1 //===-- ThreadPlanStepThrough.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/ThreadPlanStepThrough.h"
10 #include "lldb/Breakpoint/Breakpoint.h"
11 #include "lldb/Target/DynamicLoader.h"
12 #include "lldb/Target/LanguageRuntime.h"
13 #include "lldb/Target/Process.h"
14 #include "lldb/Target/RegisterContext.h"
15 #include "lldb/Target/Target.h"
16 #include "lldb/Utility/Log.h"
17 #include "lldb/Utility/Stream.h"
18 
19 using namespace lldb;
20 using namespace lldb_private;
21 
22 // ThreadPlanStepThrough: If the current instruction is a trampoline, step
23 // through it If it is the beginning of the prologue of a function, step
24 // through that as well.
25 // FIXME: At present only handles DYLD trampolines.
26 
27 ThreadPlanStepThrough::ThreadPlanStepThrough(Thread &thread,
28                                              StackID &m_stack_id,
29                                              bool stop_others)
30     : ThreadPlan(ThreadPlan::eKindStepThrough,
31                  "Step through trampolines and prologues", thread,
32                  eVoteNoOpinion, eVoteNoOpinion),
33       m_start_address(0), m_backstop_bkpt_id(LLDB_INVALID_BREAK_ID),
34       m_backstop_addr(LLDB_INVALID_ADDRESS), m_return_stack_id(m_stack_id),
35       m_stop_others(stop_others) {
36   LookForPlanToStepThroughFromCurrentPC();
37 
38   // If we don't get a valid step through plan, don't bother to set up a
39   // backstop.
40   if (m_sub_plan_sp) {
41     m_start_address = GetThread().GetRegisterContext()->GetPC(0);
42 
43     // We are going to return back to the concrete frame 1, we might pass by
44     // some inlined code that we're in the middle of by doing this, but it's
45     // easier than trying to figure out where the inlined code might return to.
46 
47     StackFrameSP return_frame_sp = thread.GetFrameWithStackID(m_stack_id);
48 
49     if (return_frame_sp) {
50       m_backstop_addr = return_frame_sp->GetFrameCodeAddress().GetLoadAddress(
51           thread.CalculateTarget().get());
52       Breakpoint *return_bp =
53           m_process.GetTarget()
54               .CreateBreakpoint(m_backstop_addr, true, false)
55               .get();
56 
57       if (return_bp != nullptr) {
58         if (return_bp->IsHardware() && !return_bp->HasResolvedLocations())
59           m_could_not_resolve_hw_bp = true;
60         return_bp->SetThreadID(m_tid);
61         m_backstop_bkpt_id = return_bp->GetID();
62         return_bp->SetBreakpointKind("step-through-backstop");
63       }
64       Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_STEP));
65       if (log) {
66         LLDB_LOGF(log, "Setting backstop breakpoint %d at address: 0x%" PRIx64,
67                   m_backstop_bkpt_id, m_backstop_addr);
68       }
69     }
70   }
71 }
72 
73 ThreadPlanStepThrough::~ThreadPlanStepThrough() { ClearBackstopBreakpoint(); }
74 
75 void ThreadPlanStepThrough::DidPush() {
76   if (m_sub_plan_sp)
77     PushPlan(m_sub_plan_sp);
78 }
79 
80 void ThreadPlanStepThrough::LookForPlanToStepThroughFromCurrentPC() {
81   Thread &thread = GetThread();
82   DynamicLoader *loader = thread.GetProcess()->GetDynamicLoader();
83   if (loader)
84     m_sub_plan_sp = loader->GetStepThroughTrampolinePlan(thread, m_stop_others);
85 
86   // If the DynamicLoader was unable to provide us with a ThreadPlan, then we
87   // try the LanguageRuntimes.
88   if (!m_sub_plan_sp) {
89     for (LanguageRuntime *runtime : m_process.GetLanguageRuntimes()) {
90       m_sub_plan_sp =
91           runtime->GetStepThroughTrampolinePlan(thread, m_stop_others);
92 
93       if (m_sub_plan_sp)
94         break;
95     }
96   }
97 
98   Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_STEP));
99   if (log) {
100     lldb::addr_t current_address = GetThread().GetRegisterContext()->GetPC(0);
101     if (m_sub_plan_sp) {
102       StreamString s;
103       m_sub_plan_sp->GetDescription(&s, lldb::eDescriptionLevelFull);
104       LLDB_LOGF(log, "Found step through plan from 0x%" PRIx64 ": %s",
105                 current_address, s.GetData());
106     } else {
107       LLDB_LOGF(log,
108                 "Couldn't find step through plan from address 0x%" PRIx64 ".",
109                 current_address);
110     }
111   }
112 }
113 
114 void ThreadPlanStepThrough::GetDescription(Stream *s,
115                                            lldb::DescriptionLevel level) {
116   if (level == lldb::eDescriptionLevelBrief)
117     s->Printf("Step through");
118   else {
119     s->PutCString("Stepping through trampoline code from: ");
120     DumpAddress(s->AsRawOstream(), m_start_address, sizeof(addr_t));
121     if (m_backstop_bkpt_id != LLDB_INVALID_BREAK_ID) {
122       s->Printf(" with backstop breakpoint ID: %d at address: ",
123                 m_backstop_bkpt_id);
124       DumpAddress(s->AsRawOstream(), m_backstop_addr, sizeof(addr_t));
125     } else
126       s->PutCString(" unable to set a backstop breakpoint.");
127   }
128 }
129 
130 bool ThreadPlanStepThrough::ValidatePlan(Stream *error) {
131   if (m_could_not_resolve_hw_bp) {
132     if (error)
133       error->PutCString(
134           "Could not create hardware breakpoint for thread plan.");
135     return false;
136   }
137 
138   if (m_backstop_bkpt_id == LLDB_INVALID_BREAK_ID) {
139     if (error)
140       error->PutCString("Could not create backstop breakpoint.");
141     return false;
142   }
143 
144   if (!m_sub_plan_sp.get()) {
145     if (error)
146       error->PutCString("Does not have a subplan.");
147     return false;
148   }
149 
150   return true;
151 }
152 
153 bool ThreadPlanStepThrough::DoPlanExplainsStop(Event *event_ptr) {
154   // If we have a sub-plan, it will have been asked first if we explain the
155   // stop, and we won't get asked.  The only time we would be the one directly
156   // asked this question is if we hit our backstop breakpoint.
