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linux/lib/siphash.c
Arnd Bergmann f7e5b9bfa6 siphash: use _unaligned version by default 
On ARM v6 and later, we define CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
because the ordinary load/store instructions (ldr, ldrh, ldrb) can
tolerate any misalignment of the memory address. However, load/store
double and load/store multiple instructions (ldrd, ldm) may still only
be used on memory addresses that are 32-bit aligned, and so we have to
use the CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS macro with care, or we
may end up with a severe performance hit due to alignment traps that
require fixups by the kernel. Testing shows that this currently happens
with clang-13 but not gcc-11. In theory, any compiler version can
produce this bug or other problems, as we are dealing with undefined
behavior in C99 even on architectures that support this in hardware,
see also https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100363.

Fortunately, the get_unaligned() accessors do the right thing: when
building for ARMv6 or later, the compiler will emit unaligned accesses
using the ordinary load/store instructions (but avoid the ones that
require 32-bit alignment). When building for older ARM, those accessors
will emit the appropriate sequence of ldrb/mov/orr instructions. And on
architectures that can truly tolerate any kind of misalignment, the
get_unaligned() accessors resolve to the leXX_to_cpup accessors that
operate on aligned addresses.

Since the compiler will in fact emit ldrd or ldm instructions when
building this code for ARM v6 or later, the solution is to use the
unaligned accessors unconditionally on architectures where this is
known to be fast. The _aligned version of the hash function is
however still needed to get the best performance on architectures
that cannot do any unaligned access in hardware.

This new version avoids the undefined behavior and should produce
the fastest hash on all architectures we support.

Link: https://lore.kernel.org/linux-arm-kernel/20181008211554.5355-4-ard.biesheuvel@linaro.org/
Link: https://lore.kernel.org/linux-crypto/CAK8P3a2KfmmGDbVHULWevB0hv71P2oi2ZCHEAqT=8dQfa0=cqQ@mail.gmail.com/
Reported-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Fixes: 2c956a6077 ("siphash: add cryptographically secure PRF")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Jason A. Donenfeld <Jason@zx2c4.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2021-11-29 19:50:50 -08:00

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/* Copyright (C) 2016 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
*
* This file is provided under a dual BSD/GPLv2 license.
*
* SipHash: a fast short-input PRF
* https://131002.net/siphash/
*
* This implementation is specifically for SipHash2-4 for a secure PRF
