1 files changed, 144 insertions, 0 deletions
diff --git a/sysdeps/unix/sysv/linux/shm-directory.c b/sysdeps/unix/sysv/linux/shm-directory.c
new file mode 100644
index 0000000000..9340f9c331
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/shm-directory.c
@@ -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);
+}