ia64/120315: Backing store switch in exception_save_restart leaves ar.rnat undefined

[Christian Kandeler]

>Number:         120315
>Category:       ia64
>Synopsis:       Backing store switch in exception_save_restart leaves ar.rnat undefined
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-ia64
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Wed Feb 06 11:50:02 UTC 2008
>Closed-Date:
>Last-Modified:
>Originator:     Christian Kandeler
>Release:        >= 5.2
>Organization:
HOB
>Environment:
>Description:
The move to bspstore in exception_save_restart (file ia64/ia64/exception.S) invalidates ar.rnat, which has to be recovered from r19, but isn't. This is the same problem that existed in epc_syscall (see this thread: http://lists.freebsd.org/pipermail/freebsd-ia64/2007-June/001391.html). It will most likely crash Itanium processors that define the "undefined()" value as used in the SDM as something else than zero, which is perfectly possible.

>How-To-Repeat:

>Fix:
Insert a mov ar.rnat=r19 after the move to bspstore. I am not including a patch because I don't want to mess with the hand-crafted bundles.

>Release-Note:
>Audit-Trail:
>Unformatted: