tools/lock_agent/agent.cpp - LeafOS-Project/android_frameworks_base - Gitiles

 /*
  * Copyright (C) 2019 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 #include <cstring>
 #include <iostream>
 #include <memory>
 #include <sstream>

 #include <unistd.h>

 #include <jni.h>

 #include <jvmti.h>

 #include <android-base/file.h>
 #include <android-base/logging.h>
 #include <android-base/macros.h>
 #include <android-base/strings.h>
 #include <android-base/unique_fd.h>

 #include <fcntl.h>
 #include <sys/stat.h>
 #include <sys/wait.h>

 #include <nativehelper/scoped_utf_chars.h>

 // We need dladdr.
 #if !defined(__APPLE__) && !defined(_WIN32)
 #ifndef _GNU_SOURCE
 #define _GNU_SOURCE
 #define DEFINED_GNU_SOURCE
 #endif
 #include <dlfcn.h>
 #ifdef DEFINED_GNU_SOURCE
 #undef _GNU_SOURCE
 #undef DEFINED_GNU_SOURCE
 #endif
 #endif

 // Slicer's headers have code that triggers these warnings. b/65298177
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wunused-parameter"
 #pragma clang diagnostic ignored "-Wsign-compare"

 #include <slicer/dex_ir.h>
 #include <slicer/code_ir.h>
 #include <slicer/dex_bytecode.h>
 #include <slicer/dex_ir_builder.h>
 #include <slicer/writer.h>
 #include <slicer/reader.h>

 #pragma clang diagnostic pop

 namespace {

 JavaVM* gJavaVM = nullptr;
 bool gForkCrash = false;
 bool gJavaCrash = false;

 // Converts a class name to a type descriptor
 // (ex. "java.lang.String" to "Ljava/lang/String;")
 std::string classNameToDescriptor(const char* className) {
     std::stringstream ss;
     ss << "L";
     for (auto p = className; *p != '\0'; ++p) {
         ss << (*p == '.' ? '/' : *p);
     }
     ss << ";";
     return ss.str();
 }

 using namespace dex;
 using namespace lir;

 class Transformer {
 public:
     explicit Transformer(std::shared_ptr<ir::DexFile> dexIr) : dexIr_(dexIr) {}

     bool transform() {
         bool classModified = false;

         std::unique_ptr<ir::Builder> builder;

         for (auto& method : dexIr_->encoded_methods) {
             // Do not look into abstract/bridge/native/synthetic methods.
             if ((method->access_flags & (kAccAbstract | kAccBridge | kAccNative | kAccSynthetic))
                     != 0) {
                 continue;
             }

             struct HookVisitor: public Visitor {
                 HookVisitor(Transformer* transformer, CodeIr* c_ir)
                         : transformer(transformer), cIr(c_ir) {
                 }

                 bool Visit(Bytecode* bytecode) override {
                     if (bytecode->opcode == OP_MONITOR_ENTER) {
                         insertHook(bytecode, true,
                                 reinterpret_cast<VReg*>(bytecode->operands[0])->reg);
                         return true;
                     }
                     if (bytecode->opcode == OP_MONITOR_EXIT) {
                         insertHook(bytecode, false,
                                 reinterpret_cast<VReg*>(bytecode->operands[0])->reg);
                         return true;
                     }
                     return false;
                 }

                 void insertHook(lir::Instruction* before, bool pre, u4 reg) {
                     transformer->preparePrePost();
                     transformer->addCall(cIr, before, OP_INVOKE_STATIC_RANGE,
                             transformer->hookType_, pre ? "preLock" : "postLock",
                             transformer->voidType_, transformer->objectType_, reg);
                     myModified = true;
                 }

                 Transformer* transformer;
                 CodeIr* cIr;
                 bool myModified = false;
             };

             CodeIr c(method.get(), dexIr_);
             bool methodModified = false;

             HookVisitor visitor(this, &c);
             for (auto it = c.instructions.begin(); it != c.instructions.end(); ++it) {
                 lir::Instruction* fi = *it;
                 fi->Accept(&visitor);
             }
             methodModified |= visitor.myModified;

             if (methodModified) {
                 classModified = true;
                 c.Assemble();
             }
         }

         return classModified;
     }

 private:
     void preparePrePost() {
         // Insert "void LockHook.(pre|post)(Object o)."

