[coreboot] Questions about coreboot on X86

[Hamo]

Dear lists,
I have been studying the boot process of coreboot more deeply, and
following questions came out:
1. Which code clean the bss and set sp pointer to the stack? Since
those addresses are defined in coreboot_ram.ld, Should it be in
ramstage? If so, where are they? I don't find them. If not, where are
they and how do they know the addresses of bss and stack?
2. What's the propose of romstage? Some init in romstage has been done
in bootblock, and why those init are done twice?

Thanks,
Hamo