[Memory] Android memory mapping

src/xenia/base/memory_posix.cc

@@ -8,12 +8,23 @@
  */
 
 #include "xenia/base/memory.h"
-#include "xenia/base/string.h"
 
 #include <fcntl.h>
 #include <sys/mman.h>
 #include <unistd.h>
 
+#include "xenia/base/math.h"
+#include "xenia/base/platform.h"
+#include "xenia/base/string.h"
+
+#if XE_PLATFORM_ANDROID
+#include <linux/ashmem.h>
+#include <string.h>
+#include <sys/ioctl.h>
+
+#include "xenia/base/platform_android.h"
+#endif
+
 namespace xe {
 namespace memory {
 
@@ -70,6 +81,31 @@ bool QueryProtect(void* base_address, size_t& length, PageAccess& access_out) {
 FileMappingHandle CreateFileMappingHandle(const std::filesystem::path& path,
                                           size_t length, PageAccess access,
                                           bool commit) {
+#if XE_PLATFORM_ANDROID
+  if (xe::platform::android::api_level() >= 26) {
+    // TODO(Triang3l): Check if memfd can be used instead on API 30+.
+    int sharedmem_fd =
+        xe::platform::android::api_functions().api_26.ASharedMemory_create(
+            path.c_str(), length);
+    return sharedmem_fd >= 0 ? sharedmem_fd : kFileMappingHandleInvalid;
+  }
+
+  // Use /dev/ashmem on API versions below 26, which added ASharedMemory.
+  // /dev/ashmem was disabled on API 29 for apps targeting it.
+  // https://chromium.googlesource.com/chromium/src/+/master/third_party/ashmem/ashmem-dev.c
+  int ashmem_fd = open("/" ASHMEM_NAME_DEF, O_RDWR);
+  if (ashmem_fd < 0) {
+    return kFileMappingHandleInvalid;
+  }
+  char ashmem_name[ASHMEM_NAME_LEN];
+  strlcpy(ashmem_name, path.c_str(), xe::countof(ashmem_name));
+  if (ioctl(ashmem_fd, ASHMEM_SET_NAME, ashmem_name) < 0 ||
+      ioctl(ashmem_fd, ASHMEM_SET_SIZE, length) < 0) {
+    close(ashmem_fd);
+    return kFileMappingHandleInvalid;
+  }
+  return ashmem_fd;
+#else
   int oflag;
   switch (access) {
     case PageAccess::kNoAccess:
@@ -94,13 +130,16 @@ FileMappingHandle CreateFileMappingHandle(const std::filesystem::path& path,
   }
   ftruncate64(ret, length);
   return ret;
+#endif
 }
 
 void CloseFileMappingHandle(FileMappingHandle handle,
                             const std::filesystem::path& path) {
   close(handle);
+#if !XE_PLATFORM_ANDROID
   auto full_path = "/" / path;
   shm_unlink(full_path.c_str());
+#endif
 }
 
 void* MapFileView(FileMappingHandle handle, void* base_address, size_t length,

src/xenia/base/platform_android.cc

@@ -0,0 +1,60 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2020 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#include "xenia/base/platform_android.h"
+
+#include <android/configuration.h>
+#include <dlfcn.h>
+
+#include "xenia/base/assert.h"
+
+namespace xe {
+namespace platform {
+namespace android {
+
+static bool initialized = false;
+
+static int32_t api_level_ = __ANDROID_API__;
+
+static ApiFunctions api_functions_;
+
+void Initialize(const ANativeActivity* activity) {
+  if (initialized) {
+    return;
+  }
+
+  AConfiguration* configuration = AConfiguration_new();
+  AConfiguration_fromAssetManager(configuration, activity->assetManager);
+  api_level_ = AConfiguration_getSdkVersion(configuration);
+  AConfiguration_delete(configuration);
+
+  if (api_level_ >= 26) {
+    // Leaked intentionally, already loaded into the address space.
+    // https://chromium.googlesource.com/chromium/src/+/master/third_party/ashmem/ashmem-dev.c#201
+    void* libandroid = dlopen("libandroid.so", RTLD_NOW);
+    assert_not_null(libandroid);
+#define XE_PLATFORM_ANDROID_LOAD_API_FUNCTION(name, api)         \
+  api_functions_.api_##api.name =                                \
+      reinterpret_cast<decltype(api_functions_.api_##api.name)>( \
+          dlsym(libandroid, #name));                             \
+  assert_not_null(api_functions_.api_##api.name);
+    XE_PLATFORM_ANDROID_LOAD_API_FUNCTION(ASharedMemory_create, 26);
+#undef XE_PLATFORM_ANDROID_LOAD_API_FUNCTION
+  }
+
+  initialized = true;
+}
+
+int32_t api_level() { return api_level_; }
+
+const ApiFunctions& api_functions() { return api_functions_; }
+
+}  // namespace android
+}  // namespace platform
+}  // namespace xe

src/xenia/base/platform_android.h

@@ -0,0 +1,44 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2020 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#ifndef XENIA_BASE_PLATFORM_ANDROID_H_
+#define XENIA_BASE_PLATFORM_ANDROID_H_
+
+// NOTE: if you're including this file it means you are explicitly depending
+// on Android-specific headers. This is bad for portability and should be
+// avoided!
+
+#include <android/native_activity.h>
+#include <cstddef>
+#include <cstdint>
+
+namespace xe {
+namespace platform {
+namespace android {
+
+// Must be called in onCreate of the first activity.
+void Initialize(const ANativeActivity* activity);
+
+// Returns the device API level - if not initialized, will return the minimum
+// level supported by Xenia.
+int32_t api_level();
+
+// Android API functions added after the minimum supported API version.
+struct ApiFunctions {
+  struct {
+    int (*ASharedMemory_create)(const char* name, size_t size);
+  } api_26;
+};
+const ApiFunctions& api_functions();
+
+}  // namespace android
+}  // namespace platform
+}  // namespace xe
+
+#endif  // XENIA_BASE_PLATFORM_ANDROID_H_