linux-kernel - RE: [PATCH v3] mac80211: LLVMLinux: Remove VLAIS usage from mac80211

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Date:	Wed, 19 Mar 2014 14:09:57 +0000
From:	David Laight <David.Laight@...LAB.COM>
To:	"'behanw@...verseincode.com'" <behanw@...verseincode.com>,
	"linville@...driver.com" <linville@...driver.com>,
	"johannes@...solutions.net" <johannes@...solutions.net>,
	"davem@...emloft.net" <davem@...emloft.net>
CC:	"linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"torvalds@...ux-foundation.org" <torvalds@...ux-foundation.org>,
	"dwmw2@...radead.org" <dwmw2@...radead.org>,
	"pageexec@...email.hu" <pageexec@...email.hu>,
	Jan-Simon Möller <dl9pf@....de>,
	Vinícius Tinti <viniciustinti@...il.com>,
	Mark Charlebois <charlebm@...il.com>
Subject: RE: [PATCH v3] mac80211: LLVMLinux: Remove VLAIS usage from mac80211

From: behanw@...verseincode.com
> Replaced the use of a Variable Length Array In Struct (VLAIS) with a C99
> compliant equivalent. This is the original VLAIS struct.
> 
> struct {
> 	struct aead_request     req;
> 	u8                      priv[crypto_aead_reqsize(tfm)];
> } aead_req;
> 
> This patch instead allocates the appropriate amount of memory using an char
> array.
> 
> The new code can be compiled with both gcc and clang.
> 
> Signed-off-by: Jan-Simon Mller <dl9pf@....de>
> Signed-off-by: Behan Webster <behanw@...verseincode.com>
> Signed-off-by: Vincius Tinti <viniciustinti@...il.com>
> Signed-off-by: Mark Charlebois <charlebm@...il.com>
> ---
>  net/mac80211/aes_ccm.c | 40 ++++++++++++++++++++++------------------
>  1 file changed, 22 insertions(+), 18 deletions(-)
> 
> diff --git a/net/mac80211/aes_ccm.c b/net/mac80211/aes_ccm.c
> index 7c7df47..20521f9 100644
> --- a/net/mac80211/aes_ccm.c
> +++ b/net/mac80211/aes_ccm.c
> @@ -23,12 +23,14 @@ void ieee80211_aes_ccm_encrypt(struct crypto_aead *tfm, u8 *b_0, u8 *aad,
>  			       u8 *data, size_t data_len, u8 *mic)
>  {
>  	struct scatterlist assoc, pt, ct[2];
> -	struct {
> -		struct aead_request	req;
> -		u8			priv[crypto_aead_reqsize(tfm)];
> -	} aead_req;
> 
> -	memset(&aead_req, 0, sizeof(aead_req));
> +	char aead_req_data[sizeof(struct aead_request) +
> +		crypto_aead_reqsize(tfm)]
> +		__aligned(__alignof__(struct aead_request));
> +
> +	struct aead_request *aead_req = (void *) aead_req_data;
> +
> +	memset(aead_req, 0, sizeof(aead_req_data));

It seems to me that the underlying function(s) ought to be changed so that
this isn't needed.
Passing an extra parameter would probably cost very little.

	David