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

[David Mosberger <davidm@napali.hpl.hp.com>]

>>>>> On Sat, 31 May 2003 00:18:39 +1000, Matt Chapman <matthewc@cse.unsw.edu.au> said:

  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.  This happens more often then
  Matt> you'd expect, since it seems that current implementations make
  Matt> the optimisation of writing the RNAT word together with the
  Matt> first word of the new group instead of the last word of the
  Matt> old group (sensible because it potentially saves a write).

Yes, I noticed the same in libunwind. ;-/

  Matt> I'd propose that the trampoline code should save bspstore in
  Matt> the sigcontext structure and restore it from there rather than
  Matt> recalculating it.  I can send a patch, but first is there any
  Matt> reason why it shouldn't be done that way?

My preference would be to fix it in a way that preserves binary
compatibility for the sigcontext structure.

	--david