mirror of https://github.com/FDOS/kernel.git
56 lines
950 B
NASM
56 lines
950 B
NASM
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%if 0
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UPX preparation stub for DOS/EXE format compressed FreeDOS kernel
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Public Domain by C. Masloch, 2022
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%endif
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cpu 8086
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org 0
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bootloadunit: ; (byte of short jump re-used)
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start:
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jmp strict short entry
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times (32 - 4) - ($ - $$) db 0
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; area for CONFIG block
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bootloadstack: ; (dword re-used for original ss:sp)
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entry:
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; common setup (copied from kernel.asm)
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push cs
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pop ds
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xor di, di
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mov byte [di + bootloadunit - $$], bl
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push bp
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mov word [di + bootloadstack - $$], sp
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mov word [di + bootloadstack + 2 - $$], ss
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; the UPX DOS/EXE depacker needs a certain ss:sp
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cli
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mov ax, 0
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patchstacksegment: equ $ - 2
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mov ss, ax
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mov sp, 0
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patchstackpointer: equ $ - 2
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sti
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mov ax, -10h
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patchpspsegment: equ $ - 2
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mov ds, ax
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mov es, ax
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jmp 0:0
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patchcsip: equ $ - 4
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end:
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times 0C0h - ($ - $$) nop
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entry_common:
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times 100h - ($ - $$) db 0
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dw patchstackpointer
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dw patchstacksegment
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dw patchpspsegment
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dw patchcsip
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dw end
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