[CRYPTO] salsa20: Add x86-64 assembly version

This is the x86-64 version of the Salsa20 stream cipher algorithm. The
original assembly code came from
<http://cr.yp.to/snuffle/salsa20/amd64-3/salsa20.s>. It has been
reformatted for clarity.
Signed-off-by: Tan Swee Heng <thesweeheng@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

arch/x86/crypto/Makefile

@@ -8,6 +8,7 @@ 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
+obj-$(CONFIG_CRYPTO_SALSA20_X86_64) += salsa20-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
@@ -15,3 +16,4 @@ 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
+salsa20-x86_64-y := salsa20-x86_64-asm_64.o salsa20_glue.o

arch/x86/crypto/salsa20_glue.c

@@ -8,6 +8,8 @@
  * 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>
+ * - x86-64 version, renamed as salsa20-x86_64-asm_64.S
+ *   available from <http://cr.yp.to/snuffle/salsa20/amd64-3/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

crypto/Kconfig

@@ -504,6 +504,21 @@ config CRYPTO_SALSA20_586
 	  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_X86_64
+	tristate "Salsa20 stream cipher algorithm (x86_64) (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