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io_uring_enter

Intro

io_uring_enter - a system call that submits and optionally waits on a set of I/O operations

Description

The io_uring_enter system call allows processes to perform I/O operations and optionally wait for their completion. This call combines the submission of a set of I/O operations with the ability to wait on them without making additional system calls. The operations used to fulfill the request are submitted via an io_uring instance associated with the process. The number of operations submitted is given in the to_submit argument and is expected to be a positive integer.

The min_complete argument tells the system how many I/O operations need to be completed (or failed) before returning from the io_uring_enter call. This value is also expected to be a positive integer, or zero, if the caller is not interested in waiting on individual I/O completion events. The flags argument is a bitmask of flags that modify the caller's request. The flags can be used to indicate if I/O operations should remain in the submission queue on error, if any registered buffers can be safely reused without the caller double-checking their contents, or if the caller should be woken up if any operation within their submission set completes or fails.

The sig argument contains a pointer to a signal set that may be used to unblock system calls being waited on. If set to NULL, the behavior will be the same as that of a call to io_uring_enter without a signal set.

Arguments

  • fd:unsigned int - file descriptor associated with the io_uring instance used to submit I/O requests.
  • to_submit:unsigned int[OPT] - the number of I/O requests to submit.
  • min_complete:unsigned int[OPT] - the number of I/O requests that need to be completed before io_uring_enter returns.
  • flags:unsigned int[OPT] - flags modifying the request submission and completion.
  • sig:sigset_t*[U] - pointer to a signal set that may unblock system calls.

Available Tags

  • K - Originated from kernel-space.
  • U - Originated from user space (in this case, the sig argument is a pointer to a signal set located in user space).
  • OPT - Optional argument - might not always be available (passed with null value)

Hooks

io_uring_enter

Type

Kprobe + Ringbuffer

Purpose

To monitor the submission and completion of I/O operations.

Example Use Case

A use case for the io_uring_enter system call could be in an application that needs to monitor the status of a large number of I/O operations. This application could submit requests using the io_uring system and then use the io_uring_enter system call to wait on their completion, without the need to make additional system calls.

Issues

The signal set passed to io_uring_enter is potentially vulnerable to a time of check to time of use (TOCTOU) attack if an unprivileged process can manipulate it before the system call is made.

The io_uring_submit and io_uring_wait system calls are related to, and should be used in conjunction with, io_uring_enter.

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.