/*
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* Copyright (C) 2019 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include <android-base/logging.h>
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#include <android/ashmemd/IAshmemDeviceService.h>
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#include <binder/IServiceManager.h>
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#include <cutils/android_filesystem_config.h>
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using android::IBinder;
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using android::IServiceManager;
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using android::String16;
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using android::ashmemd::IAshmemDeviceService;
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using android::os::ParcelFileDescriptor;
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namespace android {
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namespace ashmemd {
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static bool checkBinderAccess() {
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// Isolated apps are potentially subject to seccomp policy that restricts use of access()
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// (b/129483782). However, apps always have access to binder, so return true.
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auto uid = getuid() % AID_USER;
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if (AID_ISOLATED_START <= uid && uid <= AID_ISOLATED_END) {
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return true;
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}
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if (access("/dev/binder", R_OK | W_OK) == 0) {
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return true;
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}
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return false;
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}
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sp<IAshmemDeviceService> getAshmemService() {
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// Calls to defaultServiceManager() crash the process if it doesn't have appropriate
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// binder permissions. Check these permissions proactively.
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if (!checkBinderAccess()) {
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return nullptr;
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}
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sp<IServiceManager> sm = android::defaultServiceManager();
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sp<IBinder> binder = sm->checkService(String16("ashmem_device_service"));
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return interface_cast<IAshmemDeviceService>(binder);
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}
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extern "C" int openAshmemdFd() {
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static sp<IAshmemDeviceService> ashmemService = getAshmemService();
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if (!ashmemService) {
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LOG(ERROR) << "Failed to get IAshmemDeviceService.";
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return -1;
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}
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ParcelFileDescriptor fd;
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auto status = ashmemService->open(&fd);
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if (!status.isOk()) {
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LOG(ERROR) << "Failed IAshmemDeviceService::open()";
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return -1;
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}
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// unique_fd is the underlying type of ParcelFileDescriptor, i.e. fd is
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// closed when it falls out of scope, so we make a dup.
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return dup(fd.get());
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}
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} // namespace ashmemd
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} // namespace android
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