Re: [PATCH v2] arm: cmpxchg syscall should data abort if page notwrite

From: Nicolas Pitre
Date: Mon Mar 21 2011 - 16:41:30 EST

On Fri, 18 Mar 2011, Po-Yu Chuang wrote:

> On Fri, Mar 18, 2011 at 1:57 AM, Nicolas Pitre <nicolas.pitre@xxxxxxxxxx> wrote:
> > Nope. ÂThe code being fixed here was suptly broken so it needs fixing.
> > However this code is almost never used, if at all, as it is a fall-back
> > solution for when all the better alternatives are not available for some
> > reasons (and I'm still wondering what those reasons are for Po-Yu Chuang
> > to actually use that code). ÂIn practice this bug should have affected
> > no one.
> We met this problem while porting an v5 SMP processor because kernel
> selects NEEDS_SYSCALL_FOR_CMPXCHG by default if CPU_32v5.
> After we added our own implementation of __kuser_cmpxchg, this code
> is not needed anymore. But since this is actually a bug, it is still a good
> idea to submit a patch. :-)

Yes. Please send to RMK's patch system with my ACK.