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Subject[RFC PATCH 6/9] crypto: arm/chacha20 - refactor to allow varying number of rounds
Date
From: Eric Biggers <ebiggers@google.com>

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

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
arch/arm/crypto/Makefile | 4 +-
...hacha20-neon-core.S => chacha-neon-core.S} | 51 +++++++++--------
...hacha20-neon-glue.c => chacha-neon-glue.c} | 56 ++++++++++---------
3 files changed, 59 insertions(+), 52 deletions(-)
rename arch/arm/crypto/{chacha20-neon-core.S => chacha-neon-core.S} (93%)
rename arch/arm/crypto/{chacha20-neon-glue.c => chacha-neon-glue.c} (73%)

diff --git a/arch/arm/crypto/Makefile b/arch/arm/crypto/Makefile
index 8de542c48ade..6f58a24faa4a 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
obj-$(CONFIG_CRYPTO_SPECK_NEON) += speck-neon.o

ce-obj-$(CONFIG_CRYPTO_AES_ARM_CE) += aes-arm-ce.o
@@ -53,7 +53,7 @@ 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
speck-neon-y := speck-neon-core.o speck-neon-glue.o

ifdef REGENERATE_ARM_CRYPTO
diff --git a/arch/arm/crypto/chacha20-neon-core.S b/arch/arm/crypto/chacha-neon-core.S
similarity index 93%
rename from arch/arm/crypto/chacha20-neon-core.S
rename to arch/arm/crypto/chacha-neon-core.S
index 8e63208cc025..3b38d3cac522 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>
*
@@ -25,18 +25,18 @@
.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 operation on four words in parallel, but
* requires shuffling to rearrange the words after each round.
*
+ * The round count is given in r3.
+ *
* Clobbers: r3, q4
*/
.macro _chacha_permute

- mov r3, #10
-
.Ldoubleround_\@:
// x0 += x1, x3 = rotl32(x3 ^ x0, 16)
vadd.i32 q0, q0, q1
@@ -98,14 +98,15 @@
// x3 = shuffle32(x3, MASK(0, 3, 2, 1))
vext.8 q3, q3, q3, #4

- subs r3, r3, #1
+ subs r3, r3, #2
bne .Ldoubleround_\@
.endm

-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

// x0..3 = s0..3
add ip, r0, #0x20
@@ -117,7 +118,7 @@ ENTRY(chacha20_block_xor_neon)
vmov q10, q2
vmov q11, q3

- _chacha20_permute
+ _chacha_permute

add ip, r2, #0x20
vld1.8 {q4-q5}, [r2]
@@ -144,37 +145,41 @@ ENTRY(chacha20_block_xor_neon)
vst1.8 {q2-q3}, [ip]

bx lr
-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

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

- _chacha20_permute
+ mov r3, r2
+ _chacha_permute

vst1.8 {q0}, [r1]!
vst1.8 {q3}, [r1]

bx lr
-ENDPROC(hchacha20_block_neon)
+ENDPROC(hchacha_block_neon)

.align 5
-ENTRY(chacha20_4block_xor_neon)
+ENTRY(chacha_4block_xor_neon)
push {r4-r6, lr}
mov ip, sp // preserve the stack pointer
- sub r3, sp, #0x20 // allocate a 32 byte buffer
- bic r3, r3, #0x1f // aligned to 32 bytes
- mov sp, r3
+ sub r4, sp, #0x20 // allocate a 32 byte buffer
+ bic r4, r4, #0x1f // aligned to 32 bytes
+ mov sp, r4
+

// 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. For final XORing step we transpose the
@@ -183,14 +188,14 @@ ENTRY(chacha20_4block_xor_neon)
//

// x0..15[0-3] = s0..3[0..3]
- add r3, r0, #0x20
+ add r4, r0, #0x20
vld1.32 {q0-q1}, [r0]
- vld1.32 {q2-q3}, [r3]
+ vld1.32 {q2-q3}, [r4]

- adr r3, CTRINC
+ adr r4, CTRINC
vdup.32 q15, d7[1]
vdup.32 q14, d7[0]
- vld1.32 {q11}, [r3, :128]
+ vld1.32 {q11}, [r4, :128]
vdup.32 q13, d6[1]
vdup.32 q12, d6[0]
vadd.i32 q12, q12, q11 // x12 += counter values 0-3
@@ -207,8 +212,6 @@ ENTRY(chacha20_4block_xor_neon)
vdup.32 q1, d0[1]
vdup.32 q0, d0[0]

- mov r3, #10
-
.Ldoubleround4:
// x0 += x4, x12 = rotl32(x12 ^ x0, 16)
// x1 += x5, x13 = rotl32(x13 ^ x1, 16)
@@ -400,7 +403,7 @@ ENTRY(chacha20_4block_xor_neon)
vsri.u32 q5, q8, #25
vsri.u32 q6, q9, #25

- subs r3, r3, #1
+ subs r3, r3, #2
beq 0f

vld1.32 {q8-q9}, [sp, :256]
@@ -537,7 +540,7 @@ ENTRY(chacha20_4block_xor_neon)

mov sp, ip
pop {r4-r6, pc}
-ENDPROC(chacha20_4block_xor_neon)
+ENDPROC(chacha_4block_xor_neon)

.align 4
CTRINC: .word 0, 1, 2, 3
diff --git a/arch/arm/crypto/chacha20-neon-glue.c b/arch/arm/crypto/chacha-neon-glue.c
similarity index 73%
rename from arch/arm/crypto/chacha20-neon-glue.c
rename to arch/arm/crypto/chacha-neon-glue.c
index becc7990b1d3..b236af4889c6 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];
@@ -75,15 +77,15 @@ 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);
@@ -93,12 +95,12 @@ static int chacha20_neon(struct skcipher_request *req)
return crypto_chacha_crypt(req);

kernel_neon_begin();
- err = chacha20_neon_stream_xor(req, ctx, req->iv);
+ err = chacha_neon_stream_xor(req, ctx, req->iv);
kernel_neon_end();
return err;
}

-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);
@@ -114,10 +116,11 @@ static int xchacha20_neon(struct skcipher_request *req)

kernel_neon_begin();

- hchacha20_block_neon(state, subctx.key);
+ hchacha_block_neon(state, subctx.key, ctx->nrounds);
+ subctx.nrounds = ctx->nrounds;
memcpy(&real_iv[0], req->iv + 24, 8);
memcpy(&real_iv[8], req->iv + 16, 8);
- err = chacha20_neon_stream_xor(req, &subctx, real_iv);
+ err = chacha_neon_stream_xor(req, &subctx, real_iv);

kernel_neon_end();

@@ -139,8 +142,8 @@ 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 +158,12 @@ 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;
@@ -168,14 +171,15 @@ 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");
--
2.18.0.597.ga71716f1ad-goog
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