1 files changed, 270 insertions, 0 deletions
diff --git a/lib/openat.c b/lib/openat.c
new file mode 100644
index 0000000..cd49654
--- /dev/null
+++ b/lib/openat.c
@@ -0,0 +1,270 @@
+/* provide a replacement openat function
+   Copyright (C) 2004, 2005, 2006 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   This program 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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software Foundation,
+   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
+
+/* written by Jim Meyering */
+
+#include <config.h>
+
+#include "openat.h"
+
+#include <stdarg.h>
+#include <stddef.h>
+
+#include "dirname.h" /* solely for definition of IS_ABSOLUTE_FILE_NAME */
+#include "fcntl--.h"
+#include "lchown.h"
+#include "lstat.h"
+#include "openat-priv.h"
+#include "save-cwd.h"
+
+/* Replacement for Solaris' openat function.
+   <http://www.google.com/search?q=openat+site:docs.sun.com>
+   First, try to simulate it via open ("/proc/self/fd/FD/FILE").
+   Failing that, simulate it by doing save_cwd/fchdir/open/restore_cwd.
+   If either the save_cwd or the restore_cwd fails (relatively unlikely),
+   then give a diagnostic and exit nonzero.
+   Otherwise, upon failure, set errno and return -1, as openat does.
+   Upon successful completion, return a file descriptor.  */
+int
+openat (int fd, char const *file, int flags, ...)
+{
+  mode_t mode = 0;
+
+  if (flags & O_CREAT)
+    {
+      va_list arg;
+      va_start (arg, flags);
+
+      /* If mode_t is narrower than int, use the promoted type (int),
+         not mode_t.  Use sizeof to guess whether mode_t is narrower;
+         we don't know of any practical counterexamples.  */
+      mode = (sizeof (mode_t) < sizeof (int)
+	      ? va_arg (arg, int)
+	      : va_arg (arg, mode_t));
+
+      va_end (arg);
+    }
+
+  return openat_permissive (fd, file, flags, mode, NULL);
+}
+
+/* Like openat (FD, FILE, FLAGS, MODE), but if CWD_ERRNO is
+   nonnull, set *CWD_ERRNO to an errno value if unable to save
+   or restore the initial working directory.  This is needed only
+   the first time remove.c's remove_dir opens a command-line
+   directory argument.
+
+   If a previous attempt to restore the current working directory
+   failed, then we must not even try to access a `.'-relative name.
+   It is the caller's responsibility not to call this function
+   in that case.  */
+
+int
+openat_permissive (int fd, char const *file, int flags, mode_t mode,
+		   int *cwd_errno)
+{
+  struct saved_cwd saved_cwd;
+  int saved_errno;
+  int err;
+  bool save_ok;
+
+  if (fd == AT_FDCWD || IS_ABSOLUTE_FILE_NAME (file))
+    return open (file, flags, mode);
+
+  {
+    char buf[OPENAT_BUFFER_SIZE];
+    char *proc_file = openat_proc_name (buf, fd, file);
+    if (proc_file)
+      {
+	int open_result = open (proc_file, flags, mode);
+	int open_errno = errno;
+	if (proc_file != buf)
+	  free (proc_file);
+	/* If the syscall succeeds, or if it fails with an unexpected
+	   errno value, then return right away.  Otherwise, fall through
+	   and resort to using save_cwd/restore_cwd.  */
+	if (0 <= open_result || ! EXPECTED_ERRNO (open_errno))
+	  {
+	    errno = open_errno;
+	    return open_result;
+	  }
+      }
+  }
+
+  save_ok = (save_cwd (&saved_cwd) == 0);
+  if (! save_ok)
+    {
+      if (! cwd_errno)
+	openat_save_fail (errno);
+      *cwd_errno = errno;
+    }
+
+  err = fchdir (fd);
+  saved_errno = errno;
+
+  if (! err)
+    {
+      err = open (file, flags, mode);
+      saved_errno = errno;
+      if (save_ok && restore_cwd (&saved_cwd) != 0)
+	{
+	  if (! cwd_errno)
+	    openat_restore_fail (errno);
+	  *cwd_errno = errno;
+	}
+    }
+
+  free_cwd (&saved_cwd);
+  errno = saved_errno;
+  return err;
+}
+
+/* Return true if our openat implementation must resort to
+   using save_cwd and restore_cwd.  */
+bool
+openat_needs_fchdir (void)
+{
+  bool needs_fchdir = true;
+  int fd = open ("/", O_RDONLY);
+
+  if (0 <= fd)
+    {
+      char buf[OPENAT_BUFFER_SIZE];
+      char *proc_file = openat_proc_name (buf, fd, ".");
+      if (proc_file)
+	{
+	  needs_fchdir = false;
+	  if (proc_file != buf)
+	    free (proc_file);
+	}
+      close (fd);
+    }
+
+  return needs_fchdir;
+}
+
+#if !HAVE_FDOPENDIR
+
+/* Replacement for Solaris' function by the same name.
