Re: [PATCH] Interrupt entry CONFIG_FRAME_POINTER fix

[Tejun Heo <tj@home-tj.org>]

On Sun, Sep 12, 2004 at 01:10:26PM -0400, Zwane Mwaikambo wrote:
> On Sun, 12 Sep 2004, Andi Kleen wrote:
> > On Sun, 12 Sep 2004 18:16:28 +0900
> > Tejun Heo <tj@home-tj.org> wrote:
> > 
> > >  On x86_64, rbp isn't saved on entering interrupt handler even when
> > > CONFIG_FRAME_POINTER is turned on.  This breaks profile_pc()
> > > (resulting in oops) which uses regs->rbp to track back to the original
> > > stack.  Save full stack when CONFIG_FRAME_POINTER is specified.
> > 
> > 
> > I don't think your patch is correct, you don't restore rbp ever and it gets corrupted.
> > 
> > I think the correct change is to fix profile_pc() to not reference rbp, but just hardcode
> > the rsp offset for the FP and non FP cases (8 and 0) 
> 
> Yep, i botched up the patch, after looking at the disassembly on 
> x86_64 without CONFIG_FRAME_POINTER again it's definitely incorrect. In 
> fact there are still a few users such as _spin_lock_irqsave which push 
> flags onto the stack and the stack pointer isn't consistent across all 
> functions in that text section. I'm going to have to try Andi's previous 
> suggestions.

 I'm sorry but I guess I'm slow today. :-( Can you please be kind
enough to lighten me up on how things get corrupted?  I've read the
assembly source and disassembly of the output but I don't really see
how it'll get corrupted.

-- 
tejun