1 //===-- ThreadPlanStepOut.cpp -----------------------------------*- C++ -*-===//
2 //
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
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #include "lldb/Target/ThreadPlanStepOut.h"
10 #include "lldb/Breakpoint/Breakpoint.h"
11 #include "lldb/Core/Value.h"
12 #include "lldb/Core/ValueObjectConstResult.h"
13 #include "lldb/Symbol/Block.h"
14 #include "lldb/Symbol/Function.h"
15 #include "lldb/Symbol/Symbol.h"
16 #include "lldb/Symbol/Type.h"
17 #include "lldb/Target/ABI.h"
18 #include "lldb/Target/Process.h"
19 #include "lldb/Target/RegisterContext.h"
20 #include "lldb/Target/StopInfo.h"
21 #include "lldb/Target/Target.h"
22 #include "lldb/Target/ThreadPlanStepOverRange.h"
23 #include "lldb/Target/ThreadPlanStepThrough.h"
24 #include "lldb/Utility/Log.h"
25 
26 #include <memory>
27 
28 using namespace lldb;
29 using namespace lldb_private;
30 
31 uint32_t ThreadPlanStepOut::s_default_flag_values = 0;
32 
33 // ThreadPlanStepOut: Step out of the current frame
34 ThreadPlanStepOut::ThreadPlanStepOut(
35     Thread &thread, SymbolContext *context, bool first_insn, bool stop_others,
36     Vote stop_vote, Vote run_vote, uint32_t frame_idx,
37     LazyBool step_out_avoids_code_without_debug_info,
38     bool continue_to_next_branch, bool gather_return_value)
39     : ThreadPlan(ThreadPlan::eKindStepOut, "Step out", thread, stop_vote,
40                  run_vote),
41       ThreadPlanShouldStopHere(this), m_step_from_insn(LLDB_INVALID_ADDRESS),
42       m_return_bp_id(LLDB_INVALID_BREAK_ID),
43       m_return_addr(LLDB_INVALID_ADDRESS), m_stop_others(stop_others),
44       m_immediate_step_from_function(nullptr),
45       m_calculate_return_value(gather_return_value) {
46   Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_STEP));
47   SetFlagsToDefault();
48   SetupAvoidNoDebug(step_out_avoids_code_without_debug_info);
49 
50   m_step_from_insn = m_thread.GetRegisterContext()->GetPC(0);
51 
52   uint32_t return_frame_index = frame_idx + 1;
53   StackFrameSP return_frame_sp(
54       m_thread.GetStackFrameAtIndex(return_frame_index));
55   StackFrameSP immediate_return_from_sp(
56       m_thread.GetStackFrameAtIndex(frame_idx));
57 
58   if (!return_frame_sp || !immediate_return_from_sp)
59     return; // we can't do anything here.  ValidatePlan() will return false.
60 
61   // While stepping out, behave as-if artificial frames are not present.
62   while (return_frame_sp->IsArtificial()) {
63     m_stepped_past_frames.push_back(return_frame_sp);
64 
65     ++return_frame_index;
66     return_frame_sp = m_thread.GetStackFrameAtIndex(return_frame_index);
67 
68     // We never expect to see an artificial frame without a regular ancestor.
69     // If this happens, log the issue and defensively refuse to step out.
70     if (!return_frame_sp) {
71       LLDB_LOG(log, "Can't step out of frame with artificial ancestors");
72       return;
73     }
74   }
75 
76   m_step_out_to_id = return_frame_sp->GetStackID();
77   m_immediate_step_from_id = immediate_return_from_sp->GetStackID();
78 
79   // If the frame directly below the one we are returning to is inlined, we
80   // have to be a little more careful.  It is non-trivial to determine the real
81   // "return code address" for an inlined frame, so we have to work our way to
82   // that frame and then step out.
83   if (immediate_return_from_sp->IsInlined()) {
84     if (frame_idx > 0) {
85       // First queue a plan that gets us to this inlined frame, and when we get
86       // there we'll queue a second plan that walks us out of this frame.
