33ebc1932a
This function, based on murmurhash3, has much better distribution than the original. Using the current default of 2048 buckets, there are many fewer collisions: Before: 101421 entries and 2048/2048 buckets used, longest chain length 374 After: 101421 entries and 2048/2048 buckets used, longest chain length 81 The difference becomes much more significant when buckets are increased. A naive attempt to expand the current function to larger outputs doesn't yield any significant improvement; so this function is a prerequisite for increasing the bucket size. sds: Adapted from the original patches for libsepol to the kernel. Signed-off-by: John Brooks <john.brooks@jolla.com> Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov> Signed-off-by: Paul Moore <pmoore@redhat.com>
94 lines
2.9 KiB
C
94 lines
2.9 KiB
C
/*
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* An access vector table (avtab) is a hash table
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* of access vectors and transition types indexed
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* by a type pair and a class. An access vector
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* table is used to represent the type enforcement
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* tables.
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*
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* Author : Stephen Smalley, <sds@epoch.ncsc.mil>
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*/
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/* Updated: Frank Mayer <mayerf@tresys.com> and Karl MacMillan <kmacmillan@tresys.com>
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*
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* Added conditional policy language extensions
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*
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* Copyright (C) 2003 Tresys Technology, LLC
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, version 2.
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*
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* Updated: Yuichi Nakamura <ynakam@hitachisoft.jp>
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* Tuned number of hash slots for avtab to reduce memory usage
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*/
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#ifndef _SS_AVTAB_H_
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#define _SS_AVTAB_H_
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#include <linux/flex_array.h>
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struct avtab_key {
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u16 source_type; /* source type */
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u16 target_type; /* target type */
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u16 target_class; /* target object class */
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#define AVTAB_ALLOWED 0x0001
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#define AVTAB_AUDITALLOW 0x0002
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#define AVTAB_AUDITDENY 0x0004
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#define AVTAB_AV (AVTAB_ALLOWED | AVTAB_AUDITALLOW | AVTAB_AUDITDENY)
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#define AVTAB_TRANSITION 0x0010
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#define AVTAB_MEMBER 0x0020
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#define AVTAB_CHANGE 0x0040
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#define AVTAB_TYPE (AVTAB_TRANSITION | AVTAB_MEMBER | AVTAB_CHANGE)
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#define AVTAB_ENABLED_OLD 0x80000000 /* reserved for used in cond_avtab */
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#define AVTAB_ENABLED 0x8000 /* reserved for used in cond_avtab */
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u16 specified; /* what field is specified */
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};
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struct avtab_datum {
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u32 data; /* access vector or type value */
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};
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struct avtab_node {
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struct avtab_key key;
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struct avtab_datum datum;
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struct avtab_node *next;
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};
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struct avtab {
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struct flex_array *htable;
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u32 nel; /* number of elements */
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u32 nslot; /* number of hash slots */
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u32 mask; /* mask to compute hash func */
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};
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int avtab_init(struct avtab *);
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int avtab_alloc(struct avtab *, u32);
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struct avtab_datum *avtab_search(struct avtab *h, struct avtab_key *k);
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void avtab_destroy(struct avtab *h);
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void avtab_hash_eval(struct avtab *h, char *tag);
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struct policydb;
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int avtab_read_item(struct avtab *a, void *fp, struct policydb *pol,
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int (*insert)(struct avtab *a, struct avtab_key *k,
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struct avtab_datum *d, void *p),
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void *p);
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int avtab_read(struct avtab *a, void *fp, struct policydb *pol);
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int avtab_write_item(struct policydb *p, struct avtab_node *cur, void *fp);
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int avtab_write(struct policydb *p, struct avtab *a, void *fp);
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struct avtab_node *avtab_insert_nonunique(struct avtab *h, struct avtab_key *key,
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struct avtab_datum *datum);
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struct avtab_node *avtab_search_node(struct avtab *h, struct avtab_key *key);
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struct avtab_node *avtab_search_node_next(struct avtab_node *node, int specified);
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void avtab_cache_init(void);
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void avtab_cache_destroy(void);
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#define MAX_AVTAB_HASH_BITS 11
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#define MAX_AVTAB_HASH_BUCKETS (1 << MAX_AVTAB_HASH_BITS)
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#endif /* _SS_AVTAB_H_ */
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