1 //===-- UnwindLLDB.cpp -------------------------------------*- C++ -*-===//
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //===----------------------------------------------------------------------===//
9 #include "lldb/Core/Module.h"
10 #include "lldb/Symbol/FuncUnwinders.h"
11 #include "lldb/Symbol/Function.h"
12 #include "lldb/Symbol/UnwindPlan.h"
13 #include "lldb/Target/ABI.h"
14 #include "lldb/Target/Process.h"
15 #include "lldb/Target/RegisterContext.h"
16 #include "lldb/Target/Target.h"
17 #include "lldb/Target/Thread.h"
18 #include "lldb/Utility/Log.h"
20 #include "RegisterContextLLDB.h"
21 #include "UnwindLLDB.h"
24 using namespace lldb_private;
26 UnwindLLDB::UnwindLLDB(Thread &thread)
27 : Unwind(thread), m_frames(), m_unwind_complete(false),
28 m_user_supplied_trap_handler_functions() {
29 ProcessSP process_sp(thread.GetProcess());
32 process_sp->GetTarget().GetUserSpecifiedTrapHandlerNames(args);
33 size_t count = args.GetArgumentCount();
34 for (size_t i = 0; i < count; i++) {
35 const char *func_name = args.GetArgumentAtIndex(i);
36 m_user_supplied_trap_handler_functions.push_back(ConstString(func_name));
41 uint32_t UnwindLLDB::DoGetFrameCount() {
42 if (!m_unwind_complete) {
43 //#define DEBUG_FRAME_SPEED 1
45 #define FRAME_COUNT 10000
46 using namespace std::chrono;
47 auto time_value = steady_clock::now();
52 ProcessSP process_sp(m_thread.GetProcess());
53 ABI *abi = process_sp ? process_sp->GetABI().get() : nullptr;
55 while (AddOneMoreFrame(abi)) {
57 if ((m_frames.size() % FRAME_COUNT) == 0) {
58 const auto now = steady_clock::now();
59 const auto delta_t = now - time_value;
60 printf("%u frames in %.9f ms (%g frames/sec)\n", FRAME_COUNT,
61 duration<double, std::milli>(delta_t).count(),
62 (float)FRAME_COUNT / duration<double>(delta_t).count());
68 return m_frames.size();
71 bool UnwindLLDB::AddFirstFrame() {
72 if (m_frames.size() > 0)
75 ProcessSP process_sp(m_thread.GetProcess());
76 ABI *abi = process_sp ? process_sp->GetABI().get() : nullptr;
78 // First, set up the 0th (initial) frame
79 CursorSP first_cursor_sp(new Cursor());
80 RegisterContextLLDBSP reg_ctx_sp(new RegisterContextLLDB(
81 m_thread, RegisterContextLLDBSP(), first_cursor_sp->sctx, 0, *this));
82 if (reg_ctx_sp.get() == nullptr)
85 if (!reg_ctx_sp->IsValid())
88 if (!reg_ctx_sp->GetCFA(first_cursor_sp->cfa))
91 if (!reg_ctx_sp->ReadPC(first_cursor_sp->start_pc))
94 // Everything checks out, so release the auto pointer value and let the
95 // cursor own it in its shared pointer
96 first_cursor_sp->reg_ctx_lldb_sp = reg_ctx_sp;
97 m_frames.push_back(first_cursor_sp);
99 // Update the Full Unwind Plan for this frame if not valid
100 UpdateUnwindPlanForFirstFrameIfInvalid(abi);
105 Log *log(GetLogIfAllCategoriesSet(LIBLLDB_LOG_UNWIND));
107 LLDB_LOGF(log, "th%d Unwind of this thread is complete.",
108 m_thread.GetIndexID());
110 m_unwind_complete = true;
114 UnwindLLDB::CursorSP UnwindLLDB::GetOneMoreFrame(ABI *abi) {
115 assert(m_frames.size() != 0 &&
116 "Get one more frame called with empty frame list");
118 // If we've already gotten to the end of the stack, don't bother to try
120 if (m_unwind_complete)
123 Log *log(GetLogIfAllCategoriesSet(LIBLLDB_LOG_UNWIND));
125 CursorSP prev_frame = m_frames.back();
126 uint32_t cur_idx = m_frames.size();
128 CursorSP cursor_sp(new Cursor());
129 RegisterContextLLDBSP reg_ctx_sp(new RegisterContextLLDB(
130 m_thread, prev_frame->reg_ctx_lldb_sp, cursor_sp->sctx, cur_idx, *this));
132 uint64_t max_stack_depth = m_thread.GetMaxBacktraceDepth();
134 // We want to detect an unwind that cycles erroneously and stop backtracing.