87       m_step_out_to_inline_plan_sp = std::make_shared<ThreadPlanStepOut>(
88           m_thread, nullptr, false, stop_others, eVoteNoOpinion, eVoteNoOpinion,
89           frame_idx - 1, eLazyBoolNo, continue_to_next_branch);
90       static_cast<ThreadPlanStepOut *>(m_step_out_to_inline_plan_sp.get())
91           ->SetShouldStopHereCallbacks(nullptr, nullptr);
92       m_step_out_to_inline_plan_sp->SetPrivate(true);
93     } else {
94       // If we're already at the inlined frame we're stepping through, then
95       // just do that now.
96       QueueInlinedStepPlan(false);
97     }
98   } else {
99     // Find the return address and set a breakpoint there:
100     // FIXME - can we do this more securely if we know first_insn?
101 
102     Address return_address(return_frame_sp->GetFrameCodeAddress());
103     if (continue_to_next_branch) {
104       SymbolContext return_address_sc;
105       AddressRange range;
106       Address return_address_decr_pc = return_address;
107       if (return_address_decr_pc.GetOffset() > 0)
108         return_address_decr_pc.Slide(-1);
109 
110       return_address_decr_pc.CalculateSymbolContext(
111           &return_address_sc, lldb::eSymbolContextLineEntry);
112       if (return_address_sc.line_entry.IsValid()) {
113         const bool include_inlined_functions = false;
114         range = return_address_sc.line_entry.GetSameLineContiguousAddressRange(
115             include_inlined_functions);
116         if (range.GetByteSize() > 0) {
117           return_address =
118               m_thread.GetProcess()->AdvanceAddressToNextBranchInstruction(
119                   return_address, range);
120         }
121       }
122     }
123     m_return_addr =
124         return_address.GetLoadAddress(&m_thread.GetProcess()->GetTarget());
125 
126     if (m_return_addr == LLDB_INVALID_ADDRESS)
127       return;
128 
129     Breakpoint *return_bp = m_thread.CalculateTarget()
130                                 ->CreateBreakpoint(m_return_addr, true, false)
131                                 .get();
132 
133     if (return_bp != nullptr) {
134       if (return_bp->IsHardware() && !return_bp->HasResolvedLocations())
135         m_could_not_resolve_hw_bp = true;
136       return_bp->SetThreadID(m_thread.GetID());
137       m_return_bp_id = return_bp->GetID();
138       return_bp->SetBreakpointKind("step-out");
139     }
140 
141     if (immediate_return_from_sp) {
142       const SymbolContext &sc =
143           immediate_return_from_sp->GetSymbolContext(eSymbolContextFunction);
144       if (sc.function) {
145         m_immediate_step_from_function = sc.function;
146       }
147     }
148   }
149 }
150 
151 void ThreadPlanStepOut::SetupAvoidNoDebug(
152     LazyBool step_out_avoids_code_without_debug_info) {
153   bool avoid_nodebug = true;
154   switch (step_out_avoids_code_without_debug_info) {
155   case eLazyBoolYes:
156     avoid_nodebug = true;
157     break;
158   case eLazyBoolNo:
159     avoid_nodebug = false;
160     break;
161   case eLazyBoolCalculate:
162     avoid_nodebug = m_thread.GetStepOutAvoidsNoDebug();
163     break;
164   }
165   if (avoid_nodebug)
166     GetFlags().Set(ThreadPlanShouldStopHere::eStepOutAvoidNoDebug);
167   else
168     GetFlags().Clear(ThreadPlanShouldStopHere::eStepOutAvoidNoDebug);
169 }
170 
171 void ThreadPlanStepOut::DidPush() {
172   if (m_step_out_to_inline_plan_sp)
173     m_thread.QueueThreadPlan(m_step_out_to_inline_plan_sp, false);
174   else if (m_step_through_inline_plan_sp)
175     m_thread.QueueThreadPlan(m_step_through_inline_plan_sp, false);
176 }
177 
178 ThreadPlanStepOut::~ThreadPlanStepOut() {
179   if (m_return_bp_id != LLDB_INVALID_BREAK_ID)
180     m_thread.CalculateTarget()->RemoveBreakpointByID(m_return_bp_id);
181 }
182 
183 void ThreadPlanStepOut::GetDescription(Stream *s,
184                                        lldb::DescriptionLevel level) {
185   if (level == lldb::eDescriptionLevelBrief)
186     s->Printf("step out");
187   else {
188     if (m_step_out_to_inline_plan_sp)
189       s->Printf("Stepping out to inlined frame so we can walk through it.");
190     else if (m_step_through_inline_plan_sp)
191       s->Printf("Stepping out by stepping through inlined function.");
192     else {
193       s->Printf("Stepping out from ");
194       Address tmp_address;
195       if (tmp_address.SetLoadAddress(m_step_from_insn, &GetTarget())) {
196         tmp_address.Dump(s, &GetThread(), Address::DumpStyleResolvedDescription,
197                          Address::DumpStyleLoadAddress);
198       } else {
199         s->Printf("address 0x%" PRIx64 "", (uint64_t)m_step_from_insn);
200       }
201 
202       // FIXME: find some useful way to present the m_return_id, since there may
203       // be multiple copies of the
204       // same function on the stack.
