1/*
2 * Copyright (C) 2011 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#define LOG_TAG "Corkscrew"
18//#define LOG_NDEBUG 0
19
20#include "backtrace-arch.h"
21#include "backtrace-helper.h"
22#include "ptrace-arch.h"
23#include <corkscrew/map_info.h>
24#include <corkscrew/symbol_table.h>
25#include <corkscrew/ptrace.h>
26#include <corkscrew/demangle.h>
27
28#include <unistd.h>
29#include <signal.h>
30#include <stdlib.h>
31#include <string.h>
32#include <pthread.h>
33#include <unwind.h>
34#include <cutils/log.h>
35#include <cutils/atomic.h>
36#include <elf.h>
37
38#define __USE_GNU // For dladdr(3) in glibc.
39#include <dlfcn.h>
40
41#if defined(__BIONIC__)
42
43// Bionic implements and exports gettid but only implements tgkill.
44extern int tgkill(int tgid, int tid, int sig);
45
46#else
47
48// glibc doesn't implement or export either gettid or tgkill.
49
50#include <unistd.h>
51#include <sys/syscall.h>
52
53static pid_t gettid() {
54  return syscall(__NR_gettid);
55}
56
57static int tgkill(int tgid, int tid, int sig) {
58  return syscall(__NR_tgkill, tgid, tid, sig);
59}
60
61#endif
62
63typedef struct {
64    backtrace_frame_t* backtrace;
65    size_t ignore_depth;
66    size_t max_depth;
67    size_t ignored_frames;
68    size_t returned_frames;
69    memory_t memory;
70} backtrace_state_t;
71
72static _Unwind_Reason_Code unwind_backtrace_callback(struct _Unwind_Context* context, void* arg) {
73    backtrace_state_t* state = (backtrace_state_t*)arg;
74    uintptr_t pc = _Unwind_GetIP(context);
75    if (pc) {
76        // TODO: Get information about the stack layout from the _Unwind_Context.
77        //       This will require a new architecture-specific function to query
78        //       the appropriate registers.  Current callers of unwind_backtrace
79        //       don't need this information, so we won't bother collecting it just yet.
80        add_backtrace_entry(rewind_pc_arch(&state->memory, pc), state->backtrace,
81                state->ignore_depth, state->max_depth,
82                &state->ignored_frames, &state->returned_frames);
83    }
84    return state->returned_frames < state->max_depth ? _URC_NO_REASON : _URC_END_OF_STACK;
85}
86
87ssize_t unwind_backtrace(backtrace_frame_t* backtrace, size_t ignore_depth, size_t max_depth) {
88    ALOGV("Unwinding current thread %d.", gettid());
89
90    map_info_t* milist = acquire_my_map_info_list();
91
92    backtrace_state_t state;
93    state.backtrace = backtrace;
94    state.ignore_depth = ignore_depth;
95    state.max_depth = max_depth;
96    state.ignored_frames = 0;
97    state.returned_frames = 0;
98    init_memory(&state.memory, milist);
99
100    _Unwind_Reason_Code rc =_Unwind_Backtrace(unwind_backtrace_callback, &state);
101
102    release_my_map_info_list(milist);
103
104    if (state.returned_frames) {
105        return state.returned_frames;
106    }
107    return rc == _URC_END_OF_STACK ? 0 : -1;
108}
109
110#ifdef CORKSCREW_HAVE_ARCH
111static const int32_t STATE_DUMPING = -1;
112static const int32_t STATE_DONE = -2;
113static const int32_t STATE_CANCEL = -3;
114
115static pthread_mutex_t g_unwind_signal_mutex = PTHREAD_MUTEX_INITIALIZER;
116static volatile struct {
117    int32_t tid_state;
118    const map_info_t* map_info_list;
119    backtrace_frame_t* backtrace;
120    size_t ignore_depth;
121    size_t max_depth;
122    size_t returned_frames;
123} g_unwind_signal_state;
124
125static void unwind_backtrace_thread_signal_handler(int n __attribute__((unused)), siginfo_t* siginfo, void* sigcontext) {
