[PATCH 0/3] crypto: x86/ghash cleanups

[PATCH 0/3] crypto: x86/ghash cleanups

[Eric Biggers]

These patches are a replacement for Peter Zijlstra's patch
"[RFC][PATCH 02/12] crypto/ghash-clmulni: Use (struct) be128"
(https://lore.kernel.org/r/20221219154118.955831880@infradead.org).

Eric Biggers (3):
  crypto: x86/ghash - fix unaligned access in ghash_setkey()
  crypto: x86/ghash - use le128 instead of u128
  crypto: x86/ghash - add comment and fix broken link

 arch/x86/crypto/ghash-clmulni-intel_asm.S  |  6 +--
 arch/x86/crypto/ghash-clmulni-intel_glue.c | 45 +++++++++++++++-------
 2 files changed, 35 insertions(+), 16 deletions(-)


base-commit: 6feb57c2fd7c787aecf2846a535248899e7b70fa
-- 
2.39.0

[PATCH 1/3] crypto: x86/ghash - fix unaligned access in ghash_setkey()

[Eric Biggers]

From: Eric Biggers <ebiggers@google.com>

The key can be unaligned, so use the unaligned memory access helpers.

Fixes: 8ceee72808d1 ("crypto: ghash-clmulni-intel - use C implementation for setkey()")
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 arch/x86/crypto/ghash-clmulni-intel_glue.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/crypto/ghash-clmulni-intel_glue.c b/arch/x86/crypto/ghash-clmulni-intel_glue.c
index 1f1a95f3dd0c..c0ab0ff4af65 100644
--- a/arch/x86/crypto/ghash-clmulni-intel_glue.c
+++ b/arch/x86/crypto/ghash-clmulni-intel_glue.c
@@ -19,6 +19,7 @@
 #include <crypto/internal/simd.h>
 #include <asm/cpu_device_id.h>
 #include <asm/simd.h>
+#include <asm/unaligned.h>
 
 #define GHASH_BLOCK_SIZE	16
 #define GHASH_DIGEST_SIZE	16
@@ -54,15 +55,14 @@ static int ghash_setkey(struct crypto_shash *tfm,
 			const u8 *key, unsigned int keylen)
 {
 	struct ghash_ctx *ctx = crypto_shash_ctx(tfm);
-	be128 *x = (be128 *)key;
 	u64 a, b;
 
 	if (keylen != GHASH_BLOCK_SIZE)
 		return -EINVAL;
 
 	/* perform multiplication by 'x' in GF(2^128) */
-	a = be64_to_cpu(x->a);
-	b = be64_to_cpu(x->b);
+	a = get_unaligned_be64(key);
+	b = get_unaligned_be64(key + 8);
 
 	ctx->shash.a = (b << 1) | (a >> 63);
 	ctx->shash.b = (a << 1) | (b >> 63);
-- 
2.39.0

[PATCH 2/3] crypto: x86/ghash - use le128 instead of u128

[Eric Biggers]

From: Eric Biggers <ebiggers@google.com>

The u128 struct type is going away, so make ghash-clmulni-intel use
le128 instead.  Note that the field names a and b swapped, as they were
backwards with u128.  (a is meant to be high-order and b low-order.)

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 arch/x86/crypto/ghash-clmulni-intel_asm.S  |  4 ++--
 arch/x86/crypto/ghash-clmulni-intel_glue.c | 12 ++++++------
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/arch/x86/crypto/ghash-clmulni-intel_asm.S b/arch/x86/crypto/ghash-clmulni-intel_asm.S
index 2bf871899920..9dfeb4d31b92 100644
--- a/arch/x86/crypto/ghash-clmulni-intel_asm.S
+++ b/arch/x86/crypto/ghash-clmulni-intel_asm.S
@@ -88,7 +88,7 @@ SYM_FUNC_START_LOCAL(__clmul_gf128mul_ble)
 	RET
 SYM_FUNC_END(__clmul_gf128mul_ble)
 
-/* void clmul_ghash_mul(char *dst, const u128 *shash) */
+/* void clmul_ghash_mul(char *dst, const le128 *shash) */
 SYM_FUNC_START(clmul_ghash_mul)
 	FRAME_BEGIN
 	movups (%rdi), DATA
@@ -104,7 +104,7 @@ SYM_FUNC_END(clmul_ghash_mul)
 
