path: root/fs/ext2.c

#include "ext2.h"

#include <stdbool.h>
#include <stdint.h>


#include "mount.h"
#include "kernel.h"

#include "log.h"

#include "lib/string/string.h"

#include "interface/fs.h"

// THE SUPERBLOCK
typedef struct ext2_superblock_struct
{
    uint32_t inodes_count;
    uint32_t blocks_count;
    uint32_t blocks_reserved_count;
    uint32_t inodes_unalloc_count;
    uint32_t blocks_unalloc_count;
    uint32_t superblock_number;
    uint32_t block_size;
    uint32_t fragment_size;
    uint32_t blocks_per_group;
    uint32_t fragments_per_group;
    uint32_t inodes_per_group;
    uint8_t skip[12]; // last mount time, last written time, numer of times mounted, number of mounts before checking.
    uint16_t ext2_sig; // 0xef5
    uint16_t fs_state; 
    uint16_t error_handle; 
    uint16_t version_minor;
    uint8_t skip2[8]; // last check, check interval
    uint32_t os_id;
    uint32_t version_major;
    uint16_t uid_reserved;
    uint16_t gid_reserved;
}ext2_superblock;

/* we dont use this for now */
/*
typedef struct ext2_superblock_ext_struct
{
    uint32_t first_inode;
    uint16_t size_inode;
    uint16_t blockgroup;

    uint32_t features_opt;
    uint32_t features_req;
    uint32_t features_write;

    uint32_t blkid[4];
    char    vol_name[16];
    char    last_path[64];
    uint32_t compression;
    uint8_t prealloc_files;
    uint8_t prealloc_dirs;
    uint8_t unused[2];
    uint32_t journalid[4];
    uint32_t journal_inode;
    uint32_t journal_device;
    uint32_t orpan_head;

}ext2_superblock_ext;
*/

// BLOCKGROUP DESCRIPTOR TABLE
typedef struct ext2_blockgroup_desc_struct
{
    uint32_t addr_block_bitmap;
    uint32_t addr_inode_bitmap;;
    uint32_t addr_inode_table;
    uint16_t unalloc_blocks_count;
    uint16_t unalloc_inodes_count;
    uint16_t dir_count;
    uint8_t unused[14];
}ext2_blockgroup_desc;

typedef struct ext2_dir_struct
{
    uint32_t inode;
    uint16_t size;
    uint8_t name_length_low;
    uint8_t name_length_high;
    // name follows
}ext2_dir;

typedef struct ext2_inode_struct
{
    uint16_t permissions;
    uint16_t user_id;
    uint32_t size_low;
    uint32_t skip[4];
    uint16_t group_id;
    uint16_t hardlink_count;
    uint32_t disk_sectors;
    uint32_t flags;
    uint32_t os_specific;
    uint32_t direct_pointer[12];
    uint32_t indirect1;
    uint32_t indirect2;
    uint32_t indirect3;
    uint32_t gen_num;
    uint32_t acl; 
    uint32_t size_high;
    uint32_t frag;
    uint32_t os_spec2[3];
}ext2_inode;

static ext2_superblock *ext2_check(uint32_t ext2_start_addr)
{
    ext2_superblock *super=ext2_start_addr+1024;
    if(super->ext2_sig!=0xef53){
	kpanic("no ext2 signature found, where ram-image expected at addr: 8X%08X",ext2_start_addr+1024);
    }
    return super;
}

void ext2_dump_info(uint32_t ext2_start_addr)
{
    ext2_superblock *super=ext2_check(ext2_start_addr);
    klog("ext2 fs version %d.%d found",super->version_major, super->version_minor);
    klog("block_size %d",1024<<super->block_size);
    klog("blocks per group %d",super->blocks_per_group);
    klog("inodes per group %d",super->inodes_per_group);
    klog("free inodes: %d / %d",super->inodes_unalloc_count,super->inodes_count+super->inodes_unalloc_count);
    klog("free blocks: %d / %d (%d reserved)",super->blocks_unalloc_count,super->blocks_count+super->blocks_unalloc_count,super->blocks_reserved_count);
}

// inode numbers start a 1!
ext2_inode *ext2_get_inode(uint32_t ext2_start_addr,uint32_t inode_num)
{
    uint32_t ptr; //will temporarily hold adress of some structs

    // check signature and get pointer to superblock.
    ext2_superblock *super=ext2_check(ext2_start_addr);

    // get blockgroup descriptor for the block group containing 
    // our inode.
    int block_group=(inode_num-1)/super->inodes_per_group;
    int descriptor_start_block=1024<<super->block_size==1024?2:1;

    ptr=ext2_start_addr+(1024<<super->block_size)*descriptor_start_block;
    ptr+=sizeof(ext2_blockgroup_desc)*block_group; // skip to descriptor for our inode's block
    ext2_blockgroup_desc *desc=ptr;

    // read the inode
    ptr=ext2_start_addr+(1024<<super->block_size)*desc->addr_inode_table;
    ptr+=128*((inode_num-1)%super->inodes_per_group);
    ext2_inode *inode=ptr;

    return inode;
}

static void* ext2_get_blockstart(void* start, uint32_t block_size, uint32_t block_idx)
{
    return (start+block_size*block_idx);
}

static void* ext2_get_indirectstart(void *start, uint32_t block_size, uint32_t indirect1_idx, uint32_t block_idx)
{
    uint32_t *indirect_ptr=ext2_get_blockstart(start,block_size,indirect1_idx);
    void *ptr=ext2_get_blockstart(start,block_size,indirect_ptr[block_idx]); 
    return ptr;
}

static void* ext2_get_indirectstart_double(void *start, uint32_t block_size, uint32_t indirect2_idx, uint32_t block_idx)
{
    //doubly indirect list
    uint32_t *dil=ext2_get_blockstart(start,block_size,indirect2_idx);

    int indirect1_idx=block_idx/(block_size/4);
    int idx=block_idx%(block_size/4);

    return ext2_get_indirectstart(start,block_size,dil[indirect1_idx],idx);
}

//
uint32_t ext2_inode_blockstart(uint32_t ext2_start_addr,uint32_t inode_nr,uint32_t block)
{
    ext2_superblock *super=ext2_check(ext2_start_addr);
    int block_size=1024<<super->block_size;

    ext2_inode *inode=ext2_get_inode(ext2_start_addr,inode_nr);

    uint8_t *ptr=0;

    if(block<12)
    {
	    ptr=ext2_get_blockstart(ext2_start_addr,block_size,inode->direct_pointer[block]);

    }
    else if(block-12<block_size/4)
    {
	    ptr=ext2_get_indirectstart(ext2_start_addr,block_size,inode->indirect1,block-12);
    }
    
    else if(block-12-block_size/4<1024/4*1024/4)
    {
	ptr=ext2_get_indirectstart_double(ext2_start_addr,block_size,inode->indirect2,block-12-block_size/4);
    }

    return ptr;
}

static uint32_t ext2_filename_to_inode_traverse(uint32_t ext2_start_addr, char *path,uint32_t inode_start)
{
    uint32_t len=0;
    // true if final filename
    bool final=false;

    // skip leading slashes
    while(*path=='/')path++;
    char *first=path;

    // find end of dir or file name
    while(path[len]!='/'&&path[len]!=0)len++;

    // no more slashes
    if(path[len]==0)final=true;

    //klog("looking for %s '%s' in inode: %d",final?"file":"dir",first,inode_start);

    uint32_t pos=0;
    while(1)
    {
	fs_dirent dirs;
        uint32_t ret=ext2_read_dir(VMEM_EXT2_RAMIMAGE,inode_start, &dirs,&pos);
	if(!ret)break;

	if(strlen(dirs.name)==len && !strcmp_l(first,dirs.name,len))
	{
	    klog("found inode %d %s%s (in inode %d)",dirs.inode,dirs.name,dirs.type==FS_FILE_TYPE_DIR?"/ ":" ",inode_start);
	    if(final)return dirs.inode;
	    return ext2_filename_to_inode_traverse(ext2_start_addr,&path[len]+1,dirs.inode);
	}
    }

    klog("file not found!");
    return 0;
}

uint32_t ext2_filename_to_inode(uint32_t ext2_start_addr, char *path)
{
    if(!strcmp_l(path,"/",0))return 2; // root is inode 2 by definition
    return ext2_filename_to_inode_traverse(ext2_start_addr,path,2);
}

uint32_t ext2_read_inode(uint32_t ext2_start_addr, int inode_nr, char *buf, uint32_t *pos, uint32_t max_size)
{
    uint32_t count=0;

    ext2_superblock *super=ext2_check(ext2_start_addr);
    ext2_inode      *inode=ext2_get_inode(ext2_start_addr,inode_nr);
    uint32_t        block_size=1024<<super->block_size;

    while((*pos)<inode->size_low) 
    {
	if(count==max_size)return count;

	// get ptr to pos
	uint32_t block=(*pos)/block_size;
        uint32_t ptr = ext2_inode_blockstart(ext2_start_addr,inode_nr,block)+((*pos)%block_size);

	buf[count]=*((char *)ptr);

	*pos+=1;
	count++;
    }

    return count;
}

int ext2_read_dir(uint32_t ext2_start_addr, int inode_nr, fs_dirent *dirs, uint32_t *pos)
{
    ext2_superblock *super=ext2_check(ext2_start_addr);
    ext2_inode      *inode=ext2_get_inode(ext2_start_addr,inode_nr);
    uint32_t        block_size=1024<<super->block_size;

    while(*pos<inode->size_low) 
    {
	// get ptr to pos
	uint32_t block=(*pos)/block_size;
        uint32_t ptr = ext2_inode_blockstart(ext2_start_addr,inode_nr,block)+((*pos)%block_size);

	//dir data 
	ext2_dir *dir=ptr;

	if(dir->inode) //otherwise skip
	{
	    dirs->type=FS_FILE_TYPE_FILE;
	    ext2_inode *inode_current=ext2_get_inode(ext2_start_addr,dir->inode);
	    if(inode_current->permissions&0x4000)dirs->type=FS_FILE_TYPE_DIR;
	    memcpy(dirs->name,ptr+8,dir->name_length_low);
	    if(dir->name_length_low>255)dirs->name[255]=0; 
	    dirs->name[dir->name_length_low]=0; // null temrinate
	    dirs->inode=dir->inode;

	    *pos+=dir->size;
	    return 1;
	}

	*pos+=dir->size;
    }
    return 0;
}

/* mount interface */

fd ext2_mount_file_open(mount *m,char *path)
{
    return fd_from_path(path);
}

int ext2_mount_read_dir(mount *m,char *path, fs_dirent *dirs, uint32_t *pos)
{
    uint32_t inode= ext2_filename_to_inode(VMEM_EXT2_RAMIMAGE,path); 
    if(inode==0)return -1;
    ext2_inode *inode_current=ext2_get_inode(VMEM_EXT2_RAMIMAGE,inode);
    if(!(inode_current->permissions&0x4000))return -1;
    return ext2_read_dir(m->data, inode, dirs, pos);
}

void ext2_mount(char *path)
{
    mount m;
    m.type=MOUNT_TYPE_EXT2;
    memcpy(m.path,path,strlen(path)+1);
    m.mount_file_open=ext2_mount_file_open;
    m.mount_read_dir=ext2_mount_read_dir;
    m.data=VMEM_EXT2_RAMIMAGE;
    mount_add(m);
}