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.
This blog post explores the architecture and evolution of Darwin, Apple's open-source operating system foundation, and its XNU kernel. It explains how Darwin, built upon the Mach microkernel, incorporates components from BSD and Apple's own I/O Kit. The post details the hybrid kernel approach of XNU, combining the message-passing benefits of a microkernel with the performance advantages of a monolithic kernel. It discusses key XNU subsystems like the process manager, memory manager, file system, and networking stack, highlighting the interplay between Mach and BSD layers. The post also traces Darwin's history, from its NeXTSTEP origins through its evolution into macOS, iOS, watchOS, and tvOS, emphasizing the platform's adaptability and performance.
Hacker News users generally praised the article for its clarity and depth in explaining a complex topic. Several commenters with kernel development experience validated the information presented, noting its accuracy and helpfulness for understanding the evolution of XNU. Some discussion arose around specific architectural choices made by Apple, including the Mach microkernel and its interaction with the BSD environment. One commenter highlighted the performance benefits of the hybrid kernel approach, while others expressed interest in the challenges of maintaining such a system. A few users also pointed out areas where the article could be expanded, such as delving further into I/O Kit details and exploring the security implications of the XNU architecture.
The Linux Kernel Defence Map provides a comprehensive overview of security hardening mechanisms available within the Linux kernel. It categorizes these techniques into areas like memory management, access control, and exploit mitigation, visually mapping them to specific kernel subsystems and features. The map serves as a resource for understanding how various kernel configurations and security modules contribute to a robust and secure system, aiding in both defensive hardening and vulnerability research by illustrating the relationships between different protection layers. It aims to offer a practical guide for navigating the complex landscape of Linux kernel security.
Hacker News users generally praised the Linux Kernel Defence Map for its comprehensiveness and visual clarity. Several commenters pointed out its value for both learning and as a quick reference for experienced kernel developers. Some suggested improvements, including adding more details on specific mitigations, expanding coverage to areas like user namespaces and eBPF, and potentially creating an interactive version. A few users discussed the project's scope, questioning the inclusion of certain features and debating the effectiveness of some mitigations. There was also a short discussion comparing the map to other security resources.
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.
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.
Linux kernel 6.14 delivers significant performance improvements and enhanced Windows compatibility. Key advancements include faster initial setup times, optimized memory management reducing overhead, and improvements to the EXT4 filesystem, boosting I/O performance for everyday tasks. Better support for running Windows games through Proton and Steam Play, stemming from enhanced Direct3 12 support, and improved performance with Windows Subsystem for Linux (WSL2) make gaming and cross-platform development smoother. Initial benchmarks show impressive results, particularly for AMD systems. This release signals a notable step forward for Linux in both performance and its ability to seamlessly integrate with Windows environments.
Hacker News commenters generally express skepticism towards ZDNet's claim of a "big leap forward." Several point out that the article lacks specific benchmarks or evidence to support the performance improvement claims, especially regarding gaming. Some suggest the improvements, while present, are likely incremental and specific to certain hardware or workloads, not a universal boost. Others discuss the ongoing development of mainline Windows drivers for Linux, particularly for newer hardware, and the complexities surrounding secure boot. A few commenters mention specific improvements they appreciate, such as the inclusion of the "rusty-rng" random number generator and enhancements for RISC-V architecture. The overall sentiment is one of cautious optimism tempered by a desire for more concrete data.
The seL4 microkernel is a highly secure and reliable operating system foundation, formally verified to guarantee functional correctness and security properties. This verification proves that the implementation adheres to its specification, encompassing properties like data integrity and control-flow integrity. Designed for high-performance and real-time embedded systems, seL4's small size and minimal interface facilitate formal analysis and predictable resource usage. Its strong isolation mechanisms enable the construction of robust systems where different components with varying levels of trust can coexist securely, preventing failures in one component from affecting others. The kernel's open-source nature and liberal licensing promote transparency and wider adoption, fostering further research and development in secure systems.
Hacker News users discussed the seL4 microkernel, focusing on its formal verification and practical applications. Some questioned the real-world impact of the verification, highlighting the potential for vulnerabilities outside the kernel's scope, such as in device drivers or user-space applications. Others praised the project's rigor and considered it a significant achievement in system software. Several comments mentioned the challenges of using microkernels effectively, including the performance overhead of inter-process communication (IPC). Some users also pointed out the limited adoption of microkernels in general, despite their theoretical advantages. There was also interest in seL4's use in specific applications like autonomous vehicles and aerospace.
