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
  41 TraceChild::startTracing(const char * pathToFile, char * const argv[])
  42 {
  43     instructions = 0;
  44     pid = fork();
  45     if (pid == -1) {
  46         cout << "fork failed" << endl;
  47         return false;
  48     } else if (pid == 0) {
  49         //We're the child. Get things ready and then exec the program to trace.
  50         //Let our parent trace us
  51         if (ptrace(PTRACE_TRACEME, 0, 0, 0) == -1) {
  52             cout << "Failure calling TRACEME\n" << strerror(errno) << endl;
  53             return false;
  54         }
  55
  56         //Set up an empty environment for the child... We would want to
  57         //specify this somehow at some point
  58         char * env[] = {NULL};
  59
  60         //Start the program to trace
  61         execve(pathToFile, argv, env);
  62
  63         //We should never get here, so this is an error!
  64         cout << "Exec failed\n" <<  strerror(errno) << endl;
  65         return false;
  66     }
  67
  68     //From this point forward, we know we're in the parent process.
  69     if (!doWait()) {
  70         cout << "Didn't wait successfully" << endl;
  71         return false;
  72     }
  73     tracing = true;
  74     return true;
  75 }
  76
  77 bool
  78 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
  87 TraceChild::step()
  88 {
  89     ptraceSingleStep();
  90 }
  91
  92 bool
  93 TraceChild::ptraceSingleStep()
  94 {
  95     if (!tracing) {
  96         cout << "Not tracing!" << endl;
  97         return false;
  98     }
  99     if (ptrace(PTRACE_SINGLESTEP, pid, 0, 0) != 0) {
 100         switch (errno) {
 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
 117 TraceChild::doWait()
 118 {
 119     int wait_val;
 120     wait(&wait_val);
 121     if (WIFEXITED(wait_val)) {
 122         cerr << "Program exited! Exit status is "
 123              << WEXITSTATUS(wait_val) << endl;
 124         cerr << "Executed " << instructions
 125              << " instructions." << endl;
 126         tracing = false;
 127         return false;
 128     }
 129     if (WIFSIGNALED(wait_val)) {
 130         if (WTERMSIG(wait_val))
 131             cerr << "Program terminated by signal "
 132                  << WTERMSIG(wait_val) << endl;
 133         if (WCOREDUMP(wait_val))
 134             cerr << "Program core dumped!" << endl;
 135         tracing = false;
 136         cerr << "Executed " << instructions
 137              << " instructions." << endl;
 138         return false;
 139     }
 140     if (WIFSTOPPED(wait_val) && WSTOPSIG(wait_val) != SIGTRAP) {
 141         cerr << "Program stopped by signal " << WSTOPSIG(wait_val) << endl;
 142         tracing = false;
 143         cerr << "Executed " << instructions << " instructions." << endl;
 144             return false;
 145     }
 146     return true;
 147 }