         prepareBuilder();

         if (voidType_ == nullptr) {
             voidType_ = builder_->GetType("V");
         }
         if (hookType_ == nullptr) {
             hookType_ = builder_->GetType("Lcom/android/lock_checker/LockHook;");
         }
         if (objectType_ == nullptr) {
             objectType_ = builder_->GetType("Ljava/lang/Object;");
         }
     }

     void prepareBuilder() {
         if (builder_ == nullptr) {
             builder_ = std::unique_ptr<ir::Builder>(new ir::Builder(dexIr_));
         }
     }

     static void addInst(CodeIr* cIr, lir::Instruction* instructionAfter, Opcode opcode,
             const std::list<Operand*>& operands) {
         auto instruction = cIr->Alloc<Bytecode>();

         instruction->opcode = opcode;

         for (auto it = operands.begin(); it != operands.end(); it++) {
             instruction->operands.push_back(*it);
         }

         cIr->instructions.InsertBefore(instructionAfter, instruction);
     }

     void addCall(CodeIr* cIr, lir::Instruction* instructionAfter, Opcode opcode, ir::Type* type,
             const char* methodName, ir::Type* returnType,
             const std::vector<ir::Type*>& types, const std::list<int>& regs) {
         auto proto = builder_->GetProto(returnType, builder_->GetTypeList(types));
         auto method = builder_->GetMethodDecl(builder_->GetAsciiString(methodName), proto, type);

         VRegList* paramRegs = cIr->Alloc<VRegList>();
         for (auto it = regs.begin(); it != regs.end(); it++) {
             paramRegs->registers.push_back(*it);
         }

         addInst(cIr, instructionAfter, opcode,
                 { paramRegs, cIr->Alloc<Method>(method, method->orig_index) });
     }

     void addCall(CodeIr* cIr, lir::Instruction* instructionAfter, Opcode opcode, ir::Type* type,
             const char* methodName, ir::Type* returnType, ir::Type* paramType,
             u4 paramVReg) {
         auto proto = builder_->GetProto(returnType, builder_->GetTypeList( { paramType }));
         auto method = builder_->GetMethodDecl(builder_->GetAsciiString(methodName), proto, type);

         VRegRange* args = cIr->Alloc<VRegRange>(paramVReg, 1);

         addInst(cIr, instructionAfter, opcode,
                 { args, cIr->Alloc<Method>(method, method->orig_index) });
     }

     std::shared_ptr<ir::DexFile> dexIr_;
     std::unique_ptr<ir::Builder> builder_;

     ir::Type* voidType_ = nullptr;
     ir::Type* hookType_ = nullptr;
     ir::Type* objectType_ = nullptr;
 };

 std::pair<dex::u1*, size_t> maybeTransform(const char* name, size_t classDataLen,
         const unsigned char* classData, dex::Writer::Allocator* allocator) {
     // Isolate byte code of class class. This is needed as Android usually gives us more
     // than the class we need.
     dex::Reader reader(classData, classDataLen);

     dex::u4 index = reader.FindClassIndex(classNameToDescriptor(name).c_str());
     CHECK_NE(index, kNoIndex);
     reader.CreateClassIr(index);
     std::shared_ptr<ir::DexFile> ir = reader.GetIr();

     {
         Transformer transformer(ir);
         if (!transformer.transform()) {
             return std::make_pair(nullptr, 0);
         }
     }

     size_t new_size;
     dex::Writer writer(ir);
     dex::u1* newClassData = writer.CreateImage(allocator, &new_size);
     return std::make_pair(newClassData, new_size);
 }

 void transformHook(jvmtiEnv* jvmtiEnv, JNIEnv* env ATTRIBUTE_UNUSED,
         jclass classBeingRedefined ATTRIBUTE_UNUSED, jobject loader, const char* name,
         jobject protectionDomain ATTRIBUTE_UNUSED, jint classDataLen,
         const unsigned char* classData, jint* newClassDataLen, unsigned char** newClassData) {
     // Even reading the classData array is expensive as the data is only generated when the
     // memory is touched. Hence call JvmtiAgent#shouldTransform to check if we need to transform
     // the class.

     // Skip bootclasspath classes. TODO: Make this configurable.
     if (loader == nullptr) {
         return;
     }

     // Do not look into java.* classes. Should technically be filtered by above, but when that's
     // configurable have this.
     if (strncmp("java", name, 4) == 0) {
         return;
     }

