1 /*
2  * Copyright (C) 2013 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 #ifndef _BACKTRACE_BACKTRACE_H
18 #define _BACKTRACE_BACKTRACE_H
19 
20 #include <inttypes.h>
21 #include <stdint.h>
22 
23 #include <string>
24 #include <vector>
25 
26 #include <backtrace/backtrace_constants.h>
27 #include <backtrace/BacktraceMap.h>
28 
29 #if defined(__LP64__)
30 #define PRIPTR "016" PRIx64
31 typedef uint64_t word_t;
32 #else
33 #define PRIPTR "08" PRIx64
34 typedef uint32_t word_t;
35 #endif
36 
37 enum BacktraceUnwindErrorCode : uint32_t {
38   BACKTRACE_UNWIND_NO_ERROR,
39   // Something failed while trying to perform the setup to begin the unwind.
40   BACKTRACE_UNWIND_ERROR_SETUP_FAILED,
41   // There is no map information to use with the unwind.
42   BACKTRACE_UNWIND_ERROR_MAP_MISSING,
43   // An error occurred that indicates a programming error.
44   BACKTRACE_UNWIND_ERROR_INTERNAL,
45   // The thread to unwind has disappeared before the unwind can begin.
46   BACKTRACE_UNWIND_ERROR_THREAD_DOESNT_EXIST,
47   // The thread to unwind has not responded to a signal in a timely manner.
48   BACKTRACE_UNWIND_ERROR_THREAD_TIMEOUT,
49   // Attempt to do an unsupported operation.
50   BACKTRACE_UNWIND_ERROR_UNSUPPORTED_OPERATION,
51   // Attempt to do an offline unwind without a context.
52   BACKTRACE_UNWIND_ERROR_NO_CONTEXT,
53   // The count of frames exceed MAX_BACKTRACE_FRAMES.
54   BACKTRACE_UNWIND_ERROR_EXCEED_MAX_FRAMES_LIMIT,
55   // Failed to read memory.
56   BACKTRACE_UNWIND_ERROR_ACCESS_MEM_FAILED,
57   // Failed to read registers.
58   BACKTRACE_UNWIND_ERROR_ACCESS_REG_FAILED,
59   // Failed to find a function in debug sections.
60   BACKTRACE_UNWIND_ERROR_FIND_PROC_INFO_FAILED,
61   // Failed to execute dwarf instructions in debug sections.
62   BACKTRACE_UNWIND_ERROR_EXECUTE_DWARF_INSTRUCTION_FAILED,
63   // Unwind information is incorrect.
64   BACKTRACE_UNWIND_ERROR_UNWIND_INFO,
65   // Unwind information stopped due to sp/pc repeating.
66   BACKTRACE_UNWIND_ERROR_REPEATED_FRAME,
67 };
68 
69 struct BacktraceUnwindError {
70   enum BacktraceUnwindErrorCode error_code;
71 
72   union {
73     // for BACKTRACE_UNWIND_ERROR_ACCESS_MEM_FAILED
74     uint64_t addr;
75     // for BACKTRACE_UNWIND_ERROR_ACCESS_REG_FAILED
76     uint64_t regno;
77   } error_info;
78 
BacktraceUnwindErrorBacktraceUnwindError79   BacktraceUnwindError() : error_code(BACKTRACE_UNWIND_NO_ERROR) {}
80 };
81 
82 struct backtrace_frame_data_t {
83   size_t num;             // The current fame number.
84   uint64_t pc;            // The absolute pc.
85   uint64_t rel_pc;        // The relative pc.
86   uint64_t sp;            // The top of the stack.
87   size_t stack_size;      // The size of the stack, zero indicate an unknown stack size.
88   backtrace_map_t map;    // The map associated with the given pc.
89   std::string func_name;  // The function name associated with this pc, NULL if not found.
90   uint64_t func_offset;  // pc relative to the start of the function, only valid if func_name is not
91                          // NULL.
92 };
93 
94 struct backtrace_stackinfo_t {
95   uint64_t start;
96   uint64_t end;
97   const uint8_t* data;
98 };
99 
100 namespace unwindstack {
101 class Regs;
102 }
103 
104 class Backtrace {
105  public:
106   enum ArchEnum : uint8_t {
107     ARCH_ARM,
108     ARCH_ARM64,
109     ARCH_X86,
110     ARCH_X86_64,
111   };
112 
113   static void SetGlobalElfCache(bool enable);
114 
115   // Create the correct Backtrace object based on what is to be unwound.
116   // If pid < 0 or equals the current pid, then the Backtrace object
117   // corresponds to the current process.
118   // If pid < 0 or equals the current pid and tid >= 0, then the Backtrace
119   // object corresponds to a thread in the current process.
120   // If pid >= 0 and tid < 0, then the Backtrace object corresponds to a
121   // different process.
122   // Tracing a thread in a different process is not supported.
123   // If map is NULL, then create the map and manage it internally.
124   // If map is not NULL, the map is still owned by the caller.
