jcs.org
Serenity Operating System
1/*
2 * Copyright (c) 2020, Itamar S. <itamar8910@gmail.com>
3 *
4 * SPDX-License-Identifier: BSD-2-Clause
5 */
6
7#pragma once
8
9#include <AK/Demangle.h>
10#include <AK/DeprecatedString.h>
11#include <AK/Function.h>
12#include <AK/HashMap.h>
13#include <AK/NonnullRefPtr.h>
14#include <AK/Optional.h>
15#include <AK/OwnPtr.h>
16#include <LibCore/MappedFile.h>
17#include <LibDebug/DebugInfo.h>
18#include <LibDebug/ProcessInspector.h>
19#include <signal.h>
20#include <stdio.h>
21#include <sys/arch/regs.h>
22#include <sys/ptrace.h>
23#include <sys/wait.h>
24#include <unistd.h>
25
26namespace Debug {
27
28class DebugSession : public ProcessInspector {
29public:
30 static OwnPtr<DebugSession> exec_and_attach(DeprecatedString const& command, DeprecatedString source_root = {}, Function<ErrorOr<void>()> setup_child = {}, Function<void(float)> on_initialization_progress = {});
31 static OwnPtr<DebugSession> attach(pid_t pid, DeprecatedString source_root = {}, Function<void(float)> on_initialization_progress = {});
32
33 virtual ~DebugSession() override;
34
35 // ^Debug::ProcessInspector
36 virtual bool poke(FlatPtr address, FlatPtr data) override;
37 virtual Optional<FlatPtr> peek(FlatPtr address) const override;
38 virtual PtraceRegisters get_registers() const override;
39 virtual void set_registers(PtraceRegisters const&) override;
40 virtual void for_each_loaded_library(Function<IterationDecision(LoadedLibrary const&)>) const override;
41
42 int pid() const { return m_debuggee_pid; }
43
44 bool poke_debug(u32 register_index, FlatPtr data) const;
45 Optional<FlatPtr> peek_debug(u32 register_index) const;
46
47 enum class BreakPointState {
48 Enabled,
49 Disabled,
50 };
51
52 struct BreakPoint {
53 FlatPtr address { 0 };
54 FlatPtr original_first_word { 0 };
55 BreakPointState state { BreakPointState::Disabled };
56 };
57
58 struct InsertBreakpointAtSymbolResult {
59 DeprecatedString library_name;
60 FlatPtr address { 0 };
61 };
62
63 Optional<InsertBreakpointAtSymbolResult> insert_breakpoint(DeprecatedString const& symbol_name);
64
65 struct InsertBreakpointAtSourcePositionResult {
66 DeprecatedString library_name;
67 DeprecatedString filename;
68 size_t line_number { 0 };
69 FlatPtr address { 0 };
70 };
71
72 Optional<InsertBreakpointAtSourcePositionResult> insert_breakpoint(DeprecatedString const& filename, size_t line_number);
73
74 bool insert_breakpoint(FlatPtr address);
75 bool disable_breakpoint(FlatPtr address);
76 bool enable_breakpoint(FlatPtr address);
77 bool remove_breakpoint(FlatPtr address);
78 bool breakpoint_exists(FlatPtr address) const;
79
80 struct WatchPoint {
81 FlatPtr address { 0 };
82 u32 debug_register_index { 0 };
83 u32 ebp { 0 };
84 };
85
86 bool insert_watchpoint(FlatPtr address, u32 ebp);
87 bool remove_watchpoint(FlatPtr address);
88 bool disable_watchpoint(FlatPtr address);
89 bool watchpoint_exists(FlatPtr address) const;
90
91 void dump_breakpoints()
92 {
93 for (auto addr : m_breakpoints.keys()) {
94 dbgln("{}", addr);
95 }
96 }
97
98 enum class ContinueType {
99 FreeRun,
100 Syscall,
101 };
102 void continue_debuggee(ContinueType type = ContinueType::FreeRun);
103 void stop_debuggee();
104
105 // Returns the wstatus result of waitpid()
106 int continue_debuggee_and_wait(ContinueType type = ContinueType::FreeRun);
107
108 // Returns the new eip
109 FlatPtr single_step();
110
111 void detach();
112
113 enum DesiredInitialDebugeeState {
114 Running,
115 Stopped
116 };
117 template<typename Callback>
118 void run(DesiredInitialDebugeeState, Callback);
119
120 enum DebugDecision {
121 Continue,
122 SingleStep,
123 ContinueBreakAtSyscall,
124 Detach,
125 Kill,
126 };
127
128 enum DebugBreakReason {
129 Breakpoint,
130 Syscall,
131 Exited,
132 };
133
134private:
135 explicit DebugSession(pid_t, DeprecatedString source_root, Function<void(float)> on_initialization_progress = {});
136
137 // x86 breakpoint instruction "int3"
138 static constexpr u8 BREAKPOINT_INSTRUCTION = 0xcc;
139
140 void update_loaded_libs();
141
142 int m_debuggee_pid { -1 };
143 DeprecatedString m_source_root;
144 bool m_is_debuggee_dead { false };
145
146 HashMap<FlatPtr, BreakPoint> m_breakpoints;
147 HashMap<FlatPtr, WatchPoint> m_watchpoints;
148
149 // Maps from library name to LoadedLibrary object
150 HashMap<DeprecatedString, NonnullOwnPtr<LoadedLibrary>> m_loaded_libraries;
151
152 Function<void(float)> m_on_initialization_progress;
153};
154
155template<typename Callback>
156void DebugSession::run(DesiredInitialDebugeeState initial_debugee_state, Callback callback)
157{
158 enum class State {
159 FirstIteration,
160 FreeRun,
161 Syscall,
162 ConsecutiveBreakpoint,
163 SingleStep,
164 };
165
166 State state { State::FirstIteration };
167
168 auto do_continue_and_wait = [&]() {
169 int wstatus = continue_debuggee_and_wait((state == State::Syscall) ? ContinueType::Syscall : ContinueType::FreeRun);
170
171 // FIXME: This check actually only checks whether the debuggee
172 // stopped because it hit a breakpoint/syscall/is in single stepping mode or not
173 if (WSTOPSIG(wstatus) != SIGTRAP && WSTOPSIG(wstatus) != SIGSTOP) {
174 callback(DebugBreakReason::Exited, Optional<PtraceRegisters>());
175 m_is_debuggee_dead = true;
176 return true;
177 }
178 return false;
179 };
180
181 for (;;) {
182 if ((state == State::FirstIteration && initial_debugee_state == DesiredInitialDebugeeState::Running) || state == State::FreeRun || state == State::Syscall) {
183 if (do_continue_and_wait())
184 break;
185 }
186 if (state == State::FirstIteration)
187 state = State::FreeRun;
188
189 auto regs = get_registers();
190
191#if ARCH(X86_64)
192 FlatPtr current_instruction = regs.rip;
193#elif ARCH(AARCH64)
194 FlatPtr current_instruction;
195 TODO_AARCH64();
196#else
197# error Unknown architecture
198#endif
199
200 auto debug_status = peek_debug(DEBUG_STATUS_REGISTER);
201 if (debug_status.has_value() && (debug_status.value() & 0b1111) > 0) {
202 // Tripped a watchpoint
203 auto watchpoint_index = debug_status.value() & 0b1111;
204 Optional<WatchPoint> watchpoint {};
205 for (auto wp : m_watchpoints) {
206 if ((watchpoint_index & (1 << wp.value.debug_register_index)) == 0)
207 continue;
208 watchpoint = wp.value;
209 break;
210 }
211 if (watchpoint.has_value()) {
212 auto required_ebp = watchpoint.value().ebp;
213 auto found_ebp = false;
214
215#if ARCH(X86_64)
216 FlatPtr current_ebp = regs.rbp;
217#elif ARCH(AARCH64)
218 FlatPtr current_ebp;
219 TODO_AARCH64();
220#else
221# error Unknown architecture
222#endif
223
224 do {
225 if (current_ebp == required_ebp) {
226 found_ebp = true;
227 break;
228 }
229 auto return_address = peek(current_ebp + sizeof(FlatPtr));
230 auto next_ebp = peek(current_ebp);
231 VERIFY(return_address.has_value());
232 VERIFY(next_ebp.has_value());
233 current_instruction = return_address.value();
234 current_ebp = next_ebp.value();
235 } while (current_ebp && current_instruction);
236
237 if (!found_ebp) {
238 dbgln("Removing watchpoint at {:p} because it went out of scope!", watchpoint.value().address);
239 remove_watchpoint(watchpoint.value().address);
240 continue;
241 }
242 }
243 }
244
245 Optional<BreakPoint> current_breakpoint;
246
247 if (state == State::FreeRun || state == State::Syscall) {
248 current_breakpoint = m_breakpoints.get(current_instruction - 1);
249 if (current_breakpoint.has_value())
250 state = State::FreeRun;
251 } else {
252 current_breakpoint = m_breakpoints.get(current_instruction);
253 }
254
255 if (current_breakpoint.has_value()) {
256 // We want to make the breakpoint transparent to the user of the debugger.
