Add test-in-container infrastructure.

* Makefile (testroot.pristine): New rules to initialize the
test-in-container "testroot".
* Makerules (all-testsuite): Add tests-container.
* Rules (tests-expected): Add tests-container.
(binaries-all-tests): Likewise.
(tests-container): New, run these tests in the testroot container.
* support/Makefile (others): Add *-container, support_paths.c,
xmkdirp, and links-dso-program.
* support/links-dso-program-c.c: New.
* support/links-dso-program.cc: New.
* support/test-container.c: New.
* support/shell-container.c: New.
* support/echo-container.c: New.
* support/true-container.c: New.
* support/xmkdirp.c: New.
* support/xsymlink.c: New.
* support/support_paths.c: New.
* support/support.h: Add support paths prototypes.
* support/xunistd.h: Add xmkdirp () and xsymlink ().

* nss/tst-nss-test3.c: Convert to test-in-container.
* nss/tst-nss-test3.root/: New.

12 files changed, 1667 insertions, 0 deletions

diff --git a/support/Makefile b/support/Makefile
index 9063046c23..b5fcb6ed86 100644
--- a/support/Makefile
+++ b/support/Makefile
@@ -54,6 +54,7 @@ libsupport-routines = \
   support_format_netent \
   support_isolate_in_subprocess \
   support_openpty \
+  support_paths \
   support_quote_blob \
   support_record_failure \
   support_run_diff \
@@ -85,6 +86,7 @@ libsupport-routines = \
   xmalloc \
   xmemstream \
   xmkdir \
+  xmkdirp \
   xmmap \
   xmprotect \
   xmunmap \
@@ -140,6 +142,7 @@ libsupport-routines = \
   xsocket \
   xstrdup \
   xstrndup \
+  xsymlink \
   xsysconf \
   xunlink \
   xwaitpid \
@@ -152,6 +155,45 @@ ifeq ($(build-shared),yes)
 libsupport-inhibit-o += .o
 endif
 
+CFLAGS-support_paths.c = \
+		-DSRCDIR_PATH=\"`cd .. ; pwd`\" \
+		-DOBJDIR_PATH=\"`cd $(objpfx)/..; pwd`\" \
+		-DINSTDIR_PATH=\"$(prefix)\" \
+		-DLIBDIR_PATH=\"$(libdir)\"
+
+ifeq (,$(CXX))
+LINKS_DSO_PROGRAM = links-dso-program-c
+else
+LINKS_DSO_PROGRAM = links-dso-program
+LDLIBS-links-dso-program = -lstdc++ -lgcc_s
+endif
+
+others: \
+	$(objpfx)test-container \
+	$(objpfx)shell-container \
+	$(objpfx)echo-container \
+	$(objpfx)true-container \
+	$(objpfx)$(LINKS_DSO_PROGRAM)
+
+ifeq ($(build-programs),yes)
+endif
+
+LDLIBS-test-container = $(libsupport)
+
+others += test-container
+others-noinstall += test-container
+
+others += shell-container echo-container true-container
+others-noinstall += shell-container echo-container true-container
+
+others += $(LINKS_DSO_PROGRAM)
+others-noinstall += $(LINKS_DSO_PROGRAM)
+
+$(objpfx)test-container : $(libsupport)
+$(objpfx)shell-container : $(libsupport)
+$(objpfx)echo-container : $(libsupport)
+$(objpfx)true-container : $(libsupport)
+
 tests = \
   README-testing \
   tst-support-namespace \
diff --git a/support/echo-container.c b/support/echo-container.c
new file mode 100644
index 0000000000..e4d48df957
--- /dev/null
+++ b/support/echo-container.c
@@ -0,0 +1,34 @@
+/* Minimal /bin/echo for in-container use.
+   Copyright (C) 2018 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 <stdio.h>
+
+int
+main (int argc, const char **argv)
+{
+  int i;
+
+  for (i = 1; i < argc; i++)
+    {
+      if (i > 1)
+	putchar (' ');
+      fputs (argv[i], stdout);
+    }
+  putchar ('\n');
+  return 0;
+}
diff --git a/support/links-dso-program-c.c b/support/links-dso-program-c.c
new file mode 100644
index 0000000000..d28a28a0d0
--- /dev/null
+++ b/support/links-dso-program-c.c
@@ -0,0 +1,9 @@
+#include <stdio.h>
+
+int
+main (int argc, char **argv)
+{
+  /* Complexity to keep gcc from optimizing this away.  */
+  printf ("This is a test %s.\n", argc > 1 ? argv[1] : "null");
+  return 0;
+}
diff --git a/support/links-dso-program.cc b/support/links-dso-program.cc
new file mode 100644
index 0000000000..dba6976c06
--- /dev/null
+++ b/support/links-dso-program.cc
@@ -0,0 +1,11 @@
+#include <iostream>
+
+using namespace std;
+
+int
+main (int argc, char **argv)
+{
+  /* Complexity to keep gcc from optimizing this away.  */
+  cout << (argc > 1 ? argv[1] : "null");
+  return 0;
+}
diff --git a/support/shell-container.c b/support/shell-container.c
new file mode 100644
index 0000000000..d303131daf
--- /dev/null
+++ b/support/shell-container.c
@@ -0,0 +1,395 @@
+/* Minimal /bin/sh for in-container use.
+   Copyright (C) 2018 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/>.  */
+
+#define _FILE_OFFSET_BITS 64
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sched.h>
+#include <sys/syscall.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <dirent.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/fcntl.h>
+#include <sys/file.h>
+#include <sys/wait.h>
+#include <stdarg.h>
+#include <sys/sysmacros.h>
+#include <ctype.h>
+#include <utime.h>
+#include <errno.h>
+#include <error.h>
+
+#include <support/support.h>
+
+/* Design considerations
+
+ General rule: optimize for developer time, not run time.
+
+ Specifically:
+
+ * Don't worry about slow algorithms
+ * Don't worry about free'ing memory
+ * Don't implement anything the testsuite doesn't need.
+ * Line and argument counts are limited, see below.
