global  _start

; NOTE: assumes program loader has put argc, argv, envc, envp on stack
section .text
_start:
    xor rbp,rbp    ; base pointer undefined: set to 0
    mov r9,rdx     ; 6th arg: function to register with atexit()
    pop rsi        ; 2nd arg: argc
    mov rdx,rsp    ; 3rd arg: argv
    and rsp,$-16   ; align stack pointer to 16 bytes
    mov $_fini,r8  ; 5th arg: fini
    mov $_init,rcx ; 4th arg: init
    mov $main,rdi  ; 1st arg: main

    call rt·boot   ; int boot(
                   ;       int(*main)(int,char*[],char*[]),
                   ;       int argc,
                   ;       char *argv[],
                   ;       init, fini, atexit);

.loop: jmp .loop  ; should never reach...