/*
 * Copyright 2002-2019 Intel Corporation.
 * 
 * This software is provided to you as Sample Source Code as defined in the accompanying
 * End User License Agreement for the Intel(R) Software Development Products ("Agreement")
 * section 1.L.
 * 
 * This software and the related documents are provided as is, with no express or implied
 * warranties, other than those that are expressly stated in the License.
 */

// features.h does not exist on FreeBSD
#if !defined(TARGET_BSD) && !defined(TARGET_MAC)
// features initializes the system's state, including the state of __USE_GNU
#include <features.h>
#endif

// If __USE_GNU is defined, we don't need to do anything.
// If we defined it ourselves, we need to undefine it later.
#ifndef __USE_GNU
    #define __USE_GNU
    #define APP_UNDEF_USE_GNU
#endif

#include <sys/ucontext.h>

// If we defined __USE_GNU ourselves, we need to undefine it here.
#ifdef APP_UNDEF_USE_GNU
    #undef __USE_GNU
    #undef APP_UNDEF_USE_GNU
#endif

#include <stdlib.h>
#include <signal.h>
#include <assert.h>
#include <setjmp.h>
#include <string.h>
#include <pthread.h>
#include <stdio.h>
#include <errno.h>

pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
pthread_attr_t thread_attr;
int thread_alive = 0;

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 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: %p, top: %p, size: %ld\n",
         ss.ss_sp, (unsigned char *)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: %p, top: %p, size: %ld, disabled = %s\n",
         oss.ss_sp, (unsigned char *)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: %p, top: %p, size: %ld, disabled = %s\n",
         oss.ss_sp, (unsigned char *)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;

  /* Mask all other signals */
  ret_val = sigfillset(&p_sigaction->sa_mask);
  if(ret_val) {
    perror("ERROR, sigfillset failed");
    exit(1);
  }

  ret_val = sigaction(SIGUSR1, p_sigaction, NULL);
  if(ret_val) {
    perror("ERROR, sigaction failed");
    exit(1);
  }
}

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;

#ifdef TARGET_MAC
  printf("signal %d (captured EIP: 0x%x)\n", signum,
         uctxt->uc_mcontext->__ss.__eip);
#else
  printf("signal %d (captured EIP: 0x%x)\n", signum,
         uctxt->uc_mcontext.gregs[REG_EIP]);
#endif
}

void *thread_start(void *arg) {
  int ret_val, sig;
  sigset_t sigmask;

  printf("sigsuspend...\n");

  lock();
  thread_alive = 1;
  unlock();

  ret_val = sigfillset(&sigmask);
  if(ret_val) {
    perror("ERROR, sigfillset failed");
    exit(1);
  }

  ret_val = sigdelset(&sigmask, SIGUSR1);
  if(ret_val) {
    perror("ERROR, sigdelset failed");
    exit(1);
  }

  ret_val = sigsuspend(&sigmask);
  assert(ret_val && (errno == EINTR));

  printf("unsuspended\n");

  printf("sigwaitinfo...\n");

  lock();
  thread_alive = 2;
  unlock();

  ret_val = sigfillset(&sigmask);
  if(ret_val) {
    perror("ERROR, sigfillset failed");
    exit(1);
  }

  ret_val = sigprocmask(SIG_BLOCK, &sigmask, NULL);
  if(ret_val) {
    perror("ERROR, sigprocmask failed");
    exit(1);
  }

  ret_val = sigemptyset(&sigmask);
  if(ret_val) {
    perror("ERROR, sigemptyset failed");
    exit(1);
  }

  ret_val = sigaddset(&sigmask, SIGUSR1);
  if(ret_val) {
    perror("ERROR, sigaddset failed");
    exit(1);
  }

#ifdef TARGET_MAC
  ret_val = sigwait(&sigmask, &sig);
  printf("Ret val: %d %d\n", ret_val, sig);
  assert(sig == SIGUSR1);
#else
  ret_val = sigwaitinfo(&sigmask, NULL);
  assert(ret_val == SIGUSR1);
#endif

  printf("unsuspended\n");
  return 0;
}

int main(int argc, char **argv) {
  pthread_t tid;
  int ret_val;
  void *thread_ret;
  int cont = 0;

  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);
  }

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

  while(!cont) {
    lock();
    if(thread_alive == 1) cont = 1;
    unlock();
  }

  ret_val = pthread_kill(tid, SIGUSR1);
  if(ret_val) {
    perror("ERROR: pthread_kill failed");
    exit(1);
  }

  cont = 0;
  while(!cont) {
    lock();
    if(thread_alive == 2) cont = 1;
    unlock();
  }

  ret_val = pthread_kill(tid, SIGUSR1);
  if(ret_val) {
    perror("ERROR: pthread_kill failed");
    exit(1);
  }

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