diff options
Diffstat (limited to 'src/entry.asm')
| -rw-r--r-- | src/entry.asm | 90 |
1 files changed, 16 insertions, 74 deletions
diff --git a/src/entry.asm b/src/entry.asm index 596a042..c13cf8e 100644 --- a/src/entry.asm +++ b/src/entry.asm @@ -24,18 +24,15 @@ %define EXT2_SIG_OFFSET 0x38 ; Signature offset in superblock %define EXT2_TABLE_OFFSET 0x08 ; Inode table offset after superblock %define EXT2_INODE_TABLE_LOC 0x1000 ; New inode table location in memory -%define EXT2_ROOT_INODE 0x02 ; Root directory inode +%define EXT2_KERNEL_INODE 0x05 ; Kernel inode %define EXT2_INODE_SIZE 0x80 ; Single inode size %define EXT2_GET_ADDRESS(inode) (EXT2_INODE_TABLE_LOC + (inode - 1) * EXT2_INODE_SIZE) -%define EXT2_TYPE_OFFSET 0x00 ; Inode offset of filetype and rights %define EXT2_COUNT_OFFSET 0x1c ; Inode offset of number of data blocks %define EXT2_POINTER_OFFSET 0x28 ; Inode offset of first data pointer -%define EXT2_INODE_OFFSET 0x00 ; Dirent offset of inode number -%define EXT2_ENTRY_LENGTH_OFFSET 0x04 ; Dirent offset of entry length -%define EXT2_FILENAME_OFFSET 0x08 ; Dirent offset of file name %define EXT2_SIG 0xef53 ; Signature -%define EXT2_DIR 0x4000 ; Directory indicator -%define EXT2_REG 0x8000 ; Regular file indicator + +%define STACK_POINTER 0x00900000 ; The initial stack pointer in kernel mode +%define KERNEL_POSITION 0x00050000 ; Loaded kernel position in protected mode (* 0x10) %define A20_GATE 0x92 ; Fast A20 gate %define A20_ENABLED 0b10 ; Bit 1 defines whether A20 is enabled @@ -119,14 +116,9 @@ lba_error_msg db "LBA error!", NEWLINE, RETURN, NULL stage_two_msg db "Stage2 loaded", NEWLINE, RETURN, NULL disk_success_msg db "Disk is valid", NEWLINE, RETURN, NULL inode_table_msg db "Found inode table", NEWLINE, RETURN, NULL -kernel_found_msg db "Found kernel file", NEWLINE, RETURN, NULL protected_msg db "Jumping to protected mode", NEWLINE, RETURN, NULL drive db 0 -; Filenames -kernel_file_name db "melvix.bin", NULL -kernel_file_name_len equ $ - kernel_file_name - ; Data packet: db 0x10 ; Packet size @@ -144,9 +136,9 @@ lba: times 510 - ($ - $$) db 0 dw 0xAA55 -; This is the second stage. It tries to load '/melvix.bin' into memory. -; To do this, it first checks the integrity of the ext2 fs. Then it has to loop -; through every file in the root until the 'melvix.bin' file is found. +; This is the second stage. It tries to load the kernel (inode 5) into memory. +; To do this, it first checks the integrity of the ext2 fs. Then it has to find +; the address of the fifth inode and load its contents into memory. ; After this is finished, the stage can jump into the protected mode, enable the ; A20 line and finally jump to the kernel! ez stage_two: @@ -172,55 +164,11 @@ stage_two: mov si, inode_table_msg call print - ; Load root dir - mov bx, EXT2_GET_ADDRESS(EXT2_ROOT_INODE) ; First block - mov ax, [bx + EXT2_TYPE_OFFSET] ; Get filetype - and ax, EXT2_DIR ; AND with directory - cmp ax, EXT2_DIR ; Check if it's a directory - jne disk_error ; Not a directory! - ;mov cx, [bx + EXT2_COUNT_OFFSET] ; Number of sectors for inode - TODO later! - mov ax, [bx + EXT2_POINTER_OFFSET] ; Address of first block pointer - shl ax, 1 ; Multiply ax by 2 - mov [lba], ax - mov bx, 0x5000 - mov [dest], bx - call disk_read - - ; Find kernel - ; TODO: Fix endless loop when not found - .kernel_find_loop: - lea si, [bx + EXT2_FILENAME_OFFSET] ; First comparison string - mov di, kernel_file_name ; Second comparison string - mov cx, kernel_file_name_len ; String length - rep cmpsb ; Compare strings - je .found_kernel ; Found correct dirent! - add bx, EXT2_ENTRY_LENGTH_OFFSET ; Add dirent struct size - jmp .kernel_find_loop ; Jump to next dirent! - - .found_kernel: - mov si, kernel_found_msg - call print ; Show happy message! - ; Load kernel - mov ax, [bx + EXT2_INODE_OFFSET] ; Get inode number - dec ax ; Decrement inode: (inode - 1) - mov cx, EXT2_INODE_SIZE ; Prepare for mul - mul cx ; Multiply inode number (* EXT2_INODE_SIZE) - mov bx, ax ; Move for effective address calculations - mov bx, [bx + EXT2_INODE_TABLE_LOC] ; bx is at the start of the inode - mov ax, [bx + EXT2_TYPE_OFFSET] ; Get filetype - and ax, EXT2_REG ; AND with regular file - cmp ax, EXT2_REG ; Check if it's a regular file - jne disk_error ; Not a regular file! - ; Read first block - mov ax, [bx + EXT2_POINTER_OFFSET] ; Address of first block pointer - shl ax, 1 ; Multiply by 2 - mov [lba], ax - mov bx, 0x5000 - mov [dest], bx - call disk_read ; TODO: TEST! - - mov bx, 0x5000 + mov bx, EXT2_GET_ADDRESS(EXT2_KERNEL_INODE) ; First block + mov cx, [bx + EXT2_COUNT_OFFSET] ; Number of sectors for inode + lea di, [bx + EXT2_POINTER_OFFSET] ; Address of first block pointer + mov bx, 0x5000 ; Load to this address mov [dest + 2], bx mov bx, 0 ; Inode location = 0xF0000 mov [dest], bx @@ -239,15 +187,12 @@ kernel_load: call disk_read - add bx, 1024 ; 1kb increase + add bx, 0x400 ; 1kb increase add di, 0x4 ; Move to next block pointer - sub cx, 2 ; Read 2 blocks + sub cx, 0x2 ; Read 2 blocks jnz kernel_load ret - nop - hlt - protected_mode_enter: cli ; Turn off interrupts mov si, protected_msg @@ -279,10 +224,8 @@ protected_mode_enter: jmp 08h:protected_mode ; JUMP! -bits 32 ; Woah! +bits 32 ; Woah, so big! protected_mode: - xor eax, eax - mov ax, 10h ; Set data segement indentifier mov ds, ax mov es, ax @@ -290,11 +233,10 @@ protected_mode: mov gs, ax mov ss, ax ; Stack segment - mov esp, 0x00900000 ; Move stack pointer + mov esp, STACK_POINTER ; Move stack pointer - mov edx, 0x00050000 + mov edx, KERNEL_POSITION lea eax, [edx] - jmp $ call eax ; GDT |