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 uint64_t max_stack_depth = m_thread.GetMaxBacktraceDepth();
135 // We want to detect an unwind that cycles erroneously and stop backtracing.
136 // Don't want this maximum unwind limit to be too low -- if you have a
137 // backtrace with an "infinitely recursing" bug, it will crash when the stack
138 // blows out and the first 35,000 frames are uninteresting - it's the top
139 // most 5 frames that you actually care about. So you can't just cap the
140 // unwind at 10,000 or something. Realistically anything over around 200,000
141 // is going to blow out the stack space. If we're still unwinding at that
142 // point, we're probably never going to finish.
143 if (cur_idx >= max_stack_depth) {
145 log->Printf("%*sFrame %d unwound too many frames, assuming unwind has "
146 "gone astray, stopping.",
147 cur_idx < 100 ? cur_idx : 100, "", cur_idx);
151 if (reg_ctx_sp.get() == NULL) {
152 // If the RegisterContextLLDB has a fallback UnwindPlan, it will switch to
153 // that and return true. Subsequent calls to TryFallbackUnwindPlan() will
155 if (prev_frame->reg_ctx_lldb_sp->TryFallbackUnwindPlan()) {
156 // TryFallbackUnwindPlan for prev_frame succeeded and updated
157 // reg_ctx_lldb_sp field of prev_frame. However, cfa field of prev_frame
158 // still needs to be updated. Hence updating it.
159 if (!(prev_frame->reg_ctx_lldb_sp->GetCFA(prev_frame->cfa)))
162 return GetOneMoreFrame(abi);
166 log->Printf("%*sFrame %d did not get a RegisterContext, stopping.",
167 cur_idx < 100 ? cur_idx : 100, "", cur_idx);
171 if (!reg_ctx_sp->IsValid()) {
172 // We failed to get a valid RegisterContext. See if the regctx below this
173 // on the stack has a fallback unwind plan it can use. Subsequent calls to
174 // TryFallbackUnwindPlan() will return false.
175 if (prev_frame->reg_ctx_lldb_sp->TryFallbackUnwindPlan()) {
176 // TryFallbackUnwindPlan for prev_frame succeeded and updated
177 // reg_ctx_lldb_sp field of prev_frame. However, cfa field of prev_frame
178 // still needs to be updated. Hence updating it.
179 if (!(prev_frame->reg_ctx_lldb_sp->GetCFA(prev_frame->cfa)))
182 return GetOneMoreFrame(abi);
186 log->Printf("%*sFrame %d invalid RegisterContext for this frame, "
187 "stopping stack walk",
188 cur_idx < 100 ? cur_idx : 100, "", cur_idx);
191 if (!reg_ctx_sp->GetCFA(cursor_sp->cfa)) {
192 // If the RegisterContextLLDB has a fallback UnwindPlan, it will switch to
193 // that and return true. Subsequent calls to TryFallbackUnwindPlan() will
195 if (prev_frame->reg_ctx_lldb_sp->TryFallbackUnwindPlan()) {
196 // TryFallbackUnwindPlan for prev_frame succeeded and updated
197 // reg_ctx_lldb_sp field of prev_frame. However, cfa field of prev_frame
198 // still needs to be updated. Hence updating it.
199 if (!(prev_frame->reg_ctx_lldb_sp->GetCFA(prev_frame->cfa)))
202 return GetOneMoreFrame(abi);
207 "%*sFrame %d did not get CFA for this frame, stopping stack walk",
208 cur_idx < 100 ? cur_idx : 100, "", cur_idx);
211 if (abi && !abi->CallFrameAddressIsValid(cursor_sp->cfa)) {
212 // On Mac OS X, the _sigtramp asynchronous signal trampoline frame may not
213 // have its (constructed) CFA aligned correctly -- don't do the abi
214 // alignment check for these.
215 if (!reg_ctx_sp->IsTrapHandlerFrame()) {
216 // See if we can find a fallback unwind plan for THIS frame. It may be
217 // that the UnwindPlan we're using for THIS frame was bad and gave us a
218 // bad CFA. If that's not it, then see if we can change the UnwindPlan
219 // for the frame below us ("NEXT") -- see if using that other UnwindPlan
220 // gets us a better unwind state.
