mirror of
https://sourceware.org/git/glibc.git
synced 2024-12-12 22:30:12 +00:00
148 lines
4.3 KiB
C
148 lines
4.3 KiB
C
/* Determine directory for shm/sem files. Linux version.
|
|
Copyright (C) 2000-2020 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
|
|
<https://www.gnu.org/licenses/>. */
|
|
|
|
#include "shm-directory.h"
|
|
|
|
#include <errno.h>
|
|
#include <mntent.h>
|
|
#include <paths.h>
|
|
#include <stdio.h>
|
|
#include <string.h>
|
|
#include <sys/statfs.h>
|
|
#include <libc-lock.h>
|
|
#include "linux_fsinfo.h"
|
|
|
|
|
|
/* Mount point of the shared memory filesystem. */
|
|
static struct
|
|
{
|
|
char *dir;
|
|
size_t dirlen;
|
|
} mountpoint;
|
|
|
|
/* This is the default directory. */
|
|
static const char defaultdir[] = "/dev/shm/";
|
|
|
|
/* Protect the `mountpoint' variable above. */
|
|
__libc_once_define (static, once);
|
|
|
|
|
|
/* Determine where the shmfs is mounted (if at all). */
|
|
static void
|
|
where_is_shmfs (void)
|
|
{
|
|
char buf[512];
|
|
struct statfs f;
|
|
struct mntent resmem;
|
|
struct mntent *mp;
|
|
FILE *fp;
|
|
|
|
/* The canonical place is /dev/shm. This is at least what the
|
|
documentation tells everybody to do. */
|
|
if (__statfs (defaultdir, &f) == 0 && (f.f_type == SHMFS_SUPER_MAGIC
|
|
|| f.f_type == RAMFS_MAGIC))
|
|
{
|
|
/* It is in the normal place. */
|
|
mountpoint.dir = (char *) defaultdir;
|
|
mountpoint.dirlen = sizeof (defaultdir) - 1;
|
|
|
|
return;
|
|
}
|
|
|
|
/* OK, do it the hard way. Look through the /proc/mounts file and if
|
|
this does not exist through /etc/fstab to find the mount point. */
|
|
fp = __setmntent ("/proc/mounts", "r");
|
|
if (__glibc_unlikely (fp == NULL))
|
|
{
|
|
fp = __setmntent (_PATH_MNTTAB, "r");
|
|
if (__glibc_unlikely (fp == NULL))
|
|
/* There is nothing we can do. Blind guesses are not helpful. */
|
|
return;
|
|
}
|
|
|
|
/* Now read the entries. */
|
|
while ((mp = __getmntent_r (fp, &resmem, buf, sizeof buf)) != NULL)
|
|
/* The original name is "shm" but this got changed in early Linux
|
|
2.4.x to "tmpfs". */
|
|
if (strcmp (mp->mnt_type, "tmpfs") == 0
|
|
|| strcmp (mp->mnt_type, "shm") == 0)
|
|
{
|
|
/* Found it. There might be more than one place where the
|
|
filesystem is mounted but one is enough for us. */
|
|
size_t namelen;
|
|
|
|
/* First make sure this really is the correct entry. At least
|
|
some versions of the kernel give wrong information because
|
|
of the implicit mount of the shmfs for SysV IPC. */
|
|
if (__statfs (mp->mnt_dir, &f) != 0 || (f.f_type != SHMFS_SUPER_MAGIC
|
|
&& f.f_type != RAMFS_MAGIC))
|
|
continue;
|
|
|
|
namelen = strlen (mp->mnt_dir);
|
|
|
|
if (namelen == 0)
|
|
/* Hum, maybe some crippled entry. Keep on searching. */
|
|
continue;
|
|
|
|
mountpoint.dir = (char *) malloc (namelen + 2);
|
|
if (mountpoint.dir != NULL)
|
|
{
|
|
char *cp = __mempcpy (mountpoint.dir, mp->mnt_dir, namelen);
|
|
if (cp[-1] != '/')
|
|
*cp++ = '/';
|
|
*cp = '\0';
|
|
mountpoint.dirlen = cp - mountpoint.dir;
|
|
}
|
|
|
|
break;
|
|
}
|
|
|
|
/* Close the stream. */
|
|
__endmntent (fp);
|
|
}
|
|
|
|
|
|
const char *
|
|
__shm_directory (size_t *len)
|
|
{
|
|
/* Determine where the shmfs is mounted. */
|
|
__libc_once (once, where_is_shmfs);
|
|
|
|
/* If we don't know the mount points there is nothing we can do. Ever. */
|
|
if (__glibc_unlikely (mountpoint.dir == NULL))
|
|
{
|
|
__set_errno (ENOSYS);
|
|
return NULL;
|
|
}
|
|
|
|
*len = mountpoint.dirlen;
|
|
return mountpoint.dir;
|
|
}
|
|
#if IS_IN (libpthread)
|
|
hidden_def (__shm_directory)
|
|
|
|
/* Make sure the table is freed if we want to free everything before
|
|
exiting. */
|
|
void
|
|
__shm_directory_freeres (void)
|
|
{
|
|
if (mountpoint.dir != defaultdir)
|
|
free (mountpoint.dir);
|
|
}
|
|
#endif
|