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
24 #include <nativehelper/jni_macros.h>
25 #include <nativehelper/JNIHelp.h>
26 #include <nativehelper/ScopedLocalRef.h>
27
28 #include <algorithm>
29 #include <errno.h>
30 #include <limits>
31 #include <unistd.h>
32
33 namespace {
34
35 jclass errnoExceptionClass;
36 jmethodID errnoExceptionCtor; // MethodID for ErrnoException.<init>(String,I)
37
throwErrnoException(JNIEnv * env,const char * functionName,int error)38 void throwErrnoException(JNIEnv* env, const char* functionName, int error) {
39 ScopedLocalRef<jstring> detailMessage(env, env->NewStringUTF(functionName));
40 if (detailMessage.get() == NULL) {
41 // Not really much we can do here. We're probably dead in the water,
42 // but let's try to stumble on...
43 env->ExceptionClear();
44 }
45
46 jobject exception = env->NewObject(errnoExceptionClass,
47 errnoExceptionCtor,
48 detailMessage.get(),
49 error);
50 env->Throw(reinterpret_cast<jthrowable>(exception));
51 }
52
SharedMemory_nCreate(JNIEnv * env,jobject,jstring jname,jint size)53 jobject SharedMemory_nCreate(JNIEnv* env, jobject, jstring jname, jint size) {
54
55 // Name is optional so we can't use ScopedUtfChars for this as it throws NPE on null
56 const char* name = jname ? env->GetStringUTFChars(jname, nullptr) : nullptr;
57
58 int fd = ashmem_create_region(name, size);
59
60 // Capture the error, if there is one, before calling ReleaseStringUTFChars
61 int err = fd < 0 ? errno : 0;
62
63 if (name) {
64 env->ReleaseStringUTFChars(jname, name);
65 }
66
67 if (fd < 0) {
68 throwErrnoException(env, "SharedMemory_create", err);
69 return nullptr;
70 }
71
72 return jniCreateFileDescriptor(env, fd);
73 }
74
SharedMemory_nGetSize(JNIEnv * env,jobject,jobject fileDescriptor)75 jint SharedMemory_nGetSize(JNIEnv* env, jobject, jobject fileDescriptor) {
76 int fd = jniGetFDFromFileDescriptor(env, fileDescriptor);
77 if (!ashmem_valid(fd)) {
78 return -1;
79 }
80 size_t size = ashmem_get_size_region(fd);
81 return static_cast<jint>(std::min(size, static_cast<size_t>(std::numeric_limits<jint>::max())));
82 }
83
SharedMemory_nSetProt(JNIEnv * env,jobject,jobject fileDescriptor,jint prot)84 jint SharedMemory_nSetProt(JNIEnv* env, jobject, jobject fileDescriptor, jint prot) {
85 int fd = jniGetFDFromFileDescriptor(env, fileDescriptor);
86 int err = 0;
87 if (ashmem_set_prot_region(fd, prot)) {
88 err = errno;
89 }
90 return err;
91 }
92
93 const JNINativeMethod methods[] = {
94 NATIVE_METHOD(SharedMemory, nCreate, "(Ljava/lang/String;I)Ljava/io/FileDescriptor;"),
95 NATIVE_METHOD(SharedMemory, nGetSize, "(Ljava/io/FileDescriptor;)I"),
96 NATIVE_METHOD(SharedMemory, nSetProt, "(Ljava/io/FileDescriptor;I)I")
97 };
98
99 } // anonymous namespace
100
101 namespace android {
102
register_android_os_SharedMemory(JNIEnv * env)103 int register_android_os_SharedMemory(JNIEnv* env) {
104 errnoExceptionClass =
105 MakeGlobalRefOrDie(env, FindClassOrDie(env, "android/system/ErrnoException"));
106 errnoExceptionCtor =
107 GetMethodIDOrDie(env, errnoExceptionClass, "<init>", "(Ljava/lang/String;I)V");
108 return RegisterMethodsOrDie(env, "android/os/SharedMemory", methods, NELEM(methods));
109 }
110
111 } // namespace android
112