221 if (!reg_ctx_sp->TryFallbackUnwindPlan() ||
222 !reg_ctx_sp->GetCFA(cursor_sp->cfa) ||
223 !abi->CallFrameAddressIsValid(cursor_sp->cfa)) {
224 if (prev_frame->reg_ctx_lldb_sp->TryFallbackUnwindPlan()) {
225 // TryFallbackUnwindPlan for prev_frame succeeded and updated
226 // reg_ctx_lldb_sp field of prev_frame. However, cfa field of
227 // prev_frame still needs to be updated. Hence updating it.
228 if (!(prev_frame->reg_ctx_lldb_sp->GetCFA(prev_frame->cfa)))
231 return GetOneMoreFrame(abi);
235 log->Printf("%*sFrame %d did not get a valid CFA for this frame, "
236 "stopping stack walk",
237 cur_idx < 100 ? cur_idx : 100, "", cur_idx);
241 log->Printf("%*sFrame %d had a bad CFA value but we switched the "
242 "UnwindPlan being used and got one that looks more "
244 cur_idx < 100 ? cur_idx : 100, "", cur_idx);
248 if (!reg_ctx_sp->ReadPC(cursor_sp->start_pc)) {
249 // If the RegisterContextLLDB has a fallback UnwindPlan, it will switch to
250 // that and return true. Subsequent calls to TryFallbackUnwindPlan() will
252 if (prev_frame->reg_ctx_lldb_sp->TryFallbackUnwindPlan()) {
253 // TryFallbackUnwindPlan for prev_frame succeeded and updated
254 // reg_ctx_lldb_sp field of prev_frame. However, cfa field of prev_frame
255 // still needs to be updated. Hence updating it.
256 if (!(prev_frame->reg_ctx_lldb_sp->GetCFA(prev_frame->cfa)))
259 return GetOneMoreFrame(abi);
264 "%*sFrame %d did not get PC for this frame, stopping stack walk",
265 cur_idx < 100 ? cur_idx : 100, "", cur_idx);
268 if (abi && !abi->CodeAddressIsValid(cursor_sp->start_pc)) {
269 // If the RegisterContextLLDB has a fallback UnwindPlan, it will switch to
270 // that and return true. Subsequent calls to TryFallbackUnwindPlan() will
272 if (prev_frame->reg_ctx_lldb_sp->TryFallbackUnwindPlan()) {
273 // TryFallbackUnwindPlan for prev_frame succeeded and updated
274 // reg_ctx_lldb_sp field of prev_frame. However, cfa field of prev_frame
275 // still needs to be updated. Hence updating it.
276 if (!(prev_frame->reg_ctx_lldb_sp->GetCFA(prev_frame->cfa)))
279 return GetOneMoreFrame(abi);
283 log->Printf("%*sFrame %d did not get a valid PC, stopping stack walk",
284 cur_idx < 100 ? cur_idx : 100, "", cur_idx);
287 // Infinite loop where the current cursor is the same as the previous one...
288 if (prev_frame->start_pc == cursor_sp->start_pc &&
289 prev_frame->cfa == cursor_sp->cfa) {
291 log->Printf("th%d pc of this frame is the same as the previous frame and "
292 "CFAs for both frames are identical -- stopping unwind",
293 m_thread.GetIndexID());
297 cursor_sp->reg_ctx_lldb_sp = reg_ctx_sp;
301 void UnwindLLDB::UpdateUnwindPlanForFirstFrameIfInvalid(ABI *abi) {
302 // This function is called for First Frame only.
303 assert(m_frames.size() == 1 && "No. of cursor frames are not 1");
305 bool old_m_unwind_complete = m_unwind_complete;
306 CursorSP old_m_candidate_frame = m_candidate_frame;
308 // Try to unwind 2 more frames using the Unwinder. It uses Full UnwindPlan
309 // and if Full UnwindPlan fails, then uses FallBack UnwindPlan. Also update
310 // the cfa of Frame 0 (if required).
311 AddOneMoreFrame(abi);
313 // Remove all the frames added by above function as the purpose of using
314 // above function was just to check whether Unwinder of Frame 0 works or not.
