kernel/vfs: extract fs type registry

10 files changed, 136 insertions, 31 deletions

diff --git a/arch/x86_64/scripts/kernel.ld b/arch/x86_64/scripts/kernel.ld
index a1d8a65..dbb0f8f 100644
--- a/arch/x86_64/scripts/kernel.ld
+++ b/arch/x86_64/scripts/kernel.ld
@@ -74,9 +74,10 @@ SECTIONS
     *(.rodata*)
 
     . = ALIGN(8);
-    PROVIDE(__start_vfs_type_descriptors = .);
-    KEEP(*(vfs_type_descriptors));
-    PROVIDE(__stop_vfs_type_descriptors = .);
+
+    PROVIDE(__start_fs_types = .);
+    KEEP(*(fs_types));
+    PROVIDE(__stop_fs_types = .);
   } :kernel_rodata
 
   .kernel_data ALIGN(4K) : AT (ADDR (.kernel_data) - TEACHOS_VMA)
diff --git a/kernel/CMakeLists.txt b/kernel/CMakeLists.txt
index cbc7fa5..3dd84ba 100644
--- a/kernel/CMakeLists.txt
+++ b/kernel/CMakeLists.txt
@@ -53,6 +53,7 @@ target_sources("kernel_lib" PRIVATE
     "src/filesystem/mount.cpp"
     "src/filesystem/open_file_descriptor.cpp"
     "src/filesystem/open_file_table.cpp"
+    "src/filesystem/type_registry.cpp"
     "src/filesystem/vfs.cpp"
 
     # DevFS Filesystem
diff --git a/kernel/include/kernel/filesystem/type.hpp b/kernel/include/kernel/filesystem/type.hpp
index 87e466b..0948e54 100644
--- a/kernel/include/kernel/filesystem/type.hpp
+++ b/kernel/include/kernel/filesystem/type.hpp
@@ -28,6 +28,15 @@ namespace kernel::filesystem
     [[nodiscard]] virtual auto make_instance() const -> kstd::shared_ptr<filesystem> = 0;
   };
 
+  template<typename Type>
+  struct type_registration
+  {
+    constexpr auto static instance = Type{};
+    [[using gnu: section("fs_types"), used, visibility("hidden")]] constexpr auto static pointer{
+      kstd::make_observer<type const>(&instance),
+    };
+  };
+
 }  // namespace kernel::filesystem
 
 #endif
diff --git a/kernel/include/kernel/filesystem/type_registry.hpp b/kernel/include/kernel/filesystem/type_registry.hpp
new file mode 100644
index 0000000..2f5e708
--- /dev/null
+++ b/kernel/include/kernel/filesystem/type_registry.hpp
@@ -0,0 +1,47 @@
+#ifndef TEACH_OS_KERNEL_TYPE_REGISRY_HPP
+#define TEACH_OS_KERNEL_TYPE_REGISRY_HPP
+
+#include <kernel/filesystem/type.hpp>
+
+#include <kstd/flat_map>
+#include <kstd/memory>
+#include <kstd/string>
+
+#include <span>
+#include <string_view>
+
+namespace kernel::filesystem
+{
+
+  struct type_registry
+  {
+    using value_type = type;
+    using pointer = kstd::observer_ptr<value_type const>;
+
+    auto static init() -> void;
+    auto static get() -> type_registry &;
+
+    constexpr type_registry() noexcept = default;
+
+    //! Add a type descriptor to this registry.
+    //!
+    //! This function will register the given descriptor with this registry, given that no descriptor for a filesystem
+    //! with the same name exists in this registry already.
+    //!
+    //! @param descriptor The filesystem type descriptor to add to the registry.
+    //! @return @p true iff. the descriptor was successfully added, @p false if not.
+    auto add(pointer descriptor) -> bool;
+
+    //! Get all currently registered type descriptors.
+    //!
+    //! @return A span containing all currently registered filesystem type descriptors.
+    [[nodiscard]] auto all() const noexcept -> std::span<pointer>;
+
+  private:
+    //! A map from filesystem names (identifiers) to filesystem type descriptors.
+    kstd::flat_map<std::string_view, pointer> m_descriptors{};
+  };
+
+}  // namespace kernel::filesystem
+
+#endif
diff --git a/kernel/include/kernel/filesystem/vfs.hpp b/kernel/include/kernel/filesystem/vfs.hpp
index c8aae5c..ddc9a9b 100644
--- a/kernel/include/kernel/filesystem/vfs.hpp
+++ b/kernel/include/kernel/filesystem/vfs.hpp
@@ -6,11 +6,8 @@
 #include <kernel/filesystem/filesystem.hpp>
 #include <kernel/filesystem/mount.hpp>
 #include <kernel/filesystem/mount_table.hpp>
-#include <kernel/filesystem/type.hpp>
 