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.
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.
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.
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.
Landrun is a tool that utilizes the Landlock Linux Security Module (LSM) to sandbox processes without requiring root privileges or containers. It allows users to define fine-grained access control rules for a target process, restricting its access to the filesystem, network, and other resources. By leveraging Landlock's unprivileged mode and a clever bootstrapping process involving temporary filesystems, Landrun simplifies sandbox setup and makes robust sandboxing accessible to regular users. This enables easier and more secure execution of potentially untrusted code, contributing to a more secure desktop environment.
HN commenters generally praise Landrun for its innovative approach to sandboxing, making it easier than traditional methods like containers or VMs. Several highlight the significance of using Landlock LSM for security, noting its kernel-level enforcement as a robust mechanism. Some discuss potential use cases, including sandboxing web browsers and other potentially risky applications. A few express concerns about complexity and debugging challenges, while others point out the project's early stage and potential for improvement. The user-friendliness compared to other sandboxing techniques is a recurring theme, with commenters appreciating the streamlined process. Some also discuss potential integrations and extensions, such as combining Landrun with Firejail.
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.
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.
Scorpi is a new, open-source type-1 hypervisor designed specifically for macOS on Apple silicon. It aims to be a modern, lightweight, and performant alternative to existing solutions. Leveraging the virtualization capabilities of Apple silicon, Scorpi provides a minimal kernel responsible solely for virtualization while offloading other tasks to a dedicated "service VM." This approach prioritizes performance and security by reducing the hypervisor's attack surface. Scorpi also offers a flexible device model for efficient peripheral access and a streamlined user experience. While still in active development, it promises a compelling new option for running virtual machines on macOS.
HN commenters generally expressed excitement about Scorpi, praising its clean design and potential for macOS virtualization. Several highlighted the difficulty of macOS virtualization in the past and saw Scorpi as a promising new approach. Some questioned the performance compared to existing solutions like UTM, and others were curious about specific features like nested virtualization and GPU passthrough. A few commenters with virtualization experience offered technical insights, discussing the challenges of implementing certain features and suggesting potential improvements. The project's open-source nature and reliance on Apple's Hypervisor.framework were also points of interest. Overall, the comments reflected a cautiously optimistic view of Scorpi's potential to simplify and improve macOS virtualization.
LWN.net's "The early days of Linux (2023)" revisits Linux's origins through the lens of newly rediscovered email archives from 1992. These emails reveal the collaborative, yet sometimes contentious, environment surrounding the project's infancy. They highlight Linus Torvalds's central role, the rapid evolution of the kernel, and early discussions about licensing, portability, and features. The article underscores how open collaboration, despite its challenges, fueled Linux's early growth and laid the groundwork for its future success. The rediscovered archive offers valuable historical insight into the project's formative period and provides a more complete understanding of its development.
HN commenters discuss Linus Torvalds' early approach to Linux development, contrasting it with the more structured, corporate-driven development of today. Several highlight his initial dismissal of formal specifications, preferring a "code first, ask questions later" method guided by user feedback and rapid iteration. This organic approach, some argue, fostered innovation and rapid growth in Linux's early stages, while others note its limitations as the project matured. The discussion also touches on Torvalds' personality, described as both brilliant and abrasive, and how his strong opinions shaped the project's direction. A few comments express nostalgia for the simpler times of early open-source development, contrasting it with the complexities of modern software engineering.
A recent Linux kernel change inadvertently broke eBPF programs relying on PT_REGS_RC(regs). Intended to optimize register access for x86, this change accidentally cleared the return value register before eBPF programs using kprobe and kretprobe could access it. This resulted in eBPF tools like bpftrace and bcc showing garbage data instead of expected return values. The issue primarily affects x86 systems running kernel versions 6.5 and later and has already been fixed in 6.5.1, 6.4.12, and 6.1.38. Users of affected kernels should update to receive the fix.
