vulkan: write the driver pipeline cache atomically; reject truncated ones

The emulator stopped while saving vulkan_pipelines.bin left it empty, and
every later boot terminated: the header read throws ios_base::failure,
and macOS's libc++ throws one the handler's type doesn't match. Write the
cache to a temporary file and rename it over the old one, and treat a
file shorter than its header as invalid without reading it.

Assisted-by: Claude (Anthropic)

1 files changed, 22 insertions, 1 deletions

diff --git a/src/video_core/renderer_vulkan/vk_pipeline_cache.cpp b/src/video_core/renderer_vulkan/vk_pipeline_cache.cpp
index ac878ddfef..2c64f3375b 100644
--- a/src/video_core/renderer_vulkan/vk_pipeline_cache.cpp
+++ b/src/video_core/renderer_vulkan/vk_pipeline_cache.cpp
@@ -1138,7 +1138,11 @@ std::unique_ptr<ComputePipeline> PipelineCache::CreateComputePipeline(
 void PipelineCache::SerializeVulkanPipelineCache(const std::filesystem::path& filename,
                                                  const vk::PipelineCache& pipeline_cache,
                                                  u32 cache_version) try {
-    std::ofstream file(filename, std::ios::binary);
+    // Written beside the cache and renamed over it: the emulator stopped mid-write left the cache
+    // empty, and every later boot failed to read it.
+    auto temporary = filename;
+    temporary += ".tmp";
+    std::ofstream file(temporary, std::ios::binary);
     file.exceptions(std::ifstream::failbit);
     if (!file.is_open()) {
         LOG_ERROR(Common_Filesystem, "Failed to open Vulkan driver pipeline cache file {}",
@@ -1156,6 +1160,15 @@ void PipelineCache::SerializeVulkanPipelineCache(const std::filesystem::path& fi
         pipeline_cache.Read(&cache_size, cache_data.data());
     }
     file.write(cache_data.data(), cache_size);
+    file.close();
+    std::error_code error;
+    std::filesystem::rename(temporary, filename, error);
+    if (error) {
+        LOG_ERROR(Common_Filesystem, "Failed to replace Vulkan driver pipeline cache file {}: {}",
+                  Common::FS::PathToUTF8String(filename), error.message());
+        std::filesystem::remove(temporary, error);
+        return;
+    }
 
     LOG_INFO(Render_Vulkan, "Vulkan driver pipelines cached at: {}",
              Common::FS::PathToUTF8String(filename));
@@ -1190,6 +1203,14 @@ vk::PipelineCache PipelineCache::LoadVulkanPipelineCache(const std::filesystem::
 
         std::array<char, 8> magic_number;
         u32 cache_version;
+        // A file cut short (the emulator stopped while writing it) would throw from the reads
+        // below, and macOS's libc++ throws an ios_base::failure the handler doesn't match.
+        if (static_cast<size_t>(end) < magic_number.size() + sizeof(cache_version)) {
+            file.close();
+            LOG_ERROR(Common_Filesystem, "Truncated Vulkan driver pipeline cache file, deleting it");
+            Common::FS::RemoveFile(filename);
+            return create_pipeline_cache(0, nullptr);
+        }
         file.read(magic_number.data(), magic_number.size())
             .read(reinterpret_cast<char*>(&cache_version), sizeof(cache_version));
         if (magic_number != VULKAN_CACHE_MAGIC_NUMBER || cache_version != expected_cache_version) {