315 for (uint32_t i = 1; i < m_frames.size(); i++)
318 // Restore status after calling AddOneMoreFrame
319 m_unwind_complete = old_m_unwind_complete;
320 m_candidate_frame = old_m_candidate_frame;
324 bool UnwindLLDB::AddOneMoreFrame(ABI *abi) {
325 Log *log(GetLogIfAllCategoriesSet(LIBLLDB_LOG_UNWIND));
327 // Frame zero is a little different
328 if (m_frames.empty())
331 // If we've already gotten to the end of the stack, don't bother to try
333 if (m_unwind_complete)
336 CursorSP new_frame = m_candidate_frame;
337 if (new_frame == nullptr)
338 new_frame = GetOneMoreFrame(abi);
340 if (new_frame == nullptr) {
342 log->Printf("th%d Unwind of this thread is complete.",
343 m_thread.GetIndexID());
344 m_unwind_complete = true;
348 m_frames.push_back(new_frame);
350 // If we can get one more frame further then accept that we get back a
352 m_candidate_frame = GetOneMoreFrame(abi);
353 if (m_candidate_frame)
356 // We can't go further from the frame returned by GetOneMore frame. Lets try
357 // to get a different frame with using the fallback unwind plan.
358 if (!m_frames[m_frames.size() - 2]
359 ->reg_ctx_lldb_sp->TryFallbackUnwindPlan()) {
360 // We don't have a valid fallback unwind plan. Accept the frame as it is.
361 // This is a valid situation when we are at the bottom of the stack.
365 // Remove the possibly incorrect frame from the frame list and try to add a
366 // different one with the newly selected fallback unwind plan.
368 CursorSP new_frame_v2 = GetOneMoreFrame(abi);
369 if (new_frame_v2 == nullptr) {
370 // We haven't got a new frame from the fallback unwind plan. Accept the
371 // frame from the original unwind plan. This is a valid situation when we
372 // are at the bottom of the stack.
373 m_frames.push_back(new_frame);
377 // Push the new frame to the list and try to continue from this frame. If we
378 // can get a new frame then accept it as the correct one.
379 m_frames.push_back(new_frame_v2);
380 m_candidate_frame = GetOneMoreFrame(abi);
381 if (m_candidate_frame) {
382 // If control reached here then TryFallbackUnwindPlan had succeeded for
383 // Cursor::m_frames[m_frames.size() - 2]. It also succeeded to Unwind next
384 // 2 frames i.e. m_frames[m_frames.size() - 1] and a frame after that. For
385 // Cursor::m_frames[m_frames.size() - 2], reg_ctx_lldb_sp field was already
386 // updated during TryFallbackUnwindPlan call above. However, cfa field
387 // still needs to be updated. Hence updating it here and then returning.
388 return m_frames[m_frames.size() - 2]->reg_ctx_lldb_sp->GetCFA(
389 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 return result == UnwindLLDB::RegisterSearchResult::eRegisterFound;
473 while (frame_num >= 0) {
474 UnwindLLDB::RegisterSearchResult result;
475 result = m_frames[frame_num]->reg_ctx_lldb_sp->SavedLocationForRegister(
476 lldb_regnum, regloc);
478 // We descended down to the live register context aka stack frame 0 and are
479 // reading the value out of a live register.
480 if (result == UnwindLLDB::RegisterSearchResult::eRegisterFound &&
482 UnwindLLDB::RegisterLocation::eRegisterInLiveRegisterContext) {
486 // If we have unwind instructions saying that register N is saved in
487 // register M in the middle of the stack (and N can equal M here, meaning
488 // the register was not used in this function), then change the register
489 // number we're looking for to M and keep looking for a concrete location
490 // down the stack, or an actual value from a live RegisterContext at frame
492 if (result == UnwindLLDB::RegisterSearchResult::eRegisterFound &&
493 regloc.type == UnwindLLDB::RegisterLocation::eRegisterInRegister &&
495 result = UnwindLLDB::RegisterSearchResult::eRegisterNotFound;
496 lldb_regnum = regloc.location.register_number;
499 if (result == UnwindLLDB::RegisterSearchResult::eRegisterFound)
501 if (result == UnwindLLDB::RegisterSearchResult::eRegisterIsVolatile)