     // Do not look into our Java classes.
     if (strncmp("com/android/lock_checker", name, 24) == 0) {
         return;
     }

     class JvmtiAllocator: public dex::Writer::Allocator {
     public:
         explicit JvmtiAllocator(::jvmtiEnv* jvmti) :
                 jvmti_(jvmti) {
         }

         void* Allocate(size_t size) override {
             unsigned char* res = nullptr;
             jvmti_->Allocate(size, &res);
             return res;
         }

         void Free(void* ptr) override {
             jvmti_->Deallocate(reinterpret_cast<unsigned char*>(ptr));
         }

     private:
         ::jvmtiEnv* jvmti_;
     };
     JvmtiAllocator allocator(jvmtiEnv);
     std::pair<dex::u1*, size_t> result = maybeTransform(name, classDataLen, classData,
             &allocator);

     if (result.second > 0) {
         *newClassData = result.first;
         *newClassDataLen = static_cast<jint>(result.second);
     }
 }

 void dataDumpRequestHook(jvmtiEnv* jvmtiEnv ATTRIBUTE_UNUSED) {
     if (gJavaVM == nullptr) {
         LOG(ERROR) << "No JavaVM for dump";
         return;
     }
     JNIEnv* env;
     if (gJavaVM->GetEnv(reinterpret_cast<void**>(&env), JNI_VERSION_1_6) != JNI_OK) {
         LOG(ERROR) << "Could not get env for dump";
         return;
     }
     jclass lockHookClass = env->FindClass("com/android/lock_checker/LockHook");
     if (lockHookClass == nullptr) {
         env->ExceptionClear();
         LOG(ERROR) << "Could not find LockHook class";
         return;
     }
     jmethodID dumpId = env->GetStaticMethodID(lockHookClass, "dump", "()V");
     if (dumpId == nullptr) {
         env->ExceptionClear();
         LOG(ERROR) << "Could not find LockHook.dump";
         return;
     }
     env->CallStaticVoidMethod(lockHookClass, dumpId);
     env->ExceptionClear();
 }

 // A function for dladdr to search.
 extern "C" __attribute__ ((visibility ("default"))) void lock_agent_tag_fn() {
 }

 bool fileExists(const std::string& path) {
     struct stat statBuf;
     int rc = stat(path.c_str(), &statBuf);
     return rc == 0;
 }

 std::string findLockAgentJar() {
     // Check whether the jar is located next to the agent's so.
 #ifndef __APPLE__
     {
         Dl_info info;
         if (dladdr(reinterpret_cast<const void*>(&lock_agent_tag_fn), /* out */ &info) != 0) {
             std::string lockAgentSoPath = info.dli_fname;
             std::string dir = android::base::Dirname(lockAgentSoPath);
             std::string lockAgentJarPath = dir + "/" + "lockagent.jar";
             if (fileExists(lockAgentJarPath)) {
                 return lockAgentJarPath;
             }
         } else {
             LOG(ERROR) << "dladdr failed";
         }
     }
 #endif

     std::string sysFrameworkPath = "/system/framework/lockagent.jar";
     if (fileExists(sysFrameworkPath)) {
         return sysFrameworkPath;
     }

     std::string relPath = "lockagent.jar";
     if (fileExists(relPath)) {
         return relPath;
     }

     return "";
 }

 void prepareHook(jvmtiEnv* env) {
     // Inject the agent Java code.
     {
         std::string path = findLockAgentJar();
         if (path.empty()) {
             LOG(FATAL) << "Could not find lockagent.jar";
         }
         LOG(INFO) << "Will load Java parts from " << path;
         jvmtiError res = env->AddToBootstrapClassLoaderSearch(path.c_str());
         if (res != JVMTI_ERROR_NONE) {
             LOG(FATAL) << "Could not add lockagent from " << path << " to boot classpath: " << res;
         }
     }

     jvmtiCapabilities caps;
     memset(&caps, 0, sizeof(caps));
     caps.can_retransform_classes = 1;

     if (env->AddCapabilities(&caps) != JVMTI_ERROR_NONE) {
         LOG(FATAL) << "Could not add caps";
     }

     jvmtiEventCallbacks cb;
     memset(&cb, 0, sizeof(cb));
     cb.ClassFileLoadHook = transformHook;
     cb.DataDumpRequest = dataDumpRequestHook;

     if (env->SetEventCallbacks(&cb, sizeof(cb)) != JVMTI_ERROR_NONE) {
         LOG(FATAL) << "Could not set cb";
     }

     if (env->SetEventNotificationMode(JVMTI_ENABLE, JVMTI_EVENT_CLASS_FILE_LOAD_HOOK, nullptr)
             != JVMTI_ERROR_NONE) {
         LOG(FATAL) << "Could not enable events";
     }
     if (env->SetEventNotificationMode(JVMTI_ENABLE, JVMTI_EVENT_DATA_DUMP_REQUEST, nullptr)
             != JVMTI_ERROR_NONE) {
         LOG(FATAL) << "Could not enable events";
     }
 }

 jint attach(JavaVM* vm, char* options, void* reserved ATTRIBUTE_UNUSED) {
     gJavaVM = vm;

