segfault benchmark.

main.cpp

#include <sys/mman.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/time.h>

void *mem;
#define MEM_SIZE (8000*0x1000)

inline double gettime ()
{
    timeval tv;
    gettimeofday (&tv, NULL);
    return double (tv.tv_sec) + 0.000001 * tv.tv_usec;
}

typedef long unsigned int u64;

void sigsegv_handler(int sig, siginfo_t *info, void *raw_context) {
  if(info->si_code != SEGV_ACCERR)
    return;

  ucontext_t *context = (ucontext_t *)raw_context;

  mcontext_t *ctx = &context->uc_mcontext;

  u64 bad_address = (u64)info->si_addr;
  u64 bad_page = bad_address & (~0xfff);

  mprotect((void *)bad_page, 0x1000, PROT_READ|PROT_WRITE);
}

void installHandler() {
  struct sigaction sa;
  sa.sa_handler = nullptr;
  sa.sa_sigaction = &sigsegv_handler;
  sa.sa_flags = SA_SIGINFO;
  sigemptyset(&sa.sa_mask);
  sigaction(SIGSEGV, &sa, nullptr);
}

int main(int argc, char **argv) {
  installHandler();

  // allocate us some memory;
  mem = mmap(NULL, MEM_SIZE, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);

  if ((u64)mem == -1) {
    perror("mmap");
    return -1;
  }


  mprotect(mem, MEM_SIZE, PROT_READ);

  double start = gettime();

  for (int i = 0; i < 8000; i+= 1)
    ((unsigned char*)mem)[i*0x1000] = 0xcc;

  double end = gettime();

  munmap(mem, MEM_SIZE);

  printf("time: %gus\n", (end - start)*1000000);

  return 0;
}

Makefile

benchmark: main.cpp
	g++ main.cpp -O3 -g -std=c++11 -o benchmark