1 /* $NetBSD: vfs_hooks.c,v 1.9 2024/12/07 02:27:38 riastradh Exp $ */
2
3 /*-
4 * Copyright (c) 2005 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Julio M. Merino Vidal.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29 * POSSIBILITY OF SUCH DAMAGE.
30 */
31
32 /*
33 * VFS hooks.
34 */
35
36 #include <sys/cdefs.h>
37 __KERNEL_RCSID(0, "$NetBSD: vfs_hooks.c,v 1.9 2024/12/07 02:27:38 riastradh Exp $");
38
39 #include <sys/param.h>
40
41 #include <sys/errno.h>
42 #include <sys/mount.h>
43 #include <sys/mutex.h>
44 #include <sys/queue.h>
45 #include <sys/sdt.h>
46
47 LIST_HEAD(vfs_hooks_head, vfs_hooks) vfs_hooks_head =
48 LIST_HEAD_INITIALIZER(vfs_hooks_head);
49
50 kmutex_t vfs_hooks_lock;
51
52 void
vfs_hooks_init(void)53 vfs_hooks_init(void)
54 {
55
56 mutex_init(&vfs_hooks_lock, MUTEX_DEFAULT, IPL_NONE);
57 }
58
59 int
vfs_hooks_attach(struct vfs_hooks * vfs_hooks)60 vfs_hooks_attach(struct vfs_hooks *vfs_hooks)
61 {
62
63 mutex_enter(&vfs_hooks_lock);
64 LIST_INSERT_HEAD(&vfs_hooks_head, vfs_hooks, vfs_hooks_list);
65 mutex_exit(&vfs_hooks_lock);
66
67 return 0;
68 }
69
70 int
vfs_hooks_detach(struct vfs_hooks * vfs_hooks)71 vfs_hooks_detach(struct vfs_hooks *vfs_hooks)
72 {
73 struct vfs_hooks *hp;
74 int ret = 0;
75
76 mutex_enter(&vfs_hooks_lock);
77 LIST_FOREACH(hp, &vfs_hooks_head, vfs_hooks_list) {
78 if (hp == vfs_hooks) {
79 LIST_REMOVE(hp, vfs_hooks_list);
80 break;
81 }
82 }
83 if (hp == NULL)
84 ret = SET_ERROR(ESRCH);
85 mutex_exit(&vfs_hooks_lock);
86
87 return ret;
88 }
89
90 /*
91 * Macro to be used in one of the vfs_hooks_* function for hooks that
92 * return an error code. Calls will stop as soon as one of the hooks
93 * fails.
94 */
95 #define VFS_HOOKS_W_ERROR(func, fargs, hook, hargs) \
96 int \
97 func fargs \
98 { \
99 int error; \
100 struct vfs_hooks *hp; \
101 \
102 error = EJUSTRETURN; \
103 \
104 mutex_enter(&vfs_hooks_lock); \
105 LIST_FOREACH(hp, &vfs_hooks_head, vfs_hooks_list) { \
106 if (hp-> hook != NULL) { \
107 error = hp-> hook hargs; \
108 if (error != 0) \
109 break; \
110 } \
111 } \
112 mutex_exit(&vfs_hooks_lock); \
113 \
114 return error; \
115 }
116
117 /*
118 * Macro to be used in one of the vfs_hooks_* function for hooks that
119 * do not return any error code. All hooks will be executed
120 * unconditionally.
121 */
122 #define VFS_HOOKS_WO_ERROR(func, fargs, hook, hargs) \
123 void \
124 func fargs \
125 { \
126 struct vfs_hooks *hp; \
127 \
128 mutex_enter(&vfs_hooks_lock); \
129 LIST_FOREACH(hp, &vfs_hooks_head, vfs_hooks_list) { \
130 if (hp-> hook != NULL) \
131 hp-> hook hargs; \
132 } \
133 mutex_exit(&vfs_hooks_lock); \
134 }
135
136 /*
137 * Routines to iterate over VFS hooks lists and execute them.
138 */
139
140 VFS_HOOKS_WO_ERROR(vfs_hooks_unmount, (struct mount *mp), vh_unmount, (mp));
141 VFS_HOOKS_W_ERROR(vfs_hooks_reexport, (struct mount *mp, const char *path, void *data), vh_reexport, (mp, path, data));
142