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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | CONFORMING TO | SEE ALSO | COLOPHON |
PRCTL(2) Linux Programmer's Manual PRCTL(2)
prctl - operations on a process or thread
#include <sys/prctl.h>
int prctl(int option, unsigned long arg2, unsigned long arg3,
unsigned long arg4, unsigned long arg5);
prctl() manipulates various aspects of the behavior of the calling
thread or process.
Note that careless use of some prctl() operations can confuse the
user-space run-time environment, so these operations should be used
with care.
prctl() is called with a first argument describing what to do (with
values defined in <linux/prctl.h>), and further arguments with a
significance depending on the first one. The first argument can be:
PR_CAP_AMBIENT (since Linux 4.3)
Reads or changes the ambient capability set of the calling
thread, according to the value of arg2, which must be one of
the following:
PR_CAP_AMBIENT_RAISE
The capability specified in arg3 is added to the
ambient set. The specified capability must already be
present in both the permitted and the inheritable sets
of the process. This operation is not permitted if the
SECBIT_NO_CAP_AMBIENT_RAISE securebit is set.
PR_CAP_AMBIENT_LOWER
The capability specified in arg3 is removed from the
ambient set.
PR_CAP_AMBIENT_IS_SET
The prctl() call returns 1 if the capability in arg3 is
in the ambient set and 0 if it is not.
PR_CAP_AMBIENT_CLEAR_ALL
All capabilities will be removed from the ambient set.
This operation requires setting arg3 to zero.
In all of the above operations, arg4 and arg5 must be
specified as 0.
Higher-level interfaces layered on top of the above operations
are provided in the libcap(3) library in the form of
cap_get_ambient(3), cap_set_ambient(3), and
cap_reset_ambient(3).
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/capability.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.
A higher-level interface layered on top of this operation is
provided in the libcap(3) library in the form of
cap_get_bound(3).
PR_CAPBSET_DROP (since Linux 2.6.25)
If the calling thread has the CAP_SETPCAP capability within
its user namespace, then drop the capability specified by arg2
from the calling thread's capability 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.
A higher-level interface layered on top of this operation is
provided in the libcap(3) library in the form of
cap_drop_bound(3).
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.
A subreaper fulfills the role of init(1) for its descendant
processes. When a process becomes orphaned (i.e., its
immediate parent terminates), then that process will be
reparented to the nearest still living ancestor subreaper.
Subsequently, calls to getppid(2) in the orphaned process will
now return the PID of the subreaper process, and when the
orphan terminates, it is the subreaper process that will
receive a SIGCHLD signal and will be able to wait(2) on the
process to discover its termination status.
The setting of the "child subreaper" attribute is not
inherited by children created by fork(2) and clone(2). The
setting is preserved across execve(2).
Establishing a subreaper process is useful in session
management frameworks where a hierarchical group of processes
is managed by a subreaper process that needs to be informed
when one of the processes—for example, a double-forked daemon—
terminates (perhaps so that it can restart that process).
Some init(1) frameworks (e.g., systemd(1)) employ a subreaper
process for similar reasons.
PR_GET_CHILD_SUBREAPER (since Linux 3.4)
Return the "child subreaper" setting of the caller, in the
location pointed to by (int *) arg2.
PR_SET_DUMPABLE (since Linux 2.3.20)
Set the state of the "dumpable" attribute, which determines
whether core dumps are produced for the calling process upon
delivery of a signal whose default behavior is to produce a
core dump.
In kernels up to and including 2.6.12, arg2 must be either 0
(SUID_DUMP_DISABLE, process is not dumpable) or 1
(SUID_DUMP_USER, 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).)
Normally, the "dumpable" attribute is set to 1. However, it
is reset to the current value contained in the file
/proc/sys/fs/suid_dumpable (which by default has the value 0),
in the following circumstances:
* The process's effective user or group ID is changed.
* The process's filesystem user or group ID is changed (see
credentials(7)).
* The process executes (execve(2)) a set-user-ID or set-
group-ID program, resulting in a change of either the
effective user ID or the effective group ID.
* The process executes (execve(2)) a program that has file
capabilities (see capabilities(7)), but only if the
permitted capabilities gained exceed those already
permitted for the process.
Processes that are not dumpable can not be attached via
ptrace(2) PTRACE_ATTACH; see ptrace(2) for further details.
If a process is not dumpable, the ownership of files in the
process's /proc/[pid] directory is affected as described in
proc(5).
PR_GET_DUMPABLE (since Linux 2.3.20)
Return (as the function result) the current state of the
calling process's dumpable attribute.
