Subject: Re: patch_v3: emulating missing instructions on Alpha
From: Richard Henderson (rth@twiddle.net)
Date: Sat Oct 23 1999 - 13:55:44 PDT
On Fri, Oct 22, 1999 at 02:23:22AM +1000, Luke Deller wrote:
> + srl $0,LOG2_TASKSIZE,$5 /* if addr is not in userland, */
> + cmovne $5,$31,$0 /* then force a segfault by putting addr=0 */
> + ldq_u $3,0($0)
> + ldq_u $5,1($0)
This is not sufficient to be safe. Examine the extended
measures taken by the uaccess.h code.
I know you spent a lot of time writing this in assembly,
but I'd feel more comfortable if this were in C hanging
out with the existing opDEC code in do_entIF. There won't
be _that_ much of a speed hit doing things that way. You
get to resuse much of the entArith_User code.
DU has a defined interface through setsysinfo to turn this stuff
on and off -- use that and you don't have to conditionally
compile the code. If you don't have access to the appropriate
DU headers, I can dig them up at work later.
r~
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