Re: [Linux-ia64] sigaltstack and ar.bspstore

[Matt Chapman <matthewc@cse.unsw.edu.au>]

On Fri, Jun 20, 2003 at 11:05:30PM -0700, David Mosberger wrote:
> >>>>> On Sat, 31 May 2003 00:18:39 +1000, Matt Chapman <matthewc@cse.unsw.edu.au> said:
> 
>   Matt> Currently when using an alternate stack for signal handling,
>   Matt> the trampoline code switches to the new register stack without
>   Matt> saving bspstore.  When returning to the original register
>   Matt> stack, it calculates the bspstore as:
> 
>   Matt>   bspstore0 = rse_skip_regs(bsp0, -rse_num_regs(bsp1 - (loadrs
>   Matt> >> 19), bsp1)); where bsp0 is sc->sc_ar_bsp and bsp1 is the
>   Matt> current bsp
> 
>   Matt> Presumably the result should be the same as the original
>   Matt> bspstore.  However, it isn't in the case when the original
>   Matt> bspstore is pointing to slot 63 (the RNAT word).  The new
>   Matt> bspstore comes out pointing to slot 0 of the next group, and
>   Matt> the RNAT bits never get written.
> 
> Yes, this is a problem.  Can you try the attached patch?  Rather than
> storing an additional sc_bspstore member, the backing-store switching
> code checks whether bspstore points to an RNaT slot and, if so, stores
> the RNaT manually.  This effectively "normalizes" the backing-store
> such that ar.bspstore never points to an RNaT slot.

Ah, that's a good way of doing it (given the constraints of backwards
compatibility).  I've tested your patch and it works well for me.

Thanks!

Matt


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