Re: [PATCH v4] livepatch: introduce shadow variable API

[Joe Lawrence <joe.lawrence@redhat.com>]

On 08/16/2017 08:43 AM, Miroslav Benes wrote:
> 
>> [ ... snip ... ]
> 
> There is a comment above about locking and we do not take the spinlock 
> here. That could surprise someone. So I'd keep only klp_shadow_add() 
> comment, because there it is strictly needed. It depends on the context in 
> all other cases.

Good catch, I think this changed in this last version when I moved some
of the work outside the lock.

> Could you also add a comment above klp_shadow_lock definition about what 
> it aims to protect?
> 

How about "klp_shadow_lock provides exclusive access to the
klp_shadow_hash and the shadow variables it references."  or were
thinking of something more detailed?

>> +	/* Look for <obj, id> again under the lock */
>> +	spin_lock_irqsave(&klp_shadow_lock, flags);
>> +	shadow_data = klp_shadow_get(obj, id);
>> +	if (unlikely(shadow_data)) {
> 
> shadow_data is not needed anywhere, so you could do the same as for the 
> first speculative search and remove shadow_data variable all together.

Ok.

>> [ ... snip ... ]
> 
> Otherwise it looks good. You can add my
> 
> Acked-by: Miroslav Benes <mbenes@suse.cz>
> 
> with those nits fixed.

Thank you for all the suggestions and reviews!

-- Joe