utility.c revision f0c5872637a63e28e3cd314cfc915c07f76df9c6 
1/* system/debuggerd/utility.c
2**
3** Copyright 2008, The Android Open Source Project
4**
5** Licensed under the Apache License, Version 2.0 (the "License");
6** you may not use this file except in compliance with the License.
7** You may obtain a copy of the License at
8**
9**     http://www.apache.org/licenses/LICENSE-2.0
10**
11** Unless required by applicable law or agreed to in writing, software
12** distributed under the License is distributed on an "AS IS" BASIS,
13** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14** See the License for the specific language governing permissions and
15** limitations under the License.
16*/
17
18#include <signal.h>
19#include <string.h>
20#include <cutils/logd.h>
21#include <sys/ptrace.h>
22#include <errno.h>
23#include <corkscrew/demangle.h>
24
25#include "utility.h"
26
27#define STACK_DEPTH 32
28#define STACK_WORDS 16
29
30void _LOG(int tfd, bool in_tombstone_only, const char *fmt, ...) {
31    char buf[512];
32
33    va_list ap;
34    va_start(ap, fmt);
35
36    if (tfd >= 0) {
37        int len;
38        vsnprintf(buf, sizeof(buf), fmt, ap);
39        len = strlen(buf);
40        if(tfd >= 0) write(tfd, buf, len);
41    }
42
43    if (!in_tombstone_only)
44        __android_log_vprint(ANDROID_LOG_INFO, "DEBUG", fmt, ap);
45    va_end(ap);
46}
47
48bool signal_has_address(int sig) {
49    switch (sig) {
50        case SIGILL:
51        case SIGFPE:
52        case SIGSEGV:
53        case SIGBUS:
54            return true;
55        default:
56            return false;
57    }
58}
59
60static void dump_backtrace(const ptrace_context_t* context __attribute((unused)),
61        int tfd, pid_t tid __attribute((unused)), bool at_fault,
62        const backtrace_frame_t* backtrace, size_t frames) {
63    _LOG(tfd, !at_fault, "\nbacktrace:\n");
64
65    backtrace_symbol_t backtrace_symbols[STACK_DEPTH];
66    get_backtrace_symbols_ptrace(context, backtrace, frames, backtrace_symbols);
67    for (size_t i = 0; i < frames; i++) {
68        const backtrace_symbol_t* symbol = &backtrace_symbols[i];
69        const char* map_name = symbol->map_name ? symbol->map_name : "<unknown>";
70        const char* symbol_name = symbol->demangled_name ? symbol->demangled_name : symbol->name;
71        if (symbol_name) {
72            _LOG(tfd, !at_fault, "    #%02d  pc %08x  %s (%s)\n",
73                    (int)i, symbol->relative_pc, map_name, symbol_name);
74        } else {
75            _LOG(tfd, !at_fault, "    #%02d  pc %08x  %s\n",
76                    (int)i, symbol->relative_pc, map_name);
77        }
78    }
79    free_backtrace_symbols(backtrace_symbols, frames);
80}
81
82static void dump_stack_segment(const ptrace_context_t* context, int tfd, pid_t tid,
83        bool only_in_tombstone, uintptr_t* sp, size_t words, int label) {
84    for (size_t i = 0; i < words; i++) {
85        uint32_t stack_content;
86        if (!try_get_word_ptrace(tid, *sp, &stack_content)) {
87            break;
88        }
89
90        const map_info_t* mi;
91        const symbol_t* symbol;
92        find_symbol_ptrace(context, stack_content, &mi, &symbol);
93
94        if (symbol) {
95            char* demangled_name = demangle_symbol_name(symbol->name);
96            const char* symbol_name = demangled_name ? demangled_name : symbol->name;
97            if (!i && label >= 0) {
98                _LOG(tfd, only_in_tombstone, "    #%02d  %08x  %08x  %s (%s)\n",
99                        label, *sp, stack_content, mi ? mi->name : "", symbol_name);
100            } else {
101                _LOG(tfd, only_in_tombstone, "         %08x  %08x  %s (%s)\n",
102                        *sp, stack_content, mi ? mi->name : "", symbol_name);
