Merge branch 'symbolic-links' into 'develop-BA-FS26'

Symbolic links

See merge request teachos/kernel!29

13 files changed, 161 insertions, 43 deletions

diff --git a/kernel/include/kernel/filesystem/constants.hpp b/kernel/include/kernel/filesystem/constants.hpp
new file mode 100644
index 0000000..aff512a
--- /dev/null
+++ b/kernel/include/kernel/filesystem/constants.hpp
@@ -0,0 +1,13 @@
+#ifndef TEACH_OS_KERNEL_FILESYSTEM_CONSTANTS_HPP
+#define TEACH_OS_KERNEL_FILESYSTEM_CONSTANTS_HPP
+
+#include <cstddef>
+namespace kernel::filesystem::constants
+{
+  constexpr size_t inline max_path_length = 4096;
+
+  constexpr size_t inline symlink_max_path_length = 4096;
+  constexpr size_t inline symloop_max = 40;
+}  // namespace kernel::filesystem::constants
+
+#endif
\ No newline at end of file
diff --git a/kernel/include/kernel/filesystem/dentry.hpp b/kernel/include/kernel/filesystem/dentry.hpp
index 94fa39a..bd62735 100644
--- a/kernel/include/kernel/filesystem/dentry.hpp
+++ b/kernel/include/kernel/filesystem/dentry.hpp
@@ -24,7 +24,7 @@ namespace kernel::filesystem
     */
     enum class dentry_flags : uint32_t
     {
-      dcache_mounted = 1 << 15
+      mounted = 1 << 15
     };
 
     /**
@@ -55,6 +55,12 @@ namespace kernel::filesystem
     [[nodiscard]] auto get_name() const -> std::string_view;
 
     /**
+      @brief Get the full path of the dentry by traversing up to the root.
+      @return The full path of the dentry.
+     */
+    [[nodiscard]] auto get_full_path() const -> kstd::string;
+
+    /**
     @brief Add a @p child dentry.
     @param child The child dentry to add.
     */
diff --git a/kernel/include/kernel/filesystem/devfs/inode.hpp b/kernel/include/kernel/filesystem/devfs/inode.hpp
index 0fab280..e428891 100644
--- a/kernel/include/kernel/filesystem/devfs/inode.hpp
+++ b/kernel/include/kernel/filesystem/devfs/inode.hpp
@@ -14,11 +14,6 @@ namespace kernel::filesystem::devfs
   struct inode : kernel::filesystem::inode
   {
     /**
-    @brief Create a devfs inode. The inode is initialized with the appropriate kind (directory).
-    */
-    inode();
-
-    /**
     @brief Reads from the devfs directory inode.
     @param buffer Destination buffer.
     @param offset Read offset in bytes.
@@ -35,6 +30,12 @@ namespace kernel::filesystem::devfs
     @return Number of bytes written (always 0 because writes are not supported for this inode).
     */
     auto write(void const * buffer, size_t offset, size_t size) -> size_t override;
+
+    /**
+    @brief Check if this inode represents a directory.
+    @return returns true, since this inode represents the /dev directory in the devfs filesystem.
+    */
+    [[nodiscard]] auto is_directory() const -> bool override;
   };
 }  // namespace kernel::filesystem::devfs
 
diff --git a/kernel/include/kernel/filesystem/device_inode.hpp b/kernel/include/kernel/filesystem/device_inode.hpp
index 2f79fca..f4aa2d1 100644
--- a/kernel/include/kernel/filesystem/device_inode.hpp
+++ b/kernel/include/kernel/filesystem/device_inode.hpp
@@ -50,6 +50,12 @@ namespace kernel::filesystem
     */
     [[nodiscard]] auto device() const -> kstd::shared_ptr<kapi::devices::device> const &;
 
+    /**
+    @brief Check if this inode represents a device.
+    @return returns true, since this indoe is a device inode and represents a device.
+    */
+    [[nodiscard]] auto is_device() const -> bool override;
+
   private:
     kstd::shared_ptr<kapi::devices::device> m_device;
   };
diff --git a/kernel/include/kernel/filesystem/ext2/filesystem.hpp b/kernel/include/kernel/filesystem/ext2/filesystem.hpp
index 516e71d..d22433f 100644
--- a/kernel/include/kernel/filesystem/ext2/filesystem.hpp
+++ b/kernel/include/kernel/filesystem/ext2/filesystem.hpp
@@ -35,6 +35,7 @@ namespace kernel::filesystem::ext2
     constexpr uint16_t inline mode_mask = 0xF000;
     constexpr uint16_t inline mode_regular = 0x8000;
     constexpr uint16_t inline mode_directory = 0x4000;
+    constexpr uint16_t inline mode_symbolic_link = 0xA000;
   }  // namespace constants
 
