/*      $OpenBSD: subr_poison.c,v 1.15 2022/08/14 01:58:28 jsg Exp $ */
/*
 * Copyright (c) 2013 Ted Unangst <tedu@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <sys/param.h>

/*
 * The POISON is used as known text to copy into free objects so
 * that modifications after frees can be detected.
 */
#ifdef DEADBEEF0
#define POISON0 ((unsigned) DEADBEEF0)
#else
#define POISON0 ((unsigned) 0xdeadbeef)
#endif
#ifdef DEADBEEF1
#define POISON1 ((unsigned) DEADBEEF1)
#else
#define POISON1 ((unsigned) 0xdeafbead)
#endif
#define POISON_SIZE     64

uint32_t
poison_value(void *v)
{
        ulong l = (u_long)v;

        l = l >> PAGE_SHIFT;

        switch (l & 3) {
        case 0:
                return POISON0;
        case 1:
                return POISON1;
        case 2:
                return (POISON0 & 0xffff0000) | (~POISON0 & 0x0000ffff);
        case 3:
                return (POISON1 & 0xffff0000) | (~POISON1 & 0x0000ffff);
        }
        return 0;
}

void
poison_mem(void *v, size_t len)
{
        uint32_t *ip = v;
        size_t i;
        uint32_t poison;

        poison = poison_value(v);

        if (len > POISON_SIZE)
                len = POISON_SIZE;
        len = len / sizeof(*ip);
        for (i = 0; i < len; i++)
                ip[i] = poison;
}

int
poison_check(void *v, size_t len, size_t *pidx, uint32_t *pval)
{
        uint32_t *ip = v;
        size_t i;
        uint32_t poison;

        poison = poison_value(v);

        if (len > POISON_SIZE)
                len = POISON_SIZE;
        len = len / sizeof(*ip);
        for (i = 0; i < len; i++) {
                if (ip[i] != poison) {
                        *pidx = i;
                        *pval = poison;
                        return 1;
                }
        }
        return 0;
}