205 
206       s->Printf(" returning to frame at ");
207       if (tmp_address.SetLoadAddress(m_return_addr, &GetTarget())) {
208         tmp_address.Dump(s, &GetThread(), Address::DumpStyleResolvedDescription,
209                          Address::DumpStyleLoadAddress);
210       } else {
211         s->Printf("address 0x%" PRIx64 "", (uint64_t)m_return_addr);
212       }
213 
214       if (level == eDescriptionLevelVerbose)
215         s->Printf(" using breakpoint site %d", m_return_bp_id);
216     }
217   }
218 
219   s->Printf("\n");
220   for (StackFrameSP frame_sp : m_stepped_past_frames) {
221     s->Printf("Stepped out past: ");
222     frame_sp->DumpUsingSettingsFormat(s);
223   }
224 }
225 
226 bool ThreadPlanStepOut::ValidatePlan(Stream *error) {
227   if (m_step_out_to_inline_plan_sp)
228     return m_step_out_to_inline_plan_sp->ValidatePlan(error);
229 
230   if (m_step_through_inline_plan_sp)
231     return m_step_through_inline_plan_sp->ValidatePlan(error);
232 
233   if (m_could_not_resolve_hw_bp) {
234     if (error)
235       error->PutCString(
236           "Could not create hardware breakpoint for thread plan.");
237     return false;
238   }
239 
240   if (m_return_bp_id == LLDB_INVALID_BREAK_ID) {
241     if (error)
242       error->PutCString("Could not create return address breakpoint.");
243     return false;
244   }
245 
246   return true;
247 }
248 
249 bool ThreadPlanStepOut::DoPlanExplainsStop(Event *event_ptr) {
250   // If the step out plan is done, then we just need to step through the
251   // inlined frame.
252   if (m_step_out_to_inline_plan_sp) {
253     return m_step_out_to_inline_plan_sp->MischiefManaged();
254   } else if (m_step_through_inline_plan_sp) {
255     if (m_step_through_inline_plan_sp->MischiefManaged()) {
256       CalculateReturnValue();
257       SetPlanComplete();
258       return true;
259     } else
260       return false;
261   } else if (m_step_out_further_plan_sp) {
262     return m_step_out_further_plan_sp->MischiefManaged();
263   }
264 
265   // We don't explain signals or breakpoints (breakpoints that handle stepping
266   // in or out will be handled by a child plan.
267 
268   StopInfoSP stop_info_sp = GetPrivateStopInfo();
269   if (stop_info_sp) {
270     StopReason reason = stop_info_sp->GetStopReason();
271     if (reason == eStopReasonBreakpoint) {
272       // If this is OUR breakpoint, we're fine, otherwise we don't know why
273       // this happened...
274       BreakpointSiteSP site_sp(
275           m_thread.GetProcess()->GetBreakpointSiteList().FindByID(
276               stop_info_sp->GetValue()));
277       if (site_sp && site_sp->IsBreakpointAtThisSite(m_return_bp_id)) {
278         bool done;
279 
280         StackID frame_zero_id = m_thread.GetStackFrameAtIndex(0)->GetStackID();
281 
282         if (m_step_out_to_id == frame_zero_id)
283           done = true;
284         else if (m_step_out_to_id < frame_zero_id) {
285           // Either we stepped past the breakpoint, or the stack ID calculation
286           // was incorrect and we should probably stop.
287           done = true;
288         } else {
289           done = (m_immediate_step_from_id < frame_zero_id);
290         }
291 
292         if (done) {
293           if (InvokeShouldStopHereCallback(eFrameCompareOlder, m_status)) {
294             CalculateReturnValue();
295             SetPlanComplete();
296           }
297         }
298 
299         // If there was only one owner, then we're done.  But if we also hit
300         // some user breakpoint on our way out, we should mark ourselves as
301         // done, but also not claim to explain the stop, since it is more
302         // important to report the user breakpoint than the step out
303         // completion.
304 
305         if (site_sp->GetNumberOfOwners() == 1)
306           return true;
307       }
308       return false;
309     } else if (IsUsuallyUnexplainedStopReason(reason))
310       return false;
311     else
312       return true;
313   }
314   return true;
315 }
316 
317 bool ThreadPlanStepOut::ShouldStop(Event *event_ptr) {
318   if (IsPlanComplete())
319     return true;
320 
321   bool done = false;
322   if (m_step_out_to_inline_plan_sp) {
323     if (m_step_out_to_inline_plan_sp->MischiefManaged()) {
324       // Now step through the inlined stack we are in:
325       if (QueueInlinedStepPlan(true)) {
326         // If we can't queue a plan to do this, then just call ourselves done.
327         m_step_out_to_inline_plan_sp.reset();
328         SetPlanComplete(false);
329         return true;
330       } else
331         done = true;
332     } else
333       return m_step_out_to_inline_plan_sp->ShouldStop(event_ptr);
334   } else if (m_step_through_inline_plan_sp) {
335     if (m_step_through_inline_plan_sp->MischiefManaged())
336       done = true;
337     else
338       return m_step_through_inline_plan_sp->ShouldStop(event_ptr);
339   } else if (m_step_out_further_plan_sp) {
340     if (m_step_out_further_plan_sp->MischiefManaged())
341       m_step_out_further_plan_sp.reset();
342     else
343       return m_step_out_further_plan_sp->ShouldStop(event_ptr);
344   }
345 
346   if (!done) {
347     StackID frame_zero_id = m_thread.GetStackFrameAtIndex(0)->GetStackID();
348     done = !(frame_zero_id < m_step_out_to_id);
349   }
350 
351   // The normal step out computations think we are done, so all we need to do
352   // is consult the ShouldStopHere, and we are done.
353 
354   if (done) {
355     if (InvokeShouldStopHereCallback(eFrameCompareOlder, m_status)) {
356       CalculateReturnValue();
357       SetPlanComplete();
358     } else {
359       m_step_out_further_plan_sp =
360           QueueStepOutFromHerePlan(m_flags, eFrameCompareOlder, m_status);
361       done = false;
362     }
363   }
364 
365   return done;
366 }
367 
368 bool ThreadPlanStepOut::StopOthers() { return m_stop_others; }
369 
370 StateType ThreadPlanStepOut::GetPlanRunState() { return eStateRunning; }
371 
372 bool ThreadPlanStepOut::DoWillResume(StateType resume_state,
373                                      bool current_plan) {
374   if (m_step_out_to_inline_plan_sp || m_step_through_inline_plan_sp)
375     return true;
376 
377   if (m_return_bp_id == LLDB_INVALID_BREAK_ID)
378     return false;
379 
380   if (current_plan) {
381     Breakpoint *return_bp =
382         m_thread.CalculateTarget()->GetBreakpointByID(m_return_bp_id).get();
383     if (return_bp != nullptr)
384       return_bp->SetEnabled(true);
385   }
386   return true;
387 }
388 
389 bool ThreadPlanStepOut::WillStop() {
390   if (m_return_bp_id != LLDB_INVALID_BREAK_ID) {
391     Breakpoint *return_bp =
392         m_thread.CalculateTarget()->GetBreakpointByID(m_return_bp_id).get();
393     if (return_bp != nullptr)
394       return_bp->SetEnabled(false);
395   }
396 
397   return true;
398 }
399 
400 bool ThreadPlanStepOut::MischiefManaged() {
401   if (IsPlanComplete()) {
402     // Did I reach my breakpoint?  If so I'm done.
