Re: [PATCH 1/2] powerpc: Move the single step enable code to a genericpath

[Suzuki K. Poulose]

On 11/26/2012 11:40 PM, Sebastian Andrzej Siewior wrote:
> On 11/26/2012 12:05 PM, Suzuki K. Poulose wrote:
> > diff --git a/arch/powerpc/include/asm/probes.h
> > b/arch/powerpc/include/asm/probes.h
> > index 5f1e15b..836e9b9 100644
> > --- a/arch/powerpc/include/asm/probes.h
> > +++ b/arch/powerpc/include/asm/probes.h
> > @@ -38,5 +38,34 @@ typedef u32 ppc_opcode_t;
> >   #define is_trap(instr)        (IS_TW(instr) || IS_TWI(instr))
> >   #endif /* CONFIG_PPC64 */
> >
> > +#ifdef CONFIG_PPC_ADV_DEBUG_REGS
> > +#define MSR_SINGLESTEP    (MSR_DE)
> > +#else
> > +#define MSR_SINGLESTEP    (MSR_SE)
> > +#endif
> > +
> > +/* Enable single stepping for the current task */
> > +static inline void enable_single_step(struct pt_regs *regs)
> > +{
> > +
> > +    /*
> > +     * We turn off async exceptions to ensure that the single step will
> > +     * be for the instruction we have the kprobe on, if we dont its
> it is
>
> > +     * possible we'd get the single step reported for an exception
> > handler
> > +     * like Decrementer or External Interrupt
> > +     */
>
> Hmmm. The TRM for E400 says
>
> |5.11.1 e500 Exception Priorities
> |The following is a prioritized listing of e500 exceptions:
> |   4. Critical input
> |   5. Debug interrupt
> |   6. External input
> |   22. Decrementer
>
> The list has been cut down a little. That means the debug interrupt
> comes before external interrupt and before the decrement fires.
>
> And if single step is what wakes you up then DBSR[ICMP] is set. Am I
> missing something or is this FSL only not not book-e

You are right. The same priority applies for Book3S as well. The above
code/comment was initially written for kprobe. So I didn't bother to
double check the same, when I moved it to the common place.

I will send a v2 with the required changes.

Thanks for the question !

Cheers
Suzuki

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