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_FP_MODE (since Linux 4.0, only on MIPS)
On the MIPS architecture, user-space code can be built using
an ABI which permits linking with code that has more
restrictive floating-point (FP) requirements. For example,
user-space code may be built to target the O32 FPXX ABI and
linked with code built for either one of the more restrictive
FP32 or FP64 ABIs. When more restrictive code is linked in,
the overall requirement for the process is to use the more
restrictive floating-point mode.
Because the kernel has no means of knowing in advance which
mode the process should be executed in, and because these
restrictions can change over the lifetime of the process, the
PR_SET_FP_MODE operation is provided to allow control of the
floating-point mode from user space.
The (unsigned int) arg2 argument is a bit mask describing the
floating-point mode used:
PR_FP_MODE_FR
When this bit is unset (so called FR=0 or FR0 mode),
the 32 floating-point registers are 32 bits wide, and
64-bit registers are represented as a pair of registers
(even- and odd- numbered, with the even-numbered
register containing the lower 32 bits, and the odd-
numbered register containing the higher 32 bits).
When this bit is set (on supported hardware), the 32
floating-point registers are 64 bits wide (so called
FR=1 or FR1 mode). Note that modern MIPS
implementations (MIPS R6 and newer) support FR=1 mode
only.
Applications that use the O32 FP32 ABI can operate only
when this bit is unset (FR=0; or they can be used with
FRE enabled, see below). Applications that use the O32
FP64 ABI (and the O32 FP64A ABI, which exists to
provide the ability to operate with existing FP32 code;
see below) can operate only when this bit is set
(FR=1). Applications that use the O32 FPXX ABI can
operate with either FR=0 or FR=1.
PR_FP_MODE_FRE
Enable emulation of 32-bit floating-point mode. When
this mode is enabled, it emulates 32-bit floating-point
operations by raising a reserved-instruction exception
on every instruction that uses 32-bit formats and the
kernel then handles the instruction in software. (The
problem lies in the discrepancy of handling odd-
numbered registers which are the high 32 bits of 64-bit
registers with even numbers in FR=0 mode and the lower
32-bit parts of odd-numbered 64-bit registers in FR=1
mode.) Enabling this bit is necessary when code with
the O32 FP32 ABI should operate with code with
compatible the O32 FPXX or O32 FP64A ABIs (which
require FR=1 FPU mode) or when it is executed on newer
hardware (MIPS R6 onwards) which lacks FR=0 mode
support when a binary with the FP32 ABI is used.
Note that this mode makes sense only when the FPU is in
64-bit mode (FR=1).
Note that the use of emulation inherently has a
significant performance hit and should be avoided if
possible.
In the N32/N64 ABI, 64-bit floating-point mode is always used,
so FPU emulation is not required and the FPU always operates
in FR=1 mode.
This option is mainly intended for use by the dynamic linker
(ld.so(8)).
The arguments arg3, arg4, and arg5 are ignored.
PR_GET_FP_MODE (since Linux 4.0, only on MIPS)
Return (as the function result) the current floating-point
mode (see the description of PR_SET_FP_MODE for details).
On success, the call returns a bit mask which represents the
current floating-point mode.
The arguments arg2, arg3, arg4, and arg5 are ignored.
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 floating-point operation
accesses, or PR_FPEMU_SIGFPE to not emulate floating-point
operations and send SIGFPE instead.
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_NONRECOV 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_IO_FLUSHER (since Linux 5.6)
If a user process is involved in the block layer or filesystem
I/O path, and can allocate memory while processing I/O
requests it must set arg2 to 1. This will put the process in
the IO_FLUSHER state, which allows it special treatment to
make progress when allocating memory. If arg2 is 0, the
process will clear the IO_FLUSHER state, and the default
behavior will be used.
The calling process must have the CAP_SYS_RESOURCE capability.
arg3, arg4, and arg5 must be zero.
The IO_FLUSHER state is inherited by a child process created
via fork(2) and is preserved across execve(2).
Examples of IO_FLUSHER applications are FUSE daemons, SCSI
device emulation daemons, and daemons that perform error
handling like multipath path recovery applications.
PR_GET_IO_FLUSHER (Since Linux 5.6)
Return (as the function result) the IO_FLUSHER state of the
caller. A value of 1 indicates that the caller is in the
IO_FLUSHER state; 0 indicates that the caller is not in the
IO_FLUSHER state.
The calling process must have the CAP_SYS_RESOURCE capability.
arg2, arg3, arg4, and arg5 must be zero.
