1 /* $OpenBSD: mmap_hint.c,v 1.6 2021/12/13 16:56:50 deraadt Exp $ */
2 /*
3 * Copyright (c) 2011 Ariane van der Steldt <ariane@stack.nl>
4 *
5 * Permission to use, copy, modify, and distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
8 *
9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16 */
17
18 #include <sys/param.h> /* PAGE_SIZE PAGE_MASK */
19 #include <sys/types.h>
20 #include <sys/mman.h>
21 #include <sys/tree.h>
22 #include <machine/pmap.h>
23 #include <machine/vmparam.h>
24 #include <err.h>
25 #include <sysexits.h>
26 #include <stdio.h>
27
28 #define MAX_HINT_DIST (2UL * 1024 * 1024 * 1024)
29
30 int errors = 0;
31
32 void *
mmap_hint(void * hint)33 mmap_hint(void *hint)
34 {
35 void *p;
36 size_t delta;
37
38 p = mmap(hint, 1, PROT_READ|PROT_WRITE, MAP_ANON|MAP_PRIVATE, -1, 0);
39 if (p == MAP_FAILED) {
40 warn("mmap(addr=%p, len=1) failed", hint);
41 errors++;
42 return MAP_FAILED;
43 } else if (p == NULL) {
44 warnx("mmap(addr=%p, len=1) mapped at address 0", hint);
45 errors++;
46 return MAP_FAILED;
47 } else
48 fprintf(stderr, " -> %p\n", p);
49
50 if (hint > p)
51 delta = hint - p;
52 else
53 delta = p - hint;
54
55 if (hint != NULL && delta > MAX_HINT_DIST) {
56 warnx("hinted allocation more than %#zx bytes away from hint: "
57 "hint %p, result %p", delta, hint, p);
58 errors++;
59 return MAP_FAILED;
60 }
61 return p;
62 }
63
64 int
main()65 main()
66 {
67 void *p, *hint;
68
69 /* Check that unhinted allocation works properly. */
70 hint = NULL;
71 fprintf(stderr, "1: Checking hint %p mmap\n", hint);
72 p = mmap_hint(hint);
73
74 /* Check hinted allocation at top of map. */
75 hint = (void *)((VM_MAXUSER_ADDRESS & ~PAGE_MASK) - PAGE_SIZE);
76 fprintf(stderr, "2: Checking hint page below "
77 "VM_MAXUSER_ADDRESS %p mmap\n", hint);
78 p = mmap_hint(hint);
79
80 /* Check hinted allocation at bottom of map. */
81 hint = (void *)VM_MIN_ADDRESS;
82 fprintf(stderr, "3: Checking hint VM_MIN_ADDRESS %p mmap\n", hint);
83 p = mmap_hint(hint);
84
85 /*
86 * Check that hinted allocation doesn't overwrite existing allocation.
87 */
88 if (p == MAP_FAILED) {
89 fprintf(stderr, "4: Skipping test: required previous test "
90 "to succeed");
91 goto skip4;
92 }
93 hint = p;
94 fprintf(stderr, "4: Checking hint %p mmap, which is in use\n", hint);
95 p = mmap_hint(hint);
96 if (p == hint) {
97 warnx("hinted allocation %p overwrites previous allocation %p",
98 hint, p);
99 errors++;
100 }
101
102 skip4:
103 return errors;
104 }
105