-#include <kstd/flat_map>
 #include <kstd/memory>
-#include <kstd/string>
 
 #include <string_view>
 #include <utility>
@@ -109,8 +106,6 @@ namespace kernel::filesystem
 
     auto graft_persistent_device_fs(kstd::shared_ptr<devfs::filesystem> const & device_fs) -> void;
 
-    //! A map from filesystem names (identifiers) to filesystem type descriptors.
-    kstd::flat_map<kstd::string, kstd::observer_ptr<type const>> m_filesystems{};
     mount_table m_mount_table{};
   };
 }  // namespace kernel::filesystem
diff --git a/kernel/src/filesystem/devfs/filesystem.cpp b/kernel/src/filesystem/devfs/filesystem.cpp
index 1aaa0d1..ce887ff 100644
--- a/kernel/src/filesystem/devfs/filesystem.cpp
+++ b/kernel/src/filesystem/devfs/filesystem.cpp
@@ -32,10 +32,10 @@ namespace kernel::filesystem::devfs
     {
       return kstd::make_shared<filesystem>();
     }
-  } const constinit type_instance{};
+  };
 
-  [[gnu::section("vfs_type_descriptors"), gnu::used]]
-  auto const * const type_descriptor_pointer = static_cast<kernel::filesystem::type const *>(&type_instance);
+  [[gnu::used]]
+  constexpr auto registration = type_registration<type>{};
 
   auto filesystem::mount(kstd::shared_ptr<kernel::filesystem::inode> const &) -> operation_result
   {
diff --git a/kernel/src/filesystem/ext2/filesystem.cpp b/kernel/src/filesystem/ext2/filesystem.cpp
index 7b5d2d7..3180a19 100644
--- a/kernel/src/filesystem/ext2/filesystem.cpp
+++ b/kernel/src/filesystem/ext2/filesystem.cpp
@@ -36,10 +36,10 @@ namespace kernel::filesystem::ext2
     {
       return kstd::make_shared<filesystem>();
     }
-  } const constinit type_instance{};
+  };
 
-  [[gnu::section("vfs_type_descriptors"), gnu::used]]
-  auto const * const type_descriptor_pointer = static_cast<kernel::filesystem::type const *>(&type_instance);
+  [[gnu::used]]
+  constexpr auto registration = type_registration<type>{};
 
