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     // Perform some additional validation on the return address.
130     uint32_t permissions = 0;
131     if (!m_thread.GetProcess()->GetLoadAddressPermissions(m_return_addr,
132                                                           permissions)) {
133       m_constructor_errors.Printf("Return address (0x%" PRIx64
134                                   ") permissions not found.",
135                                   m_return_addr);
136       LLDB_LOGF(log, "ThreadPlanStepOut(%p): %s", static_cast<void *>(this),
137                 m_constructor_errors.GetData());
138       return;
139     } else if (!(permissions & ePermissionsExecutable)) {
140       m_constructor_errors.Printf("Return address (0x%" PRIx64
141                                   ") did not point to executable memory.",
142                                   m_return_addr);
143       LLDB_LOGF(log, "ThreadPlanStepOut(%p): %s", static_cast<void *>(this),
144                 m_constructor_errors.GetData());
145       return;
146     }
147 
148     Breakpoint *return_bp = m_thread.CalculateTarget()
149                                 ->CreateBreakpoint(m_return_addr, true, false)
150                                 .get();
151 
152     if (return_bp != nullptr) {
153       if (return_bp->IsHardware() && !return_bp->HasResolvedLocations())
154         m_could_not_resolve_hw_bp = true;
155       return_bp->SetThreadID(m_thread.GetID());
156       m_return_bp_id = return_bp->GetID();
157       return_bp->SetBreakpointKind("step-out");
158     }
159 
160     if (immediate_return_from_sp) {
161       const SymbolContext &sc =
162           immediate_return_from_sp->GetSymbolContext(eSymbolContextFunction);
163       if (sc.function) {
164         m_immediate_step_from_function = sc.function;
165       }
166     }
167   }
168 }
169 
170 void ThreadPlanStepOut::SetupAvoidNoDebug(
171     LazyBool step_out_avoids_code_without_debug_info) {
172   bool avoid_nodebug = true;
173   switch (step_out_avoids_code_without_debug_info) {
174   case eLazyBoolYes:
175     avoid_nodebug = true;
176     break;
177   case eLazyBoolNo:
178     avoid_nodebug = false;
179     break;
180   case eLazyBoolCalculate:
181     avoid_nodebug = m_thread.GetStepOutAvoidsNoDebug();
182     break;
183   }
184   if (avoid_nodebug)
185     GetFlags().Set(ThreadPlanShouldStopHere::eStepOutAvoidNoDebug);
186   else
187     GetFlags().Clear(ThreadPlanShouldStopHere::eStepOutAvoidNoDebug);
188 }
189 
190 void ThreadPlanStepOut::DidPush() {
191   if (m_step_out_to_inline_plan_sp)
192     m_thread.QueueThreadPlan(m_step_out_to_inline_plan_sp, false);
193   else if (m_step_through_inline_plan_sp)
194     m_thread.QueueThreadPlan(m_step_through_inline_plan_sp, false);
195 }
196 
197 ThreadPlanStepOut::~ThreadPlanStepOut() {
198   if (m_return_bp_id != LLDB_INVALID_BREAK_ID)
199     m_thread.CalculateTarget()->RemoveBreakpointByID(m_return_bp_id);
200 }
201 
202 void ThreadPlanStepOut::GetDescription(Stream *s,
203                                        lldb::DescriptionLevel level) {
204   if (level == lldb::eDescriptionLevelBrief)
205     s->Printf("step out");
206   else {
207     if (m_step_out_to_inline_plan_sp)
208       s->Printf("Stepping out to inlined frame so we can walk through it.");
209     else if (m_step_through_inline_plan_sp)
210       s->Printf("Stepping out by stepping through inlined function.");
211     else {
212       s->Printf("Stepping out from ");
213       Address tmp_address;
214       if (tmp_address.SetLoadAddress(m_step_from_insn, &GetTarget())) {
215         tmp_address.Dump(s, &GetThread(), Address::DumpStyleResolvedDescription,
216                          Address::DumpStyleLoadAddress);
217       } else {
218         s->Printf("address 0x%" PRIx64 "", (uint64_t)m_step_from_insn);
219       }
220 
221       // FIXME: find some useful way to present the m_return_id, since there may
222       // be multiple copies of the
223       // same function on the stack.
