/*      $OpenBSD: mmap_hint.c,v 1.7 2026/02/26 14:05:25 cludwig Exp $   */
/*
 * Copyright (c) 2011 Ariane van der Steldt <ariane@stack.nl>
 *
 * 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>  /* PAGE_SIZE PAGE_MASK */
#include <sys/types.h>
#include <sys/mman.h>
#include <sys/tree.h>
#include <machine/pmap.h>
#include <machine/vmparam.h>
#include <err.h>
#include <sysexits.h>
#include <stdio.h>

#define MAX_HINT_DIST   (2UL * 1024 * 1024 * 1024)

int     errors = 0;

void *
mmap_hint(void *hint)
{
        void    *p;
        size_t   delta;

        p = mmap(hint, 1, PROT_READ|PROT_WRITE, MAP_ANON|MAP_PRIVATE, -1, 0);
        if (p == MAP_FAILED) {
                warn("mmap(addr=%p, len=1) failed", hint);
                errors++;
                return MAP_FAILED;
        } else if (p == NULL) {
                warnx("mmap(addr=%p, len=1) mapped at address 0", hint);
                errors++;
                return MAP_FAILED;
        } else
                fprintf(stderr, "    -> %p\n", p);

        if (hint > p)
                delta = hint - p;
        else
                delta = p - hint;

        if (hint != NULL && hint < (void *)VM_MAXUSER_ADDRESS &&
            delta > MAX_HINT_DIST) {
                warnx("hinted allocation more than %#zx bytes away from hint: "
                    "hint %p, result %p", delta, hint, p);
                errors++;
                return MAP_FAILED;
        }
        return p;
}

int
main()
{
        void    *p, *hint;

        /* Check that unhinted allocation works properly. */
        hint = NULL;
        fprintf(stderr, "1: Checking hint %p mmap\n", hint);
        p = mmap_hint(hint);

        /* Check hinted allocation at top of map. */
        hint = (void *)((VM_MAXUSER_ADDRESS & ~PAGE_MASK) - PAGE_SIZE);
        fprintf(stderr, "2: Checking hint page below "
            "VM_MAXUSER_ADDRESS %p mmap\n", hint);
        p = mmap_hint(hint);

        /* Check hinted allocation at bottom of map. */
        hint = (void *)VM_MIN_ADDRESS;
        fprintf(stderr, "3: Checking hint VM_MIN_ADDRESS %p mmap\n", hint);
        p = mmap_hint(hint);

        /*
         * Check that hinted allocation doesn't overwrite existing allocation.
         */
        if (p == MAP_FAILED) {
                fprintf(stderr, "4: Skipping test: required previous test "
                    "to succeed");
                goto skip4;
        }
        hint = p;
        fprintf(stderr, "4: Checking hint %p mmap, which is in use\n", hint);
        p = mmap_hint(hint);
        if (p == hint) {
                warnx("hinted allocation %p overwrites previous allocation %p",
                    hint, p);
                errors++;
        }

skip4:
        /* Check hinted allocation below PAGE_SIZE. */
        hint = (void *)1UL;
        fprintf(stderr, "5: Checking hint below PAGE_SIZE %p mmap\n", hint);
        p = mmap_hint(hint);

        /* Check hinted allocation above userspace. */
        hint = (void *)VM_MAX_ADDRESS;
        fprintf(stderr, "6: Checking hint at VM_MAX_ADDRESS %p mmap\n", hint);
        p = mmap_hint(hint);

        return errors;
}