+   <http://www.google.com/search?q=fdopendir+site:docs.sun.com>
+   First, try to simulate it via opendir ("/proc/self/fd/FD").  Failing
+   that, simulate it by doing save_cwd/fchdir/opendir(".")/restore_cwd.
+   If either the save_cwd or the restore_cwd fails (relatively unlikely),
+   then give a diagnostic and exit nonzero.
+   Otherwise, this function works just like Solaris' fdopendir.
+
+   W A R N I N G:
+   Unlike the other fd-related functions here, this one
+   effectively consumes its FD parameter.  The caller should not
+   close or otherwise manipulate FD if this function returns successfully.  */
+DIR *
+fdopendir (int fd)
+{
+  struct saved_cwd saved_cwd;
+  int saved_errno;
+  DIR *dir;
+
+  char buf[OPENAT_BUFFER_SIZE];
+  char *proc_file = openat_proc_name (buf, fd, ".");
+  if (proc_file)
+    {
+      dir = opendir (proc_file);
+      saved_errno = errno;
+    }
+  else
+    {
+      dir = NULL;
+      saved_errno = EOPNOTSUPP;
+    }
+
+  /* If the syscall fails with an expected errno value, resort to
+     save_cwd/restore_cwd.  */
+  if (! dir && EXPECTED_ERRNO (saved_errno))
+    {
+      if (save_cwd (&saved_cwd) != 0)
+	openat_save_fail (errno);
+
+      if (fchdir (fd) != 0)
+	{
+	  dir = NULL;
+	  saved_errno = errno;
+	}
+      else
+	{
+	  dir = opendir (".");
+	  saved_errno = errno;
+
+	  if (restore_cwd (&saved_cwd) != 0)
+	    openat_restore_fail (errno);
+	}
+
+      free_cwd (&saved_cwd);
+    }
+
+  if (dir)
+    close (fd);
+  if (proc_file != buf)
+    free (proc_file);
+  errno = saved_errno;
+  return dir;
+}
+
+#endif
+
+/* Replacement for Solaris' function by the same name.
+   <http://www.google.com/search?q=fstatat+site:docs.sun.com>
+   First, try to simulate it via l?stat ("/proc/self/fd/FD/FILE").
+   Failing that, simulate it via save_cwd/fchdir/(stat|lstat)/restore_cwd.
+   If either the save_cwd or the restore_cwd fails (relatively unlikely),
+   then give a diagnostic and exit nonzero.
+   Otherwise, this function works just like Solaris' fstatat.  */
+
+#define AT_FUNC_NAME fstatat
+#define AT_FUNC_F1 lstat
+#define AT_FUNC_F2 stat
+#define AT_FUNC_USE_F1_COND flag == AT_SYMLINK_NOFOLLOW
+#define AT_FUNC_POST_FILE_PARAM_DECLS , struct stat *st, int flag
+#define AT_FUNC_POST_FILE_ARGS        , st
+#include "at-func.c"
+#undef AT_FUNC_NAME
+#undef AT_FUNC_F1
+#undef AT_FUNC_F2
+#undef AT_FUNC_USE_F1_COND
+#undef AT_FUNC_POST_FILE_PARAM_DECLS
+#undef AT_FUNC_POST_FILE_ARGS
+
+/* Replacement for Solaris' function by the same name.
+   <http://www.google.com/search?q=unlinkat+site:docs.sun.com>
+   First, try to simulate it via (unlink|rmdir) ("/proc/self/fd/FD/FILE").
+   Failing that, simulate it via save_cwd/fchdir/(unlink|rmdir)/restore_cwd.
+   If either the save_cwd or the restore_cwd fails (relatively unlikely),
+   then give a diagnostic and exit nonzero.
+   Otherwise, this function works just like Solaris' unlinkat.  */
+
+#define AT_FUNC_NAME unlinkat
+#define AT_FUNC_F1 rmdir
+#define AT_FUNC_F2 unlink
+#define AT_FUNC_USE_F1_COND flag == AT_REMOVEDIR
+#define AT_FUNC_POST_FILE_PARAM_DECLS , int flag
+#define AT_FUNC_POST_FILE_ARGS        /* empty */
+#include "at-func.c"
+#undef AT_FUNC_NAME
+#undef AT_FUNC_F1
+#undef AT_FUNC_F2
+#undef AT_FUNC_USE_F1_COND
+#undef AT_FUNC_POST_FILE_PARAM_DECLS
+#undef AT_FUNC_POST_FILE_ARGS