135 // Don't want this maximum unwind limit to be too low -- if you have a
136 // backtrace with an "infinitely recursing" bug, it will crash when the stack
137 // blows out and the first 35,000 frames are uninteresting - it's the top
138 // most 5 frames that you actually care about. So you can't just cap the
139 // unwind at 10,000 or something. Realistically anything over around 200,000
140 // is going to blow out the stack space. If we're still unwinding at that
141 // point, we're probably never going to finish.
142 if (cur_idx >= max_stack_depth) {
144 "%*sFrame %d unwound too many frames, assuming unwind has "
145 "gone astray, stopping.",
146 cur_idx < 100 ? cur_idx : 100, "", cur_idx);
150 if (reg_ctx_sp.get() == nullptr) {
151 // If the RegisterContextLLDB has a fallback UnwindPlan, it will switch to
152 // that and return true. Subsequent calls to TryFallbackUnwindPlan() will
154 if (prev_frame->reg_ctx_lldb_sp->TryFallbackUnwindPlan()) {
155 // TryFallbackUnwindPlan for prev_frame succeeded and updated
156 // reg_ctx_lldb_sp field of prev_frame. However, cfa field of prev_frame
157 // still needs to be updated. Hence updating it.
158 if (!(prev_frame->reg_ctx_lldb_sp->GetCFA(prev_frame->cfa)))
161 return GetOneMoreFrame(abi);
164 LLDB_LOGF(log, "%*sFrame %d did not get a RegisterContext, stopping.",
165 cur_idx < 100 ? cur_idx : 100, "", cur_idx);
169 if (!reg_ctx_sp->IsValid()) {
170 // We failed to get a valid RegisterContext. See if the regctx below this
171 // on the stack has a fallback unwind plan it can use. Subsequent calls to
172 // TryFallbackUnwindPlan() will return false.
173 if (prev_frame->reg_ctx_lldb_sp->TryFallbackUnwindPlan()) {
174 // TryFallbackUnwindPlan for prev_frame succeeded and updated
175 // reg_ctx_lldb_sp field of prev_frame. However, cfa field of prev_frame
176 // still needs to be updated. Hence updating it.
177 if (!(prev_frame->reg_ctx_lldb_sp->GetCFA(prev_frame->cfa)))
180 return GetOneMoreFrame(abi);
184 "%*sFrame %d invalid RegisterContext for this frame, "
185 "stopping stack walk",
186 cur_idx < 100 ? cur_idx : 100, "", cur_idx);
189 if (!reg_ctx_sp->GetCFA(cursor_sp->cfa)) {
190 // If the RegisterContextLLDB has a fallback UnwindPlan, it will switch to
191 // that and return true. Subsequent calls to TryFallbackUnwindPlan() will
193 if (prev_frame->reg_ctx_lldb_sp->TryFallbackUnwindPlan()) {
194 // TryFallbackUnwindPlan for prev_frame succeeded and updated
195 // reg_ctx_lldb_sp field of prev_frame. However, cfa field of prev_frame
196 // still needs to be updated. Hence updating it.
197 if (!(prev_frame->reg_ctx_lldb_sp->GetCFA(prev_frame->cfa)))
200 return GetOneMoreFrame(abi);
204 "%*sFrame %d did not get CFA for this frame, stopping stack walk",
205 cur_idx < 100 ? cur_idx : 100, "", cur_idx);
208 if (abi && !abi->CallFrameAddressIsValid(cursor_sp->cfa)) {
209 // On Mac OS X, the _sigtramp asynchronous signal trampoline frame may not
210 // have its (constructed) CFA aligned correctly -- don't do the abi
211 // alignment check for these.
