143 lines
2.3 KiB
NASM
143 lines
2.3 KiB
NASM
org 0x7c00
|
|
bits 16
|
|
|
|
start:
|
|
jmp .skip_bpb ; Workaround for some BIOSes that require this stub
|
|
nop
|
|
|
|
; Some BIOSes will do a funny and decide to overwrite bytes of code in
|
|
; the section where a FAT BPB would be, potentially overwriting
|
|
; bootsector code.
|
|
; Avoid that by filling the BPB area with 0s
|
|
times 87 db 0
|
|
|
|
.skip_bpb:
|
|
cli
|
|
cld
|
|
jmp 0x0000:.initialise_cs
|
|
.initialise_cs:
|
|
xor si, si
|
|
mov ds, si
|
|
mov es, si
|
|
mov ss, si
|
|
mov sp, 0x7c00
|
|
sti
|
|
|
|
; Limine isn't made for floppy disks, these are dead anyways.
|
|
; So if the value the BIOS passed is <0x80, just assume it has passed
|
|
; an incorrect value.
|
|
cmp dl, 0x80
|
|
jb err.0
|
|
; Values above 0x8f are dubious so we assume we weren't booted properly
|
|
; for those either
|
|
cmp dl, 0x8f
|
|
ja err.1
|
|
|
|
.continue:
|
|
; Make sure int 13h extensions are supported
|
|
mov ah, 0x41
|
|
mov bx, 0x55aa
|
|
int 0x13
|
|
jc err.2
|
|
cmp bx, 0xaa55
|
|
jne err.3
|
|
|
|
push 0x7000
|
|
pop es
|
|
mov di, stage2_locs
|
|
mov eax, dword [di]
|
|
mov ebp, dword [di+4]
|
|
xor bx, bx
|
|
xor ecx, ecx
|
|
mov cx, word [di-4]
|
|
call read_sectors
|
|
jc err.4
|
|
mov eax, dword [di+8]
|
|
mov ebp, dword [di+12]
|
|
add bx, cx
|
|
mov cx, word [di-2]
|
|
call read_sectors
|
|
jc err.5
|
|
|
|
lgdt [gdt]
|
|
|
|
cli
|
|
mov eax, cr0
|
|
bts ax, 0
|
|
mov cr0, eax
|
|
|
|
jmp 0x08:vector
|
|
|
|
times 0xda-($-$$) db 0
|
|
times 6 db 0
|
|
|
|
; Includes
|
|
|
|
%include 'disk.asm'
|
|
%include '../gdt.asm'
|
|
|
|
err:
|
|
.5:
|
|
inc si
|
|
.4:
|
|
inc si
|
|
.3:
|
|
inc si
|
|
.2:
|
|
inc si
|
|
.1:
|
|
inc si
|
|
.0:
|
|
add si, '0' | (0x4f << 8)
|
|
|
|
push 0xb800
|
|
pop es
|
|
mov word [es:0], si
|
|
|
|
sti
|
|
.h: hlt
|
|
jmp .h
|
|
|
|
bits 32
|
|
vector:
|
|
mov eax, 0x10
|
|
mov ds, ax
|
|
mov es, ax
|
|
mov fs, ax
|
|
mov gs, ax
|
|
mov ss, ax
|
|
|
|
and edx, 0xff
|
|
|
|
push 0
|
|
|
|
push edx
|
|
|
|
push stage2.size
|
|
push (stage2 - decompressor) + 0x70000
|
|
|
|
call 0x70000
|
|
|
|
times 0x1a4-($-$$) db 0
|
|
stage2_size_a: dw 0
|
|
stage2_size_b: dw 0
|
|
stage2_locs:
|
|
stage2_loc_a: dq 0
|
|
stage2_loc_b: dq 0
|
|
|
|
times 0x1b8-($-$$) db 0
|
|
times 510-($-$$) db 0
|
|
dw 0xaa55
|
|
|
|
; ********************* Stage 2 *********************
|
|
|
|
decompressor:
|
|
%strcat DECOMPRESSOR_PATH BUILDDIR, '/decompressor/decompressor.bin'
|
|
incbin DECOMPRESSOR_PATH
|
|
|
|
align 16
|
|
stage2:
|
|
%strcat STAGE2_PATH BUILDDIR, '/stage23-bios/stage2.bin.gz'
|
|
incbin STAGE2_PATH
|
|
.size: equ $ - stage2
|