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PRCTL(2)		   Linux Programmer's Manual		      PRCTL(2)

NAME
       prctl - operations on a process

SYNOPSIS
       #include	<sys/prctl.h>

       int prctl(int option, unsigned long arg2, unsigned long arg3,
		 unsigned long arg4, unsigned long arg5);

DESCRIPTION
       prctl()	is  called  with  a first argument describing what to do (with
       values defined in _linux/prctl.h_), and further arguments with  a  sig-
       nificance depending on the first	one.  The first	argument can be:

       PR_CAPBSET_READ (since Linux 2.6.25)
	      Return (as the function result) 1	if the capability specified in
	      arg2 is in the calling thread's capability bounding set, or 0 if
	      it  is not.  (The	capability constants are defined in _linux/ca-
	      pability.h_.)  The capability bounding set dictates whether  the
	      process  can  receive  the capability through a file's permitted
	      capability set on	a subsequent call to execve(2).

	      If the capability	specified in arg2 is not valid,	then the  call
	      fails with the error EINVAL.

       PR_CAPBSET_DROP (since Linux 2.6.25)
	      If  the calling thread has the CAP_SETPCAP capability, then drop
	      the capability specified by arg2 from the	calling	thread's capa-
	      bility  bounding	set.   Any children of the calling thread will
	      inherit the newly	reduced	bounding set.

	      The call fails with the error: EPERM if the calling thread  does
	      not  have	 the  CAP_SETPCAP; EINVAL if arg2 does not represent a
	      valid capability;	or EINVAL if file capabilities are not enabled
	      in the kernel, in	which case bounding sets are not supported.

       PR_SET_CHILD_SUBREAPER (since Linux 3.4)
	      If  arg2	is nonzero, set	the "child subreaper" attribute	of the
	      calling process; if arg2 is zero,	unset the attribute.   When  a
	      process is marked	as a child subreaper, all of the children that
	      it creates, and their descendants, will be marked	 as  having  a
	      subreaper.   In effect, a	subreaper fulfills the role of init(1)
	      for its descendant processes.  Upon  termination	of  a  process
	      that  is orphaned	(i.e., its immediate parent has	already	termi-
	      nated) and marked	as having a subreaper, the nearest still  liv-
	      ing ancestor subreaper will receive a SIGCHLD signal and be able
	      to wait(2) on the	process	to discover its	termination status.

       PR_GET_CHILD_SUBREAPER (since Linux 3.4)
	      Return the "child	subreaper" setting of the caller, in the loca-
	      tion pointed to by (int *) arg2.

       PR_SET_DUMPABLE (since Linux 2.3.20)
	      Set  the	state  of  the flag determining	whether	core dumps are
	      produced for the calling process upon delivery of	a signal whose
	      default  behavior	 is  to	 produce a core	dump.  (Normally, this
	      flag is set for a	process	by default, but	it is cleared  when  a
	      set-user-ID or set-group-ID program is executed and also by var-
	      ious system calls	that manipulate	process	UIDs  and  GIDs).   In
	      kernels  up  to  and  including  2.6.12,	arg2  must be either 0
	      (process is not dumpable)	or 1 (process is  dumpable).   Between
	      kernels 2.6.13 and 2.6.17, the value 2 was also permitted, which
	      caused any binary	which normally	would  not  be	dumped	to  be
	      dumped readable by root only; for	security reasons, this feature
	      has   been   removed.    (See   also    the    description    of
	      /proc/sys/fs/suid_dumpable  in proc(5).)	Processes that are not
	      dumpable can not be attached via ptrace(2) PTRACE_ATTACH.

       PR_GET_DUMPABLE (since Linux 2.3.20)
	      Return (as the function result) the current state	of the calling
	      process's	dumpable flag.

       PR_SET_ENDIAN (since Linux 2.6.18, PowerPC only)
	      Set the endian-ness of the calling process to the	value given in
	      arg2, which should  be  one  of  the  following:	PR_ENDIAN_BIG,
	      PR_ENDIAN_LITTLE,	or PR_ENDIAN_PPC_LITTLE	(PowerPC pseudo	little
	      endian).

       PR_GET_ENDIAN (since Linux 2.6.18, PowerPC only)
	      Return the endian-ness of	the calling process, in	 the  location
	      pointed to by (int *) arg2.

