kernel/time/posix-clock.c

   1 /*
   2  * posix-clock.c - support for dynamic clock devices
   3  *
   4  * Copyright (C) 2010 OMICRON electronics GmbH
   5  *
   6  *  This program is free software; you can redistribute it and/or modify
   7  *  it under the terms of the GNU General Public License as published by
   8  *  the Free Software Foundation; either version 2 of the License, or
   9  *  (at your option) any later version.
  10  *
  11  *  This program is distributed in the hope that it will be useful,
  12  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  *  GNU General Public License for more details.
  15  *
  16  *  You should have received a copy of the GNU General Public License
  17  *  along with this program; if not, write to the Free Software
  18  *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  19  */
  20 #include <linux/device.h>
  21 #include <linux/export.h>
  22 #include <linux/file.h>
  23 #include <linux/posix-clock.h>
  24 #include <linux/slab.h>
  25 #include <linux/syscalls.h>
  26 #include <linux/uaccess.h>
  27
  28 #include "posix-timers.h"
  29
  30 static void delete_clock(struct kref *kref);
  31
  32 /*
  33  * Returns NULL if the posix_clock instance attached to 'fp' is old and stale.
  34  */
  35 static struct posix_clock *get_posix_clock(struct file *fp)
  36 {
  37         struct posix_clock *clk = fp->private_data;
  38
  39         down_read(&clk->rwsem);
  40
  41         if (!clk->zombie)
  42                 return clk;
  43
  44         up_read(&clk->rwsem);
  45
  46         return NULL;
  47 }
  48
  49 static void put_posix_clock(struct posix_clock *clk)
  50 {
  51         up_read(&clk->rwsem);
  52 }
  53
  54 static ssize_t posix_clock_read(struct file *fp, char __user *buf,
  55                                 size_t count, loff_t *ppos)
  56 {
  57         struct posix_clock *clk = get_posix_clock(fp);
  58         int err = -EINVAL;
  59
  60         if (!clk)
  61                 return -ENODEV;
  62
  63         if (clk->ops.read)
  64                 err = clk->ops.read(clk, fp->f_flags, buf, count);
  65
  66         put_posix_clock(clk);
  67
  68         return err;
  69 }
  70
  71 static unsigned int posix_clock_poll(struct file *fp, poll_table *wait)
  72 {
  73         struct posix_clock *clk = get_posix_clock(fp);
  74         unsigned int result = 0;
  75
  76         if (!clk)
  77                 return POLLERR;
  78
  79         if (clk->ops.poll)
  80                 result = clk->ops.poll(clk, fp, wait);
  81
  82         put_posix_clock(clk);
  83
  84         return result;
  85 }
  86
  87 static long posix_clock_ioctl(struct file *fp,
  88                               unsigned int cmd, unsigned long arg)
  89 {
  90         struct posix_clock *clk = get_posix_clock(fp);
  91         int err = -ENOTTY;
  92
  93         if (!clk)
  94                 return -ENODEV;
  95
  96         if (clk->ops.ioctl)
  97                 err = clk->ops.ioctl(clk, cmd, arg);
  98
  99         put_posix_clock(clk);
 100
 101         return err;
 102 }
 103
 104 #ifdef CONFIG_COMPAT
 105 static long posix_clock_compat_ioctl(struct file *fp,
 106                                      unsigned int cmd, unsigned long arg)
 107 {
 108         struct posix_clock *clk = get_posix_clock(fp);
 109         int err = -ENOTTY;
 110
 111         if (!clk)
 112                 return -ENODEV;
 113
 114         if (clk->ops.ioctl)
 115                 err = clk->ops.ioctl(clk, cmd, arg);
 116
 117         put_posix_clock(clk);
 118
 119         return err;
 120 }
 121 #endif
 122
 123 static int posix_clock_open(struct inode *inode, struct file *fp)
 124 {
 125         int err;
 126         struct posix_clock *clk =
 127                 container_of(inode->i_cdev, struct posix_clock, cdev);
 128
 129         down_read(&clk->rwsem);
 130
 131         if (clk->zombie) {
 132                 err = -ENODEV;
 133                 goto out;
 134         }
 135         if (clk->ops.open)
 136                 err = clk->ops.open(clk, fp->f_mode);
 137         else
 138                 err = 0;
 139
 140         if (!err) {
 141                 kref_get(&clk->kref);
 142                 fp->private_data = clk;
 143         }
 144 out:
 145         up_read(&clk->rwsem);
 146         return err;
 147 }
 148
 149 static int posix_clock_release(struct inode *inode, struct file *fp)
 150 {
 151         struct posix_clock *clk = fp->private_data;
 152         int err = 0;
 153
 154         if (clk->ops.release)
 155                 err = clk->ops.release(clk);
 156
 157         kref_put(&clk->kref, delete_clock);
 158
 159         fp->private_data = NULL;
 160
 161         return err;
 162 }
 163
 164 static const struct file_operations posix_clock_file_operations = {