The Hacker News comments discuss the complexities and nuances of the issue presented in the article about pt_regs returning garbage in recent Linux kernels due to changes introduced by "Fred." Several commenters express sympathy for Fred, highlighting the challenging trade-offs inherent in kernel development, especially when balancing performance optimizations with backward compatibility. Some point out the difficulties of maintaining eBPF programs across kernel versions and the lack of clear documentation or warnings about these breaking changes. Others delve into the technical specifics, discussing register context, stack unwinding, and the implications for debuggers and profiling tools. The overall sentiment seems to be one of acknowledging the difficulty of the situation and the need for better communication and tooling to navigate such kernel-level changes. A few users also suggest potential workarounds and debugging strategies.
The author experienced extraordinarily high CPU utilization (3200%) on their Linux system, far exceeding the expected maximum for their 8-core processor. After extensive troubleshooting, including analyzing process lists, checking for kernel issues, and verifying hardware performance, the culprit was identified as a bug in the docker stats command itself. The command was incorrectly multiplying the CPU utilization by the number of CPUs, leading to the inflated and misleading percentage. Once the issue was pinpointed, the author switched to a more reliable monitoring tool, htop, which accurately reported normal CPU usage. This highlighted the importance of verifying monitoring tool accuracy when encountering unusual system behavior.
Hacker News users discussed the plausibility and implications of 3200% CPU utilization, referencing the original author's use of Web Workers and the browser's ability to utilize multiple threads. Some questioned if this was a true representation of CPU usage or simply a misinterpretation of metrics, suggesting that the number reflects total CPU time consumed across all cores rather than a percentage exceeding 100%. Others pointed out that using performance.now() instead of Date.now() for benchmarks is crucial for accuracy, especially with Web Workers, and speculated on the specific workload and hardware involved. The unusual percentage sparked conversation about the potential for misleading performance measurements and the nuances of interpreting CPU utilization in multi-threaded environments like browsers. Several commenters highlighted the difference between wall-clock time and CPU time, emphasizing that the former is often the more relevant metric for user experience.
Greg Kroah-Hartman's post argues that new drivers and kernel modules being written in Rust benefit the entire Linux kernel community. He emphasizes that Rust's memory safety features improve overall kernel stability and security, reducing potential bugs and vulnerabilities for everyone, even those not directly involved with Rust code. This advantage outweighs any perceived downsides like increased code complexity or a steeper learning curve for some developers. The improved safety and resulting stability ultimately reduces maintenance burden and allows developers to focus on new features instead of bug fixes, benefiting the entire ecosystem.
HN commenters largely agree with Greg KH's assessment of Rust's benefits for the kernel. Several highlight the improved memory safety and the potential for catching bugs early in the development process as significant advantages. Some express excitement about the prospect of new drivers and filesystems written in Rust, while others acknowledge the learning curve for kernel developers. A few commenters raise concerns, including the increased complexity of debugging Rust code in the kernel and the potential performance overhead. One commenter questions the long-term maintenance implications of introducing a new language, wondering if it might exacerbate the already challenging task of maintaining the kernel. Another suggests that the real win will be determined by whether Rust truly reduces the number of CVEs related to memory safety issues in the long run.
The author experienced system hangs on wake-up with their AMD GPU on Linux. They traced the issue to the AMDGPU driver's handling of the PCIe link and power states during suspend and resume. Specifically, the driver was prematurely powering off the GPU before the system had fully suspended, leading to a deadlock. By patching the driver to ensure the GPU remained powered on until the system was fully asleep, and then properly re-initializing it upon waking, they resolved the hanging issue. This fix has since been incorporated upstream into the official Linux kernel.
Commenters on Hacker News largely praised the author's work in debugging and fixing the AMD GPU sleep/wake hang issue. Several expressed having experienced this frustrating problem themselves, highlighting the real-world impact of the fix. Some discussed the complexities of debugging kernel issues and driver interactions, commending the author's persistence and systematic approach. A few commenters also inquired about specific configurations and potential remaining edge cases, while others offered additional technical insights and potential avenues for further improvement or investigation, such as exploring runtime power management. The overall sentiment reflects appreciation for the author's contribution to improving the Linux AMD GPU experience.
The blog post details troubleshooting high CPU usage attributed to the writeback process in a Linux kernel. After initial investigations pointed towards cgroups and specifically the cpu.cfs_period_us parameter, the author traced the issue to a tight loop within the cgroup writeback mechanism. This loop was triggered by a large number of cgroups combined with a specific workload pattern. Ultimately, increasing the dirty_expire_centisecs kernel parameter, which controls how long dirty data stays in memory before being written to disk, provided the solution by significantly reducing the writeback activity and lowering CPU usage.