       PR_SET_FPEMU (since Linux 2.4.18, 2.5.9,	only on	ia64)
	      Set   floating-point  emulation  control	bits  to  arg2.	  Pass
	      PR_FPEMU_NOPRINT to silently emulate fp operations accesses,  or
	      PR_FPEMU_SIGFPE to not emulate fp	operations and send SIGFPE in-
	      stead.

       PR_GET_FPEMU (since Linux 2.4.18, 2.5.9,	only on	ia64)
	      Return floating-point emulation control bits,  in	 the  location
	      pointed to by (int *) arg2.

       PR_SET_FPEXC (since Linux 2.4.21, 2.5.32, only on PowerPC)
	      Set    floating-point    exception    mode    to	 arg2.	  Pass
	      PR_FP_EXC_SW_ENABLE to  use  FPEXC  for  FP  exception  enables,
	      PR_FP_EXC_DIV  for  floating-point divide	by zero, PR_FP_EXC_OVF
	      for floating-point overflow,  PR_FP_EXC_UND  for	floating-point
	      underflow,  PR_FP_EXC_RES	 for  floating-point  inexact  result,
	      PR_FP_EXC_INV    for    floating-point	invalid	    operation,
	      PR_FP_EXC_DISABLED  for FP exceptions disabled, PR_FP_EXC_NONRE-
	      COV for async nonrecoverable exception mode, PR_FP_EXC_ASYNC for
	      async  recoverable exception mode, PR_FP_EXC_PRECISE for precise
	      exception	mode.

       PR_GET_FPEXC (since Linux 2.4.21, 2.5.32, only on PowerPC)
	      Return floating-point exception mode, in the location pointed to
	      by (int *) arg2.

       PR_SET_KEEPCAPS (since Linux 2.2.18)
	      Set  the	state  of the thread's "keep capabilities" flag, which
	      determines whether the threads's	permitted  capability  set  is
	      cleared  when  a	change	is made	to the threads's user IDs such
	      that the threads's real UID, effective UID, and saved  set-user-
	      ID  all  become nonzero when at least one	of them	previously had
	      the value	0.   By	 default,  the	permitted  capability  set  is
	      cleared  when such a change is made; setting the "keep capabili-
	      ties" flag prevents it from being	cleared.  arg2 must be	either
	      0	(permitted capabilities	are cleared) or	1 (permitted capabili-
	      ties are kept).  (A thread's effective capability	set is	always
	      cleared when such	a credential change is made, regardless	of the
	      setting of the "keep capabilities" flag.)	 The  "keep  capabili-
	      ties" value will be reset	to 0 on	subsequent calls to execve(2).

       PR_GET_KEEPCAPS (since Linux 2.2.18)
	      Return (as the function result) the current state	of the calling
	      threads's	"keep capabilities" flag.

       PR_SET_NAME (since Linux	2.6.9)
	      Set the name of the calling thread, using	the value in the loca-
	      tion  pointed  to	 by  (char *)  arg2.  The name can be up to 16
	      bytes long, and should be	null-terminated	if it  contains	 fewer
	      bytes.   This  is	 the  same  attribute  that  can  be  set  via
	      pthread_setname_np(3) and	retrieved using	pthread_getname_np(3).
	      The      attribute      is      likewise	    accessible	   via
	      /proc/self/task/[tid]/comm, where	tid is the name	of the calling
	      thread.

       PR_GET_NAME (since Linux	2.6.11)
	      Return  the name of the calling thread, in the buffer pointed to
	      by (char *) arg2.	 The buffer should allow space for  up	to  16
	      bytes;  the  returned  string  will  be null-terminated if it is
	      shorter than that.

       PR_SET_NO_NEW_PRIVS (since Linux	3.5)
	      Set the calling process's	no_new_privs bit to the	value in arg2.
	      With  no_new_privs  set  to  1,  execve(2) promises not to grant
	      privileges to do anything	that could not have been done  without
	      the  execve(2)  call (for	example, rendering the set-user-ID and
	      set-group-ID permission bits, and	 file  capabilities  non-func-
	      tional).	 Once  set,  this bit cannot be	unset.	The setting of
	      this bit	is  inherited  by  children  created  by  fork(2)  and
	      clone(2),	and preserved across execve(2).

