elf/tst-execstack.c

   1 /* Test program for making nonexecutable stacks executable
   2    on load of a DSO that requires executable stacks.  */
   3
   4 #include <dlfcn.h>
   5 #include <stdio.h>
   6 #include <string.h>
   7 #include <unistd.h>
   8 #include <error.h>
   9
  10 static void
  11 print_maps (void)
  12 {
  13 #if 0
  14   char *cmd = NULL;
  15   asprintf (&cmd, "cat /proc/%d/maps", getpid ());
  16   system (cmd);
  17   free (cmd);
  18 #endif
  19 }
  20
  21 static void deeper (void (*f) (void));
  22
  23 #if USE_PTHREADS
  24 # include <pthread.h>
  25
  26 static void *
  27 tryme_thread (void *f)
  28 {
  29   (*((void (*) (void)) f)) ();
  30
  31   return 0;
  32 }
  33
  34 static pthread_barrier_t startup_barrier, go_barrier;
  35 static void *
  36 waiter_thread (void *arg)
  37 {
  38   void **f = arg;
  39   pthread_barrier_wait (&startup_barrier);
  40   pthread_barrier_wait (&go_barrier);
  41
  42   (*((void (*) (void)) *f)) ();
  43
  44   return 0;
  45 }
  46 #endif
  47
  48 static int
  49 do_test (void)
  50 {
  51   static void *f;               /* Address of this is used in other threads. */
  52
  53 #if USE_PTHREADS
  54   /* Create some threads while stacks are nonexecutable.  */
  55   #define N 5
  56   pthread_t thr[N];
  57
  58   pthread_barrier_init (&startup_barrier, NULL, N + 1);
  59   pthread_barrier_init (&go_barrier, NULL, N + 1);
  60
  61   for (int i = 0; i < N; ++i)
  62     {
  63       int rc = pthread_create (&thr[i], NULL, &waiter_thread, &f);
  64       if (rc)
  65         error (1, rc, "pthread_create");
  66     }
  67
  68   /* Make sure they are all there using their stacks.  */
  69   pthread_barrier_wait (&startup_barrier);
  70   puts ("threads waiting");
  71 #endif
  72
  73   print_maps ();
  74
  75   /* Loading this module should force stacks to become executable.  */
  76   void *h = dlopen ("tst-execstack-mod.so", RTLD_LAZY);
  77   if (h == NULL)
  78     {
  79       printf ("cannot load: %s\n", dlerror ());
  80       return 1;
  81     }
  82
  83   f = dlsym (h, "tryme");
  84   if (f == NULL)
  85     {
  86       printf ("symbol not found: %s\n", dlerror ());
  87       return 1;
  88     }
  89
  90   /* Test if that really made our stack executable.
  91      The `tryme' function should crash if not.  */
  92
  93   (*((void (*) (void)) f)) ();
  94
  95   print_maps ();
  96
  97   /* Test that growing the stack region gets new executable pages too.  */
  98   deeper ((void (*) (void)) f);
  99
 100   print_maps ();
 101
 102 #if USE_PTHREADS
 103   /* Test that a fresh thread now gets an executable stack.  */
 104   {
 105     pthread_t th;
 106     int rc = pthread_create (&th, NULL, &tryme_thread, f);
 107     if (rc)
 108       error (1, rc, "pthread_create");
 109   }
 110
 111   puts ("threads go");
 112   /* The existing threads' stacks should have been changed.
 113      Let them run to test it.  */
 114   pthread_barrier_wait (&go_barrier);
 115
 116   pthread_exit (0);
 117 #endif
 118
 119   return 0;
 120 }
 121
 122 static void
 123 deeper (void (*f) (void))
 124 {
 125   char stack[1100 * 1024];
 126   memfrob (stack, sizeof stack);
 127   (*f) ();
 128   memfrob (stack, sizeof stack);
 129 }
 130
 131
 132 #define TEST_FUNCTION do_test ()
 133 #include "../test-skeleton.c"