prctl(2)

NAME
prctl - operations on a process or thread

LIBRARY
Standard C library (libc, -lc)

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

int prctl(int op, ...);

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 op, int arg2, int arg3);

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)