+
+*/
+
+#define MAX_ARG_COUNT 100
+#define MAX_LINE_LENGTH 1000
+
+/* Debugging is enabled via --debug, which must be the first argument.  */
+static int debug_mode = 0;
+#define dprintf if (debug_mode) fprintf
+
+/* Emulate the "/bin/true" command.  Arguments are ignored.  */
+static int
+true_func (char **argv)
+{
+  return 0;
+}
+
+/* Emulate the "/bin/echo" command.  Options are ignored, arguments
+   are printed to stdout.  */
+static int
+echo_func (char **argv)
+{
+  int i;
+
+  for (i = 0; argv[i]; i++)
+    {
+      if (i > 0)
+	putchar (' ');
+      fputs (argv[i], stdout);
+    }
+  putchar ('\n');
+
+  return 0;
+}
+
+/* Emulate the "/bin/cp" command.  Options are ignored.  Only copies
+   one source file to one destination file.  Directory destinations
+   are not supported.  */
+static int
+copy_func (char **argv)
+{
+  char *sname = argv[0];
+  char *dname = argv[1];
+  int sfd, dfd;
+  struct stat st;
+
+  sfd = open (sname, O_RDONLY);
+  if (sfd < 0)
+    {
+      fprintf (stderr, "cp: unable to open %s for reading: %s\n",
+	       sname, strerror (errno));
+      return 1;
+    }
+
+  if (fstat (sfd, &st) < 0)
+    {
+      fprintf (stderr, "cp: unable to fstat %s: %s\n",
+	       sname, strerror (errno));
+      return 1;
+    }
+
+  dfd = open (dname, O_WRONLY | O_TRUNC | O_CREAT, 0600);
+  if (dfd < 0)
+    {
+      fprintf (stderr, "cp: unable to open %s for writing: %s\n",
+	       dname, strerror (errno));
+      return 1;
+    }
+
+  if (copy_file_range (sfd, 0, dfd, 0, st.st_size, 0) != st.st_size)
+    {
+      fprintf (stderr, "cp: cannot copy file %s to %s: %s\n",
+	       sname, dname, strerror (errno));
+      return 1;
+    }
+
+  close (sfd);
+  close (dfd);
+
+  chmod (dname, st.st_mode & 0777);
+
+  return 0;
+
+}
+
+/* This is a list of all the built-in commands we understand.  */
+static struct {
+  const char *name;
+  int (*func) (char **argv);
+} builtin_funcs[] = {
+  { "true", true_func },
+  { "echo", echo_func },
+  { "cp", copy_func },
+  { NULL, NULL }
+};
+
+/* Run one tokenized command.  argv[0] is the command.  argv is
+   NULL-terminated.  */
+static void
+run_command_array (char **argv)
+{
+  int i, j;
+  pid_t pid;
+  int status;
+  int (*builtin_func) (char **args);
+
+  if (argv[0] == NULL)
+    return;
+
+  builtin_func = NULL;
+
+  int new_stdin = 0;
+  int new_stdout = 1;
+  int new_stderr = 2;
+
+  dprintf (stderr, "run_command_array starting\n");
+  for (i = 0; argv[i]; i++)
+    dprintf (stderr, "   argv [%d] `%s'\n", i, argv[i]);
+
+  for (j = i = 0; argv[i]; i++)
+    {
+      if (strcmp (argv[i], "<") == 0 && argv[i + 1])
+	{
+	  new_stdin = open (argv[i + 1], O_WRONLY|O_CREAT|O_TRUNC, 0777);
+	  ++i;
+	  continue;
+	}
+      if (strcmp (argv[i], ">") == 0 && argv[i + 1])
+	{
+	  new_stdout = open (argv[i + 1], O_WRONLY|O_CREAT|O_TRUNC, 0777);
+	  ++i;
+	  continue;
+	}
+      if (strcmp (argv[i], ">>") == 0 && argv[i + 1])
+	{
+	  new_stdout = open (argv[i + 1], O_WRONLY|O_CREAT|O_APPEND, 0777);
+	  ++i;
+	  continue;
+	}
+      if (strcmp (argv[i], "2>") == 0 && argv[i + 1])
+	{
+	  new_stderr = open (argv[i + 1], O_WRONLY|O_CREAT|O_TRUNC, 0777);
+	  ++i;
+	  continue;
+	}
+      argv[j++] = argv[i];
+    }
+  argv[j] = NULL;
+
+
+  for (i = 0; builtin_funcs[i].name != NULL; i++)
+    if (strcmp (argv[0], builtin_funcs[i].name) == 0)
+       builtin_func = builtin_funcs[i].func;
+
+  dprintf (stderr, "builtin %p argv0 `%s'\n", builtin_func, argv[0]);
+
+  pid = fork ();
+  if (pid < 0)
+    {
+      fprintf (stderr, "sh: fork failed\n");
+      exit (1);
+    }
+
+  if (pid == 0)
+    {
+      if (new_stdin != 0)
+	{
+	  dup2 (new_stdin, 0);
+	  close (new_stdin);
+	}
+      if (new_stdout != 1)
+	{
+	  dup2 (new_stdout, 1);
+	  close (new_stdout);
+	}
+      if (new_stderr != 2)
+	{
+	  dup2 (new_stderr, 2);
+	  close (new_stdout);
+	}
+
+      if (builtin_func != NULL)
+	exit (builtin_func (argv + 1));
+
+      execvp (argv[0], argv);
+
+      fprintf (stderr, "sh: execing %s failed: %s",
+	       argv[0], strerror (errno));
+      exit (1);
+    }
+
+  waitpid (pid, &status, 0);
+
+  dprintf (stderr, "exiting run_command_array\n");
+
+  if (WIFEXITED (status))
+    {
+      int rv = WEXITSTATUS (status);
+      if (rv)
+	exit (rv);
+    }
+  else
+    exit (1);
+}
+
+/* Run one command-as-a-string, by tokenizing it.  Limited to
+   MAX_ARG_COUNT arguments.  Simple substitution is done of $1 to $9
+   (as whole separate tokens) from iargs[].  Quoted strings work if
+   the quotes wrap whole tokens; i.e. "foo bar" but not foo" bar".  */
+static void
+run_command_string (const char *cmdline, const char **iargs)
+{
+  char *args[MAX_ARG_COUNT+1];
+  int ap = 0;
+  const char *start, *end;
+  int nargs;
+
+  for (nargs = 0; iargs[nargs] != NULL; ++nargs)
+    ;
+
+  dprintf (stderr, "run_command_string starting: '%s'\n", cmdline);
+
+  while (ap < MAX_ARG_COUNT)
+    {
+      /* If the argument is quoted, this is the quote character, else NUL.  */
+      int in_quote = 0;
+
+      /* Skip whitespace up to the next token.  */
+      while (*cmdline && isspace (*cmdline))
+	cmdline ++;
+      if (*cmdline == 0)
+	break;
+
+      start = cmdline;
+      /* Check for quoted argument.  */
+      in_quote = (*cmdline == '\'' || *cmdline == '"') ? *cmdline : 0;
+
+      /* Skip to end of token; either by whitespace or matching quote.  */
+      dprintf (stderr, "in_quote %d\n", in_quote);
+      while (*cmdline
+	     && (!isspace (*cmdline) || in_quote))
+	{
+	  if (*cmdline == in_quote
+	      && cmdline != start)
+	    in_quote = 0;
+	  dprintf (stderr, "[%c]%d ", *cmdline, in_quote);
