added fat32 img, wip parse bootsector

8 files changed, 185 insertions, 3 deletions

diff --git a/kernel/CMakeLists.txt b/kernel/CMakeLists.txt
index e7464658..aacb5d97 100644
--- a/kernel/CMakeLists.txt
+++ b/kernel/CMakeLists.txt
@@ -86,6 +86,7 @@ target_sources("kernel_lib" PRIVATE
     "kernel/filesystems/ext2/write_batch.cpp"
 
     # fat32 Filesystem
+    "kernel/filesystems/fat32/error.cpp"
     "kernel/filesystems/fat32/filesystem.cpp"
     "kernel/filesystems/fat32/inode.cpp"
     "kernel/filesystems/fat32/module.cpp"
diff --git a/kernel/kernel/filesystems/fat32/boot_sector.hpp b/kernel/kernel/filesystems/fat32/boot_sector.hpp
new file mode 100644
index 00000000..c66e2fc5
--- /dev/null
+++ b/kernel/kernel/filesystems/fat32/boot_sector.hpp
@@ -0,0 +1,18 @@
+#ifndef TEACHOS_KERNEL_FILESYSTEMS_FAT32_BOOT_SECTOR_HPP
+#define TEACHOS_KERNEL_FILESYSTEMS_FAT32_BOOT_SECTOR_HPP
+
+#include <kstd/bitfield_enum.hpp>
+
+#include <cstdint>
+
+namespace kernel::filesystems::fat32
+{
+  //! The boot-sector in the fat32 filesystem.
+  struct boot_sector  // todo gnu::packed?
+  {
+    std::uint16_t bytes_per_sector;
+    std::uint16_t boot_signature;
+  };
+}  // namespace kernel::filesystems::fat32
+
+#endif
\ No newline at end of file
diff --git a/kernel/kernel/filesystems/fat32/driver_state.hpp b/kernel/kernel/filesystems/fat32/driver_state.hpp
new file mode 100644
index 00000000..55b90724
--- /dev/null
+++ b/kernel/kernel/filesystems/fat32/driver_state.hpp
@@ -0,0 +1,23 @@
+#ifndef TEACHOS_KERNEL_FILESYSTEMS_FAT32_DRIVER_STATE_HPP
+#define TEACHOS_KERNEL_FILESYSTEMS_FAT32_DRIVER_STATE_HPP
+
+#include <kernel/filesystems/fat32/boot_sector.hpp>
+#include <kernel/vfs/driver_state.hpp>
+#include <kernel/vfs/inode.hpp>
+
+#include <kapi/tracked_mutex.hpp>
+
+#include <kstd/memory.hpp>
+#include <kstd/vector.hpp>
+
+namespace kernel::filesystems::fat32
+{
+
+  struct driver_state : vfs::driver_state
+  {
+    struct boot_sector boot_sector{};
+  };
+
+}  // namespace kernel::filesystems::fat32
+
+#endif
\ No newline at end of file
diff --git a/kernel/kernel/filesystems/fat32/error.cpp b/kernel/kernel/filesystems/fat32/error.cpp
new file mode 100644
index 00000000..4a18eb9e
--- /dev/null
+++ b/kernel/kernel/filesystems/fat32/error.cpp
@@ -0,0 +1,58 @@
+#include <kernel/filesystems/fat32/error.hpp>
+
+#include <kernel/vfs/error.hpp>
+
+#include <kstd/system_error.hpp>
+
+#include <string_view>
+
+namespace kernel::filesystems::fat32
+{
+
+  namespace
+  {
+    struct category_t final : kstd::error_category
+    {
+      [[nodiscard]] constexpr auto name() const noexcept -> std::string_view override
+      {
+        return "fat32";
+      }
+
+      [[nodiscard]] constexpr auto message(int value) const noexcept -> std::string_view override
+      {
+        switch (static_cast<errc>(value))
+        {
+          case errc::invalid_boot_signature:
+            return "invalid boot signature";
+          default:
+            return "unknown fat32 error";
+        };
+      }
+
+      [[nodiscard]] constexpr auto equivalent(int code, kstd::error_condition const & condition) const noexcept
+          -> bool override
+      {
+        switch (static_cast<errc>(code))
+        {
+          case errc::invalid_boot_signature:
+            if (condition.category() == kernel::vfs::category())
+            {
+              return condition.value() == static_cast<int>(kernel::vfs::errc::invalid_filesystem);
+            }
+            else if (condition.category() == kstd::generic_category())
+            {
+              return condition.value() == static_cast<int>(kstd::errc::invalid_argument);
+            }
+            break;
+        }
+        return kstd::error_category::equivalent(code, condition);
+      }
+    } constexpr inline fat32_category_instance{};
+  }  // namespace
+
+  [[nodiscard]] auto category() noexcept -> kstd::error_category const &
+  {
+    return fat32_category_instance;
+  }
+
+}  // namespace kernel::filesystems::fat32
diff --git a/kernel/kernel/filesystems/fat32/error.hpp b/kernel/kernel/filesystems/fat32/error.hpp
new file mode 100644
index 00000000..6955be3f
--- /dev/null
+++ b/kernel/kernel/filesystems/fat32/error.hpp
@@ -0,0 +1,33 @@
+#ifndef TEACHOS_KERNEL_FILESYSTEMS_FAT32_ERROR_HPP
+#define TEACHOS_KERNEL_FILESYSTEMS_FAT32_ERROR_HPP
+
+#include <kernel/vfs/error.hpp>
+
+#include <kstd/system_error.hpp>
+
+#include <type_traits>
+
+namespace kernel::filesystems::fat32
+{
+  enum struct errc : int
+  {
+    invalid_boot_signature = 1
+  };
+
+  [[nodiscard]] auto category() noexcept -> kstd::error_category const &;
+
+  [[nodiscard]] constexpr auto inline make_error_code(errc error) noexcept -> kstd::error_code
+  {
+    return {static_cast<int>(error), category()};
+  }
+}  // namespace kernel::filesystems::fat32
+
+namespace kstd
+{
+  template<>
+  struct is_error_code_enum<kernel::filesystems::fat32::errc> : std::true_type
+  {
+  };
+}  // namespace kstd
+
+#endif
\ No newline at end of file
diff --git a/kernel/kernel/filesystems/fat32/filesystem.cpp b/kernel/kernel/filesystems/fat32/filesystem.cpp
index a66a9b25..4899f0bd 100644
--- a/kernel/kernel/filesystems/fat32/filesystem.cpp
+++ b/kernel/kernel/filesystems/fat32/filesystem.cpp
@@ -1,5 +1,7 @@
 #include <kernel/filesystems/fat32/filesystem.hpp>
 
