combination of practical effectiveness and a deeper, more personal connection. The issue features a collection of articles from various contributors, each detailing their individual love for specific systems.

The first article, "Loving SQLite," by Michael Lynch, expounds on the virtues of the ubiquitous embedded database. Lynch highlights its reliability, portability, ease of use, and surprising power, illustrating how it serves as a dependable foundation for countless applications. He praises its self-contained nature, its lack of dependencies, and the simplicity of its API, making it a joy to integrate and work with. The piece emphasizes the understated elegance of SQLite and its ability to perform admirably even in demanding situations.

Next, "Plan 9 from Bell Labs: A Love Story" by Amos Jeffries recounts a long-standing admiration for the Plan 9 operating system. Jeffries details his initial exposure to the system, its unique approach to resource management using the 9P protocol, and its influence on his understanding of distributed computing. He describes the system's elegant design, its consistent philosophy, and the sense of community surrounding it. The article portrays Plan 9 not just as an operating system, but as a source of inspiration and a testament to innovative thinking.

Following this, "Loving Xmonad" by Aditya Siram dives into the world of tiling window managers, specifically focusing on Xmonad. Siram explains his preference for Xmonad's declarative configuration, its customizability, and the power it provides over the desktop environment. He emphasizes the efficiency gained through keyboard-driven workflows and the ability to tailor the window management experience to individual needs. The article highlights the joy of mastering Xmonad and the sense of control it provides.

"Why I Love Common Lisp (and You Should Too!)" by Eric Normand then makes a compelling case for the enduring relevance of Common Lisp. Normand discusses the language's powerful macro system, its dynamic nature, and the extensive standard library. He highlights its stability, maturity, and the active community that continues to support and develop it. The article portrays Common Lisp as a language that empowers developers to tackle complex problems with elegance and expressiveness.

The issue concludes with "Loving Smalltalk" by Jan Vrany, exploring the distinct philosophy and unique features of the Smalltalk programming environment. Vrany discusses the live coding capabilities, the image-based persistence, and the object-oriented paradigm at the heart of Smalltalk. He emphasizes the seamless integration of the development environment and the powerful tools it provides for introspection and debugging. The article paints a picture of Smalltalk as a dynamic and interactive system that fosters exploration and experimentation.

Throughout Paged Out #6, the recurring theme is the deep connection developers can forge with the tools they use. Each article reveals a personal journey of discovery and appreciation, highlighting not just the technical merits of these systems, but also their impact on the way developers think and create. The issue serves as a celebration of these beloved systems and a testament to the enduring power of well-designed software.

Summary of Comments ( 47 )
https://news.ycombinator.com/item?id=43517375

HN users generally praised the issue of Paged Out, finding the articles well-written and insightful. Several commenters highlighted specific pieces, such as the one on "The Spectre of Infinite Retry" and another discussing the challenges of building a database on top of a distributed consensus system. The article on the Unix philosophy also generated positive feedback. Some users appreciated the magazine's focus on systems programming and lower-level topics. There was some light discussion of the practicality of formal methods in software development, prompted by one of the articles. Overall, the reception was very positive with many expressing anticipation for future issues.

The Hacker News post titled "Paged Out #6 [pdf]" linking to a PDF magazine has generated a moderate amount of discussion, with several commenters sharing their thoughts and opinions.

Several users praise the overall quality and content of Paged Out magazine. One commenter describes it as "a nice zine", highlighting its enjoyable and easily digestible format, perfect for casual reading. Another user expresses their appreciation for the magazine's in-depth articles, contrasting it favorably with the often superficial content found in other technical blogs. They specifically mention the articles on "calculators and old databases" as being particularly insightful.

A key point of discussion revolves around the article on optimizing binary search. One commenter questions the practicality of the optimization techniques presented, arguing that the potential performance gains are negligible in most real-world scenarios and might even introduce complexity that outweighs the benefits. Another commenter challenges this view, suggesting that while the absolute gains might be small, they can be significant in specific performance-critical applications. This exchange highlights a common debate in software engineering: balancing theoretical optimization with practical considerations.

Another commenter shifts the focus to the magazine's physical characteristics, comparing it favorably to the now-defunct "2600" magazine. They appreciate the zine's size and format, suggesting a nostalgic connection to older print publications.

Beyond specific articles, there's a general appreciation for the existence and continuation of Paged Out. Commenters express their support for independent publications that explore technical topics in a more thoughtful and in-depth manner than typical online content.

Finally, one commenter raises a technical issue related to accessing the PDF on mobile devices. They describe an issue where the PDF renders poorly on their iPad, potentially impacting the readability and accessibility of the content. This points to the challenges of distributing content across diverse platforms and devices.

