crypto: aesni - replace function pointers with static branches

Replace the function pointers in the GCM implementation with static branches,
which are based on code patching, which occurs only at module load time.
This avoids the severe performance penalty caused by the use of retpolines.

In order to retain the ability to switch between different versions of the
implementation based on the input size on cores that support AVX and AVX2,
use static branches instead of static calls.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

arch/x86/crypto/aesni-intel_glue.c

@@ -31,6 +31,7 @@
 #include <crypto/internal/aead.h>
 #include <crypto/internal/simd.h>
 #include <crypto/internal/skcipher.h>
+#include <linux/jump_label.h>
 #include <linux/workqueue.h>
 #include <linux/spinlock.h>
 
@@ -128,24 +129,6 @@ asmlinkage void aesni_gcm_finalize(void *ctx,
 				   struct gcm_context_data *gdata,
 				   u8 *auth_tag, unsigned long auth_tag_len);
 
-static const struct aesni_gcm_tfm_s {
-	void (*init)(void *ctx, struct gcm_context_data *gdata, u8 *iv,
-		     u8 *hash_subkey, const u8 *aad, unsigned long aad_len);
-	void (*enc_update)(void *ctx, struct gcm_context_data *gdata, u8 *out,
-			   const u8 *in, unsigned long plaintext_len);
-	void (*dec_update)(void *ctx, struct gcm_context_data *gdata, u8 *out,
-			   const u8 *in, unsigned long ciphertext_len);
-	void (*finalize)(void *ctx, struct gcm_context_data *gdata,
-			 u8 *auth_tag, unsigned long auth_tag_len);
-} *aesni_gcm_tfm;
-
-static const struct aesni_gcm_tfm_s aesni_gcm_tfm_sse = {
-	.init = &aesni_gcm_init,
-	.enc_update = &aesni_gcm_enc_update,
-	.dec_update = &aesni_gcm_dec_update,
-	.finalize = &aesni_gcm_finalize,
-};
-
 asmlinkage void aes_ctr_enc_128_avx_by8(const u8 *in, u8 *iv,
 		void *keys, u8 *out, unsigned int num_bytes);
 asmlinkage void aes_ctr_enc_192_avx_by8(const u8 *in, u8 *iv,
@@ -175,13 +158,6 @@ asmlinkage void aesni_gcm_finalize_avx_gen2(void *ctx,
 				   struct gcm_context_data *gdata,
 				   u8 *auth_tag, unsigned long auth_tag_len);
 
-static const struct aesni_gcm_tfm_s aesni_gcm_tfm_avx_gen2 = {
-	.init = &aesni_gcm_init_avx_gen2,
-	.enc_update = &aesni_gcm_enc_update_avx_gen2,
-	.dec_update = &aesni_gcm_dec_update_avx_gen2,
-	.finalize = &aesni_gcm_finalize_avx_gen2,
-};
-
 /*
  * asmlinkage void aesni_gcm_init_avx_gen4()
  * gcm_data *my_ctx_data, context data
@@ -205,12 +181,8 @@ asmlinkage void aesni_gcm_finalize_avx_gen4(void *ctx,
 				   struct gcm_context_data *gdata,
 				   u8 *auth_tag, unsigned long auth_tag_len);
 
-static const struct aesni_gcm_tfm_s aesni_gcm_tfm_avx_gen4 = {
-	.init = &aesni_gcm_init_avx_gen4,
-	.enc_update = &aesni_gcm_enc_update_avx_gen4,
-	.dec_update = &aesni_gcm_dec_update_avx_gen4,
-	.finalize = &aesni_gcm_finalize_avx_gen4,
-};
+static __ro_after_init DEFINE_STATIC_KEY_FALSE(gcm_use_avx);
+static __ro_after_init DEFINE_STATIC_KEY_FALSE(gcm_use_avx2);
 
 static inline struct
 aesni_rfc4106_gcm_ctx *aesni_rfc4106_gcm_ctx_get(struct crypto_aead *tfm)
@@ -641,12 +613,12 @@ static int gcmaes_crypt_by_sg(bool enc, struct aead_request *req,
 			      u8 *iv, void *aes_ctx, u8 *auth_tag,
 			      unsigned long auth_tag_len)
 {
-	const struct aesni_gcm_tfm_s *gcm_tfm = aesni_gcm_tfm;
 	u8 databuf[sizeof(struct gcm_context_data) + (AESNI_ALIGN - 8)] __aligned(8);
 	struct gcm_context_data *data = PTR_ALIGN((void *)databuf, AESNI_ALIGN);
 	unsigned long left = req->cryptlen;
 	struct scatter_walk assoc_sg_walk;
 	struct skcipher_walk walk;
+	bool do_avx, do_avx2;
 	u8 *assocmem = NULL;
 	u8 *assoc;
 	int err;
@@ -654,10 +626,8 @@ static int gcmaes_crypt_by_sg(bool enc, struct aead_request *req,
 	if (!enc)
 		left -= auth_tag_len;
 
