1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD 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/cdefs.h> 29 __FBSDID("$FreeBSD$"); 30 31 #include <sys/types.h> 32 #include <linux/fs.h> 33 34 MALLOC_DEFINE(M_LSATTR, "simple_attr", "Linux Simple Attribute File"); 35 36 struct simple_attr { 37 int (*get)(void *, uint64_t *); 38 int (*set)(void *, uint64_t); 39 void *data; 40 const char *fmt; 41 struct mutex mutex; 42 }; 43 44 /* 45 * simple_attr_open: open and populate simple attribute data 46 * 47 * @inode: file inode 48 * @filp: file pointer 49 * @get: ->get() for reading file data 50 * @set: ->set() for writing file data 51 * @fmt: format specifier for data returned by @get 52 * 53 * Memory allocate a simple_attr and appropriately initialize its members. 54 * The simple_attr must be stored in filp->private_data. 55 * Simple attr files do not support seeking. Open the file as nonseekable. 56 * 57 * Return value: simple attribute file descriptor 58 */ 59 int 60 simple_attr_open(struct inode *inode, struct file *filp, 61 int (*get)(void *, uint64_t *), int (*set)(void *, uint64_t), 62 const char *fmt) 63 { 64 struct simple_attr *sattr; 65 sattr = malloc(sizeof(*sattr), M_LSATTR, M_ZERO | M_NOWAIT); 66 if (sattr == NULL) 67 return (-ENOMEM); 68 69 sattr->get = get; 70 sattr->set = set; 71 sattr->data = inode->i_private; 72 sattr->fmt = fmt; 73 mutex_init(&sattr->mutex); 74 75 filp->private_data = (void *) sattr; 76 77 return (nonseekable_open(inode, filp)); 78 } 79 80 int 81 simple_attr_release(struct inode *inode, struct file *filp) 82 { 83 free(filp->private_data, M_LSATTR); 84 return (0); 85 } 86 87 /* 88 * simple_attr_read: read simple attr data and transfer into buffer 89 * 90 * @filp: file pointer 91 * @buf: kernel space buffer 92 * @read_size: number of bytes to be transferred 93 * @ppos: starting pointer position for transfer 94 * 95 * The simple_attr structure is stored in filp->private_data. 96 * ->get() retrieves raw file data. 97 * The ->fmt specifier can format this data to be human readable. 98 * This output is then transferred into the @buf buffer. 99 * 100 * Return value: 101 * On success, number of bytes transferred 102 * On failure, negative signed ERRNO 103 */ 104 ssize_t 105 simple_attr_read(struct file *filp, char *buf, size_t read_size, loff_t *ppos) 106 { 107 struct simple_attr *sattr; 108 uint64_t data; 109 ssize_t ret; 110 char prebuf[24]; 111 112 sattr = filp->private_data; 113 114 if (sattr->get == NULL) 115 return (-EFAULT); 116 117 mutex_lock(&sattr->mutex); 118 119 ret = sattr->get(sattr->data, &data); 120 if (ret) 121 goto unlock; 122 123 scnprintf(prebuf, sizeof(prebuf), sattr->fmt, data); 124 125 ret = strlen(prebuf) + 1; 126 if (*ppos >= ret || read_size < 1) { 127 ret = -EINVAL; 128 goto unlock; 129 } 130 131 read_size = min(ret - *ppos, read_size); 132 ret = strscpy(buf, prebuf + *ppos, read_size); 133 134 /* add 1 for null terminator */ 135 if (ret > 0) 136 ret += 1; 137 138 unlock: 139 mutex_unlock(&sattr->mutex); 140 return (ret); 141 } 142 143 /* 144 * simple_attr_write: write contents of buffer into simple attribute file 145 * 146 * @filp: file pointer 147 * @buf: kernel space buffer 148 * @write_size: number bytes to be transferred 149 * @ppos: starting pointer position for transfer 150 * 151 * The simple_attr structure is stored in filp->private_data. 152 * Convert the @buf string to unsigned long long. 153 * ->set() writes unsigned long long data into the simple attr file. 154 * 155 * Return value: 156 * On success, number of bytes written to simple attr 157 * On failure, negative signed ERRNO 158 */ 159 ssize_t 160 simple_attr_write(struct file *filp, const char *buf, size_t write_size, loff_t *ppos) 161 { 162 struct simple_attr *sattr; 163 unsigned long long data; 164 size_t bufsize; 165 ssize_t ret; 166 167 sattr = filp->private_data; 168 bufsize = strlen(buf) + 1; 169 170 if (sattr->set == NULL) 171 return (-EFAULT); 172 173 if (*ppos >= bufsize || write_size < 1) 174 return (-EINVAL); 175 176 mutex_lock(&sattr->mutex); 177 178 ret = kstrtoull(buf + *ppos, 0, &data); 179 if (ret) 180 goto unlock; 181 182 ret = sattr->set(sattr->data, data); 183 if (ret) 184 goto unlock; 185 186 ret = bufsize - *ppos; 187 188 unlock: 189 mutex_unlock(&sattr->mutex); 190 return (ret); 191 } 192