* and HalfSipHash1-3/SipHash1-3 for an insecure PRF only suitable for
* hashtables.
*/
#include <linux/siphash.h>
#include <asm/unaligned.h>
#if defined(CONFIG_DCACHE_WORD_ACCESS) && BITS_PER_LONG == 64
#include <linux/dcache.h>
#include <asm/word-at-a-time.h>
#endif
#define SIPROUND \
do { \
v0 += v1; v1 = rol64(v1, 13); v1 ^= v0; v0 = rol64(v0, 32); \
v2 += v3; v3 = rol64(v3, 16); v3 ^= v2; \
v0 += v3; v3 = rol64(v3, 21); v3 ^= v0; \
v2 += v1; v1 = rol64(v1, 17); v1 ^= v2; v2 = rol64(v2, 32); \
} while (0)
#define PREAMBLE(len) \
u64 v0 = 0x736f6d6570736575ULL; \
u64 v1 = 0x646f72616e646f6dULL; \
u64 v2 = 0x6c7967656e657261ULL; \
u64 v3 = 0x7465646279746573ULL; \
u64 b = ((u64)(len)) << 56; \
v3 ^= key->key[1]; \
v2 ^= key->key[0]; \
v1 ^= key->key[1]; \
v0 ^= key->key[0];
#define POSTAMBLE \
v3 ^= b; \
SIPROUND; \
SIPROUND; \
v0 ^= b; \
v2 ^= 0xff; \
SIPROUND; \
SIPROUND; \
SIPROUND; \
SIPROUND; \
return (v0 ^ v1) ^ (v2 ^ v3);
#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
u64 __siphash_aligned(const void *data, size_t len, const siphash_key_t *key)
{
const u8 *end = data + len - (len % sizeof(u64));
const u8 left = len & (sizeof(u64) - 1);
u64 m;
PREAMBLE(len)
for (; data != end; data += sizeof(u64)) {
m = le64_to_cpup(data);
v3 ^= m;
SIPROUND;
SIPROUND;
v0 ^= m;
}
#if defined(CONFIG_DCACHE_WORD_ACCESS) && BITS_PER_LONG == 64
if (left)
b |= le64_to_cpu((__force __le64)(load_unaligned_zeropad(data) &
bytemask_from_count(left)));
#else
switch (left) {
case 7: b |= ((u64)end[6]) << 48; fallthrough;
case 6: b |= ((u64)end[5]) << 40; fallthrough;
case 5: b |= ((u64)end[4]) << 32; fallthrough;
case 4: b |= le32_to_cpup(data); break;
case 3: b |= ((u64)end[2]) << 16; fallthrough;
case 2: b |= le16_to_cpup(data); break;
case 1: b |= end[0];
}
#endif
POSTAMBLE
}
EXPORT_SYMBOL(__siphash_aligned);
#endif
u64 __siphash_unaligned(const void *data, size_t len, const siphash_key_t *key)
{
const u8 *end = data + len - (len % sizeof(u64));
const u8 left = len & (sizeof(u64) - 1);
u64 m;
PREAMBLE(len)
for (; data != end; data += sizeof(u64)) {
m = get_unaligned_le64(data);
v3 ^= m;
SIPROUND;
SIPROUND;
v0 ^= m;
}
#if defined(CONFIG_DCACHE_WORD_ACCESS) && BITS_PER_LONG == 64
if (left)
b |= le64_to_cpu((__force __le64)(load_unaligned_zeropad(data) &
bytemask_from_count(left)));
#else
switch (left) {
case 7: b |= ((u64)end[6]) << 48; fallthrough;
case 6: b |= ((u64)end[5]) << 40; fallthrough;
case 5: b |= ((u64)end[4]) << 32; fallthrough;
case 4: b |= get_unaligned_le32(end); break;
case 3: b |= ((u64)end[2]) << 16; fallthrough;
case 2: b |= get_unaligned_le16(end); break;
case 1: b |= end[0];
}
#endif
POSTAMBLE
}
EXPORT_SYMBOL(__siphash_unaligned);
/**
* siphash_1u64 - compute 64-bit siphash PRF value of a u64
* @first: first u64
* @key: the siphash key
*/
u64 siphash_1u64(const u64 first, const siphash_key_t *key)
{
PREAMBLE(8)
v3 ^= first;
SIPROUND;