103            }
104            free(demangled_name);
105        } else {
106            if (!i && label >= 0) {
107                _LOG(tfd, only_in_tombstone, "    #%02d  %08x  %08x  %s\n",
108                        label, *sp, stack_content, mi ? mi->name : "");
109            } else {
110                _LOG(tfd, only_in_tombstone, "         %08x  %08x  %s\n",
111                        *sp, stack_content, mi ? mi->name : "");
112            }
113        }
114
115        *sp += sizeof(uint32_t);
116    }
117}
118
119static void dump_stack(const ptrace_context_t* context, int tfd, pid_t tid, bool at_fault,
120        const backtrace_frame_t* backtrace, size_t frames) {
121    bool have_first = false;
122    size_t first, last;
123    for (size_t i = 0; i < frames; i++) {
124        if (backtrace[i].stack_top) {
125            if (!have_first) {
126                have_first = true;
127                first = i;
128            }
129            last = i;
130        }
131    }
132    if (!have_first) {
133        return;
134    }
135
136    _LOG(tfd, !at_fault, "\nstack:\n");
137
138    // Dump a few words before the first frame.
139    bool only_in_tombstone = !at_fault;
140    uintptr_t sp = backtrace[first].stack_top - STACK_WORDS * sizeof(uint32_t);
141    dump_stack_segment(context, tfd, tid, only_in_tombstone, &sp, STACK_WORDS, -1);
142
143    // Dump a few words from all successive frames.
144    // Only log the first 3 frames, put the rest in the tombstone.
145    for (size_t i = first; i <= last; i++) {
146        const backtrace_frame_t* frame = &backtrace[i];
147        if (sp != frame->stack_top) {
148            _LOG(tfd, only_in_tombstone, "         ........  ........\n");
149            sp = frame->stack_top;
150        }
151        if (i - first == 3) {
152            only_in_tombstone = true;
153        }
154        if (i == last) {
155            dump_stack_segment(context, tfd, tid, only_in_tombstone, &sp, STACK_WORDS, i);
156            if (sp < frame->stack_top + frame->stack_size) {
157                _LOG(tfd, only_in_tombstone, "         ........  ........\n");
158            }
159        } else {
160            size_t words = frame->stack_size / sizeof(uint32_t);
161            if (words == 0) {
162                words = 1;
163            } else if (words > STACK_WORDS) {
164                words = STACK_WORDS;
165            }
166            dump_stack_segment(context, tfd, tid, only_in_tombstone, &sp, words, i);
167        }
168    }
169}
170
171void dump_backtrace_and_stack(const ptrace_context_t* context, int tfd, pid_t tid,
172        bool at_fault) {
173    backtrace_frame_t backtrace[STACK_DEPTH];
174    ssize_t frames = unwind_backtrace_ptrace(tid, context, backtrace, 0, STACK_DEPTH);
175    if (frames > 0) {
176        dump_backtrace(context, tfd, tid, at_fault, backtrace, frames);
177        dump_stack(context, tfd, tid, at_fault, backtrace, frames);
178    }
179}
180
181void dump_memory(int tfd, pid_t tid, uintptr_t addr, bool at_fault) {
182    char code_buffer[64];       /* actual 8+1+((8+1)*4) + 1 == 45 */
183    char ascii_buffer[32];      /* actual 16 + 1 == 17 */
184    uintptr_t p, end;
185
186    p = addr & ~3;
187    p -= 32;
188    if (p > addr) {
189        /* catch underflow */
190        p = 0;
191    }
192    end = p + 80;
193    /* catch overflow; 'end - p' has to be multiples of 16 */
194    while (end < p)
195        end -= 16;
196
197    /* Dump the code around PC as:
198     *  addr     contents                             ascii
199     *  00008d34 ef000000 e8bd0090 e1b00000 512fff1e  ............../Q
200     *  00008d44 ea00b1f9 e92d0090 e3a070fc ef000000  ......-..p......
