PR_GET_SPECULATION_CTRL(2const)

Usage

#include <linux/prctl.h>  /* Definition of PR_* constants */
#include <sys/prctl.h>

int prctl(PR_GET_SPECULATION_CTRL, long misfeature, 0L, 0L, 0L);

Library

Standard C library (libc, -lc)

Overview

Return the state of the speculation misfeature specified in misfeature.

Currently, misfeature must be one of:

`PR_SPEC_STORE_BYPASS`	Get the state of the speculative store bypass misfeature.
`PR_SPEC_INDIRECT_BRANCH (since Linux 4.20)`	Get the state of the indirect branch speculation misfeature.

The return value uses bits 0-4 with the following meaning:

`PR_SPEC_PRCTL`	Mitigation can be controlled per thread by PR_SET_SPECULATION_CTRL(2const).
`PR_SPEC_ENABLE`	The speculation feature is enabled, mitigation is disabled.
`PR_SPEC_DISABLE`	The speculation feature is disabled, mitigation is enabled.
`PR_SPEC_FORCE_DISABLE`	Same as `PR_SPEC_DISABLE` but cannot be undone.
`PR_SPEC_DISABLE_NOEXEC (since Linux 5.1)`	Same as `PR_SPEC_DISABLE`, but the state will be cleared on execve(2).

If all bits are 0, then the CPU is not affected by the speculation misfeature.

If PR_SPEC_PRCTL is set, then per-thread control of the mitigation is available. If not set, PR_SET_SPECULATION_CTRL(2const) for the speculation misfeature will fail.

Return value

On success, PR_GET_SPECULATION_CTRL returns the nonnegative value described above. On error, -1 is returned, and errno is set to indicate the error.

Errors

ENODEV: The kernel or CPU does not support the requested speculation misfeature.

Releases

2 releases since Debian 13 (Trixie); the text changed 1 time.

13
Arch

Referred to by

prctl(2) operations on a process or thread PR_SET_SPECULATION_CTRL(2const) set the state of a speculation misfeature for the calling thread