[PATCH v2 2/2] crypto/crc32c: Provide crc32c-arch driver for accelerated library code

[Ard Biesheuvel <ardb+git@google.com>]

From: Ard Biesheuvel <ardb@kernel.org>

crc32c-generic is currently backed by the architecture's CRC-32c library
code, which may offer a variety of implementations depending on the
capabilities of the platform. These are not covered by the crypto
subsystem's fuzz testing capabilities because crc32c-generic is the
reference driver that the fuzzing logic uses as a source of truth.

Fix this by providing a crc32c-arch implementation which is based on the
arch library code if available, and modify crc32c-generic so it is
always based on the generic C implementation. If the arch has no CRC-32c
library code, this change does nothing.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 crypto/Makefile         |  1 +
 crypto/crc32c_generic.c | 94 +++++++++++++++-----
 lib/crc32.c             |  2 +
 3 files changed, 75 insertions(+), 22 deletions(-)

diff --git a/crypto/Makefile b/crypto/Makefile
index 2d4a3c0659fa..a1ce3fa5298d 100644
--- a/crypto/Makefile
+++ b/crypto/Makefile
@@ -152,6 +152,7 @@ obj-$(CONFIG_CRYPTO_DEFLATE) += deflate.o
 obj-$(CONFIG_CRYPTO_MICHAEL_MIC) += michael_mic.o
 obj-$(CONFIG_CRYPTO_CRC32C) += crc32c_generic.o
 obj-$(CONFIG_CRYPTO_CRC32) += crc32_generic.o
+CFLAGS_crc32c_generic.o += -DARCH=$(ARCH)
 CFLAGS_crc32_generic.o += -DARCH=$(ARCH)
 obj-$(CONFIG_CRYPTO_CRCT10DIF) += crct10dif_common.o crct10dif_generic.o
 obj-$(CONFIG_CRYPTO_CRC64_ROCKSOFT) += crc64_rocksoft_generic.o
diff --git a/crypto/crc32c_generic.c b/crypto/crc32c_generic.c
index a8c90b3f4c6c..7c2357c30fdf 100644
--- a/crypto/crc32c_generic.c
+++ b/crypto/crc32c_generic.c
@@ -85,6 +85,15 @@ static int chksum_update(struct shash_desc *desc, const u8 *data,
 {
 	struct chksum_desc_ctx *ctx = shash_desc_ctx(desc);
 
+	ctx->crc = __crc32c_le_base(ctx->crc, data, length);
+	return 0;
+}
+
+static int chksum_update_arch(struct shash_desc *desc, const u8 *data,
+			      unsigned int length)
+{
+	struct chksum_desc_ctx *ctx = shash_desc_ctx(desc);
+
 	ctx->crc = __crc32c_le(ctx->crc, data, length);
 	return 0;
 }
@@ -98,6 +107,13 @@ static int chksum_final(struct shash_desc *desc, u8 *out)
 }
 
 static int __chksum_finup(u32 *crcp, const u8 *data, unsigned int len, u8 *out)
+{
+	put_unaligned_le32(~__crc32c_le_base(*crcp, data, len), out);
+	return 0;
+}
+
+static int __chksum_finup_arch(u32 *crcp, const u8 *data, unsigned int len,
+			       u8 *out)
 {
 	put_unaligned_le32(~__crc32c_le(*crcp, data, len), out);
 	return 0;
@@ -111,6 +127,14 @@ static int chksum_finup(struct shash_desc *desc, const u8 *data,
 	return __chksum_finup(&ctx->crc, data, len, out);
 }
 
+static int chksum_finup_arch(struct shash_desc *desc, const u8 *data,
+			     unsigned int len, u8 *out)
+{
+	struct chksum_desc_ctx *ctx = shash_desc_ctx(desc);
+
+	return __chksum_finup_arch(&ctx->crc, data, len, out);
+}
+
 static int chksum_digest(struct shash_desc *desc, const u8 *data,
 			 unsigned int length, u8 *out)
 {
@@ -119,6 +143,14 @@ static int chksum_digest(struct shash_desc *desc, const u8 *data,
 	return __chksum_finup(&mctx->key, data, length, out);
 }
 
