Fix segfault in JNIEnv function hooks for test

On newer JB builds, the JNINativeInterface struct appears to be held
in read-only memory so attempting to repoint individual function pointers
in it causes segfault. So instead we repoint the top-level struct pointer
to refer to our own copy held in read/write memory.

BUG=137348
TEST=JNIAndroidTest


Review URL: https://chromiumcodereview.appspot.com/10828050

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@148943 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 33 insertions, 22 deletions

diff --git a/base/android/jni_android_unittest.cc b/base/android/jni_android_unittest.cc
index 5f5165a..abecad7 100644
--- a/base/android/jni_android_unittest.cc
+++ b/base/android/jni_android_unittest.cc
@@ -1,9 +1,10 @@
-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Copyright (c) 2012 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 "base/android/jni_android.h"
 
+#include "base/at_exit.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace base {
@@ -21,14 +22,14 @@ const char* g_last_method;
 const char* g_last_jni_signature;
 jmethodID g_last_method_id;
 
-JNINativeInterface g_previous_functions = {0};
+const JNINativeInterface* g_previous_functions;
 
 jmethodID GetMethodIDWrapper(JNIEnv* env, jclass clazz, const char* method,
                              const char* jni_signature) {
   g_last_method = method;
   g_last_jni_signature = jni_signature;
-  g_last_method_id = g_previous_functions.GetMethodID(env, clazz, method,
-                                                      jni_signature);
+  g_last_method_id = g_previous_functions->GetMethodID(env, clazz, method,
+                                                       jni_signature);
   return g_last_method_id;
 }
 
@@ -38,15 +39,16 @@ class JNIAndroidTest : public testing::Test {
  protected:
   virtual void SetUp() {
     JNIEnv* env = AttachCurrentThread();
-    g_previous_functions = *env->functions;
-    JNINativeInterface* native_interface =
-        const_cast<JNINativeInterface*>(env->functions);
-    native_interface->GetMethodID = &GetMethodIDWrapper;
+    g_previous_functions = env->functions;
+    hooked_functions = *g_previous_functions;
+    env->functions = &hooked_functions;
+    hooked_functions.GetMethodID = &GetMethodIDWrapper;
   }
 
   virtual void TearDown() {
     JNIEnv* env = AttachCurrentThread();
-    *(const_cast<JNINativeInterface*>(env->functions)) = g_previous_functions;
+    env->functions = g_previous_functions;
+    Reset();
   }
 
   void Reset() {
@@ -54,6 +56,12 @@ class JNIAndroidTest : public testing::Test {
     g_last_jni_signature = 0;
     g_last_method_id = NULL;
   }
+  // Needed to cleanup the cached method map in the implementation between
+  // runs (e.g. if using --gtest_repeat)
+  base::ShadowingAtExitManager exit_manager;
+  // From JellyBean release, the instance of this struct provided in JNIEnv is
+  // read-only, so we deep copy it to allow individual functions to be hooked.
+  JNINativeInterface hooked_functions;
 };
 
 TEST_F(JNIAndroidTest, GetMethodIDFromClassNameCaching) {
diff --git a/base/android/scoped_java_ref_unittest.cc b/base/android/scoped_java_ref_unittest.cc
index f8bc675..36f253c 100644
--- a/base/android/scoped_java_ref_unittest.cc
+++ b/base/android/scoped_java_ref_unittest.cc
@@ -15,26 +15,26 @@ namespace {
 int g_local_refs = 0;
 int g_global_refs = 0;
 
-JNINativeInterface g_previous_functions = {0};
+const JNINativeInterface* g_previous_functions;
 
 jobject NewGlobalRef(JNIEnv* env, jobject obj) {
   ++g_global_refs;
-  return g_previous_functions.NewGlobalRef(env, obj);
+  return g_previous_functions->NewGlobalRef(env, obj);
 }
 
 void DeleteGlobalRef(JNIEnv* env, jobject obj) {
   --g_global_refs;
-  return g_previous_functions.DeleteGlobalRef(env, obj);
+  return g_previous_functions->DeleteGlobalRef(env, obj);
 }
 
 jobject NewLocalRef(JNIEnv* env, jobject obj) {
   ++g_local_refs;
-  return g_previous_functions.NewLocalRef(env, obj);
+  return g_previous_functions->NewLocalRef(env, obj);
 }
 
 void DeleteLocalRef(JNIEnv* env, jobject obj) {
   --g_local_refs;
-  return g_previous_functions.DeleteLocalRef(env, obj);
+  return g_previous_functions->DeleteLocalRef(env, obj);
 }
 }  // namespace
 
@@ -44,21 +44,24 @@ class ScopedJavaRefTest : public testing::Test {
     g_local_refs = 0;
     g_global_refs = 0;
     JNIEnv* env = AttachCurrentThread();
-    g_previous_functions = *env->functions;
+    g_previous_functions = env->functions;
+    hooked_functions = *g_previous_functions;
+    env->functions = &hooked_functions;
     // We inject our own functions in JNINativeInterface so we can keep track
     // of the reference counting ourselves.
-    JNINativeInterface* native_interface =
-        const_cast<JNINativeInterface*>(env->functions);
-    native_interface->NewGlobalRef = &NewGlobalRef;
-    native_interface->DeleteGlobalRef = &DeleteGlobalRef;
-    native_interface->NewLocalRef = &NewLocalRef;
-    native_interface->DeleteLocalRef = &DeleteLocalRef;
+    hooked_functions.NewGlobalRef = &NewGlobalRef;
+    hooked_functions.DeleteGlobalRef = &DeleteGlobalRef;
+    hooked_functions.NewLocalRef = &NewLocalRef;
+    hooked_functions.DeleteLocalRef = &DeleteLocalRef;
   }
 
   virtual void TearDown() {
     JNIEnv* env = AttachCurrentThread();
-    *(const_cast<JNINativeInterface*>(env->functions)) = g_previous_functions;
+    env->functions = g_previous_functions;
   }
+  // From JellyBean release, the instance of this struct provided in JNIEnv is
+  // read-only, so we deep copy it to allow individual functions to be hooked.
+  JNINativeInterface hooked_functions;
 };
 
 // The main purpose of this is testing the various conversions compile.