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/CPPLanguageRuntime.h"
12 #include "lldb/Target/DynamicLoader.h"
13 #include "lldb/Target/ObjCLanguageRuntime.h"
14 #include "lldb/Target/Process.h"
15 #include "lldb/Target/RegisterContext.h"
16 #include "lldb/Target/Target.h"
17 #include "lldb/Utility/Log.h"
18 #include "lldb/Utility/Stream.h"
19 
20 using namespace lldb;
21 using namespace lldb_private;
22 
23 //----------------------------------------------------------------------
24 // ThreadPlanStepThrough: If the current instruction is a trampoline, step
25 // through it If it is the beginning of the prologue of a function, step
26 // through that as well.
27 // FIXME: At present only handles DYLD trampolines.
28 //----------------------------------------------------------------------
29 
30 ThreadPlanStepThrough::ThreadPlanStepThrough(Thread &thread,
31                                              StackID &m_stack_id,
32                                              bool stop_others)
33     : ThreadPlan(ThreadPlan::eKindStepThrough,
34                  "Step through trampolines and prologues", thread,
35                  eVoteNoOpinion, eVoteNoOpinion),
36       m_start_address(0), m_backstop_bkpt_id(LLDB_INVALID_BREAK_ID),
37       m_backstop_addr(LLDB_INVALID_ADDRESS), m_return_stack_id(m_stack_id),
38       m_stop_others(stop_others) {
39   LookForPlanToStepThroughFromCurrentPC();
40 
41   // If we don't get a valid step through plan, don't bother to set up a
42   // backstop.
43   if (m_sub_plan_sp) {
44     m_start_address = GetThread().GetRegisterContext()->GetPC(0);
45 
46     // We are going to return back to the concrete frame 1, we might pass by
47     // some inlined code that we're in the middle of by doing this, but it's
48     // easier than trying to figure out where the inlined code might return to.
49 
50     StackFrameSP return_frame_sp = m_thread.GetFrameWithStackID(m_stack_id);
51 
52     if (return_frame_sp) {
53       m_backstop_addr = return_frame_sp->GetFrameCodeAddress().GetLoadAddress(
54           m_thread.CalculateTarget().get());
55       Breakpoint *return_bp =
56           m_thread.GetProcess()
57               ->GetTarget()
58               .CreateBreakpoint(m_backstop_addr, true, false)
59               .get();
60 
61       if (return_bp != nullptr) {
62         if (return_bp->IsHardware() && !return_bp->HasResolvedLocations())
63           m_could_not_resolve_hw_bp = true;
64         return_bp->SetThreadID(m_thread.GetID());
65         m_backstop_bkpt_id = return_bp->GetID();
66         return_bp->SetBreakpointKind("step-through-backstop");
67       }
68       Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_STEP));
69       if (log) {
70         log->Printf("Setting backstop breakpoint %d at address: 0x%" PRIx64,
71                     m_backstop_bkpt_id, m_backstop_addr);
72       }
73     }
74   }
75 }
76 
77 ThreadPlanStepThrough::~ThreadPlanStepThrough() { ClearBackstopBreakpoint(); }
78 
79 void ThreadPlanStepThrough::DidPush() {
80   if (m_sub_plan_sp)
81     PushPlan(m_sub_plan_sp);
82 }
83 
84 void ThreadPlanStepThrough::LookForPlanToStepThroughFromCurrentPC() {
85   DynamicLoader *loader = m_thread.GetProcess()->GetDynamicLoader();
86   if (loader)
87     m_sub_plan_sp =
88         loader->GetStepThroughTrampolinePlan(m_thread, m_stop_others);
89 
90   // If that didn't come up with anything, try the ObjC runtime plugin:
91   if (!m_sub_plan_sp.get()) {
92     ObjCLanguageRuntime *objc_runtime =
93         m_thread.GetProcess()->GetObjCLanguageRuntime();
94     if (objc_runtime)
95       m_sub_plan_sp =
96           objc_runtime->GetStepThroughTrampolinePlan(m_thread, m_stop_others);
97 
98     CPPLanguageRuntime *cpp_runtime =
99         m_thread.GetProcess()->GetCPPLanguageRuntime();
100 
101     // If the ObjC runtime did not provide us with a step though plan then if we
102     // have it check the C++ runtime for a step though plan.