126    if (!android_atomic_acquire_cas(gettid(), STATE_DUMPING, &g_unwind_signal_state.tid_state)) {
127        g_unwind_signal_state.returned_frames = unwind_backtrace_signal_arch(
128                siginfo, sigcontext,
129                g_unwind_signal_state.map_info_list,
130                g_unwind_signal_state.backtrace,
131                g_unwind_signal_state.ignore_depth,
132                g_unwind_signal_state.max_depth);
133        android_atomic_release_store(STATE_DONE, &g_unwind_signal_state.tid_state);
134    } else {
135        ALOGV("Received spurious SIGURG on thread %d that was intended for thread %d.",
136                gettid(), android_atomic_acquire_load(&g_unwind_signal_state.tid_state));
137    }
138}
139#endif
140
141ssize_t unwind_backtrace_thread(pid_t tid, backtrace_frame_t* backtrace,
142        size_t ignore_depth, size_t max_depth) {
143    if (tid == gettid()) {
144        return unwind_backtrace(backtrace, ignore_depth + 1, max_depth);
145    }
146
147    ALOGV("Unwinding thread %d from thread %d.", tid, gettid());
148
149#ifdef CORKSCREW_HAVE_ARCH
150    struct sigaction act;
151    struct sigaction oact;
152    memset(&act, 0, sizeof(act));
153    act.sa_sigaction = unwind_backtrace_thread_signal_handler;
154    act.sa_flags = SA_RESTART | SA_SIGINFO | SA_ONSTACK;
155    sigemptyset(&act.sa_mask);
156
157    pthread_mutex_lock(&g_unwind_signal_mutex);
158    map_info_t* milist = acquire_my_map_info_list();
159
160    ssize_t frames = -1;
161    if (!sigaction(SIGURG, &act, &oact)) {
162        g_unwind_signal_state.map_info_list = milist;
163        g_unwind_signal_state.backtrace = backtrace;
164        g_unwind_signal_state.ignore_depth = ignore_depth;
165        g_unwind_signal_state.max_depth = max_depth;
166        g_unwind_signal_state.returned_frames = 0;
167        android_atomic_release_store(tid, &g_unwind_signal_state.tid_state);
168
169        // Signal the specific thread that we want to dump.
170        int32_t tid_state = tid;
171        if (tgkill(getpid(), tid, SIGURG)) {
172            ALOGV("Failed to send SIGURG to thread %d.", tid);
173        } else {
174            // Wait for the other thread to start dumping the stack, or time out.
175            int wait_millis = 250;
176            for (;;) {
177                tid_state = android_atomic_acquire_load(&g_unwind_signal_state.tid_state);
178                if (tid_state != tid) {
179                    break;
180                }
181                if (wait_millis--) {
182                    ALOGV("Waiting for thread %d to start dumping the stack...", tid);
183                    usleep(1000);
184                } else {
185                    ALOGV("Timed out waiting for thread %d to start dumping the stack.", tid);
186                    break;
187                }
188            }
189        }
190
191        // Try to cancel the dump if it has not started yet.
192        if (tid_state == tid) {
193            if (!android_atomic_acquire_cas(tid, STATE_CANCEL, &g_unwind_signal_state.tid_state)) {
194                ALOGV("Canceled thread %d stack dump.", tid);
195                tid_state = STATE_CANCEL;
196            } else {
197                tid_state = android_atomic_acquire_load(&g_unwind_signal_state.tid_state);
198            }
199        }
200
201        // Wait indefinitely for the dump to finish or be canceled.
202        // We cannot apply a timeout here because the other thread is accessing state that
203        // is owned by this thread, such as milist.  It should not take very
204        // long to take the dump once started.
