Vulkan: Add vk_icdInitializeConnectToServiceCallback()

CMakeLists.txt

@@ -257,10 +257,18 @@ macro(set_shared_library_export_map TARGET DIR)
             set_property(TARGET ${TARGET} APPEND_STRING PROPERTY LINK_FLAGS " -Wl,-undefined,error")
         endif()
     elseif(LINUX OR FUCHSIA)
+        # NOTE: The Fuchsia linker script is needed to export the vk_icdInitializeConnectToServiceCallback
+        # entry point (a private implementation detail betwen the Fuchsia Vulkan loader and the ICD).
+        if ((FUCHSIA) AND ("${TARGET}" STREQUAL "vk_swiftshader"))
+          set(LINKER_VERSION_SCRIPT "fuchsia_vk_swiftshader.lds")
+        else()
+          set(LINKER_VERSION_SCRIPT "${TARGET}.lds")
+        endif()
+
         # The version script only exports the API functions and
         # hides all the others.
-        set_property(TARGET ${TARGET} APPEND_STRING PROPERTY LINK_FLAGS " -Wl,--version-script=${DIR}/${TARGET}.lds")
-        set_property(TARGET ${TARGET} APPEND_STRING PROPERTY LINK_DEPENDS "${DIR}/${TARGET}.lds;")
+        set_property(TARGET ${TARGET} APPEND_STRING PROPERTY LINK_FLAGS " -Wl,--version-script=${DIR}/${LINKER_VERSION_SCRIPT}")
+        set_property(TARGET ${TARGET} APPEND_STRING PROPERTY LINK_DEPENDS "${DIR}/${LINKER_VERSION_SCRIPT};")
 
         # -Bsymbolic binds symbol references to their global definitions within
         # a shared object, thereby preventing symbol preemption.

src/Vulkan/VkGetProcAddress.cpp

@@ -517,4 +517,8 @@ extern "C" hwvulkan_module_t HAL_MODULE_INFO_SYM = {
 	}
 };
 
+#endif  // __ANDROID__
+
+#if VK_USE_PLATFORM_FUCHSIA
+PFN_vkConnectToService vk::icdFuchsiaServiceConnectCallback = nullptr;
 #endif

src/Vulkan/VkGetProcAddress.h

@@ -27,4 +27,16 @@ PFN_vkVoidFunction GetDeviceProcAddr(Device* device, const char* pName);
 
 }  // namespace vk
 
-#endif // VK_UTILS_HPP_
\ No newline at end of file
+#if VK_USE_PLATFORM_FUCHSIA
+// See vk_icdInitializeServiceConnectCallback() in libVulkan.cpp for details
+// about this global pointer. Since this is a private implementation detail
+// between the Vulkan loader and the ICDs, this type will never be part of
+// the <vulkan/vulkan_fuchsia.h> headers, so define the type here.
+typedef VkResult(VKAPI_PTR* PFN_vkConnectToService)(const char* pName, uint32_t handle);
+
+namespace vk {
+extern PFN_vkConnectToService icdFuchsiaServiceConnectCallback;
+}
+#endif  // VK_USE_PLATFORM_FUCHSIA
+
+#endif // VK_UTILS_HPP_

src/Vulkan/fuchsia_vk_swiftshader.lds

+# For Fuchsia, we must not export anything other than loader-related API
+# There is also the vk_icdInitializeConnectToServiceCallback entry point
+# that is specific to the Fuchsia Vulkan loader implementation.
+{
+global:
+	vkGetInstanceProcAddr;
+
+	# Loader-ICD interface functions
+	vk_icdGetInstanceProcAddr;
+	vk_icdNegotiateLoaderICDInterfaceVersion;
+	vk_icdInitializeConnectToServiceCallback;
+
+	# Type-strings and type-infos required by sanitizers
+	_ZTS*;
+	_ZTI*;
+
+local:
+	*;
+};
+

src/Vulkan/libVulkan.cpp

@@ -275,6 +275,26 @@ VK_EXPORT VKAPI_ATTR VkResult VKAPI_CALL vk_icdNegotiateLoaderICDInterfaceVersio
 	return VK_SUCCESS;
 }
 
+#if VK_USE_PLATFORM_FUCHSIA
+
+// This symbol must be exported by a Fuchsia Vulkan ICD. The Vulkan loader will
+// call it, passing the address of a global function pointer that can later be
+// used at runtime to connect to Fuchsia FIDL services, as required by certain
+// extensions. See https://fxbug.dev/13095 for more details.
+//
+// NOTE: This entry point has not been upstreamed to Khronos yet, which reserves
+//       all symbols starting with vk_icd. See https://fxbug.dev/13074 which
+//       tracks upstreaming progress.
+VK_EXPORT VKAPI_ATTR VkResult VKAPI_CALL vk_icdInitializeConnectToServiceCallback(
+    PFN_vkConnectToService callback)
+{
+	TRACE("(callback = %p)", callback);
+	vk::icdFuchsiaServiceConnectCallback = callback;
+	return VK_SUCCESS;
+}
+
+#endif  // VK_USE_PLATFORM_FUCHSIA
+
 static const VkExtensionProperties instanceExtensionProperties[] = {
 	{ VK_KHR_DEVICE_GROUP_CREATION_EXTENSION_NAME, VK_KHR_DEVICE_GROUP_CREATION_SPEC_VERSION },
 	{ VK_KHR_EXTERNAL_FENCE_CAPABILITIES_EXTENSION_NAME, VK_KHR_EXTERNAL_FENCE_CAPABILITIES_SPEC_VERSION },