 /*
  * void clmul_ghash_update(char *dst, const char *src, unsigned int srclen,
- *			   const u128 *shash);
+ *			   const le128 *shash);
  */
 SYM_FUNC_START(clmul_ghash_update)
 	FRAME_BEGIN
diff --git a/arch/x86/crypto/ghash-clmulni-intel_glue.c b/arch/x86/crypto/ghash-clmulni-intel_glue.c
index c0ab0ff4af65..9453b094bb3b 100644
--- a/arch/x86/crypto/ghash-clmulni-intel_glue.c
+++ b/arch/x86/crypto/ghash-clmulni-intel_glue.c
@@ -24,17 +24,17 @@
 #define GHASH_BLOCK_SIZE	16
 #define GHASH_DIGEST_SIZE	16
 
-void clmul_ghash_mul(char *dst, const u128 *shash);
+void clmul_ghash_mul(char *dst, const le128 *shash);
 
 void clmul_ghash_update(char *dst, const char *src, unsigned int srclen,
-			const u128 *shash);
+			const le128 *shash);
 
 struct ghash_async_ctx {
 	struct cryptd_ahash *cryptd_tfm;
 };
 
 struct ghash_ctx {
-	u128 shash;
+	le128 shash;
 };
 
 struct ghash_desc_ctx {
@@ -64,11 +64,11 @@ static int ghash_setkey(struct crypto_shash *tfm,
 	a = get_unaligned_be64(key);
 	b = get_unaligned_be64(key + 8);
 
-	ctx->shash.a = (b << 1) | (a >> 63);
-	ctx->shash.b = (a << 1) | (b >> 63);
+	ctx->shash.a = cpu_to_le64((a << 1) | (b >> 63));
+	ctx->shash.b = cpu_to_le64((b << 1) | (a >> 63));
 
 	if (a >> 63)
-		ctx->shash.b ^= ((u64)0xc2) << 56;
+		ctx->shash.a ^= cpu_to_le64((u64)0xc2 << 56);
 
 	return 0;
 }
-- 
2.39.0

[PATCH 3/3] crypto: x86/ghash - add comment and fix broken link

[Eric Biggers]

From: Eric Biggers <ebiggers@google.com>

Add a comment that explains what ghash_setkey() is doing, as it's hard
to understand otherwise.  Also fix a broken hyperlink.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 arch/x86/crypto/ghash-clmulni-intel_asm.S  |  2 +-
 arch/x86/crypto/ghash-clmulni-intel_glue.c | 27 ++++++++++++++++++----
 2 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/arch/x86/crypto/ghash-clmulni-intel_asm.S b/arch/x86/crypto/ghash-clmulni-intel_asm.S
index 9dfeb4d31b92..257ed9446f3e 100644
--- a/arch/x86/crypto/ghash-clmulni-intel_asm.S
+++ b/arch/x86/crypto/ghash-clmulni-intel_asm.S
@@ -4,7 +4,7 @@
  * instructions. This file contains accelerated part of ghash
  * implementation. More information about PCLMULQDQ can be found at:
  *
- * http://software.intel.com/en-us/articles/carry-less-multiplication-and-its-usage-for-computing-the-gcm-mode/
+ * https://www.intel.com/content/dam/develop/external/us/en/documents/clmul-wp-rev-2-02-2014-04-20.pdf
  *
  * Copyright (c) 2009 Intel Corp.
  *   Author: Huang Ying <ying.huang@intel.com>
diff --git a/arch/x86/crypto/ghash-clmulni-intel_glue.c b/arch/x86/crypto/ghash-clmulni-intel_glue.c
index 9453b094bb3b..700ecaee9a08 100644
--- a/arch/x86/crypto/ghash-clmulni-intel_glue.c
+++ b/arch/x86/crypto/ghash-clmulni-intel_glue.c
@@ -60,16 +60,35 @@ static int ghash_setkey(struct crypto_shash *tfm,
 	if (keylen != GHASH_BLOCK_SIZE)
 		return -EINVAL;
 
