poly1305: switch to donna

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

3 files changed, 398 insertions, 183 deletions

diff --git a/src/crypto/zinc/poly1305/poly1305-donna32.h b/src/crypto/zinc/poly1305/poly1305-donna32.h
new file mode 100644
index 0000000..1decb33
--- /dev/null
+++ b/src/crypto/zinc/poly1305/poly1305-donna32.h
@@ -0,0 +1,198 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * Copyright (C) 2015-2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ *
+ * This is based in part on Andrew Moon's poly1305-donna, which is in the
+ * public domain.
+ */
+
+struct poly1305_internal {
+	u32 h[5];
+	u32 r[5];
+};
+
+static void poly1305_init_generic(void *ctx, const u8 key[16])
+{
+	struct poly1305_internal *st = (struct poly1305_internal *)ctx;
+
+	/* r &= 0xffffffc0ffffffc0ffffffc0fffffff */
+	st->r[0] = (get_unaligned_le32(&key[0])) & 0x3ffffff;
+	st->r[1] = (get_unaligned_le32(&key[3]) >> 2) & 0x3ffff03;
+	st->r[2] = (get_unaligned_le32(&key[6]) >> 4) & 0x3ffc0ff;
+	st->r[3] = (get_unaligned_le32(&key[9]) >> 6) & 0x3f03fff;
+	st->r[4] = (get_unaligned_le32(&key[12]) >> 8) & 0x00fffff;
+
+	/* h = 0 */
+	st->h[0] = 0;
+	st->h[1] = 0;
+	st->h[2] = 0;
+	st->h[3] = 0;
+	st->h[4] = 0;
+}
+
+static void poly1305_blocks_generic(void *ctx, const u8 *input, size_t len,
+				    const u32 padbit)
+{
+	struct poly1305_internal *st = (struct poly1305_internal *)ctx;
+	const u32 hibit = padbit << 24;
+	u32 r0, r1, r2, r3, r4;
+	u32 s1, s2, s3, s4;
+	u32 h0, h1, h2, h3, h4;
+	u64 d0, d1, d2, d3, d4;
+	u32 c;
+
+	r0 = st->r[0];
+	r1 = st->r[1];
+	r2 = st->r[2];
+	r3 = st->r[3];
+	r4 = st->r[4];
+
+	s1 = r1 * 5;
+	s2 = r2 * 5;
+	s3 = r3 * 5;
+	s4 = r4 * 5;
+
+	h0 = st->h[0];
+	h1 = st->h[1];
+	h2 = st->h[2];
+	h3 = st->h[3];
+	h4 = st->h[4];
+
+	while (len >= POLY1305_BLOCK_SIZE) {
+		/* h += m[i] */
+		h0 += (get_unaligned_le32(&input[0])) & 0x3ffffff;
+		h1 += (get_unaligned_le32(&input[3]) >> 2) & 0x3ffffff;
+		h2 += (get_unaligned_le32(&input[6]) >> 4) & 0x3ffffff;
+		h3 += (get_unaligned_le32(&input[9]) >> 6) & 0x3ffffff;
+		h4 += (get_unaligned_le32(&input[12]) >> 8) | hibit;
+
+		/* h *= r */
+		d0 = ((u64)h0 * r0) + ((u64)h1 * s4) +
+		     ((u64)h2 * s3) + ((u64)h3 * s2) +
+		     ((u64)h4 * s1);
+		d1 = ((u64)h0 * r1) + ((u64)h1 * r0) +
+		     ((u64)h2 * s4) + ((u64)h3 * s3) +
+		     ((u64)h4 * s2);
+		d2 = ((u64)h0 * r2) + ((u64)h1 * r1) +
+		     ((u64)h2 * r0) + ((u64)h3 * s4) +
+		     ((u64)h4 * s3);
