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Re: Problem with GDB when debugging IRQ handlers
On Tue, Jun 28, 2011 at 03:37:59PM +0100, Russell King - ARM Linux wrote:
> On Tue, Jun 28, 2011 at 03:30:14PM +0100, Catalin Marinas wrote:
> > Actually since the return address is in S_PC (which maybe gdb assumes it
> > would be the saved LR), this is probably not be correct. After SVC
> > entry, we have he following structure on the stack:
> >
> > ORIG_r0
> > CPSR
> > <--- assuming this is the Call Frame Address (SP+S_PC+4)
> > PC <--- CFA - 4
> > LR <--- don't care
> > SP <--- CFA - 12
> > ...
>
> If I'm reading this correctly, it's not correct.
>
> parent SP --> parent context stack
> [possible empty word]
> ORIG_r0
> parent context CPSR
> parent context PC
> parent context LR
> parent context SP
> ...
> new SP --> R0
>
> That empty word may or may not be present if the parent SP is aligned to
> a 64-bit boundary.
But it shouldn't matter if we tell gdb that the previous SP (parent) is
stored in the current stack at CFA - 12. It calculates CFA by adding
S_PC+4 to the current SP, in which case the possible empty word doesn't
matter.
But please note that I don't have any gdb experience, so we need someone
else to confirm.
--
Catalin