prctl

(2)

operations on a process or thread

System callsmanpages-dev 6.9.1-1

#include <linux/prctl.h> /* Definition of PR_* constants */ #include <sys/prctl.h> int prctl(int op, ...);

LIBRARY

Standard C library (libc, -lc)

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.

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(2)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(2)PR_SET_SECUREBITS(2const)PR_GET_SECUREBITS(2const)PR_SET_SPECULATION_CTRL(2const)PR_GET_SPECULATION_CTRL(2const)