Writing a system call tracer using eBPF
A system call tracer using eBPF technology has been developed to replicate strace functionalities, focusing on common system calls and enhancing system-level interaction monitoring in Linux.
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The article discusses the development of a system call tracer using eBPF (Extended Berkeley Packet Filter) technology, which allows users to run custom programs within the Linux kernel. The tracer aims to replicate functionalities similar to the well-known tool strace, focusing on a limited set of common system calls. Key concepts include tracepoints, which are specific instrumentation points in the kernel, and eBPF maps, which facilitate data sharing between eBPF programs and user-space applications. The implementation involves writing eBPF programs that respond to system call entry and exit events, capturing system call arguments and return values. The loader program is responsible for setting up the environment, spawning a child process to execute the target program, and managing the eBPF programs. The article provides code snippets for defining data structures, writing eBPF programs, and handling system call logging. The final implementation allows for monitoring system calls made by a specified process, enhancing the ability to trace and debug system-level interactions in Linux.
- eBPF enables running custom programs in the Linux kernel for enhanced safety and maintainability.
- The tracer developed mimics the functionality of strace, focusing on a subset of system calls.
- Key components include tracepoints for hooking into kernel events and eBPF maps for data sharing.
- The implementation involves writing eBPF programs for system call entry and exit events.
- The loader program manages the execution environment and attaches eBPF programs to trace system calls.
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2 commentsWhere eBPF is powerful is that it allows you to extend the tracepoint ability to grab more complicated system call arguments. The first register argument to open(2) for instance, is a pointer to the filename to open. Merely reporting the registers is largely useless, the tracer needs to chase the pointer and report the string too. An eBPF filter can be used to recognize that the tracepoint is at an open(2) and to read the userspace memory that the relevant register points to. This enables a "full" strace replacement without using ptrace at all. There's some ongoing work to add this capability to `perf trace`.
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