glibc/sysdeps/unix/sysv/linux/pathconf.c

324 lines
7.6 KiB
C

/* Get file-specific information about a file. Linux version.
Copyright (C) 1991-2014 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 <mntent.h>
#include <stdio_ext.h>
#include <string.h>
#include <unistd.h>
#include <sys/sysmacros.h>
#include "pathconf.h"
#include "linux_fsinfo.h"
#include <not-cancel.h>
static long int posix_pathconf (const char *file, int name);
/* Define this first, so it can be inlined. */
#define __pathconf static posix_pathconf
#include <sysdeps/posix/pathconf.c>
/* Get file-specific information about FILE. */
long int
__pathconf (const char *file, int name)
{
struct statfs fsbuf;
switch (name)
{
case _PC_LINK_MAX:
return __statfs_link_max (__statfs (file, &fsbuf), &fsbuf, file, -1);
case _PC_FILESIZEBITS:
return __statfs_filesize_max (__statfs (file, &fsbuf), &fsbuf);
case _PC_2_SYMLINKS:
return __statfs_symlinks (__statfs (file, &fsbuf), &fsbuf);
case _PC_CHOWN_RESTRICTED:
return __statfs_chown_restricted (__statfs (file, &fsbuf), &fsbuf);
default:
return posix_pathconf (file, name);
}
}
static long int
distinguish_extX (const struct statfs *fsbuf, const char *file, int fd)
{
char buf[64];
char path[PATH_MAX];
struct stat64 st;
if ((file == NULL ? fstat64 (fd, &st) : stat64 (file, &st)) != 0)
/* Strange. The statfd call worked, but stat fails. Default to
the more pessimistic value. */
return EXT2_LINK_MAX;
__snprintf (buf, sizeof (buf), "/sys/dev/block/%u:%u",
gnu_dev_major (st.st_dev), gnu_dev_minor (st.st_dev));
ssize_t n = __readlink (buf, path, sizeof (path));
if (n != -1 && n < sizeof (path))
{
path[n] = '\0';
char *base = strdupa (basename (path));
__snprintf (path, sizeof (path), "/sys/fs/ext4/%s", base);
return __access (path, F_OK) == 0 ? EXT4_LINK_MAX : EXT2_LINK_MAX;
}
/* XXX Is there a better way to distinguish ext2/3 from ext4 than
iterating over the mounted filesystems and compare the device
numbers? */
FILE *mtab = __setmntent ("/proc/mounts", "r");
if (mtab == NULL)
mtab = __setmntent (_PATH_MOUNTED, "r");
/* By default be conservative. */
long int result = EXT2_LINK_MAX;
if (mtab != NULL)
{
struct mntent mntbuf;
char tmpbuf[1024];
/* No locking needed. */
(void) __fsetlocking (mtab, FSETLOCKING_BYCALLER);
while (__getmntent_r (mtab, &mntbuf, tmpbuf, sizeof (tmpbuf)))
{
if (strcmp (mntbuf.mnt_type, "ext2") != 0
&& strcmp (mntbuf.mnt_type, "ext3") != 0
&& strcmp (mntbuf.mnt_type, "ext4") != 0)
continue;
struct stat64 fsst;
if (stat64 (mntbuf.mnt_dir, &fsst) >= 0
&& st.st_dev == fsst.st_dev)
{
if (strcmp (mntbuf.mnt_type, "ext4") == 0)
result = EXT4_LINK_MAX;
break;
}
}
/* Close the file. */
__endmntent (mtab);
}
return result;
}
/* Used like: return statfs_link_max (__statfs (name, &buf), &buf); */
long int
__statfs_link_max (int result, const struct statfs *fsbuf, const char *file,
int fd)
{
if (result < 0)
{
if (errno == ENOSYS)
/* Not possible, return the default value. */
return LINUX_LINK_MAX;
/* Some error occured. */
return -1;
}
switch (fsbuf->f_type)
{
case EXT2_SUPER_MAGIC:
/* Unfortunately the kernel does not return a different magic number