     jvmtiEnv* env;
     jint jvmError = vm->GetEnv(reinterpret_cast<void**>(&env), JVMTI_VERSION_1_2);
     if (jvmError != JNI_OK) {
         return jvmError;
     }

     prepareHook(env);

     std::vector<std::string> config = android::base::Split(options, ",");
     for (const std::string& c : config) {
         if (c == "native_crash") {
             gForkCrash = true;
         } else if (c == "java_crash") {
             gJavaCrash = true;
         }
     }

     return JVMTI_ERROR_NONE;
 }

 extern "C" JNIEXPORT
 jboolean JNICALL Java_com_android_lock_1checker_LockHook_getNativeHandlingConfig(JNIEnv*, jclass) {
     return gForkCrash ? JNI_TRUE : JNI_FALSE;
 }

 extern "C" JNIEXPORT jboolean JNICALL
 Java_com_android_lock_1checker_LockHook_getSimulateCrashConfig(JNIEnv*, jclass) {
     return gJavaCrash ? JNI_TRUE : JNI_FALSE;
 }

 extern "C" JNIEXPORT void JNICALL Java_com_android_lock_1checker_LockHook_nWtf(JNIEnv* env, jclass,
         jstring msg) {
     if (!gForkCrash || msg == nullptr) {
         return;
     }

     // Create a native crash with the given message. Decouple from the current crash to create a
     // tombstone but continue on.
     //
     // TODO: Once there are not so many reports, consider making this fatal for the calling process.
     ScopedUtfChars utf(env, msg);
     if (utf.c_str() == nullptr) {
         return;
     }
     const char* args[] = {
         "/system/bin/lockagent_crasher",
         utf.c_str(),
         nullptr
     };
     pid_t pid = fork();
     if (pid < 0) {
         return;
     }
     if (pid == 0) {
         // Double fork so we return quickly. Leave init to deal with the zombie.
         pid_t pid2 = fork();
         if (pid2 == 0) {
             execv(args[0], const_cast<char* const*>(args));
             _exit(1);
             __builtin_unreachable();
         }
         _exit(0);
         __builtin_unreachable();
     }
     int status;
     waitpid(pid, &status, 0);  // Ignore any results.
 }

 extern "C" JNIEXPORT jint JNICALL Agent_OnAttach(JavaVM* vm, char* options, void* reserved) {
     return attach(vm, options, reserved);
 }

 extern "C" JNIEXPORT jint JNICALL Agent_OnLoad(JavaVM* vm, char* options, void* reserved) {
     return attach(vm, options, reserved);
 }

 int locktest_main(int argc, char *argv[]) {
     if (argc != 3) {
         LOG(FATAL) << "Need two arguments: dex-file class-name";
     }
     struct stat statBuf;
     int rc = stat(argv[1], &statBuf);
     if (rc != 0) {
         PLOG(FATAL) << "Could not get file size for " << argv[1];
     }
     std::unique_ptr<char[]> data(new char[statBuf.st_size]);
     {
         android::base::unique_fd fd(open(argv[1], O_RDONLY));
         if (fd.get() == -1) {
             PLOG(FATAL) << "Could not open file " << argv[1];
         }
         if (!android::base::ReadFully(fd.get(), data.get(), statBuf.st_size)) {
             PLOG(FATAL) << "Could not read file " << argv[1];
         }
     }

     class NewDeleteAllocator: public dex::Writer::Allocator {
     public:
         explicit NewDeleteAllocator() {
         }

         void* Allocate(size_t size) override {
             return new char[size];
         }

         void Free(void* ptr) override {
             delete[] reinterpret_cast<char*>(ptr);
         }
     };
     NewDeleteAllocator allocator;

     std::pair<dex::u1*, size_t> result = maybeTransform(argv[2], statBuf.st_size,
             reinterpret_cast<unsigned char*>(data.get()), &allocator);

     if (result.second == 0) {
         LOG(INFO) << "No transformation";
         return 0;
     }

     std::string newName(argv[1]);
     newName.append(".new");

     {
         android::base::unique_fd fd(
                 open(newName.c_str(), O_CREAT | O_TRUNC | O_WRONLY, S_IRUSR | S_IWUSR));
         if (fd.get() == -1) {
             PLOG(FATAL) << "Could not open file " << newName;
         }
         if (!android::base::WriteFully(fd.get(), result.first, result.second)) {
             PLOG(FATAL) << "Could not write file " << newName;
         }
     }
     LOG(INFO) << "Transformed file written to " << newName;

     return 0;
 }

 }  // namespace

 int main(int argc, char *argv[]) {
     return locktest_main(argc, argv);
 }
	/*
	* Copyright (C) 2019 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	#include <cstring>
	#include <iostream>
	#include <memory>
	#include <sstream>