   /**
diff --git a/kernel/include/kernel/filesystem/ext2/inode.hpp b/kernel/include/kernel/filesystem/ext2/inode.hpp
index 9291eea..b8f892a 100644
--- a/kernel/include/kernel/filesystem/ext2/inode.hpp
+++ b/kernel/include/kernel/filesystem/ext2/inode.hpp
@@ -20,7 +20,7 @@ namespace kernel::filesystem::ext2
   {
     uint16_t mode;
     uint16_t uid;
-    uint32_t size;
+    uint32_t size;  // TODO BA-FS26 signed?
     uint32_t atime;
     uint32_t ctime;
     uint32_t mtime;
@@ -42,8 +42,10 @@ namespace kernel::filesystem::ext2
   {
     /**
     @brief Create an ext2 inode associated with the given filesystem.
+    @param fs The ext2 filesystem that this inode belongs to.
+    @param data The data associated with this inode, read from the disk.
     */
-    explicit inode(filesystem * fs);
+    explicit inode(filesystem * fs, inode_data const & data);
 
     /**
     @brief Reads from the ext2 inode into a @p buffer, starting at the specified @p offset and for a given @p size.
@@ -65,12 +67,32 @@ namespace kernel::filesystem::ext2
     auto write(void const * buffer, size_t offset, size_t size) -> size_t override;
 
     /**
-    @brief The raw inode data as read from the disk.
-    */
-    inode_data m_data{};
+    @brief Get the data associated with this inode.
+    @return A reference to the inode data.
+     */
+    [[nodiscard]] auto data() const -> inode_data const &;
+
+    /**
+    @brief Check if this inode represents a directory.
+    @return returns true if this inode represents a directory, false otherwise.
+     */
+    [[nodiscard]] auto is_directory() const -> bool override;
+
+    /**
+    @brief Check if this inode represents a regular file.
+    @return returns true if this inode represents a regular file, false otherwise.
+     */
+    [[nodiscard]] auto is_regular() const -> bool override;
+
+    /**
+    @brief Check if this inode represents a symbolic link.
+    @return returns true if this inode represents a symbolic link, false otherwise.
+     */
+    [[nodiscard]] auto is_symbolic_link() const -> bool override;
 
   private:
     filesystem * m_filesystem;
+    inode_data m_data{};
   };
 }  // namespace kernel::filesystem::ext2
 
diff --git a/kernel/include/kernel/filesystem/inode.hpp b/kernel/include/kernel/filesystem/inode.hpp
index 5208be2..b34b921 100644
--- a/kernel/include/kernel/filesystem/inode.hpp
+++ b/kernel/include/kernel/filesystem/inode.hpp
@@ -11,20 +11,9 @@ namespace kernel::filesystem
   struct inode
   {
     /**
-    @brief Represents the kind of an inode.
+    @brief Create an inode.
     */
-    enum class inode_kind
-    {
-      regular,
-      directory,
-      device
-    };
-
-    /**
-    @brief Create an inode with the given @p kind.
-    @param kind The kind of the inode.
-    */
-    explicit inode(inode_kind kind);
+    inode() = default;
 
     /**
     @brief Virtual destructor for the inode.
@@ -55,23 +44,25 @@ namespace kernel::filesystem
     @brief Returns whether the inode is a directory.
     @return true if the inode is a directory, false otherwise.
     */
-    [[nodiscard]] auto is_directory() const -> bool;
+    [[nodiscard]] virtual auto is_directory() const -> bool;
 
     /**
     @brief Returns whether the inode is a regular file.
     @return true if the inode is a regular file, false otherwise.
     */
-    [[nodiscard]] auto is_regular() const -> bool;
+    [[nodiscard]] virtual auto is_regular() const -> bool;
 
