Android: Switch crazy linker to use implicit JNI registration

Hoping that this will resolve kitkat crashes where the JNI is
looking for a LegacyLinker method on the Linker class (see bug).

Bug: 849554
Change-Id: I11389b76142ead6281194cf6f363c8783d3ddbbc
Reviewed-on: https://chromium-review.googlesource.com/1088875
Commit-Queue: agrieve <agrieve@chromium.org>
Reviewed-by: Egor Pasko <pasko@chromium.org>
Cr-Commit-Position: refs/heads/master@{#565001}

base/android/linker/BUILD.gn

@@ -18,6 +18,11 @@ shared_library("chromium_android_linker") {
   #   '<(android_ndk_root)/crazy_linker.gyp:crazy_linker'
   # However, we use our own fork.  See bug 384700.
   deps = [
+    "//build:buildflag_header_h",
     "//third_party/android_crazy_linker",
   ]
+
+  # Export JNI symbols.
+  configs -= [ "//build/config/android:hide_all_but_jni_onload" ]
+  configs += [ "//build/config/android:hide_all_but_jni" ]
 }

base/android/linker/legacy_linker_jni.cc

@@ -181,11 +181,13 @@ bool ZipLibraryOpener::Open(crazy_library_t** library,
 // |library_info| is a LibInfo handle used to communicate information
 // with the Java side.
 // Return true on success.
-jboolean LoadLibrary(JNIEnv* env,
-                     jclass clazz,
-                     jstring library_name,
-                     jlong load_address,
-                     jobject lib_info_obj) {
+JNI_GENERATOR_EXPORT jboolean
+Java_org_chromium_base_library_1loader_LegacyLinker_nativeLoadLibrary(
+    JNIEnv* env,
+    jclass clazz,
+    jstring library_name,
+    jlong load_address,
+    jobject lib_info_obj) {
   String lib_name(env, library_name);
   FileLibraryOpener opener;
 
@@ -218,12 +220,14 @@ jboolean LoadLibrary(JNIEnv* env,
 // |library_info| is a LibInfo handle used to communicate information
 // with the Java side.
 // Returns true on success.
-jboolean LoadLibraryInZipFile(JNIEnv* env,
-                              jclass clazz,
-                              jstring zipfile_name,
-                              jstring library_name,
-                              jlong load_address,
-                              jobject lib_info_obj) {
+JNI_GENERATOR_EXPORT jboolean
+Java_org_chromium_base_library_1loader_LegacyLinker_nativeLoadLibraryInZipFile(
+    JNIEnv* env,
+    jclass clazz,
+    jstring zipfile_name,
+    jstring library_name,
+    jlong load_address,
+    jobject lib_info_obj) {
   String zipfile_name_str(env, zipfile_name);
   String lib_name(env, library_name);
   ZipLibraryOpener opener(zipfile_name_str.c_str());
@@ -260,7 +264,11 @@ static JavaCallbackBindings_class s_java_callback_bindings;
 // |clazz| is the static class handle for org.chromium.base.Linker,
 // and is ignored here.
 // |arg| is a pointer to an allocated crazy_callback_t, deleted after use.
-void RunCallbackOnUiThread(JNIEnv* env, jclass clazz, jlong arg) {
+JNI_GENERATOR_EXPORT void
+Java_org_chromium_base_library_1loader_LegacyLinker_nativeRunCallbackOnUiThread(
+    JNIEnv* env,
+    jclass clazz,
+    jlong arg) {
   crazy_callback_t* callback = reinterpret_cast<crazy_callback_t*>(arg);
 
   LOG_INFO("Called back from java with handler %p, opaque %p",
@@ -319,11 +327,13 @@ static bool PostForLaterExecution(crazy_callback_t* callback_request,
   return true;
 }
 
-jboolean CreateSharedRelro(JNIEnv* env,
-                           jclass clazz,
-                           jstring library_name,
-                           jlong load_address,
-                           jobject lib_info_obj) {
+JNI_GENERATOR_EXPORT jboolean
+Java_org_chromium_base_library_1loader_LegacyLinker_nativeCreateSharedRelro(
+    JNIEnv* env,
+    jclass clazz,
+    jstring library_name,
+    jlong load_address,
+    jobject lib_info_obj) {
   String lib_name(env, library_name);
 
   LOG_INFO("Called for %s", lib_name.c_str());
@@ -362,10 +372,12 @@ jboolean CreateSharedRelro(JNIEnv* env,
   return true;
 }
 
-jboolean UseSharedRelro(JNIEnv* env,
-                        jclass clazz,
-                        jstring library_name,
-                        jobject lib_info_obj) {
+JNI_GENERATOR_EXPORT jboolean
+Java_org_chromium_base_library_1loader_LegacyLinker_nativeUseSharedRelro(
+    JNIEnv* env,
+    jclass clazz,
+    jstring library_name,
+    jobject lib_info_obj) {
   String lib_name(env, library_name);
 
   LOG_INFO("Called for %s, lib_info_ref=%p", lib_name.c_str(), lib_info_obj);
@@ -400,50 +412,6 @@ jboolean UseSharedRelro(JNIEnv* env,
   return true;
 }
 
