1 //===-- UnwindLLDB.cpp -------------------------------------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 #include "lldb/Core/Module.h"
11 #include "lldb/Symbol/FuncUnwinders.h"
12 #include "lldb/Symbol/Function.h"
13 #include "lldb/Symbol/UnwindPlan.h"
14 #include "lldb/Target/ABI.h"
15 #include "lldb/Target/Process.h"
16 #include "lldb/Target/RegisterContext.h"
17 #include "lldb/Target/Target.h"
18 #include "lldb/Target/Thread.h"
19 #include "lldb/Utility/Log.h"
21 #include "RegisterContextLLDB.h"
22 #include "UnwindLLDB.h"
25 using namespace lldb_private;
27 UnwindLLDB::UnwindLLDB(Thread &thread)
28 : Unwind(thread), m_frames(), m_unwind_complete(false),
29 m_user_supplied_trap_handler_functions() {
30 ProcessSP process_sp(thread.GetProcess());
33 process_sp->GetTarget().GetUserSpecifiedTrapHandlerNames(args);
34 size_t count = args.GetArgumentCount();
35 for (size_t i = 0; i < count; i++) {
36 const char *func_name = args.GetArgumentAtIndex(i);
37 m_user_supplied_trap_handler_functions.push_back(ConstString(func_name));
42 uint32_t UnwindLLDB::DoGetFrameCount() {
43 if (!m_unwind_complete) {
44 //#define DEBUG_FRAME_SPEED 1
46 #define FRAME_COUNT 10000
47 using namespace std::chrono;
48 auto time_value = steady_clock::now();
53 ProcessSP process_sp(m_thread.GetProcess());
54 ABI *abi = process_sp ? process_sp->GetABI().get() : NULL;
56 while (AddOneMoreFrame(abi)) {
58 if ((m_frames.size() % FRAME_COUNT) == 0) {
59 const auto now = steady_clock::now();
60 const auto delta_t = now - time_value;
61 printf("%u frames in %.9f ms (%g frames/sec)\n", FRAME_COUNT,
62 duration<double, std::milli>(delta_t).count(),
63 (float)FRAME_COUNT / duration<double>(delta_t).count());
69 return m_frames.size();
72 bool UnwindLLDB::AddFirstFrame() {
73 if (m_frames.size() > 0)
76 ProcessSP process_sp(m_thread.GetProcess());
77 ABI *abi = process_sp ? process_sp->GetABI().get() : NULL;
79 // First, set up the 0th (initial) frame
80 CursorSP first_cursor_sp(new Cursor());
81 RegisterContextLLDBSP reg_ctx_sp(new RegisterContextLLDB(
82 m_thread, RegisterContextLLDBSP(), first_cursor_sp->sctx, 0, *this));
83 if (reg_ctx_sp.get() == NULL)
86 if (!reg_ctx_sp->IsValid())
89 if (!reg_ctx_sp->GetCFA(first_cursor_sp->cfa))
92 if (!reg_ctx_sp->ReadPC(first_cursor_sp->start_pc))
95 // Everything checks out, so release the auto pointer value and let the
96 // cursor own it in its shared pointer
97 first_cursor_sp->reg_ctx_lldb_sp = reg_ctx_sp;
98 m_frames.push_back(first_cursor_sp);
100 // Update the Full Unwind Plan for this frame if not valid
101 UpdateUnwindPlanForFirstFrameIfInvalid(abi);
106 Log *log(GetLogIfAllCategoriesSet(LIBLLDB_LOG_UNWIND));
108 log->Printf("th%d Unwind of this thread is complete.",
109 m_thread.GetIndexID());
111 m_unwind_complete = true;
115 UnwindLLDB::CursorSP UnwindLLDB::GetOneMoreFrame(ABI *abi) {
116 assert(m_frames.size() != 0 &&
117 "Get one more frame called with empty frame list");
119 // If we've already gotten to the end of the stack, don't bother to try
121 if (m_unwind_complete)
124 Log *log(GetLogIfAllCategoriesSet(LIBLLDB_LOG_UNWIND));
126 CursorSP prev_frame = m_frames.back();
127 uint32_t cur_idx = m_frames.size();
129 CursorSP cursor_sp(new Cursor());
130 RegisterContextLLDBSP reg_ctx_sp(new RegisterContextLLDB(
131 m_thread, prev_frame->reg_ctx_lldb_sp, cursor_sp->sctx, cur_idx, *this));
133 // We want to detect an unwind that cycles erroneously and stop backtracing.
134 // Don't want this maximum unwind limit to be too low -- if you have a
135 // backtrace with an "infinitely recursing" bug, it will crash when the stack
136 // blows out and the first 35,000 frames are uninteresting - it's the top
137 // most 5 frames that you actually care about. So you can't just cap the
138 // unwind at 10,000 or something. Realistically anything over around 200,000
139 // is going to blow out the stack space. If we're still unwinding at that
140 // point, we're probably never going to finish.
141 if (cur_idx > 300000) {
143 log->Printf("%*sFrame %d unwound too many frames, assuming unwind has "
144 "gone astray, stopping.",
145 cur_idx < 100 ? cur_idx : 100, "", cur_idx);
149 if (reg_ctx_sp.get() == NULL) {
150 // If the RegisterContextLLDB has a fallback UnwindPlan, it will switch to
151 // that and return true. Subsequent calls to TryFallbackUnwindPlan() will
153 if (prev_frame->reg_ctx_lldb_sp->TryFallbackUnwindPlan()) {
154 // TryFallbackUnwindPlan for prev_frame succeeded and updated
155 // reg_ctx_lldb_sp field of prev_frame. However, cfa field of prev_frame
156 // still needs to be updated. Hence updating it.
157 if (!(prev_frame->reg_ctx_lldb_sp->GetCFA(prev_frame->cfa)))
160 return GetOneMoreFrame(abi);
164 log->Printf("%*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 log->Printf("%*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);
205 "%*sFrame %d did not get CFA for this frame, stopping stack walk",
206 cur_idx < 100 ? cur_idx : 100, "", cur_idx);
209 if (abi && !abi->CallFrameAddressIsValid(cursor_sp->cfa)) {
210 // On Mac OS X, the _sigtramp asynchronous signal trampoline frame may not
211 // have its (constructed) CFA aligned correctly -- don't do the abi
212 // alignment check for these.
213 if (reg_ctx_sp->IsTrapHandlerFrame() == false) {
214 // See if we can find a fallback unwind plan for THIS frame. It may be
215 // that the UnwindPlan we're using for THIS frame was bad and gave us a
216 // bad CFA. If that's not it, then see if we can change the UnwindPlan
217 // for the frame below us ("NEXT") -- see if using that other UnwindPlan
218 // gets us a better unwind state.
219 if (reg_ctx_sp->TryFallbackUnwindPlan() == false ||
220 reg_ctx_sp->GetCFA(cursor_sp->cfa) == false ||
221 abi->CallFrameAddressIsValid(cursor_sp->cfa) == false) {
222 if (prev_frame->reg_ctx_lldb_sp->TryFallbackUnwindPlan()) {
223 // TryFallbackUnwindPlan for prev_frame succeeded and updated
224 // reg_ctx_lldb_sp field of prev_frame. However, cfa field of
225 // prev_frame still needs to be updated. Hence updating it.
226 if (!(prev_frame->reg_ctx_lldb_sp->GetCFA(prev_frame->cfa)))
229 return GetOneMoreFrame(abi);
233 log->Printf("%*sFrame %d did not get a valid CFA for this frame, "
234 "stopping stack walk",
235 cur_idx < 100 ? cur_idx : 100, "", cur_idx);
239 log->Printf("%*sFrame %d had a bad CFA value but we switched the "
240 "UnwindPlan being used and got one that looks more "
242 cur_idx < 100 ? cur_idx : 100, "", cur_idx);
246 if (!reg_ctx_sp->ReadPC(cursor_sp->start_pc)) {
247 // If the RegisterContextLLDB has a fallback UnwindPlan, it will switch to
248 // that and return true. Subsequent calls to TryFallbackUnwindPlan() will
250 if (prev_frame->reg_ctx_lldb_sp->TryFallbackUnwindPlan()) {
251 // TryFallbackUnwindPlan for prev_frame succeeded and updated
252 // reg_ctx_lldb_sp field of prev_frame. However, cfa field of prev_frame
253 // still needs to be updated. Hence updating it.
254 if (!(prev_frame->reg_ctx_lldb_sp->GetCFA(prev_frame->cfa)))
257 return GetOneMoreFrame(abi);
262 "%*sFrame %d did not get PC for this frame, stopping stack walk",
263 cur_idx < 100 ? cur_idx : 100, "", cur_idx);
266 if (abi && !abi->CodeAddressIsValid(cursor_sp->start_pc)) {
267 // If the RegisterContextLLDB has a fallback UnwindPlan, it will switch to
268 // that and return true. Subsequent calls to TryFallbackUnwindPlan() will
270 if (prev_frame->reg_ctx_lldb_sp->TryFallbackUnwindPlan()) {
271 // TryFallbackUnwindPlan for prev_frame succeeded and updated
272 // reg_ctx_lldb_sp field of prev_frame. However, cfa field of prev_frame
273 // still needs to be updated. Hence updating it.