	      For  more	 information,  see  the	 kernel	source file Documenta-
	      tion/prctl/no_new_privs.txt.

       PR_GET_NO_NEW_PRIVS (since Linux	3.5)
	      Return (as the function result) the value	 of  the  no_new_privs
	      bit for the current process.  A value of 0 indicates the regular
	      execve(2)	behavior.  A value of 1	indicates execve(2) will oper-
	      ate in the privilege-restricting mode described above.

       PR_SET_PDEATHSIG	(since Linux 2.1.57)
	      Set  the	parent	process	death signal of	the calling process to
	      arg2 (either a signal value in the  range	 1..maxsig,  or	 0  to
	      clear).	This  is  the signal that the calling process will get
	      when its parent dies.  This value	is cleared for the child of  a
	      fork(2)  and (since Linux	2.4.36 / 2.6.23) when executing	a set-
	      user-ID or set-group-ID binary.  This value is preserved	across
	      execve(2).

       PR_GET_PDEATHSIG	(since Linux 2.3.15)
	      Return  the current value	of the parent process death signal, in
	      the location pointed to by (int *) arg2.

       PR_SET_PTRACER (since Linux 3.4)
	      This is meaningful only when the Yama LSM	is enabled and in mode
	      1	   ("restricted	   ptrace",    visible	  via	/proc/sys/ker-
	      nel/yama/ptrace_scope).  When a "ptracer process ID"  is	passed
	      in  arg2,	 the  caller is	declaring that the ptracer process can
	      ptrace(2)	the calling process as if it were a direct process an-
	      cestor.	Each  PR_SET_PTRACER  operation	 replaces the previous
	      "ptracer process ID".  Employing PR_SET_PTRACER with arg2	set to
	      0	 clears	 the  caller's	"ptracer  process  ID".	  If  arg2  is
	      PR_SET_PTRACER_ANY, the ptrace restrictions introduced  by  Yama
	      are effectively disabled for the calling process.

	      For  further  information, see the kernel	source file Documenta-
	      tion/security/Yama.txt.

       PR_SET_SECCOMP (since Linux 2.6.23)
	      Set the secure computing (seccomp) mode for the calling  thread,
	      to  limit	 the  available	system calls.  The seccomp mode	is se-
	      lected  via  arg2.   (The	 seccomp  constants  are  defined   in
	      _linux/seccomp.h_.)

	      With  arg2 set to	SECCOMP_MODE_STRICT the	only system calls that
	      the thread is permitted to make are read(2), write(2), _exit(2),
	      and  sigreturn(2).  Other	system calls result in the delivery of
	      a	SIGKILL	signal.	 Strict	secure computing mode  is  useful  for
	      number-crunching applications that may need to execute untrusted
	      byte code, perhaps obtained by reading from a  pipe  or  socket.
	      This  operation  is  available  only if the kernel is configured
	      with CONFIG_SECCOMP enabled.

	      With arg2	set to SECCOMP_MODE_FILTER (since Linux	3.5) the  sys-
	      tem  calls allowed are defined by	a pointer to a Berkeley	Packet
	      Filter passed in arg3.  This argument is	a  pointer  to	struct
	      sock_fprog;  it can be designed to filter	arbitrary system calls
	      and system call arguments.  This mode is available only  if  the
	      kernel is	configured with	CONFIG_SECCOMP_FILTER enabled.

	      If  SECCOMP_MODE_FILTER filters permit fork(2), then the seccomp
	      mode is inherited	by children created by fork(2);	 if  execve(2)
	      is  permitted,  then  the	 seccomp  mode is preserved across ex-
	      ecve(2).	If the filters permit prctl() calls,  then  additional
	      filters can be added; they are run in order until	the first non-
	      allow result is seen.

	      For further information, see the kernel source  file  Documenta-
	      tion/prctl/seccomp_filter.txt.

       PR_GET_SECCOMP (since Linux 2.6.23)
	      Return (as the function result) the secure computing mode	of the
	      calling thread.  If the caller is	not in secure computing	 mode,
	      this operation returns 0;	if the caller is in strict secure com-
	      puting mode, then	the prctl() call will cause a  SIGKILL	signal
	      to be sent to the	process.  If the caller	is in filter mode, and
	      this system call is allowed by the seccomp filters,  it  returns
	      2.  This operation is available only if the kernel is configured
	      with CONFIG_SECCOMP enabled.