+	  cmdline ++;
+	}
+      dprintf (stderr, "\n");
+
+      /* Allocate space for this token and store it in args[].  */
+      end = cmdline;
+      dprintf (stderr, "start<%s> end<%s>\n", start, end);
+      args[ap] = (char *) xmalloc (end - start + 1);
+      memcpy (args[ap], start, end - start);
+      args[ap][end - start] = 0;
+
+      /* Strip off quotes, if found.  */
+      dprintf (stderr, "args[%d] = <%s>\n", ap, args[ap]);
+      if (args[ap][0] == '\''
+	  && args[ap][strlen (args[ap])-1] == '\'')
+	{
+	  args[ap][strlen (args[ap])-1] = 0;
+	  args[ap] ++;
+	}
+
+      else if (args[ap][0] == '"'
+	  && args[ap][strlen (args[ap])-1] == '"')
+	{
+	  args[ap][strlen (args[ap])-1] = 0;
+	  args[ap] ++;
+	}
+
+      /* Replace positional parameters like $4.  */
+      else if (args[ap][0] == '$'
+	       && isdigit (args[ap][1])
+	       && args[ap][2] == 0)
+	{
+	  int a = args[ap][1] - '1';
+	  if (0 <= a && a < nargs)
+	    args[ap] = strdup (iargs[a]);
+	}
+
+      ap ++;
+
+      if (*cmdline == 0)
+	break;
+    }
+
+  /* Lastly, NULL terminate the array and run it.  */
+  args[ap] = NULL;
+  run_command_array (args);
+}
+
+/* Run a script by reading lines and passing them to the above
+   function.  */
+static void
+run_script (const char *filename, const char **args)
+{
+  char line[MAX_LINE_LENGTH + 1];
+  dprintf (stderr, "run_script starting: '%s'\n", filename);
+  FILE *f = fopen (filename, "r");
+  if (f == NULL)
+    {
+      fprintf (stderr, "sh: %s: %s\n", filename, strerror (errno));
+      exit (1);
+    }
+  while (fgets (line, sizeof (line), f) != NULL)
+    {
+      if (line[0] == '#')
+	{
+	  dprintf (stderr, "comment: %s\n", line);
+	  continue;
+	}
+      run_command_string (line, args);
+    }
+  fclose (f);
+}
+
+int
+main (int argc, const char **argv)
+{
+  int i;
+
+  if (strcmp (argv[1], "--debug") == 0)
+    {
+      debug_mode = 1;
+      --argc;
+      ++argv;
+    }
+
+  dprintf (stderr, "container-sh starting:\n");
+  for (i = 0; i < argc; i++)
+    dprintf (stderr, "  argv[%d] is `%s'\n", i, argv[i]);
+
+  if (strcmp (argv[1], "-c") == 0)
+    run_command_string (argv[2], argv+3);
+  else
+    run_script (argv[1], argv+2);
+
+  dprintf (stderr, "normal exit 0\n");
+  return 0;
+}
diff --git a/support/support.h b/support/support.h
index 34ae6e10cd..c6ff4bafb4 100644
--- a/support/support.h
+++ b/support/support.h
@@ -25,6 +25,8 @@
 
 #include <stddef.h>
 #include <sys/cdefs.h>
+/* For mode_t.  */
+#include <sys/stat.h>
 
 __BEGIN_DECLS
 
@@ -82,6 +84,16 @@ char *xasprintf (const char *format, ...)
 char *xstrdup (const char *);
 char *xstrndup (const char *, size_t);
 
+/* These point to the TOP of the source/build tree, not your (or
+   support's) subdirectory.  */
+extern const char support_srcdir_root[];
+extern const char support_objdir_root[];
+
+/* Corresponds to the --prefix= passed to configure.  */
+extern const char support_install_prefix[];
+/* Corresponds to the install's lib/ or lib64/ directory.  */
+extern const char support_libdir_prefix[];
+
 __END_DECLS
 
 #endif /* SUPPORT_H */
diff --git a/support/support_paths.c b/support/support_paths.c
new file mode 100644
index 0000000000..a1c22315bd
--- /dev/null
+++ b/support/support_paths.c
@@ -0,0 +1,51 @@
+/* Various paths that might be needed.
+   Copyright (C) 2018 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 <support/support.h>
+#include <support/check.h>
+
+/* The idea here is to make various makefile-level paths available to
+   support programs, as canonicalized absolute paths.  */
+
+/* These point to the TOP of the source/build tree, not your (or
+   support's) subdirectory.  */
+#ifdef SRCDIR_PATH
+const char support_srcdir_root[] = SRCDIR_PATH;
+#else
+# error please -DSRCDIR_PATH=something in the Makefile
+#endif
+
+#ifdef OBJDIR_PATH
+const char support_objdir_root[] = OBJDIR_PATH;
+#else
+# error please -DOBJDIR_PATH=something in the Makefile
+#endif
+
+#ifdef INSTDIR_PATH
+/* Corresponds to the --prefix= passed to configure.  */
+const char support_install_prefix[] = INSTDIR_PATH;
+#else
+# error please -DINSTDIR_PATH=something in the Makefile
+#endif
+
+#ifdef LIBDIR_PATH
+/* Corresponds to the install's lib/ or lib64/ directory.  */
+const char support_libdir_prefix[] = LIBDIR_PATH;
+#else
+# error please -DLIBDIR_PATH=something in the Makefile
+#endif
diff --git a/support/test-container.c b/support/test-container.c
new file mode 100644
index 0000000000..ce16e061e7
--- /dev/null
+++ b/support/test-container.c
@@ -0,0 +1,988 @@
+/* Run a test case in an isolated namespace.
+   Copyright (C) 2018 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/>.  */
+
+#define _FILE_OFFSET_BITS 64
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sched.h>
+#include <sys/syscall.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <dirent.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/fcntl.h>
+#include <sys/file.h>
+#include <sys/wait.h>
+#include <stdarg.h>
+#include <sys/sysmacros.h>
+#include <ctype.h>
+#include <utime.h>
+#include <errno.h>
+#include <error.h>
+
+#ifdef __linux__
+#include <sys/mount.h>
+#endif
+
+#include <support/support.h>
+#include <support/xunistd.h>
+#include "check.h"
+#include "test-driver.h"
+
+#ifndef __linux__
+#define mount(s,t,fs,f,d) no_mount()
+int no_mount (void)
+{
+  FAIL_UNSUPPORTED("mount not supported; port needed");
+}
+#endif
+
+int verbose = 0;
+
+/* Running a test in a container is tricky.  There are two main
+   categories of things to do:
+
+   1. "Once" actions, like setting up the container and doing an
+      install into it.
