/*BEGIN_LEGAL 
Intel Open Source License 

Copyright (c) 2002-2005 Intel Corporation 
All rights reserved. 
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:

Redistributions of source code must retain the above copyright notice,
this list of conditions and the following disclaimer.  Redistributions
in binary form must reproduce the above copyright notice, this list of
conditions and the following disclaimer in the documentation and/or
other materials provided with the distribution.  Neither the name of
the Intel Corporation nor the names of its contributors may be used to
endorse or promote products derived from this software without
specific prior written permission.
 
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE INTEL OR
ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
END_LEGAL */
#include <stdlib.h>
#include <signal.h>
#include <assert.h>
#include <setjmp.h>
#include <string.h>
#include <pthread.h>
#include <stdio.h>

#define __USE_GNU
#include <ucontext.h>

pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
pthread_attr_t thread_attr;
int p_safe_exit;

void setup_signal_stack(void);
void print_signal_stack(void);
void install_signal_handler(void);
void signal_handler(int, siginfo_t *, void *);
void generate_segv(int val);
void lock();
void unlock();
void *thread_gen_segv(void *);

void printSignalMask()
{
  sigset_t maskSet;
  int maskBits;
  sigprocmask(0, NULL, &maskSet);
  int i;
  for (i=32; i>0; i--)
    maskBits = (maskBits << 1) | sigismember(&maskSet, i); 
  printf("signal mask: 0x%0.8x\n", maskBits);
}

void setup_signal_stack() {
  int ret_val;
  stack_t ss;
  stack_t oss;

  ss.ss_sp = malloc(SIGSTKSZ);
  assert(ss.ss_sp && "malloc failure");
  
  ss.ss_size = SIGSTKSZ;
  ss.ss_flags = 0;

  printf("ESP of alternate stack: 0x%x, top: 0x%x, size: %d\n",
         ss.ss_sp, ss.ss_sp + ss.ss_size, ss.ss_size);

  ret_val = sigaltstack(&ss, &oss);
  if(ret_val) {
    perror("ERROR, sigaltstack failed");
    exit(1);
  }

  printf("ESP of original stack: 0x%x, top: 0x%x, size: %d, disabled = %s\n",
         oss.ss_sp, oss.ss_sp + oss.ss_size, oss.ss_size,
         (oss.ss_flags & SS_DISABLE) ? "true" : "false");
}

void print_signal_stack() {
  int ret_val;
  stack_t oss;

  ret_val = sigaltstack(NULL, &oss);
  if(ret_val) {
    perror("ERROR, sigaltstack failed");
    exit(1);
  }

  printf("ESP of original stack: 0x%x, top: 0x%x, size: %d, disabled = %s\n",
         oss.ss_sp, oss.ss_sp + oss.ss_size, oss.ss_size,
         (oss.ss_flags & SS_DISABLE) ? "true" : "false");
}

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 | SA_ONSTACK;

  /* 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_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", &&segfault);

  /* Encourage the compiler to put val into a register so that the
     statement after the 'segfault' label is more likely to be the
     exact location of a mov to 0x0 */
  val++;

 segfault:
  *p = val;

  printf("ERROR!\n");

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

void lock() {
  int ret_val;
  
  ret_val = pthread_mutex_lock(&mutex);
  if(ret_val) {
    perror("ERROR, pthread_mutex_lock failed");
  }

  fflush(stdout);
}

void unlock() {
  int ret_val;

  fflush(stdout);

  ret_val = pthread_mutex_unlock(&mutex);
  if(ret_val) {
    perror("ERROR, pthread_mutex_unlock failed");
  }
}
void signal_handler(int signum, siginfo_t *siginfo, void *_uctxt) {
  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]);
  printSignalMask();

  int ret_val = getcontext(&signal_ctxt);
  if(ret_val) {
    perror("ERROR, getcontext failed");
    exit(1);
  }
  printf("signal handler stack: 0x%0.8x\n", signal_ctxt.uc_mcontext.gregs[REG_ESP]);


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

void *thread_start(void *arg) {
  int ret_val;

  lock();

  printf("thread arg = %d\n", (unsigned int)arg);

  if(arg) {
    setup_signal_stack();
  }
  else {
    print_signal_stack();
  }

  generate_segv(1);

  unlock();

  if(arg == (void *)2) {
    pthread_t tid;
    void *thread_ret;

    ret_val = pthread_create(&tid, NULL, thread_start, NULL);
    if(ret_val) {
      perror("ERROR, pthread_create failed");
      exit(1);
    }

    lock();
    printf("created thread 0x%lx\n", tid);
    unlock();

    ret_val = pthread_join(tid, &thread_ret);
    if(ret_val) {
      perror("ERROR, pthread_join failed");
      exit(1);
    }

    ret_val = pthread_create(&tid, NULL, thread_start, (void *)1);
    if(ret_val) {
      perror("ERROR, pthread_create failed");
      exit(1);
    }

    lock();
    printf("created thread 0x%lx\n", tid);
    unlock();

    ret_val = pthread_join(tid, &thread_ret);
    if(ret_val) {
      perror("ERROR, pthread_join failed");
      exit(1);
    }
  }

  pthread_exit(0);
}

int main(int argc, char **argv) {
  pthread_t tid;
  int ret_val;
  void *thread_ret;

  setup_signal_stack();
  install_signal_handler();

  ret_val = pthread_create(&tid, NULL, thread_start, NULL);
  if(ret_val) {
    perror("ERROR, pthread_create failed");
    exit(1);
  }

  lock();
  printf("created thread 0x%lx\n", tid);
  unlock();

  ret_val = pthread_join(tid, &thread_ret);
  if(ret_val) {
    perror("ERROR, pthread_join failed");
    exit(1);
  }

  ret_val = pthread_create(&tid, NULL, thread_start, (void *)1);
  if(ret_val) {
    perror("ERROR, pthread_create failed");
    exit(1);
  }

  lock();
  printf("created thread 0x%lx\n", tid);
  unlock();

  ret_val = pthread_join(tid, &thread_ret);
  if(ret_val) {
    perror("ERROR, pthread_join failed");
    exit(1);
  }

  ret_val = pthread_create(&tid, NULL, thread_start, (void *)2);
  if(ret_val) {
    perror("ERROR, pthread_create failed");
    exit(1);
  }

  lock();
  printf("created thread 0x%lx\n", tid);
  unlock();

  ret_val = pthread_join(tid, &thread_ret);
  if(ret_val) {
    perror("ERROR, pthread_join failed");
    exit(1);
  }
}