1 //===-- ThreadPlanStepOut.cpp ---------------------------------------------===//
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 report_stop_vote, Vote report_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, report_stop_vote,
40                  report_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 = thread.GetRegisterContext()->GetPC(0);
51 
52   uint32_t return_frame_index = frame_idx + 1;
53   StackFrameSP return_frame_sp(thread.GetStackFrameAtIndex(return_frame_index));
54   StackFrameSP immediate_return_from_sp(thread.GetStackFrameAtIndex(frame_idx));
55 
56   if (!return_frame_sp || !immediate_return_from_sp)
57     return; // we can't do anything here.  ValidatePlan() will return false.
58 
59   // While stepping out, behave as-if artificial frames are not present.
60   while (return_frame_sp->IsArtificial()) {
61     m_stepped_past_frames.push_back(return_frame_sp);
62 
63     ++return_frame_index;
64     return_frame_sp = thread.GetStackFrameAtIndex(return_frame_index);
65 
66     // We never expect to see an artificial frame without a regular ancestor.
67     // If this happens, log the issue and defensively refuse to step out.
68     if (!return_frame_sp) {
69       LLDB_LOG(log, "Can't step out of frame with artificial ancestors");
70       return;
71     }
72   }
73 
74   m_step_out_to_id = return_frame_sp->GetStackID();
75   m_immediate_step_from_id = immediate_return_from_sp->GetStackID();
76 
77   // If the frame directly below the one we are returning to is inlined, we
78   // have to be a little more careful.  It is non-trivial to determine the real
79   // "return code address" for an inlined frame, so we have to work our way to
80   // that frame and then step out.
81   if (immediate_return_from_sp->IsInlined()) {
82     if (frame_idx > 0) {
83       // First queue a plan that gets us to this inlined frame, and when we get
84       // there we'll queue a second plan that walks us out of this frame.
85       m_step_out_to_inline_plan_sp = std::make_shared<ThreadPlanStepOut>(
86           thread, nullptr, false, stop_others, eVoteNoOpinion, eVoteNoOpinion,
87           frame_idx - 1, eLazyBoolNo, continue_to_next_branch);
88       static_cast<ThreadPlanStepOut *>(m_step_out_to_inline_plan_sp.get())
89           ->SetShouldStopHereCallbacks(nullptr, nullptr);
90       m_step_out_to_inline_plan_sp->SetPrivate(true);
91     } else {
92       // If we're already at the inlined frame we're stepping through, then
93       // just do that now.
94       QueueInlinedStepPlan(false);
95     }
96   } else {
97     // Find the return address and set a breakpoint there:
98     // FIXME - can we do this more securely if we know first_insn?
99 
100     Address return_address(return_frame_sp->GetFrameCodeAddress());
101     if (continue_to_next_branch) {
102       SymbolContext return_address_sc;
103       AddressRange range;
104       Address return_address_decr_pc = return_address;
105       if (return_address_decr_pc.GetOffset() > 0)
106         return_address_decr_pc.Slide(-1);
107 
108       return_address_decr_pc.CalculateSymbolContext(
109           &return_address_sc, lldb::eSymbolContextLineEntry);
110       if (return_address_sc.line_entry.IsValid()) {
111         const bool include_inlined_functions = false;
112         range = return_address_sc.line_entry.GetSameLineContiguousAddressRange(
113             include_inlined_functions);
114         if (range.GetByteSize() > 0) {
115           return_address = m_process.AdvanceAddressToNextBranchInstruction(
116               return_address, range);
117         }
118       }
119     }
120     m_return_addr = return_address.GetLoadAddress(&m_process.GetTarget());
121 
122     if (m_return_addr == LLDB_INVALID_ADDRESS)
123       return;
124 
125     // Perform some additional validation on the return address.
