debug_stacktrace.cpp revision 11837629693e520452672e0eae28d3ce71f80ed6 
1/*
2 * Copyright (C) 2012 The Android Open Source Project
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 *  * Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 *  * Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in
12 *    the documentation and/or other materials provided with the
13 *    distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29#include "debug_stacktrace.h"
30
31#include <dlfcn.h>
32#include <inttypes.h>
33#include <unistd.h>
34#include <unwind.h>
35#include <sys/types.h>
36
37#include "debug_mapinfo.h"
38#include "malloc_debug_disable.h"
39#include "private/libc_logging.h"
40
41#if defined(__LP64__)
42#define PAD_PTR "016" PRIxPTR
43#else
44#define PAD_PTR "08" PRIxPTR
45#endif
46
47/* depends how the system includes define this */
48#ifdef HAVE_UNWIND_CONTEXT_STRUCT
49typedef struct _Unwind_Context __unwind_context;
50#else
51typedef _Unwind_Context __unwind_context;
52#endif
53
54static mapinfo_t* g_map_info = NULL;
55static void* g_demangler;
56typedef char* (*DemanglerFn)(const char*, char*, size_t*, int*);
57static DemanglerFn g_demangler_fn = NULL;
58
59__LIBC_HIDDEN__ void backtrace_startup() {
60  ScopedDisableDebugCalls disable;
61
62  g_map_info = mapinfo_create(getpid());
63  g_demangler = dlopen("libgccdemangle.so", RTLD_NOW);
64  if (g_demangler != NULL) {
65    void* sym = dlsym(g_demangler, "__cxa_demangle");
66    g_demangler_fn = reinterpret_cast<DemanglerFn>(sym);
67  }
68}
69
70__LIBC_HIDDEN__ void backtrace_shutdown() {
71  ScopedDisableDebugCalls disable;
72
73  mapinfo_destroy(g_map_info);
74  dlclose(g_demangler);
75}
76
77static char* demangle(const char* symbol) {
78  if (g_demangler_fn == NULL) {
79    return NULL;
80  }
81  return (*g_demangler_fn)(symbol, NULL, NULL, NULL);
82}
83
84struct stack_crawl_state_t {
85  uintptr_t* frames;
86  size_t frame_count;
87  size_t max_depth;
88  bool have_skipped_self;
89
90  stack_crawl_state_t(uintptr_t* frames, size_t max_depth)
91      : frames(frames), frame_count(0), max_depth(max_depth), have_skipped_self(false) {
92  }
93};
94
95static _Unwind_Reason_Code trace_function(__unwind_context* context, void* arg) {
96  stack_crawl_state_t* state = static_cast<stack_crawl_state_t*>(arg);
97
98  uintptr_t ip = _Unwind_GetIP(context);
99
100  // The first stack frame is get_backtrace itself. Skip it.
101  if (ip != 0 && !state->have_skipped_self) {
102    state->have_skipped_self = true;
103    return _URC_NO_REASON;
104  }
105
106#if defined(__arm__)
107  /*
108   * The instruction pointer is pointing at the instruction after the bl(x), and
109   * the _Unwind_Backtrace routine already masks the Thumb mode indicator (LSB
110   * in PC). So we need to do a quick check here to find out if the previous
111   * instruction is a Thumb-mode BLX(2). If so subtract 2 otherwise 4 from PC.
112   */
113  if (ip != 0) {
114    short* ptr = reinterpret_cast<short*>(ip);
115    // Thumb BLX(2)
116    if ((*(ptr-1) & 0xff80) == 0x4780) {
117      ip -= 2;
118    } else {
119      ip -= 4;
120    }
121  }
122#endif
123
124  state->frames[state->frame_count++] = ip;
125  return (state->frame_count >= state->max_depth) ? _URC_END_OF_STACK : _URC_NO_REASON;
126}
127
128__LIBC_HIDDEN__ int get_backtrace(uintptr_t* frames, size_t max_depth) {
129  ScopedDisableDebugCalls disable;
130
131  stack_crawl_state_t state(frames, max_depth);
132  _Unwind_Backtrace(trace_function, &state);
133  return state.frame_count;
134}
135
136__LIBC_HIDDEN__ void log_backtrace(uintptr_t* frames, size_t frame_count) {
137  ScopedDisableDebugCalls disable;
138
139  uintptr_t self_bt[16];
140  if (frames == NULL) {
141    frame_count = get_backtrace(self_bt, 16);
142    frames = self_bt;
143  }
144
145  __libc_format_log(ANDROID_LOG_ERROR, "libc",
146                    "*** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***\n");
147
148  for (size_t i = 0 ; i < frame_count; ++i) {
149    uintptr_t offset = 0;
150    const char* symbol = NULL;
151
152    Dl_info info;
153    if (dladdr((void*) frames[i], &info) != 0) {
154      offset = reinterpret_cast<uintptr_t>(info.dli_saddr);
155      symbol = info.dli_sname;
156    }
157
158    uintptr_t rel_pc = offset;
159    const mapinfo_t* mi = (g_map_info != NULL) ? mapinfo_find(g_map_info, frames[i], &rel_pc) : NULL;
160    const char* soname = (mi != NULL) ? mi->name : info.dli_fname;
161    if (soname == NULL) {
162      soname = "<unknown>";
163    }
164    if (symbol != NULL) {
165      // TODO: we might need a flag to say whether it's safe to allocate (demangling allocates).
166      char* demangled_symbol = demangle(symbol);
167      const char* best_name = (demangled_symbol != NULL) ? demangled_symbol : symbol;
168
169      __libc_format_log(ANDROID_LOG_ERROR, "libc",
170                        "          #%02zd  pc %" PAD_PTR "  %s (%s+%" PRIuPTR ")",
171                        i, rel_pc, soname, best_name, frames[i] - offset);
172
173      free(demangled_symbol);
174    } else {
175      __libc_format_log(ANDROID_LOG_ERROR, "libc",
176                        "          #%02zd  pc %" PAD_PTR "  %s",
177                        i, rel_pc, soname);
178    }
179  }
180}
181