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65 lines
1.5 KiB
ArmAsm
65 lines
1.5 KiB
ArmAsm
; See the end of this file for copyright and license terms.
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;
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; We use a custom ABI because BIOS interrupts use ax for their parameter:
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;
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; register | usage
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; ---------|--------------------
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; ax | BIOS parameter
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; bx | arg1, return value
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; cx | arg2
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; dx | arg3
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;
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; Registers ax-dx are saved by the caller, all others by the callee.
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;
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; To save space, strings are terminated by setting bit 7 of their last
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; character to 1 (because ascii only uses bits 0-6) rather than appending a
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; full NUL terminator byte. This technique is stolen from FreeBSD.
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;
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[bits 16]
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[org 0x7c00]
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_start:
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mov bp, 0x9000
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mov sp, bp
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mov bx, HELLO
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call print
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; TODO: switch to protected mode and call kernel here
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jmp $
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; args:
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; - bx: pointer to string
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print:
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mov ah, 0x0e
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_print_loop:
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mov al, [bx]
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mov cl, al
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and al, 0x7f
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int 0x10
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inc bx
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and cl, 0x80
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je _print_loop
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ret
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HELLO: db "hi i'm gay uwu", 0x0d, 0x8a ; '\r', '\n'|0x80
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; padding to 512 bytes (-2 for magic)
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times 510 - ($-$$) db 0
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; mbr magic
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dw 0xaa55
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; This file is part of GayBSD.
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; Copyright (c) 2021 fef <owo@fef.moe>.
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;
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; GayBSD is nonviolent software: you may only use, redistribute, and/or
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; modify it under the terms of the Cooperative Nonviolent Public License
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; (CNPL) as found in the LICENSE file in the source code root directory
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; or at <https://git.pixie.town/thufie/cnpl-builder>; either version 7
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; of the license, or (at your option) any later version.
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;
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; GayBSD comes with ABSOLUTELY NO WARRANTY, to the extent
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; permitted by applicable law. See the CNPL for details.
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