On Wed, 2002-02-06 at 11:01, Russell King - ARM Linux wrote:
> On Wed, Feb 06, 2002 at 10:51:50AM +0000, Phil Blundell wrote:
> > Be nice to be able to do that for unaligned accesses too.
> 
> How does a program determine if it should or shouldn't enable the
> unaligned accesses?

Some kind of system call I guess.  That's the way Alpha does it; they
have a couple of bits in current->thread that inherit across fork, with
a syscall to manipulate them.  In the specific alpha case it's part of
OSF_SETSYSINFO; for arm it would probably want to be a dedicated
syscall.

If you meant the question at a higher level, "what actually decides
whether to allow unaligned accesses or not", it's a user decision.  You
have a small helper program, conceptually like "nohup", that just
enables or disables the traps and then execs something else.  That's
what I envisaged for selectively disabling FPA emulation too.

p.


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