From 48760f6960ffa2e7dc8411d6a28c47bc961a2000 Mon Sep 17 00:00:00 2001
From: Andreas Gampe <agampe@google.com>
Date: Mon, 12 Jun 2017 10:43:05 -0700
Subject: [PATCH] Binder: Add more logging on Error

Try to add the Error's message to the abort, so that it shows up
when the logcat is missing.

Sample message:

'jni_internal.cc:508] JNI FatalError called: java.lang.Error thrown during binder transaction: java.lang.LinkageError: This is a test.'

(cherry picked from commit 58383ba095f552a58ed416736fe049126c647ffd)

Bug: 62514767
Test: m
Change-Id: I12026bb7a8ec9438db493f135ed5d0177187f702
---
 core/jni/android_util_Binder.cpp | 27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/core/jni/android_util_Binder.cpp b/core/jni/android_util_Binder.cpp
index de67c50e71959..26b00344b789d 100644
--- a/core/jni/android_util_Binder.cpp
+++ b/core/jni/android_util_Binder.cpp
@@ -29,6 +29,7 @@
 #include <sys/types.h>
 #include <unistd.h>
 
+#include <android-base/stringprintf.h>
 #include <binder/IInterface.h>
 #include <binder/IServiceManager.h>
 #include <binder/IPCThreadState.h>
@@ -194,10 +195,34 @@ static void report_exception(JNIEnv* env, jthrowable excep, const char* msg)
         /*
          * It's an Error: Reraise the exception and ask the runtime to abort.
          */
+
+        // Try to get the exception string. Sometimes logcat isn't available,
+        // so try to add it to the abort message.
+        std::string exc_msg = "(Unknown exception message)";
+        {
+            ScopedLocalRef<jclass> exc_class(env, env->GetObjectClass(excep));
+            jmethodID method_id = env->GetMethodID(exc_class.get(),
+                                                   "toString",
+                                                   "()Ljava/lang/String;");
+            ScopedLocalRef<jstring> jstr(
+                    env,
+                    reinterpret_cast<jstring>(
+                            env->CallObjectMethod(excep, method_id)));
+            env->ExceptionClear();  // Just for good measure.
+            if (jstr.get() != nullptr) {
+                ScopedUtfChars jstr_utf(env, jstr.get());
+                exc_msg = jstr_utf.c_str();
+            }
+        }
+
         env->Throw(excep);
         ALOGE("java.lang.Error thrown during binder transaction (stack trace follows) : ");
         env->ExceptionDescribe();
-        env->FatalError("java.lang.Error thrown during binder transaction.");
+
+        std::string error_msg = base::StringPrintf(
+                "java.lang.Error thrown during binder transaction: %s",
+                exc_msg.c_str());
+        env->FatalError(error_msg.c_str());
     }
 
 bail: