1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
|
/*
* Copyright (c) 2020, Itamar S. <itamar8910@gmail.com>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* 2. 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.
*
* 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 HOLDER 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.
*/
#pragma once
#include <AK/Demangle.h>
#include <AK/HashMap.h>
#include <AK/MappedFile.h>
#include <AK/NonnullRefPtr.h>
#include <AK/Optional.h>
#include <AK/OwnPtr.h>
#include <AK/String.h>
#include <LibC/sys/arch/i386/regs.h>
#include <LibDebug/DebugInfo.h>
#include <LibELF/Loader.h>
#include <signal.h>
#include <stdio.h>
#include <sys/ptrace.h>
#include <sys/wait.h>
#include <unistd.h>
class DebugSession {
public:
static OwnPtr<DebugSession> exec_and_attach(const String& command);
// Has to be public for OwnPtr::make
DebugSession(int pid);
~DebugSession();
int pid() const { return m_debugee_pid; }
bool poke(u32* address, u32 data);
Optional<u32> peek(u32* address) const;
enum class BreakPointState {
Enabled,
Disabled,
};
struct BreakPoint {
void* address;
u32 original_first_word;
BreakPointState state;
};
bool insert_breakpoint(void* address);
bool disable_breakpoint(void* address);
bool enable_breakpoint(void* address);
bool remove_breakpoint(void* address);
bool breakpoint_exists(void* address) const;
void dump_breakpoints()
{
for (auto addr : m_breakpoints.keys()) {
dbg() << addr;
}
}
PtraceRegisters get_registers() const;
void set_registers(const PtraceRegisters&);
enum class ContinueType {
FreeRun,
Syscall,
};
void continue_debugee(ContinueType type = ContinueType::FreeRun);
//returns the wstatus result of waitpid()
int continue_debugee_and_wait(ContinueType type = ContinueType::FreeRun);
void* single_step();
template<typename Callback>
void run(Callback callback);
const ELF::Loader& elf() const { return *m_elf; }
NonnullRefPtr<const ELF::Loader> elf_ref() const { return m_elf; }
const MappedFile& executable() const { return m_executable; }
const DebugInfo& debug_info() const { return m_debug_info; }
enum DebugDecision {
Continue,
SingleStep,
ContinueBreakAtSyscall,
Detach,
Kill,
};
enum DebugBreakReason {
Breakpoint,
Syscall,
Exited,
};
private:
// x86 breakpoint instruction "int3"
static constexpr u8 BREAKPOINT_INSTRUCTION = 0xcc;
int m_debugee_pid { -1 };
bool m_is_debugee_dead { false };
MappedFile m_executable;
NonnullRefPtr<const ELF::Loader> m_elf;
DebugInfo m_debug_info;
HashMap<void*, BreakPoint> m_breakpoints;
};
template<typename Callback>
void DebugSession::run(Callback callback)
{
enum class State {
FreeRun,
Syscall,
ConsecutiveBreakpoint,
SingleStep,
};
State state { State::FreeRun };
auto do_continue_and_wait = [&]() {
int wstatus = continue_debugee_and_wait((state == State::FreeRun) ? ContinueType::FreeRun : ContinueType::Syscall);
// FIXME: This check actually only checks whether the debugee
// stopped because it hit a breakpoint/syscall/is in single stepping mode or not
if (WSTOPSIG(wstatus) != SIGTRAP) {
callback(DebugBreakReason::Exited, Optional<PtraceRegisters>());
m_is_debugee_dead = true;
return true;
}
return false;
};
for (;;) {
if (state == State::FreeRun || state == State::Syscall) {
if (do_continue_and_wait())
break;
}
auto regs = get_registers();
Optional<BreakPoint> current_breakpoint;
if (state == State::FreeRun || state == State::Syscall) {
current_breakpoint = m_breakpoints.get((void*)((u32)regs.eip - 1));
if (current_breakpoint.has_value())
state = State::FreeRun;
} else {
current_breakpoint = m_breakpoints.get((void*)regs.eip);
}
if (current_breakpoint.has_value()) {
// We want to make the breakpoint transparrent to the user of the debugger.
// To achieive this, we perform two rollbacks:
// 1. Set regs.eip to point at the actual address of the instruction we breaked on.
// regs.eip currently points to one byte after the address of the original instruction,
// because the cpu has just executed the INT3 we patched into the instruction.
// 2. We restore the original first byte of the instruction,
// because it was patched with INT3.
regs.eip = reinterpret_cast<u32>(current_breakpoint.value().address);
set_registers(regs);
disable_breakpoint(current_breakpoint.value().address);
}
DebugBreakReason reason = (state == State::Syscall && !current_breakpoint.has_value()) ? DebugBreakReason::Syscall : DebugBreakReason::Breakpoint;
DebugDecision decision = callback(reason, regs);
if (reason == DebugBreakReason::Syscall) {
// skip the exit from the syscall
if (do_continue_and_wait())
break;
}
if (decision == DebugDecision::Continue) {
state = State::FreeRun;
} else if (decision == DebugDecision::ContinueBreakAtSyscall) {
state = State::Syscall;
}
bool did_single_step = false;
// Re-enable the breakpoint if it wasn't removed by the user
if (current_breakpoint.has_value() && m_breakpoints.contains(current_breakpoint.value().address)) {
// The current breakpoint was removed in order to make it transparrent to the user.
// We now want to re-enable it - the code execution flow could hit it again.
// To re-enable the breakpoint, we first perform a single step and execute the
// instruction of the breakpoint, and then redo the INT3 patch in its first byte.
auto stopped_address = single_step();
enable_breakpoint(current_breakpoint.value().address);
did_single_step = true;
// If there is another breakpoint after the current one,
// Then we are already on it (because of single_step)
auto breakpoint_at_next_instruction = m_breakpoints.get(stopped_address);
if (breakpoint_at_next_instruction.has_value()
&& breakpoint_at_next_instruction.value().state == BreakPointState::Enabled) {
state = State::ConsecutiveBreakpoint;
}
}
if (decision == DebugDecision::SingleStep) {
state = State::SingleStep;
}
if (decision == DebugDecision::Kill || decision == DebugDecision::Detach) {
ASSERT_NOT_REACHED(); // TODO: implement
}
if (state == State::SingleStep && !did_single_step) {
single_step();
}
}
}
|
