crypto: arm/ghash - use variably sized key struct

Of the two versions of GHASH that the ARM driver implements, only one
performs aggregation, and so the other one has no use for the powers
of H to be precomputed, or space to be allocated for them in the key
struct. So make the context size dependent on which version is being
selected, and while at it, use a static key to carry this decision,
and get rid of the function pointer.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

arch/arm/crypto/ghash-ce-glue.c

@@ -16,6 +16,7 @@
 #include <crypto/gf128mul.h>
 #include <linux/cpufeature.h>
 #include <linux/crypto.h>
+#include <linux/jump_label.h>
 #include <linux/module.h>
 
 MODULE_DESCRIPTION("GHASH hash function using ARMv8 Crypto Extensions");
@@ -27,12 +28,8 @@ MODULE_ALIAS_CRYPTO("ghash");
 #define GHASH_DIGEST_SIZE	16
 
 struct ghash_key {
-	u64	h[2];
-	u64	h2[2];
-	u64	h3[2];
-	u64	h4[2];
-
 	be128	k;
+	u64	h[][2];
 };
 
 struct ghash_desc_ctx {
@@ -46,16 +43,12 @@ struct ghash_async_ctx {
 };
 
 asmlinkage void pmull_ghash_update_p64(int blocks, u64 dg[], const char *src,
-				       struct ghash_key const *k,
-				       const char *head);
+				       u64 const h[][2], const char *head);
 
 asmlinkage void pmull_ghash_update_p8(int blocks, u64 dg[], const char *src,
-				      struct ghash_key const *k,
-				      const char *head);
+				      u64 const h[][2], const char *head);
 
-static void (*pmull_ghash_update)(int blocks, u64 dg[], const char *src,
-				  struct ghash_key const *k,
-				  const char *head);
+static __ro_after_init DEFINE_STATIC_KEY_FALSE(use_p64);
 
 static int ghash_init(struct shash_desc *desc)
 {
@@ -70,7 +63,10 @@ static void ghash_do_update(int blocks, u64 dg[], const char *src,
 {
 	if (likely(crypto_simd_usable())) {
 		kernel_neon_begin();
-		pmull_ghash_update(blocks, dg, src, key, head);
+		if (static_branch_likely(&use_p64))
+			pmull_ghash_update_p64(blocks, dg, src, key->h, head);
+		else
+			pmull_ghash_update_p8(blocks, dg, src, key->h, head);
 		kernel_neon_end();
 	} else {
 		be128 dst = { cpu_to_be64(dg[1]), cpu_to_be64(dg[0]) };
@@ -161,25 +157,26 @@ static int ghash_setkey(struct crypto_shash *tfm,
 			const u8 *inkey, unsigned int keylen)
 {
 	struct ghash_key *key = crypto_shash_ctx(tfm);
-	be128 h;
 
 	if (keylen != GHASH_BLOCK_SIZE)
 		return -EINVAL;
 
 	/* needed for the fallback */
 	memcpy(&key->k, inkey, GHASH_BLOCK_SIZE);
-	ghash_reflect(key->h, &key->k);
+	ghash_reflect(key->h[0], &key->k);
 
-	h = key->k;
-	gf128mul_lle(&h, &key->k);
-	ghash_reflect(key->h2, &h);
+	if (static_branch_likely(&use_p64)) {
+		be128 h = key->k;
 
 		gf128mul_lle(&h, &key->k);
-	ghash_reflect(key->h3, &h);
+		ghash_reflect(key->h[1], &h);
 
 		gf128mul_lle(&h, &key->k);
-	ghash_reflect(key->h4, &h);
+		ghash_reflect(key->h[2], &h);
 
+		gf128mul_lle(&h, &key->k);
+		ghash_reflect(key->h[3], &h);
+	}
 	return 0;
 }
 
@@ -195,7 +192,7 @@ static struct shash_alg ghash_alg = {
 	.base.cra_driver_name	= "ghash-ce-sync",
 	.base.cra_priority	= 300 - 1,
 	.base.cra_blocksize	= GHASH_BLOCK_SIZE,
-	.base.cra_ctxsize	= sizeof(struct ghash_key),
+	.base.cra_ctxsize	= sizeof(struct ghash_key) + sizeof(u64[2]),
 	.base.cra_module	= THIS_MODULE,
 };
 
@@ -354,10 +351,10 @@ static int __init ghash_ce_mod_init(void)
 	if (!(elf_hwcap & HWCAP_NEON))
 		return -ENODEV;
 
-	if (elf_hwcap2 & HWCAP2_PMULL)
-		pmull_ghash_update = pmull_ghash_update_p64;
-	else
-		pmull_ghash_update = pmull_ghash_update_p8;
+	if (elf_hwcap2 & HWCAP2_PMULL) {
+		ghash_alg.base.cra_ctxsize += 3 * sizeof(u64[2]);
+		static_branch_enable(&use_p64);
+	}
 
 	err = crypto_register_shash(&ghash_alg);
 	if (err)