Google makes Android development private, will continue open source releases

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Posted: 2025-03-26 19:21:51

Google is shifting internal Android development to a private model, similar to how it develops other products. While Android will remain open source, the day-to-day development process will no longer be publicly visible. Google claims this change will improve efficiency and security. The company insists this won't affect the open-source nature of Android, promising continued AOSP releases and collaboration with external partners. They anticipate no changes to the public bug tracker, release schedules, or the overall openness of the platform itself.

In a move that has stirred discussion, Google has restructured its approach to Android development, shifting a significant portion of the process behind closed doors while simultaneously reaffirming its commitment to the open-source nature of the Android Open Source Project (AOSP). This represents a nuanced alteration in strategy, not a complete abandonment of open development. Essentially, Google will now conduct the majority of its Android development work internally, privately iterating and refining new features and functionalities. This internal development cycle will involve the creation of private branches of the Android codebase, allowing Google engineers to work independently and at a potentially faster pace, free from the immediate scrutiny and constraints of public collaboration.

Following this internal development phase, Google will then merge these privately developed features and changes into the public AOSP repository. This "gated" model of development ensures that while the core development process is held privately, the resulting code remains accessible to the open-source community, manufacturers, and developers. This strategy aims to strike a balance between Google's desire for greater control over the development roadmap and timeline, and the benefits of maintaining an open-source ecosystem.

The article highlights that this change will not affect the open-source licensing of Android or the ability of manufacturers and developers to customize and distribute the operating system. AOSP will continue to serve as the foundation upon which Android is built, with Google contributing its internally developed changes back to the public project. The shift towards a more internal, private development model is primarily intended to streamline Google's internal processes, potentially allowing for faster iteration and more cohesive implementation of new features. It also potentially affords Google greater control over the direction of Android's development, mitigating fragmentation and ensuring a more unified user experience across devices. However, this change also raises questions regarding the degree of influence the broader community will have on the future of Android, and whether this shift signals a broader trend towards a more centralized development model within the open-source ecosystem. The article emphasizes that Google remains committed to open source, but the long-term implications of this change in development strategy remain to be seen.

Summary of Comments ( 14 )
https://news.ycombinator.com/item?id=43485950

Hacker News users largely expressed skepticism and concern over Google's shift towards internal Android development. Many questioned whether "open source releases" would truly remain open if Google's internal development diverged significantly, leading to a de facto closed-source model similar to iOS. Some worried about potential stagnation of the platform, with fewer external contributions and slower innovation. Others saw it as a natural progression for a maturing platform, focusing on stability and polish over rapid feature additions. A few commenters pointed out the potential benefits, such as improved security and consistency through tighter control. The prevailing sentiment, however, was cautious pessimism about the long-term implications for Android's openness and community involvement.

The Hacker News post discussing Ars Technica's article "Google makes Android development private, will continue open source releases" has generated a substantial discussion with diverse viewpoints.

Several commenters express skepticism about Google's claim that this move will improve efficiency and security. They argue that hiding the development process reduces transparency and makes it harder for the community to identify and report potential issues. Some suggest this is a move towards greater control over Android's direction, potentially limiting customization options and favoring Google's own services. The comparison to Apple's closed-source iOS development is made multiple times, with concerns raised about the potential for a similar ecosystem developing around Android.

A recurring theme is the perceived disconnect between Google's open-source rhetoric and its actions. Commenters point to past instances where Google has seemingly abandoned or de-emphasized open-source projects, leading to distrust of their long-term commitment to Android's openness. Some speculate that this shift might be driven by competitive pressures or a desire to streamline development, even at the cost of community involvement.

Some commenters offer a more nuanced perspective, acknowledging the potential benefits of a more centralized development model while still expressing reservations. They suggest that faster iteration and improved security are indeed possible, but emphasize the importance of continued community engagement and transparency in the open-source releases. The idea that Google might be shifting towards a "hybrid" approach, where core development is private but contributions and feedback are still welcomed, is discussed.

A few commenters focus on the practical implications for developers, particularly those working on custom ROMs or contributing to AOSP. Concerns are raised about the potential difficulties in understanding and adapting to changes made behind closed doors. The impact on the broader Android ecosystem, including device manufacturers and app developers, is also discussed.

Finally, some comments offer more cynical interpretations, suggesting that this move is primarily motivated by a desire to limit fragmentation and exert greater control over the Android platform. The potential for increased monetization through tighter integration with Google's services is also mentioned.

Overall, the comments reflect a mixture of skepticism, concern, and cautious optimism about the future of Android development. While some see potential benefits in a more centralized approach, the majority express reservations about the implications for transparency, community involvement, and the long-term health of the open-source ecosystem.

