cvs commit: src/sys/ia64/ia64 syscall.S
marcel at FreeBSD.org
Mon Jul 16 16:47:35 UTC 2007
marcel 2007-07-16 16:47:35 UTC
FreeBSD src repository
Restore the value of ar.rnat after the assignment to ar.bspstore.
The SDM states that writing to ar.bspstore invalidates the ar.rnat
register as a side-effect. This was interpreted as "bits in the
ar.rnat register that correspond to registers whose value is on
the stack are undefined'. Since we keep the kernel stack NaT-
aligned with the user stack (i.e. the lower 9 bits of the backing
store pointer remain unchanged when we switch to the kernel stack)
bits that need preserving would be preserved.
That interpretation is questionable. So, now, the interpretation
is more absolute: ar.rnat is undefined after writing to ar.bspstore.
As such, we write the saved value of ar.rnat back to ar.rnat after
writing to ar.bspstore.
Discussed with: christian.kandeler at hob.de
Approved by: re (kensmith)
Revision Changes Path
1.15 +3 -3 src/sys/ia64/ia64/syscall.S
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