403     //
404     // I also check the stack depth, since if we've blown past the breakpoint
405     // for some
406     // reason and we're now stopping for some other reason altogether, then
407     // we're done with this step out operation.
408 
409     Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_STEP));
410     if (log)
411       log->Printf("Completed step out plan.");
412     if (m_return_bp_id != LLDB_INVALID_BREAK_ID) {
413       m_thread.CalculateTarget()->RemoveBreakpointByID(m_return_bp_id);
414       m_return_bp_id = LLDB_INVALID_BREAK_ID;
415     }
416 
417     ThreadPlan::MischiefManaged();
418     return true;
419   } else {
420     return false;
421   }
422 }
423 
424 bool ThreadPlanStepOut::QueueInlinedStepPlan(bool queue_now) {
425   // Now figure out the range of this inlined block, and set up a "step through
426   // range" plan for that.  If we've been provided with a context, then use the
427   // block in that context.
428   StackFrameSP immediate_return_from_sp(m_thread.GetStackFrameAtIndex(0));
429   if (!immediate_return_from_sp)
430     return false;
431 
432   Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_STEP));
433   if (log) {
434     StreamString s;
435     immediate_return_from_sp->Dump(&s, true, false);
436     log->Printf("Queuing inlined frame to step past: %s.", s.GetData());
437   }
438 
439   Block *from_block = immediate_return_from_sp->GetFrameBlock();
440   if (from_block) {
441     Block *inlined_block = from_block->GetContainingInlinedBlock();
442     if (inlined_block) {
443       size_t num_ranges = inlined_block->GetNumRanges();
444       AddressRange inline_range;
445       if (inlined_block->GetRangeAtIndex(0, inline_range)) {
446         SymbolContext inlined_sc;
447         inlined_block->CalculateSymbolContext(&inlined_sc);
448         inlined_sc.target_sp = GetTarget().shared_from_this();
449         RunMode run_mode =
450             m_stop_others ? lldb::eOnlyThisThread : lldb::eAllThreads;
451         const LazyBool avoid_no_debug = eLazyBoolNo;
452 
453         m_step_through_inline_plan_sp =
454             std::make_shared<ThreadPlanStepOverRange>(
455                 m_thread, inline_range, inlined_sc, run_mode, avoid_no_debug);
456         ThreadPlanStepOverRange *step_through_inline_plan_ptr =
457             static_cast<ThreadPlanStepOverRange *>(
458                 m_step_through_inline_plan_sp.get());
459         m_step_through_inline_plan_sp->SetPrivate(true);
460 
461         step_through_inline_plan_ptr->SetOkayToDiscard(true);
462         StreamString errors;
463         if (!step_through_inline_plan_ptr->ValidatePlan(&errors)) {
464           // FIXME: Log this failure.
465           delete step_through_inline_plan_ptr;
466           return false;
467         }
468 
469         for (size_t i = 1; i < num_ranges; i++) {
470           if (inlined_block->GetRangeAtIndex(i, inline_range))
471             step_through_inline_plan_ptr->AddRange(inline_range);
472         }
473 
474         if (queue_now)
475           m_thread.QueueThreadPlan(m_step_through_inline_plan_sp, false);
476         return true;
477       }
478     }
479   }
480 
481   return false;
482 }
483 
484 void ThreadPlanStepOut::CalculateReturnValue() {
485   if (m_return_valobj_sp)
486     return;
487 
488   if (!m_calculate_return_value)
489     return;
490 
491   if (m_immediate_step_from_function != nullptr) {
492     CompilerType return_compiler_type =
493         m_immediate_step_from_function->GetCompilerType()
494             .GetFunctionReturnType();
495     if (return_compiler_type) {
496       lldb::ABISP abi_sp = m_thread.GetProcess()->GetABI();
497       if (abi_sp)
498         m_return_valobj_sp =
499             abi_sp->GetReturnValueObject(m_thread, return_compiler_type);
500     }
501   }
502 }
503 
504 bool ThreadPlanStepOut::IsPlanStale() {
505   // If we are still lower on the stack than the frame we are returning to,
506   // then there's something for us to do.  Otherwise, we're stale.
507 
508   StackID frame_zero_id = m_thread.GetStackFrameAtIndex(0)->GetStackID();
509   return !(frame_zero_id < m_step_out_to_id);
510 }
511