prctl(2)

NAME#

prctl - operations on a process or thread

LIBRARY#

Standard C library (libc, -lc)

SYNOPSIS#

#include <linux/prctl.h>\n  /* Definition of \nPR_*\n constants */
\n#include <sys/prctl.h>

int prctl(int \nop\n, ...);

DESCRIPTION#

prctl() manipulates various aspects of the behavior of the calling thread or process.

prctl() is called with a first argument describing what to do, and further arguments with a significance depending on the first one. The first argument can be:

PR_CAP_AMBIENT

PR_CAPBSET_READ

PR_CAPBSET_DROP

PR_SET_CHILD_SUBREAPER

PR_GET_CHILD_SUBREAPER

PR_SET_DUMPABLE

PR_GET_DUMPABLE

PR_SET_ENDIAN

PR_GET_ENDIAN

PR_SET_FP_MODE

PR_GET_FP_MODE

PR_SET_FPEMU

PR_GET_FPEMU

PR_SET_FPEXC

PR_GET_FPEXC

PR_SET_IO_FLUSHER

PR_GET_IO_FLUSHER

PR_SET_KEEPCAPS

PR_GET_KEEPCAPS

PR_MCE_KILL

PR_MCE_KILL_GET

PR_SET_MM

PR_SET_VMA

PR_MPX_ENABLE_MANAGEMENT

PR_MPX_DISABLE_MANAGEMENT

PR_SET_NAME

PR_GET_NAME

PR_SET_NO_NEW_PRIVS

PR_GET_NO_NEW_PRIVS

PR_PAC_RESET_KEYS

PR_SET_PDEATHSIG

PR_GET_PDEATHSIG

PR_SET_PTRACER

PR_SET_SECCOMP

PR_GET_SECCOMP

PR_SET_SECUREBITS

PR_GET_SECUREBITS

PR_GET_SPECULATION_CTRL

PR_SET_SPECULATION_CTRL

PR_SVE_SET_VL

PR_SVE_GET_VL

PR_SET_SYSCALL_USER_DISPATCH

PR_SET_TAGGED_ADDR_CTRL

PR_GET_TAGGED_ADDR_CTRL

PR_TASK_PERF_EVENTS_DISABLE

PR_TASK_PERF_EVENTS_ENABLE

PR_SET_THP_DISABLE

PR_GET_THP_DISABLE

PR_GET_TID_ADDRESS

PR_SET_TIMERSLACK

PR_GET_TIMERSLACK

PR_SET_TIMING

PR_GET_TIMING

PR_SET_TSC

PR_GET_TSC

PR_SET_UNALIGN

PR_GET_UNALIGN

PR_GET_AUXV

PR_SET_MDWE

PR_GET_MDWE

RETURN VALUE#

On success, a nonnegative value is returned. On error, -1 is returned, and errno is set to indicate the error.

ERRORS#

EINVAL

The value of op is not recognized, or not supported on this system.

EINVAL

An unused argument is nonzero.

VERSIONS#

IRIX has a prctl() system call (also introduced in Linux 2.1.44 as irix_prctl on the MIPS architecture), with prototype

ptrdiff_t prctl(int \nop\n, int \narg2\n, int \narg3\n);\n

and operations to get the maximum number of processes per user, get the maximum number of processors the calling process can use, find out whether a specified process is currently blocked, get or set the maximum stack size, and so on.

STANDARDS#

Linux.

HISTORY#

Linux 2.1.57, glibc 2.0.6

CAVEATS#

The prototype of the libc wrapper uses a variadic argument list. This makes it necessary to pass the arguments with the right width. When passing numeric constants, such as 0, use a suffix: 0L.

Careless use of some prctl() operations can confuse the user-space run-time environment, so these operations should be used with care.

SEE ALSO#

signal(2), PR_CAP_AMBIENT(2const), PR_CAPBSET_READ(2const), PR_CAPBSET_DROP(2const), PR_SET_CHILD_SUBREAPER(2const), PR_GET_CHILD_SUBREAPER(2const), PR_SET_DUMPABLE(2const), PR_GET_DUMPABLE(2const), PR_SET_ENDIAN(2const), PR_GET_ENDIAN(2const), PR_SET_FP_MODE(2const), PR_GET_FP_MODE(2const), PR_SET_FPEMU(2const), PR_GET_FPEMU(2const), PR_SET_FPEXC(2const), PR_GET_FPEXC(2const), PR_SET_IO_FLUSHER(2const), PR_GET_IO_FLUSHER(2const), PR_SET_KEEPCAPS(2const), PR_GET_KEEPCAPS(2const), PR_MCE_KILL(2const), PR_MCE_KILL_GET(2const), PR_SET_MM(2const), PR_SET_VMA(2const), PR_MPX_ENABLE_MANAGEMENT(2const), PR_MPX_DISABLE_MANAGEMENT(2const), PR_SET_NAME(2const), PR_GET_NAME(2const), PR_SET_NO_NEW_PRIVS(2const), PR_GET_NO_NEW_PRIVS(2const), PR_PAC_RESET_KEYS(2const), PR_SET_PDEATHSIG(2const), PR_GET_PDEATHSIG(2const), PR_SET_PTRACER(2const), PR_SET_SECCOMP(2const), PR_GET_SECCOMP(2const), PR_SET_SECUREBITS(2const), PR_GET_SECUREBITS(2const), PR_SET_SPECULATION_CTRL(2const), PR_GET_SPECULATION_CTRL(2const), PR_SVE_SET_VL(2const), PR_SVE_GET_VL(2const), PR_SET_SYSCALL_USER_DISPATCH(2const), PR_SET_TAGGED_ADDR_CTRL(2const), PR_GET_TAGGED_ADDR_CTRL(2const), PR_TASK_PERF_EVENTS_DISABLE(2const), PR_TASK_PERF_EVENTS_ENABLE(2const), PR_SET_THP_DISABLE(2const), PR_GET_THP_DISABLE(2const), PR_GET_TID_ADDRESS(2const), PR_SET_TIMERSLACK(2const), PR_GET_TIMERSLACK(2const), PR_SET_TIMING(2const), PR_GET_TIMING(2const), PR_SET_TSC(2const), PR_GET_TSC(2const), PR_SET_UNALIGN(2const), PR_GET_UNALIGN(2const), PR_GET_AUXV(2const), PR_SET_MDWE(2const), PR_GET_MDWE(2const), core(5)