1// SPDX-License-Identifier: LGPL-2.1-or-later
2/*
3 * Copyright (C) 2005-2006 David Gibson & Adam Litke, IBM Corporation.
4 * Copyright (C) 2006 Hugh Dickins <hugh@veritas.com>
5 * Author: David Gibson & Adam Litke
6 */
7
8/*\
9 * [Descripiton]
10 *
11 * At one stage, a misconversion of hugetlb_vmtruncate_list to a
12 * prio_tree meant that on 32-bit machines, truncates at or above 4GB
13 * could truncate lower pages, resulting in BUG_ON()s.
14 *
15 * WARNING: The offsets and addresses used within are specifically
16 * calculated to trigger the bug as it existed.  Don't mess with them
17 * unless you *really* know what you're doing.
18 *
19 * The kernel bug in question was fixed with commit
20 * 856fc2950555.
21 */
22
23#define _GNU_SOURCE
24#include <stdio.h>
25#include <sys/mount.h>
26#include <limits.h>
27#include <sys/param.h>
28#include <sys/types.h>
29
30#include "hugetlb.h"
31
32#define RANDOM_CONSTANT	0x1234ABCD
33#define MNTPOINT "hugetlbfs/"
34static int page_size;
35static long hpage_size;
36static int  fd = -1;
37
38static void run_test(void)
39{
40	off_t buggy_offset;
41	void *p, *q;
42	volatile int *pi;
43	int err;
44
45	/*
46	 * First, we make a 2 page sane hugepage mapping.  Then we
47	 * memset() it to ensure that the ptes are instantiated for
48	 * it.  Then we attempt to replace the second half of the map
49	 * with one at a bogus offset.  We leave the first page of
50	 * sane mapping in place to ensure that the corresponding
51	 * pud/pmd/whatever entries aren't cleaned away.  It's those
52	 * bad entries which can trigger bad_pud() checks if the
53	 * backout path for the bogus mapping is buggy, which it was
54	 * in some kernels.
55	 */
56	tst_res(TINFO, "Initial free hugepages: %lu",
57		SAFE_READ_MEMINFO(MEMINFO_HPAGE_FREE));
58
59	/* First get arena of three hpages size, at file offset 4GB */
60	p = SAFE_MMAP(NULL, 2*hpage_size, PROT_READ|PROT_WRITE, MAP_PRIVATE, fd, 0);
61
62	tst_res(TINFO, "After Mapping reference map, Free hugepages: %lu",
63		SAFE_READ_MEMINFO(MEMINFO_HPAGE_FREE));
64	tst_res(TINFO, "Mapped Address Range: %p-%p", p, p+2*hpage_size-1);
65
66	memset(p, 0, 2*hpage_size);
67	pi = p;
68	*pi = RANDOM_CONSTANT;
69
70	tst_res(TINFO, "After instantiate the pages, Free hugepages: %lu",
71		   SAFE_READ_MEMINFO(MEMINFO_HPAGE_FREE));
72
73	/*
74	 * Toggle the permissions on the first page.  This forces TLB
75	 * entries (including hash page table on powerpc) to be
76	 * flushed, so that the page tables must be accessed for the
77	 * test further down.  In the buggy case, those page tables
78	 * can get thrown away by a pud_clear()
79	 */
80	err = mprotect(p, hpage_size, PROT_READ);
81	if (err)
82		tst_brk(TBROK|TERRNO, "mprotect(%p, 0x%lx, PROT_READ)", p, hpage_size);
83
84	/* Replace top hpage by hpage mapping at confusing file offset */
85	buggy_offset = page_size;
86	tst_res(TINFO, "Replacing map at %p with map from offset 0x%lx...",
87	       p + hpage_size, (unsigned long)buggy_offset);
88	q = mmap(p + hpage_size, hpage_size, PROT_READ|PROT_WRITE,
89		 MAP_FIXED|MAP_PRIVATE, fd, buggy_offset);
90	if (q != MAP_FAILED) {
91		tst_res(TFAIL|TERRNO, "bogus offset mmap() succeeded at %p", q);
92		goto cleanup;
93	}
94	if (errno != EINVAL) {
95		tst_res(TFAIL|TERRNO, "bogus mmap() failed should be \"%s\" but it is",
96		     tst_strerrno(EINVAL));
97		goto cleanup;
98	}
99
100	tst_res(TINFO, "After Mapping with buggy offset, Free hugepages: %lu",
101		SAFE_READ_MEMINFO(MEMINFO_HPAGE_FREE));
102
103	if (*pi != RANDOM_CONSTANT) {
104		tst_res(TFAIL, "Pre-existing mapping clobbered: %x instead of %x",
105		     *pi, RANDOM_CONSTANT);
106		goto cleanup;
107	}
108
109	/*
110	 * The real test is whether we got a bad_pud() or similar
111	 * during the run.  The check above, combined with the earlier
112	 * mprotect()s to flush the TLB are supposed to catch it, but
113	 * it's hard to be certain.  Once bad_pud() is called
114	 * behaviour can be very strange.
115	 */
116
117	tst_res(TPASS, "Successful but inconclusive");
118cleanup:
119	SAFE_MUNMAP(p, 2*hpage_size);
120}
121
122static void setup(void)
123{
124	page_size = getpagesize();
125	hpage_size = SAFE_READ_MEMINFO("Hugepagesize:")*1024;
126	fd = tst_creat_unlinked(MNTPOINT, 0);
127}
128
129static void cleanup(void)
130{
131	if (fd >= 0)
132		SAFE_CLOSE(fd);
133}
134
135static struct tst_test test = {
136	.tags = (struct tst_tag[]) {
137		{"linux-git", "856fc2950555"},
138		{}
139	},
140	.needs_root = 1,
141	.mntpoint = MNTPOINT,
142	.needs_hugetlbfs = 1,
143	.setup = setup,
144	.cleanup = cleanup,
145	.test_all = run_test,
146	.hugepages = {4, TST_NEEDS},
147};
148