+
+   2. "Per-test" actions, like copying in support files and
+      configuring the container.
+
+
+   "Once" actions:
+
+   * mkdir $buildroot/testroot.pristine/
+   * install into it
+   * rsync to $buildroot/testroot.root/
+
+   "Per-test" actions:
+   * maybe rsync to $buildroot/testroot.root/
+   * copy support files and test binary
+   * chroot/unshare
+   * set up any mounts (like /proc)
+
+   Magic files:
+
+   For test $srcdir/foo/mytest.c we look for $srcdir/foo/mytest.root
+   and, if found...
+
+   * mytest.root/ is rsync'd into container
+   * mytest.root/preclean.req causes fresh rsync (with delete) before
+     test if present
+   * mytest.root/mytset.script has a list of "commands" to run:
+       syntax:
+         # comment
+         mv FILE FILE
+	 cp FILE FILE
+	 rm FILE
+	 FILE must start with $B/, $S/, $I/, $L/, or /
+	  (expands to build dir, source dir, install dir, library dir
+	   (in container), or container's root)
+   * mytest.root/postclean.req causes fresh rsync (with delete) after
+     test if present
+
+   Note that $srcdir/foo/mytest.script may be used instead of a
+   $srcdir/foo/mytest.root/mytest.script in the sysroot template, if
+   there is no other reason for a sysroot.
+
+   Design goals:
+
+   * independent of other packages which may not be installed (like
+     rsync or Docker, or even "cp")
+
+   * Simple, easy to review code (i.e. prefer simple naive code over
+     complex efficient code)
+
+   * The current implementation ist parallel-make-safe, but only in
+     that it uses a lock to prevent parallel access to the testroot.  */
+
+
+/* Utility Functions */
+
+/* Like xunlink, but it's OK if the file already doesn't exist.  */
+void
+maybe_xunlink (const char *path)
+{
+  int rv = unlink (path);
+  if (rv < 0 && errno != ENOENT)
+    FAIL_EXIT1 ("unlink (\"%s\"): %m", path);
+}
+
+/* Like xmkdir, but it's OK if the directory already exists.  */
+void
+maybe_xmkdir (const char *path, mode_t mode)
+{
+  struct stat st;
+
+  if (stat (path, &st) == 0
+      && S_ISDIR (st.st_mode))
+    return;
+  xmkdir (path, mode);
+}
+
+/* Temporarily concatenate multiple strings into one.  Allows up to 10
+   temporary results; use strdup () if you need them to be
+   permanent.  */
+static char *
+concat (const char *str, ...)
+{
+  /* Assume initialized to NULL/zero.  */
+  static char *bufs[10];
+  static size_t buflens[10];
+  static int bufn = 0;
+  int n;
+  size_t len;
+  va_list ap, ap2;
+  char *cp;
+  char *next;
+
+  va_start (ap, str);
+  va_copy (ap2, ap);
+
+  n = bufn;
+  bufn = (bufn + 1) % 10;
+  len = strlen (str);
+
+  while ((next = va_arg (ap, char *)) != NULL)
+    len = len + strlen (next);
+
+  va_end (ap);
+
+  if (bufs[n] == NULL)
+    {
+      bufs[n] = xmalloc (len + 1); /* NUL */
+      buflens[n] = len + 1;
+    }
+  else if (buflens[n] < len + 1)
+    {
+      bufs[n] = xrealloc (bufs[n], len + 1); /* NUL */
+      buflens[n] = len + 1;
+    }
+
+  strcpy (bufs[n], str);
+  cp = strchr (bufs[n], '\0');
+  while ((next = va_arg (ap2, char *)) != NULL)
+    {
+      strcpy (cp, next);
+      cp = strchr (cp, '\0');
+    }
+  *cp = 0;
+  va_end (ap2);
+
+  return bufs[n];
+}
+
+/* Try to mount SRC onto DEST.  */
+static void
+trymount (const char *src, const char *dest)
+{
+  if (mount (src, dest, "", MS_BIND, NULL) < 0)
+    FAIL_EXIT1 ("can't mount %s onto %s\n", src, dest);
+}
+
+/* Special case of above for devices like /dev/zero where we have to
+   mount a device over a device, not a directory over a directory.  */
+static void
+devmount (const char *new_root_path, const char *which)
+{
+  int fd;
+  fd = open (concat (new_root_path, "/dev/", which, NULL),
+	     O_CREAT | O_TRUNC | O_RDWR, 0777);
+  xclose (fd);
+
+  trymount (concat ("/dev/", which, NULL),
+	    concat (new_root_path, "/dev/", which, NULL));
+}
+
+/* Returns true if the string "looks like" an environement variable
+   being set.  */
+static int
+is_env_setting (const char *a)
+{
+  int count_name = 0;
+
+  while (*a)
+    {
+      if (isalnum (*a) || *a == '_')
+	++count_name;
+      else if (*a == '=' && count_name > 0)
+	return 1;
+      else
+	return 0;
+      ++a;
+    }
+  return 0;
+}
+
+/* Break the_line into words and store in the_words.  Max nwords,
+   returns actual count.  */
+static int
+tokenize (char *the_line, char **the_words, int nwords)
+{
+  int rv = 0;
+
+  while (nwords > 0)
+    {
+      /* Skip leading whitespace, if any.  */
+      while (*the_line && isspace (*the_line))
+	++the_line;
+
+      /* End of line?  */
+      if (*the_line == 0)
+	return rv;
+
+      /* THE_LINE points to a non-whitespace character, so we have a
+	 word.  */
+      *the_words = the_line;
+      ++the_words;
+      nwords--;
+      ++rv;
+
+      /* Skip leading whitespace, if any.  */
+      while (*the_line && ! isspace (*the_line))
+	++the_line;
+
+      /* We now point at the trailing NUL *or* some whitespace.  */
+      if (*the_line == 0)
+	return rv;
+
+      /* It was whitespace, skip and keep tokenizing.  */
+      *the_line++ = 0;
+    }
+
+  /* We get here if we filled the words buffer.  */
+  return rv;
+}
+
+
+/* Mini-RSYNC implementation.  Optimize later.      */
+
+/* A few routines for an "rsync buffer" which stores the paths we're
+   working on.  We continuously grow and shrink the paths in each
