[Android] Add minimalistic crash handler for WebView.

In the case of a crash this crash handler will print out on logcat the
version name and code. This is to reliabily determine the WebView
version in crash logs and pull the matching symbols.
This change requires a corresponding Android change to register the
crash handler in the very early stages (after LoadLibrary).

BUG=

Review URL: https://codereview.chromium.org/678763005

Cr-Commit-Position: refs/heads/master@{#301626}

2 files changed, 105 insertions, 0 deletions

diff --git a/android_webview/common/aw_crash_handler.cc b/android_webview/common/aw_crash_handler.cc
new file mode 100644
index 0000000..a637298
--- /dev/null
+++ b/android_webview/common/aw_crash_handler.cc
@@ -0,0 +1,87 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "android_webview/common/aw_crash_handler.h"
+
+#include <android/log.h>
+#include <signal.h>
+
+#include "base/logging.h"
+
+namespace {
+
+const int kExceptionSignals[] = {
+  SIGSEGV, SIGABRT, SIGFPE, SIGILL, SIGBUS
+};
+
+struct sigaction old_handlers[arraysize(kExceptionSignals)];
+
+bool crash_handler_registered;
+
+std::string g_crash_msg;
+
+const char* g_crash_msg_ptr;  // Avoid invoking STL magic in a signal handler.
+
+void AwExceptionHandler(int sig, siginfo_t* info, void* uc) {
+  if (g_crash_msg_ptr != NULL)
+    __android_log_write(ANDROID_LOG_ERROR, "chromium", g_crash_msg_ptr);
+
+  // We served our purpose. Now restore the old crash handlers. If the embedder
+  // did register a custom crash handler, it will be invoked by the kernel after
+  // this function returns. Otherwise, this will end up invoking the default
+  // signal disposition.
+  for (uint32_t i = 0; i < arraysize(kExceptionSignals); ++i) {
+    if (sigaction(kExceptionSignals[i], &old_handlers[i], NULL) == -1) {
+      signal(kExceptionSignals[i], SIG_DFL);
+    }
+  }
+}
+
+}  // namespace
+
+namespace android_webview {
+namespace crash_handler {
+
+void RegisterCrashHandler(const std::string& version) {
+  if (crash_handler_registered) {
+    NOTREACHED();
+    return;
+  }
+
+  g_crash_msg = "### WebView crash. " + version;
+  g_crash_msg_ptr = g_crash_msg.c_str();
+
+  // Fail if unable to store all the old handlers.
+  for (uint32_t i = 0; i < arraysize(kExceptionSignals); ++i) {
+    if (sigaction(kExceptionSignals[i], NULL, &old_handlers[i]) == -1) {
+      LOG(ERROR) << "Error while trying to retrieve old handler for signal "
+                 << kExceptionSignals[i] << ")";
+      return;
+    }
+  }
+
+  struct sigaction sa;
+  memset(&sa, 0, sizeof(sa));
+  sigemptyset(&sa.sa_mask);
+
+  for (uint32_t i = 0; i < arraysize(kExceptionSignals); ++i)
+    sigaddset(&sa.sa_mask, kExceptionSignals[i]);
+
+  sa.sa_sigaction = AwExceptionHandler;
+  sa.sa_flags = SA_ONSTACK | SA_SIGINFO;
+
+  for (uint32_t i = 0; i < arraysize(kExceptionSignals); ++i) {
+    if (sigaction(kExceptionSignals[i], &sa, NULL) == -1) {
+      // At this point it is impractical to back out changes, and so failure to
+      // install a signal is intentionally ignored.
+      LOG(ERROR) << "Error while overriding handler for signal "
+                 << kExceptionSignals[i];
+    }
+  }
+
+  crash_handler_registered = true;
+}
+
+}  // namespace crash_handler
+}  // namespace android_webview
diff --git a/android_webview/common/aw_crash_handler.h b/android_webview/common/aw_crash_handler.h
new file mode 100644
index 0000000..60e1d15
--- /dev/null
+++ b/android_webview/common/aw_crash_handler.h
@@ -0,0 +1,18 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef ANDROID_WEBVIEW_COMMON_AW_CRASH_HANDLER_H_
+#define ANDROID_WEBVIEW_COMMON_AW_CRASH_HANDLER_H_
+
+#include <string>
+
+namespace android_webview {
+namespace crash_handler {
+
+void RegisterCrashHandler(const std::string& version);
+
+}  // namespace crash_handler
+}  // namespace android_webview
+
+#endif  // ANDROID_WEBVIEW_COMMON_AW_CRASH_HANDLER_H_