126     uint32_t permissions = 0;
127     if (!m_process.GetLoadAddressPermissions(m_return_addr, permissions)) {
128       LLDB_LOGF(log, "ThreadPlanStepOut(%p): Return address (0x%" PRIx64
129                 ") permissions not found.", static_cast<void *>(this),
130                 m_return_addr);
131     } else if (!(permissions & ePermissionsExecutable)) {
132       m_constructor_errors.Printf("Return address (0x%" PRIx64
133                                   ") did not point to executable memory.",
134                                   m_return_addr);
135       LLDB_LOGF(log, "ThreadPlanStepOut(%p): %s", static_cast<void *>(this),
136                 m_constructor_errors.GetData());
137       return;
138     }
139 
140     Breakpoint *return_bp =
141         GetTarget().CreateBreakpoint(m_return_addr, true, false).get();
142 
143     if (return_bp != nullptr) {
144       if (return_bp->IsHardware() && !return_bp->HasResolvedLocations())
145         m_could_not_resolve_hw_bp = true;
146       return_bp->SetThreadID(m_tid);
147       m_return_bp_id = return_bp->GetID();
148       return_bp->SetBreakpointKind("step-out");
149     }
150 
151     if (immediate_return_from_sp) {
152       const SymbolContext &sc =
153           immediate_return_from_sp->GetSymbolContext(eSymbolContextFunction);
154       if (sc.function) {
155         m_immediate_step_from_function = sc.function;
156       }
157     }
158   }
159 }
160 
161 void ThreadPlanStepOut::SetupAvoidNoDebug(
162     LazyBool step_out_avoids_code_without_debug_info) {
163   bool avoid_nodebug = true;
164   switch (step_out_avoids_code_without_debug_info) {
165   case eLazyBoolYes:
166     avoid_nodebug = true;
167     break;
168   case eLazyBoolNo:
169     avoid_nodebug = false;
170     break;
171   case eLazyBoolCalculate:
172     avoid_nodebug = GetThread().GetStepOutAvoidsNoDebug();
173     break;
174   }
175   if (avoid_nodebug)
176     GetFlags().Set(ThreadPlanShouldStopHere::eStepOutAvoidNoDebug);
177   else
178     GetFlags().Clear(ThreadPlanShouldStopHere::eStepOutAvoidNoDebug);
179 }
180 
181 void ThreadPlanStepOut::DidPush() {
182   Thread &thread = GetThread();
183   if (m_step_out_to_inline_plan_sp)
184     thread.QueueThreadPlan(m_step_out_to_inline_plan_sp, false);
185   else if (m_step_through_inline_plan_sp)
186     thread.QueueThreadPlan(m_step_through_inline_plan_sp, false);
187 }
188 
189 ThreadPlanStepOut::~ThreadPlanStepOut() {
190   if (m_return_bp_id != LLDB_INVALID_BREAK_ID)
191     GetTarget().RemoveBreakpointByID(m_return_bp_id);
192 }
193 
194 void ThreadPlanStepOut::GetDescription(Stream *s,
195                                        lldb::DescriptionLevel level) {
196   if (level == lldb::eDescriptionLevelBrief)
197     s->Printf("step out");
198   else {
199     if (m_step_out_to_inline_plan_sp)
200       s->Printf("Stepping out to inlined frame so we can walk through it.");
201     else if (m_step_through_inline_plan_sp)
202       s->Printf("Stepping out by stepping through inlined function.");
203     else {
204       s->Printf("Stepping out from ");
205       Address tmp_address;
206       if (tmp_address.SetLoadAddress(m_step_from_insn, &GetTarget())) {
207         tmp_address.Dump(s, &m_process, Address::DumpStyleResolvedDescription,
208                          Address::DumpStyleLoadAddress);
209       } else {
210         s->Printf("address 0x%" PRIx64 "", (uint64_t)m_step_from_insn);
211       }
212 
213       // FIXME: find some useful way to present the m_return_id, since there may
214       // be multiple copies of the
215       // same function on the stack.