Entropy Attacks

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Posted: 2025-03-25 12:20:38

The blog post "Entropy Attacks" argues against blindly trusting entropy sources, particularly in cryptographic contexts. It emphasizes that measuring entropy based solely on observed outputs, like those from /dev/random, is insufficient for security. An attacker might manipulate or partially control the supposedly random source, leading to predictable outputs despite seemingly high entropy. The post uses the example of an attacker influencing the timing of network packets to illustrate how seemingly unpredictable data can still be exploited. It concludes by advocating for robust key-derivation functions and avoiding reliance on potentially compromised entropy sources, suggesting deterministic random bit generators (DRBGs) seeded with a high-quality initial seed as a preferable alternative.

Daniel J. Bernstein, in his blog post "Entropy Attacks," meticulously dissects the concept of entropy estimation within the realm of cryptography, specifically focusing on its application in generating supposedly random numbers for cryptographic keys. He argues that conventional entropy estimation techniques are fundamentally flawed and can lead to significant security vulnerabilities, leaving systems susceptible to attack. Instead of relying on abstract statistical measures of entropy, Bernstein advocates for a more concrete and pragmatic approach: demonstrably obtaining unpredictable bits.

Bernstein begins by elucidating the conventional wisdom regarding entropy estimation. This approach typically involves analyzing the potential sources of randomness within a system, such as mouse movements, keyboard timings, or network activity. Each source is assigned an estimated entropy value, reflecting the perceived unpredictability of its output. These individual entropy estimations are then combined to determine the overall entropy of the generated random numbers.

However, Bernstein argues that these estimations are inherently imprecise and often overly optimistic. He points out that attackers may possess more knowledge about the system than assumed, enabling them to predict the supposedly random bits with higher accuracy than the entropy estimations would suggest. He illustrates this with several examples where seemingly random sources can be influenced or predicted by an astute attacker. For instance, an attacker might analyze network traffic patterns or exploit vulnerabilities in peripheral drivers to gather information about the "random" data being collected.

Furthermore, Bernstein criticizes the common practice of combining entropy estimates from different sources. He contends that simply adding the individual entropy values doesn't accurately represent the overall entropy, as the sources may be correlated or influenced by common factors. This can lead to a significant overestimation of the true randomness of the generated numbers.

Instead of relying on these potentially flawed entropy estimations, Bernstein proposes an alternative approach focused on acquiring demonstrably unpredictable bits. He suggests using sources of randomness that are inherently difficult to predict, even by a well-informed attacker. One such example is utilizing high-quality random number generators based on physical phenomena, like radioactive decay or thermal noise, which are inherently unpredictable. Another approach is to leverage publicly verifiable randomness beacons, which provide publicly accessible random bits generated through robust and transparent processes.

He further emphasizes the importance of rigorous testing and verification of the randomness generation process. Instead of relying on theoretical entropy estimations, Bernstein advocates for empirical testing using statistical randomness tests to ensure the generated numbers exhibit the expected properties of true randomness.

In conclusion, Bernstein's "Entropy Attacks" serves as a cautionary tale against overreliance on conventional entropy estimations in cryptography. He argues that these estimations are often inaccurate and can lead to a false sense of security. He advocates for a shift towards demonstrably acquiring unpredictable bits and rigorously testing the randomness of generated numbers, ensuring the security of cryptographic systems against potential attacks.

Summary of Comments ( 13 )
https://news.ycombinator.com/item?id=43470339

The Hacker News comments discuss the practicality and effectiveness of entropy-reduction attacks, particularly in the context of Bernstein's blog post. Some users debate the real-world impact, pointing out that while theoretically interesting, such attacks often rely on unrealistic assumptions like attackers having precise timing information or access to specific hardware. Others highlight the importance of considering these attacks when designing security systems, emphasizing defense-in-depth strategies. Several comments delve into the technical details of entropy estimation and the challenges of accurately measuring it. A few users also mention specific examples of vulnerabilities related to insufficient entropy, like Debian's OpenSSL bug. The overall sentiment suggests that while these attacks aren't always easily exploitable, understanding and mitigating them is crucial for robust security.

The Hacker News post titled "Entropy Attacks" links to a blog post by Daniel J. Bernstein on entropy estimation. The discussion in the comments section revolves around the complexities and nuances of entropy estimation, particularly in the context of cryptographic systems. Several commenters engage with the technical details presented in Bernstein's post.

