1*4882a593Smuzhiyun // SPDX-License-Identifier: GPL-2.0
2*4882a593Smuzhiyun /*
3*4882a593Smuzhiyun * memfd test file-system
4*4882a593Smuzhiyun * This file uses FUSE to create a dummy file-system with only one file /memfd.
5*4882a593Smuzhiyun * This file is read-only and takes 1s per read.
6*4882a593Smuzhiyun *
7*4882a593Smuzhiyun * This file-system is used by the memfd test-cases to force the kernel to pin
8*4882a593Smuzhiyun * pages during reads(). Due to the 1s delay of this file-system, this is a
9*4882a593Smuzhiyun * nice way to test race-conditions against get_user_pages() in the kernel.
10*4882a593Smuzhiyun *
11*4882a593Smuzhiyun * We use direct_io==1 to force the kernel to use direct-IO for this
12*4882a593Smuzhiyun * file-system.
13*4882a593Smuzhiyun */
14*4882a593Smuzhiyun
15*4882a593Smuzhiyun #define FUSE_USE_VERSION 26
16*4882a593Smuzhiyun
17*4882a593Smuzhiyun #include <fuse.h>
18*4882a593Smuzhiyun #include <stdio.h>
19*4882a593Smuzhiyun #include <string.h>
20*4882a593Smuzhiyun #include <errno.h>
21*4882a593Smuzhiyun #include <fcntl.h>
22*4882a593Smuzhiyun #include <unistd.h>
23*4882a593Smuzhiyun
24*4882a593Smuzhiyun static const char memfd_content[] = "memfd-example-content";
25*4882a593Smuzhiyun static const char memfd_path[] = "/memfd";
26*4882a593Smuzhiyun
memfd_getattr(const char * path,struct stat * st)27*4882a593Smuzhiyun static int memfd_getattr(const char *path, struct stat *st)
28*4882a593Smuzhiyun {
29*4882a593Smuzhiyun memset(st, 0, sizeof(*st));
30*4882a593Smuzhiyun
31*4882a593Smuzhiyun if (!strcmp(path, "/")) {
32*4882a593Smuzhiyun st->st_mode = S_IFDIR | 0755;
33*4882a593Smuzhiyun st->st_nlink = 2;
34*4882a593Smuzhiyun } else if (!strcmp(path, memfd_path)) {
35*4882a593Smuzhiyun st->st_mode = S_IFREG | 0444;
36*4882a593Smuzhiyun st->st_nlink = 1;
37*4882a593Smuzhiyun st->st_size = strlen(memfd_content);
38*4882a593Smuzhiyun } else {
39*4882a593Smuzhiyun return -ENOENT;
40*4882a593Smuzhiyun }
41*4882a593Smuzhiyun
42*4882a593Smuzhiyun return 0;
43*4882a593Smuzhiyun }
44*4882a593Smuzhiyun
memfd_readdir(const char * path,void * buf,fuse_fill_dir_t filler,off_t offset,struct fuse_file_info * fi)45*4882a593Smuzhiyun static int memfd_readdir(const char *path,
46*4882a593Smuzhiyun void *buf,
47*4882a593Smuzhiyun fuse_fill_dir_t filler,
48*4882a593Smuzhiyun off_t offset,
49*4882a593Smuzhiyun struct fuse_file_info *fi)
50*4882a593Smuzhiyun {
51*4882a593Smuzhiyun if (strcmp(path, "/"))
52*4882a593Smuzhiyun return -ENOENT;
53*4882a593Smuzhiyun
54*4882a593Smuzhiyun filler(buf, ".", NULL, 0);
55*4882a593Smuzhiyun filler(buf, "..", NULL, 0);
56*4882a593Smuzhiyun filler(buf, memfd_path + 1, NULL, 0);
57*4882a593Smuzhiyun
58*4882a593Smuzhiyun return 0;
59*4882a593Smuzhiyun }
60*4882a593Smuzhiyun
memfd_open(const char * path,struct fuse_file_info * fi)61*4882a593Smuzhiyun static int memfd_open(const char *path, struct fuse_file_info *fi)
62*4882a593Smuzhiyun {
63*4882a593Smuzhiyun if (strcmp(path, memfd_path))
64*4882a593Smuzhiyun return -ENOENT;
65*4882a593Smuzhiyun
66*4882a593Smuzhiyun if ((fi->flags & 3) != O_RDONLY)
67*4882a593Smuzhiyun return -EACCES;
68*4882a593Smuzhiyun
69*4882a593Smuzhiyun /* force direct-IO */
70*4882a593Smuzhiyun fi->direct_io = 1;
71*4882a593Smuzhiyun
72*4882a593Smuzhiyun return 0;
73*4882a593Smuzhiyun }
74*4882a593Smuzhiyun
memfd_read(const char * path,char * buf,size_t size,off_t offset,struct fuse_file_info * fi)75*4882a593Smuzhiyun static int memfd_read(const char *path,
76*4882a593Smuzhiyun char *buf,
77*4882a593Smuzhiyun size_t size,
78*4882a593Smuzhiyun off_t offset,
79*4882a593Smuzhiyun struct fuse_file_info *fi)
80*4882a593Smuzhiyun {
81*4882a593Smuzhiyun size_t len;
82*4882a593Smuzhiyun
83*4882a593Smuzhiyun if (strcmp(path, memfd_path) != 0)
84*4882a593Smuzhiyun return -ENOENT;
85*4882a593Smuzhiyun
86*4882a593Smuzhiyun sleep(1);
87*4882a593Smuzhiyun
88*4882a593Smuzhiyun len = strlen(memfd_content);
89*4882a593Smuzhiyun if (offset < len) {
90*4882a593Smuzhiyun if (offset + size > len)
91*4882a593Smuzhiyun size = len - offset;
92*4882a593Smuzhiyun
93*4882a593Smuzhiyun memcpy(buf, memfd_content + offset, size);
94*4882a593Smuzhiyun } else {
95*4882a593Smuzhiyun size = 0;
96*4882a593Smuzhiyun }
97*4882a593Smuzhiyun
98*4882a593Smuzhiyun return size;
99*4882a593Smuzhiyun }
100*4882a593Smuzhiyun
101*4882a593Smuzhiyun static struct fuse_operations memfd_ops = {
102*4882a593Smuzhiyun .getattr = memfd_getattr,
103*4882a593Smuzhiyun .readdir = memfd_readdir,
104*4882a593Smuzhiyun .open = memfd_open,
105*4882a593Smuzhiyun .read = memfd_read,
106*4882a593Smuzhiyun };
107*4882a593Smuzhiyun
main(int argc,char * argv[])108*4882a593Smuzhiyun int main(int argc, char *argv[])
109*4882a593Smuzhiyun {
110*4882a593Smuzhiyun return fuse_main(argc, argv, &memfd_ops, NULL);
111*4882a593Smuzhiyun }
112