Gles && vulkan interoperation –vulkan准备-五八三

背景

unity提供了NativeRenderingPlugin 的方式扩展 render api —vulkan，本质是hook vulkan api的方式，供用户扩展他。

为了在unity侧开启 VK_KHR_external_memory_fd的扩展，需要熟悉unity的 NativeRenderingPlugin，以及vulkan specs。

NativeRenderingPlugin

hook api 的原理

Native rendering plugin侧定义一些需要hook的command 函数指针，存hook前指针，比如：

static PFN_##func func
static PFN_vkCreateInstance vkCreateInstance
static PFN_vkCreateDevice vkCreateDevice

Native rendering plugin侧在插件入口函数处通过vkGetInstanceProcAddr，给static PFN_* 赋值比如：

vkCreateInstance = 
(PFN_vkCreateInstance)vkGetInstanceProcAddr(VK_NULL_HANDLE, "vkCreateInstance");

vkCreateDevice= 
(PFN_vkCreateDevice)vkGetInstanceProcAddr(instance, "vkCreateDevice");

Native rendering plugin侧通过 IUnityGraphicVulkan.h中的InterceptVulkanAPI，hook想要的api 比如：

vkCreateDevice= m_UnityVulkan->InterceptVulkanAPI("vkCreateDevice", 
    (PFN_vkCreateDevice)Hook_vkCreateDevice);
vkCmdBeginRenderPass = m_UnityVulkan->InterceptVulkanAPI("vkCmdBeginRenderPass", 
    (PFN_vkVoidFunction)Hook_vkCmdBeginRenderPass);

基于以上3点就可以实现hook api

Vulkan specs

vkGetInstanceProcAddr

例如

Return a function pointer for a command

// Provided by VK_VERSION_1_0
PFN_vkVoidFunction vkGetInstanceProcAddr(
    VkInstance                                  instance,
    const char*                                 pName);

参数：
    instance is the instance that the function pointer will be compatible with, or NULL for commands not dependent on any instance.
    pName is the name of the command to obtain.

获取Vulkan Command(其实就是vulkan的api) 的函数指针。

Command 分两种类型，global command，dispatchable command.

Global command:

   不需要绑定vulkan instance 的command，

比如:

vkCreateInstance，vkEnumerateInstanceVersion,

vkEnumerateInstanceExtensionProperties,等

Dispatchable command:

   所有非global command

其中instance既可以为vkCreateInstance()返回的实例，可以为null，为null的时候，主要作用是获得vkCreateInstance的函数指针，方便用户hook

注意点

nativeRenderingPlugin 必须命名前缀为：GfxPlugin
编译出来的plugin 在unity里需要勾选preload

主要参看代码：

#define UNITY_USED_VULKAN_API_FUNCTIONS(apply) \
    apply(vkCreateInstance); \
    apply(vkCmdBeginRenderPass); \
    apply(vkCreateBuffer); \
    apply(vkGetPhysicalDeviceMemoryProperties); \
    apply(vkGetBufferMemoryRequirements); \
    apply(vkMapMemory); \
    apply(vkBindBufferMemory); \
    apply(vkAllocateMemory); \
    apply(vkDestroyBuffer); \
    apply(vkFreeMemory); \
    apply(vkUnmapMemory); \
    apply(vkQueueWaitIdle); \
    apply(vkDeviceWaitIdle); \
    apply(vkCmdCopyBufferToImage); \
    apply(vkFlushMappedMemoryRanges); \
    apply(vkCreatePipelineLayout); \
    apply(vkCreateShaderModule); \
    apply(vkDestroyShaderModule); \
    apply(vkCreateGraphicsPipelines); \
    apply(vkCmdBindPipeline); \
    apply(vkCmdDraw); \
    apply(vkCmdPushConstants); \
    apply(vkCmdBindVertexBuffers); \
    apply(vkDestroyPipeline); \
    apply(vkDestroyPipelineLayout);
    
#define VULKAN_DEFINE_API_FUNCPTR(func) static PFN_##func func
VULKAN_DEFINE_API_FUNCPTR(vkGetInstanceProcAddr);
UNITY_USED_VULKAN_API_FUNCTIONS(VULKAN_DEFINE_API_FUNCPTR);
#undef VULKAN_DEFINE_API_FUNCPTR

static void LoadVulkanAPI(PFN_vkGetInstanceProcAddr getInstanceProcAddr, VkInstance instance)
{
    if (!vkGetInstanceProcAddr && getInstanceProcAddr)
        vkGetInstanceProcAddr = getInstanceProcAddr;

	if (!vkCreateInstance)
		vkCreateInstance = (PFN_vkCreateInstance)vkGetInstanceProcAddr(VK_NULL_HANDLE, "vkCreateInstance");

