44 lines
884 B
ArmAsm
44 lines
884 B
ArmAsm
; This is the minimal startup + I/O functionality needed to run
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; RETRO on an OpenBSD x86-64 system.
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; =============================================================
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bits 64
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section .text
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global putchar
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global getchar
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global _start
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extern main
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align 8
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_start:
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call main
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jmp $
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align 8
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putchar:
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mov rax, rdi
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mov [buf], eax
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mov rax, 4 ; sys_write
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mov rdi, 1 ; stdout
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mov rsi, buf ; address
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mov rdx, 1 ; 1 byte
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syscall
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ret
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align 8
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getchar:
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mov rax, 3 ; sys_read
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mov rdi, 0 ; stdin
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mov rsi, buf ; address
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mov rdx, 1 ; 1 byte
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syscall
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mov rax, 0
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mov eax, [buf]
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ret
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section .data
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buf:
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dd 0
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dd 0
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dd 0
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dd 0
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