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
49 typedef struct _Unwind_Context __unwind_context;
50 #else
51 typedef _Unwind_Context __unwind_context;
52 #endif
53
54 static mapinfo_t* g_map_info = NULL;
55 static void* g_demangler;
56 typedef char* (*DemanglerFn)(const char*, char*, size_t*, int*);
57 static DemanglerFn g_demangler_fn = NULL;
58
backtrace_startup()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
backtrace_shutdown()70 __LIBC_HIDDEN__ void backtrace_shutdown() {
71 ScopedDisableDebugCalls disable;
72
73 mapinfo_destroy(g_map_info);
74 dlclose(g_demangler);
75 }
76
demangle(const char * symbol)77 static 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
84 struct stack_crawl_state_t {
85 uintptr_t* frames;
86 size_t frame_count;
87 size_t max_depth;
88 bool have_skipped_self;
89
stack_crawl_state_tstack_crawl_state_t90 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
trace_function(__unwind_context * context,void * arg)95 static _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
get_backtrace(uintptr_t * frames,size_t max_depth)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
log_backtrace(uintptr_t * frames,size_t frame_count)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