A CIL Tutorial - Department of Computer Science - ETH Zürich

CHAPTER 6. OVERRIDING FUNCTIONS 49
../ciltut-lib/src/tut6.c
int pthread_mutex_lock(pthread_mutex_t *m)
{
int res;
if (!pthread_mutex_lock_orig)
pthread_mutex_lock_orig = checked_dlsym(RTLD_NEXT, "pthread_mutex_lock");
res = pthread_mutex_lock_orig(m);
if (enable_lock_tracking) {
printf("thread: %d - pthread_mutex_lock(%p)\n", gettid(), m);
fflush(stdout);
}
return res;
}
int pthread_mutex_unlock(pthread_mutex_t *m)
{
int res;
if (!pthread_mutex_unlock_orig)
pthread_mutex_unlock_orig = checked_dlsym(RTLD_NEXT, "pthread_mutex_unlock");
if (enable_lock_tracking) {
printf("thread: %d - pthread_mutex_unlock(%p)\n", gettid(), m);
fflush(stdout);
}
res = pthread_mutex_unlock_orig(m);
return res;
}
void toggle_lock_tracking()
{
enable_lock_tracking = !enable_lock_tracking;
}
6.4 test/tut6.c
In this test, we simply declare a lock at global scope, then acquire and release it in the main function.
We do this simply to test that the wrapper functions we wrote in ciltut-lib/src/tut6.c are
correctly run whenever we call the lock and unlock functions.