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