PR_SET_KEEPCAPS (since Linux 2.2.18)
Set the state of the calling thread's "keep capabilities"
flag. The effect of this flag is described in
capabilities(7). arg2 must be either 0 (clear the flag) or 1
(set the flag). The "keep capabilities" 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 thread's "keep capabilities" flag. See
capabilities(7) for a description of this flag.
PR_MCE_KILL (since Linux 2.6.32)
Set the machine check memory corruption kill policy for the
calling 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_failure_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 system-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 signal. 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 (as the function result) 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
calling process. Usually these fields are set by the kernel
and dynamic 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.
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. The arg4 and arg5
arguments must be zero if unused.
Before Linux 3.10, this feature is available only if the
kernel is built with the CONFIG_CHECKPOINT_RESTORE option
enabled.
PR_SET_MM_START_CODE
Set the address above which the program text can run.
The corresponding memory area must be readable and
executable, but not writable or shareable (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
executable, but not writable or shareable.
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 shareable.
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 shareable.
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
expanded with brk(2) call. The address must be greater
than the ending address of the current program data
segment. 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
option.
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
descriptor should be obtained with a regular open(2)
call.
To change the symbolic link, one needs to unmap all
existing executable memory areas, including those
created by the kernel itself (for example the kernel
usually creates at least one executable memory area for
the ELF .text section).
In Linux 4.9 and earlier, the PR_SET_MM_EXE_FILE
operation can be performed only once in a process's
lifetime; attempting to perform the operation a second
time results in the error EPERM. This restriction was
enforced for security reasons that were subsequently
deemed specious, and the restriction was removed in
Linux 4.10 because some user-space applications needed
to perform this operation more than once.
The following options are available since Linux 3.18.
PR_SET_MM_MAP
Provides one-shot access to all the addresses by
passing in a struct prctl_mm_map (as defined in
<linux/prctl.h>). The arg4 argument should provide the
size of the struct.
This feature is available only if the kernel is built
with the CONFIG_CHECKPOINT_RESTORE option enabled.
PR_SET_MM_MAP_SIZE
Returns the size of the struct prctl_mm_map the kernel
expects. This allows user space to find a compatible
struct. The arg4 argument should be a pointer to an
unsigned int.
This feature is available only if the kernel is built
with the CONFIG_CHECKPOINT_RESTORE option enabled.
PR_MPX_ENABLE_MANAGEMENT, PR_MPX_DISABLE_MANAGEMENT (since Linux
3.19, removed in Linux 5.4; only on x86)
Enable or disable kernel management of Memory Protection
eXtensions (MPX) bounds tables. The arg2, arg3, arg4, and
arg5 arguments must be zero.
MPX is a hardware-assisted mechanism for performing bounds
checking on pointers. It consists of a set of registers
storing bounds information and a set of special instruction
prefixes that tell the CPU on which instructions it should do
bounds enforcement. There is a limited number of these
registers and when there are more pointers than registers,
their contents must be "spilled" into a set of tables. These
tables are called "bounds tables" and the MPX prctl()
operations control whether the kernel manages their allocation
and freeing.
When management is enabled, the kernel will take over
allocation and freeing of the bounds tables. It does this by
trapping the #BR exceptions that result at first use of
missing bounds tables and instead of delivering the exception
to user space, it allocates the table and populates the bounds
directory with the location of the new table. For freeing,
the kernel checks to see if bounds tables are present for
memory which is not allocated, and frees them if so.
Before enabling MPX management using PR_MPX_ENABLE_MANAGEMENT,
the application must first have allocated a user-space buffer
for the bounds directory and placed the location of that
directory in the bndcfgu register.
These calls fail if the CPU or kernel does not support MPX.
Kernel support for MPX is enabled via the CONFIG_X86_INTEL_MPX
configuration option. You can check whether the CPU supports
MPX by looking for the mpx CPUID bit, like with the following
command:
cat /proc/cpuinfo | grep ' mpx '
A thread may not switch in or out of long (64-bit) mode while
MPX is enabled.
All threads in a process are affected by these calls.
The child of a fork(2) inherits the state of MPX management.
During execve(2), MPX management is reset to a state as if
PR_MPX_DISABLE_MANAGEMENT had been called.
For further information on Intel MPX, see the kernel source
file Documentation/x86/intel_mpx.txt.
Due to a lack of toolchain support, PR_MPX_ENABLE_MANAGEMENT
and PR_MPX_DISABLE_MANAGEMENT are not supported in Linux 5.4
and later.