#define LOAD_VULKAN_FUNC(fn) if (!fn) fn = (PFN_##fn)vkGetInstanceProcAddr(instance, #fn)
    UNITY_USED_VULKAN_API_FUNCTIONS(LOAD_VULKAN_FUNC);
#undef LOAD_VULKAN_FUNC
}
static VKAPI_ATTR void VKAPI_CALL Hook_vkCmdBeginRenderPass(VkCommandBuffer commandBuffer, const VkRenderPassBeginInfo* pRenderPassBegin, VkSubpassContents contents)
{
    // Change this to 'true' to override the clear color with green
	const bool allowOverrideClearColor = false;
    if (pRenderPassBegin->clearValueCount <= 16 && pRenderPassBegin->clearValueCount > 0 && allowOverrideClearColor)
    {
        VkClearValue clearValues[16] = {};
        memcpy(clearValues, pRenderPassBegin->pClearValues, pRenderPassBegin->clearValueCount * sizeof(VkClearValue));

        VkRenderPassBeginInfo patchedBeginInfo = *pRenderPassBegin;
        patchedBeginInfo.pClearValues = clearValues;
        for (unsigned int i = 0; i < pRenderPassBegin->clearValueCount - 1; ++i)
        {
            clearValues[i].color.float32[0] = 0.0;
            clearValues[i].color.float32[1] = 1.0;
            clearValues[i].color.float32[2] = 0.0;
            clearValues[i].color.float32[3] = 1.0;
        }
        vkCmdBeginRenderPass(commandBuffer, &patchedBeginInfo, contents);
    }
    else
    {
        vkCmdBeginRenderPass(commandBuffer, pRenderPassBegin, contents);
    }
}

static VKAPI_ATTR VkResult VKAPI_CALL Hook_vkCreateInstance(const VkInstanceCreateInfo* pCreateInfo, const VkAllocationCallbacks* pAllocator, VkInstance* pInstance)
{
    vkCreateInstance = (PFN_vkCreateInstance)vkGetInstanceProcAddr(VK_NULL_HANDLE, "vkCreateInstance");
    VkResult result = vkCreateInstance(pCreateInfo, pAllocator, pInstance);
    if (result == VK_SUCCESS)
        LoadVulkanAPI(vkGetInstanceProcAddr, *pInstance);
 
    return result;
}

static int FindMemoryTypeIndex(VkPhysicalDeviceMemoryProperties const & physicalDeviceMemoryProperties, VkMemoryRequirements const & memoryRequirements, VkMemoryPropertyFlags memoryPropertyFlags)
{
    uint32_t memoryTypeBits = memoryRequirements.memoryTypeBits;

    // Search memtypes to find first index with those properties
    for (uint32_t memoryTypeIndex = 0; memoryTypeIndex < VK_MAX_MEMORY_TYPES; ++memoryTypeIndex)
    {
        if ((memoryTypeBits & 1) == 1)
        {
            // Type is available, does it match user properties?
            if ((physicalDeviceMemoryProperties.memoryTypes[memoryTypeIndex].propertyFlags & memoryPropertyFlags) == memoryPropertyFlags)
                return memoryTypeIndex;
        }
        memoryTypeBits >>= 1;
    }

    return -1;
}

static VKAPI_ATTR PFN_vkVoidFunction VKAPI_CALL Hook_vkGetInstanceProcAddr(VkInstance device, const char* funcName)
{
    if (!funcName)
        return NULL;

#define INTERCEPT(fn) if (strcmp(funcName, #fn) == 0) return (PFN_vkVoidFunction)&Hook_##fn
    INTERCEPT(vkCreateInstance);
#undef INTERCEPT

    return NULL;
}

static PFN_vkGetInstanceProcAddr UNITY_INTERFACE_API InterceptVulkanInitialization(PFN_vkGetInstanceProcAddr getInstanceProcAddr, void*)
{
    vkGetInstanceProcAddr = getInstanceProcAddr;
    return Hook_vkGetInstanceProcAddr;
}