+   buffer so there's lot of re-use.  */
+
+/* We rely on "initialized to zero" to set these up.  */
+typedef struct
+{
+  char *buf;
+  size_t len;
+  size_t size;
+} path_buf;
+
+static path_buf spath, dpath;
+
+static void
+r_setup (char *path, path_buf * pb)
+{
+  size_t len = strlen (path);
+  if (pb->buf == NULL || pb->size < len + 1)
+    {
+      /* Round up.  This is an arbitrary number, just to keep from
+	 reallocing too often.  */
+      size_t sz = ALIGN_UP (len + 1, 512);
+      if (pb->buf == NULL)
+	pb->buf = (char *) xmalloc (sz);
+      else
+	pb->buf = (char *) xrealloc (pb->buf, sz);
+      if (pb->buf == NULL)
+	FAIL_EXIT1 ("Out of memory while rsyncing\n");
+
+      pb->size = sz;
+    }
+  strcpy (pb->buf, path);
+  pb->len = len;
+}
+
+static void
+r_append (const char *path, path_buf * pb)
+{
+  size_t len = strlen (path) + pb->len;
+  if (pb->size < len + 1)
+    {
+      /* Round up */
+      size_t sz = ALIGN_UP (len + 1, 512);
+      pb->buf = (char *) xrealloc (pb->buf, sz);
+      if (pb->buf == NULL)
+	FAIL_EXIT1 ("Out of memory while rsyncing\n");
+
+      pb->size = sz;
+    }
+  strcpy (pb->buf + pb->len, path);
+  pb->len = len;
+}
+
+static int
+file_exists (char *path)
+{
+  struct stat st;
+  if (lstat (path, &st) == 0)
+    return 1;
+  return 0;
+}
+
+static void
+recursive_remove (char *path)
+{
+  pid_t child;
+  int status;
+
+  child = fork ();
+
+  switch (child) {
+  case -1:
+    FAIL_EXIT1 ("Unable to fork");
+  case 0:
+    /* Child.  */
+    execlp ("rm", "rm", "-rf", path, NULL);
+  default:
+    /* Parent.  */
+    waitpid (child, &status, 0);
+    /* "rm" would have already printed a suitable error message.  */
+    if (! WIFEXITED (status)
+	|| WEXITSTATUS (status) != 0)
+      exit (1);
+
+    break;
+  }
+}
+
+/* Used for both rsync and the mytest.script "cp" command.  */
+static void
+copy_one_file (const char *sname, const char *dname)
+{
+  int sfd, dfd;
+  struct stat st;
+  struct utimbuf times;
+
+  sfd = open (sname, O_RDONLY);
+  if (sfd < 0)
+    FAIL_EXIT1 ("unable to open %s for reading\n", sname);
+
+  if (fstat (sfd, &st) < 0)
+    FAIL_EXIT1 ("unable to fstat %s\n", sname);
+
+  dfd = open (dname, O_WRONLY | O_TRUNC | O_CREAT, 0600);
+  if (dfd < 0)
+    FAIL_EXIT1 ("unable to open %s for writing\n", dname);
+
+  if (copy_file_range (sfd, 0, dfd, 0, st.st_size, 0) != st.st_size)
+    FAIL_EXIT1 ("cannot copy file %s to %s\n", sname, dname);
+
+  xclose (sfd);
+  xclose (dfd);
+
+  if (chmod (dname, st.st_mode & 0777) < 0)
+    FAIL_EXIT1 ("chmod %s: %s\n", dname, strerror (errno));
+
+  times.actime = st.st_atime;
+  times.modtime = st.st_mtime;
+  if (utime (dname, &times) < 0)
+    FAIL_EXIT1 ("utime %s: %s\n", dname, strerror (errno));
+}
+
+/* We don't check *everything* about the two files to see if a copy is
+   needed, just the minimum to make sure we get the latest copy.  */
+static int
+need_sync (char *ap, char *bp, struct stat *a, struct stat *b)
+{
+  if ((a->st_mode & S_IFMT) != (b->st_mode & S_IFMT))
+    return 1;
+
+  if (S_ISLNK (a->st_mode))
+    {
+      int rv;
+      char *al, *bl;
+
+      if (a->st_size != b->st_size)
+	return 1;
+
+      al = xreadlink (ap);
+      bl = xreadlink (bp);
+      rv = strcmp (al, bl);
+      free (al);
+      free (bl);
+      if (rv == 0)
+	return 0; /* links are same */
+      return 1; /* links differ */
+    }
+
+  if (verbose)
+    {
+      if (a->st_size != b->st_size)
+	printf ("SIZE\n");
+      if ((a->st_mode & 0777) != (b->st_mode & 0777))
+	printf ("MODE\n");
+      if (a->st_mtime != b->st_mtime)
+	printf ("TIME\n");
+    }
+
+  if (a->st_size == b->st_size
+      && ((a->st_mode & 0777) == (b->st_mode & 0777))
+      && a->st_mtime == b->st_mtime)
+    return 0;
+
+  return 1;
+}
+
+static void
+rsync_1 (path_buf * src, path_buf * dest, int and_delete)
+{
+  DIR *dir;
+  struct dirent *de;
+  struct stat s, d;
+
+  r_append ("/", src);
+  r_append ("/", dest);
+
+  if (verbose)
+    printf ("sync %s to %s %s\n", src->buf, dest->buf,
+	    and_delete ? "and delete" : "");
+
+  size_t staillen = src->len;
+
+  size_t dtaillen = dest->len;
+
+  dir = opendir (src->buf);
+
+  while ((de = readdir (dir)) != NULL)
+    {
+      if (strcmp (de->d_name, ".") == 0
+	  || strcmp (de->d_name, "..") == 0)
+	continue;
+
+      src->len = staillen;
+      r_append (de->d_name, src);
+      dest->len = dtaillen;
+      r_append (de->d_name, dest);
+
+      s.st_mode = ~0;
+      d.st_mode = ~0;
+
+      if (lstat (src->buf, &s) != 0)
+	FAIL_EXIT1 ("%s obtained by readdir, but stat failed.\n", src->buf);
+
+      /* It's OK if this one fails, since we know the file might be
+	 missing.  */
+      lstat (dest->buf, &d);
+
+      if (! need_sync (src->buf, dest->buf, &s, &d))
+	{
+	  if (S_ISDIR (s.st_mode))
+	    rsync_1 (src, dest, and_delete);
+	  continue;
+	}
+
+      if (d.st_mode != ~0)
+	switch (d.st_mode & S_IFMT)
+	  {
+	  case S_IFDIR:
+	    if (!S_ISDIR (s.st_mode))
+	      {
+		if (verbose)
+		  printf ("-D %s\n", dest->buf);
+		recursive_remove (dest->buf);
+	      }
+	    break;
+
+	  default:
+	    if (verbose)
+	      printf ("-F %s\n", dest->buf);
+	    maybe_xunlink (dest->buf);
+	    break;
+	  }
+
+      switch (s.st_mode & S_IFMT)
+	{
+	case S_IFREG:
+	  if (verbose)
+	    printf ("+F %s\n", dest->buf);