103     if (!m_sub_plan_sp.get() && cpp_runtime)
104       m_sub_plan_sp =
105           cpp_runtime->GetStepThroughTrampolinePlan(m_thread, m_stop_others);
106   }
107 
108   Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_STEP));
109   if (log) {
110     lldb::addr_t current_address = GetThread().GetRegisterContext()->GetPC(0);
111     if (m_sub_plan_sp) {
112       StreamString s;
113       m_sub_plan_sp->GetDescription(&s, lldb::eDescriptionLevelFull);
114       log->Printf("Found step through plan from 0x%" PRIx64 ": %s",
115                   current_address, s.GetData());
116     } else {
117       log->Printf("Couldn't find step through plan from address 0x%" PRIx64 ".",
118                   current_address);
119     }
120   }
121 }
122 
123 void ThreadPlanStepThrough::GetDescription(Stream *s,
124                                            lldb::DescriptionLevel level) {
125   if (level == lldb::eDescriptionLevelBrief)
126     s->Printf("Step through");
127   else {
128     s->PutCString("Stepping through trampoline code from: ");
129     s->Address(m_start_address, sizeof(addr_t));
130     if (m_backstop_bkpt_id != LLDB_INVALID_BREAK_ID) {
131       s->Printf(" with backstop breakpoint ID: %d at address: ",
132                 m_backstop_bkpt_id);
133       s->Address(m_backstop_addr, sizeof(addr_t));
134     } else
135       s->PutCString(" unable to set a backstop breakpoint.");
136   }
137 }
138 
139 bool ThreadPlanStepThrough::ValidatePlan(Stream *error) {
140   if (m_could_not_resolve_hw_bp) {
141     if (error)
142       error->PutCString(
143           "Could not create hardware breakpoint for thread plan.");
144     return false;
145   }
146 
147   if (m_backstop_bkpt_id == LLDB_INVALID_BREAK_ID) {
148     if (error)
149       error->PutCString("Could not create backstop breakpoint.");
150     return false;
151   }
152 
153   if (!m_sub_plan_sp.get()) {
154     if (error)
155       error->PutCString("Does not have a subplan.");
156     return false;
157   }
158 
159   return true;
160 }
161 
162 bool ThreadPlanStepThrough::DoPlanExplainsStop(Event *event_ptr) {
163   // If we have a sub-plan, it will have been asked first if we explain the
164   // stop, and we won't get asked.  The only time we would be the one directly
165   // asked this question is if we hit our backstop breakpoint.
166 
167   return HitOurBackstopBreakpoint();
168 }
169 
170 bool ThreadPlanStepThrough::ShouldStop(Event *event_ptr) {
171   // If we've already marked ourselves done, then we're done...
172   if (IsPlanComplete())
173     return true;
174 
175   // First, did we hit the backstop breakpoint?
176   if (HitOurBackstopBreakpoint()) {
177     SetPlanComplete(true);
178     return true;
179   }
180 
181   // If we don't have a sub-plan, then we're also done (can't see how we would
182   // ever get here without a plan, but just in case.
183 
184   if (!m_sub_plan_sp) {
185     SetPlanComplete();
186     return true;
187   }
188 
189   // If the current sub plan is not done, we don't want to stop.  Actually, we
190   // probably won't ever get here in this state, since we generally won't get
191   // asked any questions if out current sub-plan is not done...
192   if (!m_sub_plan_sp->IsPlanComplete())
193     return false;
194 
195   // If our current sub plan failed, then let's just run to our backstop.  If
196   // we can't do that then just stop.
197   if (!m_sub_plan_sp->PlanSucceeded()) {
198     if (m_backstop_bkpt_id != LLDB_INVALID_BREAK_ID) {
199       m_sub_plan_sp.reset();
200       return false;
201     } else {
202       SetPlanComplete(false);
203       return true;
204     }
205   }
206 
207   // Next see if there is a specific step through plan at our current pc (these
208   // might chain, for instance stepping through a dylib trampoline to the objc
209   // dispatch function...)
210   LookForPlanToStepThroughFromCurrentPC();
211   if (m_sub_plan_sp) {
212     PushPlan(m_sub_plan_sp);
213     return false;
214   } else {
215     SetPlanComplete();
216     return true;
217   }
218 }
219 
220 bool ThreadPlanStepThrough::StopOthers() { return m_stop_others; }
221 
222 StateType ThreadPlanStepThrough::GetPlanRunState() { return eStateRunning; }
223 
224 bool ThreadPlanStepThrough::DoWillResume(StateType resume_state,
225                                          bool current_plan) {
226   return true;
227 }
228 
229 bool ThreadPlanStepThrough::WillStop() { return true; }
230 
231 void ThreadPlanStepThrough::ClearBackstopBreakpoint() {
232   if (m_backstop_bkpt_id != LLDB_INVALID_BREAK_ID) {
233     m_thread.GetProcess()->GetTarget().RemoveBreakpointByID(m_backstop_bkpt_id);
234     m_backstop_bkpt_id = LLDB_INVALID_BREAK_ID;
235     m_could_not_resolve_hw_bp = false;
236   }
237 }
238 
239 bool ThreadPlanStepThrough::MischiefManaged() {
240   Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_STEP));
241 
242   if (!IsPlanComplete()) {
243     return false;
244   } else {
245     if (log)
246       log->Printf("Completed step through step plan.");
247 
248     ClearBackstopBreakpoint();
249     ThreadPlan::MischiefManaged();
250     return true;
251   }
252 }
253 
254 bool ThreadPlanStepThrough::HitOurBackstopBreakpoint() {
255   StopInfoSP stop_info_sp(m_thread.GetStopInfo());
256   if (stop_info_sp && stop_info_sp->GetStopReason() == eStopReasonBreakpoint) {
257     break_id_t stop_value = (break_id_t)stop_info_sp->GetValue();
258     BreakpointSiteSP cur_site_sp =
259         m_thread.GetProcess()->GetBreakpointSiteList().FindByID(stop_value);
260     if (cur_site_sp &&
261         cur_site_sp->IsBreakpointAtThisSite(m_backstop_bkpt_id)) {
262       StackID cur_frame_zero_id =
263           m_thread.GetStackFrameAtIndex(0)->GetStackID();
264 
265       if (cur_frame_zero_id == m_return_stack_id) {
266         Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_STEP));
267         if (log)
268           log->PutCString("ThreadPlanStepThrough hit backstop breakpoint.");
269         return true;
270       }
271     }
272   }
273   return false;
274 }
275