Prepare for radical source tree reorganization.zack/build-layout-experiment

All top-level files and directories are moved into a temporary storage
directory, REORG.TODO, except for files that will certainly still
exist in their current form at top level when we're done (COPYING,
COPYING.LIB, LICENSES, NEWS, README), all old ChangeLog files (which
are moved to the new directory OldChangeLogs, instead), and the
generated file INSTALL (which is just deleted; in the new order, there
will be no generated files checked into version control).

1 files changed, 97 insertions, 0 deletions

diff --git a/REORG.TODO/csu/check_fds.c b/REORG.TODO/csu/check_fds.c
new file mode 100644
index 0000000000..062c879373
--- /dev/null
+++ b/REORG.TODO/csu/check_fds.c
@@ -0,0 +1,97 @@
+/* Copyright (C) 2000-2017 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 <errno.h>
+#include <fcntl.h>
+#include <paths.h>
+#include <unistd.h>
+#include <sys/stat.h>
+#include <sys/sysmacros.h>
+
+/* Try to get a machine dependent instruction which will make the
+   program crash.  This is used in case everything else fails.  */
+#include <abort-instr.h>
+#ifndef ABORT_INSTRUCTION
+/* No such instruction is available.  */
+# define ABORT_INSTRUCTION
+#endif
+
+#include <device-nrs.h>
+#include <not-cancel.h>
+
+
+/* Should other OSes (e.g., Hurd) have different versions which can
+   be written in a better way?  */
+static void
+check_one_fd (int fd, int mode)
+{
+  /* Note that fcntl() with this parameter is not a cancellation point.  */
+  if (__builtin_expect (__libc_fcntl (fd, F_GETFD), 0) == -1
+      && errno == EBADF)
+    {
+      const char *name;
+      dev_t dev;
+
+      /* For writable descriptors we use /dev/full.  */
+      if ((mode & O_ACCMODE) == O_WRONLY)
+	{
+	  name = _PATH_DEV "full";
+	  dev = makedev (DEV_FULL_MAJOR, DEV_FULL_MINOR);
+	}
+      else
+	{
+	  name = _PATH_DEVNULL;
+	  dev = makedev (DEV_NULL_MAJOR, DEV_NULL_MINOR);
+	}
+
+      /* Something is wrong with this descriptor, it's probably not
+	 opened.  Open /dev/null so that the SUID program we are
+	 about to start does not accidentally use this descriptor.  */
+      int nullfd = open_not_cancel (name, mode, 0);
+
+      /* We are very paranoid here.  With all means we try to ensure
+	 that we are actually opening the /dev/null device and nothing
+	 else.
+
+	 Note that the following code assumes that STDIN_FILENO,
+	 STDOUT_FILENO, STDERR_FILENO are the three lowest file
+	 decsriptor numbers, in this order.  */
+      struct stat64 st;
+      if (__builtin_expect (nullfd != fd, 0)
+	  || __builtin_expect (__fxstat64 (_STAT_VER, fd, &st), 0) != 0
+	  || __builtin_expect (S_ISCHR (st.st_mode), 1) == 0
+	  || st.st_rdev != dev)
+	/* We cannot even give an error message here since it would
+	   run into the same problems.  */
+	while (1)
+	  /* Try for ever and ever.  */
+	  ABORT_INSTRUCTION;
+    }
+}
+
+
+void
+__libc_check_standard_fds (void)
+{
+  /* Check all three standard file descriptors.  The O_NOFOLLOW flag
+     is really paranoid but some people actually are.  If /dev/null
+     should happen to be a symlink to somewhere else and not the
+     device commonly known as "/dev/null" we bail out.  */
+  check_one_fd (STDIN_FILENO, O_WRONLY | O_NOFOLLOW);
+  check_one_fd (STDOUT_FILENO, O_RDONLY | O_NOFOLLOW);
+  check_one_fd (STDERR_FILENO, O_RDONLY | O_NOFOLLOW);
+}