[PATCH v2 3/4] crypto: arm64/chacha20 - refactor to allow varying number of rounds

From: Eric Biggers
Date: Mon Dec 03 2018 - 22:56:23 EST

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From: Eric Biggers <ebiggers@xxxxxxxxxx>

In preparation for adding XChaCha12 support, rename/refactor the ARM64
NEON implementation of ChaCha20 to support different numbers of rounds.

Reviewed-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
---
arch/arm64/crypto/Makefile | 4 +-
...hacha20-neon-core.S => chacha-neon-core.S} | 45 ++++++++-------
...hacha20-neon-glue.c => chacha-neon-glue.c} | 57 ++++++++++---------
3 files changed, 57 insertions(+), 49 deletions(-)
rename arch/arm64/crypto/{chacha20-neon-core.S => chacha-neon-core.S} (94%)
rename arch/arm64/crypto/{chacha20-neon-glue.c => chacha-neon-glue.c} (71%)

diff --git a/arch/arm64/crypto/Makefile b/arch/arm64/crypto/Makefile
index 125dbb10a93e..a4ffd9fe3265 100644
--- a/arch/arm64/crypto/Makefile
+++ b/arch/arm64/crypto/Makefile
@@ -50,8 +50,8 @@ sha256-arm64-y := sha256-glue.o sha256-core.o
obj-$(CONFIG_CRYPTO_SHA512_ARM64) += sha512-arm64.o
sha512-arm64-y := sha512-glue.o sha512-core.o

-obj-$(CONFIG_CRYPTO_CHACHA20_NEON) += chacha20-neon.o
-chacha20-neon-y := chacha20-neon-core.o chacha20-neon-glue.o
+obj-$(CONFIG_CRYPTO_CHACHA20_NEON) += chacha-neon.o
+chacha-neon-y := chacha-neon-core.o chacha-neon-glue.o

obj-$(CONFIG_CRYPTO_NHPOLY1305_NEON) += nhpoly1305-neon.o
nhpoly1305-neon-y := nh-neon-core.o nhpoly1305-neon-glue.o
diff --git a/arch/arm64/crypto/chacha20-neon-core.S b/arch/arm64/crypto/chacha-neon-core.S
similarity index 94%
rename from arch/arm64/crypto/chacha20-neon-core.S
rename to arch/arm64/crypto/chacha-neon-core.S
index 0571e45a1a0a..3d3a12db5204 100644
--- a/arch/arm64/crypto/chacha20-neon-core.S
+++ b/arch/arm64/crypto/chacha-neon-core.S
@@ -1,5 +1,5 @@
/*
- * ChaCha20 256-bit cipher algorithm, RFC7539, arm64 NEON functions
+ * ChaCha/XChaCha NEON helper functions
*
* Copyright (C) 2016 Linaro, Ltd. <ard.biesheuvel@xxxxxxxxxx>
*
@@ -24,17 +24,18 @@
.align 6

/*
- * chacha20_permute - permute one block
+ * chacha_permute - permute one block
*
* Permute one 64-byte block where the state matrix is stored in the four NEON
* registers v0-v3. It performs matrix operations on four words in parallel,
* but requires shuffling to rearrange the words after each round.
*
- * Clobbers: x3, x10, v4, v12
+ * The round count is given in w3.
+ *
+ * Clobbers: w3, x10, v4, v12
*/
-chacha20_permute:
+chacha_permute:

- mov x3, #10
adr x10, ROT8
ld1 {v12.4s}, [x10]

@@ -97,16 +98,17 @@ chacha20_permute:
// x3 = shuffle32(x3, MASK(0, 3, 2, 1))
ext v3.16b, v3.16b, v3.16b, #4

- subs x3, x3, #1
+ subs w3, w3, #2
b.ne .Ldoubleround

ret
-ENDPROC(chacha20_permute)
+ENDPROC(chacha_permute)

-ENTRY(chacha20_block_xor_neon)
+ENTRY(chacha_block_xor_neon)
// x0: Input state matrix, s
// x1: 1 data block output, o
// x2: 1 data block input, i
+ // w3: nrounds

stp x29, x30, [sp, #-16]!
mov x29, sp
@@ -115,7 +117,7 @@ ENTRY(chacha20_block_xor_neon)
ld1 {v0.4s-v3.4s}, [x0]
ld1 {v8.4s-v11.4s}, [x0]

- bl chacha20_permute
+ bl chacha_permute

ld1 {v4.16b-v7.16b}, [x2]

@@ -139,42 +141,45 @@ ENTRY(chacha20_block_xor_neon)

ldp x29, x30, [sp], #16
ret
-ENDPROC(chacha20_block_xor_neon)
+ENDPROC(chacha_block_xor_neon)

-ENTRY(hchacha20_block_neon)
+ENTRY(hchacha_block_neon)
// x0: Input state matrix, s
// x1: output (8 32-bit words)
+ // w2: nrounds

stp x29, x30, [sp, #-16]!
mov x29, sp

ld1 {v0.4s-v3.4s}, [x0]