125   static Backtrace* Create(pid_t pid, pid_t tid, BacktraceMap* map = NULL);
126 
127   // Create an offline Backtrace object that can be used to do an unwind without a process
128   // that is still running. By default, information is only cached in the map
129   // file. If the calling code creates the map, data can be cached between
130   // unwinds. If not, all cached data will be destroyed when the Backtrace
131   // object is destroyed.
132   static Backtrace* CreateOffline(ArchEnum arch, pid_t pid, pid_t tid,
133                                   const std::vector<backtrace_map_t>& maps,
134                                   const backtrace_stackinfo_t& stack);
135   static Backtrace* CreateOffline(ArchEnum arch, pid_t pid, pid_t tid, BacktraceMap* map);
136 
137   // Create an offline Backtrace object that can be used to do an unwind without a process
138   // that is still running. If cache_file is set to true, then elf information will be cached
139   // for this call. The cached information survives until the calling process ends. This means
140   // that subsequent calls to create offline Backtrace objects will continue to use the same
141   // cache. It also assumes that the elf files used for each offline unwind are the same.
142   static Backtrace* CreateOffline(pid_t pid, pid_t tid, BacktraceMap* map,
143                                   const backtrace_stackinfo_t& stack, bool cache_file = false);
144 
145   virtual ~Backtrace();
146 
147   // Get the current stack trace and store in the backtrace_ structure.
148   virtual bool Unwind(size_t num_ignore_frames, void* context = NULL) = 0;
149 
150   static bool Unwind(unwindstack::Regs* regs, BacktraceMap* back_map,
151                      std::vector<backtrace_frame_data_t>* frames, size_t num_ignore_frames,
152                      std::vector<std::string>* skip_names, BacktraceUnwindError* error = nullptr);
153 
154   static bool UnwindOffline(unwindstack::Regs* regs, BacktraceMap* back_map,
155                             const backtrace_stackinfo_t& stack_info,
156                             std::vector<backtrace_frame_data_t>* frames,
157                             BacktraceUnwindError* error = nullptr);
158 
159   // Get the function name and offset into the function given the pc.
160   // If the string is empty, then no valid function name was found,
161   // or the pc is not in any valid map.
162   virtual std::string GetFunctionName(uint64_t pc, uint64_t* offset,
163                                       const backtrace_map_t* map = NULL);
164 
165   // Fill in the map data associated with the given pc.
166   virtual void FillInMap(uint64_t pc, backtrace_map_t* map);
167 
168   // Read the data at a specific address.
169   virtual bool ReadWord(uint64_t ptr, word_t* out_value) = 0;
170 
171   // Read arbitrary data from a specific address. If a read request would
172   // span from one map to another, this call only reads up until the end
173   // of the current map.
174   // Returns the total number of bytes actually read.
175   virtual size_t Read(uint64_t addr, uint8_t* buffer, size_t bytes) = 0;
176 
177   // Create a string representing the formatted line of backtrace information
178   // for a single frame.
179   virtual std::string FormatFrameData(size_t frame_num);
180   static std::string FormatFrameData(const backtrace_frame_data_t* frame);
181 
Pid()182   pid_t Pid() const { return pid_; }
Tid()183   pid_t Tid() const { return tid_; }
NumFrames()184   size_t NumFrames() const { return frames_.size(); }
185 
GetFrame(size_t frame_num)186   const backtrace_frame_data_t* GetFrame(size_t frame_num) {
187     if (frame_num >= frames_.size()) {
188       return NULL;
189     }
190     return &frames_[frame_num];
191   }
192 
193   typedef std::vector<backtrace_frame_data_t>::iterator iterator;
begin()194   iterator begin() { return frames_.begin(); }
end()195   iterator end() { return frames_.end(); }
196 
197   typedef std::vector<backtrace_frame_data_t>::const_iterator const_iterator;
begin()198   const_iterator begin() const { return frames_.begin(); }
end()199   const_iterator end() const { return frames_.end(); }
200 
GetMap()201   BacktraceMap* GetMap() { return map_; }
202 
GetError()203   BacktraceUnwindError GetError() { return error_; }
204 
205   std::string GetErrorString(BacktraceUnwindError error);
206 
207   // Set whether to skip frames in libbacktrace/libunwindstack when doing a local unwind.
SetSkipFrames(bool skip_frames)208   void SetSkipFrames(bool skip_frames) { skip_frames_ = skip_frames; }
209 
210  protected:
211   Backtrace(pid_t pid, pid_t tid, BacktraceMap* map);
212 
213   // The name returned is not demangled, GetFunctionName() takes care of
214   // demangling the name.
215   virtual std::string GetFunctionNameRaw(uint64_t pc, uint64_t* offset) = 0;
216 
217   virtual bool VerifyReadWordArgs(uint64_t ptr, word_t* out_value);
218 
219   bool BuildMap();
220 
221   pid_t pid_;
222   pid_t tid_;
223 
224   BacktraceMap* map_;
225   bool map_shared_;
226 
227   std::vector<backtrace_frame_data_t> frames_;
228 
229   // Skip frames in libbacktrace/libunwindstack when doing a local unwind.
230   bool skip_frames_ = true;
231 
232   BacktraceUnwindError error_;
233 };
234 
235 #endif // _BACKTRACE_BACKTRACE_H
236