/*BEGIN_LEGAL 
Intel Open Source License 

Copyright (c) 2002-2005 Intel Corporation 
All rights reserved. 
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modification, are permitted provided that the following conditions are
met:

Redistributions of source code must retain the above copyright notice,
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in binary form must reproduce the above copyright notice, this list of
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the Intel Corporation nor the names of its contributors may be used to
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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END_LEGAL */
#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <assert.h>
#include <setjmp.h>

#define __USE_GNU
#include <ucontext.h>

int p_safe_exit;

void install_signal_handler(void);
void signal_handler(int, siginfo_t *, void *);
void generate_hlt_segv(int val);

void install_signal_handler() {
  int ret_val;
  struct sigaction s_sigaction;
  struct sigaction *p_sigaction = &s_sigaction;

  /* Register the signal hander using the siginfo interface*/
  p_sigaction->sa_sigaction = signal_handler;
  p_sigaction->sa_flags = SA_SIGINFO;

  /* Don't mask any other signals */
  sigemptyset(&p_sigaction->sa_mask);

  ret_val = sigaction(SIGSEGV, p_sigaction, NULL);
  if(ret_val) {
    perror("ERROR, sigaction failed");
    exit(1);
  }
}

void generate_hlt_segv(int val) {
  int *p = 0;

  p_safe_exit = (int)&&safe_exit;

  printf("EIP of segfault: 0x%x (only accurate with if compiled with -O)\n", &&hlt_segfault);

 hlt_segfault:
  __asm__ __volatile__ ("hlt");


  printf("ERROR!\n");

 safe_exit:
  printf("EIP of safe exit: 0x%x\n", p_safe_exit);
}

void signal_handler(int signum, siginfo_t *siginfo, void *_uctxt) {
  int ret_val;
  ucontext_t *uctxt = (ucontext_t *)_uctxt;
  ucontext_t signal_ctxt;

  printf("signal %d (captured EIP: 0x%x)\n", signum,
         uctxt->uc_mcontext.gregs[REG_EIP]);

  uctxt->uc_mcontext.gregs[REG_EIP] = p_safe_exit;
}

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

  generate_hlt_segv(1);
  return 0;
}