Re: [Fastboot] Re: [PATCH 1/4] stack overflow safe kdump (i386) -safe_smp_processor_id

[Eric W. Biederman]

Andi Kleen <ak@xxxxxxx> writes:

> Fernando Luis Vazquez Cao <fernando@xxxxxxxxxxxxxxxxx> writes:
>> 
>> To circumvent this problem I suggest implementing
>> "safe_smp_processor_id()" (it already exists on x86_64) for i386 and
>> IA64 and use it as a replacement to smp_processor_id in the reboot path
>> to the dump capture kernel. This is a possible implementation for i386.
>
> It's not fully safe, because a SMP kernel might run on a 32bit
> system without APIC. Then hard_smp_processor_id() would fault. 
> (this cannot happen on x86-64)
>
> You probably need to check one of the globals set by apic.c
> when its disabled.

Right.  An SMP kernel on a uniprocessor, without apics.

To my knowledge all SMP systems that linux supports have
apics.

Eric

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