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, 157 insertions, 0 deletions

diff --git a/posix/tst-execvpe5.c b/posix/tst-execvpe5.c
new file mode 100644
index 0000000000..ffd764a639
--- /dev/null
+++ b/posix/tst-execvpe5.c
@@ -0,0 +1,157 @@
+/* General tests for execpve.
+   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 <errno.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <wait.h>
+
+
+/* Nonzero if the program gets called via `exec'.  */
+static int restart;
+
+
+#define CMDLINE_OPTIONS \
+  { "restart", no_argument, &restart, 1 },
+
+/* Prototype for our test function.  */
+extern void do_prepare (int argc, char *argv[]);
+extern int do_test (int argc, char *argv[]);
+
+#include "../test-skeleton.c"
+
+#define EXECVPE_KEY    "EXECVPE_ENV"
+#define EXECVPE_VALUE  "execvpe_test"
+
+
+static int
+handle_restart (void)
+{
+  /* First check if only one variable is passed on execvpe.  */
+  int env_count = 0;
+  for (char **e = environ; *e != NULL; ++e)
+    if (++env_count == INT_MAX)
+      {
+	printf ("Environment variable number overflow");
+	exit (EXIT_FAILURE);
+      }
+  if (env_count != 1)
+    {
+      printf ("Wrong number of environment variables");
+      exit (EXIT_FAILURE);
+    }
+
+  /* Check if the combinarion os "EXECVPE_ENV=execvpe_test"  */
+  const char *env = getenv (EXECVPE_KEY);
+  if (env == NULL)
+    {
+      printf ("Test environment variable not found");
+      exit (EXIT_FAILURE);
+    }
+
+  if (strncmp (env, EXECVPE_VALUE, sizeof (EXECVPE_VALUE)))
+    {
+      printf ("Test environment variable with wrong value");
+      exit (EXIT_FAILURE);
+    }
+
+  return 0;
+}
+
+
+int
+do_test (int argc, char *argv[])
+{
+  pid_t pid;
+  int status;
+
+  /* We must have
+     - one or four parameters left if called initially
+       + path for ld.so		optional
+       + "--library-path"	optional
+       + the library path	optional
+       + the application name
+  */
+
+  if (restart)
+    {
+      if (argc != 1)
+	{
+	  printf ("Wrong number of arguments (%d)\n", argc);
+	  exit (EXIT_FAILURE);
+	}
+
+      return handle_restart ();
+    }
+
+  if (argc != 2 && argc != 5)
+    {
+      printf ("Wrong number of arguments (%d)\n", argc);
+      exit (EXIT_FAILURE);
+    }
+
+  /* We want to test the `execvpe' function.  To do this we restart the
+     program with an additional parameter.  */
+  pid = fork ();
+  if (pid == 0)
+    {
+      /* This is the child.  Construct the command line.  */
+
+      /* We cast here to char* because the test itself does not modify neither
+	 the argument nor the environment list.  */
+      char *envs[] = { (char*)(EXECVPE_KEY "=" EXECVPE_VALUE), NULL };
+      if (argc == 5)
+	{
+	  char *args[] = { argv[1], argv[2], argv[3], argv[4],
+			   (char *) "--direct", (char *) "--restart", NULL };
+	  execvpe (args[0], args, envs);
+	}
+      else
+	{
+	  char *args[] = { argv[1], argv[1],
+			   (char *) "--direct", (char *) "--restart", NULL };
+	  execvpe (args[0], args, envs);
+	}
+
+      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;
+    }
+  status = WEXITSTATUS (status);
+
+  return status;
+}