eBPF program portability can be tricky due to differences in kernel versions and configurations. The blog post highlights how seemingly minor variations, such as a missing helper function or a change in struct layout, can cause a program that works perfectly on one kernel to fail on another. It emphasizes the importance of using the bpftool utility for introspection, allowing developers to compare kernel features and identify discrepancies that might be causing compatibility issues. Additionally, building eBPF programs against the oldest supported kernel and strategically employing the LINUX_VERSION_CODE macro can enhance portability and minimize unexpected behavior across different kernel versions.
OpenBSD has contributed significantly to operating system security and development through proactive approaches. These include innovations like memory safety mitigations such as W^X (preventing simultaneous write and execute permissions on memory pages) and pledge() (restricting system calls available to a process), advanced cryptography and randomization techniques, and extensive code auditing practices. The project also champions portable and reusable code, evident in the creation of OpenSSH, OpenNTPD, and other tools, which are now widely used across various platforms. Furthermore, OpenBSD emphasizes careful documentation and user-friendly features like the package management system, highlighting a commitment to both security and usability.
Hacker News users discuss OpenBSD's historical focus on proactive security, praising its influence on other operating systems. Several commenters highlight OpenBSD's pledge ("secure by default") and the depth of its code audits, contrasting it favorably with Linux's reactive approach. Some debate the practicality of OpenBSD for everyday use, citing hardware compatibility challenges and a smaller software ecosystem. Others acknowledge these limitations but emphasize OpenBSD's value as a learning resource and a model for secure coding practices. The maintainability of its codebase and the project's commitment to simplicity are also lauded. A few users mention specific innovations like OpenSSH and CARP, while others appreciate the project's consistent philosophy and long-term vision.
The GNU Make Standard Library (GMSL) offers a collection of reusable Makefile functions designed to simplify common build tasks and promote best practices in GNU Make projects. It provides functions for tasks like finding files, managing dependencies, working with directories, handling shell commands, and more. By incorporating GMSL, Makefiles can become more concise, readable, and maintainable, reducing boilerplate and improving consistency across projects. The library is designed to be modular, allowing users to include only the functions they need.
Hacker News users discussed the GNU Make Standard Library (GMSL), mostly focusing on its potential usefulness and questioning its necessity. Some commenters appreciated the idea of standardized functions for common Make tasks, finding it could improve readability and reduce boilerplate. Others argued that existing solutions like shell scripts or including Makefiles suffice, viewing GMSL as adding unnecessary complexity. The discussion also touched upon the discoverability of such a library and whether the chosen license (GPLv3) would limit its adoption. Some expressed concern about the potential for GPLv3 to "infect" projects using the library. Finally, a few users pointed out alternatives like using a higher-level build system or other scripting languages to replace Make entirely.
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.
Bunster is a tool that compiles Bash scripts into standalone, statically-linked executables. This allows for easy distribution and execution of Bash scripts without requiring a separate Bash installation on the target system. It achieves this by embedding a minimal Bash interpreter and necessary dependencies within the generated executable. This makes scripts more portable and user-friendly, especially for scenarios where installing dependencies or ensuring a specific Bash version is impractical.
Hacker News users discussed Bunster's novel approach to compiling Bash scripts, expressing interest in its potential while also raising concerns. Several questioned the practical benefits over existing solutions like shc or containers, particularly regarding dependency management and debugging complexity. Some highlighted the inherent limitations of Bash as a scripting language compared to more robust alternatives for complex applications. Others appreciated the project's ingenuity and suggested potential use cases like simplifying distribution of simple scripts or bypassing system-level restrictions on scripting. The discussion also touched upon the performance implications of this compilation method and the challenges of handling Bash's dynamic nature. A few commenters expressed curiosity about the inner workings of the compilation process and its handling of external commands.
Summary of Comments ( 12 )
https://news.ycombinator.com/item?id=43769461
The Hacker News comments discuss potential reasons for eBPF program incompatibility across different kernels, focusing primarily on kernel version discrepancies and configuration variations. Some commenters highlight the rapid evolution of the eBPF ecosystem, leading to frequent breaking changes between kernel releases. Others point to the importance of checking for specific kernel features and configurations (like
CONFIG_BPF_JIT) that might be enabled on one system but not another, especially when using newer eBPF functionalities. The use of CO-RE (Compile Once – Run Everywhere) and its limitations are also brought up, with users encountering problems despite its intent to improve portability. Finally, some suggest practical debugging strategies, such as usingbpftoolto inspect program behavior and verify kernel support for required features. A few commenters mention the challenge of staying up-to-date with eBPF's rapid development, emphasizing the need for careful testing across target kernel versions.The Hacker News post "Why Does My eBPF Program Work on One Kernel but Fail on Another?" with the ID 43769461 has several comments discussing the intricacies and challenges of working with eBPF across different kernel versions.
Several commenters highlight the rapid pace of eBPF development and the resulting instability across kernel versions. One commenter points out that the constant evolution, while beneficial in the long run, makes it difficult for developers to maintain compatibility. They mention the frequent changes in verifier rules and helper functions as primary culprits. Another echoes this sentiment, stating that keeping up with these changes can be a full-time job, particularly when dealing with complex eBPF programs. This rapid evolution necessitates careful attention to kernel version compatibility during development and deployment.
The discussion also delves into the specifics of eBPF program loading and verification. One commenter explains how the behavior of the eBPF verifier can change between kernel versions, leading to programs that work on one kernel but fail on another. They mention that seemingly minor kernel upgrades can sometimes introduce breaking changes in the verifier's logic, causing previously valid programs to be rejected. This emphasizes the need for thorough testing across different target kernels.
Another thread focuses on the challenges of debugging eBPF programs. A user shares their experience of encountering cryptic error messages from the verifier, making it difficult to pinpoint the root cause of the issue. They suggest that improved tooling and more descriptive error messages would significantly ease the debugging process. Another commenter suggests using dynamic tracing tools like
bpftraceto gain insights into the program's execution and identify potential problems.The complexities of eBPF helper functions are also addressed. One commenter points out that the availability and behavior of helper functions can vary across kernels. They recommend consulting the kernel documentation and checking for changes in helper function signatures between kernel versions. Another user advises against relying on undocumented helper functions, as their behavior might change unexpectedly.
Finally, several commenters emphasize the importance of staying updated with the latest eBPF developments. They recommend subscribing to mailing lists, following relevant communities, and keeping track of kernel release notes to anticipate potential compatibility issues. They also advocate for better documentation and tooling to simplify eBPF development and improve cross-kernel compatibility.