ext2.h

Go to the documentation of this file.

// MIT License
//
// Copyright (c) 2026 Christian Spoo
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT of OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
 
#ifndef _MINIOS_FS_EXT2_H_
#define _MINIOS_FS_EXT2_H_
 
#include <miniOS/types.h>
#include <miniOS/fs/fs_types.h>
 
typedef struct vfs_inode_info vfs_inode_info_t;
 
/* -----------------------------------------------------------------------
 * ext2 on-disk constants
 * ---------------------------------------------------------------------- */
#define EXT2_MAGIC    0xEF53
#define EXT2_ROOT_INO 2
 
/* Inode mode type bits */
#define EXT2_S_IFREG  0x8000   /* regular file */
#define EXT2_S_IFDIR  0x4000   /* directory */
#define EXT2_S_IFLNK  0xA000   /* symbolic link */
#define EXT2_S_IFCHR  0x2000   /* character device */
#define EXT2_S_IFBLK  0x6000   /* block device */
 
/* Directory entry file_type values */
#define EXT2_FT_UNKNOWN   0
#define EXT2_FT_REG_FILE  1
#define EXT2_FT_DIR       2
#define EXT2_FT_CHRDEV    3
#define EXT2_FT_BLKDEV    4
#define EXT2_FT_SYMLINK   7
 
/* -----------------------------------------------------------------------
 * On-disk structures (all little-endian; packed to match disk layout)
 * ---------------------------------------------------------------------- */
 
/* ext2 superblock — located at byte offset 1024 from partition start
 * (block 1 when block_size == 1024) */
typedef struct {
    uint32_t s_inodes_count;
    uint32_t s_blocks_count;
    uint32_t s_r_blocks_count;
    uint32_t s_free_blocks_count;
    uint32_t s_free_inodes_count;
    uint32_t s_first_data_block;   /* 1 for 1024-byte blocks, 0 for 2048+ */
    uint32_t s_log_block_size;     /* block_size = 1024 << s_log_block_size */
    uint32_t s_log_frag_size;
    uint32_t s_blocks_per_group;
    uint32_t s_frags_per_group;
    uint32_t s_inodes_per_group;
    uint32_t s_mtime;
    uint32_t s_wtime;
    uint16_t s_mnt_count;
    uint16_t s_max_mnt_count;
    uint16_t s_magic;              /* 0xEF53 */
    uint16_t s_state;
    uint16_t s_errors;
    uint16_t s_minor_rev_level;
    uint32_t s_lastcheck;
    uint32_t s_checkinterval;
    uint32_t s_creator_os;
    uint32_t s_rev_level;          /* 0 = original, 1 = dynamic */
    uint16_t s_def_resuid;
    uint16_t s_def_resgid;
    /* EXT2_DYNAMIC_REV fields (only valid if s_rev_level >= 1) */
    uint32_t s_first_ino;
    uint16_t s_inode_size;
    uint16_t s_block_group_nr;
    uint32_t s_feature_compat;
    uint32_t s_feature_incompat;
    uint32_t s_feature_ro_compat;
    uint8_t  s_uuid[16];
    uint8_t  s_volume_name[16];
    uint8_t  s_last_mounted[64];
    uint32_t s_algo_bitmap;
    /* pad to 1024 bytes */
    uint8_t  s_padding[820];
} __attribute__((packed)) ext2_superblock_t;
 
/* Block Group Descriptor — 32 bytes each, in a table at block 2
 * (for 1024-byte blocks) */
typedef struct {
    uint32_t bg_block_bitmap;
    uint32_t bg_inode_bitmap;
    uint32_t bg_inode_table;
    uint16_t bg_free_blocks_count;
    uint16_t bg_free_inodes_count;
    uint16_t bg_used_dirs_count;
    uint16_t bg_pad;
    uint8_t  bg_reserved[12];
} __attribute__((packed)) ext2_bgd_t;
 
/* Inode — 128 bytes (rev 0) or s_inode_size bytes (rev 1) */
typedef struct {
    uint16_t i_mode;        /* file type + permissions */
    uint16_t i_uid;
    uint32_t i_size;        /* file size in bytes */
    uint32_t i_atime;
    uint32_t i_ctime;
    uint32_t i_mtime;
    uint32_t i_dtime;
    uint16_t i_gid;
    uint16_t i_links_count;
    uint32_t i_blocks;      /* count in 512-byte units */
    uint32_t i_flags;
    uint32_t i_osd1;
    uint32_t i_block[15];   /* 0-11: direct, 12: indirect, 13: dbl-indirect, 14: triple */
    uint32_t i_generation;
    uint32_t i_file_acl;
    uint32_t i_dir_acl;
    uint32_t i_faddr;
    uint8_t  i_osd2[12];
} __attribute__((packed)) ext2_inode_t;
 
/* Directory entry — variable length */
typedef struct {
    uint32_t inode;
    uint16_t rec_len;
    uint8_t  name_len;
    uint8_t  file_type;   /* 0=unknown, 1=reg, 2=dir, 7=symlink */
    char     name[];      /* NOT null-terminated; length = name_len */
} __attribute__((packed)) ext2_dirent_t;
 
/* -----------------------------------------------------------------------
 * Public API
 * ---------------------------------------------------------------------- */

int ext2_mount(uint64_t part_lba_start, uint64_t part_lba_end);

int ext2_lookup(const char *path, vfs_inode_info_t *out);

int ext2_read_file(uint32_t ino, uint64_t off, void *buf, uint32_t len);

int ext2_readdir(uint32_t dir_ino, uint64_t *offset, vfs_dirent_cb_t cb, void *ud);

int ext2_write_file(uint32_t ino, uint64_t off, const void *buf, uint32_t len);

int ext2_create(uint32_t parent_ino, const char *name, uint16_t mode, uint32_t *out_ino);

int ext2_flush_inode(uint32_t ino);

int ext2_truncate_inode(uint32_t ino, uint64_t new_size);

int ext2_readlink(uint32_t ino, char *buf, uint32_t len);

int ext2_symlink(uint32_t parent_ino, const char *name, const char *target);

int ext2_mknod(uint32_t parent_ino, const char *name, uint16_t mode,
               uint32_t dev, uint32_t *out_ino);

int ext2_mkdir(uint32_t parent_ino, const char *name, uint32_t *out_ino);

int ext2_rmdir(uint32_t parent_ino, const char *name);
 
/* -----------------------------------------------------------------------
 * Filesystem type registry integration
 * ---------------------------------------------------------------------- */

void ext2_init(void);
 
#endif /* _MINIOS_FS_EXT2_H_ */