+	  copy_one_file (src->buf, dest->buf);
+	  break;
+
+	case S_IFDIR:
+	  if (verbose)
+	    printf ("+D %s\n", dest->buf);
+	  maybe_xmkdir (dest->buf, (s.st_mode & 0777) | 0700);
+	  rsync_1 (src, dest, and_delete);
+	  break;
+
+	case S_IFLNK:
+	  {
+	    char *lp;
+	    if (verbose)
+	      printf ("+L %s\n", dest->buf);
+	    lp = xreadlink (src->buf);
+	    xsymlink (lp, dest->buf);
+	    free (lp);
+	    break;
+	  }
+
+	default:
+	  break;
+	}
+    }
+
+  closedir (dir);
+  src->len = staillen;
+  src->buf[staillen] = 0;
+  dest->len = dtaillen;
+  dest->buf[dtaillen] = 0;
+
+  if (!and_delete)
+    return;
+
+  /* The rest of this function removes any files/directories in DEST
+     that do not exist in SRC.  This is triggered as part of a
+     preclean or postsclean step.  */
+
+  dir = opendir (dest->buf);
+
+  while ((de = readdir (dir)) != NULL)
+    {
+      if (strcmp (de->d_name, ".") == 0
+	  || strcmp (de->d_name, "..") == 0)
+	continue;
+
+      src->len = staillen;
+      r_append (de->d_name, src);
+      dest->len = dtaillen;
+      r_append (de->d_name, dest);
+
+      s.st_mode = ~0;
+      d.st_mode = ~0;
+
+      lstat (src->buf, &s);
+
+      if (lstat (dest->buf, &d) != 0)
+	FAIL_EXIT1 ("%s obtained by readdir, but stat failed.\n", dest->buf);
+
+      if (s.st_mode == ~0)
+	{
+	  /* dest exists and src doesn't, clean it.  */
+	  switch (d.st_mode & S_IFMT)
+	    {
+	    case S_IFDIR:
+	      if (!S_ISDIR (s.st_mode))
+		{
+		  if (verbose)
+		    printf ("-D %s\n", dest->buf);
+		  recursive_remove (dest->buf);
+		}
+	      break;
+
+	    default:
+	      if (verbose)
+		printf ("-F %s\n", dest->buf);
+	      maybe_xunlink (dest->buf);
+	      break;
+	    }
+	}
+    }
+
+  closedir (dir);
+}
+
+static void
+rsync (char *src, char *dest, int and_delete)
+{
+  r_setup (src, &spath);
+  r_setup (dest, &dpath);
+
+  rsync_1 (&spath, &dpath, and_delete);
+}
+
+
+int
+main (int argc, char **argv)
+{
+  pid_t child;
+  char *pristine_root_path;
+  char *new_root_path;
+  char *new_cwd_path;
+  char *new_objdir_path;
+  char *new_srcdir_path;
+  char **new_child_proc;
+  char *command_root;
+  char *command_base;
+  char *command_basename;
+  char *so_base;
+  int do_postclean = 0;
+
+  uid_t original_uid;
+  gid_t original_gid;
+  int UMAP;
+  int GMAP;
+  /* Used for "%lld %lld 1" so need not be large.  */
+  char tmp[100];
+  struct stat st;
+  int lock_fd;
+
+  setbuf (stdout, NULL);
+
+  /* The command line we're expecting looks like this:
+     env <set some vars> ld.so <library path> test-binary
+
+     We need to peel off any "env" or "ld.so" portion of the command
+     line, and keep track of which env vars we should preserve and
+     which we drop.  */
+
+  if (argc < 2)
+    {
+      fprintf (stderr, "Usage: containerize <program to run> <args...>\n");
+      exit (1);
+    }
+
+  if (strcmp (argv[1], "-v") == 0)
+    {
+      verbose = 1;
+      ++argv;
+      --argc;
+    }
+
+  if (strcmp (argv[1], "env") == 0)
+    {
+      ++argv;
+      --argc;
+      while (is_env_setting (argv[1]))
+	{
+	  /* If there are variables we do NOT want to propogate, this
+	     is where the test for them goes.  */
+	    {
+	      /* Need to keep these.  Note that putenv stores a
+	         pointer to our argv.  */
+	      putenv (argv[1]);
+	    }
+	  ++argv;
+	  --argc;
+	}
+    }
+
+  if (strncmp (argv[1], concat (support_objdir_root, "/elf/ld-linux-", NULL),
+	       strlen (support_objdir_root) + 14) == 0)
+    {
+      ++argv;
+      --argc;
+      while (argv[1][0] == '-')
+	{
+	  if (strcmp (argv[1], "--library-path") == 0)
+	    {
+	      ++argv;
+	      --argc;
+	    }
+	  ++argv;
+	  --argc;
+	}
+    }
+
+  pristine_root_path = strdup (concat (support_objdir_root,
+				       "/testroot.pristine", NULL));
+  new_root_path = strdup (concat (support_objdir_root,
+				  "/testroot.root", NULL));
+  new_cwd_path = get_current_dir_name ();
+  new_child_proc = argv + 1;
+
+  lock_fd = open (concat (pristine_root_path, "/lock.fd", NULL),
+		 O_CREAT | O_TRUNC | O_RDWR, 0666);
+  if (lock_fd < 0)
+    FAIL_EXIT1 ("Cannot create testroot lock.\n");
+
+  while (flock (lock_fd, LOCK_EX) != 0)
+    {
+      if (errno != EINTR)
+	FAIL_EXIT1 ("Cannot lock testroot.\n");
+    }
+
+  xmkdirp (new_root_path, 0755);
+
+  /* We look for extra setup info in a subdir in the same spot as the
+     test, with the same name but a ".root" extension.  This is that
+     directory.  We try to look in the source tree if the path we're
+     given refers to the build tree, but we rely on the path to be
+     absolute.  This is what the glibc makefiles do.  */
+  command_root = concat (argv[1], ".root", NULL);
+  if (strncmp (command_root, support_objdir_root,
+	       strlen (support_objdir_root)) == 0
+      && command_root[strlen (support_objdir_root)] == '/')
+    command_root = concat (support_srcdir_root,
+			   argv[1] + strlen (support_objdir_root),
+			   ".root", NULL);
+  command_root = strdup (command_root);
+
+  /* This cuts off the ".root" we appended above.  */
+  command_base = strdup (command_root);
+  command_base[strlen (command_base) - 5] = 0;
+
+  /* This is the basename of the test we're running.  */
+  command_basename = strrchr (command_base, '/');
+  if (command_basename == NULL)
+    command_basename = command_base;
