Re: Q: crypto/cipher.c

From: Paulo Marques
Date: Mon Apr 20 2009 - 14:41:56 EST


H Hartley Sweeten wrote:
> Hello all,

Hi,

> I have a question about the following code in crypto/cipher.c.
>
> static void cipher_crypt_unaligned(void (*fn)(struct crypto_tfm *, u8 *,
> const u8 *),
> struct crypto_tfm *tfm,
> u8 *dst, const u8 *src)
> {
> unsigned long alignmask = crypto_tfm_alg_alignmask(tfm);
> unsigned int size = crypto_tfm_alg_blocksize(tfm);
> u8 buffer[size + alignmask];
> u8 *tmp = (u8 *)ALIGN((unsigned long)buffer, alignmask + 1);
>
> memcpy(tmp, src, size);
> fn(tfm, tmp, tmp);
> memcpy(dst, tmp, size);
> }
>
> Doesn't the size of buffer need to be known at compile time for this
> to actually work? Or do alignmask and size work out to be constants?
>
> This appears to be buggy. But I may just be missing something...

It's a GCC extension:

http://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html

--
Paulo Marques - www.grupopie.com

"All generalizations are false."
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/