sigaction.asm

BITS 64

%define SYS_exit 60
%define SYS_read 0
%define SYS_write 1
%define SYS_rt_sigaction 13
%define SYS_rt_sigreturn 15
%define STDIN 0
%define STDOUT 1
%define SIGINT 2

%define sigaction_size 32
%define sigaction_handler_offset 0
%define sigaction_restorer_offset 16
%define sigaction_flags_offset 8
%define SA_RESTORER  0x04000000

segment .text
handler:
    mov rax, SYS_write
    mov rdi, STDOUT
    mov rsi, handler_msg        ;Ctrl+C
    mov rdx, handler_msg_sz
    syscall
    ret

restorer:
    mov rax, SYS_write
    mov rdi, STDOUT
    mov rsi, restorer_msg       ;I'm a restorer!
    mov rdx, restorer_msg_sz
    syscall

    mov rax, SYS_rt_sigreturn
    syscall

global _start
_start:
    mov QWORD [sa+sigaction_handler_offset], handler
    mov QWORD [sa+sigaction_flags_offset], SA_RESTORER
    ; mov QWORD [sa+sigaction_restorer_offset], restorer

    mov rax, SYS_rt_sigaction
    mov rdi, SIGINT
    mov rsi, sa
    xor rdx, rdx
    mov r10, 8
    syscall

    cmp rax, 0
    jl sigaction_failed

    mov rax, SYS_read
    mov rdi, STDIN
    mov rsi, buf
    mov rdx, buf_sz
    syscall

    mov rax, SYS_write
    mov rdi, STDOUT
    mov rsi, ok
    mov rdx, ok_sz
    syscall

    mov rax, SYS_exit
    mov rdi, 0
    syscall

sigaction_failed:
    mov rax, SYS_write
    mov rdi, STDOUT
    mov rsi, sigaction_failed_msg
    mov rdx, sigaction_failed_msg_sz
    syscall

    mov rax, SYS_exit
    mov rdi, 1
    syscall
    ret

segment .data
ok: db "OK!", 10
ok_sz: equ $-ok
handler_msg: db "Ctrl+C", 10
handler_msg_sz: equ $-handler_msg
restorer_msg: db "I'm a restorer!", 10
restorer_msg_sz: equ $-restorer_msg
sigaction_failed_msg: db "ERROR: Failed to setup sigaction for whatever reason", 10
sigaction_failed_msg_sz: equ $-sigaction_failed_msg

segment .bss
sa: resb sigaction_size
buf_sz: equ 256
buf: resb buf_sz