     /**
     @brief Returns whether the inode is a device.
     @return true if the inode is a device, false otherwise.
     */
-    [[nodiscard]] auto is_device() const -> bool;
+    [[nodiscard]] virtual auto is_device() const -> bool;
 
-    // TODO BA-FS26 avoid public member
-  public:
-    inode_kind m_kind{inode_kind::regular};
+    /**
+    @brief Returns whether the inode is a symbolic link.
+    @return true if the inode is a symbolic link, false otherwise.
+    */
+    [[nodiscard]] virtual auto is_symbolic_link() const -> bool;
   };
 }  // namespace kernel::filesystem
 
diff --git a/kernel/include/kernel/filesystem/mount_table.hpp b/kernel/include/kernel/filesystem/mount_table.hpp
index 00277ea..8e57d9e 100644
--- a/kernel/include/kernel/filesystem/mount_table.hpp
+++ b/kernel/include/kernel/filesystem/mount_table.hpp
@@ -39,13 +39,19 @@ namespace kernel::filesystem
     [[nodiscard]] auto remove_mount(std::string_view path) -> operation_result;
 
     /**
-    @brief Finds the mount with the longest prefix matching the given @p path. This method is used to determine which
-    mounted filesystem should handle a given path lookup.
+    @brief Finds the mount with the longest prefix matching the given @p path.
     @param path The path to match against the mount paths in the table.
     @return A pointer to the mount with the longest matching prefix, or a null pointer if no mount matches the path.
     */
     [[nodiscard]] auto find_longest_prefix_mount(std::string_view path) const -> kstd::shared_ptr<mount>;
 
+    /**
+    @brief Finds the mount with the exact mount path matching the given @p path.
+    @param path The path to match against the mount paths in the table.
+    @return A pointer to the mount with the exact matching path, or a null pointer if no mount matches the path.
+    */
+    [[nodiscard]] auto find_exact_mount(std::string_view path) const -> kstd::shared_ptr<mount>;
+
   private:
     [[nodiscard]] auto has_child_mounts(kstd::shared_ptr<mount> const & parent_mount) const -> bool;
 
diff --git a/kernel/include/kernel/filesystem/open_file_table.hpp b/kernel/include/kernel/filesystem/open_file_table.hpp
index 2f9a421..694f3b6 100644
--- a/kernel/include/kernel/filesystem/open_file_table.hpp
+++ b/kernel/include/kernel/filesystem/open_file_table.hpp
@@ -34,10 +34,10 @@ namespace kernel::filesystem
 
     /**
     @brief Add a file to the open file table.
-    @param f The file descriptor to add.
+    @param fd The file descriptor to add.
     @return The file descriptor index assigned to the file, or -1 on failure.
     */
-    auto add_file(kstd::shared_ptr<open_file_descriptor> const & f) -> int;
+    auto add_file(kstd::shared_ptr<open_file_descriptor> const & fd) -> int;
 
