A CIL Tutorial - Department of Computer Science - ETH Zürich

CHAPTER 6. OVERRIDING FUNCTIONS 50
# include
# include
../test/tut6.c
int counter = 0;
pthread_mutex_t mtx = PTHREAD_MUTEX_INITIALIZER;
int main()
{
toggle_lock_tracking();
pthread_mutex_lock(&mtx);
counter++;
pthread_mutex_unlock(&mtx);
return 0;
}
Now, we can compile this test by doing:
$ ciltutcc --enable-tut6 -lpthread -o tut6 test/tut6.c
Then, when we run tut6, we should get something similar to the following output:
$ ./tut6
thread:
thread:
32646 - pthread mutex lock(0x602180)
32646 - pthread mutex unlock(0x602180)
6.5 Further Reading
Many researchers have studied overriding memory allocation calls (along with the instrumentation
of some memory accesses) with the goal of catching memory management errors. Examples are
Libsafe [2], LibsafePlus [1], and HeapShield [3] (which is a part of DieHard [4]).
The Trickle [5] userspace bandwidth shaper operates by using the dynamic linker to override IO
calls with ones that track the number of bytes sent per unit time. Then, it puts the calling process
to sleep when the sending or receiving rate exceeds a user given limit.