55 lines
1.3 KiB
NASM
55 lines
1.3 KiB
NASM
global _start
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section .data
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str: db "Please give me a string: " ; \n = 0xA
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strSize: equ $ - str
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; $ = current assembler address.
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; Since str is all that is above it must be the size
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stdin: equ 0 ; POSIX
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stdout: equ 1 ; POSIX
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; Uninitialized space goes here, pretty much your heap of uninitialized bytes
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; for all kinds of purposes
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section .bss
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strBuffer: resb 64 ; reserve 64 bytes
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strBufferSize: equ 64 ; same as above
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; This is where the code goes. Text. Makes sense, right?
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section .text
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_start:
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; x64 has the syscall function, in contrast to int in x86 and ARM
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; See /usr/include/asm/unistd_64.h for the numbers
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; Clobbered registers
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; rax rdi rsi rdx r10 r8 r9
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; Write to stdout
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mov rax, 1
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mov rdi, stdout ; fd to write to
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mov rsi, str ; pointer
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mov rdx, strSize ; size
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syscall ; all arguments are specified above! (x86 = int 0x80)
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; Read from stdin
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xor rax, rax ; 0
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mov rdi, stdin ; fd to read from
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mov rsi, strBuffer ; where to store it
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mov rdx, strBufferSize ; maximum number of bytes
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syscall
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; syscall return codes are always stored in register A
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; The number of bytes read in was returned through this
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mov rdx, rax
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mov rax, 1
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mov rdi, stdout
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mov rsi, strBuffer
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syscall
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; Exit routine
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mov rax, 60 ; 60 is the exit routine
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xor rdi, rdi ; our return code (0)
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syscall
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