PR_SET_NAME (since Linux 2.6.9)
Set the name of the calling thread, using the value in the
location pointed to by (char *) arg2. The name can be up to
16 bytes long, including the terminating null byte. (If the
length of the string, including the terminating null byte,
exceeds 16 bytes, the string is silently truncated.) 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 (see
proc(5)), where [tid] is the thread ID of the calling thread,
as returned by gettid(2).
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.
PR_SET_NO_NEW_PRIVS (since Linux 3.5)
Set the calling thread's no_new_privs attribute 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 mode bits, and file capabilities
non-functional). Once set, the no_new_privs attribute cannot
be unset. The setting of this attribute is inherited by chil‐
dren created by fork(2) and clone(2), and preserved across
execve(2).
Since Linux 4.10, the value of a thread's no_new_privs
attribute can be viewed via the NoNewPrivs field in the
/proc/[pid]/status file.
For more information, see the kernel source file Documenta‐
tion/userspace-api/no_new_privs.rst (or Documenta‐
tion/prctl/no_new_privs.txt before Linux 4.13). See also
seccomp(2).
PR_GET_NO_NEW_PRIVS (since Linux 3.5)
Return (as the function result) the value of the no_new_privs
attribute for the calling thread. A value of 0 indicates the
regular execve(2) behavior. A value of 1 indicates execve(2)
will operate in the privilege-restricting mode described
above.
PR_PAC_RESET_KEYS (since Linux 5.0, only on arm64)
Securely reset the thread's pointer authentication keys to
fresh random values generated by the kernel.
The set of keys to be reset is specified by arg2, which must
be a logical OR of zero or more of the following:
PR_PAC_APIAKEY
instruction authentication key A
PR_PAC_APIBKEY
instruction authentication key B
PR_PAC_APDAKEY
data authentication key A
PR_PAC_APDBKEY
data authentication key B
PR_PAC_APGAKEY
generic authentication “A” key.
(Yes folks, there really is no generic B key.)
As a special case, if arg2 is zero, then all the keys are
reset. Since new keys could be added in future, this is the
recommended way to completely wipe the existing keys when
establishing a clean execution context. Note that there is no
need to use PR_PAC_RESET_KEYS in preparation for calling
execve(2), since execve(2) resets all the pointer authentica‐
tion keys.
The remaining arguments arg3, arg4, and arg5 must all be zero.
If the arguments are invalid, and in particular if arg2 con‐
tains set bits that are unrecognized or that correspond to a
key not available on this platform, then the call fails with
error EINVAL.
Warning: Because the compiler or run-time environment may be
using some or all of the keys, a successful PR_PAC_RESET_KEYS
may crash the calling process. The conditions for using it
safely are complex and system-dependent. Don't use it unless
you know what you are doing.
For more information, see the kernel source file Documenta‐
tion/arm64/pointer-authentication.rst (or Documenta‐
tion/arm64/pointer-authentication.txt before Linux 5.3).
PR_SET_PDEATHSIG (since Linux 2.1.57)
Set the parent-death signal of the calling process to arg2
(either a signal value in the range 1..NSIG-1, or 0 to clear).
This is the signal that the calling process will get when its
parent dies.
Warning: the "parent" in this case is considered to be the
thread that created this process. In other words, the signal
will be sent when that thread terminates (via, for example,
pthread_exit(3)), rather than after all of the threads in the
parent process terminate.
The parent-death signal is sent upon subsequent termination of
the parent thread and also upon termination of each subreaper
process (see the description of PR_SET_CHILD_SUBREAPER above)
to which the caller is subsequently reparented. If the parent
thread and all ancestor subreapers have already terminated by
the time of the PR_SET_PDEATHSIG operation, then no parent-
death signal is sent to the caller.
The parent-death signal is process-directed (see signal(7))
and, if the child installs a handler using the sigaction(2)
SA_SIGINFO flag, the si_pid field of the siginfo_t argument of
the handler contains the PID of the terminating parent
process.
The parent-death signal setting is cleared for the child of a
fork(2). It is also (since Linux 2.4.36 / 2.6.23) cleared
when executing a set-user-ID or set-group-ID binary, or a
binary that has associated capabilities (see capabilities(7));
otherwise, this value is preserved across execve(2). The par‐
ent-death signal setting is also cleared upon changes to any
of the following thread credentials: effective user ID, effec‐
tive group ID, filesystem user ID, or filesystem group ID.
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
ancestor. 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/admin-guide/LSM/Yama.rst (or Documentation/secu‐
rity/Yama.txt before Linux 4.13).
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 more recent
seccomp(2) system call provides a superset of the functional‐
ity of PR_SET_SECCOMP.
