linux/security/selinux/ss/symtab.c
Ondrej Mosnacek 24def7bb92 selinux: prepare for inlining of hashtab functions
Refactor searching and inserting into hashtabs to pave the way for
converting hashtab_search() and hashtab_insert() to inline functions in
the next patch. This will avoid indirect calls and allow the compiler to
better optimize individual callers, leading to a significant performance
improvement.

In order to avoid the indirect calls, the key hashing and comparison
callbacks need to be extracted from the hashtab struct and passed
directly to hashtab_search()/_insert() by the callers so that the
callback address is always known at compile time. The kernel's
rhashtable library (<linux/rhashtable*.h>) does the same thing.

This of course makes the hashtab functions slightly easier to misuse by
passing a wrong callback set, but unfortunately there is no better way
to implement a hash table that is both generic and efficient in C. This
patch tries to somewhat mitigate this by only calling the hashtab
functions in the same file where the corresponding callbacks are
defined (wrapping them into more specialized functions as needed).

Note that this patch doesn't bring any benefit without also moving the
definitions of hashtab_search() and -_insert() to the header file, which
is done in a follow-up patch for easier review of the hashtab.c changes
in this patch.

Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Acked-by: Stephen Smalley <stephen.smalley.work@gmail.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
2020-07-09 19:05:36 -04:00

55 lines
1.1 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* Implementation of the symbol table type.
*
* Author : Stephen Smalley, <sds@tycho.nsa.gov>
*/
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/errno.h>
#include "symtab.h"
static unsigned int symhash(const void *key)
{
const char *p, *keyp;
unsigned int size;
unsigned int val;
val = 0;
keyp = key;
size = strlen(keyp);
for (p = keyp; (p - keyp) < size; p++)
val = (val << 4 | (val >> (8*sizeof(unsigned int)-4))) ^ (*p);
return val;
}
static int symcmp(const void *key1, const void *key2)
{
const char *keyp1, *keyp2;
keyp1 = key1;
keyp2 = key2;
return strcmp(keyp1, keyp2);
}
static const struct hashtab_key_params symtab_key_params = {
.hash = symhash,
.cmp = symcmp,
};
int symtab_init(struct symtab *s, unsigned int size)
{
s->nprim = 0;
return hashtab_init(&s->table, size);
}
int symtab_insert(struct symtab *s, char *name, void *datum)
{
return hashtab_insert(&s->table, name, datum, symtab_key_params);
}
void *symtab_search(struct symtab *s, const char *name)
{
return hashtab_search(&s->table, name, symtab_key_params);
}