* sysdeps/i386/dl-machine.h (RTLD_START): Set __libc_stack_end before

	calling _dl_start, using GOTOFF access.

	* configure.in (libc_cv_z_execstack): New check.
	* configure: Regenerated.
	* config.make.in (have-z-execstack): New variable set by it.
	* elf/tst-execstack.c: New file.
	* elf/tst-execstack-mod.c: New file.
	* elf/tst-execstack-needed.c: New file.
	* elf/Makefile (tests-execstack-yes, modules-execstack-yes): New
	variables.
	(tests, modules-names): Conditionally include them.
	(distribute): Add tst-execstack-mod.c here.
	($(objpfx)tst-execstack, $(objpfx)tst-execstack.out): New targets.
	(LDFLAGS-tst-execstack, LDFLAGS-tst-execstack-mod): New variables.
	($(objpfx)tst-execstack-needed): New target.
	(LDFLAGS-tst-execstack-needed): New variable.

	* sysdeps/generic/ldsodefs.h (struct rtld_global): Add _dl_stack_flags
	and _dl_make_stack_executable_hook.  Declare _dl_make_stack_executable.
	* elf/rtld.c (_rtld_global): Add initializer for _dl_stack_flags.
	(dl_main): Reset _dl_stack_flags according to PT_GNU_STACK phdr.
	Initialize _dl_make_stack_executable_hook.
	* elf/dl-support.c: Define those new variables.
	(_dl_non_dynamic_init): Scan phdrs for PT_GNU_STACK.
	(_dl_phdr): Fix type.
	* elf/dl-load.c (_dl_map_object_from_fd): Grok PT_GNU_STACK phdr and
	enable execute permission for the stack if necessary.
	* sysdeps/generic/dl-execstack.c: New file.
	* elf/Makefile (dl-routines): Add it.
	* elf/Versions (ld: GLIBC_PRIVATE): Add _dl_make_stack_executable.
	* sysdeps/unix/sysv/linux/dl-execstack.c: New file.

1 files changed, 133 insertions, 0 deletions

diff --git a/elf/tst-execstack.c b/elf/tst-execstack.c
new file mode 100644
index 0000000..21eaa9b
--- /dev/null
+++ b/elf/tst-execstack.c
@@ -0,0 +1,133 @@
+/* Test program for making nonexecutable stacks executable
+   on load of a DSO that requires executable stacks.  */
+
+#include <dlfcn.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include <error.h>
+
+static void
+print_maps (void)
+{
+#if 0
+  char *cmd = NULL;
+  asprintf (&cmd, "cat /proc/%d/maps", getpid ());
+  system (cmd);
+  free (cmd);
+#endif
+}
+
+static void deeper (void (*f) (void));
+
+#if USE_PTHREADS
+# include <pthread.h>
+
+static void *
+tryme_thread (void *f)
+{
+  (*((void (*) (void)) f)) ();
+
+  return 0;
+}
+
+static pthread_barrier_t startup_barrier, go_barrier;
+static void *
+waiter_thread (void *arg)
+{
+  void **f = arg;
+  pthread_barrier_wait (&startup_barrier);
+  pthread_barrier_wait (&go_barrier);
+
+  (*((void (*) (void)) *f)) ();
+
+  return 0;
+}
+#endif
+
+static int
+do_test (void)
+{
+  void *f;
+
+#if USE_PTHREADS
+  /* Create some threads while stacks are nonexecutable.  */
+  #define N 5
+  pthread_t thr[N];
+
+  pthread_barrier_init (&startup_barrier, NULL, N + 1);
+  pthread_barrier_init (&go_barrier, NULL, N + 1);
+
+  for (int i = 0; i < N; ++i)
+    {
+      int rc = pthread_create (&thr[i], NULL, &waiter_thread, &f);
+      if (rc)
+	error (1, rc, "pthread_create");
+    }
+
+  /* Make sure they are all there using their stacks.  */
+  pthread_barrier_wait (&startup_barrier);
+  puts ("threads waiting");
+#endif
+
+  print_maps ();
+
+  /* Loading this module should force stacks to become executable.  */
+  void *h = dlopen ("tst-execstack-mod.so", RTLD_LAZY);
+  if (h == NULL)
+    {
+      printf ("cannot load: %s\n", dlerror ());
+      return 1;
+    }
+
+  f = dlsym (h, "tryme");
+  if (f == NULL)
+    {
+      printf ("symbol not found: %s\n", dlerror ());
+      return 1;
+    }
+
+  /* Test if that really made our stack executable.
+     The `tryme' function should crash if not.  */
+
+  (*((void (*) (void)) f)) ();
+
+  print_maps ();
+
+  /* Test that growing the stack region gets new executable pages too.  */
+  deeper ((void (*) (void)) f);
+
+  print_maps ();
+
+#if USE_PTHREADS
+  /* Test that a fresh thread now gets an executable stack.  */
+  {
+    pthread_t th;
+    int rc = pthread_create (&th, NULL, &tryme_thread, f);
+    if (rc)
+      error (1, rc, "pthread_create");
+  }
+
+  puts ("threads go");
+  /* The existing threads' stacks should have been changed.
+     Let them run to test it.  */
+  pthread_barrier_wait (&go_barrier);
+
+  pthread_exit (0);
+#endif
+
+  return 0;
+}
+
+static void
+deeper (void (*f) (void))
+{
+  char stack[1100 * 1024];
+  memfrob (stack, sizeof stack);
+  (*f) ();
+  memfrob (stack, sizeof stack);
+}
+
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"