One commenter highlights the difficulty of estimating entropy accurately, especially when dealing with real-world sources that might not exhibit ideal randomness. They mention the "haveged" program as an example of a tool attempting to generate entropy from hardware events, but acknowledge the challenges in ensuring its true randomness.

Another commenter delves into the distinction between Shannon entropy and min-entropy, emphasizing that cryptographic operations rely on min-entropy for security. They point out that measuring min-entropy is inherently more difficult than measuring Shannon entropy.

The idea of "compressing" randomness into a smaller, higher-entropy form is also discussed. Commenters explain that while it's possible to extract a shorter, more uniformly random string from a longer, less random one, this process doesn't magically create entropy. The output's entropy is fundamentally limited by the input's entropy.

One comment specifically references the use of cryptographic hash functions as randomness extractors. They explain how these functions can transform a source with uneven entropy distribution into a more uniformly random output, suitable for cryptographic keys.

A few commenters touch upon the practical implications of entropy estimation in system security. They acknowledge the difficulty of achieving truly random numbers in software and mention hardware random number generators (RNGs) as a more reliable source. They also discuss how insufficient entropy can lead to vulnerabilities in security systems.

Finally, some comments offer further reading on related topics, such as the NIST publication on entropy sources and various academic papers on randomness extraction. Overall, the comments section provides valuable insights and perspectives on the challenges of entropy estimation and its crucial role in cryptography.

The case of the critical section that let multiple threads enter a block of code

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Posted: 2025-03-23 08:14:25

A developer encountered a perplexing bug where multiple threads were simultaneously entering a supposedly protected critical section. The root cause was an unexpected optimization performed by the compiler. A loop containing a critical section, protected by EnterCriticalSection and LeaveCriticalSection, was optimized to move the EnterCriticalSection call outside the loop. Consequently, the lock was acquired only once, allowing all loop iterations for a given thread to proceed concurrently, violating the intended mutual exclusion. This highlights the subtle ways compiler optimizations can interact with threading primitives, leading to difficult-to-debug concurrency issues.

Raymond Chen's blog post, "The case of the critical section that let multiple threads enter a block of code," details a perplexing debugging scenario involving a critical section that appeared to be malfunctioning, allowing multiple threads to access a supposedly protected code block concurrently. The developer, baffled by this behavior, observed that the critical section was indeed being entered and exited correctly by each thread, yet the protected code was still being executed simultaneously. This contradicted the fundamental purpose of a critical section, which is to ensure exclusive access to shared resources by only one thread at a time.

Chen explains that the issue stemmed from a misunderstanding of how the specific critical section was being used. The developer had created a global critical section object, intending to use it to synchronize access to a particular block of code across all threads. However, inside the function containing the protected code, the developer was creating a local variable also named after the global critical section object. This shadowing effectively masked the global critical section. Each thread entering the function created its own independent, local critical section object on the stack. Consequently, while each thread dutifully entered and exited its own local critical section, these separate critical sections provided no inter-thread synchronization. The global critical section remained entirely unused, and concurrent execution within the supposedly protected code block continued unabated.

The post emphasizes the importance of understanding variable scoping rules and the dangers of unintentional variable shadowing. In this case, the seemingly correct usage of EnterCriticalSection and LeaveCriticalSection concealed the underlying problem. The developer's assumption that the critical section was functioning globally led to a difficult-to-diagnose bug. The resolution involved removing the local variable declaration, allowing the code to correctly utilize the shared, global critical section and enforce proper mutual exclusion. This restored the intended behavior, ensuring only one thread could execute the protected code block at any given moment. The post concludes by implicitly advising readers to be mindful of naming conventions and scoping rules, particularly when dealing with synchronization primitives like critical sections, to avoid similar pitfalls.

Summary of Comments ( 26 )
https://news.ycombinator.com/item?id=43451525

Hacker News users discussed potential causes for the described bug where a critical section seemed to allow multiple threads. Some pointed to subtle issues with the provided code example, suggesting the LeaveCriticalSection might be executed before the InitializeCriticalSection, due to compiler reordering or other unexpected behavior. Others speculated about memory corruption, particularly if the CRITICAL_SECTION structure was inadvertently shared or placed in writable shared memory. The possibility of the debugger misleading the developer due to its own synchronization mechanisms also arose. Several commenters emphasized the difficulty of diagnosing such race conditions and recommended using dedicated tooling like Application Verifier, while others suggested simpler alternatives for thread synchronization in such a straightforward scenario.

The Hacker News post "The case of the critical section that let multiple threads enter a block of code" (linking to a Microsoft blog post about a tricky multithreading bug) has several comments discussing the nuances of the bug and its solution.

