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 <cstring>
  33 #include <errno.h>
  34 #include <iostream>
  35 #include <sys/ptrace.h>
  36 #include <sys/wait.h>
  37
  38 using namespace std;
  39
  40 bool TraceChild::startTracing(const char * pathToFile, char * const argv[])
  41 {
  42         instructions = 0;
  43         pid = fork();
  44         if(pid == -1)
  45         {
  46                 cout << "fork failed" << endl;
  47                 return false;
  48         }
  49         else if(pid == 0)
  50         {
  51                 //We're the child. Get things ready and then exec the
  52                 //program to trace.
  53
  54                 //Let our parent trace us
  55                 if(ptrace(PTRACE_TRACEME, 0, 0, 0) == -1)
  56                 {
  57                         cout << "Failure calling TRACEME\n";
  58                         cout << strerror(errno) << endl;
  59                         return false;
  60                 }
  61
  62                 //Set up an empty environment for the child...
  63                 //We would want to specify this somehow at some point
  64                 char * env[] = {NULL};
  65
  66                 //Start the program to trace
  67                 execve(pathToFile, argv, env);
  68
  69                 //We should never get here, so this is an error!
  70                 cout << "Exec failed\n";
  71                 cout <<  strerror(errno) << endl;
  72                 return false;
  73         }
  74
  75         //From this point forward, we know we're in the parent process.
  76         if(!doWait())
  77         {
  78                 cout << "Didn't wait successfully" << endl;
  79                 return false;
  80         }
  81         tracing = true;
  82         return true;
  83 }
  84
  85 bool TraceChild::stopTracing()
  86 {
  87         if(ptrace(PTRACE_KILL, pid, 0, 0) != 0)
  88                 return false;
  89         tracing = false;
  90         return true;
  91 }
  92
  93 bool TraceChild::step()
  94 {
  95         ptraceSingleStep();
  96 }
  97
  98 bool TraceChild::ptraceSingleStep()
  99 {
 100         if(!tracing)
 101         {
 102                 cout << "Not tracing!" << endl;
 103                 return false;
 104         }
 105         if(ptrace(PTRACE_SINGLESTEP, pid, 0, 0) != 0)
 106         {
 107                 switch(errno)
 108                 {
 109                         case EBUSY: cout << "EBUSY" << endl; break;
 110                         case EFAULT: cout << "EFAULT" << endl; break;
 111                         case EIO: cout << "EIO" << endl; break;
 112                         case EPERM: cout << "EPERM" << endl; break;
 113                         case ESRCH: cout << "ESRCH" << endl; break;
 114                         default: cout << "Unknown error" << endl; break;
 115                 }
 116                 cout << "Not able to single step!" << endl;
 117                 tracing == false;
 118                 return false;
 119         }
 120         doWait();
 121         update(pid);
 122 }
 123
 124 bool TraceChild::doWait()
 125 {
 126         int wait_val;
 127         wait(&wait_val);
 128         if(WIFEXITED(wait_val))
 129         {
 130                 cerr << "Program exited! Exit status is "
 131                         << WEXITSTATUS(wait_val) << endl;
 132                 cerr << "Executed " << instructions
 133                         << " instructions." << endl;
 134                 tracing = false;
 135                 return false;
 136         }
 137         if(WIFSIGNALED(wait_val))
 138         {
 139                 if(WTERMSIG(wait_val))
 140                         cerr << "Program terminated by signal "
 141                                 << WTERMSIG(wait_val) << endl;
 142                 if(WCOREDUMP(wait_val))
 143                         cerr << "Program core dumped!" << endl;
 144                 tracing = false;
 145                 cerr << "Executed " << instructions
 146                         << " instructions." << endl;
 147                 return false;
 148         }
 149         if(WIFSTOPPED(wait_val) && WSTOPSIG(wait_val) != SIGTRAP)
 150         {
 151                 cerr << "Program stopped by signal "
 152                         << WSTOPSIG(wait_val) << endl;
 153                 tracing = false;
 154                 cerr << "Executed " << instructions
 155                         << " instructions." << endl;
 156                 return false;
 157         }
 158         return true;
 159 }