Commenters on Hacker News largely discuss practical troubleshooting steps and potential causes of the high CPU usage related to cgroups writeback described in the linked blog post. Several suggest using tools like perf to profile the kernel and pinpoint the exact function causing the issue. Some discuss potential problems with the storage layer, like slow I/O or a misconfigured RAID, while others consider the possibility of a kernel bug or an interaction with specific hardware or drivers. One commenter shares a similar experience with NFS and high CPU usage related to writeback, suggesting a potential commonality in networked filesystems. Several users emphasize the importance of systematic debugging and isolation of the problem, starting with simpler checks before diving into complex kernel analysis.
Colinux allows running Linux applications on a Windows system without the need for a virtual machine. It achieves this by running the Linux kernel as a single, large, cooperative Windows process. This process manages its own memory and handles Linux system calls, effectively creating a contained Linux environment within Windows. User-mode Linux applications then run within this environment, interacting with the Windows host only through a specialized filesystem driver and networking layer provided by Colinux. This approach offers performance advantages over traditional virtualization by minimizing the overhead associated with hardware emulation.
HN users discuss Colinux, focusing on its unique approach of running Linux within a single Windows process, contrasting it with virtual machines and WSL. Several express interest in its lightweight nature and potential performance benefits, especially for resource-constrained environments or specific use-cases like embedded systems. Some question its practicality compared to more established solutions like Docker or WSL, while others highlight the security implications of running a full kernel within a single process. The lack of recent updates to the project is also a recurring concern, leading to speculation about its current status and maintainability. The ingenuity of the approach is generally acknowledged, even if its practical application remains a point of debate.
This blog post details creating a basic Windows driver using Rust. It leverages the windows crate for Windows API bindings and the wdk-sys crate for lower-level WDK access. The driver implements a minimal "DispatchCreateClose" routine, handling device creation and closure. The post walks through setting up the Rust development environment, including Cargo configuration and build process adjustments for driver compilation. It highlights using the wdk-build crate for simplifying the build process and generating the necessary INF file for driver installation. Finally, it demonstrates loading and unloading the driver using the DevCon utility, providing a practical example of the entire workflow from development to deployment.
Hacker News users discussed the challenges and advantages of writing Windows drivers in Rust. Several commenters pointed out the difficulty of working with the Windows Driver Kit (WDK) and its C/C++ focus, contrasting it with Rust's memory safety and modern tooling. Some highlighted the potential for improved driver stability and security with Rust. The conversation also touched on existing Rust wrappers for the WDK, the maturity of Rust driver development, and the complexities of interrupt handling. One user questioned the overall benefit, arguing that the difficulty of writing drivers stems from inherent hardware complexities more than language choice. Another pointed out the limited use of high-level languages in kernel-mode drivers due to real-time constraints.
Andrew Tanenbaum, creator of MINIX, argued in 1992 that Linux, being a monolithic kernel, represented an outdated design compared to the microkernel approach of MINIX. He believed that microkernels, with their modularity and message-passing architecture, offered superior portability, maintainability, and reliability, especially as technology moved towards distributed systems and multicore processors. Tanenbaum predicted that Linux, tied to the aging Intel 386 architecture, would soon become obsolete and fade away as more advanced hardware and software paradigms emerged. He emphasized the conceptual superiority of MINIX's design, portraying Linux as a step backwards in operating system development.
HN commenters largely dismiss the linked 1992 post arguing for Minix over Linux. Many point out that the author's predictions about Linux's limitations due to its monolithic kernel and lack of microkernel structure were inaccurate, given Linux's widespread success and ongoing development. Some acknowledge that microkernels have certain advantages, but suggest that Linux's approach has proven more practical and adaptable. A few commenters find the historical perspective interesting, noting how the computing landscape has changed significantly since 1992, rendering the arguments largely irrelevant in the modern context. One commenter sarcastically celebrates Tanenbaum's foresight.
Hector Martin, the lead developer of the Asahi Linux project which brings Linux support to Apple Silicon Macs, has stepped down from his role as a Linux kernel developer. Citing burnout and frustration with the kernel development process, particularly regarding code review and the treatment of new contributors, Martin explained that maintaining both Asahi Linux and actively contributing to the kernel has become unsustainable. He intends to remain involved with Asahi Linux and will continue working on the project, but will no longer be directly involved in core kernel development or reviews. He hopes this change will allow him to focus on higher-level aspects of the project and improve the experience for other Asahi Linux developers.