Several commenters focus on the surprising nature of the bug, given its simplicity. One commenter highlights the counter-intuitive behavior of InterlockedIncrement not acting as a full memory barrier, leading to the erroneous assumption that incrementing a counter within a critical section guarantees mutual exclusion. They explain how this specific scenario, combined with the compiler's optimization of register caching, allows multiple threads to perceive the same counter value simultaneously, thus bypassing the intended locking mechanism.

Another commenter delves deeper into the specifics of memory ordering and how the lack of acquire/release semantics in the original code allows for the observed behavior. They point out that the crucial aspect of the fix is not just the use of InterlockedIncrementAcquire/InterlockedDecrementRelease but ensuring the correct memory ordering guarantees to prevent out-of-order execution. They expand on this by explaining how even seemingly simple operations can have subtle implications in a multithreaded environment, especially when dealing with shared memory.

The discussion also touches upon the challenges of debugging such issues. One commenter notes the difficulty of reproducing and diagnosing these types of bugs due to their dependence on specific hardware, compiler optimizations, and timing. They suggest that using specific compiler flags to control memory ordering could be helpful in certain situations.

Furthermore, the conversation extends to broader aspects of concurrent programming. One commenter suggests that the complexity of these issues highlights the need for higher-level synchronization primitives and abstractions that encapsulate the complexities of memory ordering and locking. They argue that relying on low-level operations like InterlockedIncrement can easily lead to subtle bugs, especially for developers not intimately familiar with the intricacies of memory models and compiler behavior. This commenter advocates for using tools and languages that offer safer concurrency mechanisms.

Finally, some comments provide additional context about the historical evolution of memory models and the challenges faced by developers in the past. One commenter mentions how older x86 processors offered stronger memory ordering guarantees by default, leading to code that worked correctly then but breaks on newer hardware with weaker memory models. This highlights the ongoing evolution of hardware and the importance of understanding the underlying memory model when writing concurrent code.

Quitting an Intel x86 Hypervisor

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Posted: 2025-03-22 20:42:04

This blog post details the surprisingly complex process of gracefully shutting down a nested Intel x86 hypervisor. It focuses on the scenario where a management VM within a parent hypervisor needs to shut down a child VM, also running a hypervisor. Simply issuing a poweroff command isn't sufficient, as it can leave the child hypervisor in an undefined state. The author explores ACPI shutdown methods, explaining that initiating shutdown from within the child hypervisor is the cleanest approach. However, since external intervention is sometimes necessary, the post delves into using the hypervisor's debug registers to inject a shutdown signal, ultimately mimicking the internal ACPI process. This involves navigating complexities of nested virtualization and ensuring data integrity during the shutdown sequence.

This blog post, titled "Quitting an Intel x86 Hypervisor," delves into the intricate process of gracefully shutting down a hypervisor running on an Intel x86 architecture. The author emphasizes the complexity beyond simply powering off the underlying hardware, as this would abruptly terminate the guest virtual machines (VMs) running within the hypervisor environment, leading to potential data loss and corruption. Instead, a controlled shutdown sequence is necessary, allowing the guest VMs to be properly saved or shut down before the hypervisor itself is terminated.

The post outlines several key stages involved in this orchestrated shutdown. It begins by discussing the initiation of the shutdown process, which can be triggered by various events, such as a user request or a critical system error. The hypervisor then systematically proceeds to shut down each running VM. This involves sending an ACPI shutdown signal to each guest, mimicking the process of a standard operating system shutdown. This allows the guest operating systems to perform their own shutdown procedures, saving data, closing applications, and unmounting file systems in an orderly fashion.

The author highlights the importance of handling potential issues during the VM shutdown phase, such as unresponsive guests. The hypervisor needs to incorporate mechanisms to deal with such scenarios, possibly through forced shutdowns after a timeout period, while acknowledging the risk of data loss in these situations. Furthermore, the post touches on the concept of saved states, where a VM's entire state can be preserved to disk, enabling it to be resumed later from the exact point of interruption. This offers a more robust approach compared to a standard shutdown, particularly in cases of unexpected hypervisor termination.

Once all guest VMs have been successfully shut down or saved, the hypervisor proceeds to deactivate its own components. This includes releasing allocated resources, disabling virtualization extensions on the CPU, and restoring the system to its pre-hypervisor state. The final step involves either handing control back to the underlying operating system, if one exists, or triggering a complete system power-off.

The author concludes by reiterating the complexity inherent in hypervisor shutdown procedures, contrasting it with the seemingly simple act of powering off a physical machine. The post emphasizes the crucial role of proper shutdown sequencing in ensuring data integrity and preventing corruption within the virtualized environment, ultimately underscoring the importance of a robust and well-defined shutdown process for any hypervisor implementation.

