StupidOS/boot/loader/loader.asm

173 lines
2.9 KiB
NASM

;; File: loader.asm
format binary
include '../common/const.inc'
include '../common/macro.inc'
include 'multiboot.inc'
org LOADER_BASE
use32
jmp _start
align 4
multiboot_header:
mb_header MultibootHeader multiboot_header
_start:
cmp eax, MULTIBOOT_MAGIC
je multiboot
use16
align 2
; =========================================================================
; real mode code
; =========================================================================
push cs
pop ds
mov [uDrive], dl
mov si, szMsgStage2
call bios_log
; enable A20 line
call a20_enable
jc .error_a20
xchg bx, bx
; check drive type
; dl <= 0x7F == floppy
; dl >= 0x80 == hard drive
; dl == 0xE0 ~= CD/DVD
; dl <= 0xFF == hard drive
mov dl, [uDrive]
cmp dl, 0x7F
; skip disk extension check
jle @f
; check disk extensions
mov ah, 0x41
mov bx, 0x55AA
int 0x13
jc @f
mov [bDriveLBA], TRUE
@@:
; detect filesystem (FAT12/16 or StpdFS)
; load kernel from filesystem
; +---------+--------+---------+
; | bootsec | sect 1 | stpd sb |
; +---------+--------+---------+
; 0 512 1024
;
; for now fat12 is asumed
call fat_load_root
mov si, szKernelFile
call fat_search_root
jc .error_not_found
; fetch memory map from bios
call memory_get_map
jc .error_memory
; video information
call video_setup
; load GDT and enter Protected-Mode
lgdt [gdt_ptr]
; enable protected mode
mov eax, cr0
or al, 1
mov cr0, eax
; reload ds, es, fs, gs, ss
mov ax, 0x10
mov ds, ax
mov es, ax
mov fs, ax
mov gs, ax
mov ss, ax
jmp 0x8:common32
.error_not_found:
mov si, szMsgErrorNotFound
jmp .error
.error_memory:
mov si, szMsgErrorMemory
jmp .error
.error_a20:
mov si, szMsgErrorA20
.error:
call bios_log
@@:
hlt
jmp @b
include 'a20.inc'
include '../common/bios.inc'
include '../common/fat12.inc'
include 'disk.inc'
include 'logger.inc'
include 'memory.inc'
include 'video.inc'
include 'gdt.inc'
uDrive rb 1
bDriveLBA db FALSE
szMsgStage2 db "StupidOS Loader", 0
szKernelFile db "VMSTUPIDSYS", 0
szMsgErrorA20 db "ERROR: can't enable a20 line", 0
szMsgErrorMemory db "ERROR: can't detect available memory", 0
szMsgErrorSector db "ERROR: reading sector", CR, LF, 0
szMsgErrorNotFound db "ERROR: kernel not found", 0
use32
; =========================================================================
; protected mode code
; =========================================================================
multiboot:
; https://www.gnu.org/software/grub/manual/multiboot/multiboot.html#Machine-state
; get screen information
; get memory map
; get kernel from module
common32:
mov [0xB8000], dword 0x07690748
; paging
; identity map first 1MB
; map kernel to 0xC000000
; -----------------------
push STPDBOOT_MAGIC
mov eax, 0xC0000000
jmp eax
hang:
hlt
jmp $
_edata:
boot_structure:
align 4096
boot_page_directory:
rb 4096
boot_768_page_table:
rb 4096
_end: