Skip to content

Instantly share code, notes, and snippets.

@rexim

rexim/sigaction.asm

Created February 11, 2022 19:30
Show Gist options
  • Save rexim/c172f43ffdc73a14e8b0f83f4cbe0f5a to your computer and use it in GitHub Desktop.
Save rexim/c172f43ffdc73a14e8b0f83f4cbe0f5a to your computer and use it in GitHub Desktop.
Download ZIP

Revisions

  1. rexim created this gist Feb 11, 2022.
    94 changes: 94 additions & 0 deletions sigaction.asm
    View file
    Original file line number Diff line number Diff line change
    @@ -0,0 +1,94 @@
    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