cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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fncache.c (1243B)

      1// SPDX-License-Identifier: GPL-2.0-only
      2/* Manage a cache of file names' existence */
      3#include <stdlib.h>
      4#include <unistd.h>
      5#include <string.h>
      6#include <linux/list.h>
      7#include "fncache.h"
      8
      9struct fncache {
     10	struct hlist_node nd;
     11	bool res;
     12	char name[];
     13};
     14
     15#define FNHSIZE 61
     16
     17static struct hlist_head fncache_hash[FNHSIZE];
     18
     19unsigned shash(const unsigned char *s)
     20{
     21	unsigned h = 0;
     22	while (*s)
     23		h = 65599 * h + *s++;
     24	return h ^ (h >> 16);
     25}
     26
     27static bool lookup_fncache(const char *name, bool *res)
     28{
     29	int h = shash((const unsigned char *)name) % FNHSIZE;
     30	struct fncache *n;
     31
     32	hlist_for_each_entry(n, &fncache_hash[h], nd) {
     33		if (!strcmp(n->name, name)) {
     34			*res = n->res;
     35			return true;
     36		}
     37	}
     38	return false;
     39}
     40
     41static void update_fncache(const char *name, bool res)
     42{
     43	struct fncache *n = malloc(sizeof(struct fncache) + strlen(name) + 1);
     44	int h = shash((const unsigned char *)name) % FNHSIZE;
     45
     46	if (!n)
     47		return;
     48	strcpy(n->name, name);
     49	n->res = res;
     50	hlist_add_head(&n->nd, &fncache_hash[h]);
     51}
     52
     53/* No LRU, only use when bounded in some other way. */
     54bool file_available(const char *name)
     55{
     56	bool res;
     57
     58	if (lookup_fncache(name, &res))
     59		return res;
     60	res = access(name, R_OK) == 0;
     61	update_fncache(name, res);
     62	return res;
     63}