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-rw-r--r--nptl/sem_open.c258
1 files changed, 258 insertions, 0 deletions
diff --git a/nptl/sem_open.c b/nptl/sem_open.c
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+++ b/nptl/sem_open.c
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+/* Copyright (C) 2002 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+ Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
+
+ 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, write to the Free
+ Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+ 02111-1307 USA. */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <mntent.h>
+#include <paths.h>
+#include <pthread.h>
+#include <semaphore.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#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)
+ {
+ /* 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 (__builtin_expect (fp == NULL, 0))
+ {
+ fp = __setmntent (_PATH_MNTTAB, "r");
+ if (__builtin_expect (fp == NULL, 0))
+ /* 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)
+ 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);
+}
+
+
+sem_t *
+sem_open (const char *name, int oflag, ...)
+{
+ char *finalname;
+ size_t namelen;
+ sem_t *result;
+ int fd;
+
+ /* 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;
+ }
+ namelen = strlen (name);
+
+ /* Create the name of the final file. */
+ finalname = (char *) alloca (mountpoint.dirlen + namelen + 1);
+ __mempcpy (__mempcpy (finalname, mountpoint.dir, mountpoint.dirlen),
+ name, namelen + 1);
+
+ /* If the semaphore object has to exist simply open it. */
+ if ((oflag & O_CREAT) == 0)
+ {
+ fd = open (finalname, oflag | O_NOFOLLOW);
+
+ if (fd == -1)
+ /* Return. errno is already set. */
+ return SEM_FAILED;
+
+ /* Map the sem_t structure from the file. */
+ result = (sem_t *) mmap (NULL, sizeof (sem_t), PROT_READ | PROT_WRITE,
+ MAP_SHARED, fd, 0);
+ }
+ else
+ {
+ /* We have to open a temporary file first since it must have the
+ correct form before we can start using it. */
+ char *tmpfname;
+ mode_t mode;
+ unsigned int value;
+ va_list ap;
+
+ va_start (ap, oflag);
+
+ mode = va_arg (ap, mode_t);
+ value = va_arg (ap, unsigned int);
+
+ va_end (ap);
+
+ if (value > SEM_VALUE_MAX)
+ {
+ __set_errno (EINVAL);
+ return SEM_FAILED;
+ }
+
+ tmpfname = (char *) alloca (mountpoint.dirlen + 6 + 1);
+ strcpy (__mempcpy (tmpfname, mountpoint.dir, mountpoint.dirlen),
+ "XXXXXX");
+
+ fd = mkstemp (tmpfname);
+ if (fd == -1)
+ return SEM_FAILED;
+
+ /* Create the initial file content. */
+ sem_t initsem;
+
+ struct sem *iinitsem = (struct sem *) &initsem;
+ iinitsem->count = value;
+
+ /* Initialize the remaining bytes as well. */
+ memset ((char *) &initsem + sizeof (struct sem), '\0',
+ sizeof (sem_t) - sizeof (struct sem));
+
+ if (TEMP_FAILURE_RETRY (write (fd, &initsem, sizeof (sem_t)))
+ != sizeof (sem_t)
+ /* Adjust the permission. */
+ || fchmod (fd, mode) != 0)
+ {
+ unlink_return:
+ unlink (tmpfname);
+ return SEM_FAILED;
+ }
+
+ /* Map the sem_t structure from the file. */
+ result = (sem_t *) mmap (NULL, sizeof (sem_t), PROT_READ | PROT_WRITE,
+ MAP_SHARED, fd, 0);
+ if (result == MAP_FAILED)
+ goto unlink_return;
+
+ /* Create or overwrite the file. Depending on what is wanted we
+ use rename or link. */
+ if ((oflag & O_EXCL) == 0)
+ {
+ /* An existing file gets overwritten. */
+ if (rename (tmpfname, finalname) != 0)
+ {
+ unmap_unlink_return:
+ munmap (result, sizeof (sem_t));
+ goto unlink_return;
+ }
+ }
+ else
+ {
+ /* Don't overwrite an existing file. */
+ if (link (tmpfname, finalname) != 0)
+ goto unmap_unlink_return;
+
+ /* This went well. Now remove the temporary name. This
+ should never fail. If it fails we leak a file name.
+ Better fix the kernel. */
+ (void) unlink (tmpfname);
+ }
+ }
+
+ /* We don't need the file descriptor anymore. */
+ close (fd);
+
+ return result;
+}