Summary of Comments ( 16 )
https://news.ycombinator.com/item?id=43448457

HN commenters generally praised the author's clear writing and technical depth. Several discussed the complexities of hypervisor development and the challenges of x86 specifically, echoing the author's points about interrupt virtualization and hardware quirks. Some offered alternative approaches to the problems described, including paravirtualization and different ways to handle interrupt remapping. A few commenters shared their own experiences wrestling with similar low-level x86 intricacies. The overall sentiment leaned towards appreciation for the author's willingness to share such detailed knowledge about a typically opaque area of software.

The Hacker News post titled "Quitting an Intel x86 Hypervisor" sparked a discussion with several interesting comments. Many of the comments revolve around the complexities and nuances of hypervisor development, especially on the x86 architecture.

One commenter highlights the difficulty of safely and cleanly shutting down a hypervisor, mentioning the need to consider the state of guest virtual machines and the potential for data loss. They emphasize the importance of carefully managing resources and ensuring a graceful exit for all involved components.

Another commenter dives into the specifics of the Intel architecture, discussing the various mechanisms and instructions involved in hypervisor operation. They point out the intricacies of handling interrupts, virtual memory, and other low-level hardware interactions.

Several commenters discuss the performance implications of hypervisors, noting that the overhead introduced by virtualization can sometimes be significant. They explore different techniques for minimizing this overhead, including hardware-assisted virtualization features and optimized hypervisor designs.

The discussion also touches upon the security aspects of hypervisors, with some commenters raising concerns about potential vulnerabilities and attack vectors. They mention the importance of robust security measures to protect both the hypervisor itself and the guest virtual machines running on it.

One compelling comment thread delves into the challenges of debugging hypervisors, given their privileged nature and close interaction with hardware. Commenters share their experiences and suggest various debugging strategies, including specialized tools and techniques.

Another interesting comment chain explores the different use cases for hypervisors, ranging from cloud computing and server virtualization to embedded systems and security-sensitive applications. Commenters discuss the trade-offs involved in choosing a particular hypervisor and the importance of selecting the right tool for the job.

Overall, the comments on the Hacker News post provide valuable insights into the world of x86 hypervisor development. They showcase the complexities, challenges, and opportunities associated with this technology, offering a glimpse into the intricate workings of these essential software components.

A Tale of Four Kernels [pdf] (2008)

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Posted: 2025-03-18 20:25:27

"A Tale of Four Kernels" examines the performance characteristics of four different operating system microkernels: Mach, Chorus, Windows NT, and L4. The paper argues that microkernels, despite their theoretical advantages in modularity and flexibility, have historically underperformed monolithic kernels due to high inter-process communication (IPC) costs. Through detailed measurements and analysis, the authors demonstrate that while Mach and Chorus suffer significantly from IPC overhead, L4's highly optimized IPC mechanisms allow it to achieve performance comparable to monolithic systems. The study reveals that careful design and implementation of IPC primitives are crucial for realizing the potential of microkernel architectures, with L4 showcasing a viable path towards efficient and flexible OS structures. Windows NT, despite being marketed as a microkernel, is shown to have a hybrid structure closer to a monolithic kernel, sidestepping the IPC bottleneck but also foregoing the modularity benefits of a true microkernel.

The 2008 paper "A Tale of Four Kernels" by Andreas Moshovos, Gokhan Memik, and Babak Falsafi delves into the complex world of memory access patterns within multi-core processors, specifically focusing on the challenges and opportunities presented by shared last-level caches. The authors meticulously dissect the performance implications of different kernel designs within the context of multi-core systems, arguing that traditional single-core optimized kernels can significantly underperform in multi-core environments due to increased contention for shared resources, particularly the last-level cache.

The paper introduces four distinct kernel implementations for a core computational task: matrix multiplication. These kernels are not merely variations in coding style, but represent fundamentally different approaches to data access and manipulation within the memory hierarchy. The "naive" kernel, designed with a single-core mindset, serves as a baseline for comparison, showcasing the potential pitfalls of ignoring multi-core considerations. The "blocked" kernel introduces the concept of data blocking to improve cache locality, reducing the frequency of costly cache misses. The "recursive" kernel leverages a divide-and-conquer strategy to further refine data access patterns and minimize cache pollution. Finally, the "tiled" kernel represents a sophisticated approach that combines the benefits of blocking and recursion, aiming for optimal cache utilization within the multi-core environment.

