1 files changed, 214 insertions, 0 deletions
diff --git a/sysdeps/unix/sysv/linux/shm_open.c b/sysdeps/unix/sysv/linux/shm_open.c
new file mode 100644
index 0000000000..08bdaeadbd
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/shm_open.c
@@ -0,0 +1,214 @@
+/* Copyright (C) 2000 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 Library General Public License as
+   published by the Free Software Foundation; either version 2 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
+   Library General Public License for more details.
+
+   You should have received a copy of the GNU Library General Public
+   License along with the GNU C Library; see the file COPYING.LIB.  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 <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/mman.h>
+#include <sys/statfs.h>
+#include <bits/libc-lock.h>
+
+
+/* XXX Currently the Linux kernel sources do not define a super magic number
+   for the shmfs and the kernel assigns the value 0 to f_type.  */
+#ifndef SHMFS_SUPER_MAGIC
+# define SHMFS_SUPER_MAGIC	0
+#endif
+
+/* Mount point of the shared memory filesystem.  */
+static struct
+{
+  char *dir;
+  size_t dirlen;
+} mountpoint;
+
+/* This is the default directory.  */
+const char defaultdir[] = "/var/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 /var/shm.  This is at least what the
+     documentation tells everybody to do.  */
+  if (__statfs ("/var/shm", &f) == 0 && f.f_type == SHMFS_SUPER_MAGIC)
+    {
+      /* It is in the normal place.  */
+      mountpoint.dir = (char *) defaultdir;
+      mountpoint.dirlen = strlen ("/var/shm/");
+
+      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)
+    if (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 = 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 /var/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;
+
+  /* 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;
+
+  if (name[0] == '\0')
+    {
+      /* The name "/" is not supported.  */
+      __set_errno (EINVAL);
+      return -1;
+    }
+
+  namelen = strlen (name);
+  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.  */
+  return open (fname, oflag, mode);
+}
+
+
+/* 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;
+
+  if (name[0] == '\0')
+    {
+      /* The name "/" is not supported.  */
+      __set_errno (ENOENT);
+      return -1;
+    }
+
+  namelen = strlen (name);
+  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.  */
+  return unlink (fname);
+}
+
+
+void
+freeit (void)
+{
+  if (mountpoint.dir != NULL && mountpoint.dir != defaultdir)
+    free (mountpoint.dir);
+}
+
+
+/* Make sure the table is freed if we want to free everything before
+   exiting.  */
+text_set_element (__libc_subfreeres, freeit);