Luna/kernel/src/main.asm

global _main
extern _start

_main:
    xor rbp, rbp
    call _start

global _userspace
_userspace:
    mov rdi, 4000 ; 4000 ms / 4 seconds
    mov rax, 2 ; sys_sleep
    int 42h
    cmp rax, 0
    jne .fail ; syscall failed
    mov rdi, .message
    mov rsi, 33
    mov rax, 3 ; sys_write
    int 42h
    cmp rax, 33
    jne .fail ; syscall did not write enough bytes
.draw:
    mov rax, 5 ; sys_rand
    int 42h
    mov r9, rax ; color
    mov rdi, 20 ; x
    mov rsi, 20 ; y
    mov r10, 40 ; width
    mov r8, 30 ; height
    mov rax, 4 ; sys_paint
    int 42h
    cmp rax, 0
    jne .fail
    mov rdi, 100
    mov rax, 2 ; sys_sleep
    int 42h
    cmp rax, 0
    jne .fail
    jmp .draw
.fail:
    mov rax, 0 ; sys_exit
    int 42h
    jmp $ ; sys_exit failed, nothing more we can do
.message:
    db "userspace preparing for painting", 0xA