1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * hugepage-mremap:
4 *
5 * Example of remapping huge page memory in a user application using the
6 * mremap system call. The path to a file in a hugetlbfs filesystem must
7 * be passed as the last argument to this test. The amount of memory used
8 * by this test in MBs can optionally be passed as an argument. If no memory
9 * amount is passed, the default amount is 10MB.
10 *
11 * To make sure the test triggers pmd sharing and goes through the 'unshare'
12 * path in the mremap code use 1GB (1024) or more.
13 */
14
15 #define _GNU_SOURCE
16 #include <stdlib.h>
17 #include <stdio.h>
18 #include <unistd.h>
19 #include <sys/mman.h>
20 #include <errno.h>
21 #include <fcntl.h> /* Definition of O_* constants */
22 #include <sys/syscall.h> /* Definition of SYS_* constants */
23 #include <linux/userfaultfd.h>
24 #include <sys/ioctl.h>
25 #include <string.h>
26 #include <stdbool.h>
27 #include "../kselftest.h"
28 #include "vm_util.h"
29
30 #define DEFAULT_LENGTH_MB 10UL
31 #define MB_TO_BYTES(x) (x * 1024 * 1024)
32
33 #define PROTECTION (PROT_READ | PROT_WRITE | PROT_EXEC)
34 #define FLAGS (MAP_SHARED | MAP_ANONYMOUS)
35
check_bytes(char * addr)36 static void check_bytes(char *addr)
37 {
38 ksft_print_msg("First hex is %x\n", *((unsigned int *)addr));
39 }
40
write_bytes(char * addr,size_t len)41 static void write_bytes(char *addr, size_t len)
42 {
43 unsigned long i;
44
45 for (i = 0; i < len; i++)
46 *(addr + i) = (char)i;
47 }
48
read_bytes(char * addr,size_t len)49 static int read_bytes(char *addr, size_t len)
50 {
51 unsigned long i;
52
53 check_bytes(addr);
54 for (i = 0; i < len; i++)
55 if (*(addr + i) != (char)i) {
56 ksft_print_msg("Mismatch at %lu\n", i);
57 return 1;
58 }
59 return 0;
60 }
61
register_region_with_uffd(char * addr,size_t len)62 static void register_region_with_uffd(char *addr, size_t len)
63 {
64 long uffd; /* userfaultfd file descriptor */
65 struct uffdio_api uffdio_api;
66
67 /* Create and enable userfaultfd object. */
68 uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK);
69 if (uffd == -1) {
70 switch (errno) {
71 case EPERM:
72 ksft_exit_skip("Insufficient permissions, try running as root.\n");
73 break;
74 case ENOSYS:
75 ksft_exit_skip("userfaultfd is not supported/not enabled.\n");
76 break;
77 default:
78 ksft_exit_fail_msg("userfaultfd failed with %s\n", strerror(errno));
79 break;
80 }
81 }
82
83 uffdio_api.api = UFFD_API;
84 uffdio_api.features = 0;
85 if (ioctl(uffd, UFFDIO_API, &uffdio_api) == -1)
86 ksft_exit_fail_msg("ioctl-UFFDIO_API: %s\n", strerror(errno));
87
88 /* Create a private anonymous mapping. The memory will be
89 * demand-zero paged--that is, not yet allocated. When we
90 * actually touch the memory, it will be allocated via
91 * the userfaultfd.
92 */
93
94 addr = mmap(NULL, len, PROT_READ | PROT_WRITE,
95 MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
96 if (addr == MAP_FAILED)
97 ksft_exit_fail_msg("mmap: %s\n", strerror(errno));
98
99 ksft_print_msg("Address returned by mmap() = %p\n", addr);
100
101 /* Register the memory range of the mapping we just created for
102 * handling by the userfaultfd object. In mode, we request to track
103 * missing pages (i.e., pages that have not yet been faulted in).
104 */
105 if (uffd_register(uffd, addr, len, true, false, false))
106 ksft_exit_fail_msg("ioctl-UFFDIO_REGISTER: %s\n", strerror(errno));
107 }
108
main(int argc,char * argv[])109 int main(int argc, char *argv[])
110 {
111 size_t length = 0;
112 int ret = 0, fd;
113
114 ksft_print_header();
115 ksft_set_plan(1);
116
117 if (argc >= 2 && !strcmp(argv[1], "-h"))
118 ksft_exit_fail_msg("Usage: %s [length_in_MB]\n", argv[0]);
119
120 /* Read memory length as the first arg if valid, otherwise fallback to
121 * the default length.
122 */
123 if (argc >= 2)
124 length = (size_t)atoi(argv[1]);
125 else
126 length = DEFAULT_LENGTH_MB;
127
128 length = MB_TO_BYTES(length);
129 fd = memfd_create(argv[0], MFD_HUGETLB);
130 if (fd < 0)
131 ksft_exit_fail_msg("Open failed: %s\n", strerror(errno));
132
133 /* mmap to a PUD aligned address to hopefully trigger pmd sharing. */
134 unsigned long suggested_addr = 0x7eaa40000000;
135 void *haddr = mmap((void *)suggested_addr, length, PROTECTION,
136 MAP_HUGETLB | MAP_SHARED | MAP_POPULATE, fd, 0);
137 ksft_print_msg("Map haddr: Returned address is %p\n", haddr);
138 if (haddr == MAP_FAILED)
139 ksft_exit_fail_msg("mmap1: %s\n", strerror(errno));
140
141 /* mmap again to a dummy address to hopefully trigger pmd sharing. */
142 suggested_addr = 0x7daa40000000;
143 void *daddr = mmap((void *)suggested_addr, length, PROTECTION,
144 MAP_HUGETLB | MAP_SHARED | MAP_POPULATE, fd, 0);
145 ksft_print_msg("Map daddr: Returned address is %p\n", daddr);
146 if (daddr == MAP_FAILED)
147 ksft_exit_fail_msg("mmap3: %s\n", strerror(errno));
148
149 suggested_addr = 0x7faa40000000;
150 void *vaddr =
151 mmap((void *)suggested_addr, length, PROTECTION, FLAGS, -1, 0);
152 ksft_print_msg("Map vaddr: Returned address is %p\n", vaddr);
153 if (vaddr == MAP_FAILED)
154 ksft_exit_fail_msg("mmap2: %s\n", strerror(errno));
155
156 register_region_with_uffd(haddr, length);
157
158 void *addr = mremap(haddr, length, length,
159 MREMAP_MAYMOVE | MREMAP_FIXED, vaddr);
160 if (addr == MAP_FAILED)
161 ksft_exit_fail_msg("mremap: %s\n", strerror(errno));
162
163 ksft_print_msg("Mremap: Returned address is %p\n", addr);
164 check_bytes(addr);
165 write_bytes(addr, length);
166 ret = read_bytes(addr, length);
167
168 munmap(addr, length);
169
170 addr = mremap(addr, length, length, 0);
171 if (addr != MAP_FAILED)
172 ksft_exit_fail_msg("mremap: Expected failure, but call succeeded\n");
173
174 close(fd);
175
176 ksft_test_result(!ret, "Read same data\n");
177 ksft_exit(!ret);
178 }
179