	#include <unistd.h>

	#include <jni.h>

	#include <jvmti.h>

	#include <android-base/file.h>
	#include <android-base/logging.h>
	#include <android-base/macros.h>
	#include <android-base/strings.h>
	#include <android-base/unique_fd.h>

	#include <fcntl.h>
	#include <sys/stat.h>
	#include <sys/wait.h>

	#include <nativehelper/scoped_utf_chars.h>

	// We need dladdr.
	#if !defined(__APPLE__) && !defined(_WIN32)
	#ifndef _GNU_SOURCE
	#define _GNU_SOURCE
	#define DEFINED_GNU_SOURCE
	#endif
	#include <dlfcn.h>
	#ifdef DEFINED_GNU_SOURCE
	#undef _GNU_SOURCE
	#undef DEFINED_GNU_SOURCE
	#endif
	#endif

	// Slicer's headers have code that triggers these warnings. b/65298177
	#pragma clang diagnostic push
	#pragma clang diagnostic ignored "-Wunused-parameter"
	#pragma clang diagnostic ignored "-Wsign-compare"

	#include <slicer/dex_ir.h>
	#include <slicer/code_ir.h>
	#include <slicer/dex_bytecode.h>
	#include <slicer/dex_ir_builder.h>
	#include <slicer/writer.h>
	#include <slicer/reader.h>

	#pragma clang diagnostic pop

	namespace {

	JavaVM* gJavaVM = nullptr;
	bool gForkCrash = false;
	bool gJavaCrash = false;

	// Converts a class name to a type descriptor
	// (ex. "java.lang.String" to "Ljava/lang/String;")
	std::string classNameToDescriptor(const char* className) {
	std::stringstream ss;
	ss << "L";
	for (auto p = className; *p != '\0'; ++p) {
	ss << (p == '.' ? '/' : p);
	}
	ss << ";";
	return ss.str();
	}

	using namespace dex;
	using namespace lir;

	class Transformer {
	public:
	explicit Transformer(std::shared_ptr<ir::DexFile> dexIr) : dexIr_(dexIr) {}

	bool transform() {
	bool classModified = false;

	std::unique_ptr<ir::Builder> builder;

	for (auto& method : dexIr_->encoded_methods) {
	// Do not look into abstract/bridge/native/synthetic methods.
	if ((method->access_flags & (kAccAbstract \| kAccBridge \| kAccNative \| kAccSynthetic))
	!= 0) {
	continue;
	}

	struct HookVisitor: public Visitor {
	HookVisitor(Transformer* transformer, CodeIr* c_ir)
	: transformer(transformer), cIr(c_ir) {
	}

	bool Visit(Bytecode* bytecode) override {
	if (bytecode->opcode == OP_MONITOR_ENTER) {
	insertHook(bytecode, true,
	reinterpret_cast<VReg*>(bytecode->operands[0])->reg);
	return true;
	}
	if (bytecode->opcode == OP_MONITOR_EXIT) {
	insertHook(bytecode, false,
	reinterpret_cast<VReg*>(bytecode->operands[0])->reg);
	return true;
	}
	return false;
	}

	void insertHook(lir::Instruction* before, bool pre, u4 reg) {
	transformer->preparePrePost();
	transformer->addCall(cIr, before, OP_INVOKE_STATIC_RANGE,
	transformer->hookType_, pre ? "preLock" : "postLock",
	transformer->voidType_, transformer->objectType_, reg);
	myModified = true;
	}

	Transformer* transformer;
	CodeIr* cIr;
	bool myModified = false;
	};

	CodeIr c(method.get(), dexIr_);
	bool methodModified = false;

	HookVisitor visitor(this, &c);
	for (auto it = c.instructions.begin(); it != c.instructions.end(); ++it) {
	lir::Instruction* fi = *it;
	fi->Accept(&visitor);
	}
	methodModified \|= visitor.myModified;

	if (methodModified) {
	classModified = true;
	c.Assemble();
	}
	}

	return classModified;
	}

	private:
	void preparePrePost() {
	// Insert "void LockHook.(pre\|post)(Object o)."