212 if (!reg_ctx_sp->IsTrapHandlerFrame()) {
213 // See if we can find a fallback unwind plan for THIS frame. It may be
214 // that the UnwindPlan we're using for THIS frame was bad and gave us a
215 // bad CFA. If that's not it, then see if we can change the UnwindPlan
216 // for the frame below us ("NEXT") -- see if using that other UnwindPlan
217 // gets us a better unwind state.
218 if (!reg_ctx_sp->TryFallbackUnwindPlan() ||
219 !reg_ctx_sp->GetCFA(cursor_sp->cfa) ||
220 !abi->CallFrameAddressIsValid(cursor_sp->cfa)) {
221 if (prev_frame->reg_ctx_lldb_sp->TryFallbackUnwindPlan()) {
222 // TryFallbackUnwindPlan for prev_frame succeeded and updated
223 // reg_ctx_lldb_sp field of prev_frame. However, cfa field of
224 // prev_frame still needs to be updated. Hence updating it.
225 if (!(prev_frame->reg_ctx_lldb_sp->GetCFA(prev_frame->cfa)))
228 return GetOneMoreFrame(abi);
232 "%*sFrame %d did not get a valid CFA for this frame, "
233 "stopping stack walk",
234 cur_idx < 100 ? cur_idx : 100, "", cur_idx);
238 "%*sFrame %d had a bad CFA value but we switched the "
239 "UnwindPlan being used and got one that looks more "
241 cur_idx < 100 ? cur_idx : 100, "", cur_idx);
245 if (!reg_ctx_sp->ReadPC(cursor_sp->start_pc)) {
246 // If the RegisterContextLLDB has a fallback UnwindPlan, it will switch to
247 // that and return true. Subsequent calls to TryFallbackUnwindPlan() will
249 if (prev_frame->reg_ctx_lldb_sp->TryFallbackUnwindPlan()) {
250 // TryFallbackUnwindPlan for prev_frame succeeded and updated
251 // reg_ctx_lldb_sp field of prev_frame. However, cfa field of prev_frame
252 // still needs to be updated. Hence updating it.
253 if (!(prev_frame->reg_ctx_lldb_sp->GetCFA(prev_frame->cfa)))
256 return GetOneMoreFrame(abi);
260 "%*sFrame %d did not get PC for this frame, stopping stack walk",
261 cur_idx < 100 ? cur_idx : 100, "", cur_idx);
264 if (abi && !abi->CodeAddressIsValid(cursor_sp->start_pc)) {
265 // If the RegisterContextLLDB has a fallback UnwindPlan, it will switch to
266 // that and return true. Subsequent calls to TryFallbackUnwindPlan() will
268 if (prev_frame->reg_ctx_lldb_sp->TryFallbackUnwindPlan()) {
269 // TryFallbackUnwindPlan for prev_frame succeeded and updated
270 // reg_ctx_lldb_sp field of prev_frame. However, cfa field of prev_frame
271 // still needs to be updated. Hence updating it.
272 if (!(prev_frame->reg_ctx_lldb_sp->GetCFA(prev_frame->cfa)))
275 return GetOneMoreFrame(abi);
278 LLDB_LOGF(log, "%*sFrame %d did not get a valid PC, stopping stack walk",
279 cur_idx < 100 ? cur_idx : 100, "", cur_idx);
282 // Infinite loop where the current cursor is the same as the previous one...
283 if (prev_frame->start_pc == cursor_sp->start_pc &&
284 prev_frame->cfa == cursor_sp->cfa) {
286 "th%d pc of this frame is the same as the previous frame and "
287 "CFAs for both frames are identical -- stopping unwind",
288 m_thread.GetIndexID());
292 cursor_sp->reg_ctx_lldb_sp = reg_ctx_sp;
296 void UnwindLLDB::UpdateUnwindPlanForFirstFrameIfInvalid(ABI *abi) {
297 // This function is called for First Frame only.
298 assert(m_frames.size() == 1 && "No. of cursor frames are not 1");
300 bool old_m_unwind_complete = m_unwind_complete;
301 CursorSP old_m_candidate_frame = m_candidate_frame;
303 // Try to unwind 2 more frames using the Unwinder. It uses Full UnwindPlan
304 // and if Full UnwindPlan fails, then uses FallBack UnwindPlan. Also update
305 // the cfa of Frame 0 (if required).
