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 <unistd.h>
33 #include <unwind.h>
34 #include <sys/types.h>
35
36 #include "debug_mapinfo.h"
37 #include "libc_logging.h"
38
39 /* depends how the system includes define this */
40 #ifdef HAVE_UNWIND_CONTEXT_STRUCT
41 typedef struct _Unwind_Context __unwind_context;
42 #else
43 typedef _Unwind_Context __unwind_context;
44 #endif
45
46 static mapinfo_t* gMapInfo = NULL;
47 static void* gDemangler;
48 typedef char* (*DemanglerFn)(const char*, char*, size_t*, int*);
49 static DemanglerFn gDemanglerFn = NULL;
50
backtrace_startup()51 __LIBC_HIDDEN__ void backtrace_startup() {
52 gMapInfo = mapinfo_create(getpid());
53 gDemangler = dlopen("libgccdemangle.so", RTLD_NOW);
54 if (gDemangler != NULL) {
55 void* sym = dlsym(gDemangler, "__cxa_demangle");
56 gDemanglerFn = reinterpret_cast<DemanglerFn>(sym);
57 }
58 }
59
backtrace_shutdown()60 __LIBC_HIDDEN__ void backtrace_shutdown() {
61 mapinfo_destroy(gMapInfo);
62 dlclose(gDemangler);
63 }
64
demangle(const char * symbol)65 static char* demangle(const char* symbol) {
66 if (gDemanglerFn == NULL) {
67 return NULL;
68 }
69 return (*gDemanglerFn)(symbol, NULL, NULL, NULL);
70 }
71
72 struct stack_crawl_state_t {
73 uintptr_t* frames;
74 size_t frame_count;
75 size_t max_depth;
76 bool have_skipped_self;
77
stack_crawl_state_tstack_crawl_state_t78 stack_crawl_state_t(uintptr_t* frames, size_t max_depth)
79 : frames(frames), frame_count(0), max_depth(max_depth), have_skipped_self(false) {
80 }
81 };
82
trace_function(__unwind_context * context,void * arg)83 static _Unwind_Reason_Code trace_function(__unwind_context* context, void* arg) {
84 stack_crawl_state_t* state = static_cast<stack_crawl_state_t*>(arg);
85
86 uintptr_t ip = _Unwind_GetIP(context);
87
88 // The first stack frame is get_backtrace itself. Skip it.
89 if (ip != 0 && !state->have_skipped_self) {
90 state->have_skipped_self = true;
91 return _URC_NO_REASON;
92 }
93
94 #ifdef __arm__
95 /*
96 * The instruction pointer is pointing at the instruction after the bl(x), and
97 * the _Unwind_Backtrace routine already masks the Thumb mode indicator (LSB
98 * in PC). So we need to do a quick check here to find out if the previous
99 * instruction is a Thumb-mode BLX(2). If so subtract 2 otherwise 4 from PC.
100 */
101 if (ip != 0) {
102 short* ptr = reinterpret_cast<short*>(ip);
103 // Thumb BLX(2)
104 if ((*(ptr-1) & 0xff80) == 0x4780) {
105 ip -= 2;
106 } else {
107 ip -= 4;
108 }
109 }
110 #endif
111
112 state->frames[state->frame_count++] = ip;
113 return (state->frame_count >= state->max_depth) ? _URC_END_OF_STACK : _URC_NO_REASON;
114 }
115
get_backtrace(uintptr_t * frames,size_t max_depth)116 __LIBC_HIDDEN__ int get_backtrace(uintptr_t* frames, size_t max_depth) {
117 stack_crawl_state_t state(frames, max_depth);
118 _Unwind_Backtrace(trace_function, &state);
119 return state.frame_count;
120 }
121
log_backtrace(uintptr_t * frames,size_t frame_count)122 __LIBC_HIDDEN__ void log_backtrace(uintptr_t* frames, size_t frame_count) {
123 uintptr_t self_bt[16];
124 if (frames == NULL) {
125 frame_count = get_backtrace(self_bt, 16);
126 frames = self_bt;
127 }
128
129 __libc_format_log(ANDROID_LOG_ERROR, "libc",
130 "*** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***\n");
131
132 for (size_t i = 0 ; i < frame_count; ++i) {
133 void* offset = 0;
134 const char* symbol = NULL;
135
136 Dl_info info;
137 if (dladdr((void*) frames[i], &info) != 0) {
138 offset = info.dli_saddr;
139 symbol = info.dli_sname;
140 }
141
142 uintptr_t rel_pc;
143 const mapinfo_t* mi = (gMapInfo != NULL) ? mapinfo_find(gMapInfo, frames[i], &rel_pc) : NULL;
144 const char* soname = (mi != NULL) ? mi->name : info.dli_fname;
145 if (soname == NULL) {
146 soname = "<unknown>";
147 }
148 if (symbol != NULL) {
149 // TODO: we might need a flag to say whether it's safe to allocate (demangling allocates).
150 char* demangled_symbol = demangle(symbol);
151 const char* best_name = (demangled_symbol != NULL) ? demangled_symbol : symbol;
152
153 __libc_format_log(ANDROID_LOG_ERROR, "libc", " #%02d pc %08x %s (%s+0x%x)",
154 i, rel_pc, soname, best_name, frames[i] - (uintptr_t) offset);
155
156 free(demangled_symbol);
157 } else {
158 __libc_format_log(ANDROID_LOG_ERROR, "libc", " #%02d pc %08x %s",
159 i, rel_pc, soname);
160 }
161 }
162 }
163