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1 /*
2  * Copyright (C) 2017 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #define _GNU_SOURCE 1
18 #include <elf.h>
19 #include <inttypes.h>
20 #include <stdint.h>
21 #include <string.h>
22 #include <sys/types.h>
23 #include <unistd.h>
24 
25 #include <algorithm>
26 
27 #include <android-base/stringprintf.h>
28 #include <android-base/strings.h>
29 
30 #include <demangle.h>
31 
32 #include <unwindstack/Elf.h>
33 #include <unwindstack/JitDebug.h>
34 #include <unwindstack/MapInfo.h>
35 #include <unwindstack/Maps.h>
36 #include <unwindstack/Memory.h>
37 #include <unwindstack/Unwinder.h>
38 
39 #if !defined(NO_LIBDEXFILE_SUPPORT)
40 #include <unwindstack/DexFiles.h>
41 #endif
42 
43 namespace unwindstack {
44 
45 // Inject extra 'virtual' frame that represents the dex pc data.
46 // The dex pc is a magic register defined in the Mterp interpreter,
47 // and thus it will be restored/observed in the frame after it.
48 // Adding the dex frame first here will create something like:
49 //   #7 pc 0015fa20 core.vdex   java.util.Arrays.binarySearch+8
50 //   #8 pc 006b1ba1 libartd.so  ExecuteMterpImpl+14625
51 //   #9 pc 0039a1ef libartd.so  art::interpreter::Execute+719
FillInDexFrame()52 void Unwinder::FillInDexFrame() {
53   size_t frame_num = frames_.size();
54   frames_.resize(frame_num + 1);
55   FrameData* frame = &frames_.at(frame_num);
56   frame->num = frame_num;
57 
58   uint64_t dex_pc = regs_->dex_pc();
59   frame->pc = dex_pc;
60   frame->sp = regs_->sp();
61 
62   MapInfo* info = maps_->Find(dex_pc);
63   if (info != nullptr) {
64     frame->map_start = info->start;
65     frame->map_end = info->end;
66     frame->map_elf_start_offset = info->elf_start_offset;
67     frame->map_exact_offset = info->offset;
68     frame->map_load_bias = info->load_bias;
69     frame->map_flags = info->flags;
70     if (resolve_names_) {
71       frame->map_name = info->name;
72     }
73     frame->rel_pc = dex_pc - info->start;
74   } else {
75     frame->rel_pc = dex_pc;
76     return;
77   }
78 
79   if (!resolve_names_) {
80     return;
81   }
82 
83 #if !defined(NO_LIBDEXFILE_SUPPORT)
84   if (dex_files_ == nullptr) {
85     return;
86   }
87 
88   dex_files_->GetMethodInformation(maps_, info, dex_pc, &frame->function_name,
89                                    &frame->function_offset);
90 #endif
91 }
92 
FillInFrame(MapInfo * map_info,Elf * elf,uint64_t rel_pc,uint64_t pc_adjustment)93 FrameData* Unwinder::FillInFrame(MapInfo* map_info, Elf* elf, uint64_t rel_pc,
94                                  uint64_t pc_adjustment) {
95   size_t frame_num = frames_.size();
96   frames_.resize(frame_num + 1);
97   FrameData* frame = &frames_.at(frame_num);
98   frame->num = frame_num;
99   frame->sp = regs_->sp();
100   frame->rel_pc = rel_pc - pc_adjustment;
101   frame->pc = regs_->pc() - pc_adjustment;
102 
103   if (map_info == nullptr) {
104     // Nothing else to update.
105     return nullptr;
106   }
107 
108   if (resolve_names_) {
109     frame->map_name = map_info->name;
110     if (embedded_soname_ && map_info->elf_start_offset != 0 && !frame->map_name.empty()) {
111       std::string soname = elf->GetSoname();
112       if (!soname.empty()) {
113         frame->map_name += '!' + soname;
114       }
115     }
116   }
117   frame->map_elf_start_offset = map_info->elf_start_offset;
118   frame->map_exact_offset = map_info->offset;
119   frame->map_start = map_info->start;
120   frame->map_end = map_info->end;
121   frame->map_flags = map_info->flags;
122   frame->map_load_bias = elf->GetLoadBias();
123   return frame;
124 }
125 
ShouldStop(const std::vector<std::string> * map_suffixes_to_ignore,std::string & map_name)126 static bool ShouldStop(const std::vector<std::string>* map_suffixes_to_ignore,
127                        std::string& map_name) {
128   if (map_suffixes_to_ignore == nullptr) {
129     return false;
130   }
131   auto pos = map_name.find_last_of('.');
132   if (pos == std::string::npos) {
133     return false;
134   }
135 
136   return std::find(map_suffixes_to_ignore->begin(), map_suffixes_to_ignore->end(),
137                    map_name.substr(pos + 1)) != map_suffixes_to_ignore->end();
138 }
139 
Unwind(const std::vector<std::string> * initial_map_names_to_skip,const std::vector<std::string> * map_suffixes_to_ignore)140 void Unwinder::Unwind(const std::vector<std::string>* initial_map_names_to_skip,
141                       const std::vector<std::string>* map_suffixes_to_ignore) {
142   frames_.clear();
143   last_error_.code = ERROR_NONE;
144   last_error_.address = 0;
145   elf_from_memory_not_file_ = false;
146 
147   ArchEnum arch = regs_->Arch();
148 
149   bool return_address_attempt = false;
150   bool adjust_pc = false;
151   for (; frames_.size() < max_frames_;) {
152     uint64_t cur_pc = regs_->pc();
153     uint64_t cur_sp = regs_->sp();
154 
155     MapInfo* map_info = maps_->Find(regs_->pc());
156     uint64_t pc_adjustment = 0;
157     uint64_t step_pc;
158     uint64_t rel_pc;
159     Elf* elf;
160     if (map_info == nullptr) {
161       step_pc = regs_->pc();
162       rel_pc = step_pc;
163       last_error_.code = ERROR_INVALID_MAP;
164     } else {
165       if (ShouldStop(map_suffixes_to_ignore, map_info->name)) {
166         break;
167       }
168       elf = map_info->GetElf(process_memory_, arch);
169       // If this elf is memory backed, and there is a valid file, then set
170       // an indicator that we couldn't open the file.