The authors conduct a rigorous experimental evaluation of these kernels across a range of multi-core architectures and configurations, utilizing detailed simulations to capture the intricate interplay between kernel behavior and cache performance. Their findings highlight the significant performance gains achievable through careful kernel design. The naive kernel, predictably, suffers from severe performance degradation as the number of cores increases, demonstrating the limitations of single-core optimization in a multi-core world. The blocked, recursive, and tiled kernels progressively improve performance by minimizing cache misses and reducing contention for shared cache lines. The tiled kernel, in particular, exhibits remarkable scalability, achieving near-linear speedup with increasing core counts, showcasing the effectiveness of its sophisticated data access strategy.

Beyond simply presenting performance results, the paper offers valuable insights into the design principles underlying efficient multi-core kernels. It emphasizes the importance of considering cache behavior and inter-core communication patterns when developing kernels for multi-core processors. The authors argue that optimizing for single-core performance can be detrimental in multi-core systems and advocate for a holistic design approach that considers the shared resources and potential contention points. The study’s findings underscore the crucial role of data locality and efficient cache utilization in achieving optimal performance in multi-core environments, paving the way for future research and development in multi-core kernel design. The paper ultimately concludes that developers must move beyond traditional single-core optimizations and embrace new strategies tailored specifically for the complexities of multi-core architectures.

Summary of Comments ( 5 )
https://news.ycombinator.com/item?id=43404617

Hacker News users discuss the practical implications and historical context of the "Four Kernels" paper. Several commenters highlight the paper's effectiveness in teaching OS fundamentals, particularly for those new to the subject. The simplicity of the kernels, along with the provided code, allows for easy comprehension and experimentation. Some discuss how valuable this approach is compared to diving straight into a complex kernel like Linux. Others point out that while pedagogically useful, these simplified kernels lack the complexities of real-world operating systems, such as memory management and device drivers. The historical significance of MINIX 3 is also touched upon, with one commenter mentioning Tanenbaum's involvement and the influence of these kernels on educational materials. The overall sentiment is that the paper is a valuable resource for learning OS basics.

The Hacker News post titled "A Tale of Four Kernels [pdf] (2008)" linking to a paper comparing microkernels has a modest number of comments, primarily focusing on the practicality and performance implications of microkernels.

One commenter highlights the historical context of the paper, mentioning that it was written during a time when multicore systems were becoming prevalent, leading to renewed interest in microkernels due to their potential advantages in terms of isolation and modularity. They also point out the paper's focus on the perceived performance disadvantages of microkernels, which had often been cited as a major drawback.

Another commenter discusses the "L4 is a fast path" concept, explaining that while Mach (a microkernel system) incurred significant overhead for inter-process communication, L4 aimed to optimize this by making the common case extremely fast. This optimization involved streamlining the message-passing mechanism and minimizing context switching overhead.

A further comment elaborates on the performance trade-offs of microkernels, acknowledging the inherent overhead of message passing but arguing that careful design and optimization can mitigate this significantly. They suggest that the benefits of microkernels, such as improved security and reliability, can outweigh the performance costs in certain applications.

One commenter notes the difficulty in achieving ideal performance with microkernels, especially when dealing with shared memory. They point to the challenges of managing memory access and maintaining consistency across different components of the system.

A user mentions seL4, a formally verified microkernel, as a significant advancement in the field. They explain that formal verification provides strong guarantees about the correctness of the kernel, potentially leading to improved security and reliability.

Finally, a commenter highlights the historical preference for monolithic kernels in widely adopted operating systems like Windows, macOS, and Linux, attributing this to their perceived simplicity and performance advantages. They suggest that the complexities of microkernel design and implementation have hindered their widespread adoption.

In summary, the comments on the Hacker News post revolve around the trade-offs between performance and other desirable characteristics like security and modularity in microkernels, highlighting the ongoing discussion and advancements in microkernel design and the challenges they face in competing with established monolithic kernels.

History of Null Pointer Dereferences on macOS

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Posted: 2025-03-17 13:11:23

macOS historically handled null pointer dereferences by trapping them, leading to immediate application crashes. This was achieved by mapping the first page of virtual memory to an inaccessible region. Over time, increasing demands for performance, especially from Java, prompted Apple to introduce "guarded pages" in macOS 10.7 (Lion). This optimization allowed for a small window of usable memory at address zero, improving performance for frequently checked null references but introducing the risk of silent memory corruption if a true null pointer dereference occurred. While efforts were made to mitigate these risks, the behavior shifted again in macOS 12 (Monterey) and later ARM-based systems, where the entire page at zero became usable. This means null pointer dereferences now consistently result in memory corruption, potentially leading to more difficult-to-debug issues.