224 
225       s->Printf(" returning to frame at ");
226       if (tmp_address.SetLoadAddress(m_return_addr, &GetTarget())) {
227         tmp_address.Dump(s, &GetThread(), Address::DumpStyleResolvedDescription,
228                          Address::DumpStyleLoadAddress);
229       } else {
230         s->Printf("address 0x%" PRIx64 "", (uint64_t)m_return_addr);
231       }
232 
233       if (level == eDescriptionLevelVerbose)
234         s->Printf(" using breakpoint site %d", m_return_bp_id);
235     }
236   }
237 
238   s->Printf("\n");
239   for (StackFrameSP frame_sp : m_stepped_past_frames) {
240     s->Printf("Stepped out past: ");
241     frame_sp->DumpUsingSettingsFormat(s);
242   }
243 }
244 
245 bool ThreadPlanStepOut::ValidatePlan(Stream *error) {
246   if (m_step_out_to_inline_plan_sp)
247     return m_step_out_to_inline_plan_sp->ValidatePlan(error);
248 
249   if (m_step_through_inline_plan_sp)
250     return m_step_through_inline_plan_sp->ValidatePlan(error);
251 
252   if (m_could_not_resolve_hw_bp) {
253     if (error)
254       error->PutCString(
255           "Could not create hardware breakpoint for thread plan.");
256     return false;
257   }
258 
259   if (m_return_bp_id == LLDB_INVALID_BREAK_ID) {
260     if (error) {
261       error->PutCString("Could not create return address breakpoint.");
262       if (m_constructor_errors.GetSize() > 0) {
263         error->PutCString(" ");
264         error->PutCString(m_constructor_errors.GetString());
265       }
266     }
267     return false;
268   }
269 
270   return true;
271 }
272 
273 bool ThreadPlanStepOut::DoPlanExplainsStop(Event *event_ptr) {
274   // If the step out plan is done, then we just need to step through the
275   // inlined frame.
276   if (m_step_out_to_inline_plan_sp) {
277     return m_step_out_to_inline_plan_sp->MischiefManaged();
278   } else if (m_step_through_inline_plan_sp) {
279     if (m_step_through_inline_plan_sp->MischiefManaged()) {
280       CalculateReturnValue();
281       SetPlanComplete();
282       return true;
283     } else
284       return false;
285   } else if (m_step_out_further_plan_sp) {
286     return m_step_out_further_plan_sp->MischiefManaged();
287   }
288 
289   // We don't explain signals or breakpoints (breakpoints that handle stepping
290   // in or out will be handled by a child plan.
291 
292   StopInfoSP stop_info_sp = GetPrivateStopInfo();
293   if (stop_info_sp) {
294     StopReason reason = stop_info_sp->GetStopReason();
295     if (reason == eStopReasonBreakpoint) {
296       // If this is OUR breakpoint, we're fine, otherwise we don't know why
297       // this happened...
298       BreakpointSiteSP site_sp(
299           m_thread.GetProcess()->GetBreakpointSiteList().FindByID(
300               stop_info_sp->GetValue()));
301       if (site_sp && site_sp->IsBreakpointAtThisSite(m_return_bp_id)) {
302         bool done;
303 
304         StackID frame_zero_id = m_thread.GetStackFrameAtIndex(0)->GetStackID();
305 
306         if (m_step_out_to_id == frame_zero_id)
307           done = true;
308         else if (m_step_out_to_id < frame_zero_id) {
309           // Either we stepped past the breakpoint, or the stack ID calculation
310           // was incorrect and we should probably stop.
311           done = true;
312         } else {
313           done = (m_immediate_step_from_id < frame_zero_id);
314         }
315 
316         if (done) {
317           if (InvokeShouldStopHereCallback(eFrameCompareOlder, m_status)) {
318             CalculateReturnValue();
319             SetPlanComplete();
320           }
321         }
322 
323         // If there was only one owner, then we're done.  But if we also hit
324         // some user breakpoint on our way out, we should mark ourselves as
325         // done, but also not claim to explain the stop, since it is more
326         // important to report the user breakpoint than the step out
327         // completion.
