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_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.

STANDARDS
       Linux.

HISTORY
       Linux 4.17.

SEE ALSO
       prctl(2), PR_SET_SPECULATION_CTRL(2const)

Linux man-pages 6.19              2026-02-08   PR_GET_SPECULATION_CTRL(2const)