From 89d0a20d56f48ab967fd171aefefa729364c7484 Mon Sep 17 00:00:00 2001 From: Johannes Stoelp Date: Thu, 20 Mar 2025 19:46:21 +0100 Subject: x86: asm example use preprocessor + fix str length --- src/arch/x86_64.md | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) diff --git a/src/arch/x86_64.md b/src/arch/x86_64.md index 35fd9aa..38f40e1 100644 --- a/src/arch/x86_64.md +++ b/src/arch/x86_64.md @@ -331,34 +331,35 @@ Small assembler skeleton, ready to use with following properties: - gnu assembler [`gas`][gas_doc] - intel syntax ```x86asm -# file: greet.s +// file: greet.S +#include .intel_syntax noprefix .section .text, "ax", @progbits .global _start _start: - mov rdi, 1 # fd + mov rdi, 1 # fd (stdout) lea rsi, [rip + greeting] # buf mov rdx, [rip + greeting_len] # count - mov rax, 1 # write(2) syscall nr + mov rax, __NR_write # write(2) syscall nr syscall - mov rdi, 0 # exit code + mov rdi, __NR_exit # exit code mov rax, 60 # exit(2) syscall nr syscall .section .rdonly, "a", @progbits greeting: - .asciz "Hi ASM-World!\n" + .ascii "Hi ASM-World!\n" greeting_len: .int .-greeting ``` -> Syscall numbers are defined in `/usr/include/asm/unistd.h`. +> Files with `.S` suffix are pre-processed, while files with `.s` suffix are not. To compile and run: ```bash -> gcc -o greet greet.s -nostartfiles -nostdlib && ./greet +> gcc -o greet greet.S -nostartfiles -nostdlib && ./greet Hi ASM-World! ``` -- cgit v1.2.3