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/* Get file-specific information about a file. Linux version.
Copyright (C) 2003-2019 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <sysdep.h>
#include <time.h>
#include <unistd.h>
#include <sys/resource.h>
#include <sys/param.h>
#include <not-cancel.h>
#include <ldsodefs.h>
/* Legacy value of ARG_MAX. The macro is now not defined since the
actual value varies based on the stack size. */
#define legacy_ARG_MAX 131072
static long int posix_sysconf (int name);
#ifndef HAS_CPUCLOCK
static long int
has_cpuclock (int name)
{
# if defined __NR_clock_getres || HP_TIMING_AVAIL
/* If we have HP_TIMING, we will fall back on that if the system
call does not work, so we support it either way. */
# if !HP_TIMING_AVAIL
/* Check using the clock_getres system call. */
struct timespec ts;
INTERNAL_SYSCALL_DECL (err);
int r = INTERNAL_SYSCALL (clock_getres, err, 2,
(name == _SC_CPUTIME
? CLOCK_PROCESS_CPUTIME_ID
: CLOCK_THREAD_CPUTIME_ID),
&ts);
if (INTERNAL_SYSCALL_ERROR_P (r, err))
return -1;
# endif
return _POSIX_VERSION;
# else
return -1;
# endif
}
# define HAS_CPUCLOCK(name) has_cpuclock (name)
#endif
/* Get the value of the system variable NAME. */
long int
__sysconf (int name)
{
const char *procfname = NULL;
switch (name)
{
struct rlimit rlimit;
#ifdef __NR_clock_getres
case _SC_MONOTONIC_CLOCK:
/* Check using the clock_getres system call. */
{
struct timespec ts;
INTERNAL_SYSCALL_DECL (err);
int r;
r = INTERNAL_SYSCALL (clock_getres, err, 2, CLOCK_MONOTONIC, &ts);
return INTERNAL_SYSCALL_ERROR_P (r, err) ? -1 : _POSIX_VERSION;
}
#endif
case _SC_CPUTIME:
case _SC_THREAD_CPUTIME:
return HAS_CPUCLOCK (name);
case _SC_ARG_MAX:
/* Use getrlimit to get the stack limit. */
if (__getrlimit (RLIMIT_STACK, &rlimit) == 0)
return MAX (legacy_ARG_MAX, rlimit.rlim_cur / 4);
return legacy_ARG_MAX;
case _SC_NGROUPS_MAX:
/* Try to read the information from the /proc/sys/kernel/ngroups_max
file. */
procfname = "/proc/sys/kernel/ngroups_max";
break;
case _SC_SIGQUEUE_MAX:
if (__getrlimit (RLIMIT_SIGPENDING, &rlimit) == 0)
return rlimit.rlim_cur;
/* The /proc/sys/kernel/rtsig-max file contains the answer. */
procfname = "/proc/sys/kernel/rtsig-max";
break;
default:
break;
}
if (procfname != NULL)
{
int fd = __open_nocancel (procfname, O_RDONLY);
if (fd != -1)
{
/* This is more than enough, the file contains a single integer. */
char buf[32];
ssize_t n;
n = TEMP_FAILURE_RETRY (__read_nocancel (fd, buf, sizeof (buf) - 1));
__close_nocancel_nostatus (fd);
if (n > 0)
{
/* Terminate the string. */
buf[n] = '\0';
char *endp;
long int res = strtol (buf, &endp, 10);
if (endp != buf && (*endp == '\0' || *endp == '\n'))
return res;
}
}
}
return posix_sysconf (name);
}
/* Now the POSIX version. */
#undef __sysconf
#define __sysconf static posix_sysconf
#include <sysdeps/posix/sysconf.c>
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