- bl chacha20_permute
+ mov w3, w2
+ bl chacha_permute

st1 {v0.16b}, [x1], #16
st1 {v3.16b}, [x1]

ldp x29, x30, [sp], #16
ret
-ENDPROC(hchacha20_block_neon)
+ENDPROC(hchacha_block_neon)

.align 6
-ENTRY(chacha20_4block_xor_neon)
+ENTRY(chacha_4block_xor_neon)
// x0: Input state matrix, s
// x1: 4 data blocks output, o
// x2: 4 data blocks input, i
+ // w3: nrounds

//
- // This function encrypts four consecutive ChaCha20 blocks by loading
+ // This function encrypts four consecutive ChaCha blocks by loading
// the state matrix in NEON registers four times. The algorithm performs
// each operation on the corresponding word of each state matrix, hence
// requires no word shuffling. For final XORing step we transpose the
// matrix by interleaving 32- and then 64-bit words, which allows us to
// do XOR in NEON registers.
//
- adr x3, CTRINC // ... and ROT8
- ld1 {v30.4s-v31.4s}, [x3]
+ adr x9, CTRINC // ... and ROT8
+ ld1 {v30.4s-v31.4s}, [x9]

// x0..15[0-3] = s0..3[0..3]
mov x4, x0
@@ -186,8 +191,6 @@ ENTRY(chacha20_4block_xor_neon)
// x12 += counter values 0-3
add v12.4s, v12.4s, v30.4s

- mov x3, #10
-
.Ldoubleround4:
// x0 += x4, x12 = rotl32(x12 ^ x0, 16)
// x1 += x5, x13 = rotl32(x13 ^ x1, 16)
@@ -361,7 +364,7 @@ ENTRY(chacha20_4block_xor_neon)
sri v7.4s, v18.4s, #25
sri v4.4s, v19.4s, #25

- subs x3, x3, #1
+ subs w3, w3, #2
b.ne .Ldoubleround4

ld4r {v16.4s-v19.4s}, [x0], #16
@@ -475,7 +478,7 @@ ENTRY(chacha20_4block_xor_neon)
st1 {v28.16b-v31.16b}, [x1]

ret
-ENDPROC(chacha20_4block_xor_neon)
+ENDPROC(chacha_4block_xor_neon)

CTRINC: .word 0, 1, 2, 3
ROT8: .word 0x02010003, 0x06050407, 0x0a09080b, 0x0e0d0c0f
diff --git a/arch/arm64/crypto/chacha20-neon-glue.c b/arch/arm64/crypto/chacha-neon-glue.c
similarity index 71%
rename from arch/arm64/crypto/chacha20-neon-glue.c
rename to arch/arm64/crypto/chacha-neon-glue.c
index a5b9cbc0c4de..4d992029b912 100644
--- a/arch/arm64/crypto/chacha20-neon-glue.c
+++ b/arch/arm64/crypto/chacha-neon-glue.c
@@ -1,5 +1,6 @@
/*
- * ChaCha20 256-bit cipher algorithm, RFC7539, arm64 NEON functions
+ * ARM NEON accelerated ChaCha and XChaCha stream ciphers,
+ * including ChaCha20 (RFC7539)
*
* Copyright (C) 2016 - 2017 Linaro, Ltd. <ard.biesheuvel@xxxxxxxxxx>
*
@@ -28,18 +29,20 @@
#include <asm/neon.h>
#include <asm/simd.h>

-asmlinkage void chacha20_block_xor_neon(u32 *state, u8 *dst, const u8 *src);
-asmlinkage void chacha20_4block_xor_neon(u32 *state, u8 *dst, const u8 *src);
-asmlinkage void hchacha20_block_neon(const u32 *state, u32 *out);
+asmlinkage void chacha_block_xor_neon(u32 *state, u8 *dst, const u8 *src,
+ int nrounds);
+asmlinkage void chacha_4block_xor_neon(u32 *state, u8 *dst, const u8 *src,
+ int nrounds);
+asmlinkage void hchacha_block_neon(const u32 *state, u32 *out, int nrounds);

-static void chacha20_doneon(u32 *state, u8 *dst, const u8 *src,
- unsigned int bytes)
+static void chacha_doneon(u32 *state, u8 *dst, const u8 *src,
+ unsigned int bytes, int nrounds)
{
u8 buf[CHACHA_BLOCK_SIZE];

while (bytes >= CHACHA_BLOCK_SIZE * 4) {
kernel_neon_begin();
- chacha20_4block_xor_neon(state, dst, src);
+ chacha_4block_xor_neon(state, dst, src, nrounds);
kernel_neon_end();
bytes -= CHACHA_BLOCK_SIZE * 4;
src += CHACHA_BLOCK_SIZE * 4;
@@ -52,7 +55,7 @@ static void chacha20_doneon(u32 *state, u8 *dst, const u8 *src,

kernel_neon_begin();
while (bytes >= CHACHA_BLOCK_SIZE) {
- chacha20_block_xor_neon(state, dst, src);
+ chacha_block_xor_neon(state, dst, src, nrounds);
bytes -= CHACHA_BLOCK_SIZE;
src += CHACHA_BLOCK_SIZE;
dst += CHACHA_BLOCK_SIZE;
@@ -60,14 +63,14 @@ static void chacha20_doneon(u32 *state, u8 *dst, const u8 *src,
}
if (bytes) {
memcpy(buf, src, bytes);
- chacha20_block_xor_neon(state, buf, buf);
+ chacha_block_xor_neon(state, buf, buf, nrounds);
memcpy(dst, buf, bytes);
}
kernel_neon_end();
}

-static int chacha20_neon_stream_xor(struct skcipher_request *req,
- struct chacha_ctx *ctx, u8 *iv)
+static int chacha_neon_stream_xor(struct skcipher_request *req,
+ struct chacha_ctx *ctx, u8 *iv)
{
struct skcipher_walk walk;
u32 state[16];
@@ -83,15 +86,15 @@ static int chacha20_neon_stream_xor(struct skcipher_request *req,
if (nbytes < walk.total)
nbytes = round_down(nbytes, walk.stride);

- chacha20_doneon(state, walk.dst.virt.addr, walk.src.virt.addr,
- nbytes);
+ chacha_doneon(state, walk.dst.virt.addr, walk.src.virt.addr,
+ nbytes, ctx->nrounds);
err = skcipher_walk_done(&walk, walk.nbytes - nbytes);
}

return err;
}

-static int chacha20_neon(struct skcipher_request *req)
+static int chacha_neon(struct skcipher_request *req)
{
struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm);
@@ -99,10 +102,10 @@ static int chacha20_neon(struct skcipher_request *req)
if (req->cryptlen <= CHACHA_BLOCK_SIZE || !may_use_simd())
return crypto_chacha_crypt(req);

- return chacha20_neon_stream_xor(req, ctx, req->iv);
+ return chacha_neon_stream_xor(req, ctx, req->iv);
}

-static int xchacha20_neon(struct skcipher_request *req)
+static int xchacha_neon(struct skcipher_request *req)
{
struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm);
@@ -116,12 +119,13 @@ static int xchacha20_neon(struct skcipher_request *req)
crypto_chacha_init(state, ctx, req->iv);

kernel_neon_begin();
- hchacha20_block_neon(state, subctx.key);
+ hchacha_block_neon(state, subctx.key, ctx->nrounds);
kernel_neon_end();
+ subctx.nrounds = ctx->nrounds;

memcpy(&real_iv[0], req->iv + 24, 8);
memcpy(&real_iv[8], req->iv + 16, 8);
- return chacha20_neon_stream_xor(req, &subctx, real_iv);
+ return chacha_neon_stream_xor(req, &subctx, real_iv);
}

static struct skcipher_alg algs[] = {
@@ -139,8 +143,8 @@ static struct skcipher_alg algs[] = {
.chunksize = CHACHA_BLOCK_SIZE,
.walksize = 4 * CHACHA_BLOCK_SIZE,
.setkey = crypto_chacha20_setkey,
- .encrypt = chacha20_neon,
- .decrypt = chacha20_neon,
+ .encrypt = chacha_neon,
+ .decrypt = chacha_neon,
}, {
.base.cra_name = "xchacha20",
.base.cra_driver_name = "xchacha20-neon",
@@ -155,12 +159,12 @@ static struct skcipher_alg algs[] = {
.chunksize = CHACHA_BLOCK_SIZE,
.walksize = 4 * CHACHA_BLOCK_SIZE,
.setkey = crypto_chacha20_setkey,
- .encrypt = xchacha20_neon,
- .decrypt = xchacha20_neon,
+ .encrypt = xchacha_neon,
+ .decrypt = xchacha_neon,
}
};

-static int __init chacha20_simd_mod_init(void)
+static int __init chacha_simd_mod_init(void)
{
if (!(elf_hwcap & HWCAP_ASIMD))
return -ENODEV;
@@ -168,14 +172,15 @@ static int __init chacha20_simd_mod_init(void)
return crypto_register_skciphers(algs, ARRAY_SIZE(algs));
}

-static void __exit chacha20_simd_mod_fini(void)
+static void __exit chacha_simd_mod_fini(void)
{
crypto_unregister_skciphers(algs, ARRAY_SIZE(algs));
}

-module_init(chacha20_simd_mod_init);
-module_exit(chacha20_simd_mod_fini);
+module_init(chacha_simd_mod_init);
+module_exit(chacha_simd_mod_fini);

+MODULE_DESCRIPTION("ChaCha and XChaCha stream ciphers (NEON accelerated)");
MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>");
MODULE_LICENSE("GPL v2");
MODULE_ALIAS_CRYPTO("chacha20");
--
2.19.2

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