205        while (tid_state == STATE_DUMPING) {
206            ALOGV("Waiting for thread %d to finish dumping the stack...", tid);
207            usleep(1000);
208            tid_state = android_atomic_acquire_load(&g_unwind_signal_state.tid_state);
209        }
210
211        if (tid_state == STATE_DONE) {
212            frames = g_unwind_signal_state.returned_frames;
213        }
214
215        sigaction(SIGURG, &oact, NULL);
216    }
217
218    release_my_map_info_list(milist);
219    pthread_mutex_unlock(&g_unwind_signal_mutex);
220    return frames;
221#else
222    return -1;
223#endif
224}
225
226ssize_t unwind_backtrace_ptrace(pid_t tid, const ptrace_context_t* context,
227        backtrace_frame_t* backtrace, size_t ignore_depth, size_t max_depth) {
228#ifdef CORKSCREW_HAVE_ARCH
229    return unwind_backtrace_ptrace_arch(tid, context, backtrace, ignore_depth, max_depth);
230#else
231    return -1;
232#endif
233}
234
235static void init_backtrace_symbol(backtrace_symbol_t* symbol, uintptr_t pc) {
236    symbol->relative_pc = pc;
237    symbol->relative_symbol_addr = 0;
238    symbol->map_name = NULL;
239    symbol->symbol_name = NULL;
240    symbol->demangled_name = NULL;
241}
242
243void get_backtrace_symbols(const backtrace_frame_t* backtrace, size_t frames,
244        backtrace_symbol_t* backtrace_symbols) {
245    map_info_t* milist = acquire_my_map_info_list();
246    for (size_t i = 0; i < frames; i++) {
247        const backtrace_frame_t* frame = &backtrace[i];
248        backtrace_symbol_t* symbol = &backtrace_symbols[i];
249        init_backtrace_symbol(symbol, frame->absolute_pc);
250
251        const map_info_t* mi = find_map_info(milist, frame->absolute_pc);
252        if (mi) {
253            symbol->relative_pc = frame->absolute_pc - mi->start;
254            if (mi->name[0]) {
255                symbol->map_name = strdup(mi->name);
256            }
257            Dl_info info;
258            if (dladdr((const void*)frame->absolute_pc, &info) && info.dli_sname) {
259                symbol->relative_symbol_addr = (uintptr_t)info.dli_saddr
260                        - (uintptr_t)info.dli_fbase;
261                symbol->symbol_name = strdup(info.dli_sname);
262                symbol->demangled_name = demangle_symbol_name(symbol->symbol_name);
263            }
264        }
265    }
266    release_my_map_info_list(milist);
267}
268
269void get_backtrace_symbols_ptrace(const ptrace_context_t* context,
270        const backtrace_frame_t* backtrace, size_t frames,
271        backtrace_symbol_t* backtrace_symbols) {
272    for (size_t i = 0; i < frames; i++) {
273        const backtrace_frame_t* frame = &backtrace[i];
274        backtrace_symbol_t* symbol = &backtrace_symbols[i];
275        init_backtrace_symbol(symbol, frame->absolute_pc);
276
277        const map_info_t* mi;
278        const symbol_t* s;
279        find_symbol_ptrace(context, frame->absolute_pc, &mi, &s);
280        if (mi) {
281            symbol->relative_pc = frame->absolute_pc - mi->start;
282            if (mi->name[0]) {
283                symbol->map_name = strdup(mi->name);
284            }
285        }
286        if (s) {
287            symbol->relative_symbol_addr = s->start;
288            symbol->symbol_name = strdup(s->name);
289            symbol->demangled_name = demangle_symbol_name(symbol->symbol_name);
290        }
291    }
292}
293
294void free_backtrace_symbols(backtrace_symbol_t* backtrace_symbols, size_t frames) {
295    for (size_t i = 0; i < frames; i++) {
296        backtrace_symbol_t* symbol = &backtrace_symbols[i];
297        free(symbol->map_name);
298        free(symbol->symbol_name);
299        free(symbol->demangled_name);
300        init_backtrace_symbol(symbol, 0);
301    }
302}
303
304void format_backtrace_line(unsigned frameNumber, const backtrace_frame_t* frame __attribute__((unused)),
305        const backtrace_symbol_t* symbol, char* buffer, size_t bufferSize) {
306    const char* mapName = symbol->map_name ? symbol->map_name : "<unknown>";
307    const char* symbolName = symbol->demangled_name ? symbol->demangled_name : symbol->symbol_name;
308    size_t fieldWidth = (bufferSize - 80) / 2;
309    if (symbolName) {
310        uint32_t pc_offset = symbol->relative_pc - symbol->relative_symbol_addr;
311        if (pc_offset) {
312            snprintf(buffer, bufferSize, "#%02d  pc %08x  %.*s (%.*s+%u)",
313                    frameNumber, symbol->relative_pc, fieldWidth, mapName,
314                    fieldWidth, symbolName, pc_offset);
315        } else {
316            snprintf(buffer, bufferSize, "#%02d  pc %08x  %.*s (%.*s)",
317                    frameNumber, symbol->relative_pc, fieldWidth, mapName,
318                    fieldWidth, symbolName);
319        }
320    } else {
321        snprintf(buffer, bufferSize, "#%02d  pc %08x  %.*s",
322                frameNumber, symbol->relative_pc, fieldWidth, mapName);
323    }
324}
325