[PATCH v4 08/14] crypto: arm/chacha20 - refactor to allow varying number of rounds

Eric Biggers
2018-11-17T01:28:58Z

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

Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
arch/arm/crypto/Makefile | 4 +-
...hacha20-neon-core.S => chacha-neon-core.S} | 44 ++++++++-------
...hacha20-neon-glue.c => chacha-neon-glue.c} | 56 ++++++++++---------
3 files changed, 56 insertions(+), 48 deletions(-)
rename arch/arm/crypto/{chacha20-neon-core.S => chacha-neon-core.S} (94%)
rename arch/arm/crypto/{chacha20-neon-glue.c => chacha-neon-glue.c} (72%)

diff --git a/arch/arm/crypto/Makefile b/arch/arm/crypto/Makefile
index bd5bceef0605..005482ff9504 100644
--- a/arch/arm/crypto/Makefile
+++ b/arch/arm/crypto/Makefile
@@ -9,7 +9,7 @@ obj-$(CONFIG_CRYPTO_SHA1_ARM) += sha1-arm.o
obj-$(CONFIG_CRYPTO_SHA1_ARM_NEON) += sha1-arm-neon.o
obj-$(CONFIG_CRYPTO_SHA256_ARM) += sha256-arm.o
obj-$(CONFIG_CRYPTO_SHA512_ARM) += sha512-arm.o
-obj-$(CONFIG_CRYPTO_CHACHA20_NEON) += chacha20-neon.o
+obj-$(CONFIG_CRYPTO_CHACHA20_NEON) += chacha-neon.o

ce-obj-$(CONFIG_CRYPTO_AES_ARM_CE) += aes-arm-ce.o
ce-obj-$(CONFIG_CRYPTO_SHA1_ARM_CE) += sha1-arm-ce.o
@@ -52,7 +52,7 @@ aes-arm-ce-y := aes-ce-core.o aes-ce-glue.o
ghash-arm-ce-y := ghash-ce-core.o ghash-ce-glue.o
crct10dif-arm-ce-y := crct10dif-ce-core.o crct10dif-ce-glue.o
crc32-arm-ce-y:= crc32-ce-core.o crc32-ce-glue.o
-chacha20-neon-y := chacha20-neon-core.o chacha20-neon-glue.o
+chacha-neon-y := chacha-neon-core.o chacha-neon-glue.o

ifdef REGENERATE_ARM_CRYPTO
quiet_cmd_perl = PERL $@
diff --git a/arch/arm/crypto/chacha20-neon-core.S b/arch/arm/crypto/chacha-neon-core.S
similarity index 94%
rename from arch/arm/crypto/chacha20-neon-core.S
rename to arch/arm/crypto/chacha-neon-core.S
index 2335e5055d2b..eb22926d4912 100644
--- a/arch/arm/crypto/chacha20-neon-core.S
+++ b/arch/arm/crypto/chacha-neon-core.S
@@ -1,5 +1,5 @@
/*
- * ChaCha20 256-bit cipher algorithm, RFC7539, ARM NEON functions
+ * ChaCha/XChaCha NEON helper functions
*
* Copyright (C) 2016 Linaro, Ltd. <ard.biesheuvel@linaro.org>
*
@@ -27,9 +27,9 @@
* (d) vtbl.8 + vtbl.8 (multiple of 8 bits rotations only,
* needs index vector)
*
- * ChaCha20 has 16, 12, 8, and 7-bit rotations. For the 12 and 7-bit
- * rotations, the only choices are (a) and (b). We use (a) since it takes
- * two-thirds the cycles of (b) on both Cortex-A7 and Cortex-A53.
+ * ChaCha has 16, 12, 8, and 7-bit rotations. For the 12 and 7-bit rotations,
+ * the only choices are (a) and (b). We use (a) since it takes two-thirds the
+ * cycles of (b) on both Cortex-A7 and Cortex-A53.
*
* For the 16-bit rotation, we use vrev32.16 since it's consistently fastest
* and doesn't need a temporary register.
@@ -53,18 +53,19 @@
.align 5

/*
- * 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 q0-q3. It performs matrix operations on four words in parallel,
* but requires shuffling to rearrange the words after each round.
*
+ * The round count is given in r3.
+ *
* Clobbers: r3, ip, q4-q5
*/
-chacha20_permute:
+chacha_permute:

adr ip, .Lrol8_table
- mov r3, #10
vld1.8 {d10}, [ip, :64]

.Ldoubleround:
@@ -128,16 +129,17 @@ chacha20_permute:
// x3 = shuffle32(x3, MASK(0, 3, 2, 1))
vext.8 q3, q3, q3, #4

- subs r3, r3, #1
+ subs r3, r3, #2
bne .Ldoubleround

bx lr
-ENDPROC(chacha20_permute)
+ENDPROC(chacha_permute)

-ENTRY(chacha20_block_xor_neon)
+ENTRY(chacha_block_xor_neon)
// r0: Input state matrix, s
// r1: 1 data block output, o
// r2: 1 data block input, i
+ // r3: nrounds
push {lr}

