android_webview/common/aw_crash_handler.cc

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "android_webview/common/aw_crash_handler.h"
   6
   7 #include <android/log.h>
   8 #include <signal.h>
   9 #include <sys/prctl.h>
  10 #include <sys/syscall.h>
  11 #include <unistd.h>
  12
  13 #include "base/logging.h"
  14
  15 namespace {
  16
  17 const int kExceptionSignals[] = {
  18   SIGSEGV, SIGABRT, SIGFPE, SIGILL, SIGBUS
  19 };
  20
  21 struct sigaction old_handlers[arraysize(kExceptionSignals)];
  22
  23 bool crash_handler_registered;
  24
  25 std::string g_crash_msg;
  26
  27 const char* g_crash_msg_ptr;  // Avoid invoking STL magic in a signal handler.
  28
  29 void AwExceptionHandler(int sig, siginfo_t* info, void* uc) {
  30   if (g_crash_msg_ptr != NULL)
  31     __android_log_write(ANDROID_LOG_ERROR, "chromium", g_crash_msg_ptr);
  32
  33   // Detect if some buggy code in the embedder did reinstall the handler using
  34   // signal() instead of sigaction() (which would cause |info| to be invalid).
  35   struct sigaction cur_handler;
  36   if (sigaction(sig, NULL, &cur_handler) != 0 ||
  37       (cur_handler.sa_flags & SA_SIGINFO) == 0) {
  38     info = NULL;
  39   }
  40
  41   // We served our purpose. Now restore the old crash handlers. If the embedder
  42   // did register a custom crash handler, it will be invoked by the kernel after
  43   // this function returns. Otherwise, this will end up invoking the default
  44   // signal disposition.
  45   for (uint32_t i = 0; i < arraysize(kExceptionSignals); ++i) {
  46     if (sigaction(kExceptionSignals[i], &old_handlers[i], NULL) == -1) {
  47       signal(kExceptionSignals[i], SIG_DFL);
  48     }
  49   }
  50
  51   if ((info != NULL && info->si_pid) || sig == SIGABRT) {
  52     // This signal was triggered by somebody sending us the signal with kill().
  53     // In order to retrigger it, we have to queue a new signal by calling
  54     // kill() ourselves.  The special case (si_pid == 0 && sig == SIGABRT) is
  55     // due to the kernel sending a SIGABRT from a user request via SysRQ.
  56     if (syscall(__NR_tgkill, getpid(), syscall(__NR_gettid), sig) < 0) {
  57       // If we failed to kill ourselves resort to terminating uncleanly.
  58       exit(1);
  59     }
  60   }
  61 }
  62
  63 }  // namespace
  64
  65 namespace android_webview {
  66 namespace crash_handler {
  67
  68 void RegisterCrashHandler(const std::string& version) {
  69   if (crash_handler_registered) {
  70     NOTREACHED();
  71     return;
  72   }
  73
  74   g_crash_msg = "### WebView " + version;
  75   g_crash_msg_ptr = g_crash_msg.c_str();
  76
  77   // Fail if unable to store all the old handlers.
  78   for (uint32_t i = 0; i < arraysize(kExceptionSignals); ++i) {
  79     if (sigaction(kExceptionSignals[i], NULL, &old_handlers[i]) == -1) {
  80       LOG(ERROR) << "Error while trying to retrieve old handler for signal "
  81                  << kExceptionSignals[i] << ")";
  82       return;
  83     }
  84   }
  85
  86   struct sigaction sa;
  87   memset(&sa, 0, sizeof(sa));
  88   sigemptyset(&sa.sa_mask);
  89
  90   // Mask all exception signals when we're handling one of them.
  91   for (uint32_t i = 0; i < arraysize(kExceptionSignals); ++i)
  92     sigaddset(&sa.sa_mask, kExceptionSignals[i]);
  93
  94   sa.sa_sigaction = AwExceptionHandler;
  95   sa.sa_flags = SA_ONSTACK | SA_SIGINFO;
  96
  97   for (uint32_t i = 0; i < arraysize(kExceptionSignals); ++i) {
  98     if (sigaction(kExceptionSignals[i], &sa, NULL) == -1) {
  99       // At this point it is impractical to back out changes, and so failure to
 100       // install a signal is intentionally ignored.
 101       LOG(ERROR) << "Error while overriding handler for signal "
 102                  << kExceptionSignals[i];
 103     }
 104   }
 105
 106   crash_handler_registered = true;
 107 }
 108
 109 }  // namespace crash_handler
 110 }  // namespace android_webview