libvulkan: Use a stub HAL when no real Vulkan HAL is present

This stub HAL enumerates zero VkPhysicalDevices. This allows a
VkInstane to be created and queried for physical devices successfully
even on devices without a Vulkan driver. Handling this with a stub HAL
avoids the need for NULL HAL and NULL driver function pointer checks
in many places throughout the loader, which would be more error-prone.

Fixes bug: 28100673
Change-Id: I76bea975929a85eda354730d6c815567b412b160

4 files changed, 178 insertions, 9 deletions

diff --git a/vulkan/libvulkan/Android.mk b/vulkan/libvulkan/Android.mk
index 0979471161..7830c26359 100644
--- a/vulkan/libvulkan/Android.mk
+++ b/vulkan/libvulkan/Android.mk
@@ -45,6 +45,7 @@ LOCAL_SRC_FILES := \
 	driver.cpp \
 	driver_gen.cpp \
 	layers_extensions.cpp \
+	stubhal.cpp \
 	swapchain.cpp \
 	vulkan_loader_data.cpp
 LOCAL_ADDITIONAL_DEPENDENCIES := $(LOCAL_PATH)/Android.mk
diff --git a/vulkan/libvulkan/driver.cpp b/vulkan/libvulkan/driver.cpp
index 9dbdcc21a6..72b09813ab 100644
--- a/vulkan/libvulkan/driver.cpp
+++ b/vulkan/libvulkan/driver.cpp
@@ -23,6 +23,7 @@
 #include <sys/prctl.h>
 
 #include "driver.h"
+#include "stubhal.h"
 
 // #define ENABLE_ALLOC_CALLSTACKS 1
 #if ENABLE_ALLOC_CALLSTACKS
@@ -47,7 +48,7 @@ namespace {
 
 class CreateInfoWrapper {
    public:
-    CreateInfoWrapper(hwvulkan_device_t* hw_dev,
+    CreateInfoWrapper(const hwvulkan_device_t* hw_dev,
                       const VkInstanceCreateInfo& create_info,
                       const VkAllocationCallbacks& allocator);
     CreateInfoWrapper(VkPhysicalDevice physical_dev,
@@ -87,7 +88,7 @@ class CreateInfoWrapper {
     const VkAllocationCallbacks& allocator_;
 
     union {
-        hwvulkan_device_t* hw_dev_;
+        const hwvulkan_device_t* hw_dev_;
         VkPhysicalDevice physical_dev_;
     };
 
@@ -102,7 +103,7 @@ class CreateInfoWrapper {
     std::bitset<ProcHook::EXTENSION_COUNT> hal_extensions_;
 };
 
-CreateInfoWrapper::CreateInfoWrapper(hwvulkan_device_t* hw_dev,
+CreateInfoWrapper::CreateInfoWrapper(const hwvulkan_device_t* hw_dev,
                                      const VkInstanceCreateInfo& create_info,
                                      const VkAllocationCallbacks& allocator)
     : is_instance_(true),
@@ -340,7 +341,7 @@ void CreateInfoWrapper::FilterExtension(const char* name) {
     }
 }
 
-hwvulkan_device_t* g_hwdevice = nullptr;
+const hwvulkan_device_t* g_hwdevice = nullptr;
 
 VKAPI_ATTR void* DefaultAllocate(void*,
                                  size_t size,
@@ -428,15 +429,17 @@ bool Debuggable() {
 }
 
 bool OpenHAL() {
-    if (g_hwdevice)
-        return true;
+    ALOG_ASSERT(!g_hwdevice, "OpenHAL called more than once");
+
+    // Use a stub device unless we successfully open a real HAL device.
+    g_hwdevice = &stubhal::kDevice;
 
     const hwvulkan_module_t* module;
     int result =
         hw_get_module("vulkan", reinterpret_cast<const hw_module_t**>(&module));
     if (result != 0) {
-        ALOGE("failed to load vulkan hal: %s (%d)", strerror(-result), result);
-        return false;
+        ALOGV("no Vulkan HAL present, using stub HAL");
+        return true;
     }
 