171       if (!elf_from_memory_not_file_ && map_info->memory_backed_elf && !map_info->name.empty() &&
172           map_info->name[0] != '[' && !android::base::StartsWith(map_info->name, "/memfd:")) {
173         elf_from_memory_not_file_ = true;
174       }
175       step_pc = regs_->pc();
176       rel_pc = elf->GetRelPc(step_pc, map_info);
177       // Everyone except elf data in gdb jit debug maps uses the relative pc.
178       if (!(map_info->flags & MAPS_FLAGS_JIT_SYMFILE_MAP)) {
179         step_pc = rel_pc;
180       }
181       if (adjust_pc) {
182         pc_adjustment = regs_->GetPcAdjustment(rel_pc, elf);
183       } else {
184         pc_adjustment = 0;
185       }
186       step_pc -= pc_adjustment;
187 
188       // If the pc is in an invalid elf file, try and get an Elf object
189       // using the jit debug information.
190       if (!elf->valid() && jit_debug_ != nullptr) {
191         uint64_t adjusted_jit_pc = regs_->pc() - pc_adjustment;
192         Elf* jit_elf = jit_debug_->GetElf(maps_, adjusted_jit_pc);
193         if (jit_elf != nullptr) {
194           // The jit debug information requires a non relative adjusted pc.
195           step_pc = adjusted_jit_pc;
196           elf = jit_elf;
197         }
198       }
199     }
200 
201     FrameData* frame = nullptr;
202     if (map_info == nullptr || initial_map_names_to_skip == nullptr ||
203         std::find(initial_map_names_to_skip->begin(), initial_map_names_to_skip->end(),
204                   basename(map_info->name.c_str())) == initial_map_names_to_skip->end()) {
205       if (regs_->dex_pc() != 0) {
206         // Add a frame to represent the dex file.
207         FillInDexFrame();
208         // Clear the dex pc so that we don't repeat this frame later.
209         regs_->set_dex_pc(0);
210 
211         // Make sure there is enough room for the real frame.
212         if (frames_.size() == max_frames_) {
213           last_error_.code = ERROR_MAX_FRAMES_EXCEEDED;
214           break;
215         }
216       }
217 
218       frame = FillInFrame(map_info, elf, rel_pc, pc_adjustment);
219 
220       // Once a frame is added, stop skipping frames.
221       initial_map_names_to_skip = nullptr;
222     }
223     adjust_pc = true;
224 
225     bool stepped = false;
226     bool in_device_map = false;
227     bool finished = false;
228     if (map_info != nullptr) {
229       if (map_info->flags & MAPS_FLAGS_DEVICE_MAP) {
230         // Do not stop here, fall through in case we are
231         // in the speculative unwind path and need to remove
232         // some of the speculative frames.
233         in_device_map = true;
234       } else {
235         MapInfo* sp_info = maps_->Find(regs_->sp());
236         if (sp_info != nullptr && sp_info->flags & MAPS_FLAGS_DEVICE_MAP) {
237           // Do not stop here, fall through in case we are
238           // in the speculative unwind path and need to remove
239           // some of the speculative frames.
240           in_device_map = true;
241         } else {
242           if (elf->StepIfSignalHandler(rel_pc, regs_, process_memory_.get())) {
243             stepped = true;
244             if (frame != nullptr) {
245               // Need to adjust the relative pc because the signal handler
246               // pc should not be adjusted.
247               frame->rel_pc = rel_pc;
248               frame->pc += pc_adjustment;
249               step_pc = rel_pc;
250             }
251           } else if (elf->Step(step_pc, regs_, process_memory_.get(), &finished)) {
252             stepped = true;
253           }
254           elf->GetLastError(&last_error_);
255         }
256       }
257     }
258 
259     if (frame != nullptr) {
260       if (!resolve_names_ ||
261           !elf->GetFunctionName(step_pc, &frame->function_name, &frame->function_offset)) {
262         frame->function_name = "";
263         frame->function_offset = 0;
264       }
265     }
266 
267     if (finished) {
268       break;
269     }
270 
271     if (!stepped) {
272       if (return_address_attempt) {
273         // Only remove the speculative frame if there are more than two frames
274         // or the pc in the first frame is in a valid map.
