crypto: x86/chacha - depend on generic chacha library instead of crypto driver

In preparation of extending the x86 ChaCha driver to also expose the ChaCha
library interface, drop the dependency on the chacha_generic crypto driver
as a non-SIMD fallback, and depend on the generic ChaCha library directly.
This way, we only pull in the code we actually need, without registering
a set of ChaCha skciphers that we will never use.

Since turning the FPU on and off is cheap these days, simplify the SIMD
routine by dropping the per-page yield, which makes for a cleaner switch
to the library API as well. This also allows use to invoke the skcipher
walk routines in non-atomic mode.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

arch/x86/crypto/chacha_glue.c

@@ -123,37 +123,38 @@ static void chacha_dosimd(u32 *state, u8 *dst, const u8 *src,
 	}
 }
 
-static int chacha_simd_stream_xor(struct skcipher_walk *walk,
+static int chacha_simd_stream_xor(struct skcipher_request *req,
 				  const struct chacha_ctx *ctx, const u8 *iv)
 {
 	u32 *state, state_buf[16 + 2] __aligned(8);
-	int next_yield = 4096; /* bytes until next FPU yield */
-	int err = 0;
+	struct skcipher_walk walk;
+	int err;
+
+	err = skcipher_walk_virt(&walk, req, false);
 
 	BUILD_BUG_ON(CHACHA_STATE_ALIGN != 16);
 	state = PTR_ALIGN(state_buf + 0, CHACHA_STATE_ALIGN);
 
-	crypto_chacha_init(state, ctx, iv);
+	chacha_init_generic(state, ctx->key, iv);
 
-	while (walk->nbytes > 0) {
-		unsigned int nbytes = walk->nbytes;
+	while (walk.nbytes > 0) {
+		unsigned int nbytes = walk.nbytes;
 
-		if (nbytes < walk->total) {
-			nbytes = round_down(nbytes, walk->stride);
-			next_yield -= nbytes;
-		}
+		if (nbytes < walk.total)
+			nbytes = round_down(nbytes, walk.stride);
 
-		chacha_dosimd(state, walk->dst.virt.addr, walk->src.virt.addr,
-			      nbytes, ctx->nrounds);
-
-		if (next_yield <= 0) {
-			/* temporarily allow preemption */
-			kernel_fpu_end();
+		if (!crypto_simd_usable()) {
+			chacha_crypt_generic(state, walk.dst.virt.addr,
+					     walk.src.virt.addr, nbytes,
+					     ctx->nrounds);
+		} else {
 			kernel_fpu_begin();
-			next_yield = 4096;
+			chacha_dosimd(state, walk.dst.virt.addr,
+				      walk.src.virt.addr, nbytes,
+				      ctx->nrounds);
+			kernel_fpu_end();
 		}
-
-		err = skcipher_walk_done(walk, walk->nbytes - nbytes);
+		err = skcipher_walk_done(&walk, walk.nbytes - nbytes);
 	}
 
 	return err;
@@ -163,55 +164,34 @@ static int chacha_simd(struct skcipher_request *req)
 {
 	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 	struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm);
-	struct skcipher_walk walk;
-	int err;
 
-	if (req->cryptlen <= CHACHA_BLOCK_SIZE || !crypto_simd_usable())
-		return crypto_chacha_crypt(req);
-
-	err = skcipher_walk_virt(&walk, req, true);
-	if (err)
-		return err;
-
-	kernel_fpu_begin();
-	err = chacha_simd_stream_xor(&walk, ctx, req->iv);
-	kernel_fpu_end();
-	return err;
+	return chacha_simd_stream_xor(req, ctx, req->iv);
 }
 
 static int xchacha_simd(struct skcipher_request *req)
 {
 	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 	struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm);
-	struct skcipher_walk walk;
-	struct chacha_ctx subctx;
 	u32 *state, state_buf[16 + 2] __aligned(8);
+	struct chacha_ctx subctx;
 	u8 real_iv[16];
-	int err;
-
-	if (req->cryptlen <= CHACHA_BLOCK_SIZE || !crypto_simd_usable())
-		return crypto_xchacha_crypt(req);
-
-	err = skcipher_walk_virt(&walk, req, true);
-	if (err)
-		return err;
 
 	BUILD_BUG_ON(CHACHA_STATE_ALIGN != 16);
 	state = PTR_ALIGN(state_buf + 0, CHACHA_STATE_ALIGN);
-	crypto_chacha_init(state, ctx, req->iv);
-
-	kernel_fpu_begin();
-
-	hchacha_block_ssse3(state, subctx.key, ctx->nrounds);
+	chacha_init_generic(state, ctx->key, req->iv);
+
+	if (req->cryptlen > CHACHA_BLOCK_SIZE && crypto_simd_usable()) {
+		kernel_fpu_begin();
+		hchacha_block_ssse3(state, subctx.key, ctx->nrounds);
+		kernel_fpu_end();
+	} else {
+		hchacha_block_generic(state, subctx.key, ctx->nrounds);
+	}
 	subctx.nrounds = ctx->nrounds;
 
 	memcpy(&real_iv[0], req->iv + 24, 8);
 	memcpy(&real_iv[8], req->iv + 16, 8);
-	err = chacha_simd_stream_xor(&walk, &subctx, real_iv);
-
-	kernel_fpu_end();
-
-	return err;
+	return chacha_simd_stream_xor(req, &subctx, real_iv);
 }
 
 static struct skcipher_alg algs[] = {
@@ -227,7 +207,7 @@ static struct skcipher_alg algs[] = {
 		.max_keysize		= CHACHA_KEY_SIZE,
 		.ivsize			= CHACHA_IV_SIZE,
 		.chunksize		= CHACHA_BLOCK_SIZE,
-		.setkey			= crypto_chacha20_setkey,
+		.setkey			= chacha20_setkey,
 		.encrypt		= chacha_simd,
 		.decrypt		= chacha_simd,
 	}, {
@@ -242,7 +222,7 @@ static struct skcipher_alg algs[] = {
 		.max_keysize		= CHACHA_KEY_SIZE,
 		.ivsize			= XCHACHA_IV_SIZE,
 		.chunksize		= CHACHA_BLOCK_SIZE,
-		.setkey			= crypto_chacha20_setkey,
+		.setkey			= chacha20_setkey,
 		.encrypt		= xchacha_simd,
 		.decrypt		= xchacha_simd,
 	}, {
@@ -257,7 +237,7 @@ static struct skcipher_alg algs[] = {
 		.max_keysize		= CHACHA_KEY_SIZE,
 		.ivsize			= XCHACHA_IV_SIZE,
 		.chunksize		= CHACHA_BLOCK_SIZE,
-		.setkey			= crypto_chacha12_setkey,
+		.setkey			= chacha12_setkey,
 		.encrypt		= xchacha_simd,
 		.decrypt		= xchacha_simd,
 	},

crypto/Kconfig

@@ -1436,7 +1436,7 @@ config CRYPTO_CHACHA20_X86_64
 	tristate "ChaCha stream cipher algorithms (x86_64/SSSE3/AVX2/AVX-512VL)"
 	depends on X86 && 64BIT
 	select CRYPTO_SKCIPHER
-	select CRYPTO_CHACHA20
+	select CRYPTO_LIB_CHACHA_GENERIC
 	help
 	  SSSE3, AVX2, and AVX-512VL optimized implementations of the ChaCha20,
 	  XChaCha20, and XChaCha12 stream ciphers.