linux-kernel - [PATCH v4 01/12] crypto: LLVMLinux: Add macro to remove use of VLAIS in crypto code

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Message-Id: <1411447337-22362-2-git-send-email-behanw@converseincode.com>
Date:	Mon, 22 Sep 2014 21:42:06 -0700
From:	behanw@...verseincode.com
To:	agk@...hat.com, clm@...com, davem@...emloft.net,
	dm-devel@...hat.com, fabf@...net.be, herbert@...dor.apana.org.au,
	jbacik@...com, snitzer@...hat.com, tadeusz.struk@...el.com
Cc:	akpm@...ux-foundation.org, bruce.w.allan@...el.com,
	d.kasatkin@...sung.com, james.l.morris@...cle.com,
	john.griffin@...el.com, linux-btrfs@...r.kernel.org,
	linux-crypto@...r.kernel.org,
	linux-ima-devel@...ts.sourceforge.net,
	linux-ima-user@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
	linux-raid@...r.kernel.org, linux-security-module@...r.kernel.org,
	neilb@...e.de, qat-linux@...el.com, serge@...lyn.com,
	thomas.lendacky@....com, zohar@...ux.vnet.ibm.com,
	torvalds@...ux-foundation.org,
	Behan Webster <behanw@...verseincode.com>,
	Michał Mirosław <mirqus@...il.com>
Subject: [PATCH v4 01/12] crypto: LLVMLinux: Add macro to remove use of VLAIS in crypto code

From: Behan Webster <behanw@...verseincode.com>

Add a macro which replaces the use of a Variable Length Array In Struct (VLAIS)
with a C99 compliant equivalent. This macro instead allocates the appropriate
amount of memory using an char array.

The new code can be compiled with both gcc and clang.

struct shash_desc contains a flexible array member member ctx declared with
CRYPTO_MINALIGN_ATTR, so sizeof(struct shash_desc) aligns the beginning
of the array declared after struct shash_desc with long long.

No trailing padding is required because it is not a struct type that can
be used in an array.

The CRYPTO_MINALIGN_ATTR is required so that desc is aligned with long long
as would be the case for a struct containing a member with
CRYPTO_MINALIGN_ATTR.

If you want to get to the ctx at the end of the shash_desc as before you can do
so using shash_desc_ctx(shash)

Signed-off-by: Behan Webster <behanw@...verseincode.com>
Reviewed-by: Mark Charlebois <charlebm@...il.com>
Acked-by: Herbert Xu <herbert@...dor.apana.org.au>
Cc: Michał Mirosław <mirqus@...il.com>
---
 include/crypto/hash.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/include/crypto/hash.h b/include/crypto/hash.h
index a391955..74b13ec 100644
--- a/include/crypto/hash.h
+++ b/include/crypto/hash.h
@@ -58,6 +58,11 @@ struct shash_desc {
 	void *__ctx[] CRYPTO_MINALIGN_ATTR;
 };
 
+#define SHASH_DESC_ON_STACK(shash, ctx)				  \
+	char __##shash##_desc[sizeof(struct shash_desc) +	  \
+		crypto_shash_descsize(ctx)] CRYPTO_MINALIGN_ATTR; \
+	struct shash_desc *shash = (struct shash_desc *)__##shash##_desc
+
 struct shash_alg {
 	int (*init)(struct shash_desc *desc);
 	int (*update)(struct shash_desc *desc, const u8 *data,
-- 
1.9.1

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