The seccomp mode is selected 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) (but not exit_group(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 oper‐
ation is available only if the kernel is configured with CON‐
FIG_SECCOMP enabled.
With arg2 set to SECCOMP_MODE_FILTER (since Linux 3.5), the
system 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 sys‐
tem 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 sec‐
comp mode is inherited by children created by fork(2); if
execve(2) is permitted, then the seccomp mode is preserved
across execve(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/userspace-api/seccomp_filter.rst (or Documenta‐
tion/prctl/seccomp_filter.txt before Linux 4.13).
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 computing 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; otherwise, the process is killed with a
SIGKILL signal. This operation is available only if the ker‐
nel is configured with CONFIG_SECCOMP enabled.
Since Linux 3.8, the Seccomp field of the /proc/[pid]/status
file provides a method of obtaining the same information,
without the risk that the process is killed; see proc(5).
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_GET_SPECULATION_CTRL (since Linux 4.17)
Return (as the function result) the state of the speculation
misfeature specified in arg2. Currently, the only permitted
value for this argument is PR_SPEC_STORE_BYPASS (otherwise the
call fails with the error ENODEV).
The return value uses bits 0-3 with the following meaning:
PR_SPEC_PRCTL
Mitigation can be controlled per thread by PR_SET_SPEC‐
ULATION_CTRL.
PR_SPEC_ENABLE
The speculation feature is enabled, mitigation is dis‐
abled.
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 specu‐
lation misfeature.
If PR_SPEC_PRCTL is set, then per-thread control of the miti‐
gation is available. If not set, prctl() for the speculation
misfeature will fail.
The arg3, arg4, and arg5 arguments must be specified as 0;
otherwise the call fails with the error EINVAL.
PR_SET_SPECULATION_CTRL (since Linux 4.17)
Sets the state of the speculation misfeature specified in
arg2. The speculation-misfeature settings are per-thread
attributes.
Currently, arg2 must be one of:
PR_SPEC_STORE_BYPASS
Set the state of the speculative store bypass misfea‐
ture.
PR_SPEC_INDIRECT_BRANCH (since Linux 4.20)
Set the state of the indirect branch speculation mis‐
feature.
If arg2 does not have one of the above values, then the call
fails with the error ENODEV.
The arg3 argument is used to hand in the control value, which
is one of the following:
PR_SPEC_ENABLE
The speculation feature is enabled, mitigation is dis‐
abled.
PR_SPEC_DISABLE
The speculation feature is disabled, mitigation is
enabled.
PR_SPEC_FORCE_DISABLE
Same as PR_SPEC_DISABLE, but cannot be undone. A sub‐
sequent prctl(arg2, PR_SPEC_ENABLE) with the same value
for arg2 will fail with the error EPERM.
PR_SPEC_DISABLE_NOEXEC (since Linux 5.1)
Same as PR_SPEC_DISABLE, but the state will be cleared
on execve(2). Currently only supported for arg2 equal
to PR_SPEC_STORE_BYPASS.
Any unsupported value in arg3 will result in the call failing
with the error ERANGE.
The arg4 and arg5 arguments must be specified as 0; otherwise
the call fails with the error EINVAL.
The speculation feature can also be controlled by the
spec_store_bypass_disable boot parameter. This parameter may
enforce a read-only policy which will result in the prctl()
call failing with the error ENXIO. For further details, see
the kernel source file Documentation/admin-guide/kernel-param‐
eters.txt.
PR_SVE_SET_VL (since Linux 4.15, only on arm64)
Configure the thread's SVE vector length, as specified by
(int) arg2. Arguments arg3, arg4, and arg5 are ignored.
The bits of arg2 corresponding to PR_SVE_VL_LEN_MASK must be
set to the desired vector length in bytes. This is inter‐
preted as an upper bound: the kernel will select the greatest
available vector length that does not exceed the value speci‐
fied. In particular, specifying SVE_VL_MAX (defined in
<asm/sigcontext.h>) for the PR_SVE_VL_LEN_MASK bits requests
the maximum supported vector length.
In addition, the other bits of arg2 must be set to one of the
following combinations of flags:
0 Perform the change immediately. At the next execve(2)
in the thread, the vector length will be reset to the
value configured in /proc/sys/abi/sve_default_vec‐
tor_length.
PR_SVE_VL_INHERIT
Perform the change immediately. Subsequent execve(2)
calls will preserve the new vector length.
PR_SVE_SET_VL_ONEXEC
Defer the change, so that it is performed at the next
execve(2) in the thread. Further execve(2) calls will
reset the vector length to the value configured in
/proc/sys/abi/sve_default_vector_length.