+  else
+    ++command_basename;
+
+  /* Shared object base directory.  */
+  so_base = strdup (argv[1]);
+  if (strrchr (so_base, '/') != NULL)
+    strrchr (so_base, '/')[1] = 0;
+
+  if (file_exists (concat (command_root, "/postclean.req", NULL)))
+    do_postclean = 1;
+
+  rsync (pristine_root_path, new_root_path,
+	 file_exists (concat (command_root, "/preclean.req", NULL)));
+
+  if (stat (command_root, &st) >= 0
+      && S_ISDIR (st.st_mode))
+    rsync (command_root, new_root_path, 0);
+
+  new_objdir_path = strdup (concat (new_root_path,
+				    support_objdir_root, NULL));
+  new_srcdir_path = strdup (concat (new_root_path,
+				    support_srcdir_root, NULL));
+
+  /* new_cwd_path starts with '/' so no "/" needed between the two.  */
+  xmkdirp (concat (new_root_path, new_cwd_path, NULL), 0755);
+  xmkdirp (new_srcdir_path, 0755);
+  xmkdirp (new_objdir_path, 0755);
+
+  original_uid = getuid ();
+  original_gid = getgid ();
+
+  /* Handle the cp/mv/rm "script" here.  */
+  {
+    char *the_line = NULL;
+    size_t line_len = 0;
+    char *fname = concat (command_root, "/",
+			  command_basename, ".script", NULL);
+    char *the_words[3];
+    FILE *f = fopen (fname, "r");
+
+    if (verbose && f)
+      fprintf (stderr, "running %s\n", fname);
+
+    if (f == NULL)
+      {
+	/* Try foo.script instead of foo.root/foo.script, as a shortcut.  */
+	fname = concat (command_base, ".script", NULL);
+	f = fopen (fname, "r");
+	if (verbose && f)
+	  fprintf (stderr, "running %s\n", fname);
+      }
+
+    /* Note that we do NOT look for a Makefile-generated foo.script in
+       the build directory.  If that is ever needed, this is the place
+       to add it.  */
+
+    /* This is where we "interpret" the mini-script which is <test>.script.  */
+    if (f != NULL)
+      {
+	while (getline (&the_line, &line_len, f) > 0)
+	  {
+	    int nt = tokenize (the_line, the_words, 3);
+	    int i;
+
+	    for (i = 1; i < nt; ++i)
+	      {
+		if (memcmp (the_words[i], "$B/", 3) == 0)
+		  the_words[i] = concat (support_objdir_root,
+					 the_words[i] + 2, NULL);
+		else if (memcmp (the_words[i], "$S/", 3) == 0)
+		  the_words[i] = concat (support_srcdir_root,
+					 the_words[i] + 2, NULL);
+		else if (memcmp (the_words[i], "$I/", 3) == 0)
+		  the_words[i] = concat (new_root_path,
+					 support_install_prefix,
+					 the_words[i] + 2, NULL);
+		else if (memcmp (the_words[i], "$L/", 3) == 0)
+		  the_words[i] = concat (new_root_path,
+					 support_libdir_prefix,
+					 the_words[i] + 2, NULL);
+		else if (the_words[i][0] == '/')
+		  the_words[i] = concat (new_root_path,
+					 the_words[i], NULL);
+	      }
+
+	    if (nt == 3 && the_words[2][strlen (the_words[2]) - 1] == '/')
+	      {
+		char *r = strrchr (the_words[1], '/');
+		if (r)
+		  the_words[2] = concat (the_words[2], r + 1, NULL);
+		else
+		  the_words[2] = concat (the_words[2], the_words[1], NULL);
+	      }
+
+	    if (nt == 2 && strcmp (the_words[0], "so") == 0)
+	      {
+		the_words[2] = concat (new_root_path, support_libdir_prefix,
+				       "/", the_words[1], NULL);
+		the_words[1] = concat (so_base, the_words[1], NULL);
+		copy_one_file (the_words[1], the_words[2]);
+	      }
+	    else if (nt == 3 && strcmp (the_words[0], "cp") == 0)
+	      {
+		copy_one_file (the_words[1], the_words[2]);
+	      }
+	    else if (nt == 3 && strcmp (the_words[0], "mv") == 0)
+	      {
+		if (rename (the_words[1], the_words[2]) < 0)
+		  FAIL_EXIT1 ("rename %s -> %s: %s", the_words[1],
+			      the_words[2], strerror (errno));
+	      }
+	    else if (nt == 3 && strcmp (the_words[0], "chmod") == 0)
+	      {
+		long int m;
+		m = strtol (the_words[1], NULL, 0);
+		if (chmod (the_words[2], m) < 0)
+		    FAIL_EXIT1 ("chmod %s: %s\n",
+				the_words[2], strerror (errno));
+
+	      }
+	    else if (nt == 2 && strcmp (the_words[0], "rm") == 0)
+	      {
+		maybe_xunlink (the_words[1]);
+	      }
+	    else if (nt > 0 && the_words[0][0] != '#')
+	      {
+		printf ("\033[31minvalid [%s]\033[0m\n", the_words[0]);
+	      }
+	  }
+	fclose (f);
+      }
+  }
+
+#ifdef CLONE_NEWNS
+  /* The unshare here gives us our own spaces and capabilities.  */
+  if (unshare (CLONE_NEWUSER | CLONE_NEWPID | CLONE_NEWNS) < 0)
+    {
+      /* Older kernels may not support all the options.  */
+      if (errno == EINVAL)
+	FAIL_UNSUPPORTED ("unable to unshare user/fs: %s", strerror (errno));
+      else
+	FAIL_EXIT1 ("unable to unshare user/fs: %s", strerror (errno));
+    }
+#else
+  /* Some targets may not support unshare at all.  */
+  FAIL_UNSUPPORTED ("unshare support missing");
+#endif
+
+  /* Some systems, by default, all mounts leak out of the namespace.  */
+  if (mount ("none", "/", NULL, MS_REC | MS_PRIVATE, NULL) != 0)
+    FAIL_EXIT1 ("could not create a private mount namespace\n");
+
+  trymount (support_srcdir_root, new_srcdir_path);
+  trymount (support_objdir_root, new_objdir_path);
+
+  xmkdirp (concat (new_root_path, "/dev", NULL), 0755);
+  devmount (new_root_path, "null");
+  devmount (new_root_path, "zero");
+  devmount (new_root_path, "urandom");
+
+  /* We're done with the "old" root, switch to the new one.  */
+  if (chroot (new_root_path) < 0)
+    FAIL_EXIT1 ("Can't chroot to %s - ", new_root_path);
+
+  if (chdir (new_cwd_path) < 0)
+    FAIL_EXIT1 ("Can't cd to new %s - ", new_cwd_path);