+static int chksum_digest_arch(struct shash_desc *desc, const u8 *data,
+			      unsigned int length, u8 *out)
+{
+	struct chksum_ctx *mctx = crypto_shash_ctx(desc->tfm);
+
+	return __chksum_finup_arch(&mctx->key, data, length, out);
+}
+
 static int crc32c_cra_init(struct crypto_tfm *tfm)
 {
 	struct chksum_ctx *mctx = crypto_tfm_ctx(tfm);
@@ -127,35 +159,53 @@ static int crc32c_cra_init(struct crypto_tfm *tfm)
 	return 0;
 }
 
-static struct shash_alg alg = {
-	.digestsize		=	CHKSUM_DIGEST_SIZE,
-	.setkey			=	chksum_setkey,
-	.init		=	chksum_init,
-	.update		=	chksum_update,
-	.final		=	chksum_final,
-	.finup		=	chksum_finup,
-	.digest		=	chksum_digest,
-	.descsize		=	sizeof(struct chksum_desc_ctx),
-	.base			=	{
-		.cra_name		=	"crc32c",
-		.cra_driver_name	=	"crc32c-generic",
-		.cra_priority		=	100,
-		.cra_flags		=	CRYPTO_ALG_OPTIONAL_KEY,
-		.cra_blocksize		=	CHKSUM_BLOCK_SIZE,
-		.cra_ctxsize		=	sizeof(struct chksum_ctx),
-		.cra_module		=	THIS_MODULE,
-		.cra_init		=	crc32c_cra_init,
-	}
-};
+static struct shash_alg algs[] = {{
+	.digestsize		= CHKSUM_DIGEST_SIZE,
+	.setkey			= chksum_setkey,
+	.init			= chksum_init,
+	.update			= chksum_update,
+	.final			= chksum_final,
+	.finup			= chksum_finup,
+	.digest			= chksum_digest,
+	.descsize		= sizeof(struct chksum_desc_ctx),
+
+	.base.cra_name		= "crc32c",
+	.base.cra_driver_name	= "crc32c-generic",
+	.base.cra_priority	= 100,
+	.base.cra_flags		= CRYPTO_ALG_OPTIONAL_KEY,
+	.base.cra_blocksize	= CHKSUM_BLOCK_SIZE,
+	.base.cra_ctxsize	= sizeof(struct chksum_ctx),
+	.base.cra_module	= THIS_MODULE,
+	.base.cra_init		= crc32c_cra_init,
+}, {
+	.digestsize		= CHKSUM_DIGEST_SIZE,
+	.setkey			= chksum_setkey,
+	.init			= chksum_init,
+	.update			= chksum_update_arch,
+	.final			= chksum_final,
+	.finup			= chksum_finup_arch,
+	.digest			= chksum_digest_arch,
+	.descsize		= sizeof(struct chksum_desc_ctx),
+
+	.base.cra_name		= "crc32c",
+	.base.cra_driver_name	= "crc32c-" __stringify(ARCH),
+	.base.cra_priority	= 150,
+	.base.cra_flags		= CRYPTO_ALG_OPTIONAL_KEY,
+	.base.cra_blocksize	= CHKSUM_BLOCK_SIZE,
+	.base.cra_ctxsize	= sizeof(struct chksum_ctx),
+	.base.cra_module	= THIS_MODULE,
+	.base.cra_init		= crc32c_cra_init,
+}};
 
 static int __init crc32c_mod_init(void)
 {
-	return crypto_register_shash(&alg);
+	/* register the arch flavor only if it differs from the generic one */
+	return crypto_register_shashes(algs, 1 + (&__crc32c_le != &__crc32c_le_base));
 }
 
 static void __exit crc32c_mod_fini(void)
 {
-	crypto_unregister_shash(&alg);
+	crypto_unregister_shashes(algs, 1 + (&__crc32c_le != &__crc32c_le_base));
 }
 
 subsys_initcall(crc32c_mod_init);
diff --git a/lib/crc32.c b/lib/crc32.c
index a54ba87b7073..ff587fee3893 100644
--- a/lib/crc32.c
+++ b/lib/crc32.c
@@ -208,6 +208,8 @@ u32 __pure crc32_le_base(u32, unsigned char const *, size_t) __alias(crc32_le);
 EXPORT_SYMBOL(crc32_le_base);
 
 u32 __pure __crc32c_le_base(u32, unsigned char const *, size_t) __alias(__crc32c_le);
+EXPORT_SYMBOL(__crc32c_le_base);
+
 u32 __pure crc32_be_base(u32, unsigned char const *, size_t) __alias(crc32_be);
 
 /*
-- 
2.47.0.rc1.288.g06298d1525-goog