274 if (!(prev_frame->reg_ctx_lldb_sp->GetCFA(prev_frame->cfa)))
277 return GetOneMoreFrame(abi);
281 log->Printf("%*sFrame %d did not get a valid PC, stopping stack walk",
282 cur_idx < 100 ? cur_idx : 100, "", cur_idx);
285 // Infinite loop where the current cursor is the same as the previous one...
286 if (prev_frame->start_pc == cursor_sp->start_pc &&
287 prev_frame->cfa == cursor_sp->cfa) {
289 log->Printf("th%d pc of this frame is the same as the previous frame and "
290 "CFAs for both frames are identical -- stopping unwind",
291 m_thread.GetIndexID());
295 cursor_sp->reg_ctx_lldb_sp = reg_ctx_sp;
299 void UnwindLLDB::UpdateUnwindPlanForFirstFrameIfInvalid(ABI *abi) {
300 // This function is called for First Frame only.
301 assert(m_frames.size() == 1 && "No. of cursor frames are not 1");
303 bool old_m_unwind_complete = m_unwind_complete;
304 CursorSP old_m_candidate_frame = m_candidate_frame;
306 // Try to unwind 2 more frames using the Unwinder. It uses Full UnwindPlan
307 // and if Full UnwindPlan fails, then uses FallBack UnwindPlan. Also update
308 // the cfa of Frame 0 (if required).
309 AddOneMoreFrame(abi);
311 // Remove all the frames added by above function as the purpose of using
312 // above function was just to check whether Unwinder of Frame 0 works or not.
313 for (uint32_t i = 1; i < m_frames.size(); i++)
316 // Restore status after calling AddOneMoreFrame
317 m_unwind_complete = old_m_unwind_complete;
318 m_candidate_frame = old_m_candidate_frame;
322 bool UnwindLLDB::AddOneMoreFrame(ABI *abi) {
323 Log *log(GetLogIfAllCategoriesSet(LIBLLDB_LOG_UNWIND));
325 // Frame zero is a little different
326 if (m_frames.empty())
329 // If we've already gotten to the end of the stack, don't bother to try
331 if (m_unwind_complete)
334 CursorSP new_frame = m_candidate_frame;
335 if (new_frame == nullptr)
336 new_frame = GetOneMoreFrame(abi);
338 if (new_frame == nullptr) {
340 log->Printf("th%d Unwind of this thread is complete.",
341 m_thread.GetIndexID());
342 m_unwind_complete = true;
346 m_frames.push_back(new_frame);
348 // If we can get one more frame further then accept that we get back a
350 m_candidate_frame = GetOneMoreFrame(abi);
351 if (m_candidate_frame)
354 // We can't go further from the frame returned by GetOneMore frame. Lets try
355 // to get a different frame with using the fallback unwind plan.
356 if (!m_frames[m_frames.size() - 2]
357 ->reg_ctx_lldb_sp->TryFallbackUnwindPlan()) {
358 // We don't have a valid fallback unwind plan. Accept the frame as it is.
359 // This is a valid situation when we are at the bottom of the stack.
363 // Remove the possibly incorrect frame from the frame list and try to add a
364 // different one with the newly selected fallback unwind plan.
366 CursorSP new_frame_v2 = GetOneMoreFrame(abi);
367 if (new_frame_v2 == nullptr) {
368 // We haven't got a new frame from the fallback unwind plan. Accept the
369 // frame from the original unwind plan. This is a valid situation when we
370 // are at the bottom of the stack.
371 m_frames.push_back(new_frame);
375 // Push the new frame to the list and try to continue from this frame. If we
376 // can get a new frame then accept it as the correct one.
377 m_frames.push_back(new_frame_v2);
378 m_candidate_frame = GetOneMoreFrame(abi);
379 if (m_candidate_frame) {
380 // If control reached here then TryFallbackUnwindPlan had succeeded for
381 // Cursor::m_frames[m_frames.size() - 2]. It also succeeded to Unwind next
382 // 2 frames i.e. m_frames[m_frames.size() - 1] and a frame after that. For
383 // Cursor::m_frames[m_frames.size() - 2], reg_ctx_lldb_sp field was already
384 // updated during TryFallbackUnwindPlan call above. However, cfa field
385 // still needs to be updated. Hence updating it here and then returning.
386 if (!(m_frames[m_frames.size() - 2]->reg_ctx_lldb_sp->GetCFA(
387 m_frames[m_frames.size() - 2]->cfa)))
392 // The new frame hasn't helped in unwinding. Fall back to the original one as
393 // the default unwind plan is usually more reliable then the fallback one.
395 m_frames.push_back(new_frame);
399 bool UnwindLLDB::DoGetFrameInfoAtIndex(uint32_t idx, addr_t &cfa, addr_t &pc) {
400 if (m_frames.size() == 0) {
401 if (!AddFirstFrame())
405 ProcessSP process_sp(m_thread.GetProcess());
406 ABI *abi = process_sp ? process_sp->GetABI().get() : NULL;
408 while (idx >= m_frames.size() && AddOneMoreFrame(abi))
411 if (idx < m_frames.size()) {
412 cfa = m_frames[idx]->cfa;
413 pc = m_frames[idx]->start_pc;
419 lldb::RegisterContextSP
420 UnwindLLDB::DoCreateRegisterContextForFrame(StackFrame *frame) {
421 lldb::RegisterContextSP reg_ctx_sp;
422 uint32_t idx = frame->GetConcreteFrameIndex();
425 return m_thread.GetRegisterContext();
428 if (m_frames.size() == 0) {
429 if (!AddFirstFrame())
433 ProcessSP process_sp(m_thread.GetProcess());
434 ABI *abi = process_sp ? process_sp->GetABI().get() : NULL;
436 while (idx >= m_frames.size()) {
437 if (!AddOneMoreFrame(abi))
441 const uint32_t num_frames = m_frames.size();
442 if (idx < num_frames) {
443 Cursor *frame_cursor = m_frames[idx].get();
444 reg_ctx_sp = frame_cursor->reg_ctx_lldb_sp;
449 UnwindLLDB::RegisterContextLLDBSP
450 UnwindLLDB::GetRegisterContextForFrameNum(uint32_t frame_num) {
451 RegisterContextLLDBSP reg_ctx_sp;
452 if (frame_num < m_frames.size())
453 reg_ctx_sp = m_frames[frame_num]->reg_ctx_lldb_sp;
457 bool UnwindLLDB::SearchForSavedLocationForRegister(
458 uint32_t lldb_regnum, lldb_private::UnwindLLDB::RegisterLocation ®loc,
459 uint32_t starting_frame_num, bool pc_reg) {
460 int64_t frame_num = starting_frame_num;
461 if (static_cast<size_t>(frame_num) >= m_frames.size())
464 // Never interrogate more than one level while looking for the saved pc
465 // value. If the value isn't saved by frame_num, none of the frames lower on
466 // the stack will have a useful value.
468 UnwindLLDB::RegisterSearchResult result;
469 result = m_frames[frame_num]->reg_ctx_lldb_sp->SavedLocationForRegister(
470 lldb_regnum, regloc);
471 if (result == UnwindLLDB::RegisterSearchResult::eRegisterFound)
476 while (frame_num >= 0) {
477 UnwindLLDB::RegisterSearchResult result;
478 result = m_frames[frame_num]->reg_ctx_lldb_sp->SavedLocationForRegister(
479 lldb_regnum, regloc);
481 // We descended down to the live register context aka stack frame 0 and are
482 // reading the value out of a live register.
483 if (result == UnwindLLDB::RegisterSearchResult::eRegisterFound &&
485 UnwindLLDB::RegisterLocation::eRegisterInLiveRegisterContext) {
489 // If we have unwind instructions saying that register N is saved in
490 // register M in the middle of the stack (and N can equal M here, meaning
491 // the register was not used in this function), then change the register
492 // number we're looking for to M and keep looking for a concrete location
493 // down the stack, or an actual value from a live RegisterContext at frame
495 if (result == UnwindLLDB::RegisterSearchResult::eRegisterFound &&
496 regloc.type == UnwindLLDB::RegisterLocation::eRegisterInRegister &&
498 result = UnwindLLDB::RegisterSearchResult::eRegisterNotFound;
499 lldb_regnum = regloc.location.register_number;
502 if (result == UnwindLLDB::RegisterSearchResult::eRegisterFound)
504 if (result == UnwindLLDB::RegisterSearchResult::eRegisterIsVolatile)