216 
217       s->Printf(" returning to frame at ");
218       if (tmp_address.SetLoadAddress(m_return_addr, &GetTarget())) {
219         tmp_address.Dump(s, &m_process, Address::DumpStyleResolvedDescription,
220                          Address::DumpStyleLoadAddress);
221       } else {
222         s->Printf("address 0x%" PRIx64 "", (uint64_t)m_return_addr);
223       }
224 
225       if (level == eDescriptionLevelVerbose)
226         s->Printf(" using breakpoint site %d", m_return_bp_id);
227     }
228   }
229 
230   if (m_stepped_past_frames.empty())
231     return;
232 
233   s->Printf("\n");
234   for (StackFrameSP frame_sp : m_stepped_past_frames) {
235     s->Printf("Stepped out past: ");
236     frame_sp->DumpUsingSettingsFormat(s);
237   }
238 }
239 
240 bool ThreadPlanStepOut::ValidatePlan(Stream *error) {
241   if (m_step_out_to_inline_plan_sp)
242     return m_step_out_to_inline_plan_sp->ValidatePlan(error);
243 
244   if (m_step_through_inline_plan_sp)
245     return m_step_through_inline_plan_sp->ValidatePlan(error);
246 
247   if (m_could_not_resolve_hw_bp) {
248     if (error)
249       error->PutCString(
250           "Could not create hardware breakpoint for thread plan.");
251     return false;
252   }
253 
254   if (m_return_bp_id == LLDB_INVALID_BREAK_ID) {
255     if (error) {
256       error->PutCString("Could not create return address breakpoint.");
257       if (m_constructor_errors.GetSize() > 0) {
258         error->PutCString(" ");
259         error->PutCString(m_constructor_errors.GetString());
260       }
261     }
262     return false;
263   }
264 
265   return true;
266 }
267 
268 bool ThreadPlanStepOut::DoPlanExplainsStop(Event *event_ptr) {
269   // If the step out plan is done, then we just need to step through the
270   // inlined frame.
271   if (m_step_out_to_inline_plan_sp) {
272     return m_step_out_to_inline_plan_sp->MischiefManaged();
273   } else if (m_step_through_inline_plan_sp) {
274     if (m_step_through_inline_plan_sp->MischiefManaged()) {
275       CalculateReturnValue();
276       SetPlanComplete();
277       return true;
278     } else
279       return false;
280   } else if (m_step_out_further_plan_sp) {
281     return m_step_out_further_plan_sp->MischiefManaged();
282   }
283 
284   // We don't explain signals or breakpoints (breakpoints that handle stepping
285   // in or out will be handled by a child plan.
286 
287   StopInfoSP stop_info_sp = GetPrivateStopInfo();
288   if (stop_info_sp) {
289     StopReason reason = stop_info_sp->GetStopReason();
290     if (reason == eStopReasonBreakpoint) {
291       // If this is OUR breakpoint, we're fine, otherwise we don't know why
292       // this happened...
293       BreakpointSiteSP site_sp(
294           m_process.GetBreakpointSiteList().FindByID(stop_info_sp->GetValue()));
295       if (site_sp && site_sp->IsBreakpointAtThisSite(m_return_bp_id)) {
296         bool done;
297 
298         StackID frame_zero_id =
299             GetThread().GetStackFrameAtIndex(0)->GetStackID();
300 
301         if (m_step_out_to_id == frame_zero_id)
302           done = true;
303         else if (m_step_out_to_id < frame_zero_id) {
304           // Either we stepped past the breakpoint, or the stack ID calculation
305           // was incorrect and we should probably stop.
306           done = true;
307         } else {
308           done = (m_immediate_step_from_id < frame_zero_id);
309         }
310 
311         if (done) {
312           if (InvokeShouldStopHereCallback(eFrameCompareOlder, m_status)) {
313             CalculateReturnValue();
314             SetPlanComplete();
315           }
316         }
317 
318         // If there was only one owner, then we're done.  But if we also hit
319         // some user breakpoint on our way out, we should mark ourselves as
320         // done, but also not claim to explain the stop, since it is more
321         // important to report the user breakpoint than the step out
322         // completion.
