PR_GET_SPECULATION_CTRL(2const) PR_GET_SPECULATION_CTRL(2const)
NAME
PR_GET_SPECULATION_CTRL - get the state of a speculation misfeature for
the calling thread
LIBRARY
Standard C library (libc, -lc)
SYNOPSIS
#include <linux/prctl.h> /* Definition of PR_* constants */
#include <sys/prctl.h>
int prctl(PR_GET_SPECULATION_CTRL, long misfeature, 0L, 0L, 0L);
DESCRIPTION
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_SPECULA-
TION_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 ex-
ecve(2).
If all bits are 0, then the CPU is not affected by the speculation mis-
feature.
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 specula-
tion misfeature will fail.
RETURN VALUE
On success, PR_GET_SPECULATION_CTRL returns the nonnegative value de-
scribed 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 mis-
feature.
STANDARDS
Linux.
HISTORY
Linux 4.17.
SEE ALSO
prctl(2), PR_SET_SPECULATION_CTRL(2const)
Linux man-pages 6.9.1 2024-06-01 PR_GET_SPECULATION_CTRL(2const)
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