util/statetrace/tracechild.cc

/*
 * Copyright (c) 2006-2007 The Regents of The University of Michigan
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met: redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer;
 * redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution;
 * neither the name of the copyright holders nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * Authors: Gabe Black
 */

#include "tracechild.hh"
#include <sys/wait.h>
#include <sys/ptrace.h>
#include <iostream>
#include <errno.h>

using namespace std;

bool TraceChild::startTracing(const char * pathToFile, char * const argv[])
{
        instructions = 0;
        pid = fork();
        if(pid == -1)
        {
                cout << "fork failed" << endl;
                return false;
        }
        else if(pid == 0)
        {
                //We're the child. Get things ready and then exec the
                //program to trace.

                //Let our parent trace us
                if(ptrace(PTRACE_TRACEME, 0, 0, 0) == -1)
                {
                        cout << "Failure calling TRACEME\n";
                        cout << strerror(errno) << endl;
                        return false;
                }

                //Set up an empty environment for the child...
                //We would want to specify this somehow at some point
                char * env[] = {NULL};

                //Start the program to trace
                execve(pathToFile, argv, env);

                //We should never get here, so this is an error!
                cout << "Exec failed\n";
                cout <<  strerror(errno) << endl;
                return false;
        }

        //From this point forward, we know we're in the parent process.
        if(!doWait())
        {
                cout << "Didn't wait successfully" << endl;
                return false;
        }
        tracing = true;
        if(!update(pid))
        {
                cout << "Didn't update successfully!" << endl;
                return false;
        }
        return true;
}

bool TraceChild::stopTracing()
{
        if(ptrace(PTRACE_KILL, pid, 0, 0) != 0)
                return false;
        tracing = false;
        return true;
}

bool TraceChild::step()
{
        ptraceSingleStep();
}

bool TraceChild::ptraceSingleStep()
{
        if(!tracing)
        {
                cout << "Not tracing!" << endl;
                return false;
        }
        if(ptrace(PTRACE_SINGLESTEP, pid, 0, 0) != 0)
        {
                switch(errno)
                {
                        case EBUSY: cout << "EBUSY" << endl; break;
                        case EFAULT: cout << "EFAULT" << endl; break;
                        case EIO: cout << "EIO" << endl; break;
                        case EPERM: cout << "EPERM" << endl; break;
                        case ESRCH: cout << "ESRCH" << endl; break;
                        default: cout << "Unknown error" << endl; break;
                }
                cout << "Not able to single step!" << endl;
                tracing == false;
                return false;
        }
        doWait();
        update(pid);
}

bool TraceChild::doWait()
{
        int wait_val;
        wait(&wait_val);
        if(WIFEXITED(wait_val))
        {
                cerr << "Program exited! Exit status is "
                        << WEXITSTATUS(wait_val) << endl;
                cerr << "Executed " << instructions
                        << " instructions." << endl;
                tracing = false;
                return false;
        }
        if(WIFSIGNALED(wait_val))
        {
                if(WTERMSIG(wait_val))
                        cerr << "Program terminated by signal "
                                << WTERMSIG(wait_val) << endl;
                if(WCOREDUMP(wait_val))
                        cerr << "Program core dumped!" << endl;
                tracing = false;
                cerr << "Executed " << instructions
                        << " instructions." << endl;
                return false;
        }
        if(WIFSTOPPED(wait_val) && WSTOPSIG(wait_val) != SIGTRAP)
        {
                cerr << "Program stopped by signal "
                        << WSTOPSIG(wait_val) << endl;
                tracing = false;
                cerr << "Executed " << instructions
                        << " instructions." << endl;
                return false;
        }
        return true;
}