+		d3 = ((u64)h0 * r3) + ((u64)h1 * r2) +
+		     ((u64)h2 * r1) + ((u64)h3 * r0) +
+		     ((u64)h4 * s4);
+		d4 = ((u64)h0 * r4) + ((u64)h1 * r3) +
+		     ((u64)h2 * r2) + ((u64)h3 * r1) +
+		     ((u64)h4 * r0);
+
+		/* (partial) h %= p */
+		c = (u32)(d0 >> 26);
+		h0 = (u32)d0 & 0x3ffffff;
+		d1 += c;
+		c = (u32)(d1 >> 26);
+		h1 = (u32)d1 & 0x3ffffff;
+		d2 += c;
+		c = (u32)(d2 >> 26);
+		h2 = (u32)d2 & 0x3ffffff;
+		d3 += c;
+		c = (u32)(d3 >> 26);
+		h3 = (u32)d3 & 0x3ffffff;
+		d4 += c;
+		c = (u32)(d4 >> 26);
+		h4 = (u32)d4 & 0x3ffffff;
+		h0 += c * 5;
+		c = (h0 >> 26);
+		h0 = h0 & 0x3ffffff;
+		h1 += c;
+
+		input += POLY1305_BLOCK_SIZE;
+		len -= POLY1305_BLOCK_SIZE;
+	}
+
+	st->h[0] = h0;
+	st->h[1] = h1;
+	st->h[2] = h2;
+	st->h[3] = h3;
+	st->h[4] = h4;
+}
+
+static void poly1305_emit_generic(void *ctx, u8 mac[16], const u32 nonce[4])
+{
+	struct poly1305_internal *st = (struct poly1305_internal *)ctx;
+	u32 h0, h1, h2, h3, h4, c;
+	u32 g0, g1, g2, g3, g4;
+	u64 f;
+	u32 mask;
+
+	/* fully carry h */
+	h0 = st->h[0];
+	h1 = st->h[1];
+	h2 = st->h[2];
+	h3 = st->h[3];
+	h4 = st->h[4];
+
+	c = h1 >> 26;
+	h1 = h1 & 0x3ffffff;
+	h2 += c;
+	c = h2 >> 26;
+	h2 = h2 & 0x3ffffff;
+	h3 += c;
+	c = h3 >> 26;
+	h3 = h3 & 0x3ffffff;
+	h4 += c;
+	c = h4 >> 26;
+	h4 = h4 & 0x3ffffff;
+	h0 += c * 5;
+	c = h0 >> 26;
+	h0 = h0 & 0x3ffffff;
+	h1 += c;
+
+	/* compute h + -p */
+	g0 = h0 + 5;
+	c = g0 >> 26;
+	g0 &= 0x3ffffff;
+	g1 = h1 + c;
+	c = g1 >> 26;
+	g1 &= 0x3ffffff;
+	g2 = h2 + c;
+	c = g2 >> 26;
+	g2 &= 0x3ffffff;
+	g3 = h3 + c;
+	c = g3 >> 26;
+	g3 &= 0x3ffffff;
+	g4 = h4 + c - (1UL << 26);
+
+	/* select h if h < p, or h + -p if h >= p */
+	mask = (g4 >> ((sizeof(u32) * 8) - 1)) - 1;
+	g0 &= mask;
+	g1 &= mask;
+	g2 &= mask;
+	g3 &= mask;
+	g4 &= mask;
+	mask = ~mask;
+
+	h0 = (h0 & mask) | g0;
+	h1 = (h1 & mask) | g1;
+	h2 = (h2 & mask) | g2;
+	h3 = (h3 & mask) | g3;
+	h4 = (h4 & mask) | g4;
+
+	/* h = h % (2^128) */
+	h0 = ((h0) | (h1 << 26)) & 0xffffffff;
+	h1 = ((h1 >> 6) | (h2 << 20)) & 0xffffffff;
+	h2 = ((h2 >> 12) | (h3 << 14)) & 0xffffffff;
+	h3 = ((h3 >> 18) | (h4 << 8)) & 0xffffffff;
+
+	/* mac = (h + nonce) % (2^128) */
+	f = (u64)h0 + nonce[0];
+	h0 = (u32)f;
+	f = (u64)h1 + nonce[1] + (f >> 32);
+	h1 = (u32)f;
+	f = (u64)h2 + nonce[2] + (f >> 32);
+	h2 = (u32)f;
+	f = (u64)h3 + nonce[3] + (f >> 32);
+	h3 = (u32)f;
+
+	put_unaligned_le32(h0, &mac[0]);
+	put_unaligned_le32(h1, &mac[4]);
+	put_unaligned_le32(h2, &mac[8]);
+	put_unaligned_le32(h3, &mac[12]);
+}
diff --git a/src/crypto/zinc/poly1305/poly1305-donna64.h b/src/crypto/zinc/poly1305/poly1305-donna64.h
new file mode 100644
index 0000000..2aa2570
--- /dev/null
+++ b/src/crypto/zinc/poly1305/poly1305-donna64.h
@@ -0,0 +1,177 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * Copyright (C) 2015-2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ *
+ * This is based in part on Andrew Moon's poly1305-donna, which is in the
+ * public domain.
+ */
+
+typedef __uint128_t u128;
+
+struct poly1305_internal {
+	u64 r[3];
+	u64 h[3];
+};
+
+static void poly1305_init_generic(void *ctx, const u8 key[16])
+{
+	struct poly1305_internal *st = (struct poly1305_internal *)ctx;
+	u64 t0, t1;
+
+	/* r &= 0xffffffc0ffffffc0ffffffc0fffffff */
+	t0 = get_unaligned_le64(&key[0]);
+	t1 = get_unaligned_le64(&key[8]);
+
+	st->r[0] = t0 & 0xffc0fffffff;
+	st->r[1] = ((t0 >> 44) | (t1 << 20)) & 0xfffffc0ffff;
+	st->r[2] = ((t1 >> 24)) & 0x00ffffffc0f;
+
+	/* h = 0 */
+	st->h[0] = 0;
+	st->h[1] = 0;
+	st->h[2] = 0;
+}
+
+static void poly1305_blocks_generic(void *ctx, const u8 *input, size_t len,
+				    const u32 padbit)
+{
+	struct poly1305_internal *st = (struct poly1305_internal *)ctx;
+	const u64 hibit = ((u64)padbit) << 40;
+	u64 r0, r1, r2;
+	u64 s1, s2;
+	u64 h0, h1, h2;
+	u64 c;
+	u128 d0, d1, d2, d;
+
+	r0 = st->r[0];
+	r1 = st->r[1];
+	r2 = st->r[2];
+
+	h0 = st->h[0];
+	h1 = st->h[1];
+	h2 = st->h[2];
+
+	s1 = r1 * (5 << 2);
+	s2 = r2 * (5 << 2);
+
+	while (len >= POLY1305_BLOCK_SIZE) {
+		u64 t0, t1;
+
+		/* h += m[i] */
+		t0 = get_unaligned_le64(&input[0]);
+		t1 = get_unaligned_le64(&input[8]);
+
+		h0 += t0 & 0xfffffffffff;
+		h1 += ((t0 >> 44) | (t1 << 20)) & 0xfffffffffff;
+		h2 += (((t1 >> 24)) & 0x3ffffffffff) | hibit;
+
+		/* h *= r */
+		d0 = (u128)h0 * r0;
+		d = (u128)h1 * s2;
+		d0 += d;
+		d = (u128)h2 * s1;
+		d0 += d;
+		d1 = (u128)h0 * r1;
+		d = (u128)h1 * r0;
+		d1 += d;
+		d = (u128)h2 * s2;
+		d1 += d;
+		d2 = (u128)h0 * r2;
+		d = (u128)h1 * r1;
+		d2 += d;
+		d = (u128)h2 * r0;
+		d2 += d;
+
+		/* (partial) h %= p */
+		c = (u64)(d0 >> 44);
+		h0 = (u64)d0 & 0xfffffffffff;
+		d1 += c;
+		c = (u64)(d1 >> 44);
+		h1 = (u64)d1 & 0xfffffffffff;
+		d2 += c;
+		c = (u64)(d2 >> 42);
+		h2 = (u64)d2 & 0x3ffffffffff;
+		h0 += c * 5;
+		c = h0 >> 44;
+		h0 = h0 & 0xfffffffffff;
+		h1 += c;
+
+		input += POLY1305_BLOCK_SIZE;
+		len -= POLY1305_BLOCK_SIZE;
+	}
+
+	st->h[0] = h0;
+	st->h[1] = h1;