       PR_SET_SECUREBITS (since	Linux 2.6.26)
	      Set the "securebits" flags of the	calling	thread	to  the	 value
	      supplied in arg2.	 See capabilities(7).

       PR_GET_SECUREBITS (since	Linux 2.6.26)
	      Return  (as  the	function result) the "securebits" flags	of the
	      calling thread.  See capabilities(7).

       PR_SET_THP_DISABLE (since Linux 3.15)
	      Set the state of the "THP	disable" flag for the calling  thread.
	      If  arg2	has  a nonzero value, the flag is set, otherwise it is
	      cleared.	Setting	this flag  provides  a	method	for  disabling
	      transparent  huge	 pages for jobs	where the code cannot be modi-
	      fied, and	using a	malloc hook with madvise(2) is not  an	option
	      (i.e., statically	allocated data).  The setting of the "THP dis-
	      able" flag is inherited by a child created via  fork(2)  and  is
	      preserved	across execve(2).

       PR_GET_THP_DISABLE (since Linux 3.15)
	      Return (via the function result) the current setting of the "THP
	      disable" flag for	the calling thread: either 1, if the  flag  is
	      set, or 0, if it is not.

       PR_GET_TID_ADDRESS (since Linux 3.5)
	      Retrieve	the  clear_child_tid address set by set_tid_address(2)
	      and the clone(2)	CLONE_CHILD_CLEARTID  flag,  in	 the  location
	      pointed  to by (int **) arg2.  This feature is available only if
	      the kernel is built with	the  CONFIG_CHECKPOINT_RESTORE	option
	      enabled.

       PR_SET_TIMERSLACK (since	Linux 2.6.28)
	      Set  the	current	 timer	slack  for  the	 calling thread	to the
	      nanosecond value supplied	in arg2.  If  arg2  is	less  than  or
	      equal to zero, reset the current timer slack to the thread's de-
	      fault timer slack	value.	The timer slack	is used	by the	kernel
	      to group timer expirations for the calling thread	that are close
	      to one another; as a  consequence,  timer	 expirations  for  the
	      thread  may  be  up  to the specified number of nanoseconds late
	      (but will	never expire early).  Grouping timer  expirations  can
	      help reduce system power consumption by minimizing CPU wake-ups.

	      The  timer  expirations affected by timer	slack are those	set by
	      select(2),   pselect(2),	 poll(2),   ppoll(2),	epoll_wait(2),
	      epoll_pwait(2),  clock_nanosleep(2),  nanosleep(2), and futex(2)
	      (and thus	the library functions implemented via futexes, includ-
	      ing    pthread_cond_timedwait(3),	   pthread_mutex_timedlock(3),
	      pthread_rwlock_timedrdlock(3),	pthread_rwlock_timedwrlock(3),
	      and sem_timedwait(3)).

	      Timer slack is not applied to threads that are scheduled under a
	      real-time	scheduling policy (see sched_setscheduler(2)).

	      Each thread has two associated timer slack values:  a  "default"
	      value, and a "current" value.  The current value is the one that
	      governs grouping of timer	expirations.  When  a  new  thread  is
	      created,	the  two  timer	 slack values are made the same	as the
	      current value of the creating thread.  Thereafter, a thread  can
	      adjust  its current timer	slack value via	PR_SET_TIMERSLACK (the
	      default value can't be changed).	The timer slack	values of init
	      (PID  1),	 the ancestor of all processes,	are 50,000 nanoseconds
	      (50 microseconds).  The timer slack values are preserved	across
	      execve(2).

       PR_GET_TIMERSLACK (since	Linux 2.6.28)
	      Return (as the function result) the current timer	slack value of
	      the calling thread.

       PR_SET_TIMING (since Linux 2.6.0-test4)
	      Set whether to use  (normal,  traditional)  statistical  process
	      timing  or  accurate  timestamp-based process timing, by passing
	      PR_TIMING_STATISTICAL or PR_TIMING_TIMESTAMP to  arg2.   PR_TIM-
	      ING_TIMESTAMP  is	 not  currently	implemented (attempting	to set
	      this mode	will yield the error EINVAL).

