sigsegv.c

// blox.c

#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <time.h>
#include "common/log.h"
#include "sigsegv.h"

#define TOTAL_FAULTS 0x4000

#ifndef MORELLO
#include <mach/task.h>
#include <mach/mach_init.h>
#include <mach/mach_port.h>
#endif

int count = 0;
static sigsegv_dispatcher dispatcher;

static int area_handler(void *fault_address, void *user_arg) {
  uintptr_t area = *(uintptr_t *)user_arg;
  if (!((uintptr_t)fault_address >= area && (uintptr_t)fault_address - area < TOTAL_FAULTS)) {
    abort();
  }
  if (mprotect((void *)area, TOTAL_FAULTS, PROT_READ | PROT_WRITE) == 0) {
    count++;
    return 1;
  }
  return 0;
}

static int handler(void *fault_address, int serious) {
  return sigsegv_dispatch(&dispatcher, fault_address);
}

static inline void silence_xcode() {
#ifndef MORELLO
  int ret = task_set_exception_ports(mach_task_self(), EXC_MASK_BAD_ACCESS, MACH_PORT_NULL, EXCEPTION_DEFAULT, 0);
  /* Add auto breakpoint `proc hand -p true -s false SIGSEGV / SIGBUS` to lldb / xcode */
#endif
}

int main(int argc, const char **argv) {
  silence_xcode();
  sigsegv_init(&dispatcher);
  sigsegv_install_handler(&handler);
  void *p = mmap((void *)0x12340000, TOTAL_FAULTS, (PROT_READ | PROT_WRITE), MAP_ANON | MAP_PRIVATE, -1, 0);
  if (p == (void *)(-1)) {
    BLOX_ERROR("mmap failed!");
    exit(2);
  }
  BLOX_DEBUG("mmap succeeded!");
  uintptr_t area1 = (uintptr_t)p;
  sigsegv_register(&dispatcher, (void *)area1, TOTAL_FAULTS, &area_handler, &area1);
  if (mprotect((void *)area1, TOTAL_FAULTS, PROT_NONE) < 0) {
    BLOX_ERROR("mprotect area1 failed!");
    exit(2);
  }
  char *c = (char *)p;
  clock_t start = clock();
  for (int i = 0; i < TOTAL_FAULTS; i++) {
    c[i] = 'b';
    if (mprotect((void *)area1, TOTAL_FAULTS, PROT_NONE) < 0) {
      BLOX_ERROR("mprotect area1 failed!");
      exit(2);
    }
  }
  clock_t end = clock();
  float seconds = (float)(end - start) / CLOCKS_PER_SEC;
  int __faults = TOTAL_FAULTS;
  printf("Took : %0.3f seconds to cause %0.0f faults!\n", seconds, (float)__faults);
  printf("final count = %0.0f\n", (float)count);
  printf("%0.0f\n", (float)c[100]);
  return 0;
}