275         // This allows for a case where the code jumps into the middle of
276         // nowhere, but there is no other unwind information after that.
277         if (frames_.size() > 2 || (frames_.size() > 0 && maps_->Find(frames_[0].pc) != nullptr)) {
278           // Remove the speculative frame.
279           frames_.pop_back();
280         }
281         break;
282       } else if (in_device_map) {
283         // Do not attempt any other unwinding, pc or sp is in a device
284         // map.
285         break;
286       } else {
287         // Steping didn't work, try this secondary method.
288         if (!regs_->SetPcFromReturnAddress(process_memory_.get())) {
289           break;
290         }
291         return_address_attempt = true;
292       }
293     } else {
294       return_address_attempt = false;
295       if (max_frames_ == frames_.size()) {
296         last_error_.code = ERROR_MAX_FRAMES_EXCEEDED;
297       }
298     }
299 
300     // If the pc and sp didn't change, then consider everything stopped.
301     if (cur_pc == regs_->pc() && cur_sp == regs_->sp()) {
302       last_error_.code = ERROR_REPEATED_FRAME;
303       break;
304     }
305   }
306 }
307 
FormatFrame(const FrameData & frame)308 std::string Unwinder::FormatFrame(const FrameData& frame) {
309   std::string data;
310   if (regs_->Is32Bit()) {
311     data += android::base::StringPrintf("  #%02zu pc %08" PRIx64, frame.num, frame.rel_pc);
312   } else {
313     data += android::base::StringPrintf("  #%02zu pc %016" PRIx64, frame.num, frame.rel_pc);
314   }
315 
316   if (frame.map_start == frame.map_end) {
317     // No valid map associated with this frame.
318     data += "  <unknown>";
319   } else if (!frame.map_name.empty()) {
320     data += "  " + frame.map_name;
321   } else {
322     data += android::base::StringPrintf("  <anonymous:%" PRIx64 ">", frame.map_start);
323   }
324 
325   if (frame.map_elf_start_offset != 0) {
326     data += android::base::StringPrintf(" (offset 0x%" PRIx64 ")", frame.map_elf_start_offset);
327   }
328 
329   if (!frame.function_name.empty()) {
330     data += " (" + demangle(frame.function_name.c_str());
331     if (frame.function_offset != 0) {
332       data += android::base::StringPrintf("+%" PRId64, frame.function_offset);
333     }
334     data += ')';
335   }
336 
337   MapInfo* map_info = maps_->Find(frame.map_start);
338   if (map_info != nullptr && display_build_id_) {
339     std::string build_id = map_info->GetPrintableBuildID();
340     if (!build_id.empty()) {
341       data += " (BuildId: " + build_id + ')';
342     }
343   }
344   return data;
345 }
346 
FormatFrame(size_t frame_num)347 std::string Unwinder::FormatFrame(size_t frame_num) {
348   if (frame_num >= frames_.size()) {
349     return "";
350   }
351   return FormatFrame(frames_[frame_num]);
352 }
353 
SetJitDebug(JitDebug * jit_debug,ArchEnum arch)354 void Unwinder::SetJitDebug(JitDebug* jit_debug, ArchEnum arch) {
355   jit_debug->SetArch(arch);
356   jit_debug_ = jit_debug;
357 }
358 
359 #if !defined(NO_LIBDEXFILE_SUPPORT)
SetDexFiles(DexFiles * dex_files,ArchEnum arch)360 void Unwinder::SetDexFiles(DexFiles* dex_files, ArchEnum arch) {
361   dex_files->SetArch(arch);
362   dex_files_ = dex_files;
363 }
364 #endif
365 
Init(ArchEnum arch)366 bool UnwinderFromPid::Init(ArchEnum arch) {
367   if (pid_ == getpid()) {
368     maps_ptr_.reset(new LocalMaps());
369   } else {
370     maps_ptr_.reset(new RemoteMaps(pid_));
371   }
372   if (!maps_ptr_->Parse()) {
373     return false;
374   }
375   maps_ = maps_ptr_.get();
376 
377   process_memory_ = Memory::CreateProcessMemoryCached(pid_);
378 
379   jit_debug_ptr_.reset(new JitDebug(process_memory_));
380   jit_debug_ = jit_debug_ptr_.get();
381   SetJitDebug(jit_debug_, arch);
382 #if !defined(NO_LIBDEXFILE_SUPPORT)
383   dex_files_ptr_.reset(new DexFiles(process_memory_));
384   dex_files_ = dex_files_ptr_.get();
385   SetDexFiles(dex_files_, arch);
386 #endif
387 
388   return true;
389 }
390 
391 }  // namespace unwindstack
392