On March 17, 2017 12:27:46 PM PDT, Peter Zijlstra [off-list ref] wrote:

On Fri, Mar 17, 2017 at 11:52:01AM -0700, Michael Davidson wrote:

quoted

On Fri, Mar 17, 2017 at 5:44 AM, Peter Zijlstra

[off-list ref] wrote:

quoted

quoted

Be that as it may; what you construct above is disgusting. Surely

the

quoted

quoted

code can be refactored to not look like dog vomit?

Also; its not immediately obvious conf->copies is 'small' and this
doesn't blow up the stack; I feel that deserves a comment

somewhere.

quoted

quoted

I agree that the code is horrible.

It is, in fact, exactly the same solution that was used to remove
variable length arrays in structs from several of the crypto drivers

a

quoted

few years ago - see the definition of SHASH_DESC_ON_STACK() in
"crypto/hash.h" - I did not, however, hide the horrors in a macro
preferring to leave the implementation visible as a warning to

whoever

quoted

might touch the code next.

I believe that the actual stack usage is exactly the same as it was

previously.

quoted

I can certainly wrap this  up in a macro and add comments with
appropriately dire warnings in it if you feel that is both necessary
and sufficient.

We got away with ugly in the past, so we should get to do it again?

Seriously, you should have taken the hack the first time that this needs to be fixed.  Just because this is a fairly uncommon construct in the kernel doesn't mean it is not in userspace.

I would like to say this falls in the category of "fix your compiler this time".  Once is one thing, twice is unacceptable.
-- 
Sent from my Android device with K-9 Mail. Please excuse my brevity.