for ext4. This would be necessary to easily detect etx4 since it
has a different LINK_MAX value. Therefore we have to find it out
the hard way. */
return distinguish_extX (fsbuf, file, fd);
case F2FS_SUPER_MAGIC:
return F2FS_LINK_MAX;
case MINIX_SUPER_MAGIC:
case MINIX_SUPER_MAGIC2:
return MINIX_LINK_MAX;
case MINIX2_SUPER_MAGIC:
case MINIX2_SUPER_MAGIC2:
return MINIX2_LINK_MAX;
case XENIX_SUPER_MAGIC:
return XENIX_LINK_MAX;
case SYSV4_SUPER_MAGIC:
case SYSV2_SUPER_MAGIC:
return SYSV_LINK_MAX;
case COH_SUPER_MAGIC:
return COH_LINK_MAX;
case UFS_MAGIC:
case UFS_CIGAM:
return UFS_LINK_MAX;
case REISERFS_SUPER_MAGIC:
return REISERFS_LINK_MAX;
case XFS_SUPER_MAGIC:
return XFS_LINK_MAX;
case LUSTRE_SUPER_MAGIC:
return LUSTRE_LINK_MAX;
default:
return LINUX_LINK_MAX;
}
}
/* Used like: return statfs_filesize_max (__statfs (name, &buf), &buf); */
long int
__statfs_filesize_max (int result, const struct statfs *fsbuf)
{
if (result < 0)
{
if (errno == ENOSYS)
/* Not possible, return the default value. */
return 32;
/* Some error occured. */
return -1;
}
switch (fsbuf->f_type)
{
case F2FS_SUPER_MAGIC:
return 256;
case BTRFS_SUPER_MAGIC:
return 255;
case EXT2_SUPER_MAGIC:
case UFS_MAGIC:
case UFS_CIGAM:
case REISERFS_SUPER_MAGIC:
case XFS_SUPER_MAGIC:
case SMB_SUPER_MAGIC:
case NTFS_SUPER_MAGIC:
case UDF_SUPER_MAGIC:
case JFS_SUPER_MAGIC:
case VXFS_SUPER_MAGIC:
case CGROUP_SUPER_MAGIC:
case LUSTRE_SUPER_MAGIC:
return 64;
case MSDOS_SUPER_MAGIC:
case JFFS_SUPER_MAGIC:
case JFFS2_SUPER_MAGIC:
case NCP_SUPER_MAGIC:
case ROMFS_SUPER_MAGIC:
return 32;
default:
return 32;
}
}
/* Used like: return statfs_link_max (__statfs (name, &buf), &buf); */
long int
__statfs_symlinks (int result, const struct statfs *fsbuf)
{
if (result < 0)
{
if (errno == ENOSYS)
/* Not possible, return the default value. */
return 1;
/* Some error occured. */
return -1;
}
switch (fsbuf->f_type)
{
case ADFS_SUPER_MAGIC:
case BFS_MAGIC:
case CRAMFS_MAGIC:
case DEVPTS_SUPER_MAGIC:
case EFS_SUPER_MAGIC:
case EFS_MAGIC:
case MSDOS_SUPER_MAGIC:
case NTFS_SUPER_MAGIC:
case QNX4_SUPER_MAGIC:
case ROMFS_SUPER_MAGIC:
/* No symlink support. */
return 0;
default:
return 1;
}
}
/* Used like: return __statfs_chown_restricted (__statfs (name, &buf), &buf);*/
long int
__statfs_chown_restricted (int result, const struct statfs *fsbuf)
{
if (result < 0)
{
if (errno == ENOSYS)
/* Not possible, return the default value. */
return 1;
/* Some error occured. */
return -1;
}
#if __ASSUME_XFS_RESTRICTED_CHOWN
return 1;
#else
int fd;
int save_errno;
long int retval = 1;
switch (fsbuf->f_type)
{
case XFS_SUPER_MAGIC:
save_errno = errno;
/* Read the value from /proc/sys/fs/xfs/restrict_chown. If we cannot
read it default to assume the restriction is in place. */
fd = open_not_cancel_2 ("/proc/sys/fs/xfs/restrict_chown", O_RDONLY);
if (fd != -1)
{
char buf[2];
if (TEMP_FAILURE_RETRY (read_not_cancel (fd, buf, 2)) == 2
&& buf[0] >= '0' && buf[0] <= '1')
retval = buf[0] - '0';
close_not_cancel_no_status (fd);
}
__set_errno (save_errno);
break;
default:
break;
}
return retval;
#endif
}