start address of the code segment of the program on x86-64

Hi, 0×08048000 address is the start address of the code segment of a program in on x86-32. What is the start address of the code segment of the program on x86-64 ? Is there a place in the kernel code where I can add a printk on a x86_64 machine to view the code segment start ? How can it be done ? rgs Kevin