1 #include <signal.h>
2 #include <unistd.h>
3 #include <stdlib.h>
4 #include <sys/mman.h>
5 #include <stdio.h>
6 #include <mach/mach.h>
7 #include <mach/mach_vm.h>
8 
9 int *g_int_ptr = NULL;
10 size_t g_size = 10*sizeof(int);
11 
12 void
13 saction_handler(int signo, siginfo_t info, void *baton) {
14   printf("Got into handler.\n");   // stop here in the signal handler
15   kern_return_t success
16       = mach_vm_protect(mach_task_self(), (mach_vm_address_t) g_int_ptr,
17                         g_size, 0, VM_PROT_READ|VM_PROT_WRITE);
18   g_int_ptr[1] = 20;
19 }
20 int
21 main()
22 {
23   kern_return_t vm_result = vm_allocate(mach_task_self(), &g_int_ptr, g_size, VM_FLAGS_ANYWHERE);
24   for (int i = 0; i < 10; i++)
25     g_int_ptr[i] = i * 10;
26 
27   vm_result = mach_vm_protect(mach_task_self(), (mach_vm_address_t) g_int_ptr, g_size, 0, VM_PROT_NONE);
28   struct sigaction my_action;
29   sigemptyset(&my_action.sa_mask);
30   my_action.sa_handler = (void (*)(int)) saction_handler;
31   my_action.sa_flags = SA_SIGINFO;
32 
33   sigaction(SIGBUS, &my_action, NULL); // Stop here to get things going.
34   int local_value = g_int_ptr[1];
35   return local_value; // Break here to make sure we got past the signal handler
36 }
37