Userspace/libc/ElfInterpreter/ldstart.c

void __attribute__((naked, used, no_stack_protector)) _ld_start()
{
    __asm__("movq $0, %rbp\n"
            "pushq %rbp\n"
            "pushq %rbp\n"
            "movq %rsp, %rbp\n"

            "pushq %rcx\n"
            "pushq %rdx\n"
            "pushq %rsi\n"
            "pushq %rdi\n"

            "call ld_main\n"

            "popq %rdi\n"
            "popq %rsi\n"
            "popq %rdx\n"
            "popq %rcx\n"

            "call ld_load\n"
            "movl %eax, %edi\n"
            "call _exit");
}

void _exit(int Code)
{
    __asm__ __volatile__("syscall"
                         :
                         : "a"(0), "D"(Code)
                         : "rcx", "r11", "memory");
    while (1)
        ;
}