+	st->h[2] = h2;
+}
+
+static void poly1305_emit_generic(void *ctx, u8 mac[16], const u32 nonce[4])
+{
+	struct poly1305_internal *st = (struct poly1305_internal *)ctx;
+	u64 h0, h1, h2, c;
+	u64 g0, g1, g2;
+	u64 t0, t1;
+
+	/* fully carry h */
+	h0 = st->h[0];
+	h1 = st->h[1];
+	h2 = st->h[2];
+
+	c = h1 >> 44;
+	h1 &= 0xfffffffffff;
+	h2 += c;
+	c = h2 >> 42;
+	h2 &= 0x3ffffffffff;
+	h0 += c * 5;
+	c = h0 >> 44;
+	h0 &= 0xfffffffffff;
+	h1 += c;
+	c = h1 >> 44;
+	h1 &= 0xfffffffffff;
+	h2 += c;
+	c = h2 >> 42;
+	h2 &= 0x3ffffffffff;
+	h0 += c * 5;
+	c = h0 >> 44;
+	h0 &= 0xfffffffffff;
+	h1 += c;
+
+	/* compute h + -p */
+	g0 = h0 + 5;
+	c  = g0 >> 44;
+	g0 &= 0xfffffffffff;
+	g1 = h1 + c;
+	c  = g1 >> 44;
+	g1 &= 0xfffffffffff;
+	g2 = h2 + c - (1ULL << 42);
+
+	/* select h if h < p, or h + -p if h >= p */
+	c = (g2 >> ((sizeof(u64) * 8) - 1)) - 1;
+	g0 &= c;
+	g1 &= c;
+	g2 &= c;
+	c  = ~c;
+	h0 = (h0 & c) | g0;
+	h1 = (h1 & c) | g1;
+	h2 = (h2 & c) | g2;
+
+	/* h = (h + nonce) */
+	t0 = ((u64)nonce[1] << 32) | nonce[0];
+	t1 = ((u64)nonce[3] << 32) | nonce[2];
+
+	h0 += t0 & 0xfffffffffff;
+	c = h0 >> 44;
+	h0 &= 0xfffffffffff;
+	h1 += (((t0 >> 44) | (t1 << 20)) & 0xfffffffffff) + c;
+	c = h1 >> 44;
+	h1 &= 0xfffffffffff;
+	h2 += (((t1 >> 24)) & 0x3ffffffffff) + c;
+	h2 &= 0x3ffffffffff;
+
+	/* mac = h % (2^128) */
+	h0 = h0 | (h1 << 44);
+	h1 = (h1 >> 20) | (h2 << 24);
+
+	put_unaligned_le64(h0, &mac[0]);
+	put_unaligned_le64(h1, &mac[8]);
+}
diff --git a/src/crypto/zinc/poly1305/poly1305.c b/src/crypto/zinc/poly1305/poly1305.c
index fd662de..c09b092 100644
--- a/src/crypto/zinc/poly1305/poly1305.c
+++ b/src/crypto/zinc/poly1305/poly1305.c
@@ -1,9 +1,6 @@
-/* SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0
+/* SPDX-License-Identifier: GPL-2.0
  *
  * Copyright (C) 2015-2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
- * Copyright (C) 2006-2017 CRYPTOGAMS by <appro@openssl.org>. All Rights Reserved.
- *
- * This is based in part on Andy Polyakov's implementation from CRYPTOGAMS.
  *
  * Implementation of the Poly1305 message authenticator.
  *
@@ -23,7 +20,7 @@ static inline bool poly1305_init_arch(void *ctx,
 {
 	return false;
 }
-static inline bool poly1305_blocks_arch(void *ctx, const u8 *inp,
+static inline bool poly1305_blocks_arch(void *ctx, const u8 *input,
 					const size_t len, const u32 padbit,
 					simd_context_t simd_context)
 {
@@ -40,166 +37,11 @@ void __init poly1305_fpu_init(void)
 }
 #endif
 
-struct poly1305_internal {
-	u32 h[5];
-	u32 r[4];
-};
-
-static void poly1305_init_generic(void *ctx, const u8 key[16])
-{
-	struct poly1305_internal *st = (struct poly1305_internal *)ctx;
-
-	/* h = 0 */
-	st->h[0] = 0;
-	st->h[1] = 0;
-	st->h[2] = 0;
-	st->h[3] = 0;
-	st->h[4] = 0;
-
-	/* r &= 0xffffffc0ffffffc0ffffffc0fffffff */
-	st->r[0] = get_unaligned_le32(&key[ 0]) & 0x0fffffff;
-	st->r[1] = get_unaligned_le32(&key[ 4]) & 0x0ffffffc;
-	st->r[2] = get_unaligned_le32(&key[ 8]) & 0x0ffffffc;
-	st->r[3] = get_unaligned_le32(&key[12]) & 0x0ffffffc;
-}
-
-static void poly1305_blocks_generic(void *ctx, const u8 *inp, size_t len,
-				    const u32 padbit)
-{
-#define CONSTANT_TIME_CARRY(a, b)                                              \
-	((a ^ ((a ^ b) | ((a - b) ^ b))) >> (sizeof(a) * 8 - 1))
-	struct poly1305_internal *st = (struct poly1305_internal *)ctx;
-	u32 r0, r1, r2, r3;
-	u32 s1, s2, s3;
-	u32 h0, h1, h2, h3, h4, c;
-	u64 d0, d1, d2, d3;
-
-	r0 = st->r[0];
-	r1 = st->r[1];
-	r2 = st->r[2];
-	r3 = st->r[3];
-
-	s1 = r1 + (r1 >> 2);
-	s2 = r2 + (r2 >> 2);
-	s3 = r3 + (r3 >> 2);
-
-	h0 = st->h[0];
-	h1 = st->h[1];
-	h2 = st->h[2];
-	h3 = st->h[3];
-	h4 = st->h[4];
-
-	while (len >= POLY1305_BLOCK_SIZE) {
-		/* h += m[i] */
-		h0 = (u32)(d0 = (u64)h0 + (0       ) + get_unaligned_le32(&inp[ 0]));
-		h1 = (u32)(d1 = (u64)h1 + (d0 >> 32) + get_unaligned_le32(&inp[ 4]));
-		h2 = (u32)(d2 = (u64)h2 + (d1 >> 32) + get_unaligned_le32(&inp[ 8]));
-		h3 = (u32)(d3 = (u64)h3 + (d2 >> 32) + get_unaligned_le32(&inp[12]));
-		h4 += (u32)(d3 >> 32) + padbit;
-
-		/* h *= r "%" p, where "%" stands for "partial remainder" */
-		d0 = ((u64)h0 * r0) +
-		     ((u64)h1 * s3) +
-		     ((u64)h2 * s2) +
-		     ((u64)h3 * s1);
-		d1 = ((u64)h0 * r1) +
-		     ((u64)h1 * r0) +
-		     ((u64)h2 * s3) +
-		     ((u64)h3 * s2) +
-		     (h4 * s1);
-		d2 = ((u64)h0 * r2) +
-		     ((u64)h1 * r1) +
-		     ((u64)h2 * r0) +
-		     ((u64)h3 * s3) +
-		     (h4 * s2);
-		d3 = ((u64)h0 * r3) +
-		     ((u64)h1 * r2) +
-		     ((u64)h2 * r1) +
-		     ((u64)h3 * r0) +
-		     (h4 * s3);
-		h4 = (h4 * r0);
-
-		/* last reduction step: */
-		/* a) h4:h0 = h4<<128 + d3<<96 + d2<<64 + d1<<32 + d0 */
-		h0 = (u32)d0;
-		h1 = (u32)(d1 += d0 >> 32);