328 
329         if (site_sp->GetNumberOfOwners() == 1)
330           return true;
331       }
332       return false;
333     } else if (IsUsuallyUnexplainedStopReason(reason))
334       return false;
335     else
336       return true;
337   }
338   return true;
339 }
340 
341 bool ThreadPlanStepOut::ShouldStop(Event *event_ptr) {
342   if (IsPlanComplete())
343     return true;
344 
345   bool done = false;
346   if (m_step_out_to_inline_plan_sp) {
347     if (m_step_out_to_inline_plan_sp->MischiefManaged()) {
348       // Now step through the inlined stack we are in:
349       if (QueueInlinedStepPlan(true)) {
350         // If we can't queue a plan to do this, then just call ourselves done.
351         m_step_out_to_inline_plan_sp.reset();
352         SetPlanComplete(false);
353         return true;
354       } else
355         done = true;
356     } else
357       return m_step_out_to_inline_plan_sp->ShouldStop(event_ptr);
358   } else if (m_step_through_inline_plan_sp) {
359     if (m_step_through_inline_plan_sp->MischiefManaged())
360       done = true;
361     else
362       return m_step_through_inline_plan_sp->ShouldStop(event_ptr);
363   } else if (m_step_out_further_plan_sp) {
364     if (m_step_out_further_plan_sp->MischiefManaged())
365       m_step_out_further_plan_sp.reset();
366     else
367       return m_step_out_further_plan_sp->ShouldStop(event_ptr);
368   }
369 
370   if (!done) {
371     StackID frame_zero_id = m_thread.GetStackFrameAtIndex(0)->GetStackID();
372     done = !(frame_zero_id < m_step_out_to_id);
373   }
374 
375   // The normal step out computations think we are done, so all we need to do
376   // is consult the ShouldStopHere, and we are done.
377 
378   if (done) {
379     if (InvokeShouldStopHereCallback(eFrameCompareOlder, m_status)) {
380       CalculateReturnValue();
381       SetPlanComplete();
382     } else {
383       m_step_out_further_plan_sp =
384           QueueStepOutFromHerePlan(m_flags, eFrameCompareOlder, m_status);
385       done = false;
386     }
387   }
388 
389   return done;
390 }
391 
392 bool ThreadPlanStepOut::StopOthers() { return m_stop_others; }
393 
394 StateType ThreadPlanStepOut::GetPlanRunState() { return eStateRunning; }
395 
396 bool ThreadPlanStepOut::DoWillResume(StateType resume_state,
397                                      bool current_plan) {
398   if (m_step_out_to_inline_plan_sp || m_step_through_inline_plan_sp)
399     return true;
400 
401   if (m_return_bp_id == LLDB_INVALID_BREAK_ID)
402     return false;
403 
404   if (current_plan) {
405     Breakpoint *return_bp =
406         m_thread.CalculateTarget()->GetBreakpointByID(m_return_bp_id).get();
407     if (return_bp != nullptr)
408       return_bp->SetEnabled(true);
409   }
410   return true;
411 }
412 
413 bool ThreadPlanStepOut::WillStop() {
414   if (m_return_bp_id != LLDB_INVALID_BREAK_ID) {
415     Breakpoint *return_bp =
416         m_thread.CalculateTarget()->GetBreakpointByID(m_return_bp_id).get();
417     if (return_bp != nullptr)
418       return_bp->SetEnabled(false);
419   }
420 
421   return true;
422 }
423 
424 bool ThreadPlanStepOut::MischiefManaged() {
425   if (IsPlanComplete()) {
426     // Did I reach my breakpoint?  If so I'm done.
427     //
428     // I also check the stack depth, since if we've blown past the breakpoint
429     // for some
430     // reason and we're now stopping for some other reason altogether, then
431     // we're done with this step out operation.
