Use execveat syscall in fexecve (bug 22134)

By using execveat we no longer depend on /proc.  The execveat syscall was
introduced in 3.19, except for a few late comers.

2 files changed, 89 insertions, 1 deletions

diff --git a/posix/Makefile b/posix/Makefile
index 7188cba04c..7f77b07dfa 100644
--- a/posix/Makefile
+++ b/posix/Makefile
@@ -93,7 +93,7 @@ tests		:= test-errno tstgetopt testfnm runtests runptests \
 		   tst-fnmatch3 bug-regex36 tst-getaddrinfo5 \
 		   tst-posix_spawn-fd tst-posix_spawn-setsid \
 		   tst-posix_fadvise tst-posix_fadvise64 \
-		   tst-sysconf-empty-chroot tst-glob_symlinks
+		   tst-sysconf-empty-chroot tst-glob_symlinks tst-fexecve
 tests-internal	:= bug-regex5 bug-regex20 bug-regex33 \
 		   tst-rfc3484 tst-rfc3484-2 tst-rfc3484-3
 xtests		:= bug-ga2
diff --git a/posix/tst-fexecve.c b/posix/tst-fexecve.c
new file mode 100644
index 0000000000..2409102e21
--- /dev/null
+++ b/posix/tst-fexecve.c
@@ -0,0 +1,88 @@
+/* Copyright (C) 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 <unistd.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <sys/wait.h>
+
+#include <support/check.h>
+
+/* Try executing "/bin/sh -c true", using FD opened on /bin/sh.  */
+static int
+try_fexecve (int fd)
+{
+  pid_t pid = fork ();
+
+  if (pid == 0)
+    {
+      static const char *const argv[] = {
+	"/bin/sh", "-c", "true", NULL
+      };
+      fexecve (fd, (char *const *) argv, environ);
+      _exit (errno);
+    }
+  if (pid < 0)
+    FAIL_RET ("fork failed: %m");
+
+  pid_t termpid;
+  int status;
+  termpid = TEMP_FAILURE_RETRY (waitpid (pid, &status, 0));
+  if (termpid == -1)
+    FAIL_RET ("waitpid failed: %m");
+  if (termpid != pid)
+    FAIL_RET ("waitpid returned %ld != %ld",
+	      (long int) termpid, (long int) pid);
+  if (!WIFEXITED (status))
+    FAIL_RET ("child hasn't exited normally");
+
+  /* If fexecve is unimplemented mark this test as UNSUPPORTED.  */
+  if (WEXITSTATUS (status) == ENOSYS)
+    FAIL_UNSUPPORTED ("fexecve is unimplemented");
+
+  if (WEXITSTATUS (status) != 0)
+    {
+      errno = WEXITSTATUS (status);
+      FAIL_RET ("fexecve failed: %m");
+    }
+  return 0;
+}
+
+static int
+do_test (void)
+{
+  int fd;
+  int ret;
+
+  fd = open ("/bin/sh", O_RDONLY);
+  if (fd < 0)
+    FAIL_UNSUPPORTED ("/bin/sh cannot be opened: %m");
+  ret = try_fexecve (fd);
+  close (fd);
+
+#ifdef O_PATH
+  fd = open ("/bin/sh", O_RDONLY | O_PATH);
+  if (fd < 0)
+    FAIL_UNSUPPORTED ("/bin/sh cannot be opened (O_PATH): %m");
+  ret |= try_fexecve (fd);
+  close (fd);
+#endif
+
+  return ret;
+}
+
+#include <support/test-driver.c>