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
throwErrnoException(JNIEnv * env,const char * functionName,int error)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
SharedMemory_create(JNIEnv * env,jobject,jstring jname,jint size)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
SharedMemory_getSize(JNIEnv * env,jobject,jobject fileDescriptor)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
SharedMemory_setProt(JNIEnv * env,jobject,jobject fileDescriptor,jint prot)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
register_android_os_SharedMemory(JNIEnv * env)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