	prepareBuilder();

	if (voidType_ == nullptr) {
	voidType_ = builder_->GetType("V");
	}
	if (hookType_ == nullptr) {
	hookType_ = builder_->GetType("Lcom/android/lock_checker/LockHook;");
	}
	if (objectType_ == nullptr) {
	objectType_ = builder_->GetType("Ljava/lang/Object;");
	}
	}

	void prepareBuilder() {
	if (builder_ == nullptr) {
	builder_ = std::unique_ptr<ir::Builder>(new ir::Builder(dexIr_));
	}
	}

	static void addInst(CodeIr* cIr, lir::Instruction* instructionAfter, Opcode opcode,
	const std::list<Operand*>& operands) {
	auto instruction = cIr->Alloc<Bytecode>();

	instruction->opcode = opcode;

	for (auto it = operands.begin(); it != operands.end(); it++) {
	instruction->operands.push_back(*it);
	}

	cIr->instructions.InsertBefore(instructionAfter, instruction);
	}

	void addCall(CodeIr* cIr, lir::Instruction* instructionAfter, Opcode opcode, ir::Type* type,
	const char* methodName, ir::Type* returnType,
	const std::vector<ir::Type*>& types, const std::list<int>& regs) {
	auto proto = builder_->GetProto(returnType, builder_->GetTypeList(types));
	auto method = builder_->GetMethodDecl(builder_->GetAsciiString(methodName), proto, type);

	VRegList* paramRegs = cIr->Alloc<VRegList>();
	for (auto it = regs.begin(); it != regs.end(); it++) {
	paramRegs->registers.push_back(*it);
	}

	addInst(cIr, instructionAfter, opcode,
	{ paramRegs, cIr->Alloc<Method>(method, method->orig_index) });
	}

	void addCall(CodeIr* cIr, lir::Instruction* instructionAfter, Opcode opcode, ir::Type* type,
	const char* methodName, ir::Type* returnType, ir::Type* paramType,
	u4 paramVReg) {
	auto proto = builder_->GetProto(returnType, builder_->GetTypeList( { paramType }));
	auto method = builder_->GetMethodDecl(builder_->GetAsciiString(methodName), proto, type);

	VRegRange* args = cIr->Alloc<VRegRange>(paramVReg, 1);

	addInst(cIr, instructionAfter, opcode,
	{ args, cIr->Alloc<Method>(method, method->orig_index) });
	}

	std::shared_ptr<ir::DexFile> dexIr_;
	std::unique_ptr<ir::Builder> builder_;

	ir::Type* voidType_ = nullptr;
	ir::Type* hookType_ = nullptr;
	ir::Type* objectType_ = nullptr;
	};

	std::pair<dex::u1, size_t> maybeTransform(const char name, size_t classDataLen,
	const unsigned char* classData, dex::Writer::Allocator* allocator) {
	// Isolate byte code of class class. This is needed as Android usually gives us more
	// than the class we need.
	dex::Reader reader(classData, classDataLen);

	dex::u4 index = reader.FindClassIndex(classNameToDescriptor(name).c_str());
	CHECK_NE(index, kNoIndex);
	reader.CreateClassIr(index);
	std::shared_ptr<ir::DexFile> ir = reader.GetIr();

	{
	Transformer transformer(ir);
	if (!transformer.transform()) {
	return std::make_pair(nullptr, 0);
	}
	}

	size_t new_size;
	dex::Writer writer(ir);
	dex::u1* newClassData = writer.CreateImage(allocator, &new_size);
	return std::make_pair(newClassData, new_size);
	}

	void transformHook(jvmtiEnv* jvmtiEnv, JNIEnv* env ATTRIBUTE_UNUSED,
	jclass classBeingRedefined ATTRIBUTE_UNUSED, jobject loader, const char* name,
	jobject protectionDomain ATTRIBUTE_UNUSED, jint classDataLen,
	const unsigned char* classData, jint* newClassDataLen, unsigned char** newClassData) {
	// Even reading the classData array is expensive as the data is only generated when the
	// memory is touched. Hence call JvmtiAgent#shouldTransform to check if we need to transform
	// the class.

	// Skip bootclasspath classes. TODO: Make this configurable.
	if (loader == nullptr) {
	return;
	}

	// Do not look into java.* classes. Should technically be filtered by above, but when that's
	// configurable have this.
	if (strncmp("java", name, 4) == 0) {
	return;
	}

