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128 lines
3.3 KiB
C
128 lines
3.3 KiB
C
/* Get file-specific information about a file. Linux version.
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Copyright (C) 2003-2025 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <assert.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <stdlib.h>
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#include <sysdep.h>
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#include <time.h>
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#include <unistd.h>
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#include <sys/resource.h>
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#include <sys/param.h>
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#include <not-cancel.h>
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#include <ldsodefs.h>
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#include <sysconf-sigstksz.h>
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/* Legacy value of ARG_MAX. The macro is now not defined since the
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actual value varies based on the stack size. */
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#define legacy_ARG_MAX 131072
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/* Newer kernels (4.13) limit the maximum command line arguments lengths to
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6MiB. */
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#define maximum_ARG_MAX (6 * 1024 * 1024)
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static long int posix_sysconf (int name);
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/* Get the value of the system variable NAME. */
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long int
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__sysconf (int name)
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{
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const char *procfname = NULL;
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switch (name)
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{
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case _SC_MONOTONIC_CLOCK:
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case _SC_CPUTIME:
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case _SC_THREAD_CPUTIME:
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return _POSIX_VERSION;
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case _SC_ARG_MAX:
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{
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struct rlimit rlimit;
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/* Use getrlimit to get the stack limit. */
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if (__getrlimit (RLIMIT_STACK, &rlimit) == 0)
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{
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const long int limit = MAX (legacy_ARG_MAX, rlimit.rlim_cur / 4);
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return MIN (limit, maximum_ARG_MAX);
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}
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return legacy_ARG_MAX;
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}
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case _SC_NGROUPS_MAX:
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/* Try to read the information from the /proc/sys/kernel/ngroups_max
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file. */
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procfname = "/proc/sys/kernel/ngroups_max";
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break;
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case _SC_SIGQUEUE_MAX:
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{
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struct rlimit rlimit;
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if (__getrlimit (RLIMIT_SIGPENDING, &rlimit) == 0)
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return rlimit.rlim_cur;
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/* The /proc/sys/kernel/rtsig-max file contains the answer. */
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procfname = "/proc/sys/kernel/rtsig-max";
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}
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break;
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case _SC_MINSIGSTKSZ:
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assert (GLRO(dl_minsigstacksize) != 0);
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return GLRO(dl_minsigstacksize);
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case _SC_SIGSTKSZ:
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return sysconf_sigstksz ();
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default:
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break;
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}
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if (procfname != NULL)
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{
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int fd = __open_nocancel (procfname, O_RDONLY | O_CLOEXEC);
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if (fd != -1)
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{
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/* This is more than enough, the file contains a single integer. */
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char buf[32];
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ssize_t n;
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n = TEMP_FAILURE_RETRY (__read_nocancel (fd, buf, sizeof (buf) - 1));
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__close_nocancel_nostatus (fd);
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if (n > 0)
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{
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/* Terminate the string. */
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buf[n] = '\0';
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char *endp;
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long int res = strtol (buf, &endp, 10);
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if (endp != buf && (*endp == '\0' || *endp == '\n'))
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return res;
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}
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}
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}
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return posix_sysconf (name);
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}
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/* Now the POSIX version. */
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#undef __sysconf
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#define __sysconf static posix_sysconf
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#include <sysdeps/posix/sysconf.c>
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