[CRYPTO] api: Align tfm context as wide as possible

Since tfm contexts can contain arbitrary types we should provide at least
natural alignment (__attribute__ ((__aligned__))) for them.  In particular,
this is needed on the Xscale which is a 32-bit architecture with a u64 type
that requires 64-bit alignment.  This problem was reported by Ronen Shitrit.

The crypto_tfm structure's size was 44 bytes on 32-bit architectures and
80 bytes on 64-bit architectures.  So adding this requirement only means
that we have to add an extra 4 bytes on 32-bit architectures.

On i386 the natural alignment is 16 bytes which also benefits the VIA
Padlock as it no longer has to manually align its context structure to
128 bits.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/api.c

@@ -165,7 +165,7 @@ static unsigned int crypto_ctxsize(struct crypto_alg *alg, int flags)
 		break;
 	}
 
-	return len + alg->cra_alignmask;
+	return len + (alg->cra_alignmask & ~(crypto_tfm_ctx_alignment() - 1));
 }
 
 struct crypto_tfm *crypto_alloc_tfm(const char *name, u32 flags)

drivers/crypto/padlock-aes.c

@@ -284,7 +284,11 @@ aes_hw_extkey_available(uint8_t key_len)
 
 static inline struct aes_ctx *aes_ctx(void *ctx)
 {
-	return (struct aes_ctx *)ALIGN((unsigned long)ctx, PADLOCK_ALIGNMENT);
+	unsigned long align = PADLOCK_ALIGNMENT;
+
+	if (align <= crypto_tfm_ctx_alignment())
+		align = 1;
+	return (struct aes_ctx *)ALIGN((unsigned long)ctx, align);
 }
 
 static int

include/linux/crypto.h

@@ -229,6 +229,8 @@ struct crypto_tfm {
 	} crt_u;
 	
 	struct crypto_alg *__crt_alg;
+
+	char __crt_ctx[] __attribute__ ((__aligned__));
 };
 
 /* 
@@ -301,7 +303,13 @@ static inline unsigned int crypto_tfm_alg_alignmask(struct crypto_tfm *tfm)
 
 static inline void *crypto_tfm_ctx(struct crypto_tfm *tfm)
 {
-	return (void *)&tfm[1];
+	return tfm->__crt_ctx;
+}
+
+static inline unsigned int crypto_tfm_ctx_alignment(void)
+{
+	struct crypto_tfm *tfm;
+	return __alignof__(tfm->__crt_ctx);
 }
 
 /*