/*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
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END_LEGAL */
#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <assert.h>
#include <setjmp.h>
#include <sys/types.h>
#include <linux/unistd.h>

#define __USE_GNU
#include <ucontext.h>

ucontext_t *p_saved_ctxt;

void install_signal_handlers(void);
void segv_signal_handler(int, siginfo_t *, void *);
void usr2_signal_handler(int, siginfo_t *, void *);
void generate_segv(int val);
void print_fp_regs(struct _libc_fpstate *);
void print_fp_reg(struct _libc_fpreg *);

void install_signal_handlers() {
  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 = segv_signal_handler;
  p_sigaction->sa_flags = SA_SIGINFO;

  /* mask all other signals */
  sigfillset(&p_sigaction->sa_mask);

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

  p_sigaction->sa_sigaction = usr2_signal_handler;
  p_sigaction->sa_flags = SA_SIGINFO;

  ret_val = sigaction(SIGUSR2, p_sigaction, NULL);
  if(ret_val) {
    perror("ERROR, sigaction failed");
    exit(1);
  }
}

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

  printf("EIP of segfault: 0x%x\n", &&segfault);

  __asm__ __volatile__ (
           "movl $0x600D1, %eax;\
            movl $0x600D2, %ebx;\
            movl $0x600D3, %ecx;\
            movl $0x600D4, %edx;\
            movl $0x600D5, %edi;\
            movl $0x600D6, %esi;\
            movl $0x600D7, %ebp");

 segfault:
  __asm__ __volatile__ (
           "movl (0x0), %ecx");
}

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

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

  assert(uctxt->uc_mcontext.fpregs);
  printf("FCW: 0x%hx\n",uctxt->uc_mcontext.fpregs->cw);
  print_fp_regs(uctxt->uc_mcontext.fpregs);

  tid = getpid();
  ret_val = kill(tid, SIGUSR2);
}

void print_fp_regs(struct _libc_fpstate *fpstate) {
  int i;
  for(i = 0; i < 8; i++) {
    printf("reg %d: ", i);
    print_fp_reg(&fpstate->_st[i]);
    printf("\n");
  }
}

void print_fp_reg(struct _libc_fpreg *p_reg) {
  printf("exponent = 0x%hx significand = 0x%hx%hx%hx%hx",
         p_reg->exponent, p_reg->significand[3], p_reg->significand[2],
         p_reg->significand[1], p_reg->significand[0]);
}

void usr2_signal_handler(int signum, siginfo_t *siginfo, void *_uctxt) {
  int ret_val;
  ucontext_t *uctxt = (ucontext_t *)_uctxt;
  ucontext_t signal_ctxt;
  pid_t tid;

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

  // Change contexts

  assert(uctxt->uc_mcontext.fpregs);
  printf("FCW: 0x%hx\n",uctxt->uc_mcontext.fpregs->cw);
  print_fp_regs(uctxt->uc_mcontext.fpregs);

  uctxt->uc_mcontext.gregs[REG_EDI] = p_saved_ctxt->uc_mcontext.gregs[REG_EDI];
  uctxt->uc_mcontext.gregs[REG_ESI] = p_saved_ctxt->uc_mcontext.gregs[REG_ESI];
  uctxt->uc_mcontext.gregs[REG_EBP] = p_saved_ctxt->uc_mcontext.gregs[REG_EBP];
  uctxt->uc_mcontext.gregs[REG_ESP] = p_saved_ctxt->uc_mcontext.gregs[REG_ESP];
  uctxt->uc_mcontext.gregs[REG_EBX] = p_saved_ctxt->uc_mcontext.gregs[REG_EBX];
  uctxt->uc_mcontext.gregs[REG_EDX] = p_saved_ctxt->uc_mcontext.gregs[REG_EDX];
  uctxt->uc_mcontext.gregs[REG_ECX] = p_saved_ctxt->uc_mcontext.gregs[REG_ECX];
  uctxt->uc_mcontext.gregs[REG_EAX] = p_saved_ctxt->uc_mcontext.gregs[REG_EAX];
  uctxt->uc_mcontext.gregs[REG_EIP] = p_saved_ctxt->uc_mcontext.gregs[REG_EIP];
  uctxt->uc_mcontext.gregs[REG_EFL] = p_saved_ctxt->uc_mcontext.gregs[REG_EFL];

  // getcontext() doesn't appear to properly set the segment registers,
  // so don't mess with them.
  //uctxt->uc_mcontext.gregs[REG_CS] = p_saved_ctxt->uc_mcontext.gregs[REG_CS];
  //uctxt->uc_mcontext.gregs[REG_SS] = p_saved_ctxt->uc_mcontext.gregs[REG_SS];
  //uctxt->uc_mcontext.gregs[REG_DS] = p_saved_ctxt->uc_mcontext.gregs[REG_DS];
  //uctxt->uc_mcontext.gregs[REG_ES] = p_saved_ctxt->uc_mcontext.gregs[REG_ES];
  //uctxt->uc_mcontext.gregs[REG_FS] = p_saved_ctxt->uc_mcontext.gregs[REG_FS];
  //uctxt->uc_mcontext.gregs[REG_GS] = p_saved_ctxt->uc_mcontext.gregs[REG_GS];
}

int main(int argc, char **argv) {
  int ret_val;
  p_saved_ctxt = malloc(sizeof(ucontext_t));

  install_signal_handlers();

  volatile double test_d = 3.14;
  assert(test_d == 3.14);

  ret_val = getcontext(p_saved_ctxt);
  if(ret_val) {
    perror("ERROR, getcontext failed");
    exit(1);
  }

  print_fp_regs(p_saved_ctxt->uc_mcontext.fpregs);
  p_saved_ctxt->uc_mcontext.gregs[REG_EIP] = (int)&&safe_exit;

  assert(p_saved_ctxt->uc_mcontext.fpregs);
  printf("FCW: 0x%hx\n",p_saved_ctxt->uc_mcontext.fpregs->cw);

  generate_segv(1);

 safe_exit:  
  printf("safe exit\n");

  ret_val = getcontext(p_saved_ctxt);
  if(ret_val) {
    perror("ERROR, getcontext failed");
    exit(1);
  }

  assert(p_saved_ctxt->uc_mcontext.fpregs);
  printf("FCW: 0x%hx\n",p_saved_ctxt->uc_mcontext.fpregs->cw);

  free(p_saved_ctxt);
  p_saved_ctxt = 0;
  return 0;
}