	// Do not look into our Java classes.
	if (strncmp("com/android/lock_checker", name, 24) == 0) {
	return;
	}

	class JvmtiAllocator: public dex::Writer::Allocator {
	public:
	explicit JvmtiAllocator(::jvmtiEnv* jvmti) :
	jvmti_(jvmti) {
	}

	void* Allocate(size_t size) override {
	unsigned char* res = nullptr;
	jvmti_->Allocate(size, &res);
	return res;
	}

	void Free(void* ptr) override {
	jvmti_->Deallocate(reinterpret_cast<unsigned char*>(ptr));
	}

	private:
	::jvmtiEnv* jvmti_;
	};
	JvmtiAllocator allocator(jvmtiEnv);
	std::pair<dex::u1*, size_t> result = maybeTransform(name, classDataLen, classData,
	&allocator);

	if (result.second > 0) {
	*newClassData = result.first;
	*newClassDataLen = static_cast<jint>(result.second);
	}
	}

	void dataDumpRequestHook(jvmtiEnv* jvmtiEnv ATTRIBUTE_UNUSED) {
	if (gJavaVM == nullptr) {
	LOG(ERROR) << "No JavaVM for dump";
	return;
	}
	JNIEnv* env;
	if (gJavaVM->GetEnv(reinterpret_cast<void**>(&env), JNI_VERSION_1_6) != JNI_OK) {
	LOG(ERROR) << "Could not get env for dump";
	return;
	}
	jclass lockHookClass = env->FindClass("com/android/lock_checker/LockHook");
	if (lockHookClass == nullptr) {
	env->ExceptionClear();
	LOG(ERROR) << "Could not find LockHook class";
	return;
	}
	jmethodID dumpId = env->GetStaticMethodID(lockHookClass, "dump", "()V");
	if (dumpId == nullptr) {
	env->ExceptionClear();
	LOG(ERROR) << "Could not find LockHook.dump";
	return;
	}
	env->CallStaticVoidMethod(lockHookClass, dumpId);
	env->ExceptionClear();
	}

	// A function for dladdr to search.
	extern "C" __attribute__ ((visibility ("default"))) void lock_agent_tag_fn() {
	}

	bool fileExists(const std::string& path) {
	struct stat statBuf;
	int rc = stat(path.c_str(), &statBuf);
	return rc == 0;
	}

	std::string findLockAgentJar() {
	// Check whether the jar is located next to the agent's so.
	#ifndef __APPLE__
	{
	Dl_info info;
	if (dladdr(reinterpret_cast<const void>(&lock_agent_tag_fn), / out */ &info) != 0) {
	std::string lockAgentSoPath = info.dli_fname;
	std::string dir = android::base::Dirname(lockAgentSoPath);
	std::string lockAgentJarPath = dir + "/" + "lockagent.jar";
	if (fileExists(lockAgentJarPath)) {
	return lockAgentJarPath;
	}
	} else {
	LOG(ERROR) << "dladdr failed";
	}
	}
	#endif

	std::string sysFrameworkPath = "/system/framework/lockagent.jar";
	if (fileExists(sysFrameworkPath)) {
	return sysFrameworkPath;
	}

	std::string relPath = "lockagent.jar";
	if (fileExists(relPath)) {
	return relPath;
	}

	return "";
	}

	void prepareHook(jvmtiEnv* env) {
	// Inject the agent Java code.
	{
	std::string path = findLockAgentJar();
	if (path.empty()) {
	LOG(FATAL) << "Could not find lockagent.jar";
	}
	LOG(INFO) << "Will load Java parts from " << path;
	jvmtiError res = env->AddToBootstrapClassLoaderSearch(path.c_str());
	if (res != JVMTI_ERROR_NONE) {
	LOG(FATAL) << "Could not add lockagent from " << path << " to boot classpath: " << res;
	}
	}

	jvmtiCapabilities caps;
	memset(&caps, 0, sizeof(caps));
	caps.can_retransform_classes = 1;

	if (env->AddCapabilities(&caps) != JVMTI_ERROR_NONE) {
	LOG(FATAL) << "Could not add caps";
	}

	jvmtiEventCallbacks cb;
	memset(&cb, 0, sizeof(cb));
	cb.ClassFileLoadHook = transformHook;
	cb.DataDumpRequest = dataDumpRequestHook;

	if (env->SetEventCallbacks(&cb, sizeof(cb)) != JVMTI_ERROR_NONE) {
	LOG(FATAL) << "Could not set cb";
	}

	if (env->SetEventNotificationMode(JVMTI_ENABLE, JVMTI_EVENT_CLASS_FILE_LOAD_HOOK, nullptr)
	!= JVMTI_ERROR_NONE) {
	LOG(FATAL) << "Could not enable events";
	}
	if (env->SetEventNotificationMode(JVMTI_ENABLE, JVMTI_EVENT_DATA_DUMP_REQUEST, nullptr)
	!= JVMTI_ERROR_NONE) {
	LOG(FATAL) << "Could not enable events";
	}
	}

	jint attach(JavaVM* vm, char* options, void* reserved ATTRIBUTE_UNUSED) {
	gJavaVM = vm;

