[CRYPTO] salsa20_i586: Salsa20 stream cipher algorithm (i586 version)

This patch contains the salsa20-i586 implementation. The original
assembly code came from
<http://cr.yp.to/snuffle/salsa20/x86-pm/salsa20.s>. I have reformatted
it (added indents) so that it matches the other algorithms in
arch/x86/crypto.

Signed-off-by: Tan Swee Heng <thesweeheng@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

arch/x86/crypto/Makefile

@@ -4,12 +4,14 @@
 
 obj-$(CONFIG_CRYPTO_AES_586) += aes-i586.o
 obj-$(CONFIG_CRYPTO_TWOFISH_586) += twofish-i586.o
+obj-$(CONFIG_CRYPTO_SALSA20_586) += salsa20-i586.o
 
 obj-$(CONFIG_CRYPTO_AES_X86_64) += aes-x86_64.o
 obj-$(CONFIG_CRYPTO_TWOFISH_X86_64) += twofish-x86_64.o
 
 aes-i586-y := aes-i586-asm_32.o aes_glue.o
 twofish-i586-y := twofish-i586-asm_32.o twofish_32.o
+salsa20-i586-y := salsa20-i586-asm_32.o salsa20_glue.o
 
 aes-x86_64-y := aes-x86_64-asm_64.o aes_glue.o
 twofish-x86_64-y := twofish-x86_64-asm_64.o twofish_64.o

arch/x86/crypto/salsa20_glue.c

@@ -0,0 +1,127 @@
+/*
+ * Glue code for optimized assembly version of  Salsa20.
+ *
+ * Copyright (c) 2007 Tan Swee Heng <thesweeheng@gmail.com>
+ *
+ * The assembly codes are public domain assembly codes written by Daniel. J.
+ * Bernstein <djb@cr.yp.to>. The codes are modified to include indentation
+ * and to remove extraneous comments and functions that are not needed.
+ * - i586 version, renamed as salsa20-i586-asm_32.S
+ *   available from <http://cr.yp.to/snuffle/salsa20/x86-pm/salsa20.s>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ *
+ */
+
+#include <crypto/algapi.h>
+#include <linux/module.h>
+#include <linux/crypto.h>
+
+#define SALSA20_IV_SIZE        8U
+#define SALSA20_MIN_KEY_SIZE  16U
+#define SALSA20_MAX_KEY_SIZE  32U
+
+// use the ECRYPT_* function names
+#define salsa20_keysetup        ECRYPT_keysetup
+#define salsa20_ivsetup         ECRYPT_ivsetup
+#define salsa20_encrypt_bytes   ECRYPT_encrypt_bytes
+
+struct salsa20_ctx
+{
+	u32 input[16];
+};
+
+asmlinkage void salsa20_keysetup(struct salsa20_ctx *ctx, const u8 *k,
+				 u32 keysize, u32 ivsize);
+asmlinkage void salsa20_ivsetup(struct salsa20_ctx *ctx, const u8 *iv);
+asmlinkage void salsa20_encrypt_bytes(struct salsa20_ctx *ctx,
+				      const u8 *src, u8 *dst, u32 bytes);
+
+static int setkey(struct crypto_tfm *tfm, const u8 *key,
+		  unsigned int keysize)
+{
+	struct salsa20_ctx *ctx = crypto_tfm_ctx(tfm);
+	salsa20_keysetup(ctx, key, keysize*8, SALSA20_IV_SIZE*8);
+	return 0;
+}
+
+static int encrypt(struct blkcipher_desc *desc,
+		   struct scatterlist *dst, struct scatterlist *src,
+		   unsigned int nbytes)
+{
+	struct blkcipher_walk walk;
+	struct crypto_blkcipher *tfm = desc->tfm;
+	struct salsa20_ctx *ctx = crypto_blkcipher_ctx(tfm);
+	int err;
+
+	blkcipher_walk_init(&walk, dst, src, nbytes);
+	err = blkcipher_walk_virt_block(desc, &walk, 64);
+
+	salsa20_ivsetup(ctx, walk.iv);
+
+	if (likely(walk.nbytes == nbytes))
+	{
+		salsa20_encrypt_bytes(ctx, walk.src.virt.addr,
+				      walk.dst.virt.addr, nbytes);
+		return blkcipher_walk_done(desc, &walk, 0);
+	}
+
+	while (walk.nbytes >= 64) {
+		salsa20_encrypt_bytes(ctx, walk.src.virt.addr,
+				      walk.dst.virt.addr,
+				      walk.nbytes - (walk.nbytes % 64));
+		err = blkcipher_walk_done(desc, &walk, walk.nbytes % 64);
+	}
+
+	if (walk.nbytes) {
+		salsa20_encrypt_bytes(ctx, walk.src.virt.addr,
+				      walk.dst.virt.addr, walk.nbytes);
+		err = blkcipher_walk_done(desc, &walk, 0);
+	}
+
+	return err;
+}
+
+static struct crypto_alg alg = {
+	.cra_name           =   "salsa20",
+	.cra_driver_name    =   "salsa20-asm",
+	.cra_priority       =   200,
+	.cra_flags          =   CRYPTO_ALG_TYPE_BLKCIPHER,
+	.cra_type           =   &crypto_blkcipher_type,
+	.cra_blocksize      =   1,
+	.cra_ctxsize        =   sizeof(struct salsa20_ctx),
+	.cra_alignmask      =	3,
+	.cra_module         =   THIS_MODULE,
+	.cra_list           =   LIST_HEAD_INIT(alg.cra_list),
+	.cra_u              =   {
+		.blkcipher = {
+			.setkey         =   setkey,
+			.encrypt        =   encrypt,
+			.decrypt        =   encrypt,
+			.min_keysize    =   SALSA20_MIN_KEY_SIZE,
+			.max_keysize    =   SALSA20_MAX_KEY_SIZE,
+			.ivsize         =   SALSA20_IV_SIZE,
+		}
+	}
+};
+
+static int __init init(void)
+{
+	return crypto_register_alg(&alg);
+}
+
+static void __exit fini(void)
+{
+	crypto_unregister_alg(&alg);
+}
+
+module_init(init);
+module_exit(fini);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION ("Salsa20 stream cipher algorithm (optimized assembly version)");
+MODULE_ALIAS("salsa20");
+MODULE_ALIAS("salsa20-asm");

crypto/Kconfig

@@ -489,6 +489,21 @@ config CRYPTO_SALSA20
 	  The Salsa20 stream cipher algorithm is designed by Daniel J.
 	  Bernstein <djb@cr.yp.to>. See <http://cr.yp.to/snuffle.html>
 
+config CRYPTO_SALSA20_586
+	tristate "Salsa20 stream cipher algorithm (i586) (EXPERIMENTAL)"
+	depends on (X86 || UML_X86) && !64BIT
+	depends on EXPERIMENTAL
+	select CRYPTO_BLKCIPHER
+	select CRYPTO_SALSA20
+	help
+	  Salsa20 stream cipher algorithm.
+
+	  Salsa20 is a stream cipher submitted to eSTREAM, the ECRYPT
+	  Stream Cipher Project. See <http://www.ecrypt.eu.org/stream/>
+
+	  The Salsa20 stream cipher algorithm is designed by Daniel J.
+	  Bernstein <djb@cr.yp.to>. See <http://cr.yp.to/snuffle.html>
+
 config CRYPTO_DEFLATE
 	tristate "Deflate compression algorithm"
 	select CRYPTO_ALGAPI