The blog post "History of Null Pointer Dereferences on macOS" by Ariadne Fine details the evolution of how macOS (and its predecessor, NeXTSTEP) handles attempts to dereference null pointers. The author meticulously chronicles the changes across different versions of the operating system, highlighting the motivations and consequences of each modification.

Initially, in the early days of NeXTSTEP, dereferencing a null pointer consistently resulted in a crash. This behavior, while predictable, was not always desirable for developers. The article explains that this strict enforcement stemmed from the Mach microkernel underpinning NeXTSTEP, where accessing address zero was a guaranteed fault.

As NeXTSTEP evolved into macOS, Apple introduced a mitigation strategy known as "zero page mapping." This technique involved mapping the first page of virtual memory (starting at address zero) to a read-only page filled with zeros. Consequently, attempts to dereference a null pointer would no longer immediately crash but would instead return a zero value for reads. Writes to a null pointer would still trigger a crash. This change provided a degree of backward compatibility and fault tolerance for older applications that might inadvertently dereference null pointers, offering a softer failure mode in some cases.

The blog post further elaborates on the nuances of zero page mapping. It explains that while this mechanism provided a measure of resilience, it also introduced potential security vulnerabilities. Attackers could exploit the predictable zeroed-out data for malicious purposes. Consequently, Apple introduced further refinements to the system.

One crucial enhancement was the introduction of guard pages. These are strategically placed non-accessible pages surrounding the zero page. Accessing memory within these guard pages would immediately trigger a crash. This fortified the system against exploits that might attempt to access memory adjacent to the zero page.

Over time, Apple continued to refine the behavior. Motivated by security concerns and the desire to adhere to POSIX standards, macOS later moved away from zero page mapping for user-space applications. The article notes that for modern 64-bit processes, dereferencing a null pointer typically results in a segmentation fault, aligning macOS behavior with the more standard Unix-like approach. However, the zero page mapping mechanism persists for 32-bit processes for backward compatibility, although with stricter enforcement and smaller page sizes to reduce the potential attack surface.

The post concludes by emphasizing that the handling of null pointer dereferences on macOS has been a dynamic journey, shaped by a complex interplay of performance considerations, security vulnerabilities, backward compatibility, and evolving industry standards. This evolution has led to a more robust and secure system, albeit one with a nuanced history. The detailed account provides valuable insight into the underlying mechanics of memory management within macOS.

Summary of Comments ( 8 )
https://news.ycombinator.com/item?id=43388218

Hacker News users discussed the nuances of null pointer dereferences on macOS and other systems. Some highlighted that the behavior described (where dereferencing a NULL pointer doesn't always crash) isn't unique to macOS and stems from virtual memory page zero being unmapped. Others pointed out the security implications, particularly in the kernel, where such behavior could be exploited. Several commenters mentioned the trade-off between debugging ease (catching null pointer dereferences early) and performance (the overhead of checking for null every time). The history of this design choice and its evolution in different macOS versions was also a topic of conversation, along with comparisons to other operating systems' handling of null pointers. One commenter noted the irony of Apple moving away from this behavior, as it was initially designed to make things less crashy. The utility of tools like scribble for catching such errors was also mentioned.

The Hacker News post titled "History of Null Pointer Dereferences on macOS" (https://news.ycombinator.com/item?id=43388218) has generated a modest number of comments, offering various perspectives on the topic.

Several commenters discuss the technical aspects of null pointer handling in different operating systems and architectures. One commenter mentions how the behavior of dereferencing a null pointer differs between x86 and ARM, highlighting that ARM doesn't map the first page of memory, leading to a crash. They also note the historical reasons for macOS's behavior, explaining how it's a legacy from older versions of the OS and the transition from PowerPC.

Another commenter explains that mapping the zero page wasn't done on macOS for performance reasons, as it adds overhead to every memory access to check for zero-page accesses. This trade-off between performance and ease of debugging is a recurring theme.

Another thread of discussion focuses on the complexities and nuances of exploiting null pointer dereferences for security purposes. One commenter points out that if the address 0 is mapped, then dereferencing NULL can lead to arbitrary code execution in some circumstances, while if it isn't mapped (as in ARM), the result is simply a crash.

Some users reminisce about older systems where dereferencing null pointers was more predictable, simplifying debugging in certain scenarios. Others contribute by sharing anecdotal experiences and observations related to null pointer behavior in different contexts.

A couple of commenters touch on mitigation techniques, like using static analysis tools to catch potential null pointer dereferences before they cause problems.

While the number of comments isn't extensive, they provide valuable insights into the history, technical implications, and security considerations surrounding null pointer dereferences on macOS and other systems. They highlight the trade-offs involved in different design choices and offer practical perspectives from developers who have encountered these issues firsthand.

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