1 /* 2 * Copyright (C) 2017 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #define LOG_TAG "SharedMemory" 18 19 #include "core_jni_helpers.h" 20 21 #include <cutils/ashmem.h> 22 #include <utils/Log.h> 23 #include <nativehelper/JNIHelp.h> 24 #include <nativehelper/JniConstants.h> 25 #include <nativehelper/ScopedLocalRef.h> 26 27 #include <algorithm> 28 #include <errno.h> 29 #include <limits> 30 #include <unistd.h> 31 32 namespace { 33 34 static void throwErrnoException(JNIEnv* env, const char* functionName, int error) { 35 static jmethodID ctor = env->GetMethodID(JniConstants::errnoExceptionClass, 36 "<init>", "(Ljava/lang/String;I)V"); 37 38 ScopedLocalRef<jstring> detailMessage(env, env->NewStringUTF(functionName)); 39 if (detailMessage.get() == NULL) { 40 // Not really much we can do here. We're probably dead in the water, 41 // but let's try to stumble on... 42 env->ExceptionClear(); 43 } 44 45 jobject exception = env->NewObject(JniConstants::errnoExceptionClass, ctor, 46 detailMessage.get(), error); 47 env->Throw(reinterpret_cast<jthrowable>(exception)); 48 } 49 50 static jobject SharedMemory_create(JNIEnv* env, jobject, jstring jname, jint size) { 51 52 // Name is optional so we can't use ScopedUtfChars for this as it throws NPE on null 53 const char* name = jname ? env->GetStringUTFChars(jname, nullptr) : nullptr; 54 55 int fd = ashmem_create_region(name, size); 56 57 // Capture the error, if there is one, before calling ReleaseStringUTFChars 58 int err = fd < 0 ? errno : 0; 59 60 if (name) { 61 env->ReleaseStringUTFChars(jname, name); 62 } 63 64 if (fd < 0) { 65 throwErrnoException(env, "SharedMemory_create", err); 66 return nullptr; 67 } 68 69 return jniCreateFileDescriptor(env, fd); 70 } 71 72 static jint SharedMemory_getSize(JNIEnv* env, jobject, jobject fileDescriptor) { 73 int fd = jniGetFDFromFileDescriptor(env, fileDescriptor); 74 if (!ashmem_valid(fd)) { 75 return -1; 76 } 77 size_t size = ashmem_get_size_region(fd); 78 return static_cast<jint>(std::min(size, static_cast<size_t>(std::numeric_limits<jint>::max()))); 79 } 80 81 static jint SharedMemory_setProt(JNIEnv* env, jobject, jobject fileDescriptor, jint prot) { 82 int fd = jniGetFDFromFileDescriptor(env, fileDescriptor); 83 int err = 0; 84 if (ashmem_set_prot_region(fd, prot)) { 85 err = errno; 86 } 87 return err; 88 } 89 90 static const JNINativeMethod methods[] = { 91 {"nCreate", "(Ljava/lang/String;I)Ljava/io/FileDescriptor;", (void*)SharedMemory_create}, 92 {"nGetSize", "(Ljava/io/FileDescriptor;)I", (void*)SharedMemory_getSize}, 93 {"nSetProt", "(Ljava/io/FileDescriptor;I)I", (void*)SharedMemory_setProt}, 94 }; 95 96 } // anonymous namespace 97 98 namespace android { 99 100 int register_android_os_SharedMemory(JNIEnv* env) 101 { 102 return RegisterMethodsOrDie(env, "android/os/SharedMemory", methods, NELEM(methods)); 103 } 104 105 } // namespace android 106
