Prepare for radical source tree reorganization. zack/build-layout-experiment

All top-level files and directories are moved into a temporary storage
directory, REORG.TODO, except for files that will certainly still
exist in their current form at top level when we're done (COPYING,
COPYING.LIB, LICENSES, NEWS, README), all old ChangeLog files (which
are moved to the new directory OldChangeLogs, instead), and the
generated file INSTALL (which is just deleted; in the new order, there
will be no generated files checked into version control).

1 files changed, 236 insertions, 0 deletions

diff --git a/REORG.TODO/elf/tst-execstack.c b/REORG.TODO/elf/tst-execstack.c
new file mode 100644
index 0000000000..114f341d76
--- /dev/null
+++ b/REORG.TODO/elf/tst-execstack.c
@@ -0,0 +1,236 @@
+/* Test program for making nonexecutable stacks executable
+   on load of a DSO that requires executable stacks.  */
+
+#include <dlfcn.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include <error.h>
+#include <stackinfo.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 bool allow_execstack = true;
+
+
+static int
+do_test (void)
+{
+  /* Check whether SELinux is enabled and disallows executable stacks.  */
+  FILE *fp = fopen ("/selinux/enforce", "r");
+  if (fp != NULL)
+    {
+      char *line = NULL;
+      size_t linelen = 0;
+
+      bool enabled = false;
+      ssize_t n = getline (&line, &linelen, fp);
+      if (n > 0 && line[0] != '0')
+	enabled = true;
+
+      fclose (fp);
+
+      if (enabled)
+	{
+	  fp = fopen ("/selinux/booleans/allow_execstack", "r");
+	  if (fp != NULL)
+	    {
+	      n = getline (&line, &linelen, fp);
+	      if (n > 0 && line[0] == '0')
+		allow_execstack = false;
+	    }
+
+	  fclose (fp);
+	}
+    }
+
+  printf ("executable stacks %sallowed\n", allow_execstack ? "" : "not ");
+
+  static void *f;		/* Address of this is used in other threads. */
+
+#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 ();
+
+#if USE_PTHREADS
+  void *old_stack_addr, *new_stack_addr;
+  size_t stack_size;
+  pthread_t me = pthread_self ();
+  pthread_attr_t attr;
+  int ret = 0;
+
+  ret = pthread_getattr_np (me, &attr);
+  if (ret)
+    {
+      printf ("before execstack: pthread_getattr_np returned error: %s\n",
+	      strerror (ret));
+      return 1;
+    }
+
+  ret = pthread_attr_getstack (&attr, &old_stack_addr, &stack_size);
+  if (ret)
+    {
+      printf ("before execstack: pthread_attr_getstack returned error: %s\n",
+	      strerror (ret));
+      return 1;
+    }
+# if _STACK_GROWS_DOWN
+    old_stack_addr += stack_size;
+# else
+    old_stack_addr -= stack_size;
+# endif
+#endif
+
+  /* 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 allow_execstack;
+    }
+
+  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 ();
+
+#if USE_PTHREADS
+  ret = pthread_getattr_np (me, &attr);
+  if (ret)
+    {
+      printf ("after execstack: pthread_getattr_np returned error: %s\n",
+	      strerror (ret));
+      return 1;
+    }
+
+  ret = pthread_attr_getstack (&attr, &new_stack_addr, &stack_size);
+  if (ret)
+    {
+      printf ("after execstack: pthread_attr_getstack returned error: %s\n",
+	      strerror (ret));
+      return 1;
+    }
+
+# if _STACK_GROWS_DOWN
+    new_stack_addr += stack_size;
+# else
+    new_stack_addr -= stack_size;
+# endif
+
+  /* It is possible that the dlopen'd module may have been mmapped just below
+     the stack.  The stack size is taken as MIN(stack rlimit size, end of last
+     vma) in pthread_getattr_np.  If rlimit is set high enough, it is possible
+     that the size may have changed.  A subsequent call to
+     pthread_attr_getstack returns the size and (bottom - size) as the
+     stacksize and stackaddr respectively.  If the size changes due to the
+     above, then both stacksize and stackaddr can change, but the stack bottom
+     should remain the same, which is computed as stackaddr + stacksize.  */
+  if (old_stack_addr != new_stack_addr)
+    {
+      printf ("Stack end changed, old: %p, new: %p\n",
+	      old_stack_addr, new_stack_addr);
+      return 1;
+    }
+  printf ("Stack address remains the same: %p\n", old_stack_addr);
+#endif
+
+  /* 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 ((void *) (long int) (! allow_execstack));
+#endif
+
+  return ! allow_execstack;
+}
+
+static void
+deeper (void (*f) (void))
+{
+  char stack[1100 * 1024];
+  memfrob (stack, sizeof stack);
+  (*f) ();
+  memfrob (stack, sizeof stack);
+}
+
+
+#include <support/test-driver.c>