2019-03-24 19:24:25 +01:00
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; assumptions about the starting envionment
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cpu 8086
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org 0x0000
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_startup:
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xor ax, ax ; trash ax
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mov ax, cs
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cmp ax, 0x0000 ; MBR or NBP, CS=0000 IP=7C00
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je .mbr
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cmp ax, 0x07C0 ; MBR on weird BIOS, CS=07C0 IP=0000
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je .mbr
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.dos:
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; ROP because call only works on immediate or memory
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mov ax, cs
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push ax ; return CS
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mov ax, .dosret
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add ax, 0x0100
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push ax ; return IP
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mov ax, cs
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add ax, 0x0010
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push ax ; main CS
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mov ax, main
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push ax ; main IP
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retf
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.dosret:
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int 0x20
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jmp .halt
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.mbr:
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push si ; index of partition table entry
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push ds ; segment for ^
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push dx ; dl might contain drive number
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push bx ; possible offset for pxeenv+ struct
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push es ; segment for ^
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mov ax, 0x0050
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mov es, ax
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mov di, 0x0000
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xor ax, ax
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mov ds, ax
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mov si, 0x7C00
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mov cx, _reloc_end
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rep movsb
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call 0x0050:main
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.halt:
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hlt
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jmp .halt
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2019-03-23 21:23:17 +01:00
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main:
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mov ax, cs
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mov ds, ax
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call heap_init
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2019-03-24 18:59:45 +01:00
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call ivt_backup
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call debug_init
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2019-03-23 22:26:46 +01:00
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2019-03-24 18:59:45 +01:00
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int 0x2E
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2019-03-23 21:23:17 +01:00
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2019-03-24 18:59:45 +01:00
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retf
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2019-03-23 21:23:17 +01:00
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2019-03-24 19:24:25 +01:00
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%include "heap.asm"
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%include "intr.asm"
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%include "debug.asm"
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%include "kprintf.asm"
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_reloc_end:
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2019-03-23 21:23:17 +01:00
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align 16
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heap:
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