323 
324         if (site_sp->GetNumberOfOwners() == 1)
325           return true;
326       }
327       return false;
328     } else if (IsUsuallyUnexplainedStopReason(reason))
329       return false;
330     else
331       return true;
332   }
333   return true;
334 }
335 
336 bool ThreadPlanStepOut::ShouldStop(Event *event_ptr) {
337   if (IsPlanComplete())
338     return true;
339 
340   bool done = false;
341   if (m_step_out_to_inline_plan_sp) {
342     if (m_step_out_to_inline_plan_sp->MischiefManaged()) {
343       // Now step through the inlined stack we are in:
344       if (QueueInlinedStepPlan(true)) {
345         // If we can't queue a plan to do this, then just call ourselves done.
346         m_step_out_to_inline_plan_sp.reset();
347         SetPlanComplete(false);
348         return true;
349       } else
350         done = true;
351     } else
352       return m_step_out_to_inline_plan_sp->ShouldStop(event_ptr);
353   } else if (m_step_through_inline_plan_sp) {
354     if (m_step_through_inline_plan_sp->MischiefManaged())
355       done = true;
356     else
357       return m_step_through_inline_plan_sp->ShouldStop(event_ptr);
358   } else if (m_step_out_further_plan_sp) {
359     if (m_step_out_further_plan_sp->MischiefManaged())
360       m_step_out_further_plan_sp.reset();
361     else
362       return m_step_out_further_plan_sp->ShouldStop(event_ptr);
363   }
364 
365   if (!done) {
366     StackID frame_zero_id = GetThread().GetStackFrameAtIndex(0)->GetStackID();
367     done = !(frame_zero_id < m_step_out_to_id);
368   }
369 
370   // The normal step out computations think we are done, so all we need to do
371   // is consult the ShouldStopHere, and we are done.
372 
373   if (done) {
374     if (InvokeShouldStopHereCallback(eFrameCompareOlder, m_status)) {
375       CalculateReturnValue();
376       SetPlanComplete();
377     } else {
378       m_step_out_further_plan_sp =
379           QueueStepOutFromHerePlan(m_flags, eFrameCompareOlder, m_status);
380       done = false;
381     }
382   }
383 
384   return done;
385 }
386 
387 bool ThreadPlanStepOut::StopOthers() { return m_stop_others; }
388 
389 StateType ThreadPlanStepOut::GetPlanRunState() { return eStateRunning; }
390 
391 bool ThreadPlanStepOut::DoWillResume(StateType resume_state,
392                                      bool current_plan) {
393   if (m_step_out_to_inline_plan_sp || m_step_through_inline_plan_sp)
394     return true;
395 
396   if (m_return_bp_id == LLDB_INVALID_BREAK_ID)
397     return false;
398 
399   if (current_plan) {
400     Breakpoint *return_bp = GetTarget().GetBreakpointByID(m_return_bp_id).get();
401     if (return_bp != nullptr)
402       return_bp->SetEnabled(true);
403   }
404   return true;
405 }
406 
407 bool ThreadPlanStepOut::WillStop() {
408   if (m_return_bp_id != LLDB_INVALID_BREAK_ID) {
409     Breakpoint *return_bp = GetTarget().GetBreakpointByID(m_return_bp_id).get();
410     if (return_bp != nullptr)
411       return_bp->SetEnabled(false);
412   }
413 
414   return true;
415 }
416 
417 bool ThreadPlanStepOut::MischiefManaged() {
418   if (IsPlanComplete()) {
419     // Did I reach my breakpoint?  If so I'm done.
420     //
421     // I also check the stack depth, since if we've blown past the breakpoint
422     // for some
423     // reason and we're now stopping for some other reason altogether, then
424     // we're done with this step out operation.
425 
426     Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_STEP));
427     if (log)
428       LLDB_LOGF(log, "Completed step out plan.");
429     if (m_return_bp_id != LLDB_INVALID_BREAK_ID) {
430       GetTarget().RemoveBreakpointByID(m_return_bp_id);
431       m_return_bp_id = LLDB_INVALID_BREAK_ID;
432     }
433 
434     ThreadPlan::MischiefManaged();
435     return true;
436   } else {
437     return false;
438   }
439 }
440 
441 bool ThreadPlanStepOut::QueueInlinedStepPlan(bool queue_now) {
442   // Now figure out the range of this inlined block, and set up a "step through
443   // range" plan for that.  If we've been provided with a context, then use the
444   // block in that context.
445   Thread &thread = GetThread();
446   StackFrameSP immediate_return_from_sp(thread.GetStackFrameAtIndex(0));
447   if (!immediate_return_from_sp)
448     return false;
449 
450   Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_STEP));
451   if (log) {
452     StreamString s;
453     immediate_return_from_sp->Dump(&s, true, false);
454     LLDB_LOGF(log, "Queuing inlined frame to step past: %s.", s.GetData());
455   }
456 
457   Block *from_block = immediate_return_from_sp->GetFrameBlock();
458   if (from_block) {
459     Block *inlined_block = from_block->GetContainingInlinedBlock();
460     if (inlined_block) {
461       size_t num_ranges = inlined_block->GetNumRanges();
462       AddressRange inline_range;
463       if (inlined_block->GetRangeAtIndex(0, inline_range)) {
464         SymbolContext inlined_sc;
465         inlined_block->CalculateSymbolContext(&inlined_sc);
466         inlined_sc.target_sp = GetTarget().shared_from_this();
467         RunMode run_mode =
468             m_stop_others ? lldb::eOnlyThisThread : lldb::eAllThreads;
469         const LazyBool avoid_no_debug = eLazyBoolNo;
470 
471         m_step_through_inline_plan_sp =
472             std::make_shared<ThreadPlanStepOverRange>(
473                 thread, inline_range, inlined_sc, run_mode, avoid_no_debug);
474         ThreadPlanStepOverRange *step_through_inline_plan_ptr =
475             static_cast<ThreadPlanStepOverRange *>(
476                 m_step_through_inline_plan_sp.get());
477         m_step_through_inline_plan_sp->SetPrivate(true);
478 
479         step_through_inline_plan_ptr->SetOkayToDiscard(true);
480         StreamString errors;
481         if (!step_through_inline_plan_ptr->ValidatePlan(&errors)) {
482           // FIXME: Log this failure.
483           delete step_through_inline_plan_ptr;
484           return false;
485         }
486 
487         for (size_t i = 1; i < num_ranges; i++) {
488           if (inlined_block->GetRangeAtIndex(i, inline_range))
489             step_through_inline_plan_ptr->AddRange(inline_range);
490         }
491 
492         if (queue_now)
493           thread.QueueThreadPlan(m_step_through_inline_plan_sp, false);
494         return true;
495       }
496     }
497   }
498 
499   return false;
500 }
501 
502 void ThreadPlanStepOut::CalculateReturnValue() {
503   if (m_return_valobj_sp)
504     return;
505 
506   if (!m_calculate_return_value)
507     return;
508 
509   if (m_immediate_step_from_function != nullptr) {
510     CompilerType return_compiler_type =
511         m_immediate_step_from_function->GetCompilerType()
512             .GetFunctionReturnType();
513     if (return_compiler_type) {
514       lldb::ABISP abi_sp = m_process.GetABI();
515       if (abi_sp)
516         m_return_valobj_sp =
517             abi_sp->GetReturnValueObject(GetThread(), return_compiler_type);
518     }
519   }
520 }
521 
522 bool ThreadPlanStepOut::IsPlanStale() {
523   // If we are still lower on the stack than the frame we are returning to,
524   // then there's something for us to do.  Otherwise, we're stale.
525 
526   StackID frame_zero_id = GetThread().GetStackFrameAtIndex(0)->GetStackID();
527   return !(frame_zero_id < m_step_out_to_id);
528 }
529