tracechild.cc revision 8108 
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
38using namespace std;
39
40bool
41TraceChild::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
77bool
78TraceChild::stopTracing()
79{
80    if (ptrace(PTRACE_KILL, pid, 0, 0) != 0)
81        return false;
82    tracing = false;
83    return true;
84}
85
86bool
87TraceChild::step()
88{
89    ptraceSingleStep();
90}
91
92bool
93TraceChild::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
116bool
117TraceChild::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}
148