201     */
202    while (p < end) {
203        char* asc_out = ascii_buffer;
204
205        sprintf(code_buffer, "%08x ", p);
206
207        int i;
208        for (i = 0; i < 4; i++) {
209            /*
210             * If we see (data == -1 && errno != 0), we know that the ptrace
211             * call failed, probably because we're dumping memory in an
212             * unmapped or inaccessible page.  I don't know if there's
213             * value in making that explicit in the output -- it likely
214             * just complicates parsing and clarifies nothing for the
215             * enlightened reader.
216             */
217            long data = ptrace(PTRACE_PEEKTEXT, tid, (void*)p, NULL);
218            sprintf(code_buffer + strlen(code_buffer), "%08lx ", data);
219
220            int j;
221            for (j = 0; j < 4; j++) {
222                /*
223                 * Our isprint() allows high-ASCII characters that display
224                 * differently (often badly) in different viewers, so we
225                 * just use a simpler test.
226                 */
227                char val = (data >> (j*8)) & 0xff;
228                if (val >= 0x20 && val < 0x7f) {
229                    *asc_out++ = val;
230                } else {
231                    *asc_out++ = '.';
232                }
233            }
234            p += 4;
235        }
236        *asc_out = '\0';
237        _LOG(tfd, !at_fault, "    %s %s\n", code_buffer, ascii_buffer);
238    }
239}
240
241void dump_nearby_maps(const ptrace_context_t* context, int tfd, pid_t tid) {
242    siginfo_t si;
243    memset(&si, 0, sizeof(si));
244    if (ptrace(PTRACE_GETSIGINFO, tid, 0, &si)) {
245        _LOG(tfd, false, "cannot get siginfo for %d: %s\n",
246                tid, strerror(errno));
247        return;
248    }
249    if (!signal_has_address(si.si_signo)) {
250        return;
251    }
252
253    uintptr_t addr = (uintptr_t) si.si_addr;
254    addr &= ~0xfff;     /* round to 4K page boundary */
255    if (addr == 0) {    /* null-pointer deref */
256        return;
257    }
258
259    _LOG(tfd, false, "\nmemory map around fault addr %08x:\n", (int)si.si_addr);
260
261    /*
262     * Search for a match, or for a hole where the match would be.  The list
263     * is backward from the file content, so it starts at high addresses.
264     */
265    bool found = false;
266    map_info_t* map = context->map_info_list;
267    map_info_t *next = NULL;
268    map_info_t *prev = NULL;
269    while (map != NULL) {
270        if (addr >= map->start && addr < map->end) {
271            found = true;
272            next = map->next;
273            break;
274        } else if (addr >= map->end) {
275            /* map would be between "prev" and this entry */
276            next = map;
277            map = NULL;
278            break;
279        }
280
281        prev = map;
282        map = map->next;
283    }
284
285    /*
286     * Show "next" then "match" then "prev" so that the addresses appear in
287     * ascending order (like /proc/pid/maps).
288     */
289    if (next != NULL) {
290        _LOG(tfd, false, "    %08x-%08x %s\n", next->start, next->end, next->name);
291    } else {
292        _LOG(tfd, false, "    (no map below)\n");
293    }
294    if (map != NULL) {
295        _LOG(tfd, false, "    %08x-%08x %s\n", map->start, map->end, map->name);
296    } else {
297        _LOG(tfd, false, "    (no map for address)\n");
298    }
299    if (prev != NULL) {
300        _LOG(tfd, false, "    %08x-%08x %s\n", prev->start, prev->end, prev->name);
301    } else {
302        _LOG(tfd, false, "    (no map above)\n");
303    }
304}
305