util/statetrace/tracechild.cc

   1 /*
   2  * Copyright (c) 2006-2007 The Regents of The University of Michigan
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions are
   7  * met: redistributions of source code must retain the above copyright
   8  * notice, this list of conditions and the following disclaimer;
   9  * redistributions in binary form must reproduce the above copyright
  10  * notice, this list of conditions and the following disclaimer in the
  11  * documentation and/or other materials provided with the distribution;
  12  * neither the name of the copyright holders nor the names of its
  13  * contributors may be used to endorse or promote products derived from
  14  * this software without specific prior written permission.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  17  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  18  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  19  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  20  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  21  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  22  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  26  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27  *
  28  * Authors: Gabe Black
  29  */
  30
  31 #include "tracechild.hh"
  32 #include <sys/wait.h>
  33 #include <sys/ptrace.h>
  34 #include <iostream>
  35 #include <errno.h>
  36
  37 using namespace std;
  38
  39 bool TraceChild::startTracing(const char * pathToFile, char * const argv[])
  40 {
  41         instructions = 0;
  42         pid = fork();
  43         if(pid == -1)
  44         {
  45                 cout << "fork failed" << endl;
  46                 return false;
  47         }
  48         else if(pid == 0)
  49         {
  50                 //We're the child. Get things ready and then exec the
  51                 //program to trace.
  52
  53                 //Let our parent trace us
  54                 if(ptrace(PTRACE_TRACEME, 0, 0, 0) == -1)
  55                 {
  56                         cout << "Failure calling TRACEME\n";
  57                         cout << strerror(errno) << endl;
  58                         return false;
  59                 }
  60
  61                 //Set up an empty environment for the child...
  62                 //We would want to specify this somehow at some point
  63                 char * env[] = {NULL};
  64
  65                 //Start the program to trace
  66                 execve(pathToFile, argv, env);
  67
  68                 //We should never get here, so this is an error!
  69                 cout << "Exec failed\n";
  70                 cout <<  strerror(errno) << endl;
  71                 return false;
  72         }
  73
  74         //From this point forward, we know we're in the parent process.
  75         if(!doWait())
  76         {
  77                 cout << "Didn't wait successfully" << endl;
  78                 return false;
  79         }
  80         tracing = true;
  81         if(!update(pid))
  82         {
  83                 cout << "Didn't update successfully!" << endl;
  84                 return false;
  85         }
  86         return true;
  87 }
  88
  89 bool TraceChild::stopTracing()
  90 {
  91         if(ptrace(PTRACE_KILL, pid, 0, 0) != 0)
  92                 return false;
  93         tracing = false;
  94         return true;
  95 }
  96
  97 bool TraceChild::step()
  98 {
  99         ptraceSingleStep();
 100 }
 101
 102 bool TraceChild::ptraceSingleStep()
 103 {
 104         if(!tracing)
 105         {
 106                 cout << "Not tracing!" << endl;
 107                 return false;
 108         }
 109         if(ptrace(PTRACE_SINGLESTEP, pid, 0, 0) != 0)
 110         {
 111                 switch(errno)
 112                 {
 113                         case EBUSY: cout << "EBUSY" << endl; break;
 114                         case EFAULT: cout << "EFAULT" << endl; break;
 115                         case EIO: cout << "EIO" << endl; break;
 116                         case EPERM: cout << "EPERM" << endl; break;
 117                         case ESRCH: cout << "ESRCH" << endl; break;
 118                         default: cout << "Unknown error" << endl; break;
 119                 }
 120                 cout << "Not able to single step!" << endl;
 121                 tracing == false;
 122                 return false;
 123         }
 124         doWait();
 125         update(pid);
 126 }
 127
 128 bool TraceChild::doWait()
 129 {
 130         int wait_val;
 131         wait(&wait_val);
 132         if(WIFEXITED(wait_val))
 133         {
 134                 cerr << "Program exited! Exit status is "
 135                         << WEXITSTATUS(wait_val) << endl;
 136                 cerr << "Executed " << instructions
 137                         << " instructions." << endl;
 138                 tracing = false;
 139                 return false;
 140         }
 141         if(WIFSIGNALED(wait_val))
 142         {
 143                 if(WTERMSIG(wait_val))
 144                         cerr << "Program terminated by signal "
 145                                 << WTERMSIG(wait_val) << endl;
 146                 if(WCOREDUMP(wait_val))
 147                         cerr << "Program core dumped!" << endl;
 148                 tracing = false;
 149                 cerr << "Executed " << instructions
 150                         << " instructions." << endl;
 151                 return false;
 152         }
 153         if(WIFSTOPPED(wait_val) && WSTOPSIG(wait_val) != SIGTRAP)
 154         {
 155                 cerr << "Program stopped by signal "
 156                         << WSTOPSIG(wait_val) << endl;
 157                 tracing = false;
 158                 cerr << "Executed " << instructions
 159                         << " instructions." << endl;
 160                 return false;
 161         }
 162         return true;
 163 }