rseq - registers a specified region in a given address space before user-level code execution.
rseq is a Linux syscall that enables user-level code to register and reserve a specific memory region for exclusive execution without outside interruption. It does this by reserving a specific address space for exclusive execution and using the kernel to enforce atomicity of this exclusive code region. The main purpose of rseq is to provide a lightweight concurrency mechanism for multithreaded applications. This syscall is useful when implementing certain performance optimizations, such as loop-level parallelism, where it is critical that only one thread is allowed to execute a specific region of code.
The syscall takes a pointer to a region event structure (struct rseq), the length of that structure, an optional flags argument, and an optional signal argument. The flags are used to indicate what kind of operations the application wishes to perform, such as reading or writing memory. The signal argument allows the application to optionally specify a signal to be sent to the calling process if the operation fails.
By using rseq, user-level code can register and reserve a specific memory region for exclusive execution that is guaranteed to return success or failure atomically. It is important to note, however, that rseq is currently only supported on 64-bit x86 systems and Linux kernel versions 4.13 and later.
struct rseq*[KU] - Pointer to the data structure used to specify a region for exclusive execution.
u32[KU] - Length of the data structure in bytes. Must be given as an argument for safety reasons.
int[K] - Optional argument to indicate what kind of operations the application wishes to perform.
u32[K] - Optional argument to specify a signal to be sent to the calling process if rseq fails.
- K - Originated from kernel-space.
- U - Originated from user space (for example, pointer to user space memory used to get it)
retrieve the arguments for the syscall, then store them as part of the context related to the calling process
Verifiy that the parameters retrieved by the previous probe are valid before attempting to execute the actual system call.
Example Use Case¶
rseq is useful when implementing certain performance optimizations, where it is critical that only one thread is allowed to execute a specific region of code. An example would be loop-level parallelism, where a programmer can take advantage of multiple CPU cores to increase the performance of loops.
rseq is currently only supported on 64-bit x86 systems and Linux kernel versions 4.13 and later. It is also not yet supported on memory model architectures, like ARM.
rseq system call can be used in conjunction with the
set_tid_address system call to create a reliable thread-local region event.
This document was automatically generated by OpenAI and needs review. It might not be accurate and might contain errors. The authors of Tracee recommend that the user reads the "events.go" source file to understand the events and their arguments better.