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siphash: use one source of truth for siphash permutations
The SipHash family of permutations is currently used in three places: - siphash.c itself, used in the ordinary way it was intended. - random32.c, in a construction from an anonymous contributor. - random.c, as part of its fast_mix function. Each one of these places reinvents the wheel with the same C code, same rotation constants, and same symmetry-breaking constants. This commit tidies things up a bit by placing macros for the permutations and constants into siphash.h, where each of the three .c users can access them. It also leaves a note dissuading more users of them from emerging. Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
This commit is contained in:
Jason A. Donenfeld
parent
791332b3cb
commit
e73aaae2fa
@ -52,6 +52,7 @@
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#include <linux/uuid.h>
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#include <linux/uaccess.h>
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#include <linux/suspend.h>
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#include <linux/siphash.h>
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#include <crypto/chacha.h>
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#include <crypto/blake2s.h>
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#include <asm/processor.h>
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@ -1086,12 +1087,11 @@ struct fast_pool {
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static DEFINE_PER_CPU(struct fast_pool, irq_randomness) = {
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#ifdef CONFIG_64BIT
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/* SipHash constants */
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.pool = { 0x736f6d6570736575UL, 0x646f72616e646f6dUL,
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0x6c7967656e657261UL, 0x7465646279746573UL }
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#define FASTMIX_PERM SIPHASH_PERMUTATION
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.pool = { SIPHASH_CONST_0, SIPHASH_CONST_1, SIPHASH_CONST_2, SIPHASH_CONST_3 }
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#else
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/* HalfSipHash constants */
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.pool = { 0, 0, 0x6c796765U, 0x74656462U }
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#define FASTMIX_PERM HSIPHASH_PERMUTATION
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.pool = { HSIPHASH_CONST_0, HSIPHASH_CONST_1, HSIPHASH_CONST_2, HSIPHASH_CONST_3 }
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#endif
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};
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@ -1103,27 +1103,11 @@ static DEFINE_PER_CPU(struct fast_pool, irq_randomness) = {
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*/
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static void fast_mix(unsigned long s[4], unsigned long v1, unsigned long v2)
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{
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#ifdef CONFIG_64BIT
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#define PERM() do { \
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s[0] += s[1]; s[1] = rol64(s[1], 13); s[1] ^= s[0]; s[0] = rol64(s[0], 32); \
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s[2] += s[3]; s[3] = rol64(s[3], 16); s[3] ^= s[2]; \
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s[0] += s[3]; s[3] = rol64(s[3], 21); s[3] ^= s[0]; \
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s[2] += s[1]; s[1] = rol64(s[1], 17); s[1] ^= s[2]; s[2] = rol64(s[2], 32); \
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} while (0)
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#else
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#define PERM() do { \
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s[0] += s[1]; s[1] = rol32(s[1], 5); s[1] ^= s[0]; s[0] = rol32(s[0], 16); \
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s[2] += s[3]; s[3] = rol32(s[3], 8); s[3] ^= s[2]; \
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s[0] += s[3]; s[3] = rol32(s[3], 7); s[3] ^= s[0]; \
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s[2] += s[1]; s[1] = rol32(s[1], 13); s[1] ^= s[2]; s[2] = rol32(s[2], 16); \
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} while (0)
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#endif
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s[3] ^= v1;
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PERM();
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FASTMIX_PERM(s[0], s[1], s[2], s[3]);
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s[0] ^= v1;
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s[3] ^= v2;
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PERM();
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FASTMIX_PERM(s[0], s[1], s[2], s[3]);
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s[0] ^= v2;
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}
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@ -10,6 +10,7 @@
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#include <linux/types.h>
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#include <linux/percpu.h>
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#include <linux/siphash.h>
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u32 prandom_u32(void);
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void prandom_bytes(void *buf, size_t nbytes);
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@ -27,15 +28,10 @@ DECLARE_PER_CPU(unsigned long, net_rand_noise);
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* The core SipHash round function. Each line can be executed in
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* parallel given enough CPU resources.
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*/
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#define PRND_SIPROUND(v0, v1, v2, v3) ( \
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v0 += v1, v1 = rol64(v1, 13), v2 += v3, v3 = rol64(v3, 16), \
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v1 ^= v0, v0 = rol64(v0, 32), v3 ^= v2, \
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v0 += v3, v3 = rol64(v3, 21), v2 += v1, v1 = rol64(v1, 17), \
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v3 ^= v0, v1 ^= v2, v2 = rol64(v2, 32) \
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)
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#define PRND_SIPROUND(v0, v1, v2, v3) SIPHASH_PERMUTATION(v0, v1, v2, v3)
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#define PRND_K0 (0x736f6d6570736575 ^ 0x6c7967656e657261)
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#define PRND_K1 (0x646f72616e646f6d ^ 0x7465646279746573)
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#define PRND_K0 (SIPHASH_CONST_0 ^ SIPHASH_CONST_2)
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#define PRND_K1 (SIPHASH_CONST_1 ^ SIPHASH_CONST_3)
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#elif BITS_PER_LONG == 32
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/*
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@ -43,14 +39,9 @@ DECLARE_PER_CPU(unsigned long, net_rand_noise);
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* This is weaker, but 32-bit machines are not used for high-traffic
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* applications, so there is less output for an attacker to analyze.