-		h2 = (u32)(d2 += d1 >> 32);
-		h3 = (u32)(d3 += d2 >> 32);
-		h4 += (u32)(d3 >> 32);
-		/* b) (h4:h0 += (h4:h0>>130) * 5) %= 2^130 */
-		c = (h4 >> 2) + (h4 & ~3U);
-		h4 &= 3;
-		h0 += c;
-		h1 += (c = CONSTANT_TIME_CARRY(h0, c));
-		h2 += (c = CONSTANT_TIME_CARRY(h1, c));
-		h3 += (c = CONSTANT_TIME_CARRY(h2, c));
-		h4 += CONSTANT_TIME_CARRY(h3, c);
-		/*
-		 * Occasional overflows to 3rd bit of h4 are taken care of
-		 * "naturally". If after this point we end up at the top of
-		 * this loop, then the overflow bit will be accounted for
-		 * in next iteration. If we end up in poly1305_emit, then
-		 * comparison to modulus below will still count as "carry
-		 * into 131st bit", so that properly reduced value will be
-		 * picked in conditional move.
-		 */
-
-		inp += POLY1305_BLOCK_SIZE;
-		len -= POLY1305_BLOCK_SIZE;
-	}
-
-	st->h[0] = h0;
-	st->h[1] = h1;
-	st->h[2] = h2;
-	st->h[3] = h3;
-	st->h[4] = h4;
-#undef CONSTANT_TIME_CARRY
-}
-
-static void poly1305_emit_generic(void *ctx, u8 mac[16], const u32 nonce[4])
-{
-	struct poly1305_internal *st = (struct poly1305_internal *)ctx;
-	u32 h0, h1, h2, h3, h4;
-	u32 g0, g1, g2, g3, g4;
-	u64 t;
-	u32 mask;
-
-	h0 = st->h[0];
-	h1 = st->h[1];
-	h2 = st->h[2];
-	h3 = st->h[3];
-	h4 = st->h[4];
-
-	/* compare to modulus by computing h + -p */
-	g0 = (u32)(t = (u64)h0 + 5);
-	g1 = (u32)(t = (u64)h1 + (t >> 32));
-	g2 = (u32)(t = (u64)h2 + (t >> 32));
-	g3 = (u32)(t = (u64)h3 + (t >> 32));
-	g4 = h4 + (u32)(t >> 32);
-
-	/* if there was carry into 131st bit, h3:h0 = g3:g0 */
-	mask = 0 - (g4 >> 2);
-	g0 &= mask;
-	g1 &= mask;
-	g2 &= mask;
-	g3 &= mask;
-	mask = ~mask;
-	h0 = (h0 & mask) | g0;
-	h1 = (h1 & mask) | g1;
-	h2 = (h2 & mask) | g2;
-	h3 = (h3 & mask) | g3;
-
-	/* mac = (h + nonce) % (2^128) */
-	h0 = (u32)(t = (u64)h0 + nonce[0]);
-	h1 = (u32)(t = (u64)h1 + (t >> 32) + nonce[1]);
-	h2 = (u32)(t = (u64)h2 + (t >> 32) + nonce[2]);
-	h3 = (u32)(t = (u64)h3 + (t >> 32) + nonce[3]);
-
-	put_unaligned_le32(h0, &mac[ 0]);
-	put_unaligned_le32(h1, &mac[ 4]);
-	put_unaligned_le32(h2, &mac[ 8]);
-	put_unaligned_le32(h3, &mac[12]);
-}
+#if defined(CONFIG_ARCH_SUPPORTS_INT128) && defined(__SIZEOF_INT128__)
+#include "poly1305-donna64.h"
+#else
+#include "poly1305-donna32.h"
+#endif
 
