1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause
3 *
4 * Copyright (c) 2022, Jake Freeland <jfree@freebsd.org>
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
16 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
25 * SUCH DAMAGE.
26 */
27
28 #include <sys/types.h>
29 #include <linux/fs.h>
30
31 MALLOC_DEFINE(M_LSATTR, "simple_attr", "Linux Simple Attribute File");
32
33 struct simple_attr {
34 int (*get)(void *, uint64_t *);
35 int (*set)(void *, uint64_t);
36 void *data;
37 const char *fmt;
38 struct mutex mutex;
39 };
40
41 /*
42 * simple_attr_open: open and populate simple attribute data
43 *
44 * @inode: file inode
45 * @filp: file pointer
46 * @get: ->get() for reading file data
47 * @set: ->set() for writing file data
48 * @fmt: format specifier for data returned by @get
49 *
50 * Memory allocate a simple_attr and appropriately initialize its members.
51 * The simple_attr must be stored in filp->private_data.
52 * Simple attr files do not support seeking. Open the file as nonseekable.
53 *
54 * Return value: simple attribute file descriptor
55 */
56 int
simple_attr_open(struct inode * inode,struct file * filp,int (* get)(void *,uint64_t *),int (* set)(void *,uint64_t),const char * fmt)57 simple_attr_open(struct inode *inode, struct file *filp,
58 int (*get)(void *, uint64_t *), int (*set)(void *, uint64_t),
59 const char *fmt)
60 {
61 struct simple_attr *sattr;
62 sattr = malloc(sizeof(*sattr), M_LSATTR, M_ZERO | M_NOWAIT);
63 if (sattr == NULL)
64 return (-ENOMEM);
65
66 sattr->get = get;
67 sattr->set = set;
68 sattr->data = inode->i_private;
69 sattr->fmt = fmt;
70 mutex_init(&sattr->mutex);
71
72 filp->private_data = (void *) sattr;
73
74 return (nonseekable_open(inode, filp));
75 }
76
77 int
simple_attr_release(struct inode * inode,struct file * filp)78 simple_attr_release(struct inode *inode, struct file *filp)
79 {
80 free(filp->private_data, M_LSATTR);
81 return (0);
82 }
83
84 /*
85 * simple_attr_read: read simple attr data and transfer into buffer
86 *
87 * @filp: file pointer
88 * @buf: kernel space buffer
89 * @read_size: number of bytes to be transferred
90 * @ppos: starting pointer position for transfer
91 *
92 * The simple_attr structure is stored in filp->private_data.
93 * ->get() retrieves raw file data.
94 * The ->fmt specifier can format this data to be human readable.
95 * This output is then transferred into the @buf buffer.
96 *
97 * Return value:
98 * On success, number of bytes transferred
99 * On failure, negative signed ERRNO
100 */
101 ssize_t
simple_attr_read(struct file * filp,char __user * buf,size_t read_size,loff_t * ppos)102 simple_attr_read(struct file *filp, char __user *buf, size_t read_size,
103 loff_t *ppos)
104 {
105 struct simple_attr *sattr;
106 uint64_t data;
107 ssize_t ret;
108 char prebuf[24];
109
110 sattr = filp->private_data;
111
112 if (sattr->get == NULL)
113 return (-EFAULT);
114
115 mutex_lock(&sattr->mutex);
116
117 ret = sattr->get(sattr->data, &data);
118 if (ret)
119 goto unlock;
120
121 scnprintf(prebuf, sizeof(prebuf), sattr->fmt, data);
122
123 /* add 1 for null terminator */
124 ret = simple_read_from_buffer(buf, read_size, ppos, prebuf,
125 strlen(prebuf) + 1);
126
127 unlock:
128 mutex_unlock(&sattr->mutex);
129 return (ret);
130 }
131
132 /*
133 * simple_attr_write_common: write contents of buffer into simple attribute file
134 *
135 * @filp: file pointer
136 * @buf: kernel space buffer
137 * @write_size: number bytes to be transferred
138 * @ppos: starting pointer position for transfer
139 * @is_signed: signedness of data in @buf
140 *
141 * The simple_attr structure is stored in filp->private_data.
142 * Convert the @buf string to unsigned long long.
143 * ->set() writes unsigned long long data into the simple attr file.
144 *
145 * Return value:
146 * On success, number of bytes written to simple attr
147 * On failure, negative signed ERRNO
148 */
149 static ssize_t
simple_attr_write_common(struct file * filp,const char __user * ubuf,size_t write_size,loff_t * ppos,bool is_signed)150 simple_attr_write_common(struct file *filp, const char __user *ubuf,
151 size_t write_size, loff_t *ppos, bool is_signed)
152 {
153 struct simple_attr *sattr;
154 unsigned long long data;
155 char *buf;
156 ssize_t ret;
157
158 sattr = filp->private_data;
159
160 if (sattr->set == NULL)
161 return (-EFAULT);
162
163 if (*ppos != 0 || write_size < 1)
164 return (-EINVAL);
165
166 buf = malloc(write_size, M_LSATTR, M_WAITOK);
167 if (copy_from_user(buf, ubuf, write_size) != 0) {
168 free(buf, M_LSATTR);
169 return (-EFAULT);
170 }
171 if (strnlen(buf, write_size) == write_size) {
172 free(buf, M_LSATTR);
173 return (-EINVAL);
174 }
175
176 mutex_lock(&sattr->mutex);
177
178 if (is_signed)
179 ret = kstrtoll(buf, 0, &data);
180 else
181 ret = kstrtoull(buf, 0, &data);
182 if (ret)
183 goto unlock;
184
185 ret = sattr->set(sattr->data, data);
186 if (ret)
187 goto unlock;
188
189 ret = write_size;
190
191 unlock:
192 mutex_unlock(&sattr->mutex);
193 free(buf, M_LSATTR);
194 return (ret);
195 }
196
197 ssize_t
simple_attr_write(struct file * filp,const char __user * buf,size_t write_size,loff_t * ppos)198 simple_attr_write(struct file *filp, const char __user *buf, size_t write_size,
199 loff_t *ppos)
200 {
201 return (simple_attr_write_common(filp, buf, write_size, ppos, false));
202 }
203
204 ssize_t
simple_attr_write_signed(struct file * filp,const char __user * buf,size_t write_size,loff_t * ppos)205 simple_attr_write_signed(struct file *filp, const char __user *buf,
206 size_t write_size, loff_t *ppos)
207 {
208 return (simple_attr_write_common(filp, buf, write_size, ppos, true));
209 }
210