prctl — operations on a process
#include <sys/prctl.h>
int
prctl( |
int | option, |
unsigned long | arg2, | |
unsigned long | arg3, | |
unsigned long | arg4, | |
unsigned long | arg5) ; |
prctl
() is called with a
first argument describing what to do (with values defined in
<linux/prctl.h
>), and
further parameters with a significance depending on the first
one. The first argument can be:
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 upon a fork(2).
PR_GET_PDEATHSIG
(Since Linux 2.3.15) Read the current value of the
parent process death signal into the (int *) arg2
.
PR_SET_DUMPABLE
(Since Linux 2.3.20) Set the state of the flag
determining whether core dumps are produced for this
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 various 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).)
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_KEEPCAPS
(Since Linux 2.2.18) Set the state of the process's
"keep capabilities" flag, which determines whether the
process's effective and permitted capability sets are
cleared when a change is made to the process's user IDs
such that the process's real UID, effective UID, and
saved set-user-ID all become non-zero when at least one
of them previously had the value 0. (By default, these
credential sets are cleared). arg2
must be either 0
(capabilities are cleared) or 1 (capabilities are
kept).
PR_GET_KEEPCAPS
(Since Linux 2.2.18) Return (as the function result) the current state of the calling process's "keep capabilities" flag.
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_GET_TIMING
(Since Linux 2.6.0-test4) Return (as the function result) which process timing method is currently in use.
PR_SET_NAME
(Since Linux 2.6.9) Set the process name for the
calling process to arg2
.
PR_GET_NAME
(Since Linux 2.6.11) Get the process name for the
calling process from arg2
.
PR_GET_ENDIAN
(Since Linux 2.6.18, PowerPC only) Return the endian-ness of the calling process.
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_SET_UNALIGN
(Since Linux 2.3.48, only on parisc and ia64) 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.
PR_GET_UNALIGN
(Since Linux 2.3.48, only on parisc and ia64) Get
unaligned access control bits from 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
instead.
PR_GET_FPEMU
(Since Linux 2.4.18, 2.5.9, only on ia64) Get
floating-point emulation control bits from 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
non-recoverable 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) Get
floating-point exception mode from arg2
.
PR_GET_DUMPABLE
and
PR_GET_KEEPCAPS
return 0 or 1
on success. All other option
values return 0 on
success. On error, −1 is returned, and errno
is set appropriately.
The value of option
is not recognized,
or it is PR_SET_PDEATHSIG
and arg2
is not
zero or a signal number.
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 maximum stack size, etc.
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