-	if (left < AVX_GEN4_OPTSIZE && gcm_tfm == &aesni_gcm_tfm_avx_gen4)
-		gcm_tfm = &aesni_gcm_tfm_avx_gen2;
-	if (left < AVX_GEN2_OPTSIZE && gcm_tfm == &aesni_gcm_tfm_avx_gen2)
-		gcm_tfm = &aesni_gcm_tfm_sse;
+	do_avx = (left >= AVX_GEN2_OPTSIZE);
+	do_avx2 = (left >= AVX_GEN4_OPTSIZE);
 
 	/* Linearize assoc, if not already linear */
 	if (req->src->length >= assoclen && req->src->length) {
@@ -677,7 +647,14 @@ static int gcmaes_crypt_by_sg(bool enc, struct aead_request *req,
 	}
 
 	kernel_fpu_begin();
-	gcm_tfm->init(aes_ctx, data, iv, hash_subkey, assoc, assoclen);
+	if (static_branch_likely(&gcm_use_avx2) && do_avx2)
+		aesni_gcm_init_avx_gen4(aes_ctx, data, iv, hash_subkey, assoc,
+					assoclen);
+	else if (static_branch_likely(&gcm_use_avx) && do_avx)
+		aesni_gcm_init_avx_gen2(aes_ctx, data, iv, hash_subkey, assoc,
+					assoclen);
+	else
+		aesni_gcm_init(aes_ctx, data, iv, hash_subkey, assoc, assoclen);
 	kernel_fpu_end();
 
 	if (!assocmem)
@@ -690,9 +667,35 @@ static int gcmaes_crypt_by_sg(bool enc, struct aead_request *req,
 
 	while (walk.nbytes > 0) {
 		kernel_fpu_begin();
-		(enc ? gcm_tfm->enc_update
-		     : gcm_tfm->dec_update)(aes_ctx, data, walk.dst.virt.addr,
-					    walk.src.virt.addr, walk.nbytes);
+		if (static_branch_likely(&gcm_use_avx2) && do_avx2) {
+			if (enc)
+				aesni_gcm_enc_update_avx_gen4(aes_ctx, data,
+							      walk.dst.virt.addr,
+							      walk.src.virt.addr,
+							      walk.nbytes);
+			else
+				aesni_gcm_dec_update_avx_gen4(aes_ctx, data,
+							      walk.dst.virt.addr,
+							      walk.src.virt.addr,
+							      walk.nbytes);
+		} else if (static_branch_likely(&gcm_use_avx) && do_avx) {
+			if (enc)
+				aesni_gcm_enc_update_avx_gen2(aes_ctx, data,
+							      walk.dst.virt.addr,
+							      walk.src.virt.addr,
+							      walk.nbytes);
+			else
+				aesni_gcm_dec_update_avx_gen2(aes_ctx, data,
+							      walk.dst.virt.addr,
+							      walk.src.virt.addr,
+							      walk.nbytes);
+		} else if (enc) {
+			aesni_gcm_enc_update(aes_ctx, data, walk.dst.virt.addr,
+					     walk.src.virt.addr, walk.nbytes);
+		} else {
+			aesni_gcm_dec_update(aes_ctx, data, walk.dst.virt.addr,
+					     walk.src.virt.addr, walk.nbytes);
+		}
 		kernel_fpu_end();
 
 		err = skcipher_walk_done(&walk, 0);
@@ -702,7 +705,14 @@ static int gcmaes_crypt_by_sg(bool enc, struct aead_request *req,
 		return err;
 
 	kernel_fpu_begin();
-	gcm_tfm->finalize(aes_ctx, data, auth_tag, auth_tag_len);
+	if (static_branch_likely(&gcm_use_avx2) && do_avx2)
+		aesni_gcm_finalize_avx_gen4(aes_ctx, data, auth_tag,
+					    auth_tag_len);
+	else if (static_branch_likely(&gcm_use_avx) && do_avx)
+		aesni_gcm_finalize_avx_gen2(aes_ctx, data, auth_tag,
+					    auth_tag_len);
+	else
+		aesni_gcm_finalize(aes_ctx, data, auth_tag, auth_tag_len);
 	kernel_fpu_end();
 
 	return 0;
@@ -1141,14 +1151,14 @@ static int __init aesni_init(void)
 #ifdef CONFIG_X86_64
 	if (boot_cpu_has(X86_FEATURE_AVX2)) {
 		pr_info("AVX2 version of gcm_enc/dec engaged.\n");
-		aesni_gcm_tfm = &aesni_gcm_tfm_avx_gen4;
+		static_branch_enable(&gcm_use_avx);
+		static_branch_enable(&gcm_use_avx2);
 	} else
 	if (boot_cpu_has(X86_FEATURE_AVX)) {
 		pr_info("AVX version of gcm_enc/dec engaged.\n");
-		aesni_gcm_tfm = &aesni_gcm_tfm_avx_gen2;
+		static_branch_enable(&gcm_use_avx);
 	} else {
 		pr_info("SSE version of gcm_enc/dec engaged.\n");
-		aesni_gcm_tfm = &aesni_gcm_tfm_sse;
 	}
 	aesni_ctr_enc_tfm = aesni_ctr_enc;
 	if (boot_cpu_has(X86_FEATURE_AVX)) {