ROSE/boot.nasm

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3.8 KiB
NASM
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secreadcnt equ 0x38
kernelreads equ 0x10000/(512*secreadcnt) ; 64K / Sector Size FIXME This underestimates when kernel size is not divisible by bytes per read
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[ORG 0x7c00]
[BITS 16]
xor ax, ax
mov ds, ax
mov es, ax
mov ax, 0x8000
mov ss, ax
mov sp, 0xFF00
mov ah, 0x41 ; int 13 extensions check
mov bx, 0x55AA
int 0x13
jc no_exten
mov cx, kernelreads
read_loop:
xor ax, ax
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mov ah, 0x42
mov si, addr_packet
int 0x13
jc err
add word [addr_packet_transfer_buff_seg], (secreadcnt*512)/16
add word [addr_packet_start_block], secreadcnt
loop read_loop
entry:
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;mov ax,0x2403 ; A20 BIOS Support
;int 0x15
;jb .no_a20
;cmp ah,0
;jnz .no_a20
;mov ax,0x2401 ; A20 BIOS Activate
;int 0x15
;.no_a20:
cli ; no interrupts
xor ax,ax
mov ds, ax
lgdt [gdt_desc] ; load gdt register
mov eax, cr0 ; set pmode bit
or al, 1
mov cr0, eax
jmp 08h:Pmode
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no_exten:
; read with CHS
; FIXME This only reads up to sector count
mov ah,8
int 0x13 ; geometry
and cx, 0x3f
push cx
push 0x0080 ; DH=head,DL=disk
push 0x2000 ; buffer seg
push 2 ; sector
.loop:
mov ax, [esp]
push 0xb800
pop es
xor di,di
call hexprint
mov ax, [esp+2]
mov es, ax
mov ax, 0x0201
mov cx, [esp]
xor bx,bx
mov dx, [esp+4]
int 0x13
jc err
add word [esp+2], 0x20
mov cx, [esp]
inc cl
mov [esp], cx
cmp cl, [esp+6]
jg entry
jmp .loop
err:
mov bx, ax
mov si, string
mov cx, string_end - string
print:
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push 0xb800
pop es
xor di, di
mov ah, 0x7
err_print:
lodsb
stosw
loop err_print
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;add di, 2
;mov ax, bx
;call hexprint
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hlt_loop:
hlt
jmp hlt_loop
hexprint:
xor cx, cx
mov bl, al
shr al, 4
jmp .donibble
.nibble2:
mov al, bl
inc cx
.donibble:
and al, 0x0F
cmp al, 0x0A
jl .noadjust
add al, 'A' - '0' - 10
.noadjust:
add al, '0'
mov ah, 0x7
stosw
test cx, cx
jz .nibble2
ret
[BITS 32]
Pmode:
mov eax, 0x10
mov ds, ax
mov es, ax
mov fs, ax
mov gs, ax
mov ss, ax
; check A20
.a20:
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mov edi, 0x107C00
mov esi, 0x007C00
mov [esi], esi
mov [edi], edi
cmpsd
jne .kernel
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call enable_A20
;in al, 0x92 ; fast A20
;test al, 2
;jnz .fa20_end
;or al, 2
;and al, 0xFE
;out 0x92, al
;.fa20_end:
jmp .a20
.kernel:
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;mov dword [0xb8000], 0x07000700 | 'P' | 'M' << 16
;mov dword [0xb8004], 0x07000700 | 'O' | 'D' << 16
;mov dword [0xb8008], 0x07000700 | 'E' | ' ' << 16
mov esi, 0x20000
mov edi, 0x100000
mov ecx, 0x10000
rep movsb
jmp 08h:0x100000
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enable_A20:
cli
call a20wait
mov al,0xAD
out 0x64,al
call a20wait
mov al,0xD0
out 0x64,al
call a20wait2
in al,0x60
push eax
call a20wait
mov al,0xD1
out 0x64,al
call a20wait
pop eax
or al,2
out 0x60,al
call a20wait
mov al,0xAE
out 0x64,al
call a20wait
ret
a20wait:
in al,0x64
test al,2
jnz a20wait
ret
a20wait2:
in al,0x64
test al,1
jz a20wait2
ret
gdt_desc:
dw gdt_end - gdt
dd gdt
gdt:
gdt_null: dq 0
gdt_code: dw 0xFFFF, 0 ; bits 0-15 limit (4GB), bits 0-15 base address
db 0 ; bits 16-23 base address
db 10011010b ; access byte
db 11001111b ; bits 16-19 limit (4GB), 4 bits flags
db 0 ; bits 24-31 base address
gdt_data: dw 0xFFFF, 0 ; bits 0-15 limit (4GB), bits 0-15 base address
db 0 ; bits 16-23 base address
db 10010010b ; access byte
db 11001111b ; bits 16-19 limit (4GB), 4 bits flags
db 0 ; bits 24-31 base address
gdt_end:
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string: db 'DISK ERROR'
string_end:
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;no_exten_str: db 'NO INT13 EXTEN'
;no_exten_str_end:
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addr_packet:
db 0x10, 0x00 ; size, reserved
dw secreadcnt ; blocks
addr_packet_transfer_buff_off: dw 0x0000 ; transfer buffer offset
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addr_packet_transfer_buff_seg: dw 0x2000 ; transfer buffer segment
addr_packet_start_block: dq 1 ; start block