+
+  /* To complete the containerization, we need to fork () at least
+     once.  We can't exec, nor can we somehow link the new child to
+     our parent.  So we run the child and propogate it's exit status
+     up.  */
+  child = fork ();
+  if (child < 0)
+    FAIL_EXIT1 ("Unable to fork");
+  else if (child > 0)
+    {
+      /* Parent.  */
+      int status;
+      waitpid (child, &status, 0);
+
+      /* There's a bit of magic here, since the buildroot is mounted
+	 in our space, the paths are still valid, and since the mounts
+	 aren't recursive, it sees *only* the built root, not anything
+	 we would normally se if we rsync'd to "/" like mounted /dev
+	 files.  */
+      if (do_postclean)
+	  rsync (pristine_root_path, new_root_path, 1);
+
+      if (WIFEXITED (status))
+	exit (WEXITSTATUS (status));
+
+      if (WIFSIGNALED (status))
+	{
+	  printf ("%%SIGNALLED%%\n");
+	  exit (77);
+	}
+
+      printf ("%%EXITERROR%%\n");
+      exit (78);
+    }
+
+  /* The rest is the child process, which is now PID 1 and "in" the
+     new root.  */
+
+  maybe_xmkdir ("/tmp", 0755);
+
+  /* Now that we're pid 1 (effectively "root") we can mount /proc  */
+  maybe_xmkdir ("/proc", 0777);
+  if (mount ("proc", "/proc", "proc", 0, NULL) < 0)
+    FAIL_EXIT1 ("Unable to mount /proc: ");
+
+  /* We map our original UID to the same UID in the container so we
+     can own our own files normally.  */
+  UMAP = open ("/proc/self/uid_map", O_WRONLY);
+  if (UMAP < 0)
+    FAIL_EXIT1 ("can't write to /proc/self/uid_map\n");
+
+  sprintf (tmp, "%lld %lld 1\n",
+	   (long long) original_uid, (long long) original_uid);
+  write (UMAP, tmp, strlen (tmp));
+  xclose (UMAP);
+
+  /* We must disable setgroups () before we can map our groups, else we
+     get EPERM.  */
+  GMAP = open ("/proc/self/setgroups", O_WRONLY);
+  if (GMAP >= 0)
+    {
+      /* We support kernels old enough to not have this.  */
+      write (GMAP, "deny\n", 5);
+      xclose (GMAP);
+    }
+
+  /* We map our original GID to the same GID in the container so we
+     can own our own files normally.  */
+  GMAP = open ("/proc/self/gid_map", O_WRONLY);
+  if (GMAP < 0)
+    FAIL_EXIT1 ("can't write to /proc/self/gid_map\n");
+
+  sprintf (tmp, "%lld %lld 1\n",
+	   (long long) original_gid, (long long) original_gid);
+  write (GMAP, tmp, strlen (tmp));
+  xclose (GMAP);
+
+  /* Now run the child.  */
+  execvp (new_child_proc[0], new_child_proc);
+
+  /* Or don't run the child?  */
+  FAIL_EXIT1 ("Unable to exec %s\n", new_child_proc[0]);
+
+  /* Because gcc won't know error () never returns...  */
+  exit (EXIT_UNSUPPORTED);
+}
diff --git a/support/true-container.c b/support/true-container.c
new file mode 100644
index 0000000000..57dc57e252
--- /dev/null
+++ b/support/true-container.c
@@ -0,0 +1,26 @@
+/* Minimal /bin/true for in-container use.
+   Copyright (C) 2018 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/>.  */
+
+/* Implements the in-container /bin/true, which always returns true
+   (0).  */
+
+int
+main (void)
+{
+  return 0;
+}
diff --git a/support/xmkdirp.c b/support/xmkdirp.c
new file mode 100644
index 0000000000..fada0452ea
--- /dev/null
+++ b/support/xmkdirp.c
@@ -0,0 +1,66 @@
+/* Error-checking replacement for "mkdir -p".
+   Copyright (C) 2018 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 <support/support.h>
+#include <support/check.h>
+#include <support/xunistd.h>
+
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+
+/* Equivalent of "mkdir -p".  Any failures cause FAIL_EXIT1 so no
+   return code is needed.  */
+
+void
+xmkdirp (const char *path, mode_t mode)
+{
+  struct stat s;
+  const char *slash_p;
+  int rv;
+
+  if (path[0] == 0)
+    return;
+
+  if (stat (path, &s) == 0)
+    {
+      if (S_ISDIR (s.st_mode))
+	return;
+      errno = EEXIST;
+      FAIL_EXIT1 ("mkdir_p (\"%s\", 0%o): %m", path, mode);
+    }
+
+  slash_p = strrchr (path, '/');
+  if (slash_p != NULL)
+    {
+      while (slash_p > path && slash_p[-1] == '/')
+	--slash_p;
+      if (slash_p > path)
+	{
+	  char *parent = xstrndup (path, slash_p - path);
+	  xmkdirp (parent, mode);
+	  free (parent);
+	}
+    }
+
+  rv = mkdir (path, mode);
+  if (rv != 0)
+    FAIL_EXIT1 ("mkdir_p (\"%s\", 0%o): %m", path, mode);
+
+  return;
+}
diff --git a/support/xsymlink.c b/support/xsymlink.c
new file mode 100644
index 0000000000..0f3edf640a
--- /dev/null
+++ b/support/xsymlink.c
@@ -0,0 +1,29 @@
+/* Error-checking replacement for "symlink".
+   Copyright (C) 2018 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 <support/support.h>
+#include <support/check.h>
+
+#include <unistd.h>
+
+void
+xsymlink (const char *target, const char *linkpath)
+{
+  if (symlink (target, linkpath) < 0)
+    FAIL_EXIT1 ("symlink (\"%s\", \"%s\")", target, linkpath);
+}
diff --git a/support/xunistd.h b/support/xunistd.h
index 5fe5dae818..cdd4e8d92d 100644
--- a/support/xunistd.h
+++ b/support/xunistd.h
@@ -43,6 +43,10 @@ void xunlink (const char *path);
 long xsysconf (int name);
 long long xlseek (int fd, long long offset, int whence);
 void xftruncate (int fd, long long length);
+void xsymlink (const char *target, const char *linkpath);
+
+/* Equivalent of "mkdir -p".  */
+void xmkdirp (const char *, mode_t);
 
 /* Read the link at PATH.  The caller should free the returned string
    with free.  */