/* * Copyright (C) 2017 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. */ #define LOG_TAG "SharedMemory" #include "core_jni_helpers.h" #include <cutils/ashmem.h> #include <utils/Log.h> #include <nativehelper/JNIHelp.h> #include <nativehelper/JniConstants.h> #include <nativehelper/ScopedLocalRef.h> #include <algorithm> #include <errno.h> #include <limits> #include <unistd.h> namespace { static void throwErrnoException(JNIEnv* env, const char* functionName, int error) { static jmethodID ctor = env->GetMethodID(JniConstants::errnoExceptionClass, "<init>", "(Ljava/lang/String;I)V"); ScopedLocalRef<jstring> detailMessage(env, env->NewStringUTF(functionName)); if (detailMessage.get() == NULL) { // Not really much we can do here. We're probably dead in the water, // but let's try to stumble on... env->ExceptionClear(); } jobject exception = env->NewObject(JniConstants::errnoExceptionClass, ctor, detailMessage.get(), error); env->Throw(reinterpret_cast<jthrowable>(exception)); } static jobject SharedMemory_create(JNIEnv* env, jobject, jstring jname, jint size) { // Name is optional so we can't use ScopedUtfChars for this as it throws NPE on null const char* name = jname ? env->GetStringUTFChars(jname, nullptr) : nullptr; int fd = ashmem_create_region(name, size); // Capture the error, if there is one, before calling ReleaseStringUTFChars int err = fd < 0 ? errno : 0; if (name) { env->ReleaseStringUTFChars(jname, name); } if (fd < 0) { throwErrnoException(env, "SharedMemory_create", err); return nullptr; } return jniCreateFileDescriptor(env, fd); } static jint SharedMemory_getSize(JNIEnv* env, jobject, jobject fileDescriptor) { int fd = jniGetFDFromFileDescriptor(env, fileDescriptor); if (!ashmem_valid(fd)) { return -1; } size_t size = ashmem_get_size_region(fd); return static_cast<jint>(std::min(size, static_cast<size_t>(std::numeric_limits<jint>::max()))); } static jint SharedMemory_setProt(JNIEnv* env, jobject, jobject fileDescriptor, jint prot) { int fd = jniGetFDFromFileDescriptor(env, fileDescriptor); int err = 0; if (ashmem_set_prot_region(fd, prot)) { err = errno; } return err; } static const JNINativeMethod methods[] = { {"nCreate", "(Ljava/lang/String;I)Ljava/io/FileDescriptor;", (void*)SharedMemory_create}, {"nGetSize", "(Ljava/io/FileDescriptor;)I", (void*)SharedMemory_getSize}, {"nSetProt", "(Ljava/io/FileDescriptor;I)I", (void*)SharedMemory_setProt}, }; } // anonymous namespace namespace android { int register_android_os_SharedMemory(JNIEnv* env) { return RegisterMethodsOrDie(env, "android/os/SharedMemory", methods, NELEM(methods)); } } // namespace android