306 AddOneMoreFrame(abi);
308 // Remove all the frames added by above function as the purpose of using
309 // above function was just to check whether Unwinder of Frame 0 works or not.
310 for (uint32_t i = 1; i < m_frames.size(); i++)
313 // Restore status after calling AddOneMoreFrame
314 m_unwind_complete = old_m_unwind_complete;
315 m_candidate_frame = old_m_candidate_frame;
319 bool UnwindLLDB::AddOneMoreFrame(ABI *abi) {
320 Log *log(GetLogIfAllCategoriesSet(LIBLLDB_LOG_UNWIND));
322 // Frame zero is a little different
323 if (m_frames.empty())
326 // If we've already gotten to the end of the stack, don't bother to try
328 if (m_unwind_complete)
331 CursorSP new_frame = m_candidate_frame;
332 if (new_frame == nullptr)
333 new_frame = GetOneMoreFrame(abi);
335 if (new_frame == nullptr) {
336 LLDB_LOGF(log, "th%d Unwind of this thread is complete.",
337 m_thread.GetIndexID());
338 m_unwind_complete = true;
342 m_frames.push_back(new_frame);
344 // If we can get one more frame further then accept that we get back a
346 m_candidate_frame = GetOneMoreFrame(abi);
347 if (m_candidate_frame)
350 // We can't go further from the frame returned by GetOneMore frame. Lets try
351 // to get a different frame with using the fallback unwind plan.
352 if (!m_frames[m_frames.size() - 2]
353 ->reg_ctx_lldb_sp->TryFallbackUnwindPlan()) {
354 // We don't have a valid fallback unwind plan. Accept the frame as it is.
355 // This is a valid situation when we are at the bottom of the stack.
359 // Remove the possibly incorrect frame from the frame list and try to add a
360 // different one with the newly selected fallback unwind plan.
362 CursorSP new_frame_v2 = GetOneMoreFrame(abi);
363 if (new_frame_v2 == nullptr) {
364 // We haven't got a new frame from the fallback unwind plan. Accept the
365 // frame from the original unwind plan. This is a valid situation when we
366 // are at the bottom of the stack.
367 m_frames.push_back(new_frame);
371 // Push the new frame to the list and try to continue from this frame. If we
372 // can get a new frame then accept it as the correct one.
373 m_frames.push_back(new_frame_v2);
374 m_candidate_frame = GetOneMoreFrame(abi);
375 if (m_candidate_frame) {
376 // If control reached here then TryFallbackUnwindPlan had succeeded for
377 // Cursor::m_frames[m_frames.size() - 2]. It also succeeded to Unwind next
378 // 2 frames i.e. m_frames[m_frames.size() - 1] and a frame after that. For
379 // Cursor::m_frames[m_frames.size() - 2], reg_ctx_lldb_sp field was already
380 // updated during TryFallbackUnwindPlan call above. However, cfa field
381 // still needs to be updated. Hence updating it here and then returning.
382 return m_frames[m_frames.size() - 2]->reg_ctx_lldb_sp->GetCFA(
383 m_frames[m_frames.size() - 2]->cfa);
386 // The new frame hasn't helped in unwinding. Fall back to the original one as
387 // the default unwind plan is usually more reliable then the fallback one.
389 m_frames.push_back(new_frame);
393 bool UnwindLLDB::DoGetFrameInfoAtIndex(uint32_t idx, addr_t &cfa, addr_t &pc,
394 bool &behaves_like_zeroth_frame) {
395 if (m_frames.size() == 0) {
396 if (!AddFirstFrame())
400 ProcessSP process_sp(m_thread.GetProcess());
401 ABI *abi = process_sp ? process_sp->GetABI().get() : nullptr;
403 while (idx >= m_frames.size() && AddOneMoreFrame(abi))
406 if (idx < m_frames.size()) {
407 cfa = m_frames[idx]->cfa;
408 pc = m_frames[idx]->start_pc;
410 // Frame zero always behaves like it.
