From 93bca4c2a7c1852fc89df6965c835a7dbbdd6512 Mon Sep 17 00:00:00 2001
From: Lukas Oesch <lukasoesch20@gmail.com>
Date: Thu, 2 Apr 2026 09:50:14 +0200
Subject: read ext2 superblock and check the magic number

---
 .../include/kernel/filesystem/ext2/filesystem.hpp  | 11 +++-
 kernel/src/filesystem/ext2/filesystem.cpp          | 66 ++++++++++++----------
 2 files changed, 47 insertions(+), 30 deletions(-)

(limited to 'kernel')

diff --git a/kernel/include/kernel/filesystem/ext2/filesystem.hpp b/kernel/include/kernel/filesystem/ext2/filesystem.hpp
index 078da31..176d83c 100644
--- a/kernel/include/kernel/filesystem/ext2/filesystem.hpp
+++ b/kernel/include/kernel/filesystem/ext2/filesystem.hpp
@@ -2,20 +2,29 @@
 #define TEACH_OS_KERNEL_FILESYSTEM_EXT2_FILESYSTEM_HPP
 
 #include "kapi/devices/device.hpp"
+
+#include "kernel/filesystem/ext2/superblock.hpp"
 #include "kernel/filesystem/filesystem.hpp"
 #include "kernel/filesystem/inode.hpp"
 
 #include <kstd/memory>
 
+#include <cstddef>
 #include <string_view>
 
 namespace kernel::filesystem::ext2
 {
   struct filesystem : kernel::filesystem::filesystem
   {
-    auto mount(kstd::shared_ptr<kapi::devices::device> const & device) -> int override;
+    auto mount(kstd::shared_ptr<kapi::devices::device> const & device) -> int;
     auto lookup(kstd::shared_ptr<kernel::filesystem::inode> const & parent, std::string_view name)
         -> kstd::shared_ptr<kernel::filesystem::inode> override;
+
+  private:
+    auto get_block_size() -> size_t;
+    auto get_inode_size() -> size_t;
+
+    superblock m_superblock;
   };
 }  // namespace kernel::filesystem::ext2
 
diff --git a/kernel/src/filesystem/ext2/filesystem.cpp b/kernel/src/filesystem/ext2/filesystem.cpp
index eb9edc4..a3425b5 100644
--- a/kernel/src/filesystem/ext2/filesystem.cpp
+++ b/kernel/src/filesystem/ext2/filesystem.cpp
@@ -1,10 +1,10 @@
 #include "kernel/filesystem/ext2/filesystem.hpp"
 
-#include "kernel/devices/block_device_utils.hpp"
 #include "kapi/devices/device.hpp"
+
+#include "kernel/devices/block_device_utils.hpp"
 #include "kernel/filesystem/ext2/inode.hpp"
 #include "kernel/filesystem/ext2/superblock.hpp"
-#include "kernel/filesystem/filesystem.hpp"
 #include "kernel/filesystem/inode.hpp"
 
 #include <kstd/memory>
@@ -17,37 +17,35 @@ namespace kernel::filesystem::ext2
 {
   namespace
   {
-    // constexpr size_t SUPERBLOCK_OFFSET = 1024;
-    // constexpr uint16_t EXT2_MAGIC = 0xEF53;
-
-    // // Mode bits
-    // constexpr uint16_t S_IFMT = 0xF000;
-    // constexpr uint16_t S_IFREG = 0x8000;
-    // constexpr uint16_t S_IFDIR = 0x4000;
-
-    // auto S_ISREG(uint16_t mode) -> bool
-    // {
-    //   return (mode & S_IFMT) == S_IFREG;
-    // }
-    // auto S_ISDIR(uint16_t mode) -> bool
-    // {
-    //   return (mode & S_IFMT) == S_IFDIR;
-    // }
-
-    // auto get_block_size(superblock const & superblock) -> size_t
-    // {
-    //   return 1024U << superblock.log_block_size;
-    // }
-
-    // auto get_inode_size(superblock const & superblock) -> size_t
-    // {
-    //   return superblock.rev_level == 0 ? 128 : superblock.inode_size;
-    // }
+    constexpr size_t SUPERBLOCK_OFFSET = 1024;
+    constexpr uint16_t EXT2_MAGIC = 0xEF53;
+
+    // Mode bits
+    constexpr uint16_t S_IFMT = 0xF000;
+    constexpr uint16_t S_IFREG = 0x8000;
+    constexpr uint16_t S_IFDIR = 0x4000;
+
+    auto S_ISREG(uint16_t mode) -> bool
+    {
+      return (mode & S_IFMT) == S_IFREG;
+    }
+    auto S_ISDIR(uint16_t mode) -> bool
+    {
+      return (mode & S_IFMT) == S_IFDIR;
+    }
   }  // namespace
 
   auto filesystem::mount(kstd::shared_ptr<kapi::devices::device> const & device) -> int
   {
-    kernel::filesystem::filesystem::mount(device);  // TODO BA-FS26 error handling?
+    m_device = device;
+
+    kernel::devices::block_device_utils::read(m_device, &m_superblock, SUPERBLOCK_OFFSET, sizeof(m_superblock));
+
+    if (m_superblock.magic != EXT2_MAGIC)
+    {
+      return -1;
+    }
+
     // TODO BA-FS26 load proper root inode from ext2 metadata
     // m_root_inode = inode{inode_kind::directory};
 
@@ -69,4 +67,14 @@ namespace kernel::filesystem::ext2
 
     return kstd::make_shared<inode>();
   }
+
+  auto filesystem::get_block_size() -> size_t
+  {
+    return 1024U << m_superblock.log_block_size;
+  }
+
+  auto filesystem::get_inode_size() -> size_t
+  {
+    return m_superblock.rev_level == 0 ? 128 : m_superblock.inode_size;
+  }
 }  // namespace kernel::filesystem::ext2
-- 
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