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NPTL: Refactor named semaphore code to use shm-directory.h

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This commit is contained in:
Roland McGrath
2014-12-12 13:17:21 -08:00
parent c76d1ff514
commit e4f639e4a1
14 changed files with 113 additions and 183 deletions
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143
nptl/sem_open.c
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@ -18,8 +18,6 @@
#include <errno.h>
#include <fcntl.h>
#include <mntent.h>
#include <paths.h>
#include <pthread.h>
#include <search.h>
#include <semaphore.h>
@ -30,98 +28,8 @@
#include <unistd.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/statfs.h>
#include <linux_fsinfo.h>
#include "semaphoreP.h"
/* Information about the mount point. */
struct mountpoint_info mountpoint attribute_hidden;
/* This is the default mount point. */
static const char defaultmount[] = "/dev/shm";
/* This is the default directory. */
static const char defaultdir[] = "/dev/shm/sem.";
/* Protect the `mountpoint' variable above. */
pthread_once_t __namedsem_once attribute_hidden = PTHREAD_ONCE_INIT;
/* Determine where the shmfs is mounted (if at all). */
void
attribute_hidden
__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 (defaultmount, &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 + 4 + 2);
if (mountpoint.dir != NULL)
{
char *cp = __mempcpy (mountpoint.dir, mp->mnt_dir, namelen);
if (cp[-1] != '/')
*cp++ = '/';
cp = stpcpy (cp, "sem.");
mountpoint.dirlen = cp - mountpoint.dir;
}
break;
}
/* Close the stream. */
__endmntent (fp);
}
#include <shm-directory.h>
/* Comparison function for search of existing mapping. */
@ -217,8 +125,9 @@ check_add_mapping (const char *name, size_t namelen, int fd, sem_t *existing)
if (result != existing && existing != SEM_FAILED && existing != MAP_FAILED)
{
/* Do not disturb errno. */
INTERNAL_SYSCALL_DECL (err);
INTERNAL_SYSCALL (munmap, err, 2, existing, sizeof (sem_t));
int save = errno;
munmap (existing, sizeof (sem_t));
errno = save;
}
return result;
@ -228,42 +137,17 @@ check_add_mapping (const char *name, size_t namelen, int fd, sem_t *existing)
sem_t *
sem_open (const char *name, int oflag, ...)
{
char *finalname;
sem_t *result = SEM_FAILED;
int fd;
sem_t *result;
/* Determine where the shmfs is mounted. */
__pthread_once (&__namedsem_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 SEM_FAILED;
}
/* Construct the filename. */
while (name[0] == '/')
++name;
if (name[0] == '\0')
{
/* The name "/" is not supported. */
__set_errno (EINVAL);
return SEM_FAILED;
}
size_t namelen = strlen (name) + 1;
/* Create the name of the final file. */
finalname = (char *) alloca (mountpoint.dirlen + namelen);
__mempcpy (__mempcpy (finalname, mountpoint.dir, mountpoint.dirlen),
name, namelen);
/* Create the name of the final file in local variable SHM_NAME. */
SHM_GET_NAME (EINVAL, SEM_FAILED, SEM_SHM_PREFIX);
/* If the semaphore object has to exist simply open it. */
if ((oflag & O_CREAT) == 0 || (oflag & O_EXCL) == 0)
{
try_again:
fd = __libc_open (finalname,
fd = __libc_open (shm_name,
(oflag & ~(O_CREAT|O_ACCMODE)) | O_NOFOLLOW | O_RDWR);
if (fd == -1)
@ -317,8 +201,8 @@ sem_open (const char *name, int oflag, ...)
memset ((char *) &sem.initsem + sizeof (struct new_sem), '\0',
sizeof (sem_t) - sizeof (struct new_sem));
tmpfname = (char *) alloca (mountpoint.dirlen + 6 + 1);
char *xxxxxx = __mempcpy (tmpfname, mountpoint.dir, mountpoint.dirlen);
tmpfname = __alloca (shm_dirlen + sizeof SEM_SHM_PREFIX + 6);
char *xxxxxx = __mempcpy (tmpfname, shm_dir, shm_dirlen);
int retries = 0;
#define NRETRIES 50
@ -361,7 +245,7 @@ sem_open (const char *name, int oflag, ...)
fd, 0)) != MAP_FAILED)
{
/* Create the file. Don't overwrite an existing file. */
if (link (tmpfname, finalname) != 0)
if (link (tmpfname, shm_name) != 0)
{
/* Undo the mapping. */
(void) munmap (result, sizeof (sem_t));
@ -402,8 +286,9 @@ sem_open (const char *name, int oflag, ...)
if (fd != -1)
{
/* Do not disturb errno. */
INTERNAL_SYSCALL_DECL (err);
INTERNAL_SYSCALL (close, err, 1, fd);
int save = errno;
__libc_close (fd);
errno = save;
}
return result;