rulimine/stage1/cd/bootsect.asm

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1.7 KiB
NASM
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org 0x7c00
bits 16
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jmp skip_bpb
nop
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; El Torito Boot Information Table
; ↓ Set by mkisofs
times 8-($-$$) db 0
boot_info:
bi_PVD dd 0
bi_boot_LBA dd 0
bi_boot_len dd 0
bi_checksum dd 0
bi_reserved times 40 db 0
times 90-($-$$) db 0
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skip_bpb:
cli
cld
jmp 0x0000:.initialise_cs
.initialise_cs:
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xor si, si
mov ds, si
mov es, si
mov ss, si
mov sp, 0x7c00
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sti
; int 13h?
mov ah, 0x41
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mov bx, 0x55aa
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int 0x13
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jc err.0
cmp bx, 0xaa55
jne err.1
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; --- Load the decompressor ---
mov eax, dword [bi_boot_LBA]
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add eax, 1
mov ecx, stage2.fullsize / 2048
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; DECOMPRESSOR_LOCATION = 0x70000 = 0x7000:0x0000
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push 0x7000
pop es
xor bx, bx
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call read_2k_sectors
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jc err.2
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; Enable GDT
lgdt [gdt]
cli
mov eax, cr0
or al, 1
mov cr0, eax
jmp 0x08:pmode
err:
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.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
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%include 'read_2k_sectors.asm'
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%include '../gdt.asm'
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bits 32
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pmode:
mov eax, 0x10
mov ds, ax
mov es, ax
mov fs, ax
mov gs, ax
mov ss, ax
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; Time to handle control over to the decompressor
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push 2
and edx, 0xff
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push edx ; Boot drive
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push stage2.size
push (stage2 - decompressor) + 0x70000
call 0x70000
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; Align stage2 to 2K ON DISK
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times 2048-($-$$) db 0
decompressor:
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%strcat DECOMPRESSOR_PATH BUILDDIR, '/decompressor-build/decompressor.bin'
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incbin DECOMPRESSOR_PATH
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align 16
stage2:
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%strcat STAGE2_PATH BUILDDIR, '/common-bios/stage2.bin.gz'
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incbin STAGE2_PATH
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.size: equ $ - stage2
times ((($-$$)+2047) & ~2047)-($-$$) db 0
.fullsize: equ $ - decompressor