lib/siphash.c

Source file repositories/reference/linux-study-clean/lib/siphash.c

File Facts

System
Linux kernel
Corpus path
lib/siphash.c
Extension
.c
Size
11847 bytes
Lines
539
Domain
Kernel Services
Bucket
lib
Inferred role
Kernel Services: exported/initcall integration point
Status
integration implementation candidate

Why This File Exists

Shared kernel service surface used by multiple subsystems, including helpers, cryptography, virtualization support, and async I/O infrastructure.

Dependency Surface

Detected Declarations

Annotated Snippet

// SPDX-License-Identifier: (GPL-2.0-only OR BSD-3-Clause)
/* Copyright (C) 2016-2022 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
 *
 * 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 <linux/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 SIPHASH_PERMUTATION(v0, v1, v2, v3)

#define PREAMBLE(len) \
	u64 v0 = SIPHASH_CONST_0; \
	u64 v1 = SIPHASH_CONST_1; \
	u64 v2 = SIPHASH_CONST_2; \
	u64 v3 = SIPHASH_CONST_3; \
	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;

Annotation

Implementation Notes