// x0..3 = s0..3
@@ -150,7 +152,7 @@ ENTRY(chacha20_block_xor_neon)
vmov q10, q2
vmov q11, q3

- bl chacha20_permute
+ bl chacha_permute

add ip, r2, #0x20
vld1.8 {q4-q5}, [r2]
@@ -177,30 +179,32 @@ ENTRY(chacha20_block_xor_neon)
vst1.8 {q2-q3}, [ip]

pop {pc}
-ENDPROC(chacha20_block_xor_neon)
+ENDPROC(chacha_block_xor_neon)

-ENTRY(hchacha20_block_neon)
+ENTRY(hchacha_block_neon)
// r0: Input state matrix, s
// r1: output (8 32-bit words)
+ // r2: nrounds
push {lr}

vld1.32 {q0-q1}, [r0]!
vld1.32 {q2-q3}, [r0]

- bl chacha20_permute
+ mov r3, r2
+ bl chacha_permute

vst1.32 {q0}, [r1]!
vst1.32 {q3}, [r1]

pop {pc}
-ENDPROC(hchacha20_block_neon)
+ENDPROC(hchacha_block_neon)

.align 4
.Lctrinc: .word 0, 1, 2, 3
.Lrol8_table: .byte 3, 0, 1, 2, 7, 4, 5, 6

.align 5
-ENTRY(chacha20_4block_xor_neon)
+ENTRY(chacha_4block_xor_neon)
push {r4-r5}
mov r4, sp // preserve the stack pointer
sub ip, sp, #0x20 // allocate a 32 byte buffer
@@ -210,9 +214,10 @@ ENTRY(chacha20_4block_xor_neon)
// r0: Input state matrix, s
// r1: 4 data blocks output, o
// r2: 4 data blocks input, i
+ // r3: 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. The words are re-interleaved before the
@@ -245,7 +250,6 @@ ENTRY(chacha20_4block_xor_neon)
vdup.32 q0, d0[0]

adr ip, .Lrol8_table
- mov r3, #10
b 1f

.Ldoubleround4:
@@ -443,7 +447,7 @@ ENTRY(chacha20_4block_xor_neon)
vsri.u32 q5, q8, #25
vsri.u32 q6, q9, #25

- subs r3, r3, #1
+ subs r3, r3, #2
bne .Ldoubleround4

// x0..7[0-3] are in q0-q7, x10..15[0-3] are in q10-q15.
@@ -553,4 +557,4 @@ ENTRY(chacha20_4block_xor_neon)

pop {r4-r5}
bx lr
-ENDPROC(chacha20_4block_xor_neon)
+ENDPROC(chacha_4block_xor_neon)
diff --git a/arch/arm/crypto/chacha20-neon-glue.c b/arch/arm/crypto/chacha-neon-glue.c
similarity index 72%
rename from arch/arm/crypto/chacha20-neon-glue.c
rename to arch/arm/crypto/chacha-neon-glue.c
index f2d3b0f70a8d..385557d38634 100644
--- a/arch/arm/crypto/chacha20-neon-glue.c
+++ b/arch/arm/crypto/chacha-neon-glue.c
@@ -28,24 +28,26 @@
#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);
-
-static void chacha20_doneon(u32 *state, u8 *dst, const u8 *src,
- unsigned int bytes)
+asmlinkage void chacha_block_xor_neon(const u32 *state, u8 *dst, const u8 *src,
+ int nrounds);
+asmlinkage void chacha_4block_xor_neon(const u32 *state, u8 *dst, const u8 *src,
+ int nrounds);
+asmlinkage void hchacha_block_neon(const u32 *state, u32 *out, int nrounds);
+
+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) {
- chacha20_4block_xor_neon(state, dst, src);
+ chacha_4block_xor_neon(state, dst, src, nrounds);
bytes -= CHACHA_BLOCK_SIZE * 4;
src += CHACHA_BLOCK_SIZE * 4;
dst += CHACHA_BLOCK_SIZE * 4;
state[12] += 4;
}
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;
@@ -53,13 +55,13 @@ 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);
}
}

-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];
@@ -76,8 +78,8 @@ static int chacha20_neon_stream_xor(struct skcipher_request *req,
nbytes = round_down(nbytes, walk.stride);

kernel_neon_begin();
- 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);
kernel_neon_end();
err = skcipher_walk_done(&walk, walk.nbytes - nbytes);
}
@@ -85,7 +87,7 @@ static int chacha20_neon_stream_xor(struct skcipher_request *req,
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);
@@ -93,10 +95,10 @@ 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);
@@ -110,12 +112,13 @@ 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[] = {
@@ -133,8 +136,8 @@ 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",
@@ -149,12 +152,12 @@ 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_NEON))
return -ENODEV;
@@ -162,14 +165,15 @@ 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@linaro.org>");
MODULE_LICENSE("GPL v2");
MODULE_ALIAS_CRYPTO("chacha20");
--
2.19.1.1215.g8438c0b245-goog