Several Hacker News commenters expressed surprise and sadness at Hector Martin's resignation, acknowledging his significant contributions to the Asahi Linux project and the broader Linux community. Some speculated about the reasons behind his departure, citing burnout, frustration with kernel development processes, or potential new opportunities. Others discussed the implications for the future of Asahi Linux, with some expressing concern about the project's trajectory without Martin's leadership, while others remained optimistic about the strong community he fostered. A few commenters questioned the overall tone of Martin's resignation email, finding it overly critical of the Linux kernel community. Finally, some users shared personal anecdotes of interacting with Martin, praising his technical skills and helpfulness.
Uscope is a new, from-scratch debugger for Linux written in C and Python. It aims to be a modern, user-friendly alternative to GDB, boasting a simpler, more intuitive command language and interface. Key features include reverse debugging capabilities, a TUI interface with mouse support, and integration with Python scripting for extended functionality. The project is currently under active development and welcomes contributions.
Hacker News users generally expressed interest in Uscope, praising its clean UI and the ambition of building a debugger from scratch. Several commenters questioned the practical need for a new debugger given existing robust options like GDB, LLDB, and Delve, wondering about Uscope's potential advantages. Some discussed the challenges of debugger development, highlighting the complexities of DWARF parsing and platform compatibility. A few users suggested integrations with other tools, like REPLs, and requested features like remote debugging. The novelty of a fresh approach to debugging generated curiosity, but skepticism regarding long-term viability and differentiation also emerged. Some expressed concerns about feature parity with existing debuggers and the sustainability of the project.
Chimera Linux is focusing on simplicity and performance in its desktop environment. The project uses a custom-built desktop built on Wayland, emphasizing minimal dependencies and a streamlined experience. This includes a basic compositor called Chimera-wm, along with self-developed components like a file manager and terminal emulator, to minimize bloat and maintain a tight control over the user experience. While still under heavy development, the project aims to provide a fast, clean, and easily adaptable desktop environment built from the ground up.
HN commenters generally express interest in Chimera Linux's approach of using a modern init system and focusing on a straightforward desktop experience. Some praise its potential for stability and performance by sticking with known-good components. Others are skeptical of its niche appeal, questioning whether simplifying the desktop is a significant enough draw. A few commenters raise concerns about the sustainability of a project reliant on a single developer, while others commend the developer's clear vision and execution. The discussion also touches on the limitations of systemd and the challenges of balancing minimalism with user expectations. Some express hope for Chimera becoming a viable alternative to established distributions.
A vulnerability (CVE-2024-54507) was discovered in the XNU kernel, affecting macOS and iOS, which allows malicious actors to leak kernel memory. The flaw resides in the sysctl interface, specifically the kern.hv_vmm_vcpu_state handler. This handler failed to properly validate the size of the buffer provided by the user, resulting in an out-of-bounds read. By crafting a request with a larger buffer than expected, an attacker could read data beyond the intended memory region, potentially exposing sensitive kernel information. This vulnerability was patched by Apple in October 2024 and is relatively simple to exploit.
Hacker News commenters discuss the CVE-2024-54507 vulnerability, focusing on the unusual nature of the vulnerable sysctl and the potential implications. Several express surprise at the existence of a sysctl that directly modifies kernel memory, questioning why such a mechanism exists and speculating about its intended purpose. Some highlight the severity of the vulnerability, emphasizing the ease of exploitation and the potential for privilege escalation. Others note the fortunate aspect of the bug manifesting as a kernel panic rather than silent memory corruption, making detection easier. The limited practical impact due to System Integrity Protection (SIP) is also mentioned, alongside the difficulty of exploiting the vulnerability remotely. A few commenters also delve into the technical details of the exploit, discussing the specific memory manipulation involved and the resulting kernel crash. The overall sentiment reflects concern about the unusual nature of the vulnerability and its potential implications, even with the mitigating factors.
The ROCm Device Support Wishlist GitHub discussion serves as a central hub for users to request and discuss support for new AMD GPUs and other hardware within the ROCm platform. It encourages users to upvote existing requests or submit new ones with detailed system information, emphasizing driver versions and specific models for clarity and to gauge community interest. The goal is to provide the ROCm developers with a clear picture of user demand, helping them prioritize development efforts for broader hardware compatibility.
