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                 ptrace(PTRACE_TRACEME, 0, 0, 0);
  55
  56                 //Start the program to trace
  57                 execv(pathToFile, argv);
  58
  59                 //We should never get here, so this is an error!
  60                 return false;
  61         }
  62
  63         //From this point forward, we know we're in the parent process.
  64         if(!doWait())
  65         {
  66                 cout << "Didn't wait successfully" << endl;
  67                 return false;
  68         }
  69         tracing = true;
  70         if(!update(pid))
  71         {
  72                 cout << "Didn't update successfully!" << endl;
  73                 return false;
  74         }
  75         return true;
  76 }
  77
  78 bool TraceChild::stopTracing()
  79 {
  80         if(ptrace(PTRACE_KILL, pid, 0, 0) != 0)
  81                 return false;
  82         tracing = false;
  83         return true;
  84 }
  85
  86 bool TraceChild::step()
  87 {
  88         ptraceSingleStep();
  89 }
  90
  91 bool TraceChild::ptraceSingleStep()
  92 {
  93         if(!tracing)
  94         {
  95                 cout << "Not tracing!" << endl;
  96                 return false;
  97         }
  98         if(ptrace(PTRACE_SINGLESTEP, pid, 0, 0) != 0)
  99         {
 100                 switch(errno)
 101                 {
 102                         case EBUSY: cout << "EBUSY" << endl; break;
 103                         case EFAULT: cout << "EFAULT" << endl; break;
 104                         case EIO: cout << "EIO" << endl; break;
 105                         case EPERM: cout << "EPERM" << endl; break;
 106                         case ESRCH: cout << "ESRCH" << endl; break;
 107                         default: cout << "Unknown error" << endl; break;
 108                 }
 109                 cout << "Not able to single step!" << endl;
 110                 tracing == false;
 111                 return false;
 112         }
 113         doWait();
 114         update(pid);
 115 }
 116
 117 bool TraceChild::doWait()
 118 {
 119         int wait_val;
 120         wait(&wait_val);
 121         if(WIFEXITED(wait_val))
 122         {
 123                 cerr << "Program exited! Exit status is "
 124                         << WEXITSTATUS(wait_val) << endl;
 125                 cerr << "Executed " << instructions
 126                         << " instructions." << endl;
 127                 tracing = false;
 128                 return false;
 129         }
 130         if(WIFSIGNALED(wait_val))
 131         {
 132                 if(WTERMSIG(wait_val))
 133                         cerr << "Program terminated by signal "
 134                                 << WTERMSIG(wait_val) << endl;
 135                 if(WCOREDUMP(wait_val))
 136                         cerr << "Program core dumped!" << endl;
 137                 tracing = false;
 138                 cerr << "Executed " << instructions
 139                         << " instructions." << endl;
 140                 return false;
 141         }
 142         if(WIFSTOPPED(wait_val) && WSTOPSIG(wait_val) != SIGTRAP)
 143         {
 144                 cerr << "Program stopped by signal "
 145                         << WSTOPSIG(wait_val) << endl;
 146                 tracing = false;
 147                 cerr << "Executed " << instructions
 148                         << " instructions." << endl;
 149                 return false;
 150         }
 151         return true;
 152 }