[RFC PATCH] uprobes: copy to user-space xol page with proper cache flushing

[Peter Zijlstra]

On Fri, Apr 11, 2014 at 05:00:29PM +0100, Russell King - ARM Linux wrote:
> On Fri, Apr 11, 2014 at 05:32:49PM +0200, Peter Zijlstra wrote:
> > On Fri, Apr 11, 2014 at 05:22:07PM +0200, Oleg Nesterov wrote:
> > > And I am just curious, why arm's copy_to_user_page() disables premption
> > > before memcpy?
> > 
> > Without looking, I suspect its because the VIVT caches, they need to get
> > shot down on every context switch.
> 
> So... let's think about that for a moment... if we have a preemption event,
> then that's a context switch, which means...
> 
> No, this is obviously not the reason, because such an event on a fully
> VIVT system would result in the caches being flushed, meaning that we
> wouldn't need to do anything if we could be predicably preempted at that
> point.

Yeah; I've since realized I was completely wrong about that. Thanks for
explaining though.