Re: [discuss] Re: [PATCH 2/3] reliable stack trace support (x86-64)

[Andi Kleen]

On Tuesday 16 May 2006 18:06, Jan Beulich wrote:
> >>> Andi Kleen <ak@xxxxxxx> 16.05.06 17:13 >>>
> On Tuesday 16 May 2006 16:21, Jan Beulich wrote:
> >> These are the x86_64-specific pieces to enable reliable stack traces. The
> >> only restriction with this is that it currently cannot unwind across the
> >> interrupt->normal stack boundary, as that transition is lacking proper
> >> annotation.
> >
> >It would be nice if you could submit a patch to fix that.
> 
> But I don't know how to fix it. See my other mail 
which mail?


> - I have no experience with expressions, nor have I ever seen them in 
> use.

I remember Jim Houston used a hack of just loading the old stack into a register
and defining that as a base register in CFI. I guess i would be willing 
to trade a few moves for that (should be pretty much free on a OOO CPU anyways) 
You think that trick would work?
 
> >> +#define UNW_PC(frame) (frame)->regs.rip
> >> +#define UNW_SP(frame) (frame)->regs.rsp
> >
> >I think we alreay have instruction_pointer(). Better add a stack_pointer() 
> >in ptrace.h too.
> 
> I could do that, but the macros will have to remain, as they don't access pt_regs directly, so I guess it'd be
> pointless to change it.

UNW_PC() is instruction_pointer(&frame->regs), isn't it?

-Andi
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