util/statetrace/tracechild.cc

   1 /*
   2  * Copyright (c) 2006 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, const char * arg)
  40 {
  41         pid = fork();
  42         if(pid == -1)
  43         {
  44                 cout << "fork failed" << endl;
  45                 return false;
  46         }
  47         else if(pid == 0)
  48         {
  49                 //We're the child. Get things ready and then exec the
  50                 //program to trace.
  51
  52                 //Let our parent trace us
  53                 ptrace(PTRACE_TRACEME, 0, 0, 0);
  54
  55                 //Start the program to trace
  56                 execl(pathToFile, arg);
  57
  58                 //We should never get here, so this is an error!
  59                 return false;
  60         }
  61
  62         //From this point forward, we know we're in the parent process.
  63         if(!doWait())
  64         {
  65                 cout << "Didn't wait successfully" << endl;
  66                 return false;
  67         }
  68         tracing = true;
  69         if(!update(pid))
  70         {
  71                 cout << "Didn't update successfully!" << endl;
  72                 return false;
  73         }
  74         return true;
  75 }
  76
  77 bool TraceChild::stopTracing()
  78 {
  79         if(ptrace(PTRACE_KILL, pid, 0, 0) != 0)
  80                 return false;
  81         tracing = false;
  82         return true;
  83 }
  84
  85 bool TraceChild::step()
  86 {
  87         ptraceSingleStep();
  88 }
  89
  90 bool TraceChild::ptraceSingleStep()
  91 {
  92         if(!tracing)
  93         {
  94                 cout << "Not tracing!" << endl;
  95                 return false;
  96         }
  97         if(ptrace(PTRACE_SINGLESTEP, pid, 0, 0) != 0)
  98         {
  99                 switch(errno)
 100                 {
 101                         case EBUSY: cout << "EBUSY" << endl; break;
 102                         case EFAULT: cout << "EFAULT" << endl; break;
 103                         case EIO: cout << "EIO" << endl; break;
 104                         case EPERM: cout << "EPERM" << endl; break;
 105                         case ESRCH: cout << "ESRCH" << endl; break;
 106                         default: cout << "Unknown error" << endl; break;
 107                 }
 108                 cout << "Not able to single step!" << endl;
 109                 tracing == false;
 110                 return false;
 111         }
 112         doWait();
 113         update(pid);
 114 }
 115
 116 bool TraceChild::doWait()
 117 {
 118         int wait_val;
 119         wait(&wait_val);
 120         if(WIFEXITED(wait_val))
 121         {
 122                 cerr << "Program exited! Exit status is "
 123                         << WEXITSTATUS(wait_val) << endl;
 124                 tracing = false;
 125                 return false;
 126         }
 127         if(WIFSIGNALED(wait_val))
 128         {
 129                 if(WTERMSIG(wait_val))
 130                         cerr << "Program terminated by signal "
 131                                 << WTERMSIG(wait_val) << endl;
 132                 if(WCOREDUMP(wait_val))
 133                         cerr << "Program core dumped!" << endl;
 134                 tracing = false;
 135                 return false;
 136         }
 137         if(WIFSTOPPED(wait_val) && WSTOPSIG(wait_val) != SIGTRAP)
 138         {
 139                 cerr << "Program stopped by signal "
 140                         << WSTOPSIG(wait_val) << endl;
 141                 tracing = false;
 142                 return false;
 143         }
 144         return true;
 145 }