       PR_GET_TIMING (since Linux 2.6.0-test4)
	      Return (as the function result) which process timing  method  is
	      currently	in use.

       PR_TASK_PERF_EVENTS_DISABLE (since Linux	2.6.31)
	      Disable	all  performance  counters  attached  to  the  calling
	      process, regardless of whether the counters were created by this
	      process or another process.  Performance counters	created	by the
	      calling process for other	processes are  unaffected.   For  more
	      information on performance counters, see the Linux kernel	source
	      file tools/perf/design.txt.

	      Originally called	PR_TASK_PERF_COUNTERS_DISABLE;	renamed	 (with
	      same numerical value) in Linux 2.6.32.

       PR_TASK_PERF_EVENTS_ENABLE (since Linux 2.6.31)
	      The  converse of PR_TASK_PERF_EVENTS_DISABLE; enable performance
	      counters attached	to the calling process.

	      Originally called	PR_TASK_PERF_COUNTERS_ENABLE; renamed in Linux
	      2.6.32.

       PR_SET_TSC (since Linux 2.6.26, x86 only)
	      Set  the	state  of  the	flag determining whether the timestamp
	      counter can be read by the process.  Pass	PR_TSC_ENABLE to  arg2
	      to  allow	it to be read, or PR_TSC_SIGSEGV to generate a SIGSEGV
	      when the process tries to	read the timestamp counter.

       PR_GET_TSC (since Linux 2.6.26, x86 only)
	      Return the state of the flag determining whether	the  timestamp
	      counter can be read, in the location pointed to by (int *) arg2.

       PR_SET_UNALIGN
	      (Only  on: ia64, since Linux 2.3.48; parisc, since Linux 2.6.15;
	      PowerPC, since Linux 2.6.18; Alpha, since	Linux 2.6.22) Set  un-
	      aligned access control bits to arg2.  Pass PR_UNALIGN_NOPRINT to
	      silently fix up unaligned	user accesses, or PR_UNALIGN_SIGBUS to
	      generate SIGBUS on unaligned user	access.

       PR_GET_UNALIGN
	      (see  PR_SET_UNALIGN  for	 information on	versions and architec-
	      tures) Return unaligned access control  bits,  in	 the  location
	      pointed to by (int *) arg2.

       PR_MCE_KILL (since Linux	2.6.32)
	      Set the machine check memory corruption kill policy for the cur-
	      rent thread.  If arg2 is	PR_MCE_KILL_CLEAR,  clear  the	thread
	      memory  corruption  kill policy and use the system-wide default.
	      (The system-wide default is defined by /proc/sys/vm/memory_fail-
	      ure_early_kill; see proc(5).)  If	arg2 is	PR_MCE_KILL_SET, use a
	      thread-specific memory corruption	kill policy.   In  this	 case,
	      arg3    defines	 whether    the	   policy    is	  early	  kill
	      (PR_MCE_KILL_EARLY), late	kill (PR_MCE_KILL_LATE), or  the  sys-
	      tem-wide	default	 (PR_MCE_KILL_DEFAULT).	 Early kill means that
	      the thread receives a SIGBUS signal as soon as  hardware	memory
	      corruption  is  detected inside its address space.  In late kill
	      mode, the	process	is killed only when it	accesses  a  corrupted
	      page.   See sigaction(2) for more	information on the SIGBUS sig-
	      nal.  The	policy is inherited by children.  The remaining	unused
	      prctl() arguments	must be	zero for future	compatibility.

       PR_MCE_KILL_GET (since Linux 2.6.32)
	      Return  the  current per-process machine check kill policy.  All
	      unused prctl() arguments must be zero.

       PR_SET_MM (since	Linux 3.3)
	      Modify certain kernel memory map descriptor fields of the	 call-
	      ing process.  Usually these fields are set by the	kernel and dy-
	      namic loader (see	ld.so(8) for more information) and  a  regular
	      application  should  not	use  this feature.  However, there are
	      cases, such as self-modifying programs, where  a	program	 might
	      find  it	useful	to change its own memory map.  This feature is
	      available	only if	the kernel is  built  with  the	 CONFIG_CHECK-
	      POINT_RESTORE option enabled.  The calling process must have the
	      CAP_SYS_RESOURCE capability.  The	value in arg2 is  one  of  the
	      options below, while arg3	provides a new value for the option.

