os/libc/stdio.c

void print(char* s) 
{
    asm("mov %0, %%eax" :: "r" (s));
    asm("mov $0, %edx");
    asm("int $0x80");
}

void input(char* buf)
{
    asm("mov %0, %%eax" :: "r" (buf));
    asm("mov $1, %edx");
    asm("int $0x80");
}