411 behaves_like_zeroth_frame = true;
412 } else if (m_frames[idx - 1]->reg_ctx_lldb_sp->IsTrapHandlerFrame()) {
413 // This could be an asynchronous signal, thus the
414 // pc might point to the interrupted instruction rather
415 // than a post-call instruction
416 behaves_like_zeroth_frame = true;
417 } else if (m_frames[idx]->reg_ctx_lldb_sp->IsTrapHandlerFrame()) {
418 // This frame may result from signal processing installing
419 // a pointer to the first byte of a signal-return trampoline
420 // in the return address slot of the frame below, so this
421 // too behaves like the zeroth frame (i.e. the pc might not
422 // be pointing just past a call in it)
423 behaves_like_zeroth_frame = true;
425 behaves_like_zeroth_frame = false;
432 lldb::RegisterContextSP
433 UnwindLLDB::DoCreateRegisterContextForFrame(StackFrame *frame) {
434 lldb::RegisterContextSP reg_ctx_sp;
435 uint32_t idx = frame->GetConcreteFrameIndex();
438 return m_thread.GetRegisterContext();
441 if (m_frames.size() == 0) {
442 if (!AddFirstFrame())
446 ProcessSP process_sp(m_thread.GetProcess());
447 ABI *abi = process_sp ? process_sp->GetABI().get() : nullptr;
449 while (idx >= m_frames.size()) {
450 if (!AddOneMoreFrame(abi))
454 const uint32_t num_frames = m_frames.size();
455 if (idx < num_frames) {
456 Cursor *frame_cursor = m_frames[idx].get();
457 reg_ctx_sp = frame_cursor->reg_ctx_lldb_sp;
462 UnwindLLDB::RegisterContextLLDBSP
463 UnwindLLDB::GetRegisterContextForFrameNum(uint32_t frame_num) {
464 RegisterContextLLDBSP reg_ctx_sp;
465 if (frame_num < m_frames.size())
466 reg_ctx_sp = m_frames[frame_num]->reg_ctx_lldb_sp;
470 bool UnwindLLDB::SearchForSavedLocationForRegister(
471 uint32_t lldb_regnum, lldb_private::UnwindLLDB::RegisterLocation ®loc,
472 uint32_t starting_frame_num, bool pc_reg) {
473 int64_t frame_num = starting_frame_num;
474 if (static_cast<size_t>(frame_num) >= m_frames.size())
477 // Never interrogate more than one level while looking for the saved pc
478 // value. If the value isn't saved by frame_num, none of the frames lower on
479 // the stack will have a useful value.
481 UnwindLLDB::RegisterSearchResult result;
482 result = m_frames[frame_num]->reg_ctx_lldb_sp->SavedLocationForRegister(
483 lldb_regnum, regloc);
484 return result == UnwindLLDB::RegisterSearchResult::eRegisterFound;
486 while (frame_num >= 0) {
487 UnwindLLDB::RegisterSearchResult result;
488 result = m_frames[frame_num]->reg_ctx_lldb_sp->SavedLocationForRegister(
489 lldb_regnum, regloc);
491 // We descended down to the live register context aka stack frame 0 and are
492 // reading the value out of a live register.
493 if (result == UnwindLLDB::RegisterSearchResult::eRegisterFound &&
495 UnwindLLDB::RegisterLocation::eRegisterInLiveRegisterContext) {
499 // If we have unwind instructions saying that register N is saved in
500 // register M in the middle of the stack (and N can equal M here, meaning
501 // the register was not used in this function), then change the register
502 // number we're looking for to M and keep looking for a concrete location
503 // down the stack, or an actual value from a live RegisterContext at frame
505 if (result == UnwindLLDB::RegisterSearchResult::eRegisterFound &&
506 regloc.type == UnwindLLDB::RegisterLocation::eRegisterInRegister &&
508 result = UnwindLLDB::RegisterSearchResult::eRegisterNotFound;
509 lldb_regnum = regloc.location.register_number;
512 if (result == UnwindLLDB::RegisterSearchResult::eRegisterFound)
514 if (result == UnwindLLDB::RegisterSearchResult::eRegisterIsVolatile)