text: /*
   * Copyright (c) 2006-2007 The Regents of The University of Michigan
   * 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 copyright holders 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 COPYRIGHT
   * OWNER OR 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.
   *
   * Authors: Gabe Black
   */
  
  #include <sys/ptrace.h>
  #include <sys/wait.h>
  
  #include <cerrno>
  #include <cstring>
  #include <iostream>
  
  #include "tracechild.hh"
  
  using namespace std;
  
  bool
  TraceChild::startTracing(const char * pathToFile, char * const argv[])
  {
      instructions = 0;
      pid = fork();
      if (pid == -1) {
          cout << "fork failed" << endl;
          return false;
      } else if (pid == 0) {
          //We're the child. Get things ready and then exec the program to trace.
          //Let our parent trace us
          if (ptrace(PTRACE_TRACEME, 0, 0, 0) == -1) {
              cout << "Failure calling TRACEME\n" << strerror(errno) << endl;
              return false;
          }
  
          //Set up an empty environment for the child... We would want to
          //specify this somehow at some point
          char * env[] = {NULL};
  
          //Start the program to trace
          execve(pathToFile, argv, env);
  
          //We should never get here, so this is an error!
          cout << "Exec failed\n" <<  strerror(errno) << endl;
          return false;
      }
  
      //From this point forward, we know we're in the parent process.
      if (!doWait()) {
          cout << "Didn't wait successfully" << endl;
          return false;
      }
      tracing = true;
      return true;
  }
  
  bool
  TraceChild::stopTracing()
  {
      if (ptrace(PTRACE_KILL, pid, 0, 0) != 0)
          return false;
      tracing = false;
      return true;
  }
  
  bool
  TraceChild::step()
  {
      ptraceSingleStep();
  }
  
  bool
  TraceChild::ptraceSingleStep()
  {
      if (!tracing) {
          cout << "Not tracing!" << endl;
          return false;
      }
      if (ptrace(PTRACE_SINGLESTEP, pid, 0, 0) != 0) {
          switch (errno) {
            case EBUSY: cout << "EBUSY" << endl; break;
            case EFAULT: cout << "EFAULT" << endl; break;
            case EIO: cout << "EIO" << endl; break;
            case EPERM: cout << "EPERM" << endl; break;
            case ESRCH: cout << "ESRCH" << endl; break;
            default: cout << "Unknown error" << endl; break;
          }
          cout << "Not able to single step!" << endl;
          tracing == false;
          return false;
      }
      doWait();
      update(pid);
  }
  
  bool
  TraceChild::doWait()
  {
      int wait_val;
      wait(&wait_val);
      if (WIFEXITED(wait_val)) {
          cerr << "Program exited! Exit status is "
               << WEXITSTATUS(wait_val) << endl;
          cerr << "Executed " << instructions
               << " instructions." << endl;
          tracing = false;
          return false;
      }
      if (WIFSIGNALED(wait_val)) {
          if (WTERMSIG(wait_val))
              cerr << "Program terminated by signal "
                   << WTERMSIG(wait_val) << endl;
          if (WCOREDUMP(wait_val))
              cerr << "Program core dumped!" << endl;
          tracing = false;
          cerr << "Executed " << instructions
               << " instructions." << endl;
          return false;
      }
      if (WIFSTOPPED(wait_val) && WSTOPSIG(wait_val) != SIGTRAP) {
          cerr << "Program stopped by signal " << WSTOPSIG(wait_val) << endl;
          tracing = false;
          cerr << "Executed " << instructions << " instructions." << endl;
              return false;
      }
      return true;
  }
  