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/* 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>
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 ();
/* 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 ();
/* 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 (! 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);
}
#define TEST_FUNCTION do_test ()
#include "../test-skeleton.c"
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