* io/fcntl.h [__USE_ATFILE] (AT_EACCESS): New macro.

	* posix/unistd.h [__USE_ATFILE]: Declare faccessat.
	* io/faccessat.c: New file.
	* sysdeps/unix/sysv/linux/faccessat.c: New file.
	* io/Makefile (routines): Add faccessat.
	* io/Versions (libc: GLIBC_2.4): Likewise.
	* io/tst-faccessat.c: New file.
	* io/Makefile (tests): Add it.

	* io/sys/stat.h: Likewise.

1 files changed, 123 insertions, 0 deletions

diff --git a/sysdeps/unix/sysv/linux/faccessat.c b/sysdeps/unix/sysv/linux/faccessat.c
new file mode 100644
index 0000000000..80b3b240f7
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/faccessat.c
@@ -0,0 +1,123 @@
+/* Test for access to file, relative to open directory.  Linux version.
+   Copyright (C) 2006 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, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <alloca.h>
+#include <sysdep.h>
+
+int
+faccessat (fd, file, mode, flag)
+     int fd;
+     const char *file;
+     int mode;
+     int flag;
+{
+  if (flag & ~(AT_SYMLINK_NOFOLLOW | AT_EACCESS))
+    {
+      __set_errno (EINVAL);
+      return -1;
+    }
+
+  char *buf = NULL;
+
+  if (fd != AT_FDCWD && file[0] != '/')
+    {
+      size_t filelen = strlen (file);
+      static const char procfd[] = "/proc/self/fd/%d/%s";
+      /* Buffer for the path name we are going to use.  It consists of
+	 - the string /proc/self/fd/
+	 - the file descriptor number
+	 - the file name provided.
+	 The final NUL is included in the sizeof.   A bit of overhead
+	 due to the format elements compensates for possible negative
+	 numbers.  */
+      size_t buflen = sizeof (procfd) + sizeof (int) * 3 + filelen;
+      buf = alloca (buflen);
+
+      __snprintf (buf, buflen, procfd, fd, file);
+      file = buf;
+    }
+
+  if ((!(flag & AT_EACCESS) || ! __libc_enable_secure)
+#ifndef __NR_laccess		/* Linux so far has no laccess syscall.  */
+      && !(flag & AT_SYMLINK_NOFOLLOW)
+#endif
+      )
+    {
+      /* If we are not set-uid or set-gid, access does the same.  */
+
+      int result;
+      INTERNAL_SYSCALL_DECL (err);
+
+#ifdef __NR_laccess
+      if (flag & AT_SYMLINK_NOFOLLOW)
+	result = INTERNAL_SYSCALL (laccess, err, 2, file, mode);
+      else
+#endif
+	result = INTERNAL_SYSCALL (access, err, 2, file, mode);
+
+      if (__builtin_expect (INTERNAL_SYSCALL_ERROR_P (result, err), 0))
+	{
+	  __atfct_seterrno (INTERNAL_SYSCALL_ERRNO (result, err), fd, buf);
+	  result = -1;
+	}
+
+      return result;
+    }
+
+  struct stat64 stats;
+  if (fstatat64 (fd, file, &stats, flag & AT_SYMLINK_NOFOLLOW))
+    return -1;
+
+  mode &= (X_OK | W_OK | R_OK);	/* Clear any bogus bits. */
+#if R_OK != S_IROTH || W_OK != S_IWOTH || X_OK != S_IXOTH
+# error Oops, portability assumptions incorrect.
+#endif
+
+  if (mode == F_OK)
+    return 0;			/* The file exists. */
+
+  uid_t uid = (flag & AT_EACCESS) ? __geteuid () : __getuid ();
+
+  /* The super-user can read and write any file, and execute any file
+     that anyone can execute. */
+  if (uid == 0 && ((mode & X_OK) == 0
+		   || (stats.st_mode & (S_IXUSR | S_IXGRP | S_IXOTH))))
+    return 0;
+
+  int granted = (uid == stats.st_uid
+		 ? (unsigned int) (stats.st_mode & (mode << 6)) >> 6
+		 : (stats.st_gid == ((flag & AT_EACCESS)
+				     ? __getegid () : __getgid ())
+		    || __group_member (stats.st_gid))
+		 ? (unsigned int) (stats.st_mode & (mode << 3)) >> 3
+		 : (stats.st_mode & mode));
+
+  if (granted == mode)
+    return 0;
+
+  __set_errno (EACCES);
+  return -1;
+}