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

[David Miller]

From: Oleg Nesterov <oleg at redhat.com>
Date: Tue, 15 Apr 2014 20:03:11 +0200

> On 04/15, David Miller wrote:
>>
>> From: Oleg Nesterov <oleg at redhat.com>
>> Date: Tue, 15 Apr 2014 19:43:30 +0200
>>
>> > Finally, let me repeat, you should verify that this
>> > __copy_to_user_page(page, uaddr, kaddr) will not something bad if uaddr
>> > is not mmapped, or its mapping do not match area->page.
>>
>> Just directly access userspace with the usual exception mechanism we
>> use for copy_to_user(), put_user(), et al. and if it faults you'll get
>> -EFAULT and handle it.
>>
>> This also avoids the D-cache aliasing issues entirely as I explained
>> in my other reply.
> 
> Yes, yes, this is obvious.
> 
> But I have no idea what else we should do to take care of icache.

Russell, if for example userland stores into the instruction stream
to patch an instruction, what needs to be done on ARM?