130 lines
3.3 KiB
C
130 lines
3.3 KiB
C
/*
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* Copyright (c) 2018 Apple Inc. All rights reserved.
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*
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* @APPLE_OSREFERENCE_LICENSE_HEADER_START@
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*
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* This file contains Original Code and/or Modifications of Original Code
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* as defined in and that are subject to the Apple Public Source License
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* Version 2.0 (the 'License'). You may not use this file except in
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* compliance with the License. The rights granted to you under the License
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* may not be used to create, or enable the creation or redistribution of,
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* unlawful or unlicensed copies of an Apple operating system, or to
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* circumvent, violate, or enable the circumvention or violation of, any
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* terms of an Apple operating system software license agreement.
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*
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* Please obtain a copy of the License at
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* http://www.opensource.apple.com/apsl/ and read it before using this file.
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*
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* The Original Code and all software distributed under the License are
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* distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
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* EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
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* INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
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* Please see the License for the specific language governing rights and
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* limitations under the License.
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*
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* @APPLE_OSREFERENCE_LICENSE_HEADER_END@
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*/
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#ifndef _OS_HASH_H_
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#define _OS_HASH_H_
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#if PRIVATE
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#include <os/base.h>
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__BEGIN_DECLS
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static inline uint32_t
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os_hash_jenkins_update(const void *data, size_t length, uint32_t hash)
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{
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const uint8_t *key = (const uint8_t *)data;
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for (size_t i = 0; i < length; i++) {
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hash += key[i];
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hash += (hash << 10);
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hash ^= (hash >> 6);
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}
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return hash;
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}
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static inline uint32_t
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os_hash_jenkins_finish(uint32_t hash)
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{
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hash += (hash << 3);
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hash ^= (hash >> 11);
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hash += (hash << 15);
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return hash;
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}
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/*!
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* @function os_hash_jenkins
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*
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* @brief
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* The original Jenkins "one at a time" hash.
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*
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* @discussion
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* TBD: There may be some value to unrolling here,
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* depending on the architecture.
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*
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* @param data
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* The address of the data to hash.
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*
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* @param length
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* The length of the data to hash
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*
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* @param seed
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* An optional hash seed (defaults to 0).
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*
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* @returns
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* The jenkins hash for this data.
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*/
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__attribute__((overloadable))
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static inline uint32_t
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os_hash_jenkins(const void *data, size_t length, uint32_t seed)
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{
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return os_hash_jenkins_finish(os_hash_jenkins_update(data, length, seed));
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}
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__attribute__((overloadable))
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static inline uint32_t
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os_hash_jenkins(const void *data, size_t length)
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{
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return os_hash_jenkins(data, length, 0);
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}
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/*!
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* @function os_hash_kernel_pointer
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*
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* @brief
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* Hashes a pointer from a zone.
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*
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* @discussion
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* This is a really cheap and fast hash that will behave well for pointers
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* allocated by the kernel.
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*
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* This should be not used for untrusted pointer values from userspace,
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* or cases when the pointer is somehow under the control of userspace.
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*
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* This hash function utilizes knowledge about the span of the kernel
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* address space and inherent alignment of zalloc/kalloc.
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*
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* @param pointer
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* The pointer to hash.
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*
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* @returns
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* The hash for this pointer.
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*/
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static inline uint32_t
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os_hash_kernel_pointer(const void *pointer)
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{
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uintptr_t key = (uintptr_t)pointer >> 4;
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key *= 0x5052acdb;
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return (uint32_t)key ^ __builtin_bswap32((uint32_t)key);
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}
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__END_DECLS
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#endif // PRIVATE
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#endif // _OS_HASH_H_
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