1 //===-- ThreadPlanStepThrough.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/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 = m_thread.GetFrameWithStackID(m_stack_id);
48 
49     if (return_frame_sp) {
50       m_backstop_addr = return_frame_sp->GetFrameCodeAddress().GetLoadAddress(
51           m_thread.CalculateTarget().get());
52       Breakpoint *return_bp =
53           m_thread.GetProcess()
54               ->GetTarget()
55               .CreateBreakpoint(m_backstop_addr, true, false)
56               .get();
57 
58       if (return_bp != nullptr) {
59         if (return_bp->IsHardware() && !return_bp->HasResolvedLocations())
60           m_could_not_resolve_hw_bp = true;
61         return_bp->SetThreadID(m_thread.GetID());
62         m_backstop_bkpt_id = return_bp->GetID();
63         return_bp->SetBreakpointKind("step-through-backstop");
64       }
65       Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_STEP));
66       if (log) {
67         LLDB_LOGF(log, "Setting backstop breakpoint %d at address: 0x%" PRIx64,
68                   m_backstop_bkpt_id, m_backstop_addr);
69       }
70     }
71   }
72 }
73 
74 ThreadPlanStepThrough::~ThreadPlanStepThrough() { ClearBackstopBreakpoint(); }
75 
76 void ThreadPlanStepThrough::DidPush() {
77   if (m_sub_plan_sp)
78     PushPlan(m_sub_plan_sp);
79 }
80 
81 void ThreadPlanStepThrough::LookForPlanToStepThroughFromCurrentPC() {
82   DynamicLoader *loader = m_thread.GetProcess()->GetDynamicLoader();
83   if (loader)
84     m_sub_plan_sp =
85         loader->GetStepThroughTrampolinePlan(m_thread, m_stop_others);
86 
87   // If the DynamicLoader was unable to provide us with a ThreadPlan, then we
88   // try the LanguageRuntimes.
89   if (!m_sub_plan_sp) {
90     for (LanguageRuntime *runtime :
91          m_thread.GetProcess()->GetLanguageRuntimes()) {
92       m_sub_plan_sp =
93           runtime->GetStepThroughTrampolinePlan(m_thread, m_stop_others);
94 
95       if (m_sub_plan_sp)
96         break;
97     }
98   }
99 
100   Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_STEP));
101   if (log) {
102     lldb::addr_t current_address = GetThread().GetRegisterContext()->GetPC(0);
103     if (m_sub_plan_sp) {
104       StreamString s;
105       m_sub_plan_sp->GetDescription(&s, lldb::eDescriptionLevelFull);
106       LLDB_LOGF(log, "Found step through plan from 0x%" PRIx64 ": %s",
107                 current_address, s.GetData());
108     } else {
109       LLDB_LOGF(log,
110                 "Couldn't find step through plan from address 0x%" PRIx64 ".",
111                 current_address);
112     }
113   }
114 }
115 
116 void ThreadPlanStepThrough::GetDescription(Stream *s,
117                                            lldb::DescriptionLevel level) {
118   if (level == lldb::eDescriptionLevelBrief)
119     s->Printf("Step through");
120   else {
121     s->PutCString("Stepping through trampoline code from: ");
122     DumpAddress(s->AsRawOstream(), m_start_address, sizeof(addr_t));
123     if (m_backstop_bkpt_id != LLDB_INVALID_BREAK_ID) {
124       s->Printf(" with backstop breakpoint ID: %d at address: ",
125                 m_backstop_bkpt_id);
126       DumpAddress(s->AsRawOstream(), m_backstop_addr, sizeof(addr_t));
127     } else
128       s->PutCString(" unable to set a backstop breakpoint.");
129   }
130 }
131 
132 bool ThreadPlanStepThrough::ValidatePlan(Stream *error) {
133   if (m_could_not_resolve_hw_bp) {
134     if (error)
135       error->PutCString(
136           "Could not create hardware breakpoint for thread plan.");
137     return false;
138   }
139 
140   if (m_backstop_bkpt_id == LLDB_INVALID_BREAK_ID) {
141     if (error)
142       error->PutCString("Could not create backstop breakpoint.");
143     return false;
144   }
145 
146   if (!m_sub_plan_sp.get()) {
147     if (error)
148       error->PutCString("Does not have a subplan.");
149     return false;
150   }
151 
152   return true;
153 }
154 
155 bool ThreadPlanStepThrough::DoPlanExplainsStop(Event *event_ptr) {
156   // If we have a sub-plan, it will have been asked first if we explain the
157   // stop, and we won't get asked.  The only time we would be the one directly
158   // asked this question is if we hit our backstop breakpoint.
