Re: [PATCH v2] crypto, dm: LLVMLinux: Remove VLAIS usage from dm-crypt

[Behan Webster]

On 09/06/14 01:46, Milan Broz wrote:
> On 09/06/2014 01:02 AM, behanw@xxxxxxxxxxxxxxxxxx wrote:
> > From: Jan-Simon MÃller <dl9pf@xxxxxx>
> >
> > The use of variable length arrays in structs (VLAIS) in the Linux Kernel code
> > precludes the use of compilers which don't implement VLAIS (for instance the
> > Clang compiler). This patch instead allocates the appropriate amount of memory
> > using an char array.
> Well, if clang (or C99 code) is now preferred for kernel, why not.
>
> Just please commit the patch series en bloc (together with the patches
> removing VLAIS from crypto code you posted to cryptoapi list).
They seemed more separate than that. However, happy to post them as a 
patch set.

> > -	struct {
> > -		struct shash_desc desc;
> > -		char ctx[crypto_shash_descsize(lmk->hash_tfm)];
> > -	} sdesc;
> > +	char sdesc[sizeof(struct shash_desc) +
> > +		crypto_shash_descsize(lmk->hash_tfm)] CRYPTO_MINALIGN_ATTR;
> > +	struct shash_desc *desc = (struct shash_desc *)sdesc;
> TBH, this looks even more uglier that the previous code :-)
I'm not claiming it's prettier. Merely C99. :)

> (But tglx already complained on different patch and I fully agree that crypto code
> should not use this kind of construction in the first place...
> It would be very nice to introduce at least some macro hiding these crazy
> stack allocations later.)
I actually agree with you and tglx. Will fix.

As I said to tglx, we were asked not to hide things with macro magic in 
some of our non-crypto VLAIS removal patches. Happy to use macros in 
this case.

Thanks,

Behan

--
Behan Webster
behanw@xxxxxxxxxxxxxxxxxx

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