#include <stdlib.h>
#include <signal.h>
#include <sys/signal.h>
#include <sys/types.h>
#include <sys/mman.h>
# include <fcntl.h>

# define zero_fd -1
# define map_flags MAP_ANON | MAP_PRIVATE
# define SIGSEGV_FAULT_ADDRESS_ROUNDOFF_BITS 0UL

unsigned long page;
int handler_called = 0;

void sigsegv_handler (int sig, siginfo_t *sip, void *ucp)
{
  void *fault_address = (void *) (sip->si_addr);
  handler_called++;
  if (handler_called == 10)
    exit (4);
  if (fault_address
      != (void*)((page + 0x678) & ~SIGSEGV_FAULT_ADDRESS_ROUNDOFF_BITS))
    exit (3);
  if (mprotect ((void *) page, 0x10000, PROT_READ | PROT_WRITE) < 0)
    exit (2);
}

void crasher (unsigned long p)
{
  *(int *) (p + 0x678) = 42;
}

int main ()
{
  void *p;
  struct sigaction action;
  /* Preparations.  */
  /* Setup some mmaped memory.  */
  p = mmap ((void *) 0x12340000, 0x10000, PROT_READ | PROT_WRITE, map_flags, zero_fd, 0);
  if (p == (void *)(-1))
    exit (2);
  page = (unsigned long) p;
  /* Make it read-only.  */
  if (mprotect ((void *) page, 0x10000, PROT_READ) < 0)
    exit (2);
  /* Install the SIGSEGV handler.  */
  sigemptyset(&action.sa_mask);
  action.sa_sigaction = &sigsegv_handler;
  action.sa_flags = SA_SIGINFO;
  sigaction (SIGSEGV, &action, (struct sigaction *) NULL);
  sigaction (SIGBUS, &action, (struct sigaction *) NULL);
  /* The first write access should invoke the handler and then complete.  */
  crasher (page);
  /* The second write access should not invoke the handler.  */
  crasher (page);
  /* Check that the handler was called only once.  */
  if (handler_called != 1)
    exit (1);
  /* Test passed!  */
  return 0;
}