     /**
     @brief Get a file from the open file table.
diff --git a/kernel/include/kernel/filesystem/path.hpp b/kernel/include/kernel/filesystem/path.hpp
new file mode 100644
index 0000000..4845bf1
--- /dev/null
+++ b/kernel/include/kernel/filesystem/path.hpp
@@ -0,0 +1,71 @@
+#ifndef TEACH_OS_KERNEL_FILESYSTEM_PATH_HPP
+#define TEACH_OS_KERNEL_FILESYSTEM_PATH_HPP
+
+#include <kernel/filesystem/constants.hpp>
+
+#include <kstd/string>
+
+#include <ranges>
+#include <string_view>
+
+namespace kernel::filesystem::path
+{
+  /**
+  @brief Provides utilities for handling filesystem paths, including validation and splitting into components.
+  */
+
+  /**
+  @brief Checks if the given path is within the maximum allowed length.
+  @param path The path to check.
+  @return true if the path length is valid, false otherwise.
+  */
+  auto inline is_valid_path_length(std::string_view path) -> bool
+  {
+    return path.length() < kernel::filesystem::constants::max_path_length;
+  }
+
+  /**
+  @brief Checks if the given path is a valid absolute path (starts with '/').
+  @param path The path to check.
+  @return true if the path is a valid absolute path, false otherwise.
+  */
+  auto inline is_valid_absolute_path(std::string_view path) -> bool
+  {
+    return !path.empty() && path.front() == '/' && is_valid_path_length(path);
+  }
+
+  /**
+  @brief Checks if the given path is a valid relative path (doesn't start with '/').
+  @param path The path to check.
+  @return true if the path is a valid relative path, false otherwise.
+  */
+  auto inline is_valid_relative_path(std::string_view path) -> bool
+  {
+    return !path.empty() && path.front() != '/' && is_valid_path_length(path);
+  }
+
+  /**
+  @brief Checks if the given path is a valid path (either absolute or relative).
+  @param path The path to check.
+  @return true if the path is a valid path, false otherwise.
+  */
+  auto inline is_valid_path(std::string_view path) -> bool
+  {
+    return is_valid_absolute_path(path) || is_valid_relative_path(path);
+  }
+
+  /**
+  @brief Splits the given path into its components.
+  @param path The path to split.
+  @return A range of strings representing the components of the path.
+  */
+  auto inline split(std::string_view path)
+  {
+    return std::views::split(path, '/') | std::views::filter([](auto const & part) { return !part.empty(); }) |
+           std::views::transform(
+               [](auto const & part) { return kstd::string(std::string_view(part.begin(), part.end())); });
+  }
+
+}  // namespace kernel::filesystem::path
+
+#endif  // TEACH_OS_KERNEL_FILESYSTEM_PATH_HPP
\ No newline at end of file
diff --git a/kernel/include/kernel/filesystem/rootfs/inode.hpp b/kernel/include/kernel/filesystem/rootfs/inode.hpp
index 37d0a30..58035ea 100644
--- a/kernel/include/kernel/filesystem/rootfs/inode.hpp
+++ b/kernel/include/kernel/filesystem/rootfs/inode.hpp
@@ -22,11 +22,6 @@ namespace kernel::filesystem::rootfs
   struct inode : kernel::filesystem::inode
   {
     /**
-    @brief Create a rootfs inode. The inode is initialized with the appropriate kind (directory).
-    */
-    inode();
-
-    /**
     @brief Reads from the rootfs directory inode.
     @param buffer Destination buffer.
     @param offset Read offset in bytes.
@@ -57,6 +52,12 @@ namespace kernel::filesystem::rootfs
     */
     auto lookup_child(std::string_view name) -> kstd::shared_ptr<inode>;
 
+    /**
+    @brief Check if this inode represents a directory.
+    @return returns true, since this inode represents the root directory in the rootfs filesystem.
+    */
+    [[nodiscard]] auto is_directory() const -> bool override;
+
   private:
     kstd::vector<std::pair<kstd::string, kstd::shared_ptr<inode>>> m_children;
   };
diff --git a/kernel/include/kernel/filesystem/vfs.hpp b/kernel/include/kernel/filesystem/vfs.hpp
index 881f458..7e66fb7 100644
--- a/kernel/include/kernel/filesystem/vfs.hpp
+++ b/kernel/include/kernel/filesystem/vfs.hpp
@@ -77,8 +77,8 @@ namespace kernel::filesystem
     auto init_internal() -> void;
 
     [[nodiscard]] auto resolve_path(std::string_view path) -> kstd::shared_ptr<dentry>;
-    auto do_mount_internal(std::string_view path, kstd::shared_ptr<dentry> const & mount_point_dentry,
-                           kstd::shared_ptr<filesystem> const & fs) -> void;
+    auto do_mount_internal(kstd::shared_ptr<dentry> const & mount_point_dentry, kstd::shared_ptr<filesystem> const & fs)
+        -> void;
 
     mount_table m_mount_table;
   };
diff --git a/kernel/include/kernel/test_support/filesystem/inode.hpp b/kernel/include/kernel/test_support/filesystem/inode.hpp
index 9d17917..8a76437 100644
--- a/kernel/include/kernel/test_support/filesystem/inode.hpp
+++ b/kernel/include/kernel/test_support/filesystem/inode.hpp
@@ -9,10 +9,10 @@ namespace kernel::tests::filesystem
 {
   struct inode : kernel::filesystem::inode
   {
-    inode();
-
     auto read(void * buffer, size_t offset, size_t size) const -> size_t override;
     auto write(void const * buffer, size_t offset, size_t size) -> size_t override;
+
+    [[nodiscard]] auto is_regular() const -> bool override;
   };
 }  // namespace kernel::tests::filesystem