     hwvulkan_device_t* device;
@@ -444,7 +447,8 @@ bool OpenHAL() {
         module->common.methods->open(&module->common, HWVULKAN_DEVICE_0,
                                      reinterpret_cast<hw_device_t**>(&device));
     if (result != 0) {
-        ALOGE("failed to open vulkan driver: %s (%d)", strerror(-result),
+        // Any device with a Vulkan HAL should be able to open the device.
+        ALOGE("failed to open Vulkan HAL device: %s (%d)", strerror(-result),
               result);
         return false;
     }
diff --git a/vulkan/libvulkan/stubhal.cpp b/vulkan/libvulkan/stubhal.cpp
new file mode 100644
index 0000000000..89fcebbd27
--- /dev/null
+++ b/vulkan/libvulkan/stubhal.cpp
@@ -0,0 +1,134 @@
+/*
+ * Copyright 2016 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.
+ */
+
+/* NOTE:
+ * This stub HAL is only used internally by the loader when a real HAL
+ * implementation is not present, in order to avoid needing "null HAL" checks
+ * throughout the loader. It does not enumerate any physical devices, and is
+ * only as conformant to the Vulkan and Android HAL interfaces as the loader
+ * needs it to be. Do not use it as an example of a correct implementation; the
+ * code in ../null_driver is better for that.
+ */
+
+#undef LOG_TAG
+#define LOG_TAG "vkstub"
+
+#include <array>
+#include <bitset>
+#include <mutex>
+#include <hardware/hwvulkan.h>
+#include <log/log.h>
+#include "stubhal.h"
+
+namespace vulkan {
+namespace stubhal {
+
+namespace {
+
+const size_t kMaxInstances = 32;
+static std::mutex g_instance_mutex;
+static std::bitset<kMaxInstances> g_instance_used(false);
+static std::array<hwvulkan_dispatch_t, kMaxInstances> g_instances;
+
+[[noreturn]] void NoOp() {
+    LOG_ALWAYS_FATAL("invalid stub function called");
+}
+
+VKAPI_ATTR VkResult
+EnumerateInstanceExtensionProperties(const char* /*layer_name*/,
+                                     uint32_t* count,
+                                     VkExtensionProperties* /*properties*/) {
+    *count = 0;
+    return VK_SUCCESS;
+}
+
+VKAPI_ATTR VkResult
+EnumerateInstanceLayerProperties(uint32_t* count,
+                                 VkLayerProperties* /*properties*/) {
+    *count = 0;
+    return VK_SUCCESS;
+}
+
+VKAPI_ATTR VkResult CreateInstance(const VkInstanceCreateInfo* /*create_info*/,
+                                   const VkAllocationCallbacks* /*allocator*/,
+                                   VkInstance* instance) {
+    std::lock_guard<std::mutex> lock(g_instance_mutex);
+    for (size_t i = 0; i < kMaxInstances; i++) {
+        if (!g_instance_used[i]) {
+            g_instance_used[i] = true;
+            g_instances[i].magic = HWVULKAN_DISPATCH_MAGIC;
+            *instance = reinterpret_cast<VkInstance>(&g_instances[i]);
+            return VK_SUCCESS;
+        }
+    }
+    ALOGE("no more instances available (max=%zu)", kMaxInstances);
+    return VK_ERROR_INITIALIZATION_FAILED;
+}
+
+VKAPI_ATTR void DestroyInstance(VkInstance instance,
+                                const VkAllocationCallbacks* /*allocator*/) {
+    std::lock_guard<std::mutex> lock(g_instance_mutex);
+    ssize_t idx =
+        reinterpret_cast<hwvulkan_dispatch_t*>(instance) - &g_instances[0];
+    ALOG_ASSERT(idx >= 0 && idx < g_instance_used.size(),
+                "DestroyInstance: invalid instance handle");
+    g_instance_used[static_cast<size_t>(idx)] = false;
+}
+
+VKAPI_ATTR VkResult EnumeratePhysicalDevices(VkInstance /*instance*/,
+                                             uint32_t* count,
+                                             VkPhysicalDevice* /*gpus*/) {
+    *count = 0;
+    return VK_SUCCESS;
+}
+
+VKAPI_ATTR PFN_vkVoidFunction GetInstanceProcAddr(VkInstance /*instance*/,
+                                                  const char* name) {
+    if (strcmp(name, "vkCreateInstance") == 0)
+        return reinterpret_cast<PFN_vkVoidFunction>(CreateInstance);
+    if (strcmp(name, "vkDestroyInstance") == 0)
+        return reinterpret_cast<PFN_vkVoidFunction>(DestroyInstance);
+    if (strcmp(name, "vkEnumerateInstanceExtensionProperties") == 0)
+        return reinterpret_cast<PFN_vkVoidFunction>(
+            EnumerateInstanceExtensionProperties);
+    if (strcmp(name, "vkEnumeratePhysicalDevices") == 0)
+        return reinterpret_cast<PFN_vkVoidFunction>(EnumeratePhysicalDevices);
+    if (strcmp(name, "vkGetInstanceProcAddr") == 0)
+        return reinterpret_cast<PFN_vkVoidFunction>(GetInstanceProcAddr);
+
+    // None of the other Vulkan functions should ever be called, as they all
+    // take a VkPhysicalDevice or other object obtained from a physical device.
+    return reinterpret_cast<PFN_vkVoidFunction>(NoOp);
+}
+
+}  // anonymous namespace
+
+const hwvulkan_device_t kDevice = {
+    .common =
+        {
+            .tag = HARDWARE_DEVICE_TAG,
+            .version = HWVULKAN_DEVICE_API_VERSION_0_1,
+            .module = nullptr,
+            .close = nullptr,
+        },
+    .EnumerateInstanceExtensionProperties =
+        EnumerateInstanceExtensionProperties,
+    .CreateInstance = CreateInstance,
+    .GetInstanceProcAddr = GetInstanceProcAddr,
+};
+
+}  // namespace stubhal
+}  // namespace vulkan
diff --git a/vulkan/libvulkan/stubhal.h b/vulkan/libvulkan/stubhal.h
new file mode 100644
index 0000000000..9ba7d04067
--- /dev/null
+++ b/vulkan/libvulkan/stubhal.h
@@ -0,0 +1,30 @@
+/*
+ * Copyright 2016 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.
+ */
+
+#ifndef LIBVULKAN_STUBHAL_H
+#define LIBVULKAN_STUBHAL_H 1
+
+struct hwvulkan_device_t;
+
+namespace vulkan {
+namespace stubhal {
+
+extern const hwvulkan_device_t kDevice;
+
+}  // namespace stubhal
+}  // namespace vulkan
+
+#endif  // LIBVULKAN_STUBHAL_H