hello world

hello.s

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+global _start
+
+; constants
+SYS_WRITE   equ 1
+SYS_EXIT    equ 60
+STDOUT      equ 1
+
+SECTION .data
+hello           db  "Hello world!", 0x0a
+hello_len       equ $ - hello
+
+SECTION .text
+
+_start:
+    ; syscall(SYS_WRITE, STDOUT, hello, hello_len);
+    mov     rax, SYS_WRITE
+    mov     rdi, STDOUT
+    mov     rsi, hello
+    mov     rdx, hello_len
+    syscall
+    push    rax
+
+    ; syscall(SYS_EXIT, <sys_write return value> - hello_len);
+    mov     rax, SYS_EXIT
+    pop     rdi
+    sub     rdi, hello_len
+    syscall

readme.md

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+# x86_64 assembly
+
+https://userpages.cs.umbc.edu/tsimo1/CMSC313/nasmdoc/html/nasmdoc3.html
+https://x64.syscall.sh/
+
+https://web.stanford.edu/class/cs107/resources/x86-64-reference.pdf
+https://ggbaker.ca/295/x86.html
+https://josemariasola.github.io/reference/assembler/Stanford%20CS107%20Guide%20to%20x86-64.pdf