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glibc/elf/tst-execstack.c
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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> | |
#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); | |
} | |
#define TEST_FUNCTION do_test () | |
#include "../test-skeleton.c" |