elf: Testing infrastructure for ld.so DSO sorting (BZ #17645)

This is the first of a 2-part patch set that fixes slow DSO sorting behavior in
the dynamic loader, as reported in BZ #17645. In order to facilitate such a
large modification to the dynamic loader, this first patch implements a testing
framework for validating shared object sorting behavior, to enable comparison
between old/new sorting algorithms, and any later enhancements.

This testing infrastructure consists of a Python script
scripts/dso-ordering-test.py' which takes in a description language, consisting
of strings that describe a set of link dependency relations between DSOs, and
generates testcase programs and Makefile fragments to automatically test the
described situation, for example:

  a->b->c->d          # four objects linked one after another

  a->[bc]->d;b->c     # a depends on b and c, which both depend on d,
                      # b depends on c (b,c linked to object a in fixed order)

  a->b->c;{+a;%a;-a}  # a, b, c serially dependent, main program uses
                      # dlopen/dlsym/dlclose on object a

  a->b->c;{}!->[abc]  # a, b, c serially dependent; multiple tests generated
                      # to test all permutations of a, b, c ordering linked
                      # to main program

 (Above is just a short description of what the script can do, more
  documentation is in the script comments.)

Two files containing several new tests, elf/dso-sort-tests-[12].def are added,
including test scenarios for BZ #15311 and Redhat issue #1162810 [1].

Due to the nature of dynamic loader tests, where the sorting behavior and test
output occurs before/after main(), generating testcases to use
support/test-driver.c does not suffice to control meaningful timeout for ld.so.
Therefore a new utility program 'support/test-run-command', based on
test-driver.c/support_test_main.c has been added. This does the same testcase
control, but for a program specified through a command-line rather than at the
source code level. This utility is used to run the dynamic loader testcases
generated by dso-ordering-test.py.

[1] https://bugzilla.redhat.com/show_bug.cgi?id=1162810

Signed-off-by: Chung-Lin Tang  <cltang@codesourcery.com>
Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

1 files changed, 12 insertions, 0 deletions

diff --git a/support/support_test_main.c b/support/support_test_main.c
index 07e3cdd173..66a754b84f 100644
--- a/support/support_test_main.c
+++ b/support/support_test_main.c
@@ -228,6 +228,18 @@ run_test_function (int argc, char **argv, const struct test_config *config)
   while (wait_for_debugger)
     usleep (1000);
 
+  if (config->run_command_mode)
+    {
+      /* In run-command-mode, the child process executes the command line
+	 arguments as a new program.  */
+      char **argv_ = xmalloc (sizeof (char *) * argc);
+      memcpy (argv_, &argv[1], sizeof (char *) * (argc - 1));
+      argv_[argc - 1] = NULL;
+      execv (argv_[0], argv_);
+      printf ("error: should not return here\n");
+      exit (1);
+    }
+
   if (config->test_function != NULL)
     return config->test_function ();
   else if (config->test_function_argv != NULL)