On Mon, Jul 14, 2008 at 12:05:18AM +0800, Zhang Rui wrote:
2008/7/13, Kevin O'Connor kevin@koconnor.net:
In LegacyBIOS(SeaBIOS), I inserted some code in post.c
[...]
"movl $" __stringify(BUILD_STACK_ADDR) ", %esp\n"[...]
I think the return address in the stack is wrong. I am trying to figure it out.
You moved the stack (by assigning a new value to %esp). So, the return address is not on the stack - it's on the previous stack.
But I tried without "movl $" __stringify(BUILD_STACK_ADDR) ", %esp\n", post_coreboot in LegacyBIOS(SeaBIOS) can not run correctly. I think I should manually set the return address?
Right - seabios needs to be using its stack in order to call 16bit functions. You probably need to save and restore the stack. Completely untested, but something like:
movl %esp, %esi movl $BUILD_STACK_ADDR, %esp ljmp 0x10, $1f
1: calll post_coreboot
movl %esi, %esp retl
However, note that the above wont save/restore the idt/gdt. And again, I'm not sure if coreboot puts its stack/idt/gdt somewhere where seabios may overwrite it.
-Kevin