PR_SVE_SET_VL_ONEXEC | PR_SVE_VL_INHERIT
Defer the change, so that it is performed at the next
execve(2) in the thread. Further execve(2) calls will
preserve the new vector length.
In all cases, any previously pending deferred change is can‐
celed.
The call fails with error EINVAL if SVE is not supported on
the platform, if arg2 is unrecognized or invalid, or the value
in the bits of arg2 corresponding to PR_SVE_VL_LEN_MASK is
outside the range SVE_VL_MIN..SVE_VL_MAX or is not a multiple
of 16.
On success, a nonnegative value is returned that describes the
selected configuration. If PR_SVE_SET_VL_ONEXEC was included
in arg2, then the configuration described by the return value
will take effect at the next execve(). Otherwise, the config‐
uration is already in effect when the PR_SVE_SET_VL call
returns. In either case, the value is encoded in the same way
as the return value of PR_SVE_GET_VL. Note that there is no
explicit flag in the return value corresponding to
PR_SVE_SET_VL_ONEXEC.
The configuration (including any pending deferred change) is
inherited across fork(2) and clone(2).
For more information, see the kernel source file Documenta‐
tion/arm64/sve.rst (or Documentation/arm64/sve.txt before
Linux 5.3).
Warning: Because the compiler or run-time environment may be
using SVE, using this call without the PR_SVE_SET_VL_ONEXEC
flag may crash the calling process. The conditions for using
it safely are complex and system-dependent. Don't use it
unless you really know what you are doing.
PR_SVE_GET_VL (since Linux 4.15, only on arm64)
Get the thread's current SVE vector length configuration.
Arguments arg2, arg3, arg4, and arg5 are ignored.
Provided that the kernel and platform support SVE, this opera‐
tion always succeeds, returning a nonnegative value that
describes the current configuration. The bits corresponding
to PR_SVE_VL_LEN_MASK contain the currently configured vector
length in bytes. The bit corresponding to PR_SVE_VL_INHERIT
indicates whether the vector length will be inherited across
execve(2).
Note that there is no way to determine whether there is a
pending vector length change that has not yet taken effect.
For more information, see the kernel source file Documenta‐
tion/arm64/sve.rst (or Documentation/arm64/sve.txt before
Linux 5.3).
PR_SET_TAGGED_ADDR_CTRL (since Linux 5.4, only on arm64)
Controls support for passing tagged user-space addresses to
the kernel (i.e., addresses where bits 56—63 are not all
zero).
The level of support is selected by arg2, which can be one of
the following:
0 Addresses that are passed for the purpose of being
dereferenced by the kernel must be untagged.
PR_TAGGED_ADDR_ENABLE
Addresses that are passed for the purpose of being
dereferenced by the kernel may be tagged, with the
exceptions summarized below.
The remaining arguments arg3, arg4, and arg5 must all be zero.
On success, the mode specified in arg2 is set for the calling
thread and the return value is 0. If the arguments are
invalid, the mode specified in arg2 is unrecognized, or if
this feature is unsupported by the kernel or disabled via
/proc/sys/abi/tagged_addr_disabled, the call fails with the
error EINVAL.
In particular, if prctl(PR_SET_TAGGED_ADDR_CTRL, 0, 0, 0, 0)
fails with EINVAL, then all addresses passed to the kernel
must be untagged.
Irrespective of which mode is set, addresses passed to certain
interfaces must always be untagged:
· brk(2), mmap(2), shmat(2), shmdt(2), and the new_address
argument of mremap(2).
(Prior to Linux 5.6 these accepted tagged addresses, but the
behaviour may not be what you expect. Don't rely on it.)
· ‘polymorphic’ interfaces that accept pointers to arbitrary
types cast to a void * or other generic type, specifically
prctl(2), ioctl(2), and in general setsockopt(2) (only cer‐
tain specific setsockopt(2) options allow tagged addresses).
This list of exclusions may shrink when moving from one kernel
version to a later kernel version. While the kernel may make
some guarantees for backwards compatibility reasons, for the
purposes of new software the effect of passing tagged
addresses to these interfaces is unspecified.
The mode set by this call is inherited across fork(2) and
clone(2). The mode is reset by execve(2) to 0 (i.e., tagged
addresses not permitted in the user/kernel ABI).
For more information, see the kernel source file Documenta‐
tion/arm64/tagged-address-abi.rst.
Warning: This call is primarily intended for use by the run-
time environment. A successful PR_SET_TAGGED_ADDR_CTRL call
elsewhere may crash the calling process. The conditions for
using it safely are complex and system-dependent. Don't use
it unless you know what you are doing.