432 
433     Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_STEP));
434     if (log)
435       LLDB_LOGF(log, "Completed step out plan.");
436     if (m_return_bp_id != LLDB_INVALID_BREAK_ID) {
437       m_thread.CalculateTarget()->RemoveBreakpointByID(m_return_bp_id);
438       m_return_bp_id = LLDB_INVALID_BREAK_ID;
439     }
440 
441     ThreadPlan::MischiefManaged();
442     return true;
443   } else {
444     return false;
445   }
446 }
447 
448 bool ThreadPlanStepOut::QueueInlinedStepPlan(bool queue_now) {
449   // Now figure out the range of this inlined block, and set up a "step through
450   // range" plan for that.  If we've been provided with a context, then use the
451   // block in that context.
452   StackFrameSP immediate_return_from_sp(m_thread.GetStackFrameAtIndex(0));
453   if (!immediate_return_from_sp)
454     return false;
455 
456   Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_STEP));
457   if (log) {
458     StreamString s;
459     immediate_return_from_sp->Dump(&s, true, false);
460     LLDB_LOGF(log, "Queuing inlined frame to step past: %s.", s.GetData());
461   }
462 
463   Block *from_block = immediate_return_from_sp->GetFrameBlock();
464   if (from_block) {
465     Block *inlined_block = from_block->GetContainingInlinedBlock();
466     if (inlined_block) {
467       size_t num_ranges = inlined_block->GetNumRanges();
468       AddressRange inline_range;
469       if (inlined_block->GetRangeAtIndex(0, inline_range)) {
470         SymbolContext inlined_sc;
471         inlined_block->CalculateSymbolContext(&inlined_sc);
472         inlined_sc.target_sp = GetTarget().shared_from_this();
473         RunMode run_mode =
474             m_stop_others ? lldb::eOnlyThisThread : lldb::eAllThreads;
475         const LazyBool avoid_no_debug = eLazyBoolNo;
476 
477         m_step_through_inline_plan_sp =
478             std::make_shared<ThreadPlanStepOverRange>(
479                 m_thread, inline_range, inlined_sc, run_mode, avoid_no_debug);
480         ThreadPlanStepOverRange *step_through_inline_plan_ptr =
481             static_cast<ThreadPlanStepOverRange *>(
482                 m_step_through_inline_plan_sp.get());
483         m_step_through_inline_plan_sp->SetPrivate(true);
484 
485         step_through_inline_plan_ptr->SetOkayToDiscard(true);
486         StreamString errors;
487         if (!step_through_inline_plan_ptr->ValidatePlan(&errors)) {
488           // FIXME: Log this failure.
489           delete step_through_inline_plan_ptr;
490           return false;
491         }
492 
493         for (size_t i = 1; i < num_ranges; i++) {
494           if (inlined_block->GetRangeAtIndex(i, inline_range))
495             step_through_inline_plan_ptr->AddRange(inline_range);
496         }
497 
498         if (queue_now)
499           m_thread.QueueThreadPlan(m_step_through_inline_plan_sp, false);
500         return true;
501       }
502     }
503   }
504 
505   return false;
506 }
507 
508 void ThreadPlanStepOut::CalculateReturnValue() {
509   if (m_return_valobj_sp)
510     return;
511 
512   if (!m_calculate_return_value)
513     return;
514 
515   if (m_immediate_step_from_function != nullptr) {
516     CompilerType return_compiler_type =
517         m_immediate_step_from_function->GetCompilerType()
518             .GetFunctionReturnType();
519     if (return_compiler_type) {
520       lldb::ABISP abi_sp = m_thread.GetProcess()->GetABI();
521       if (abi_sp)
522         m_return_valobj_sp =
523             abi_sp->GetReturnValueObject(m_thread, return_compiler_type);
524     }
525   }
526 }
527 
528 bool ThreadPlanStepOut::IsPlanStale() {
529   // If we are still lower on the stack than the frame we are returning to,
530   // then there's something for us to do.  Otherwise, we're stale.
531 
532   StackID frame_zero_id = m_thread.GetStackFrameAtIndex(0)->GetStackID();
533   return !(frame_zero_id < m_step_out_to_id);
534 }
535