Hacker News users discussed the ROCm device support wishlist, expressing both excitement and skepticism. Some were enthusiastic about the potential for wider AMD GPU adoption, particularly for scientific computing and AI workloads where open-source solutions are preferred. Others questioned the viability of ROCm competing with CUDA, citing concerns about software maturity, performance consistency, and developer mindshare. The need for more robust documentation and easier installation processes was a recurring theme. Several commenters shared personal experiences with ROCm, highlighting successes with specific applications but also acknowledging difficulties in getting it to work reliably across different hardware configurations. Some expressed hope for better support from AMD to broaden adoption and improve the overall ROCm ecosystem.
The author's Chumby 8, a vintage internet appliance, consistently ran at 100% CPU usage due to a kernel bug affecting the way the CPU's clock frequency was handled. The original kernel expected a constant clock speed, but the Chumby's CPU dynamically scaled its frequency. This discrepancy caused the kernel's timekeeping functions to malfunction, leading to a busy loop that consumed all available CPU cycles. Upgrading to a newer kernel, compiled with the correct configuration for a variable clock speed, resolved the issue and brought CPU usage back to normal levels.
The Hacker News comments primarily focus on the surprising complexity and challenges involved in the author's quest to upgrade the kernel of a Chumby 8. Several commenters expressed admiration for the author's deep dive into the embedded system's inner workings, with some jokingly comparing it to a software archaeological expedition. There's also discussion about the prevalence of inefficient browser implementations on embedded devices, contributing to high CPU usage. Some suggest alternative approaches, like using a lightweight browser or a different operating system entirely. A few commenters shared their own experiences with similar embedded devices and the difficulties in optimizing their performance. The overall sentiment reflects appreciation for the author's detailed troubleshooting process and the interesting technical insights it provides.
The article explores a new method for process creation using io_uring, aiming to improve efficiency and reduce overhead compared to traditional fork() and execve(). This new approach uses a "registered executable" within io_uring, allowing asynchronous process launching without the performance penalties of copying memory pages between parent and child processes. The proposed solution involves two new system calls: pidfd_spawn() and pidfd_wait(). pidfd_spawn() creates a new process from the registered executable and returns a process file descriptor, while pidfd_wait() provides an asynchronous wait mechanism using io_uring. This approach offers a streamlined process-creation pathway within the io_uring framework, potentially boosting performance for applications that frequently spawn processes, like containers or web servers.
Hacker News users discuss the implications of io_uring's new process creation capabilities. Several express excitement about the potential performance improvements, particularly for applications that frequently spawn processes, like web servers. Some highlight the security benefits of avoiding execve, while others raise concerns about the complexity introduced by this new feature and the potential for misuse. A few commenters delve into the technical details, comparing the approach to other process creation methods and discussing the trade-offs involved. Several anticipate interesting use cases, including containerization and sandboxing. One user questions if io_uring is becoming overly complex and straying from its original purpose.
iOS 18 introduces a new feature that automatically reboots devices after a prolonged period of inactivity. Reverse engineering revealed this is managed by the SpringBoard process, which monitors user interaction and triggers a reboot after approximately 72 hours of inactivity. The reboot is signaled by setting a specific flag in a system property and is considered a "soft" reboot, likely to maintain device state where possible. This feature seems primarily targeted at corporate devices enrolled in Mobile Device Management (MDM) systems, as a way to clear temporary states and potentially address performance issues resulting from prolonged uptime without requiring manual intervention. The exact conditions for triggering the reboot, beyond inactivity time, are still being investigated.
Hacker News users discussed the potential reasons behind iOS 18's automatic reboot after extended inactivity, with some speculating it's related to memory management, specifically clearing caches or resetting background processes. Others suggested it could be a security measure to mitigate potential exploits or simply a bug. A few commenters expressed concern about the reboot happening without warning, potentially interrupting ongoing tasks or data syncing. Some highlighted the lack of official documentation on this behavior and the author's reverse engineering efforts to uncover the cause. The discussion also touched on similar behavior observed in other operating systems and the overall complexity of modern OS architectures.
Summary of Comments ( 5 )
https://news.ycombinator.com/item?id=43601301
Hacker News users discussed the practicality and security implications of the
mem-isolatecrate. 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-isolatecrate) 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.