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Refactor shm_{open,unlink} code to separate Linux-specific directory choice from POSIX-generic code.

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This commit is contained in:
Roland McGrath 2014-12-11 14:15:51 -08:00
parent f82c43af8a
commit 78e21c5df6
9 changed files with 287 additions and 279 deletions
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14
ChangeLog
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@ -1,3 +1,17 @@
2014-12-11 Roland McGrath <roland@hack.frob.com>
* sysdeps/posix/shm-directory.c: New file.
* sysdeps/posix/shm-directory.h: New file.
* sysdeps/posix/Makefile [($(subdir) = rt] (librt-routines): Add it.
* sysdeps/posix/shm_open.c: Use SHM_GET_NAME.
Use O_NOFOLLOW and O_CLOEXEC if available. Transmute EISDIR to EINVAL.
* sysdeps/posix/shm_unlink.c: Use SHM_GET_NAME.
Transmute EPERM to EACCES.
* sysdeps/unix/sysv/linux/shm-directory.c: New file, most code taken
from ...
* sysdeps/unix/sysv/linux/shm_open.c: ... here. File removed.
* sysdeps/unix/sysv/linux/shm_unlink.c: File removed.
2014-12-11 Kaz Kojima <kkojima@rr.iij4u.or.jp>
* sysdeps/sh/jmpbuf_unwind.h (_jmpbuf_sp): Declare SP as void

4
sysdeps/posix/Makefile
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@ -3,3 +3,7 @@ L_tmpnam = 20
TMP_MAX = 238328
L_ctermid = 9
L_cuserid = 9
ifeq ($(subdir),rt)
librt-routines += shm-directory
endif

35
sysdeps/posix/shm-directory.c Normal file
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@ -0,0 +1,35 @@
/* Determine directory for shm/sem files. Generic POSIX version.
Copyright (C) 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 "shm-directory.h"
#include <unistd.h>
#if _POSIX_MAPPED_FILES
# include <paths.h>
# define SHMDIR (_PATH_DEV "shm/")
const char *
__shm_directory (size_t *len)
{
*len = sizeof SHMDIR - 1;
return SHMDIR;
}
#endif

63
sysdeps/posix/shm-directory.h Normal file
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@ -0,0 +1,63 @@
/* Header for directory for shm/sem files.
Copyright (C) 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/>. */
#ifndef _SHM_DIRECTORY_H
#include <errno.h>
#include <limits.h>
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>
extern const char *__shm_directory (size_t *len);
/* This defines local variables SHM_DIR and SHM_DIRLEN, giving the
directory prefix (with trailing slash) and length (not including '\0'
terminator) of the directory used for shm files. If that cannot be
determined, it sets errno to ENOSYS and returns RETVAL_FOR_INVALID.
This uses the local variable NAME as an lvalue, and increments it past
any leading slashes. It then defines the local variable NAMELEN, giving
strlen (NAME) + 1. If NAME is invalid, it sets errno to
ERRNO_FOR_INVALID and returns RETVAL_FOR_INVALID. Finally, it defines
the local variable SHM_NAME, giving the absolute file name of the shm
file corresponding to NAME. */
#define SHM_GET_NAME(errno_for_invalid, retval_for_invalid) \
size_t shm_dirlen; \
const char *shm_dir = __shm_directory (&shm_dirlen); \
/* If we don't know what directory to use, there is nothing we can do. */ \
if (__glibc_unlikely (shm_dir == NULL)) \
{ \
__set_errno (ENOSYS); \
return retval_for_invalid; \
} \
/* Construct the filename. */ \
while (name[0] == '/') \
++name; \
size_t namelen = strlen (name) + 1; \
/* Validate the filename. */ \
if (namelen == 1 || namelen >= NAME_MAX || strchr (name, '/') != NULL) \
{ \
__set_errno (errno_for_invalid); \
return retval_for_invalid; \
} \
char *shm_name = __alloca (shm_dirlen + namelen); \
__mempcpy (__mempcpy (shm_name, shm_dir, shm_dirlen), name, namelen)
#endif /* shm-directory.h */

50
sysdeps/posix/shm_open.c
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@ -19,50 +19,41 @@
#include <unistd.h>
#if ! _POSIX_MAPPED_FILES
#include <rt/shm_open.c>
# include <rt/shm_open.c>
#else
#include <errno.h>
#include <sys/mman.h>
#include <fcntl.h>
#include <string.h>
#include <stdlib.h>
#include <paths.h>
# include <fcntl.h>
# include <shm-directory.h>
#define SHMDIR (_PATH_DEV "shm/")
/* Open shared memory object. */
int
shm_open (const char *name, int oflag, mode_t mode)
{
size_t namelen;
char *fname;
int fd;
SHM_GET_NAME (EINVAL, -1);
/* Construct the filename. */
while (name[0] == '/')
++name;
# ifdef O_NOFOLLOW
oflag |= O_NOFOLLOW;
# endif
# ifdef O_CLOEXEC
oflag |= O_CLOEXEC;
# endif
int fd = open (shm_name, oflag, mode);
if (fd == -1 && __glibc_unlikely (errno == EISDIR))
/* It might be better to fold this error with EINVAL since
directory names are just another example for unsuitable shared
object names and the standard does not mention EISDIR. */
__set_errno (EINVAL);
if (name[0] == '\0')
{
/* The name "/" is not supported. */
__set_errno (EINVAL);
return -1;
}
namelen = strlen (name);
fname = (char *) __alloca (sizeof SHMDIR - 1 + namelen + 1);
__mempcpy (__mempcpy (fname, SHMDIR, sizeof SHMDIR - 1),
name, namelen + 1);
fd = open (name, oflag, mode);
# ifndef O_CLOEXEC
if (fd != -1)
{
/* We got a descriptor. Now set the FD_CLOEXEC bit. */
int flags = fcntl (fd, F_GETFD, 0);
if (__builtin_expect (flags, 0) != -1)
if (__glibc_likely (flags != -1))
{
flags |= FD_CLOEXEC;
flags = fcntl (fd, F_SETFD, flags);
@ -77,8 +68,9 @@ shm_open (const char *name, int oflag, mode_t mode)
__set_errno (save_errno);
}
}
# endif
return fd;
}
#endif
#endif /* _POSIX_MAPPED_FILES */

