This post explores integrating Rust into a Java project for performance-critical components using JNI. It details a practical example of optimizing a data serialization task, demonstrating significant speed improvements by leveraging Rust's efficiency and memory safety. The article walks through the process of creating a Rust library, exposing functions via JNI, and integrating it into the Java application. It acknowledges the added complexity of JNI but emphasizes the substantial performance gains as justification, particularly for CPU-bound operations. Finally, the author recommends careful consideration of the trade-offs between complexity and performance when deciding whether to adopt this hybrid approach.
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.
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.
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.
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.
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.
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.
Combining Tokio's asynchronous runtime with prctl(PR_SET_PDEATHSIG) in a multi-threaded Rust application can lead to a subtle and difficult-to-debug issue. PR_SET_PDEATHSIG causes a signal to be sent to a child process when its parent terminates. If a thread in a Tokio runtime calls prctl to set this signal and then that thread's parent exits, the signal can be delivered to a different thread within the runtime, potentially one that is unprepared to handle it and is holding critical resources. This can result in resource leaks, deadlocks, or panics, as the unexpected signal disrupts the normal flow of the asynchronous operations. The blog post details a specific scenario where this occurred and provides guidance on avoiding such issues, emphasizing the importance of carefully considering signal handling when mixing Tokio with prctl.
The Hacker News comments discuss the surprising interaction between Tokio and prctl(PR_SET_PDEATHSIG). Several commenters express surprise at the behavior, noting that it's non-intuitive and potentially dangerous for multi-threaded programs using Tokio. Some point out the complexities of signal handling in general, and the specific challenges when combined with asynchronous runtimes. One commenter highlights the importance of understanding the underlying system calls and their implications, especially when mixing different programming paradigms. The discussion also touches on the difficulty of debugging such issues and the lack of clear documentation or warnings about this particular interaction. A few commenters suggest potential workarounds or mitigations, including avoiding PR_SET_PDEATHSIG altogether in Tokio-based applications. Overall, the comments underscore the subtle complexities that can arise when combining asynchronous programming with low-level system calls.
The blog post argues for a standardized, cross-platform OS API specifically designed for timers. Existing timer mechanisms, like POSIX's timerfd and Windows' CreateWaitableTimer, while useful, differ significantly across operating systems, complicating cross-platform development. The author proposes a new API with a consistent interface that abstracts away these platform-specific details. This ideal API would allow developers to create, arm, and disarm timers, specifying absolute or relative deadlines with optional periodic behavior, all while handling potential issues like early wake-ups gracefully. This would simplify codebases and improve portability for applications relying on precise timing across different operating systems.
The Hacker News comments discuss the complexities of cross-platform timer APIs, largely agreeing with the article's premise. Several commenters highlight the difficulties introduced by different operating systems' power management features, impacting timer accuracy and reliability. Specific challenges like signal coalescing and the lack of a unified interface for monotonic timers are mentioned. Some propose workarounds like busy-waiting for short durations or using platform-specific code for optimal performance. The need for a standardized API is reiterated, with suggestions for what such an API should offer, including considerations for power efficiency and different timer resolutions. One commenter points to the challenges of abstracting away hardware differences completely, suggesting the ideal solution may involve a combination of OS-level improvements and application-specific strategies.
This blog post explores using NetBSD's native graphics capabilities without relying on the X Window System (X11). The author demonstrates direct framebuffer access using libraries like wscons and libcaca for simple graphics and text output, highlighting the performance benefits and reduced complexity compared to a full X11 setup. This approach is particularly advantageous for embedded or resource-constrained systems, or situations where a minimal graphical interface suffices. The post details setting up a NetBSD virtual machine, configuring wscons, and provides code examples using libcaca to draw shapes and text directly to the screen, showcasing the simplicity and directness of this method.
HN commenters largely praised the elegance and simplicity of NetBSD's native graphics stack, contrasting it favorably with the complexity of X11. Several pointed out the historical context, noting that this approach harkens back to simpler times and offers a refreshing alternative to the bloat of modern desktop environments. Some expressed interest in exploring NetBSD specifically because of this feature. A few commenters questioned the practicality for everyday use, citing the limited software ecosystem that supports it. Others discussed the performance implications, with some suggesting it could be faster than X11 in certain scenarios. There was also discussion of similar approaches in other operating systems, such as Framebuffer and Wayland.
This project introduces a C-based web framework designed for dynamic module loading and hot reloading. Leveraging a custom module format and a simple HTTP server, it allows developers to modify and reload C code without restarting the server, facilitating rapid development and experimentation. The framework compiles and links modules on-the-fly, managing dependencies and updating the running server seamlessly. While currently limited in features, it aims to offer a performant and flexible foundation for building web applications directly in C.
Hacker News users discussed the practicality and novelty of a C web framework with hot reloading. Some questioned the real-world use cases and performance benefits compared to existing solutions, suggesting the project serves more as an interesting experiment than a production-ready tool. Others expressed interest in the technical implementation, particularly the hot reloading aspect, and appreciated the author's effort in exploring this concept. Several users pointed out potential issues like memory leaks and the challenges of safely reloading C code in a web server environment. The overall sentiment leans towards acknowledging the project's technical ingenuity while remaining skeptical about its broad applicability.
Summary of Comments ( 32 )
https://news.ycombinator.com/item?id=43991221
Hacker News users generally expressed interest in the potential of Rust for performance-critical sections of Java applications. Several commenters pointed out that JNI comes with overhead, advising caution and profiling to ensure actual performance gains. Some shared alternative approaches like JNA and GraalVM's native image for simpler integration. Others discussed the complexities of memory management and exception handling across the language boundary, emphasizing the importance of careful design. A few users also mentioned existing projects using Rust with Java, indicating growing real-world adoption of this approach. One compelling comment highlighted that while the appeal of Rust is performance, maintainability should also be a primary consideration, especially given the added complexity of cross-language integration. Another pointed out the potential for data corruption if Rust code modifies Java-managed objects without proper synchronization.
The Hacker News post "Lessons from Mixing Rust and Java: Fast, Safe, and Practical" linking to a Medium article about integrating Rust into Java projects using JNI generated a moderate discussion with several insightful comments.
Several commenters discussed the complexities and performance implications of JNI. One user pointed out the overhead associated with JNI calls, especially for smaller operations, suggesting that it's crucial to benchmark and profile to ensure performance gains outweigh the overhead. They emphasized that JNI isn't a magic bullet and its effectiveness depends heavily on the specific use case. Another commenter echoed this sentiment, cautioning against premature optimization and advising careful consideration of whether the performance benefits justify the added complexity of JNI.
Another thread focused on alternatives to JNI, such as using message queues like Kafka or RabbitMQ for inter-process communication. This approach, while potentially introducing latency, offers better isolation and fault tolerance, particularly beneficial in distributed systems. This suggestion sparked a discussion about the trade-offs between performance and complexity when choosing between JNI and inter-process communication.
Some users shared their personal experiences with Rust and Java integration. One commenter mentioned using Rust for performance-critical sections of a Java application and achieving significant improvements, while another highlighted the challenges of managing memory and ensuring thread safety when working with JNI. They discussed the importance of understanding the memory models of both languages to avoid common pitfalls.
The discussion also touched upon the tooling and ecosystem surrounding Rust and Java integration. Commenters mentioned tools like JNA and SWIG as alternatives to hand-written JNI code, highlighting their ease of use but also potential performance limitations.
Finally, a few commenters expressed their enthusiasm for the combination of Rust and Java, praising Rust's performance and safety features while acknowledging the complexities of integrating the two languages. They emphasized the importance of careful design and thorough testing to ensure a successful integration.