257 // To achieve this, we perform two rollbacks:
258 // 1. Set regs.eip to point at the actual address of the instruction we broke on.
259 // regs.eip currently points to one byte after the address of the original instruction,
260 // because the cpu has just executed the INT3 we patched into the instruction.
261 // 2. We restore the original first byte of the instruction,
262 // because it was patched with INT3.
263 auto breakpoint_addr = bit_cast<FlatPtr>(current_breakpoint.value().address);
264#if ARCH(X86_64)
265 regs.rip = breakpoint_addr;
266#elif ARCH(AARCH64)
267 (void)breakpoint_addr;
268 TODO_AARCH64();
269#else
270# error Unknown architecture
271#endif
272 set_registers(regs);
273 disable_breakpoint(current_breakpoint.value().address);
274 }
275
276 DebugBreakReason reason = (state == State::Syscall && !current_breakpoint.has_value()) ? DebugBreakReason::Syscall : DebugBreakReason::Breakpoint;
277
278 DebugDecision decision = callback(reason, regs);
279
280 if (reason == DebugBreakReason::Syscall) {
281 // skip the exit from the syscall
282 if (do_continue_and_wait())
283 break;
284 }
285
286 if (decision == DebugDecision::Continue) {
287 state = State::FreeRun;
288 } else if (decision == DebugDecision::ContinueBreakAtSyscall) {
289 state = State::Syscall;
290 }
291
292 bool did_single_step = false;
293
294 // Re-enable the breakpoint if it wasn't removed by the user
295 if (current_breakpoint.has_value()) {
296 auto current_breakpoint_address = bit_cast<FlatPtr>(current_breakpoint.value().address);
297 if (m_breakpoints.contains(current_breakpoint_address)) {
298 // The current breakpoint was removed to make it transparent to the user.
299 // We now want to re-enable it - the code execution flow could hit it again.
300 // To re-enable the breakpoint, we first perform a single step and execute the
301 // instruction of the breakpoint, and then redo the INT3 patch in its first byte.
302
303 // If the user manually inserted a breakpoint at the current instruction,
304 // we need to disable that breakpoint because we want to singlestep over that
305 // instruction (we re-enable it again later anyways).
306 if (m_breakpoints.contains(current_breakpoint_address) && m_breakpoints.get(current_breakpoint_address).value().state == BreakPointState::Enabled) {
307 disable_breakpoint(current_breakpoint.value().address);
308 }
309 auto stopped_address = single_step();
310 enable_breakpoint(current_breakpoint.value().address);
311 did_single_step = true;
312 // If there is another breakpoint after the current one,
313 // Then we are already on it (because of single_step)
314 auto breakpoint_at_next_instruction = m_breakpoints.get(stopped_address);
315 if (breakpoint_at_next_instruction.has_value()
316 && breakpoint_at_next_instruction.value().state == BreakPointState::Enabled) {
317 state = State::ConsecutiveBreakpoint;
318 }
319 }
320 }
321
322 if (decision == DebugDecision::SingleStep) {
323 state = State::SingleStep;
324 }
325
326 if (decision == DebugDecision::Detach) {
327 detach();
328 break;
329 }
330 if (decision == DebugDecision::Kill) {
331 kill(m_debuggee_pid, SIGTERM);
332 break;
333 }
334
335 if (state == State::SingleStep && !did_single_step) {
336 single_step();
337 }
338 }
339}
340
341}