	      PR_SET_MM_START_CODE
		     Set  the  address	above  which the program text can run.
		     The corresponding memory area must	be readable  and  exe-
		     cutable,  but  not	 writable or sharable (see mprotect(2)
		     and mmap(2) for more information).

	      PR_SET_MM_END_CODE
		     Set the address below which the  program  text  can  run.
		     The  corresponding	 memory	area must be readable and exe-
		     cutable, but not writable or sharable.

	      PR_SET_MM_START_DATA
		     Set the address above which initialized and uninitialized
		     (bss)  data  are  placed.	 The corresponding memory area
		     must be readable and  writable,  but  not	executable  or
		     sharable.

	      PR_SET_MM_END_DATA
		     Set the address below which initialized and uninitialized
		     (bss) data	are placed.   The  corresponding  memory  area
		     must  be  readable	 and  writable,	 but not executable or
		     sharable.

	      PR_SET_MM_START_STACK
		     Set the start address of the  stack.   The	 corresponding
		     memory area must be readable and writable.

	      PR_SET_MM_START_BRK
		     Set  the  address above which the program heap can	be ex-
		     panded with brk(2)	call.  The  address  must  be  greater
		     than  the ending address of the current program data seg-
		     ment.  In addition, the combined size  of	the  resulting
		     heap  and	the  size of the data segment can't exceed the
		     RLIMIT_DATA resource limit	(see setrlimit(2)).

	      PR_SET_MM_BRK
		     Set the current brk(2) value.  The	requirements  for  the
		     address  are  the same as for the PR_SET_MM_START_BRK op-
		     tion.

	      The following options are	available since	Linux 3.5.

	      PR_SET_MM_ARG_START
		     Set the address above which the program command  line  is
		     placed.

	      PR_SET_MM_ARG_END
		     Set  the  address below which the program command line is
		     placed.

	      PR_SET_MM_ENV_START
		     Set the address above which the  program  environment  is
		     placed.

	      PR_SET_MM_ENV_END
		     Set  the  address	below which the	program	environment is
		     placed.

		     The    address    passed	 with	  PR_SET_MM_ARG_START,
		     PR_SET_MM_ARG_END,	       PR_SET_MM_ENV_START,	   and
		     PR_SET_MM_ENV_END should belong to	a process stack	 area.
		     Thus,  the	 corresponding	memory	area must be readable,
		     writable, and (depending  on  the	kernel	configuration)
		     have the MAP_GROWSDOWN attribute set (see mmap(2)).

	      PR_SET_MM_AUXV
		     Set  a  new  auxiliary  vector.  The arg3 argument	should
		     provide the address of the	vector.	 The arg4 is the  size
		     of	the vector.

	      PR_SET_MM_EXE_FILE
		     Supersede	the /proc/pid/exe symbolic link	with a new one
		     pointing to a new executable file identified by the  file
		     descriptor	 provided in arg3 argument.  The file descrip-
		     tor should	be obtained with a regular open(2) call.

		     To	change the symbolic link, one needs to unmap  all  ex-
		     isting  executable	 memory	areas, including those created
		     by	the kernel itself (for example the kernel usually cre-
		     ates  at  least  one  executable  memory area for the ELF
		     .text section).

		     The second	limitation is that  such  transitions  can  be
		     done  only	 once in a process life	time.  Any further at-
		     tempts will be rejected.  This should help	system	admin-
		     istrators	monitor	unusual	symbolic-link transitions over
		     all processes running on a	system.

RETURN VALUE
       On  success,  PR_GET_DUMPABLE,  PR_GET_KEEPCAPS,	  PR_GET_NO_NEW_PRIVS,
       PR_GET_THP_DISABLE,  PR_CAPBSET_READ, PR_GET_TIMING, PR_GET_TIMERSLACK,
       PR_GET_SECUREBITS, PR_MCE_KILL_GET, and (if it returns)	PR_GET_SECCOMP
       return the nonnegative values described above.  All other option	values
       return 0	on success.  On	error, -1 is returned, and errno is set	appro-
       priately.

ERRORS
       EFAULT arg2 is an invalid address.

       EINVAL The value	of option is not recognized.

       EINVAL option  is  PR_MCE_KILL or PR_MCE_KILL_GET or PR_SET_MM, and un-
	      used prctl() arguments were not specified	as zero.

