format ELF64 executable 3
entry start

__NR_open equ 2
__NR_close equ 3
__NR_sendfile equ 40
__NR_exit equ 60
STDIN_FILENO equ 0
STDOUT_FILENO equ 1
CHUNKSIZE equ 1048576

segment readable writeable
    fd dq STDIN_FILENO

segment readable executable

start:
    xor r8, r8
    mov rbx, 1
    cmp [rsp], rbx
    je sendfile
open:
    xor rsi, rsi
    mov rdi, [rsp+rbx*8+8]
    mov rax, __NR_open
    syscall
    mov [fd], rax
sendfile:
    mov r10, CHUNKSIZE
    mov rdx, r8
    mov rsi, [fd]
    mov rdi, STDOUT_FILENO
    mov rax, __NR_sendfile
    syscall
    test rax, rax
    jnz sendfile
close:
    mov rdi, [fd]
    mov rax, __NR_close
    syscall
    inc rbx
    cmp rbx, [rsp]
    jb open
exit:
    xor rdi, rdi
    mov rax, __NR_exit
    syscall