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 <sys/ptrace.h>
32#include <sys/wait.h>
33
34#include <cerrno>
35#include <cstring>
36#include <iostream>
37
38#include "tracechild.hh"
39
40using namespace std;
41
42bool
43TraceChild::startTracing(const char * pathToFile, char * const argv[])
44{
45    instructions = 0;
46    pid = fork();
47    if (pid == -1) {
48        cout << "fork failed" << endl;
49        return false;
50    } else if (pid == 0) {
51        //We're the child. Get things ready and then exec the program to trace.
52        //Let our parent trace us
53        if (ptrace(PTRACE_TRACEME, 0, 0, 0) == -1) {
54            cout << "Failure calling TRACEME\n" << strerror(errno) << endl;
55            return false;
56        }
57
58        //Set up an empty environment for the child... We would want to
59        //specify this somehow at some point
60        char * env[] = {NULL};
61
62        //Start the program to trace
63        execve(pathToFile, argv, env);
64
65        //We should never get here, so this is an error!
66        cout << "Exec failed\n" <<  strerror(errno) << endl;
67        return false;
68    }
69
70    //From this point forward, we know we're in the parent process.
71    if (!doWait()) {
72        cout << "Didn't wait successfully" << endl;
73        return false;
74    }
75    tracing = true;
76    return true;
77}
78
79bool
80TraceChild::stopTracing()
81{
82    if (ptrace(PTRACE_KILL, pid, 0, 0) != 0)
83        return false;
84    tracing = false;
85    return true;
86}
87
88bool
89TraceChild::step()
90{
91    ptraceSingleStep();
92}
93
94bool
95TraceChild::ptraceSingleStep()
96{
97    if (!tracing) {
98        cout << "Not tracing!" << endl;
99        return false;
100    }
101    if (ptrace(PTRACE_SINGLESTEP, pid, 0, 0) != 0) {
102        switch (errno) {
103          case EBUSY: cout << "EBUSY" << endl; break;
104          case EFAULT: cout << "EFAULT" << endl; break;
105          case EIO: cout << "EIO" << endl; break;
106          case EPERM: cout << "EPERM" << endl; break;
107          case ESRCH: cout << "ESRCH" << endl; break;
108          default: cout << "Unknown error" << endl; break;
109        }
110        cout << "Not able to single step!" << endl;
111        tracing = false;
112        return false;
113    }
114    doWait();
115    update(pid);
116}
117
118bool
119TraceChild::doWait()
120{
121    int wait_val;
122    wait(&wait_val);
123    if (WIFEXITED(wait_val)) {
124        cerr << "Program exited! Exit status is "
125             << WEXITSTATUS(wait_val) << endl;
126        cerr << "Executed " << instructions
127             << " instructions." << endl;
128        tracing = false;
129        return false;
130    }
131    if (WIFSIGNALED(wait_val)) {
132        if (WTERMSIG(wait_val))
133            cerr << "Program terminated by signal "
134                 << WTERMSIG(wait_val) << endl;
135        if (WCOREDUMP(wait_val))
136            cerr << "Program core dumped!" << endl;
137        tracing = false;
138        cerr << "Executed " << instructions
139             << " instructions." << endl;
140        return false;
141    }
142    if (WIFSTOPPED(wait_val) && WSTOPSIG(wait_val) != SIGTRAP) {
143        cerr << "Program stopped by signal " << WSTOPSIG(wait_val) << endl;
144        tracing = false;
145        cerr << "Executed " << instructions << " instructions." << endl;
146            return false;
147    }
148    return true;
149}
150