159 
160   return HitOurBackstopBreakpoint();
161 }
162 
163 bool ThreadPlanStepThrough::ShouldStop(Event *event_ptr) {
164   // If we've already marked ourselves done, then we're done...
165   if (IsPlanComplete())
166     return true;
167 
168   // First, did we hit the backstop breakpoint?
169   if (HitOurBackstopBreakpoint()) {
170     SetPlanComplete(true);
171     return true;
172   }
173 
174   // If we don't have a sub-plan, then we're also done (can't see how we would
175   // ever get here without a plan, but just in case.
176 
177   if (!m_sub_plan_sp) {
178     SetPlanComplete();
179     return true;
180   }
181 
182   // If the current sub plan is not done, we don't want to stop.  Actually, we
183   // probably won't ever get here in this state, since we generally won't get
184   // asked any questions if out current sub-plan is not done...
185   if (!m_sub_plan_sp->IsPlanComplete())
186     return false;
187 
188   // If our current sub plan failed, then let's just run to our backstop.  If
189   // we can't do that then just stop.
190   if (!m_sub_plan_sp->PlanSucceeded()) {
191     if (m_backstop_bkpt_id != LLDB_INVALID_BREAK_ID) {
192       m_sub_plan_sp.reset();
193       return false;
194     } else {
195       SetPlanComplete(false);
196       return true;
197     }
198   }
199 
200   // Next see if there is a specific step through plan at our current pc (these
201   // might chain, for instance stepping through a dylib trampoline to the objc
202   // dispatch function...)
203   LookForPlanToStepThroughFromCurrentPC();
204   if (m_sub_plan_sp) {
205     PushPlan(m_sub_plan_sp);
206     return false;
207   } else {
208     SetPlanComplete();
209     return true;
210   }
211 }
212 
213 bool ThreadPlanStepThrough::StopOthers() { return m_stop_others; }
214 
215 StateType ThreadPlanStepThrough::GetPlanRunState() { return eStateRunning; }
216 
217 bool ThreadPlanStepThrough::DoWillResume(StateType resume_state,
218                                          bool current_plan) {
219   return true;
220 }
221 
222 bool ThreadPlanStepThrough::WillStop() { return true; }
223 
224 void ThreadPlanStepThrough::ClearBackstopBreakpoint() {
225   if (m_backstop_bkpt_id != LLDB_INVALID_BREAK_ID) {
226     m_thread.GetProcess()->GetTarget().RemoveBreakpointByID(m_backstop_bkpt_id);
227     m_backstop_bkpt_id = LLDB_INVALID_BREAK_ID;
228     m_could_not_resolve_hw_bp = false;
229   }
230 }
231 
232 bool ThreadPlanStepThrough::MischiefManaged() {
233   Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_STEP));
234 
235   if (!IsPlanComplete()) {
236     return false;
237   } else {
238     LLDB_LOGF(log, "Completed step through step plan.");
239 
240     ClearBackstopBreakpoint();
241     ThreadPlan::MischiefManaged();
242     return true;
243   }
244 }
245 
246 bool ThreadPlanStepThrough::HitOurBackstopBreakpoint() {
247   StopInfoSP stop_info_sp(m_thread.GetStopInfo());
248   if (stop_info_sp && stop_info_sp->GetStopReason() == eStopReasonBreakpoint) {
249     break_id_t stop_value = (break_id_t)stop_info_sp->GetValue();
250     BreakpointSiteSP cur_site_sp =
251         m_thread.GetProcess()->GetBreakpointSiteList().FindByID(stop_value);
252     if (cur_site_sp &&
253         cur_site_sp->IsBreakpointAtThisSite(m_backstop_bkpt_id)) {
254       StackID cur_frame_zero_id =
255           m_thread.GetStackFrameAtIndex(0)->GetStackID();
256 
257       if (cur_frame_zero_id == m_return_stack_id) {
258         Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_STEP));
259         if (log)
260           log->PutCString("ThreadPlanStepThrough hit backstop breakpoint.");
261         return true;
262       }
263     }
264   }
265   return false;
266 }
267