-	/* perform multiplication by 'x' in GF(2^128) */
+	/*
+	 * GHASH maps bits to polynomial coefficients backwards, which makes it
+	 * hard to implement.  But it can be shown that the GHASH multiplication
+	 *
+	 *	D * K (mod x^128 + x^7 + x^2 + x + 1)
+	 *
+	 * (where D is a data block and K is the key) is equivalent to:
+	 *
+	 *	bitreflect(D) * bitreflect(K) * x^(-127)
+	 *		(mod x^128 + x^127 + x^126 + x^121 + 1)
+	 *
+	 * So, the code below precomputes:
+	 *
+	 *	bitreflect(K) * x^(-127) (mod x^128 + x^127 + x^126 + x^121 + 1)
+	 *
+	 * ... but in Montgomery form (so that Montgomery multiplication can be
+	 * used), i.e. with an extra x^128 factor, which means actually:
+	 *
+	 *	bitreflect(K) * x (mod x^128 + x^127 + x^126 + x^121 + 1)
+	 *
+	 * The within-a-byte part of bitreflect() cancels out GHASH's built-in
+	 * reflection, and thus bitreflect() is actually a byteswap.
+	 */
 	a = get_unaligned_be64(key);
 	b = get_unaligned_be64(key + 8);
-
 	ctx->shash.a = cpu_to_le64((a << 1) | (b >> 63));
 	ctx->shash.b = cpu_to_le64((b << 1) | (a >> 63));
-
 	if (a >> 63)
 		ctx->shash.a ^= cpu_to_le64((u64)0xc2 << 56);
-
 	return 0;
 }
 
-- 
2.39.0

Re: [PATCH 3/3] crypto: x86/ghash - add comment and fix broken link

[Peter Zijlstra]

On Mon, Dec 19, 2022 at 09:40:42PM -0800, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> Add a comment that explains what ghash_setkey() is doing, as it's hard
> to understand otherwise.  Also fix a broken hyperlink.
> 
> Signed-off-by: Eric Biggers <ebiggers@google.com>
> ---
>  arch/x86/crypto/ghash-clmulni-intel_asm.S  |  2 +-
>  arch/x86/crypto/ghash-clmulni-intel_glue.c | 27 ++++++++++++++++++----
>  2 files changed, 24 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/crypto/ghash-clmulni-intel_asm.S b/arch/x86/crypto/ghash-clmulni-intel_asm.S
> index 9dfeb4d31b92..257ed9446f3e 100644
> --- a/arch/x86/crypto/ghash-clmulni-intel_asm.S
> +++ b/arch/x86/crypto/ghash-clmulni-intel_asm.S
> @@ -4,7 +4,7 @@
>   * instructions. This file contains accelerated part of ghash
>   * implementation. More information about PCLMULQDQ can be found at:
>   *
> - * http://software.intel.com/en-us/articles/carry-less-multiplication-and-its-usage-for-computing-the-gcm-mode/
> + * https://www.intel.com/content/dam/develop/external/us/en/documents/clmul-wp-rev-2-02-2014-04-20.pdf

Since these things have a habbit if changing, we tend to prefer to host
a copy on kernel.org somewhere (used to be bugzilla, but perhaps there's
a better places these days).