29
sysdeps/posix/shm_unlink.c
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@ -24,37 +24,20 @@
#else
#include <errno.h>
#include <sys/mman.h>
#include <string.h>
#include <stdlib.h>
#include <paths.h>
#include "shm-directory.h"
#define SHMDIR (_PATH_DEV "shm/")
/* Remove shared memory object. */
int
shm_unlink (const char *name)
{
size_t namelen;
char *fname;
SHM_GET_NAME (ENOENT, -1);
/* Construct the filename. */
while (name[0] == '/')
++name;
if (name[0] == '\0')
{
/* The name "/" is not supported. */
__set_errno (EINVAL);
return -1;
}
namelen = strlen (name);
fname = (char *) __alloca (sizeof SHMDIR - 1 + namelen + 1);
__mempcpy (__mempcpy (fname, SHMDIR, sizeof SHMDIR - 1),
name, namelen + 1);
return unlink (name);
int result = unlink (shm_name);
if (result < 0 && errno == EPERM)
__set_errno (EACCES);
return result;
}
#endif

144
sysdeps/unix/sysv/linux/shm-directory.c Normal file
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@ -0,0 +1,144 @@
/* Determine directory for shm/sem files. Linux version.
Copyright (C) 2000-2014 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 "shm-directory.h"
#include <errno.h>
#include <mntent.h>
#include <paths.h>
#include <stdio.h>
#include <string.h>
#include <sys/statfs.h>
#include <bits/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;
}
/* Make sure the table is freed if we want to free everything before
exiting. */
libc_freeres_fn (freeit)
{
if (mountpoint.dir != defaultdir)
free (mountpoint.dir);
}

226
sysdeps/unix/sysv/linux/shm_open.c
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@ -1,226 +0,0 @@
/* Copyright (C) 2000-2014 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 <fcntl.h>
#include <mntent.h>
#include <paths.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/statfs.h>
#include <bits/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);
}
/* Open shared memory object. This implementation assumes the shmfs
implementation introduced in the late 2.3.x kernel series to be
available. Normally the filesystem will be mounted at /dev/shm but
we fall back on searching for the actual mount point should opening
such a file fail. */
int
shm_open (const char *name, int oflag, mode_t mode)
{
size_t namelen;
char *fname;
int fd;
/* 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 (mountpoint.dir == NULL)
{
__set_errno (ENOSYS);
return -1;
}
/* Construct the filename. */
while (name[0] == '/')
++name;
namelen = strlen (name);
/* Validate the filename. */
if (name[0] == '\0' || namelen > NAME_MAX || strchr (name, '/') != NULL)
{
__set_errno (EINVAL);
return -1;
}
fname = (char *) alloca (mountpoint.dirlen + namelen + 1);
__mempcpy (__mempcpy (fname, mountpoint.dir, mountpoint.dirlen),
name, namelen + 1);
/* And get the file descriptor.
XXX Maybe we should test each descriptor whether it really is for a
file on the shmfs. If this is what should be done the whole function
should be revamped since we can determine whether shmfs is available
while trying to open the file, all in one turn. */
fd = open (fname, oflag | O_CLOEXEC | O_NOFOLLOW, mode);
if (fd == -1 && __glibc_unlikely (errno == EISDIR))
/* It might be better to fold this error with EINVAL since
directory names are just another example for unsuitable shared
object names and the standard does not mention EISDIR. */
__set_errno (EINVAL);
return fd;
}
/* Unlink a shared memory object. */
int
shm_unlink (const char *name)
{
size_t namelen;
char *fname;
/* Determine where the shmfs is mounted. */
__libc_once (once, where_is_shmfs);
if (mountpoint.dir == NULL)
{
/* We cannot find the shmfs. If `name' is really a shared
memory object it must have been created by another process
and we have no idea where that process found the mountpoint. */
__set_errno (ENOENT);
return -1;
}
/* Construct the filename. */
while (name[0] == '/')
++name;
namelen = strlen (name);
/* Validate the filename. */
if (name[0] == '\0' || namelen > NAME_MAX || strchr (name, '/') != NULL)
{
__set_errno (ENOENT);
return -1;
}
fname = (char *) alloca (mountpoint.dirlen + namelen + 1);
__mempcpy (__mempcpy (fname, mountpoint.dir, mountpoint.dirlen),
name, namelen + 1);
/* And remove the file. */
int ret = unlink (fname);
if (ret < 0 && errno == EPERM)
__set_errno (EACCES);
return ret;
}
/* Make sure the table is freed if we want to free everything before
exiting. */
libc_freeres_fn (freeit)
{
if (mountpoint.dir != defaultdir)
free (mountpoint.dir);
}

1
sysdeps/unix/sysv/linux/shm_unlink.c
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@ -1 +0,0 @@
/* This function is for technical reason defined in shm_open.c. */