 165         .owner          = THIS_MODULE,
 166         .llseek         = no_llseek,
 167         .read           = posix_clock_read,
 168         .poll           = posix_clock_poll,
 169         .unlocked_ioctl = posix_clock_ioctl,
 170         .open           = posix_clock_open,
 171         .release        = posix_clock_release,
 172 #ifdef CONFIG_COMPAT
 173         .compat_ioctl   = posix_clock_compat_ioctl,
 174 #endif
 175 };
 176
 177 int posix_clock_register(struct posix_clock *clk, dev_t devid)
 178 {
 179         int err;
 180
 181         kref_init(&clk->kref);
 182         init_rwsem(&clk->rwsem);
 183
 184         cdev_init(&clk->cdev, &posix_clock_file_operations);
 185         clk->cdev.owner = clk->ops.owner;
 186         err = cdev_add(&clk->cdev, devid, 1);
 187
 188         return err;
 189 }
 190 EXPORT_SYMBOL_GPL(posix_clock_register);
 191
 192 static void delete_clock(struct kref *kref)
 193 {
 194         struct posix_clock *clk = container_of(kref, struct posix_clock, kref);
 195
 196         if (clk->release)
 197                 clk->release(clk);
 198 }
 199
 200 void posix_clock_unregister(struct posix_clock *clk)
 201 {
 202         cdev_del(&clk->cdev);
 203
 204         down_write(&clk->rwsem);
 205         clk->zombie = true;
 206         up_write(&clk->rwsem);
 207
 208         kref_put(&clk->kref, delete_clock);
 209 }
 210 EXPORT_SYMBOL_GPL(posix_clock_unregister);
 211
 212 struct posix_clock_desc {
 213         struct file *fp;
 214         struct posix_clock *clk;
 215 };
 216
 217 static int get_clock_desc(const clockid_t id, struct posix_clock_desc *cd)
 218 {
 219         struct file *fp = fget(CLOCKID_TO_FD(id));
 220         int err = -EINVAL;
 221
 222         if (!fp)
 223                 return err;
 224
 225         if (fp->f_op->open != posix_clock_open || !fp->private_data)
 226                 goto out;
 227
 228         cd->fp = fp;
 229         cd->clk = get_posix_clock(fp);
 230
 231         err = cd->clk ? 0 : -ENODEV;
 232 out:
 233         if (err)
 234                 fput(fp);
 235         return err;
 236 }
 237
 238 static void put_clock_desc(struct posix_clock_desc *cd)
 239 {
 240         put_posix_clock(cd->clk);
 241         fput(cd->fp);
 242 }
 243
 244 static int pc_clock_adjtime(clockid_t id, struct timex *tx)
 245 {
 246         struct posix_clock_desc cd;
 247         int err;
 248
 249         err = get_clock_desc(id, &cd);
 250         if (err)
 251                 return err;
 252
 253         if ((cd.fp->f_mode & FMODE_WRITE) == 0) {
 254                 err = -EACCES;
 255                 goto out;
 256         }
 257
 258         if (cd.clk->ops.clock_adjtime)
 259                 err = cd.clk->ops.clock_adjtime(cd.clk, tx);
 260         else
 261                 err = -EOPNOTSUPP;
 262 out:
 263         put_clock_desc(&cd);
 264
 265         return err;
 266 }
 267
 268 static int pc_clock_gettime(clockid_t id, struct timespec64 *ts)
 269 {
 270         struct posix_clock_desc cd;
 271         int err;
 272
 273         err = get_clock_desc(id, &cd);
 274         if (err)
 275                 return err;
 276
 277         if (cd.clk->ops.clock_gettime)
 278                 err = cd.clk->ops.clock_gettime(cd.clk, ts);
 279         else
 280                 err = -EOPNOTSUPP;
 281
 282         put_clock_desc(&cd);
 283
 284         return err;
 285 }
 286
 287 static int pc_clock_getres(clockid_t id, struct timespec64 *ts)
 288 {
 289         struct posix_clock_desc cd;
 290         int err;
 291
 292         err = get_clock_desc(id, &cd);
 293         if (err)
 294                 return err;
 295
 296         if (cd.clk->ops.clock_getres)
 297                 err = cd.clk->ops.clock_getres(cd.clk, ts);
 298         else
 299                 err = -EOPNOTSUPP;
 300
 301         put_clock_desc(&cd);
 302
 303         return err;
 304 }
 305
 306 static int pc_clock_settime(clockid_t id, const struct timespec64 *ts)
 307 {
 308         struct posix_clock_desc cd;
 309         int err;
 310
 311         err = get_clock_desc(id, &cd);
 312         if (err)
 313                 return err;
 314
 315         if ((cd.fp->f_mode & FMODE_WRITE) == 0) {
 316                 err = -EACCES;
 317                 goto out;
 318         }
 319
 320         if (cd.clk->ops.clock_settime)
 321                 err = cd.clk->ops.clock_settime(cd.clk, ts);
 322         else
 323                 err = -EOPNOTSUPP;
 324 out:
 325         put_clock_desc(&cd);
 326
 327         return err;
 328 }
 329
 330 const struct k_clock clock_posix_dynamic = {
 331         .clock_getres   = pc_clock_getres,
 332         .clock_set      = pc_clock_settime,
 333         .clock_get      = pc_clock_gettime,
 334         .clock_adj      = pc_clock_adjtime,
 335 };