157 
158   return HitOurBackstopBreakpoint();
159 }
160 
161 bool ThreadPlanStepThrough::ShouldStop(Event *event_ptr) {
162   // If we've already marked ourselves done, then we're done...
163   if (IsPlanComplete())
164     return true;
165 
166   // First, did we hit the backstop breakpoint?
167   if (HitOurBackstopBreakpoint()) {
168     SetPlanComplete(true);
169     return true;
170   }
171 
172   // If we don't have a sub-plan, then we're also done (can't see how we would
173   // ever get here without a plan, but just in case.
174 
175   if (!m_sub_plan_sp) {
176     SetPlanComplete();
177     return true;
178   }
179 
180   // If the current sub plan is not done, we don't want to stop.  Actually, we
181   // probably won't ever get here in this state, since we generally won't get
182   // asked any questions if out current sub-plan is not done...
183   if (!m_sub_plan_sp->IsPlanComplete())
184     return false;
185 
186   // If our current sub plan failed, then let's just run to our backstop.  If
187   // we can't do that then just stop.
188   if (!m_sub_plan_sp->PlanSucceeded()) {
189     if (m_backstop_bkpt_id != LLDB_INVALID_BREAK_ID) {
190       m_sub_plan_sp.reset();
191       return false;
192     } else {
193       SetPlanComplete(false);
194       return true;
195     }
196   }
197 
198   // Next see if there is a specific step through plan at our current pc (these
199   // might chain, for instance stepping through a dylib trampoline to the objc
200   // dispatch function...)
201   LookForPlanToStepThroughFromCurrentPC();
202   if (m_sub_plan_sp) {
203     PushPlan(m_sub_plan_sp);
204     return false;
205   } else {
206     SetPlanComplete();
207     return true;
208   }
209 }
210 
211 bool ThreadPlanStepThrough::StopOthers() { return m_stop_others; }
212 
213 StateType ThreadPlanStepThrough::GetPlanRunState() { return eStateRunning; }
214 
215 bool ThreadPlanStepThrough::DoWillResume(StateType resume_state,
216                                          bool current_plan) {
217   return true;
218 }
219 
220 bool ThreadPlanStepThrough::WillStop() { return true; }
221 
222 void ThreadPlanStepThrough::ClearBackstopBreakpoint() {
223   if (m_backstop_bkpt_id != LLDB_INVALID_BREAK_ID) {
224     m_process.GetTarget().RemoveBreakpointByID(m_backstop_bkpt_id);
225     m_backstop_bkpt_id = LLDB_INVALID_BREAK_ID;
226     m_could_not_resolve_hw_bp = false;
227   }
228 }
229 
230 bool ThreadPlanStepThrough::MischiefManaged() {
231   Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_STEP));
232 
233   if (!IsPlanComplete()) {
234     return false;
235   } else {
236     LLDB_LOGF(log, "Completed step through step plan.");
237 
238     ClearBackstopBreakpoint();
239     ThreadPlan::MischiefManaged();
240     return true;
241   }
242 }
243 
244 bool ThreadPlanStepThrough::HitOurBackstopBreakpoint() {
245   Thread &thread = GetThread();
246   StopInfoSP stop_info_sp(thread.GetStopInfo());
247   if (stop_info_sp && stop_info_sp->GetStopReason() == eStopReasonBreakpoint) {
248     break_id_t stop_value = (break_id_t)stop_info_sp->GetValue();
249     BreakpointSiteSP cur_site_sp =
250         m_process.GetBreakpointSiteList().FindByID(stop_value);
251     if (cur_site_sp &&
252         cur_site_sp->IsBreakpointAtThisSite(m_backstop_bkpt_id)) {
253       StackID cur_frame_zero_id = thread.GetStackFrameAtIndex(0)->GetStackID();
254 
255       if (cur_frame_zero_id == m_return_stack_id) {
256         Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_STEP));
257         if (log)
258           log->PutCString("ThreadPlanStepThrough hit backstop breakpoint.");
259         return true;
260       }
261     }
262   }
263   return false;
264 }
265