+#include <kernel/filesystems/fat32/boot_sector.hpp>
+#include <kernel/filesystems/fat32/error.hpp>
 #include <kernel/filesystems/fat32/inode.hpp>
 #include <kernel/vfs/error.hpp>
 #include <kernel/vfs/filesystem.hpp>
@@ -7,8 +9,11 @@
 #include <kapi/filesystem.hpp>
 
 #include <kstd/memory.hpp>
+#include <kstd/print.hpp>
 #include <kstd/result.hpp>
+#include <kstd/span.hpp>
 #include <kstd/system_error.hpp>
+#include <kstd/units.hpp>
 
 #include <cstdint>
 #include <optional>
@@ -20,11 +25,31 @@ namespace kernel::filesystems::fat32
 
   auto filesystem::probe(inode_ptr const & inode) const -> kstd::result<std::uint32_t>
   {
-    if (inode)
+    auto boot_sector = fat32::boot_sector{};
+    auto const boot_signature_bytes = kstd::raw_bytes(boot_sector.boot_signature);
+    auto boot_signature_result = inode->read(boot_signature_bytes, kstd::bytes{constants::boot_signature_offset});
+
+    if (!boot_signature_result)
     {
-      return kstd::failure(vfs::errc::invalid_argument);
+      return kstd::failure(boot_signature_result.error());
     }
 
+    if (boot_sector.boot_signature != constants::boot_signature)
+    {
+      return kstd::failure(errc::invalid_boot_signature);
+    }
+
+    auto const bytes_per_sector_bytes = kstd::raw_bytes(boot_sector.bytes_per_sector);
+    auto bytes_per_sector_result = inode->read(bytes_per_sector_bytes, kstd::bytes{constants::bytes_per_sector_offset});
+
+    if (!bytes_per_sector_result)
+    {
+      return kstd::failure(bytes_per_sector_result.error());
+    }
+
+    kstd::println("[OS:FAT32] bytes_per_sector: {}", boot_sector.bytes_per_sector);
+    kstd::println("[OS:FAT32] boot_signature: {:#06X}", boot_sector.boot_signature);
+
     return 0;
   }
 
diff --git a/kernel/kernel/filesystems/fat32/filesystem.hpp b/kernel/kernel/filesystems/fat32/filesystem.hpp
index 8b0b4941..9c516ca9 100644
--- a/kernel/kernel/filesystems/fat32/filesystem.hpp
+++ b/kernel/kernel/filesystems/fat32/filesystem.hpp
@@ -10,6 +10,7 @@
 #include <kstd/result.hpp>
 #include <kstd/string.hpp>
 #include <kstd/system_error.hpp>
+#include <kstd/units.hpp>
 #include <kstd/vector.hpp>
 
 #include <cstdint>
@@ -18,6 +19,14 @@
 
 namespace kernel::filesystems::fat32
 {
+  //! Constants related to the fat32 filesystem.
+  namespace constants
+  {
+    constexpr kstd::bytes inline bytes_per_sector_offset = kstd::bytes{0x0B};
+    constexpr kstd::bytes inline boot_signature_offset = kstd::bytes{0x1FE};
+    constexpr std::uint16_t inline boot_signature = 0xAA55;
+  }  // namespace constants
+
   //! The File Allocation Table 32 Filesystem (fat32)
   struct filesystem : kernel::vfs::filesystem
   {
diff --git a/kernel/kernel/main.cpp b/kernel/kernel/main.cpp
index bc192950..15952547 100644
--- a/kernel/kernel/main.cpp
+++ b/kernel/kernel/main.cpp
@@ -25,6 +25,21 @@
 
 using namespace kstd::units_literals;
 
+auto run_demo_fat32() -> void
+{
+  kstd::println("[OS:DEM] Running FAT32 Demo");
+
+  kstd::println("[OS:DEM] mount /dev/ram3 to /entrance");
+  if (auto result = kapi::filesystem::mount("/dev/ram3", "/entrance"))
+  {
+    kstd::println("[OS:DEM] mounted /dev/ram3 to /entrance");
+  }
+  else
+  {
+    kapi::system::panic("[OS:DEM] failed to mount /dev/ram3 on /entrance", result.error());
+  }
+}
+
 auto run_demo() -> void
 {
   // 1) open a file
@@ -312,7 +327,7 @@ auto main() -> int
   kstd::println("[OS] Virtual filesystem initialized.");
 
   // TODO BA-FS26 remove demo code?
-  run_demo();
+  run_demo_fat32();
 
   kapi::system::panic("[OS] Returning from kernel main!");
 }