xref: /netbsd-src/sys/modules/examples/fopsmapper/fopsmapper.c (revision 212c9b3b52d0f45cb4a5c673ffdad2160584d688)
1 /*	$NetBSD: fopsmapper.c,v 1.3 2024/04/17 18:10:27 riastradh Exp $	*/
2 
3 /*-
4  * Copyright (c) 2020 The NetBSD Foundation, Inc.
5  * All rights reserved.
6  *
7  * Redistribution and use in source and binary forms, with or without
8  * modification, are permitted provided that the following conditions
9  * are met:
10  * 1. Redistributions of source code must retain the above copyright
11  *    notice, this list of conditions and the following disclaimer.
12  * 2. Redistributions in binary form must reproduce the above copyright
13  *    notice, this list of conditions and the following disclaimer in the
14  *    documentation and/or other materials provided with the distribution.
15  *
16  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
17  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
18  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
19  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
20  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
21  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
22  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
23  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
24  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
25  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
26  * POSSIBILITY OF SUCH DAMAGE.
27  */
28 
29 #include <sys/cdefs.h>
30 __KERNEL_RCSID(0, "$NetBSD: fopsmapper.c,v 1.3 2024/04/17 18:10:27 riastradh Exp $");
31 
32 #include <sys/types.h>
33 
34 #include <sys/conf.h>
35 #include <sys/file.h>
36 #include <sys/filedesc.h>
37 #include <sys/kernel.h>
38 #include <sys/kmem.h>
39 #include <sys/mman.h>
40 #include <sys/module.h>
41 #include <sys/mutex.h>
42 #include <sys/param.h>
43 #include <sys/systm.h>
44 
45 #include <uvm/uvm_extern.h>
46 
47 /*
48  * To use this module you need to:
49  *
50  * mknod /dev/fopsmapper c 351 0
51  */
52 
53 dev_open_t fopsmapper_open;
54 
55 const struct cdevsw fopsmapper_cdevsw = {
56 	.d_open = fopsmapper_open,
57 	.d_close = noclose,
58 	.d_read = noread,
59 	.d_write = nowrite,
60 	.d_ioctl = noioctl,
61 	.d_stop = nostop,
62 	.d_tty = notty,
63 	.d_poll = nopoll,
64 	.d_mmap = nommap,
65 	.d_kqfilter = nokqfilter,
66 	.d_discard = nodiscard,
67 	.d_flag = D_OTHER
68 };
69 
70 static int fopsmapper_mmap(struct file *, off_t *, size_t, int, int *, int *,
71     struct uvm_object **, int *);
72 static int fopsmapper_close(struct file *);
73 
74 const struct fileops mapper_fileops = {
75 	.fo_read = fbadop_read,
76 	.fo_write = fbadop_write,
77 	.fo_ioctl = fbadop_ioctl,
78 	.fo_fcntl = fnullop_fcntl,
79 	.fo_poll = fnullop_poll,
80 	.fo_stat = fbadop_stat,
81 	.fo_close = fopsmapper_close,
82 	.fo_kqfilter = fnullop_kqfilter,
83 	.fo_restart = fnullop_restart,
84 	.fo_mmap = fopsmapper_mmap,
85 };
86 
87 struct fopsmapper_softc {
88 	char *buf;
89 	struct uvm_object *uobj;
90 	size_t bufsize;
91 };
92 
93 int
fopsmapper_open(dev_t dev,int flag,int mode,struct lwp * l)94 fopsmapper_open(dev_t dev, int flag, int mode, struct lwp *l)
95 {
96 	struct fopsmapper_softc *fo;
97 	struct file *fp;
98 	int fd, error;
99 
100 	if ((error = fd_allocfile(&fp, &fd)) != 0)
101 		return error;
102 
103 	fo = kmem_zalloc(sizeof(*fo), KM_SLEEP);
104 
105 	return fd_clone(fp, fd, flag, &mapper_fileops, fo);
106 }
107 
108 int
fopsmapper_mmap(struct file * fp,off_t * offp,size_t size,int prot,int * flagsp,int * advicep,struct uvm_object ** uobjp,int * maxprotp)109 fopsmapper_mmap(struct file *fp, off_t *offp, size_t size, int prot,
110     int *flagsp, int *advicep, struct uvm_object **uobjp, int *maxprotp)
111 {
112 	struct fopsmapper_softc *fo;
113 	vaddr_t va;
114 	int error;
115 
116 	if (prot & PROT_EXEC)
117 		return EACCES;
118 
119 	if (size != (size_t)PAGE_SIZE)
120 		return EINVAL;
121 
122 	if ((fo = fp->f_data) == NULL)
123 		return ENXIO;
124 
125 	fo->bufsize = size;
126 	fo->uobj = uao_create(size, 0);
127 
128 	fo->buf = NULL;
129 
130 	/*
131 	 * Map the uvm object into kernel.  Consumes our reference to
132 	 * uobj on success.
133 	 */
134 	error =	uvm_map(kernel_map, &va, fo->bufsize, fo->uobj, 0, 0,
135 	    UVM_MAPFLAG(UVM_PROT_RW, UVM_PROT_RW,
136 		UVM_INH_SHARE, UVM_ADV_RANDOM, 0));
137 	if (error) {
138 		uao_detach(fo->uobj);
139 		goto out;
140 	}
141 	fo->buf = (char *)va;
142 	snprintf(fo->buf, 13, "Hey There!");
143 
144 	/* Get the reference of uobj */
145 	uao_reference(fo->uobj);
146 	*uobjp = fo->uobj;
147 	*maxprotp = prot;
148 	*advicep = UVM_ADV_RANDOM;
149 	error = 0;
150 
151 out:	return error;
152 }
153 
154 int
fopsmapper_close(struct file * fp)155 fopsmapper_close(struct file *fp)
156 {
157 	struct fopsmapper_softc *fo;
158 
159 	fo = fp->f_data;
160 	KASSERT(fo != NULL);
161 
162 	if (fo->buf != NULL)
163 		uvm_deallocate(kernel_map, (vaddr_t)fo->buf, fo->bufsize);
164 
165 	kmem_free(fo, sizeof(*fo));
166 
167 	return 0;
168 }
169 
170 MODULE(MODULE_CLASS_MISC, fopsmapper, NULL);
171 
172 static int
fopsmapper_modcmd(modcmd_t cmd,void * arg __unused)173 fopsmapper_modcmd(modcmd_t cmd, void *arg __unused)
174 {
175 	int cmajor = 351, bmajor = -1;
176 
177 	switch (cmd) {
178 	case MODULE_CMD_INIT:
179 		if (devsw_attach("fopsmapper", NULL, &bmajor,
180 			&fopsmapper_cdevsw, &cmajor))
181 			return ENXIO;
182 		return 0;
183 	case MODULE_CMD_FINI:
184 		return EBUSY;
185 	default:
186 		return ENOTTY;
187 	}
188 }
189