tracechild.cc revision 6406 
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 TraceChild::startTracing(const char * pathToFile, char * const argv[])
41{
42        instructions = 0;
43        pid = fork();
44        if(pid == -1)
45        {
46                cout << "fork failed" << endl;
47                return false;
48        }
49        else if(pid == 0)
50        {
51                //We're the child. Get things ready and then exec the
52                //program to trace.
53
54                //Let our parent trace us
55                if(ptrace(PTRACE_TRACEME, 0, 0, 0) == -1)
56                {
57                        cout << "Failure calling TRACEME\n";
58                        cout << strerror(errno) << endl;
59                        return false;
60                }
61
62                //Set up an empty environment for the child...
63                //We would want to specify this somehow at some point
64                char * env[] = {NULL};
65
66                //Start the program to trace
67                execve(pathToFile, argv, env);
68
69                //We should never get here, so this is an error!
70                cout << "Exec failed\n";
71                cout <<  strerror(errno) << endl;
72                return false;
73        }
74
75        //From this point forward, we know we're in the parent process.
76        if(!doWait())
77        {
78                cout << "Didn't wait successfully" << endl;
79                return false;
80        }
81        tracing = true;
82        if(!update(pid))
83        {
84                cout << "Didn't update successfully!" << endl;
85                return false;
86        }
87        return true;
88}
89
90bool TraceChild::stopTracing()
91{
92        if(ptrace(PTRACE_KILL, pid, 0, 0) != 0)
93                return false;
94        tracing = false;
95        return true;
96}
97
98bool TraceChild::step()
99{
100        ptraceSingleStep();
101}
102
103bool TraceChild::ptraceSingleStep()
104{
105        if(!tracing)
106        {
107                cout << "Not tracing!" << endl;
108                return false;
109        }
110        if(ptrace(PTRACE_SINGLESTEP, pid, 0, 0) != 0)
111        {
112                switch(errno)
113                {
114                        case EBUSY: cout << "EBUSY" << endl; break;
115                        case EFAULT: cout << "EFAULT" << endl; break;
116                        case EIO: cout << "EIO" << endl; break;
117                        case EPERM: cout << "EPERM" << endl; break;
118                        case ESRCH: cout << "ESRCH" << endl; break;
119                        default: cout << "Unknown error" << endl; break;
120                }
121                cout << "Not able to single step!" << endl;
122                tracing == false;
123                return false;
124        }
125        doWait();
126        update(pid);
127}
128
129bool TraceChild::doWait()
130{
131        int wait_val;
132        wait(&wait_val);
133        if(WIFEXITED(wait_val))
134        {
135                cerr << "Program exited! Exit status is "
136                        << WEXITSTATUS(wait_val) << endl;
137                cerr << "Executed " << instructions
138                        << " instructions." << endl;
139                tracing = false;
140                return false;
141        }
142        if(WIFSIGNALED(wait_val))
143        {
144                if(WTERMSIG(wait_val))
145                        cerr << "Program terminated by signal "
146                                << WTERMSIG(wait_val) << endl;
147                if(WCOREDUMP(wait_val))
148                        cerr << "Program core dumped!" << endl;
149                tracing = false;
150                cerr << "Executed " << instructions
151                        << " instructions." << endl;
152                return false;
153        }
154        if(WIFSTOPPED(wait_val) && WSTOPSIG(wait_val) != SIGTRAP)
155        {
156                cerr << "Program stopped by signal "
157                        << WSTOPSIG(wait_val) << endl;
158                tracing = false;
159                cerr << "Executed " << instructions
160                        << " instructions." << endl;
161                return false;
162        }
163        return true;
164}
165