1/*
2 * Copyright 2008, 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 "DEBUG"
18
19#include "utility.h"
20
21#include <errno.h>
22#include <signal.h>
23#include <string.h>
24#include <sys/ptrace.h>
25#include <sys/wait.h>
26#include <unistd.h>
27
28#include <string>
29
30#include <android-base/stringprintf.h>
31#include <android-base/unique_fd.h>
32#include <backtrace/Backtrace.h>
33#include <log/log.h>
34
35// Whitelist output desired in the logcat output.
36bool is_allowed_in_logcat(enum logtype ltype) {
37  if ((ltype == HEADER)
38   || (ltype == REGISTERS)
39   || (ltype == BACKTRACE)) {
40    return true;
41  }
42  return false;
43}
44
45__attribute__((__weak__, visibility("default")))
46void _LOG(log_t* log, enum logtype ltype, const char* fmt, ...) {
47  bool write_to_tombstone = (log->tfd != -1);
48  bool write_to_logcat = is_allowed_in_logcat(ltype)
49                      && log->crashed_tid != -1
50                      && log->current_tid != -1
51                      && (log->crashed_tid == log->current_tid);
52
53  char buf[512];
54  va_list ap;
55  va_start(ap, fmt);
56  vsnprintf(buf, sizeof(buf), fmt, ap);
57  va_end(ap);
58
59  size_t len = strlen(buf);
60  if (len <= 0) {
61    return;
62  }
63
64  if (write_to_tombstone) {
65    TEMP_FAILURE_RETRY(write(log->tfd, buf, len));
66  }
67
68  if (write_to_logcat) {
69    __android_log_buf_write(LOG_ID_CRASH, ANDROID_LOG_FATAL, LOG_TAG, buf);
70    if (log->amfd_data != nullptr) {
71      *log->amfd_data += buf;
72    }
73  }
74}
75
76bool wait_for_signal(pid_t tid, siginfo_t* siginfo) {
77  while (true) {
78    int status;
79    pid_t n = TEMP_FAILURE_RETRY(waitpid(tid, &status, __WALL));
80    if (n == -1) {
81      ALOGE("waitpid failed: tid %d, %s", tid, strerror(errno));
82      return false;
83    } else if (n == tid) {
84      if (WIFSTOPPED(status)) {
85        if (ptrace(PTRACE_GETSIGINFO, tid, nullptr, siginfo) != 0) {
86          ALOGE("PTRACE_GETSIGINFO failed: %s", strerror(errno));
87          return false;
88        }
89        return true;
90      } else {
91        ALOGE("unexpected waitpid response: n=%d, status=%08x\n", n, status);
92        // This is the only circumstance under which we can allow a detach
93        // to fail with ESRCH, which indicates the tid has exited.
94        return false;
95      }
96    }
97  }
98}
99
100#define MEMORY_BYTES_TO_DUMP 256
101#define MEMORY_BYTES_PER_LINE 16
102
103void dump_memory(log_t* log, Backtrace* backtrace, uintptr_t addr, const char* fmt, ...) {
104  std::string log_msg;
105  va_list ap;
106  va_start(ap, fmt);
107  android::base::StringAppendV(&log_msg, fmt, ap);
108  va_end(ap);
109
110  // Align the address to sizeof(long) and start 32 bytes before the address.
111  addr &= ~(sizeof(long) - 1);
112  if (addr >= 4128) {
113    addr -= 32;
114  }
115
116  // Don't bother if the address looks too low, or looks too high.
117  if (addr < 4096 ||
118#if defined(__LP64__)
119      addr > 0x4000000000000000UL - MEMORY_BYTES_TO_DUMP) {
120#else
121      addr > 0xffff0000 - MEMORY_BYTES_TO_DUMP) {
122#endif
123    return;
124  }
125
126  _LOG(log, logtype::MEMORY, "\n%s\n", log_msg.c_str());
127
128  // Dump 256 bytes
129  uintptr_t data[MEMORY_BYTES_TO_DUMP/sizeof(uintptr_t)];
130  memset(data, 0, MEMORY_BYTES_TO_DUMP);
131  size_t bytes = backtrace->Read(addr, reinterpret_cast<uint8_t*>(data), sizeof(data));
132  if (bytes % sizeof(uintptr_t) != 0) {
133    // This should never happen, but just in case.
134    ALOGE("Bytes read %zu, is not a multiple of %zu", bytes, sizeof(uintptr_t));
135    bytes &= ~(sizeof(uintptr_t) - 1);
136  }
137
138  uintptr_t start = 0;
139  bool skip_2nd_read = false;
140  if (bytes == 0) {
141    // In this case, we might want to try another read at the beginning of
142    // the next page only if it's within the amount of memory we would have
143    // read.
144    size_t page_size = sysconf(_SC_PAGE_SIZE);
145    start = ((addr + (page_size - 1)) & ~(page_size - 1)) - addr;
146    if (start == 0 || start >= MEMORY_BYTES_TO_DUMP) {
147      skip_2nd_read = true;
148    }
149  }
150
151  if (bytes < MEMORY_BYTES_TO_DUMP && !skip_2nd_read) {
152    // Try to do one more read. This could happen if a read crosses a map,
153    // but the maps do not have any break between them. Or it could happen
154    // if reading from an unreadable map, but the read would cross back
155    // into a readable map. Only requires one extra read because a map has
156    // to contain at least one page, and the total number of bytes to dump
157    // is smaller than a page.
158    size_t bytes2 = backtrace->Read(addr + start + bytes, reinterpret_cast<uint8_t*>(data) + bytes,
159                                    sizeof(data) - bytes - start);
160    bytes += bytes2;
161    if (bytes2 > 0 && bytes % sizeof(uintptr_t) != 0) {
162      // This should never happen, but we'll try and continue any way.
163      ALOGE("Bytes after second read %zu, is not a multiple of %zu", bytes, sizeof(uintptr_t));
164      bytes &= ~(sizeof(uintptr_t) - 1);
165    }
166  }
167
168  // Dump the code around memory as:
169  //  addr             contents                           ascii
170  //  0000000000008d34 ef000000e8bd0090 e1b00000512fff1e  ............../Q
171  //  0000000000008d44 ea00b1f9e92d0090 e3a070fcef000000  ......-..p......
172  // On 32-bit machines, there are still 16 bytes per line but addresses and
173  // words are of course presented differently.
174  uintptr_t* data_ptr = data;
175  size_t current = 0;
176  size_t total_bytes = start + bytes;
177  for (size_t line = 0; line < MEMORY_BYTES_TO_DUMP / MEMORY_BYTES_PER_LINE; line++) {
178    std::string logline;
179    android::base::StringAppendF(&logline, "    %" PRIPTR, addr);
180
181    addr += MEMORY_BYTES_PER_LINE;
182    std::string ascii;
183    for (size_t i = 0; i < MEMORY_BYTES_PER_LINE / sizeof(uintptr_t); i++) {
184      if (current >= start && current + sizeof(uintptr_t) <= total_bytes) {
185        android::base::StringAppendF(&logline, " %" PRIPTR, *data_ptr);
186
187        // Fill out the ascii string from the data.
188        uint8_t* ptr = reinterpret_cast<uint8_t*>(data_ptr);
189        for (size_t val = 0; val < sizeof(uintptr_t); val++, ptr++) {
190          if (*ptr >= 0x20 && *ptr < 0x7f) {
191            ascii += *ptr;
192          } else {
193            ascii += '.';
194          }
195        }
196        data_ptr++;
197      } else {
198        logline += ' ' + std::string(sizeof(uintptr_t) * 2, '-');
199        ascii += std::string(sizeof(uintptr_t), '.');
200      }
201      current += sizeof(uintptr_t);
202    }
203    _LOG(log, logtype::MEMORY, "%s  %s\n", logline.c_str(), ascii.c_str());
204  }
205}
206
207void read_with_default(const char* path, char* buf, size_t len, const char* default_value) {
208  android::base::unique_fd fd(open(path, O_RDONLY));
209  if (fd != -1) {
210    int rc = TEMP_FAILURE_RETRY(read(fd.get(), buf, len - 1));
211    if (rc != -1) {
212      buf[rc] = '\0';
213
214      // Trim trailing newlines.
215      if (rc > 0 && buf[rc - 1] == '\n') {
216        buf[rc - 1] = '\0';
217      }
218      return;
219    }
220  }
221  strcpy(buf, default_value);
222}
223