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*/
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#define PRND_SIPROUND(v0, v1, v2, v3) ( \
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v0 += v1, v1 = rol32(v1, 5), v2 += v3, v3 = rol32(v3, 8), \
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v1 ^= v0, v0 = rol32(v0, 16), v3 ^= v2, \
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v0 += v3, v3 = rol32(v3, 7), v2 += v1, v1 = rol32(v1, 13), \
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v3 ^= v0, v1 ^= v2, v2 = rol32(v2, 16) \
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)
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#define PRND_K0 0x6c796765
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#define PRND_K1 0x74656462
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#define PRND_SIPROUND(v0, v1, v2, v3) HSIPHASH_PERMUTATION(v0, v1, v2, v3)
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#define PRND_K0 (HSIPHASH_CONST_0 ^ HSIPHASH_CONST_2)
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#define PRND_K1 (HSIPHASH_CONST_1 ^ HSIPHASH_CONST_3)
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#else
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#error Unsupported BITS_PER_LONG
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@ -138,4 +138,32 @@ static inline u32 hsiphash(const void *data, size_t len,
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return ___hsiphash_aligned(data, len, key);
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}
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/*
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* These macros expose the raw SipHash and HalfSipHash permutations.
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* Do not use them directly! If you think you have a use for them,
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* be sure to CC the maintainer of this file explaining why.
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*/
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#define SIPHASH_PERMUTATION(a, b, c, d) ( \
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(a) += (b), (b) = rol64((b), 13), (b) ^= (a), (a) = rol64((a), 32), \
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(c) += (d), (d) = rol64((d), 16), (d) ^= (c), \
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(a) += (d), (d) = rol64((d), 21), (d) ^= (a), \
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(c) += (b), (b) = rol64((b), 17), (b) ^= (c), (c) = rol64((c), 32))
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#define SIPHASH_CONST_0 0x736f6d6570736575ULL
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#define SIPHASH_CONST_1 0x646f72616e646f6dULL
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#define SIPHASH_CONST_2 0x6c7967656e657261ULL
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#define SIPHASH_CONST_3 0x7465646279746573ULL
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#define HSIPHASH_PERMUTATION(a, b, c, d) ( \
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(a) += (b), (b) = rol32((b), 5), (b) ^= (a), (a) = rol32((a), 16), \
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(c) += (d), (d) = rol32((d), 8), (d) ^= (c), \
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(a) += (d), (d) = rol32((d), 7), (d) ^= (a), \
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(c) += (b), (b) = rol32((b), 13), (b) ^= (c), (c) = rol32((c), 16))
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#define HSIPHASH_CONST_0 0U
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#define HSIPHASH_CONST_1 0U
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#define HSIPHASH_CONST_2 0x6c796765U
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#define HSIPHASH_CONST_3 0x74656462U
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#endif /* _LINUX_SIPHASH_H */
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@ -18,19 +18,13 @@
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#include <asm/word-at-a-time.h>
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#endif
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#define SIPROUND \
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do { \
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v0 += v1; v1 = rol64(v1, 13); v1 ^= v0; v0 = rol64(v0, 32); \
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v2 += v3; v3 = rol64(v3, 16); v3 ^= v2; \
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v0 += v3; v3 = rol64(v3, 21); v3 ^= v0; \
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v2 += v1; v1 = rol64(v1, 17); v1 ^= v2; v2 = rol64(v2, 32); \
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} while (0)
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#define SIPROUND SIPHASH_PERMUTATION(v0, v1, v2, v3)
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#define PREAMBLE(len) \
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u64 v0 = 0x736f6d6570736575ULL; \
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u64 v1 = 0x646f72616e646f6dULL; \
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u64 v2 = 0x6c7967656e657261ULL; \
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u64 v3 = 0x7465646279746573ULL; \
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u64 v0 = SIPHASH_CONST_0; \
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u64 v1 = SIPHASH_CONST_1; \
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u64 v2 = SIPHASH_CONST_2; \
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u64 v3 = SIPHASH_CONST_3; \
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u64 b = ((u64)(len)) << 56; \
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v3 ^= key->key[1]; \
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v2 ^= key->key[0]; \
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@ -389,19 +383,13 @@ u32 hsiphash_4u32(const u32 first, const u32 second, const u32 third,
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}
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EXPORT_SYMBOL(hsiphash_4u32);
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#else
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#define HSIPROUND \
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do { \
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v0 += v1; v1 = rol32(v1, 5); v1 ^= v0; v0 = rol32(v0, 16); \
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v2 += v3; v3 = rol32(v3, 8); v3 ^= v2; \
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v0 += v3; v3 = rol32(v3, 7); v3 ^= v0; \
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v2 += v1; v1 = rol32(v1, 13); v1 ^= v2; v2 = rol32(v2, 16); \
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} while (0)
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#define HSIPROUND HSIPHASH_PERMUTATION(v0, v1, v2, v3)
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#define HPREAMBLE(len) \
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u32 v0 = 0; \
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u32 v1 = 0; \
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u32 v2 = 0x6c796765U; \
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u32 v3 = 0x74656462U; \
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u32 v0 = HSIPHASH_CONST_0; \
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u32 v1 = HSIPHASH_CONST_1; \
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u32 v2 = HSIPHASH_CONST_2; \
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u32 v3 = HSIPHASH_CONST_3; \
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u32 b = ((u32)(len)) << 24; \
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v3 ^= key->key[1]; \
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v2 ^= key->key[0]; \
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