       EINVAL arg2 is not valid	value for this option.

       EINVAL option is	PR_SET_SECCOMP or PR_GET_SECCOMP, and the  kernel  was
	      not configured with CONFIG_SECCOMP.

       EINVAL option is	PR_SET_MM, and one of the following is true

	      *	 arg4 or arg5 is nonzero;

	      *	 arg3  is greater than TASK_SIZE (the limit on the size	of the
		 user address space for	this architecture);

	      *	 arg2	  is	 PR_SET_MM_START_CODE,	   PR_SET_MM_END_CODE,
		 PR_SET_MM_START_DATA,		PR_SET_MM_END_DATA,	    or
		 PR_SET_MM_START_STACK,	and the	permissions of the correspond-
		 ing memory area are not as required;

	      *	 arg2  is  PR_SET_MM_START_BRK	or  PR_SET_MM_BRK, and arg3 is
		 less than or equal to the end of the data segment  or	speci-
		 fies  a value that would cause	the RLIMIT_DATA	resource limit
		 to be exceeded.

       EINVAL option is	PR_SET_PTRACER and arg2	is not 0,  PR_SET_PTRACER_ANY,
	      or the PID of an existing	process.

       EINVAL option  is  PR_SET_PDEATHSIG and arg2 is not a valid signal num-
	      ber.

       EINVAL option is	PR_SET_DUMPABLE	and arg2 is neither  SUID_DUMP_DISABLE
	      nor SUID_DUMP_USER.

       EINVAL option is	PR_SET_TIMING and arg2 is not PR_TIMING_STATISTICAL.

       EINVAL option  is  PR_SET_NO_NEW_PRIVS  and  arg2  is not equal to 1 or
	      arg3, arg4, or arg5 is nonzero.

       EINVAL option is	PR_GET_NO_NEW_PRIVS and	arg2, arg3, arg4, or  arg5  is
	      nonzero.

       EINVAL option is	PR_SET_THP_DISABLE and arg3, arg4, or arg5 is nonzero.

       EINVAL option  is  PR_GET_THP_DISABLE  and arg2,	arg3, arg4, or arg5 is
	      nonzero.

       EPERM  option is	PR_SET_SECUREBITS, and the caller does	not  have  the
	      CAP_SETPCAP  capability,	or  tried to unset a "locked" flag, or
	      tried to set a flag whose	corresponding locked flag was set (see
	      capabilities(7)).

       EPERM  option	is    PR_SET_KEEPCAPS,	  and	 the   callers's   SE-
	      CURE_KEEP_CAPS_LOCKED flag is set	(see capabilities(7)).

       EPERM  option is	PR_CAPBSET_DROP, and the  caller  does	not  have  the
	      CAP_SETPCAP capability.

       EPERM  option   is   PR_SET_MM,	and  the  caller  does	not  have  the
	      CAP_SYS_RESOURCE capability.

       EACCES option is	PR_SET_MM, and arg3 is PR_SET_MM_EXE_FILE, the file is
	      not executable.

       EBUSY  option  is  PR_SET_MM,  arg3 is PR_SET_MM_EXE_FILE, and this the
	      second attempt to	change the /proc/pid/exe symbolic link,	 which
	      is prohibited.

       EBADF  option  is  PR_SET_MM,  arg3 is PR_SET_MM_EXE_FILE, and the file
	      descriptor passed	in arg4	is not valid.

VERSIONS
       The prctl() system call was introduced in Linux 2.1.57.

CONFORMING TO
       This call is Linux-specific.  IRIX has a	prctl()	system call (also  in-
       troduced	 in Linux 2.1.44 as irix_prctl on the MIPS architecture), with
       prototype

       ptrdiff_t prctl(int option, int arg2, int arg3);

       and options 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	 maxi-
       mum stack size, and so on.

SEE ALSO
       signal(2), core(5)

COLOPHON
       This  page  is  part of release 3.74 of the Linux man-pages project.  A
       description of the project, information about reporting bugs,  and  the
       latest	  version     of     this    page,    can    be	   found    at
       http://www.kernel.org/doc/man-pages/.

Linux				  2014-04-14			      PRCTL(2)

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | CONFORMING TO | SEE ALSO | COLOPHON

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