summaryrefslogtreecommitdiffstats
path: root/tools/testing/selftests/mm/hugepage-mremap.c
blob: cabd0084f57b8e5c32c987185391c136ee4579ec (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
// SPDX-License-Identifier: GPL-2.0
/*
 * hugepage-mremap:
 *
 * Example of remapping huge page memory in a user application using the
 * mremap system call.  The path to a file in a hugetlbfs filesystem must
 * be passed as the last argument to this test.  The amount of memory used
 * by this test in MBs can optionally be passed as an argument.  If no memory
 * amount is passed, the default amount is 10MB.
 *
 * To make sure the test triggers pmd sharing and goes through the 'unshare'
 * path in the mremap code use 1GB (1024) or more.
 */

#define _GNU_SOURCE
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/mman.h>
#include <errno.h>
#include <fcntl.h> /* Definition of O_* constants */
#include <sys/syscall.h> /* Definition of SYS_* constants */
#include <linux/userfaultfd.h>
#include <sys/ioctl.h>
#include <string.h>
#include <stdbool.h>
#include "vm_util.h"

#define DEFAULT_LENGTH_MB 10UL
#define MB_TO_BYTES(x) (x * 1024 * 1024)

#define PROTECTION (PROT_READ | PROT_WRITE | PROT_EXEC)
#define FLAGS (MAP_SHARED | MAP_ANONYMOUS)

static void check_bytes(char *addr)
{
	printf("First hex is %x\n", *((unsigned int *)addr));
}

static void write_bytes(char *addr, size_t len)
{
	unsigned long i;

	for (i = 0; i < len; i++)
		*(addr + i) = (char)i;
}

static int read_bytes(char *addr, size_t len)
{
	unsigned long i;

	check_bytes(addr);
	for (i = 0; i < len; i++)
		if (*(addr + i) != (char)i) {
			printf("Mismatch at %lu\n", i);
			return 1;
		}
	return 0;
}

static void register_region_with_uffd(char *addr, size_t len)
{
	long uffd; /* userfaultfd file descriptor */
	struct uffdio_api uffdio_api;

	/* Create and enable userfaultfd object. */

	uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK);
	if (uffd == -1) {
		perror("userfaultfd");
		exit(1);
	}

	uffdio_api.api = UFFD_API;
	uffdio_api.features = 0;
	if (ioctl(uffd, UFFDIO_API, &uffdio_api) == -1) {
		perror("ioctl-UFFDIO_API");
		exit(1);
	}

	/* Create a private anonymous mapping. The memory will be
	 * demand-zero paged--that is, not yet allocated. When we
	 * actually touch the memory, it will be allocated via
	 * the userfaultfd.
	 */

	addr = mmap(NULL, len, PROT_READ | PROT_WRITE,
		    MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
	if (addr == MAP_FAILED) {
		perror("mmap");
		exit(1);
	}

	printf("Address returned by mmap() = %p\n", addr);

	/* Register the memory range of the mapping we just created for
	 * handling by the userfaultfd object. In mode, we request to track
	 * missing pages (i.e., pages that have not yet been faulted in).
	 */
	if (uffd_register(uffd, addr, len, true, false, false)) {
		perror("ioctl-UFFDIO_REGISTER");
		exit(1);
	}
}

int main(int argc, char *argv[])
{
	size_t length = 0;
	int ret = 0, fd;

	if (argc >= 2 && !strcmp(argv[1], "-h")) {
		printf("Usage: %s [length_in_MB]\n", argv[0]);
		exit(1);
	}

	/* Read memory length as the first arg if valid, otherwise fallback to
	 * the default length.
	 */
	if (argc >= 2)
		length = (size_t)atoi(argv[1]);
	else
		length = DEFAULT_LENGTH_MB;

	length = MB_TO_BYTES(length);
	fd = memfd_create(argv[0], MFD_HUGETLB);
	if (fd < 0) {
		perror("Open failed");
		exit(1);
	}

	/* mmap to a PUD aligned address to hopefully trigger pmd sharing. */
	unsigned long suggested_addr = 0x7eaa40000000;
	void *haddr = mmap((void *)suggested_addr, length, PROTECTION,
			   MAP_HUGETLB | MAP_SHARED | MAP_POPULATE, fd, 0);
	printf("Map haddr: Returned address is %p\n", haddr);
	if (haddr == MAP_FAILED) {
		perror("mmap1");
		exit(1);
	}

	/* mmap again to a dummy address to hopefully trigger pmd sharing. */
	suggested_addr = 0x7daa40000000;
	void *daddr = mmap((void *)suggested_addr, length, PROTECTION,
			   MAP_HUGETLB | MAP_SHARED | MAP_POPULATE, fd, 0);
	printf("Map daddr: Returned address is %p\n", daddr);
	if (daddr == MAP_FAILED) {
		perror("mmap3");
		exit(1);
	}

	suggested_addr = 0x7faa40000000;
	void *vaddr =
		mmap((void *)suggested_addr, length, PROTECTION, FLAGS, -1, 0);
	printf("Map vaddr: Returned address is %p\n", vaddr);
	if (vaddr == MAP_FAILED) {
		perror("mmap2");
		exit(1);
	}

	register_region_with_uffd(haddr, length);

	void *addr = mremap(haddr, length, length,
			    MREMAP_MAYMOVE | MREMAP_FIXED, vaddr);
	if (addr == MAP_FAILED) {
		perror("mremap");
		exit(1);
	}

	printf("Mremap: Returned address is %p\n", addr);
	check_bytes(addr);
	write_bytes(addr, length);
	ret = read_bytes(addr, length);

	munmap(addr, length);

	addr = mremap(addr, length, length, 0);
	if (addr != MAP_FAILED) {
		printf("mremap: Expected failure, but call succeeded\n");
		exit(1);
	}

	close(fd);

	return ret;
}