	jvmtiEnv* env;
	jint jvmError = vm->GetEnv(reinterpret_cast<void**>(&env), JVMTI_VERSION_1_2);
	if (jvmError != JNI_OK) {
	return jvmError;
	}

	prepareHook(env);

	std::vector<std::string> config = android::base::Split(options, ",");
	for (const std::string& c : config) {
	if (c == "native_crash") {
	gForkCrash = true;
	} else if (c == "java_crash") {
	gJavaCrash = true;
	}
	}

	return JVMTI_ERROR_NONE;
	}

	extern "C" JNIEXPORT
	jboolean JNICALL Java_com_android_lock_1checker_LockHook_getNativeHandlingConfig(JNIEnv*, jclass) {
	return gForkCrash ? JNI_TRUE : JNI_FALSE;
	}

	extern "C" JNIEXPORT jboolean JNICALL
	Java_com_android_lock_1checker_LockHook_getSimulateCrashConfig(JNIEnv*, jclass) {
	return gJavaCrash ? JNI_TRUE : JNI_FALSE;
	}

	extern "C" JNIEXPORT void JNICALL Java_com_android_lock_1checker_LockHook_nWtf(JNIEnv* env, jclass,
	jstring msg) {
	if (!gForkCrash \|\| msg == nullptr) {
	return;
	}

	// Create a native crash with the given message. Decouple from the current crash to create a
	// tombstone but continue on.
	//
	// TODO: Once there are not so many reports, consider making this fatal for the calling process.
	ScopedUtfChars utf(env, msg);
	if (utf.c_str() == nullptr) {
	return;
	}
	const char* args[] = {
	"/system/bin/lockagent_crasher",
	utf.c_str(),
	nullptr
	};
	pid_t pid = fork();
	if (pid < 0) {
	return;
	}
	if (pid == 0) {
	// Double fork so we return quickly. Leave init to deal with the zombie.
	pid_t pid2 = fork();
	if (pid2 == 0) {
	execv(args[0], const_cast<char* const*>(args));
	_exit(1);
	__builtin_unreachable();
	}
	_exit(0);
	__builtin_unreachable();
	}
	int status;
	waitpid(pid, &status, 0); // Ignore any results.
	}

	extern "C" JNIEXPORT jint JNICALL Agent_OnAttach(JavaVM* vm, char* options, void* reserved) {
	return attach(vm, options, reserved);
	}

	extern "C" JNIEXPORT jint JNICALL Agent_OnLoad(JavaVM* vm, char* options, void* reserved) {
	return attach(vm, options, reserved);
	}

	int locktest_main(int argc, char *argv[]) {
	if (argc != 3) {
	LOG(FATAL) << "Need two arguments: dex-file class-name";
	}
	struct stat statBuf;
	int rc = stat(argv[1], &statBuf);
	if (rc != 0) {
	PLOG(FATAL) << "Could not get file size for " << argv[1];
	}
	std::unique_ptr<char[]> data(new char[statBuf.st_size]);
	{
	android::base::unique_fd fd(open(argv[1], O_RDONLY));
	if (fd.get() == -1) {
	PLOG(FATAL) << "Could not open file " << argv[1];
	}
	if (!android::base::ReadFully(fd.get(), data.get(), statBuf.st_size)) {
	PLOG(FATAL) << "Could not read file " << argv[1];
	}
	}

	class NewDeleteAllocator: public dex::Writer::Allocator {
	public:
	explicit NewDeleteAllocator() {
	}

	void* Allocate(size_t size) override {
	return new char[size];
	}

	void Free(void* ptr) override {
	delete[] reinterpret_cast<char*>(ptr);
	}
	};
	NewDeleteAllocator allocator;

	std::pair<dex::u1*, size_t> result = maybeTransform(argv[2], statBuf.st_size,
	reinterpret_cast<unsigned char*>(data.get()), &allocator);

	if (result.second == 0) {
	LOG(INFO) << "No transformation";
	return 0;
	}

	std::string newName(argv[1]);
	newName.append(".new");

	{
	android::base::unique_fd fd(
	open(newName.c_str(), O_CREAT \| O_TRUNC \| O_WRONLY, S_IRUSR \| S_IWUSR));
	if (fd.get() == -1) {
	PLOG(FATAL) << "Could not open file " << newName;
	}
	if (!android::base::WriteFully(fd.get(), result.first, result.second)) {
	PLOG(FATAL) << "Could not write file " << newName;
	}
	}
	LOG(INFO) << "Transformed file written to " << newName;

	return 0;
	}

	} // namespace

	int main(int argc, char *argv[]) {
	return locktest_main(argc, argv);
	}