Re: [discuss] [OOPS] powernow on smp dual core amd64

[Andi Kleen <ak@suse.de>]

> asmlinkage void smp_call_function_interrupt(void)
> {
>        void (*func) (void *info) = call_data->func;
>        void *info = call_data->info;
>        int wait = call_data->wait;
> 
>        ack_APIC_irq();
>        /*
>         * Notify initiating CPU that I've grabbed the data and am
>         * about to execute the function
>         */
>        mb();
>        atomic_inc(&call_data->started);
>        /*
>         * At this point the info structure may be out of scope unless 
> wait==1
>         */
>        irq_enter();
>        (*func)(info);  <--- passed bogus data
> 
> Looks like you jumped through a bogus function pointer.  I'm guessing it 
> has something to do with an unitialized IRQ vector for the CPU speed on 
> one of the cores (simply because it seems somewhat plausible):

What should a "IRQ vector for the CPU speed" be?

> 
> extern u8 irq_vector[NR_IRQ_VECTORS];
> #define IO_APIC_VECTOR(irq)     (irq_vector[irq])
> #define AUTO_ASSIGN             -1
> 
> So irq_vector[AUTO_ASSIGN] = 0xff which could have somehow made it into 
> your function pointer.


Yes, but it is hard to see how that should happen short of massive
memory corruption. call_data is a global variable even.

However after a MCE things can be a bit instable. Maybe it would
be best to use a streamlined panic in this case that doesn't touch
the other CPUs.

-Andi
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