[coreboot] Data in memory changes unexpectedly in initialize_cpus

Patrick Georgi patrick at georgi-clan.de
Wed Feb 10 11:51:36 CET 2010

Am 10.02.2010 11:24, schrieb Bao, Zheng:
> I am debugging the fam10+RS780+SB700. Now I am facing a problem which
> troubles me for quite a long time. It came up since CBFS play its role.
> The data in memory changes unexpectedly. The printk_debug can not help
> to narrow down the point where the writing happens.
> So I set the memory address which changes during booting as a breakpoint
> trigger. Anyone writes data to this address will cause a breakpoint. But
> unfortunately nothing can be captured. So I had to set breakpoint in the
> whole process to narrow down. Now I narrow down to the initialize_cpus
> in src/cpu/x86/lapic/. The functions called in initialize_cpus are
> static which can not find a symbol in the coreboot.map. I need to
> disassemble the binary to find out why. Before that, I need to guess
> what on earth happens.
> It seems to have something to do with the SMP. It seems that other cores
> write data into the memory which is not belong to them. Do you think it
> can happen?
Can you narrow down a bit what kind of data is overwritten there?

The only thing related to SMP that I can think of is stacks and CBFS
loading. For both it might (but should not) happen that multiple cores
try to do the same thing and overwrite each other's data.

Stacks seem fine in AMD code (from a short look), you could try to look
what the APs so once they are started. cbfs might happen early, and we
need to change things there, eg. have the BSP decompress the AP code
once, before starting the APs, instead of the APs, which would require
locking to not stumble over each other.


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