Reapply "Add local impl of mapper for libhidlmemory"

This reverts commit 5410c8c04a03527289f69df063cfe9ea30349d2c.

Test: atest CtsMediaAudioTestCases
Tets: remove android.hidl.memory@1.0-impl.so from device &&
      atest CtsMediaAudioTestCases && check for call_once log
Bug: 205764958
Bug: 310700278
Bug: 310680652
Change-Id: Iebaf64882949d5923362f80e79eeed8f8fece7bb

2 files changed, 97 insertions, 2 deletions

diff --git a/libhidlmemory/AshmemMemory.h b/libhidlmemory/AshmemMemory.h
new file mode 100644
index 0000000..ffb9c00
--- /dev/null
+++ b/libhidlmemory/AshmemMemory.h
@@ -0,0 +1,61 @@
+/*
+ * Copyright (C) 2023 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.
+ */
+#pragma once
+
+#include <android/hidl/memory/1.0/IMemory.h>
+#include <hidl/Status.h>
+#include <inttypes.h>
+#include <log/log.h>
+#include <sys/mman.h>
+
+namespace android {
+namespace hardware {
+namespace impl {
+
+using ::android::sp;
+using ::android::hardware::hidl_memory;
+using ::android::hardware::Return;
+using ::android::hardware::Void;
+using ::android::hidl::memory::V1_0::IMemory;
+
+struct AshmemMemory : public IMemory {
+    AshmemMemory(const hidl_memory& memory, void* data) : mMemory(memory), mData(data) {}
+
+    ~AshmemMemory() { munmap(mData, mMemory.size()); }
+
+    // Methods from ::android::hidl::memory::V1_0::IMemory follow.
+    Return<void*> getPointer() override { return mData; }
+    Return<uint64_t> getSize() override { return mMemory.size(); }
+    // NOOPs (since non0remoted memory)
+    Return<void> update() override { return Void(); }
+    Return<void> updateRange(uint64_t /*start*/, uint64_t /*length*/) override { return Void(); }
+    Return<void> read() override { return Void(); }
+    Return<void> readRange(uint64_t /*start*/, uint64_t /*length*/) override { return Void(); }
+    Return<void> commit() override { return Void(); }
+
+  private:
+    // Holding onto hidl_memory reference because it contains
+    // handle and size, and handle will also be required for
+    // the remoted case.
+    hidl_memory mMemory;
+
+    // Mapped memory in process.
+    void* mData;
+};
+
+}  // namespace impl
+}  // namespace hardware
+}  // namespace android
diff --git a/libhidlmemory/mapping.cpp b/libhidlmemory/mapping.cpp
index 8f0bcf4..3fcc354 100644
--- a/libhidlmemory/mapping.cpp
+++ b/libhidlmemory/mapping.cpp
@@ -19,6 +19,7 @@
 #include <mutex>
 #include <string>
 
+#include <AshmemMemory.h>
 #include <hidlmemory/mapping.h>
 
 #include <android-base/logging.h>
@@ -35,6 +36,33 @@ namespace hardware {
 
 static std::map<std::string, sp<IMapper>> gMappersByName;
 static std::mutex gMutex;
+static std::once_flag gOnceFlagLog;
+
+static sp<IMemory> createAshmemMemory(const hidl_memory& mem) {
+    if (mem.handle()->numFds == 0) {
+        return nullptr;
+    }
+
+    // If ashmem service runs in 32-bit (size_t is uint32_t) and a 64-bit
+    // client process requests a memory > 2^32 bytes, the size would be
+    // converted to a 32-bit number in mmap. mmap could succeed but the
+    // mapped memory's actual size would be smaller than the reported size.
+    if (mem.size() > SIZE_MAX) {
+        ALOGE("Cannot map %" PRIu64 " bytes of memory because it is too large.", mem.size());
+        android_errorWriteLog(0x534e4554, "79376389");
+        return nullptr;
+    }
+
+    int fd = mem.handle()->data[0];
+    void* data = mmap(0, mem.size(), PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+    if (data == MAP_FAILED) {
+        // mmap never maps at address zero without MAP_FIXED, so we can avoid
+        // exposing clients to MAP_FAILED.
+        return nullptr;
+    }
+
+    return new impl::AshmemMemory(mem, data);
+}
 
 static inline sp<IMapper> getMapperService(const std::string& name) {
     std::unique_lock<std::mutex> _lock(gMutex);
@@ -55,8 +83,14 @@ sp<IMemory> mapMemory(const hidl_memory& memory) {
     sp<IMapper> mapper = getMapperService(memory.name());
 
     if (mapper == nullptr) {
-        LOG(ERROR) << "Could not fetch mapper for " << memory.name() << " shared memory";
-        return nullptr;
+        if (memory.name() == "ashmem") {
+            std::call_once(gOnceFlagLog,
+                           [&]() { LOG(INFO) << "Using libhidlmemory mapper for ashmem."; });
+            return createAshmemMemory(memory);
+        } else {
+            LOG(ERROR) << "Could not fetch mapper for " << memory.name() << " shared memory";
+            return nullptr;
+        }
     }
 
     if (mapper->isRemote()) {