 void poly1305_init(struct poly1305_ctx *ctx, const u8 key[POLY1305_KEY_SIZE],
 		   simd_context_t simd_context)
@@ -211,16 +53,17 @@ void poly1305_init(struct poly1305_ctx *ctx, const u8 key[POLY1305_KEY_SIZE],
 
 	if (!poly1305_init_arch(ctx->opaque, key, simd_context))
 		poly1305_init_generic(ctx->opaque, key);
+
 	ctx->num = 0;
 }
 EXPORT_SYMBOL(poly1305_init);
 
-static inline void poly1305_blocks(void *ctx, const u8 *inp, const size_t len,
+static inline void poly1305_blocks(void *ctx, const u8 *input, const size_t len,
 				   const u32 padbit,
 				   simd_context_t simd_context)
 {
-	if (!poly1305_blocks_arch(ctx, inp, len, padbit, simd_context))
-		poly1305_blocks_generic(ctx, inp, len, padbit);
+	if (!poly1305_blocks_arch(ctx, input, len, padbit, simd_context))
+		poly1305_blocks_generic(ctx, input, len, padbit);
 }
 
 static inline void poly1305_emit(void *ctx, u8 mac[POLY1305_KEY_SIZE],
@@ -231,7 +74,7 @@ static inline void poly1305_emit(void *ctx, u8 mac[POLY1305_KEY_SIZE],
 		poly1305_emit_generic(ctx, mac, nonce);
 }
 
-void poly1305_update(struct poly1305_ctx *ctx, const u8 *inp, size_t len,
+void poly1305_update(struct poly1305_ctx *ctx, const u8 *input, size_t len,
 		     simd_context_t simd_context)
 {
 	const size_t num = ctx->num % POLY1305_BLOCK_SIZE;
@@ -239,30 +82,28 @@ void poly1305_update(struct poly1305_ctx *ctx, const u8 *inp, size_t len,
 
 	if (num) {
 		rem = POLY1305_BLOCK_SIZE - num;
-		if (len >= rem) {
-			memcpy(ctx->data + num, inp, rem);
-			poly1305_blocks(ctx->opaque, ctx->data,
-					POLY1305_BLOCK_SIZE, 1, simd_context);
-			inp += rem;
-			len -= rem;
-		} else {
-			/* Still not enough data to process a block. */
-			memcpy(ctx->data + num, inp, len);
+		if (len < rem) {
+			memcpy(ctx->data + num, input, len);
 			ctx->num = num + len;
 			return;
 		}
+		memcpy(ctx->data + num, input, rem);
+		poly1305_blocks(ctx->opaque, ctx->data, POLY1305_BLOCK_SIZE, 1,
+				simd_context);
+		input += rem;
+		len -= rem;
 	}
 
 	rem = len % POLY1305_BLOCK_SIZE;
 	len -= rem;
 
 	if (len >= POLY1305_BLOCK_SIZE) {
-		poly1305_blocks(ctx->opaque, inp, len, 1, simd_context);
-		inp += len;
+		poly1305_blocks(ctx->opaque, input, len, 1, simd_context);
+		input += len;
 	}
 
 	if (rem)
-		memcpy(ctx->data, inp, rem);
+		memcpy(ctx->data, input, rem);
 
 	ctx->num = rem;
 }
@@ -274,7 +115,7 @@ void poly1305_finish(struct poly1305_ctx *ctx, u8 mac[POLY1305_MAC_SIZE],
 	size_t num = ctx->num % POLY1305_BLOCK_SIZE;
 
 	if (num) {
-		ctx->data[num++] = 1; /* pad bit */
+		ctx->data[num++] = 1;
 		while (num < POLY1305_BLOCK_SIZE)
 			ctx->data[num++] = 0;
 		poly1305_blocks(ctx->opaque, ctx->data, POLY1305_BLOCK_SIZE, 0,
@@ -283,7 +124,6 @@ void poly1305_finish(struct poly1305_ctx *ctx, u8 mac[POLY1305_MAC_SIZE],
 
 	poly1305_emit(ctx->opaque, mac, ctx->nonce, simd_context);
 
-	/* zero out the state */
 	memzero_explicit(ctx, sizeof(*ctx));
 }
 EXPORT_SYMBOL(poly1305_finish);