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 #include <stdint.h>
18 #include <ucontext.h>
19 
20 #include <memory>
21 #include <string>
22 
23 #define UNW_LOCAL_ONLY
24 #include <libunwind.h>
25 
26 #include <android-base/logging.h>
27 #include <backtrace/Backtrace.h>
28 
29 #include "BacktraceLog.h"
30 #include "UnwindCurrent.h"
31 
GetFunctionNameRaw(uintptr_t pc,uintptr_t * offset)32 std::string UnwindCurrent::GetFunctionNameRaw(uintptr_t pc, uintptr_t* offset) {
33   if (!initialized_) {
34     // If init local is not called, then trying to get a function name will
35     // fail, so try to initialize first.
36     std::unique_ptr<unw_cursor_t> cursor(new unw_cursor_t);
37     if (unw_init_local(cursor.get(), &context_) < 0) {
38       return "";
39     }
40     initialized_ = true;
41   }
42 
43   *offset = 0;
44   char buf[512];
45   unw_word_t value;
46   if (unw_get_proc_name_by_ip(unw_local_addr_space, pc, buf, sizeof(buf),
47                               &value, &context_) >= 0 && buf[0] != '\0') {
48     *offset = static_cast<uintptr_t>(value);
49     return buf;
50   }
51   return "";
52 }
53 
GetUnwContextFromUcontext(const ucontext_t * ucontext)54 void UnwindCurrent::GetUnwContextFromUcontext(const ucontext_t* ucontext) {
55   unw_tdep_context_t* unw_context = reinterpret_cast<unw_tdep_context_t*>(&context_);
56 
57 #if defined(__arm__)
58   unw_context->regs[0] = ucontext->uc_mcontext.arm_r0;
59   unw_context->regs[1] = ucontext->uc_mcontext.arm_r1;
60   unw_context->regs[2] = ucontext->uc_mcontext.arm_r2;
61   unw_context->regs[3] = ucontext->uc_mcontext.arm_r3;
62   unw_context->regs[4] = ucontext->uc_mcontext.arm_r4;
63   unw_context->regs[5] = ucontext->uc_mcontext.arm_r5;
64   unw_context->regs[6] = ucontext->uc_mcontext.arm_r6;
65   unw_context->regs[7] = ucontext->uc_mcontext.arm_r7;
66   unw_context->regs[8] = ucontext->uc_mcontext.arm_r8;
67   unw_context->regs[9] = ucontext->uc_mcontext.arm_r9;
68   unw_context->regs[10] = ucontext->uc_mcontext.arm_r10;
69   unw_context->regs[11] = ucontext->uc_mcontext.arm_fp;
70   unw_context->regs[12] = ucontext->uc_mcontext.arm_ip;
71   unw_context->regs[13] = ucontext->uc_mcontext.arm_sp;
72   unw_context->regs[14] = ucontext->uc_mcontext.arm_lr;
73   unw_context->regs[15] = ucontext->uc_mcontext.arm_pc;
74 #else
75   unw_context->uc_mcontext = ucontext->uc_mcontext;
76 #endif
77 }
78 
UnwindFromContext(size_t num_ignore_frames,ucontext_t * ucontext)79 bool UnwindCurrent::UnwindFromContext(size_t num_ignore_frames, ucontext_t* ucontext) {
80   if (ucontext == nullptr) {
81     int ret = unw_getcontext(&context_);
82     if (ret < 0) {
83       BACK_LOGW("unw_getcontext failed %d", ret);
84       error_ = BACKTRACE_UNWIND_ERROR_SETUP_FAILED;
85       return false;
86     }
87   } else {
88     GetUnwContextFromUcontext(ucontext);
89   }
90 
91   // The cursor structure is pretty large, do not put it on the stack.
92   std::unique_ptr<unw_cursor_t> cursor(new unw_cursor_t);
93   int ret = unw_init_local(cursor.get(), &context_);
94   if (ret < 0) {
95     BACK_LOGW("unw_init_local failed %d", ret);
96     error_ = BACKTRACE_UNWIND_ERROR_SETUP_FAILED;
97     return false;
98   }
99   initialized_ = true;
100 
101   size_t num_frames = 0;
102   do {
103     unw_word_t pc;
104     ret = unw_get_reg(cursor.get(), UNW_REG_IP, &pc);
105     if (ret < 0) {
106       BACK_LOGW("Failed to read IP %d", ret);
107       break;
108     }
109     unw_word_t sp;
110     ret = unw_get_reg(cursor.get(), UNW_REG_SP, &sp);
111     if (ret < 0) {
112       BACK_LOGW("Failed to read SP %d", ret);
113       break;
114     }
115 
116     frames_.resize(num_frames+1);
117     backtrace_frame_data_t* frame = &frames_.at(num_frames);
118     frame->num = num_frames;
119     frame->pc = static_cast<uintptr_t>(pc);
120     frame->sp = static_cast<uintptr_t>(sp);
121     frame->stack_size = 0;
122 
123     FillInMap(frame->pc, &frame->map);
124     // Check to see if we should skip this frame because it's coming
125     // from within the library, and we are doing a local unwind.
126     if (ucontext != nullptr || num_frames != 0 || !DiscardFrame(*frame)) {
127       if (num_ignore_frames == 0) {
128         // GetFunctionName is an expensive call, only do it if we are
129         // keeping the frame.
130         frame->func_name = GetFunctionName(frame->pc, &frame->func_offset, &frame->map);
131         if (num_frames > 0) {
132           // Set the stack size for the previous frame.
133           backtrace_frame_data_t* prev = &frames_.at(num_frames-1);
134           prev->stack_size = frame->sp - prev->sp;
135         }
136         num_frames++;
137       } else {
138         num_ignore_frames--;
139         // Set the number of frames to zero to remove the frame added
140         // above. By definition, if we still have frames to ignore
141         // there should only be one frame in the vector.
142         CHECK(num_frames == 0);
143         frames_.resize(0);
144       }
145     }
146     // If the pc is in a device map, then don't try to step.
147     if (frame->map.flags & PROT_DEVICE_MAP) {
148       break;
149     }
150     // Verify the sp is not in a device map too.
151     backtrace_map_t map;
152     FillInMap(frame->sp, &map);
153     if (map.flags & PROT_DEVICE_MAP) {
154       break;
155     }
156     ret = unw_step (cursor.get());
157   } while (ret > 0 && num_frames < MAX_BACKTRACE_FRAMES);
158 
159   return true;
160 }
161