posix: execvpe cleanup

This patch removes all the dynamic allocation on execvpe code and
instead use direct stack allocation.  This is QoI approach to make
it possible use in scenarios where memory is shared with parent
(vfork or clone with CLONE_VM).

For default process spawn (script file without a shebang), stack
allocation is bounded by NAME_MAX plus PATH_MAX plus 1.  Large
file arguments returns an error (ENAMETOOLONG).  This differs than
current GLIBC pratice in general, but it used to limit stack
allocation for large inputs.  Also, path in PATH environment variable
larger than PATH_MAX are ignored.

The shell direct execution exeception, where execve returns ENOEXEC,
might requires a large stack allocation due large input argument list.

Tested on i686, x86_64, powerpc64le, and aarch64.

	* posix/execvpe.c (__execvpe): Remove dynamic allocation.
	* posix/Makefile (tests): Add tst-execvpe{1,2,3,4,5,6}.
	* posix/tst-execvp1.c (do_test): Use a macro to call execvp.
	* posix/tst-execvp2.c (do_test): Likewise.
	* posix/tst-execvp3.c (do_test): Likewise.
	* posix/tst-execvp4.c (do_test): Likewise.
	* posix/tst-execvpe1.c: New file.
	* posix/tst-execvpe2.c: Likewise.
	* posix/tst-execvpe3.c: Likewise.
	* posix/tst-execvpe4.c: Likewise.
	* posix/tst-execvpe5.c: Likewise.
	* posix/tst-execvpe6.c: Likewise.

1 files changed, 150 insertions, 0 deletions

diff --git a/posix/tst-execvpe6.c b/posix/tst-execvpe6.c
new file mode 100644
index 0000000000..bfb6ee11ac
--- /dev/null
+++ b/posix/tst-execvpe6.c
@@ -0,0 +1,150 @@
+/* Check execvpe script argument handling.
+   Copyright (C) 2016 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>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/stat.h>
+#include <sys/param.h>
+
+static char *fname1;
+static char *fname2;
+static char *logname;
+
+static void do_prepare (void);
+#define PREPARE(argc, argv) do_prepare ()
+static int do_test (void);
+#define TEST_FUNCTION do_test ()
+
+#include "../test-skeleton.c"
+
+static void
+do_prepare (void)
+{
+  int logfd = create_temp_file ("logfile", &logname);
+  close (logfd);
+
+  int fd1 = create_temp_file ("testscript", &fname1);
+  dprintf (fd1, "echo foo $1 $2 $3 > %s\n", logname);
+  fchmod (fd1, 0700);
+  close (fd1);
+
+  int fd2 = create_temp_file ("testscript", &fname2);
+  dprintf (fd2, "echo foo > %s\n", logname);
+  fchmod (fd2, 0700);
+  close (fd2);
+}
+
+static int
+run_script (const char *fname, char *args[])
+{
+  /* We want to test the `execvpe' function.  To do this we restart the
+     program with an additional parameter.  */
+  int status;
+  pid_t pid = fork ();
+  if (pid == 0)
+    {
+      execvpe (fname, args, NULL);
+
+      puts ("Cannot exec");
+      exit (EXIT_FAILURE);
+    }
+  else if (pid == (pid_t) -1)
+    {
+      puts ("Cannot fork");
+      return 1;
+    }
+
+  /* Wait for the child.  */
+  if (waitpid (pid, &status, 0) != pid)
+    {
+      puts ("Wrong child");
+      return 1;
+    }
+
+  if (WTERMSIG (status) != 0)
+    {
+      puts ("Child terminated incorrectly");
+      return 1;
+    }
+
+  return 0;
+}
+
+static int
+check_output (const char *expected)
+{
+  /* Check log output.  */
+  FILE *arq = fopen (logname, "r");
+  if (arq == NULL)
+    {
+      puts ("Error opening output file");
+      return 1;
+    }
+
+  char line[128];
+  if (fgets (line, sizeof (line), arq) == NULL)
+    {
+      puts ("Error reading output file");
+      return 1;
+    }
+  fclose (arq);
+
+  if (strcmp (line, expected) != 0)
+    {
+      puts ("Output file different than expected");
+      return 1;
+    }
+
+  return 0;
+}
+
+static int
+do_test (void)
+{
+  if  (setenv ("PATH", test_dir, 1) != 0)
+    {
+      puts ("setenv failed");
+      return 1;
+    }
+
+  /* First check resulting script run with some arguments results in correct
+     output file.  */
+  char *args1[] = { fname1, (char*) "1", (char *) "2", (char *) "3", NULL };
+  if (run_script (fname1,args1))
+    return 1;
+  if (check_output ("foo 1 2 3\n"))
+    return 1;
+
+  /* Same as before but with an expected empty argument list.  */
+  char *args2[] = { fname2, NULL };
+  if (run_script (fname2, args2))
+    return 1;
+  if (check_output ("foo\n"))
+    return 1;
+
+  /* Same as before but with an empty argument list.  */
+  char *args3[] = { NULL };
+  if (run_script (fname2, args3))
+    return 1;
+  if (check_output ("foo\n"))
+    return 1;
+
+  return 0;
+}