PR_GET_TAGGED_ADDR_CTRL (since Linux 5.4, only on arm64)
Returns the current tagged address mode for the calling
thread.
Arguments arg2, arg3, arg4, and arg5 must all be zero.
If the arguments are invalid or this feature is disabled or
unsupported by the kernel, the call fails with EINVAL. In
particular, if prctl(PR_GET_TAGGED_ADDR_CTRL, 0, 0, 0, 0)
fails with EINVAL, then this feature is definitely either
unsupported, or disabled via /proc/sys/abi/tagged_addr_dis‐
abled. In this case, all addresses passed to the kernel must
be untagged.
Otherwise, the call returns a nonnegative value describing the
current tagged address mode, encoded in the same way as the
arg2 argument of PR_SET_TAGGED_ADDR_CTRL.
For more information, see the kernel source file Documenta‐
tion/arm64/tagged-address-abi.rst.
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
(retaining the 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 perfor‐
mance counters attached to the calling process.
Originally called PR_TASK_PERF_COUNTERS_ENABLE; renamed in
Linux 2.6.32.
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, other‐
wise it is cleared. Setting this flag provides a method for
disabling transparent huge pages for jobs where the code can‐
not be modified, and using a malloc hook with madvise(2) is
not an option (i.e., statically allocated data). The setting
of the "THP disable" 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 (as 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)
Return 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. Note that since the prctl() system call does
not have a compat implementation for the AMD64 x32 and MIPS
n32 ABIs, and the kernel writes out a pointer using the ker‐
nel's pointer size, this operation expects a user-space buffer
of 8 (not 4) bytes on these ABIs.
PR_SET_TIMERSLACK (since Linux 2.6.28)
Each thread has two associated timer slack values: a "default"
value, and a "current" value. This operation sets the "cur‐
rent" timer slack value for the calling thread. arg2 is an
unsigned long value, then maximum "current" value is ULONG_MAX
and the minimum "current" value is 1. If the nanosecond value
supplied in arg2 is greater than zero, then the "current"
value is set to this value. If arg2 is equal to zero, the
"current" timer slack is reset to the thread's "default" timer
slack value.
The "current" 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,
including 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)).
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 value is inherited by a child created via
fork(2), and is preserved across execve(2).
Since Linux 4.6, the "current" timer slack value of any
process can be examined and changed via the file
/proc/[pid]/timerslack_ns. See proc(5).
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)
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)
Return (as the function result) which process timing method is
currently in use.
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; sh, since Linux 2.6.34; tile, since Linux 3.12) Set
unaligned 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. Alpha also supports an additional flag with the value
of 4 and no corresponding named constant, which instructs ker‐
nel to not fix up unaligned accesses (it is analogous to pro‐
viding the UAC_NOFIX flag in SSI_NVPAIRS operation of the set‐
sysinfo() system call on Tru64).
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 (unsigned int *) arg2.
On success, PR_CAP_AMBIENT+PR_CAP_AMBIENT_IS_SET, PR_CAPBSET_READ,
PR_GET_DUMPABLE, PR_GET_FP_MODE, PR_GET_IO_FLUSHER, PR_GET_KEEPCAPS,
PR_MCE_KILL_GET, PR_GET_NO_NEW_PRIVS, PR_GET_SECUREBITS,
PR_GET_SPECULATION_CTRL, PR_SVE_GET_VL, PR_SVE_SET_VL,
PR_GET_TAGGED_ADDR_CTRL, PR_GET_THP_DISABLE, PR_GET_TIMING,
PR_GET_TIMERSLACK, 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
appropriately.
EACCES option is PR_SET_SECCOMP and arg2 is SECCOMP_MODE_FILTER, but
the process does not have the CAP_SYS_ADMIN capability or has
not set the no_new_privs attribute (see the discussion of
PR_SET_NO_NEW_PRIVS above).
EACCES option is PR_SET_MM, and arg3 is PR_SET_MM_EXE_FILE, the file
is not executable.
EBADF option is PR_SET_MM, arg3 is PR_SET_MM_EXE_FILE, and the file
descriptor passed in arg4 is not valid.
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.
EFAULT arg2 is an invalid address.
EFAULT option is PR_SET_SECCOMP, arg2 is SECCOMP_MODE_FILTER, the
system was built with CONFIG_SECCOMP_FILTER, and arg3 is an
invalid address.
EINVAL The value of option is not recognized, or not supported on
this system.
