tracechild.cc revision 3115 
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
37using namespace std;
38
39bool 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
77bool TraceChild::stopTracing()
78{
79        if(ptrace(PTRACE_KILL, pid, 0, 0) != 0)
80                return false;
81        tracing = false;
82        return true;
83}
84
85bool TraceChild::step()
86{
87        ptraceSingleStep();
88}
89
90bool 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
116bool 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}
146