SIPROUND;
v0 ^= first;
POSTAMBLE
}
EXPORT_SYMBOL(siphash_1u64);
/**
* siphash_2u64 - compute 64-bit siphash PRF value of 2 u64
* @first: first u64
* @second: second u64
* @key: the siphash key
*/
u64 siphash_2u64(const u64 first, const u64 second, const siphash_key_t *key)
{
PREAMBLE(16)
v3 ^= first;
SIPROUND;
SIPROUND;
v0 ^= first;
v3 ^= second;
SIPROUND;
SIPROUND;
v0 ^= second;
POSTAMBLE
}
EXPORT_SYMBOL(siphash_2u64);
/**
* siphash_3u64 - compute 64-bit siphash PRF value of 3 u64
* @first: first u64
* @second: second u64
* @third: third u64
* @key: the siphash key
*/
u64 siphash_3u64(const u64 first, const u64 second, const u64 third,
const siphash_key_t *key)
{
PREAMBLE(24)
v3 ^= first;
SIPROUND;
SIPROUND;
v0 ^= first;
v3 ^= second;
SIPROUND;
SIPROUND;
v0 ^= second;
v3 ^= third;
SIPROUND;
SIPROUND;
v0 ^= third;
POSTAMBLE
}
EXPORT_SYMBOL(siphash_3u64);
/**
* siphash_4u64 - compute 64-bit siphash PRF value of 4 u64
* @first: first u64
* @second: second u64
* @third: third u64
* @forth: forth u64
* @key: the siphash key
*/
u64 siphash_4u64(const u64 first, const u64 second, const u64 third,
const u64 forth, const siphash_key_t *key)
{
PREAMBLE(32)
v3 ^= first;
SIPROUND;
SIPROUND;
v0 ^= first;
v3 ^= second;
SIPROUND;
SIPROUND;
v0 ^= second;
v3 ^= third;
SIPROUND;
SIPROUND;
v0 ^= third;
v3 ^= forth;
SIPROUND;
SIPROUND;
v0 ^= forth;
POSTAMBLE
}
EXPORT_SYMBOL(siphash_4u64);
u64 siphash_1u32(const u32 first, const siphash_key_t *key)
{
PREAMBLE(4)
b |= first;
POSTAMBLE
}
EXPORT_SYMBOL(siphash_1u32);
u64 siphash_3u32(const u32 first, const u32 second, const u32 third,
const siphash_key_t *key)
{
u64 combined = (u64)second << 32 | first;
PREAMBLE(12)
v3 ^= combined;
SIPROUND;
SIPROUND;
v0 ^= combined;
b |= third;
POSTAMBLE
}
EXPORT_SYMBOL(siphash_3u32);
#if BITS_PER_LONG == 64
/* Note that on 64-bit, we make HalfSipHash1-3 actually be SipHash1-3, for
* performance reasons. On 32-bit, below, we actually implement HalfSipHash1-3.
*/
#define HSIPROUND SIPROUND
#define HPREAMBLE(len) PREAMBLE(len)
#define HPOSTAMBLE \
v3 ^= b; \
HSIPROUND; \
v0 ^= b; \
v2 ^= 0xff; \
HSIPROUND; \
HSIPROUND; \
HSIPROUND; \
return (v0 ^ v1) ^ (v2 ^ v3);
#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
u32 __hsiphash_aligned(const void *data, size_t len, const hsiphash_key_t *key)
{
const u8 *end = data + len - (len % sizeof(u64));
const u8 left = len & (sizeof(u64) - 1);
u64 m;
HPREAMBLE(len)
for (; data != end; data += sizeof(u64)) {
m = le64_to_cpup(data);
v3 ^= m;
HSIPROUND;
v0 ^= m;
}
#if defined(CONFIG_DCACHE_WORD_ACCESS) && BITS_PER_LONG == 64
if (left)
b |= le64_to_cpu((__force __le64)(load_unaligned_zeropad(data) &
bytemask_from_count(left)));
#else
switch (left) {
case 7: b |= ((u64)end[6]) << 48; fallthrough;
case 6: b |= ((u64)end[5]) << 40; fallthrough;
case 5: b |= ((u64)end[4]) << 32; fallthrough;
case 4: b |= le32_to_cpup(data); break;
case 3: b |= ((u64)end[2]) << 16; fallthrough;
case 2: b |= le16_to_cpup(data); break;
case 1: b |= end[0];
}
#endif
HPOSTAMBLE
}
EXPORT_SYMBOL(__hsiphash_aligned);
#endif
u32 __hsiphash_unaligned(const void *data, size_t len,
const hsiphash_key_t *key)
{
const u8 *end = data + len - (len % sizeof(u64));
const u8 left = len & (sizeof(u64) - 1);
u64 m;
HPREAMBLE(len)
for (; data != end; data += sizeof(u64)) {
m = get_unaligned_le64(data);
v3 ^= m;
HSIPROUND;
v0 ^= m;
}
#if defined(CONFIG_DCACHE_WORD_ACCESS) && BITS_PER_LONG == 64
if (left)
b |= le64_to_cpu((__force __le64)(load_unaligned_zeropad(data) &
bytemask_from_count(left)));
#else
switch (left) {
case 7: b |= ((u64)end[6]) << 48; fallthrough;
case 6: b |= ((u64)end[5]) << 40; fallthrough;
case 5: b |= ((u64)end[4]) << 32; fallthrough;
case 4: b |= get_unaligned_le32(end); break;
case 3: b |= ((u64)end[2]) << 16; fallthrough;
case 2: b |= get_unaligned_le16(end); break;
case 1: b |= end[0];
}
#endif
HPOSTAMBLE
}
EXPORT_SYMBOL(__hsiphash_unaligned);
/**
* hsiphash_1u32 - compute 64-bit hsiphash PRF value of a u32
* @first: first u32
* @key: the hsiphash key
*/
u32 hsiphash_1u32(const u32 first, const hsiphash_key_t *key)
{
HPREAMBLE(4)
b |= first;
HPOSTAMBLE
}
EXPORT_SYMBOL(hsiphash_1u32);
/**
* hsiphash_2u32 - compute 32-bit hsiphash PRF value of 2 u32
* @first: first u32
* @second: second u32
* @key: the hsiphash key
*/
u32 hsiphash_2u32(const u32 first, const u32 second, const hsiphash_key_t *key)
{
u64 combined = (u64)second << 32 | first;
HPREAMBLE(8)
v3 ^= combined;
HSIPROUND;
v0 ^= combined;
HPOSTAMBLE
}
EXPORT_SYMBOL(hsiphash_2u32);
/**
* hsiphash_3u32 - compute 32-bit hsiphash PRF value of 3 u32
* @first: first u32
* @second: second u32
* @third: third u32
* @key: the hsiphash key
*/
u32 hsiphash_3u32(const u32 first, const u32 second, const u32 third,
const hsiphash_key_t *key)
{
u64 combined = (u64)second << 32 | first;
HPREAMBLE(12)
v3 ^= combined;
HSIPROUND;
v0 ^= combined;
b |= third;
HPOSTAMBLE
}
EXPORT_SYMBOL(hsiphash_3u32);
/**
* hsiphash_4u32 - compute 32-bit hsiphash PRF value of 4 u32
* @first: first u32
* @second: second u32
* @third: third u32
* @forth: forth u32
* @key: the hsiphash key
*/
u32 hsiphash_4u32(const u32 first, const u32 second, const u32 third,
const u32 forth, const hsiphash_key_t *key)
{
u64 combined = (u64)second << 32 | first;
HPREAMBLE(16)
v3 ^= combined;
HSIPROUND;
v0 ^= combined;
combined = (u64)forth << 32 | third;
v3 ^= combined;
HSIPROUND;
v0 ^= combined;
HPOSTAMBLE
}
EXPORT_SYMBOL(hsiphash_4u32);
#else
#define HSIPROUND \
do { \
v0 += v1; v1 = rol32(v1, 5); v1 ^= v0; v0 = rol32(v0, 16); \
v2 += v3; v3 = rol32(v3, 8); v3 ^= v2; \
v0 += v3; v3 = rol32(v3, 7); v3 ^= v0; \
v2 += v1; v1 = rol32(v1, 13); v1 ^= v2; v2 = rol32(v2, 16); \
} while (0)
#define HPREAMBLE(len) \
u32 v0 = 0; \
u32 v1 = 0; \
u32 v2 = 0x6c796765U; \
u32 v3 = 0x74656462U; \
u32 b = ((u32)(len)) << 24; \
v3 ^= key->key[1]; \
v2 ^= key->key[0]; \
v1 ^= key->key[1]; \
v0 ^= key->key[0];
#define HPOSTAMBLE \
v3 ^= b; \
HSIPROUND; \
v0 ^= b; \
v2 ^= 0xff; \
HSIPROUND; \
HSIPROUND; \
HSIPROUND; \
return v1 ^ v3;
#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
u32 __hsiphash_aligned(const void *data, size_t len, const hsiphash_key_t *key)
{
const u8 *end = data + len - (len % sizeof(u32));
const u8 left = len & (sizeof(u32) - 1);
u32 m;
HPREAMBLE(len)
for (; data != end; data += sizeof(u32)) {
m = le32_to_cpup(data);
v3 ^= m;
HSIPROUND;
v0 ^= m;
}
switch (left) {
case 3: b |= ((u32)end[2]) << 16; fallthrough;
case 2: b |= le16_to_cpup(data); break;
case 1: b |= end[0];
}
HPOSTAMBLE
}
EXPORT_SYMBOL(__hsiphash_aligned);
#endif
u32 __hsiphash_unaligned(const void *data, size_t len,
const hsiphash_key_t *key)
{
const u8 *end = data + len - (len % sizeof(u32));
const u8 left = len & (sizeof(u32) - 1);
u32 m;
HPREAMBLE(len)
for (; data != end; data += sizeof(u32)) {
m = get_unaligned_le32(data);
v3 ^= m;
HSIPROUND;
v0 ^= m;
}
switch (left) {
case 3: b |= ((u32)end[2]) << 16; fallthrough;
case 2: b |= get_unaligned_le16(end); break;
case 1: b |= end[0];
}
HPOSTAMBLE
}
EXPORT_SYMBOL(__hsiphash_unaligned);
/**
* hsiphash_1u32 - compute 32-bit hsiphash PRF value of a u32
* @first: first u32
* @key: the hsiphash key
*/
u32 hsiphash_1u32(const u32 first, const hsiphash_key_t *key)
{
HPREAMBLE(4)
v3 ^= first;
HSIPROUND;
v0 ^= first;
HPOSTAMBLE
}
EXPORT_SYMBOL(hsiphash_1u32);
/**
* hsiphash_2u32 - compute 32-bit hsiphash PRF value of 2 u32
* @first: first u32
* @second: second u32
* @key: the hsiphash key
*/
u32 hsiphash_2u32(const u32 first, const u32 second, const hsiphash_key_t *key)
{
HPREAMBLE(8)
v3 ^= first;
HSIPROUND;
v0 ^= first;
v3 ^= second;
HSIPROUND;
v0 ^= second;
HPOSTAMBLE
}
EXPORT_SYMBOL(hsiphash_2u32);
/**
* hsiphash_3u32 - compute 32-bit hsiphash PRF value of 3 u32
* @first: first u32
* @second: second u32
* @third: third u32
* @key: the hsiphash key
*/
u32 hsiphash_3u32(const u32 first, const u32 second, const u32 third,
const hsiphash_key_t *key)
{
HPREAMBLE(12)
v3 ^= first;
HSIPROUND;
v0 ^= first;
v3 ^= second;
HSIPROUND;
v0 ^= second;
v3 ^= third;
HSIPROUND;
v0 ^= third;
HPOSTAMBLE
}
EXPORT_SYMBOL(hsiphash_3u32);
/**
* hsiphash_4u32 - compute 32-bit hsiphash PRF value of 4 u32
* @first: first u32
* @second: second u32
* @third: third u32
* @forth: forth u32
* @key: the hsiphash key
*/
u32 hsiphash_4u32(const u32 first, const u32 second, const u32 third,
const u32 forth, const hsiphash_key_t *key)
{
HPREAMBLE(16)
v3 ^= first;
HSIPROUND;
v0 ^= first;
v3 ^= second;
HSIPROUND;
v0 ^= second;
v3 ^= third;
HSIPROUND;
v0 ^= third;
v3 ^= forth;
HSIPROUND;
v0 ^= forth;
HPOSTAMBLE
}
EXPORT_SYMBOL(hsiphash_4u32);
#endif
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