-const JNINativeMethod kNativeMethods[] = {
-    {"nativeLoadLibrary",
-     "("
-     "Ljava/lang/String;"
-     "J"
-     "Lorg/chromium/base/library_loader/Linker$LibInfo;"
-     ")"
-     "Z",
-     reinterpret_cast<void*>(&LoadLibrary)},
-    {"nativeLoadLibraryInZipFile",
-     "("
-     "Ljava/lang/String;"
-     "Ljava/lang/String;"
-     "J"
-     "Lorg/chromium/base/library_loader/Linker$LibInfo;"
-     ")"
-     "Z",
-     reinterpret_cast<void*>(&LoadLibraryInZipFile)},
-    {"nativeRunCallbackOnUiThread",
-     "("
-     "J"
-     ")"
-     "V",
-     reinterpret_cast<void*>(&RunCallbackOnUiThread)},
-    {"nativeCreateSharedRelro",
-     "("
-     "Ljava/lang/String;"
-     "J"
-     "Lorg/chromium/base/library_loader/Linker$LibInfo;"
-     ")"
-     "Z",
-     reinterpret_cast<void*>(&CreateSharedRelro)},
-    {"nativeUseSharedRelro",
-     "("
-     "Ljava/lang/String;"
-     "Lorg/chromium/base/library_loader/Linker$LibInfo;"
-     ")"
-     "Z",
-     reinterpret_cast<void*>(&UseSharedRelro)},
-};
-
-const size_t kNumNativeMethods =
-    sizeof(kNativeMethods) / sizeof(kNativeMethods[0]);
-
 }  // namespace
 
 bool LegacyLinkerJNIInit(JavaVM* vm, JNIEnv* env) {
@@ -461,10 +429,6 @@ bool LegacyLinkerJNIInit(JavaVM* vm, JNIEnv* env) {
                           &linker_class))
     return false;
 
-  LOG_INFO("Registering native methods");
-  if (env->RegisterNatives(linker_class, kNativeMethods, kNumNativeMethods) < 0)
-    return false;
-
   // Resolve and save the Java side Linker callback class and method.
   LOG_INFO("Resolving callback bindings");
   if (!s_java_callback_bindings.Init(env, linker_class)) {

base/android/linker/linker_jni.cc

@@ -147,7 +147,10 @@ bool InitStaticInt(JNIEnv* env,
 // then loads the library normally at any available address.
 // |env| is the current JNI environment handle, and |clazz| a class.
 // Returns the address selected by ASLR, or 0 on error.
-jlong GetRandomBaseLoadAddress(JNIEnv* env, jclass clazz) {
+JNI_GENERATOR_EXPORT jlong
+Java_org_chromium_base_library_1loader_Linker_nativeGetRandomBaseLoadAddress(
+    JNIEnv* env,
+    jclass clazz) {
   size_t bytes = kAddressSpaceReservationSize;
 
 #if RESERVE_BREAKPAD_GUARD_REGION
@@ -175,32 +178,8 @@ jlong GetRandomBaseLoadAddress(JNIEnv* env, jclass clazz) {
 
 namespace {
 
-const JNINativeMethod kNativeMethods[] = {
-    {"nativeGetRandomBaseLoadAddress",
-     "("
-     ")"
-     "J",
-     reinterpret_cast<void*>(&GetRandomBaseLoadAddress)},
-};
-
-const size_t kNumNativeMethods =
-    sizeof(kNativeMethods) / sizeof(kNativeMethods[0]);
-
 // JNI_OnLoad() initialization hook.
 bool LinkerJNIInit(JavaVM* vm, JNIEnv* env) {
-  LOG_INFO("Entering");
-
-  // Register native methods.
-  jclass linker_class;
-  if (!InitClassReference(env,
-                          "org/chromium/base/library_loader/Linker",
-                          &linker_class))
-    return false;
-
-  LOG_INFO("Registering native methods");
-  if (env->RegisterNatives(linker_class, kNativeMethods, kNumNativeMethods) < 0)
-    return false;
-
   // Find LibInfo field ids.
   LOG_INFO("Caching field IDs");
   if (!s_lib_info_fields.Init(env)) {

base/android/linker/linker_jni.h

@@ -21,6 +21,8 @@
 #include <stddef.h>
 #include <stdlib.h>
 
+#include "build/build_config.h"
+
 // Set this to 1 to enable debug traces to the Android log.
 // Note that LOG() from "base/logging.h" cannot be used, since it is
 // in base/ which hasn't been loaded yet.
@@ -48,6 +50,16 @@
 //   https://crbug.com/504410
 #define RESERVE_BREAKPAD_GUARD_REGION 1
 
+#if defined(ARCH_CPU_X86)
+// Dalvik JIT generated code doesn't guarantee 16-byte stack alignment on
+// x86 - use force_align_arg_pointer to realign the stack at the JNI
+// boundary. https://crbug.com/655248
+#define JNI_GENERATOR_EXPORT \
+  extern "C" __attribute__((visibility("default"), force_align_arg_pointer))
+#else
+#define JNI_GENERATOR_EXPORT extern "C" __attribute__((visibility("default")))
+#endif
+
 namespace chromium_android_linker {
 
 // Larger than the largest library we might attempt to load.