>   *
>   * Copyright (c) 2009 Intel Corp.
>   *   Author: Huang Ying <ying.huang@intel.com>
> diff --git a/arch/x86/crypto/ghash-clmulni-intel_glue.c b/arch/x86/crypto/ghash-clmulni-intel_glue.c
> index 9453b094bb3b..700ecaee9a08 100644
> --- a/arch/x86/crypto/ghash-clmulni-intel_glue.c
> +++ b/arch/x86/crypto/ghash-clmulni-intel_glue.c
> @@ -60,16 +60,35 @@ static int ghash_setkey(struct crypto_shash *tfm,
>  	if (keylen != GHASH_BLOCK_SIZE)
>  		return -EINVAL;
>  
> -	/* perform multiplication by 'x' in GF(2^128) */
> +	/*
> +	 * GHASH maps bits to polynomial coefficients backwards, which makes it
> +	 * hard to implement.  But it can be shown that the GHASH multiplication
> +	 *
> +	 *	D * K (mod x^128 + x^7 + x^2 + x + 1)
> +	 *
> +	 * (where D is a data block and K is the key) is equivalent to:
> +	 *
> +	 *	bitreflect(D) * bitreflect(K) * x^(-127)
> +	 *		(mod x^128 + x^127 + x^126 + x^121 + 1)
> +	 *
> +	 * So, the code below precomputes:
> +	 *
> +	 *	bitreflect(K) * x^(-127) (mod x^128 + x^127 + x^126 + x^121 + 1)
> +	 *
> +	 * ... but in Montgomery form (so that Montgomery multiplication can be
> +	 * used), i.e. with an extra x^128 factor, which means actually:
> +	 *
> +	 *	bitreflect(K) * x (mod x^128 + x^127 + x^126 + x^121 + 1)
> +	 *
> +	 * The within-a-byte part of bitreflect() cancels out GHASH's built-in
> +	 * reflection, and thus bitreflect() is actually a byteswap.
> +	 */

Whee, thanks, that was indeed entirely non-obvious.

Re: [PATCH 3/3] crypto: x86/ghash - add comment and fix broken link

[Herbert Xu]

On Tue, Dec 20, 2022 at 11:09:16AM +0100, Peter Zijlstra wrote:
> On Mon, Dec 19, 2022 at 09:40:42PM -0800, Eric Biggers wrote:
>
> > - * http://software.intel.com/en-us/articles/carry-less-multiplication-and-its-usage-for-computing-the-gcm-mode/
> > + * https://www.intel.com/content/dam/develop/external/us/en/documents/clmul-wp-rev-2-02-2014-04-20.pdf
> 
> Since these things have a habbit if changing, we tend to prefer to host
> a copy on kernel.org somewhere (used to be bugzilla, but perhaps there's
> a better places these days).

Alternatively just save a copy at web.archive.org when you submit
the patch and use that link.  In fact it seems that the original
link is still available via web.archive.org (sans pictures).

Cheers,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: [PATCH 0/3] crypto: x86/ghash cleanups

[Peter Zijlstra]

On Mon, Dec 19, 2022 at 09:40:39PM -0800, Eric Biggers wrote:
> These patches are a replacement for Peter Zijlstra's patch
> "[RFC][PATCH 02/12] crypto/ghash-clmulni: Use (struct) be128"
> (https://lore.kernel.org/r/20221219154118.955831880@infradead.org).
> 
> Eric Biggers (3):
>   crypto: x86/ghash - fix unaligned access in ghash_setkey()
>   crypto: x86/ghash - use le128 instead of u128
>   crypto: x86/ghash - add comment and fix broken link
> 
>  arch/x86/crypto/ghash-clmulni-intel_asm.S  |  6 +--
>  arch/x86/crypto/ghash-clmulni-intel_glue.c | 45 +++++++++++++++-------
>  2 files changed, 35 insertions(+), 16 deletions(-)

Thanks! Lemme go rebase on top of this.

Re: [PATCH 0/3] crypto: x86/ghash cleanups

[Herbert Xu]

On Mon, Dec 19, 2022 at 09:40:39PM -0800, Eric Biggers wrote:
> These patches are a replacement for Peter Zijlstra's patch
> "[RFC][PATCH 02/12] crypto/ghash-clmulni: Use (struct) be128"
> (https://lore.kernel.org/r/20221219154118.955831880@infradead.org).
> 
> Eric Biggers (3):
>   crypto: x86/ghash - fix unaligned access in ghash_setkey()
>   crypto: x86/ghash - use le128 instead of u128
>   crypto: x86/ghash - add comment and fix broken link
> 
>  arch/x86/crypto/ghash-clmulni-intel_asm.S  |  6 +--
>  arch/x86/crypto/ghash-clmulni-intel_glue.c | 45 +++++++++++++++-------
>  2 files changed, 35 insertions(+), 16 deletions(-)
> 
> 
> base-commit: 6feb57c2fd7c787aecf2846a535248899e7b70fa
> -- 
> 2.39.0

All applied.  Thanks.
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt