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 #include "build/build_config.h"
  15
  16 namespace {
  17
  18 const int kExceptionSignals[] = {
  19   SIGSEGV, SIGABRT, SIGFPE, SIGILL, SIGBUS
  20 };
  21
  22 struct sigaction old_handlers[arraysize(kExceptionSignals)];
  23
  24 bool crash_handler_registered;
  25
  26 std::string g_crash_msg;
  27
  28 const char* g_crash_msg_ptr;  // Avoid invoking STL magic in a signal handler.
  29
  30 void AwExceptionHandler(int sig, siginfo_t* info, void* uc) {
  31   if (g_crash_msg_ptr != NULL)
  32     __android_log_write(ANDROID_LOG_ERROR, "chromium", g_crash_msg_ptr);
  33
  34   // Detect if some buggy code in the embedder did reinstall the handler using
  35   // signal() instead of sigaction() (which would cause |info| to be invalid).
  36   struct sigaction cur_handler;
  37   if (sigaction(sig, NULL, &cur_handler) != 0 ||
  38       (cur_handler.sa_flags & SA_SIGINFO) == 0) {
  39     info = NULL;
  40   }
  41
  42   // We served our purpose. Now restore the old crash handlers. If the embedder
  43   // did register a custom crash handler, it will be invoked by the kernel after
  44   // this function returns. Otherwise, this will end up invoking the default
  45   // signal disposition.
  46   for (uint32_t i = 0; i < arraysize(kExceptionSignals); ++i) {
  47     if (sigaction(kExceptionSignals[i], &old_handlers[i], NULL) == -1) {
  48       signal(kExceptionSignals[i], SIG_DFL);
  49     }
  50   }
  51
  52   if ((info != NULL && info->si_pid) || sig == SIGABRT) {
  53     // This signal was triggered by somebody sending us the signal with kill().
  54     // In order to retrigger it, we have to queue a new signal by calling
  55     // kill() ourselves.  The special case (si_pid == 0 && sig == SIGABRT) is
  56     // due to the kernel sending a SIGABRT from a user request via SysRQ.
  57     if (syscall(__NR_tgkill, getpid(), syscall(__NR_gettid), sig) < 0) {
  58       // If we failed to kill ourselves resort to terminating uncleanly.
  59       exit(1);
  60     }
  61   }
  62 }
  63
  64 }  // namespace
  65
  66 namespace android_webview {
  67 namespace crash_handler {
  68
  69 void RegisterCrashHandler(const std::string& version) {
  70 #if defined(ARCH_CPU_X86_FAMILY)
  71   // Don't install signal handler on X86/64 because this breaks binary
  72   // translators that handle SIGSEGV in userspace and get chained after our
  73   // handler. See crbug.com/477444
  74   return;
  75 #endif
  76
  77   if (crash_handler_registered) {
  78     NOTREACHED();
  79     return;
  80   }
  81
  82   g_crash_msg = "### WebView " + version;
  83   g_crash_msg_ptr = g_crash_msg.c_str();
  84
  85   // Fail if unable to store all the old handlers.
  86   for (uint32_t i = 0; i < arraysize(kExceptionSignals); ++i) {
  87     if (sigaction(kExceptionSignals[i], NULL, &old_handlers[i]) == -1) {
  88       LOG(ERROR) << "Error while trying to retrieve old handler for signal "
  89                  << kExceptionSignals[i] << ")";
  90       return;
  91     }
  92   }
  93
  94   struct sigaction sa;
  95   memset(&sa, 0, sizeof(sa));
  96   sigemptyset(&sa.sa_mask);
  97
  98   // Mask all exception signals when we're handling one of them.
  99   for (uint32_t i = 0; i < arraysize(kExceptionSignals); ++i)
 100     sigaddset(&sa.sa_mask, kExceptionSignals[i]);
 101
 102   sa.sa_sigaction = AwExceptionHandler;
 103   sa.sa_flags = SA_ONSTACK | SA_SIGINFO;
 104
 105   for (uint32_t i = 0; i < arraysize(kExceptionSignals); ++i) {
 106     if (sigaction(kExceptionSignals[i], &sa, NULL) == -1) {
 107       // At this point it is impractical to back out changes, and so failure to
 108       // install a signal is intentionally ignored.
 109       LOG(ERROR) << "Error while overriding handler for signal "
 110                  << kExceptionSignals[i];
 111     }
 112   }
 113
 114   crash_handler_registered = true;
 115 }
 116
 117 }  // namespace crash_handler
 118 }  // namespace android_webview