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 <[e-mail]>
Signed-off-by: Herbert Xu <[e-mail]>

arch/x86/crypto/aesni-intel_glue.c

···
 #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>
 
···
 				   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,
···
 				   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
···
 				   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)
···
 			      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;
···
 	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) {
···
 	}
 
 	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)
···
 
 	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);
···
 		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;
···
 #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)) {