EINVAL option is PR_MCE_KILL or PR_MCE_KILL_GET or PR_SET_MM, and
unused 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_SECCOMP, arg2 is SECCOMP_MODE_FILTER, and the
kernel was not configured with CONFIG_SECCOMP_FILTER.
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
corresponding 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
specifies 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
number.
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.
EINVAL option is PR_CAP_AMBIENT and an unused argument (arg4, arg5,
or, in the case of PR_CAP_AMBIENT_CLEAR_ALL, arg3) is nonzero;
or arg2 has an invalid value; or arg2 is PR_CAP_AMBIENT_LOWER,
PR_CAP_AMBIENT_RAISE, or PR_CAP_AMBIENT_IS_SET and arg3 does
not specify a valid capability.
EINVAL option was PR_GET_SPECULATION_CTRL or PR_SET_SPECULATION_CTRL
and unused arguments to prctl() are not 0. EINVAL option is
PR_PAC_RESET_KEYS and the arguments are invalid or
unsupported. See the description of PR_PAC_RESET_KEYS above
for details.
EINVAL option is PR_SVE_SET_VL and the arguments are invalid or
unsupported, or SVE is not available on this platform. See
the description of PR_SVE_SET_VL above for details.
EINVAL option is PR_SVE_GET_VL and SVE is not available on this
platform.
EINVAL option is PR_SET_TAGGED_ADDR_CTRL and the arguments are
invalid or unsupported. See the description of
PR_SET_TAGGED_ADDR_CTRL above for details.
EINVAL option is PR_GET_TAGGED_ADDR_CTRL and the arguments are
invalid or unsupported. See the description of
PR_GET_TAGGED_ADDR_CTRL above for details.
ENODEV option was PR_SET_SPECULATION_CTRL the kernel or CPU does not
support the requested speculation misfeature.
ENXIO option was PR_MPX_ENABLE_MANAGEMENT or
PR_MPX_DISABLE_MANAGEMENT and the kernel or the CPU does not
support MPX management. Check that the kernel and processor
have MPX support.
ENXIO option was PR_SET_SPECULATION_CTRL implies that the control of
the selected speculation misfeature is not possible. See
PR_GET_SPECULATION_CTRL for the bit fields to determine which
option is available.
EOPNOTSUPP
option is PR_SET_FP_MODE and arg2 has an invalid or
unsupported value.
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_SPECULATION_CTRL wherein the speculation was
disabled with PR_SPEC_FORCE_DISABLE and caller tried to enable
it again.
EPERM option is PR_SET_KEEPCAPS, and the caller's
SECBIT_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.
EPERM option is PR_CAP_AMBIENT and arg2 is PR_CAP_AMBIENT_RAISE, but
either the capability specified in arg3 is not present in the
process's permitted and inheritable capability sets, or the
PR_CAP_AMBIENT_LOWER securebit has been set.
ERANGE option was PR_SET_SPECULATION_CTRL and arg3 is not
PR_SPEC_ENABLE, PR_SPEC_DISABLE, PR_SPEC_FORCE_DISABLE, nor
PR_SPEC_DISABLE_NOEXEC.
The prctl() system call was introduced in Linux 2.1.57.
This call is Linux-specific. 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 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 max‐
imum stack size, and so on.
signal(2), core(5)
This page is part of release 5.08 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
https://www.kernel.org/doc/man-pages/.
Linux 2020-08-13 PRCTL(2)
Pages that refer to this page: capsh(1) , setpriv(1) , systemd-nspawn(1) , arch_prctl(2) , execve(2) , exit(2) , _exit(2) , _Exit(2) , fork(2) , getpid(2) , getppid(2) , madvise(2) , perf_event_open(2) , prctl(2) , ptrace(2) , seccomp(2) , syscalls(2) , wait(2) , waitid(2) , waitpid(2) , capng_change_id(3) , capng_lock(3) , do_tracepoint(3) , exit(3) , lttng-ust(3) , pthread_getname_np(3) , pthread_setname_np(3) , sd_event_add_time(3) , sd_event_source_get_time(3) , sd_event_source_get_time_accuracy(3) , sd_event_source_get_time_clock(3) , sd_event_source_set_time(3) , sd_event_source_set_time_accuracy(3) , sd_event_time_handler_t(3) , tracepoint(3) , tracepoint_enabled(3) , core(5) , proc(5) , procfs(5) , system.conf.d(5) , systemd.exec(5) , systemd-system.conf(5) , systemd.timer(5) , systemd-user.conf(5) , user.conf.d(5) , capabilities(7) , credentials(7) , environ(7) , pid_namespaces(7) , time(7) , fuse(8) , mount.fuse3(8)
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