   auto filesystem::mount(kstd::shared_ptr<kernel::filesystem::inode> const & backing_inode) -> operation_result
   {
diff --git a/kernel/src/filesystem/type_registry.cpp b/kernel/src/filesystem/type_registry.cpp
new file mode 100644
index 0000000..033b879
--- /dev/null
+++ b/kernel/src/filesystem/type_registry.cpp
@@ -0,0 +1,67 @@
+#include <kernel/filesystem/type_registry.hpp>
+
+#include <kapi/system.hpp>
+
+#include <kstd/memory>
+#include <kstd/print>
+
+#include <algorithm>
+#include <optional>
+#include <ranges>
+#include <span>
+
+namespace kernel::filesystem
+{
+
+  extern "C"
+  {
+    extern type_registry::pointer const __start_fs_types;
+    extern type_registry::pointer const __stop_fs_types;
+  }
+
+  namespace
+  {
+    auto constinit instance = std::optional<type_registry>{};
+  }
+
+  auto type_registry::init() -> void
+  {
+    if (instance)
+    {
+      kapi::system::panic("[FILESYSTEM] tried to initialize type registry more than once!");
+    }
+
+    instance.emplace();
+
+    auto type_descriptors = std::span{&__start_fs_types, &__stop_fs_types} |  //
+                            std::views::filter([](auto p) { return p != nullptr; });
+
+    std::ranges::for_each(type_descriptors, [](auto descriptor) {
+      kstd::println("[FILESYSTEM] registering '{}'", descriptor->name());
+      instance->add(descriptor);
+    });
+  }
+
+  auto type_registry::get() -> type_registry &
+  {
+    if (!instance)
+    {
+      kapi::system::panic("[FILESYSTEM] type registry has not been initialized!");
+    }
+
+    return *instance;
+  }
+
+  auto type_registry::add(pointer descriptor) -> bool
+  {
+    auto result = m_descriptors.emplace(descriptor->name(), descriptor);
+    return result.second;
+  }
+
+  [[nodiscard]] auto type_registry::all() const noexcept -> std::span<pointer>
+  {
+    // TODO: implement value accessor for flat_map
+    return {};
+  }
+
+}  // namespace kernel::filesystem
diff --git a/kernel/src/filesystem/vfs.cpp b/kernel/src/filesystem/vfs.cpp
index 8dcae2c..8d1fd23 100644
--- a/kernel/src/filesystem/vfs.cpp
+++ b/kernel/src/filesystem/vfs.cpp
@@ -8,29 +8,20 @@
 #include <kernel/filesystem/mount_table.hpp>
 #include <kernel/filesystem/path.hpp>
 #include <kernel/filesystem/rootfs/filesystem.hpp>
-#include <kernel/filesystem/type.hpp>
 
 #include <kapi/system.hpp>
 
 #include <kstd/memory>
 #include <kstd/print>
-#include <kstd/string>
 #include <kstd/vector>
 
 #include <algorithm>
 #include <cstdint>
 #include <optional>
 #include <ranges>
-#include <span>
 #include <string_view>
 #include <utility>
 
-extern "C"
-{
-  extern kernel::filesystem::type const * const __start_vfs_type_descriptors;
-  extern kernel::filesystem::type const * const __stop_vfs_type_descriptors;
-}
-
 namespace
 {
   constinit auto static active_vfs = std::optional<kernel::filesystem::vfs>{};
@@ -50,14 +41,6 @@ namespace kernel::filesystem
 
   vfs::vfs()
   {
-    // Register all compiled-in filesystems
-    auto type_descriptors = std::span{&__start_vfs_type_descriptors, &__stop_vfs_type_descriptors} |
-                            std::views::filter([](auto p) { return p != nullptr; });
-    std::ranges::for_each(type_descriptors, [this](auto descriptor) {
-      kstd::println("[FILESYSTEM] registering '{}'", descriptor->name());
-      m_filesystems.emplace(descriptor->name(), descriptor);
-    });
-
     // mount rootfs at /
     auto root_fs = kstd::make_shared<rootfs::filesystem>();
     root_fs->mount(nullptr);
diff --git a/kernel/src/main.cpp b/kernel/src/main.cpp
index 6985e94..5063d18 100644
--- a/kernel/src/main.cpp
+++ b/kernel/src/main.cpp
@@ -1,3 +1,4 @@
+#include "kernel/filesystem/type_registry.hpp"
 #include <kernel/devices/storage/management.hpp>
 #include <kernel/filesystem/open_file_table.hpp>
 #include <kernel/filesystem/vfs.hpp>
@@ -138,6 +139,7 @@ auto main() -> int
   kernel::filesystem::open_file_table::init();
   kstd::println("[OS] Global open file table initialized.");
 
+  kernel::filesystem::type_registry::init();
   kernel::filesystem::vfs::init();
   kstd::println("[OS] Virtual filesystem initialized.");