sys/kern/kern_conf.c

   1 /*-
   2  * Parts Copyright (c) 1995 Terrence R. Lambert
   3  * Copyright (c) 1995 Julian R. Elischer
   4  * All rights reserved.
   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  * 3. All advertising materials mentioning features or use of this software
  15  *    must display the following acknowledgement:
  16  *      This product includes software developed by Terrence R. Lambert.
  17  * 4. The name Terrence R. Lambert may not be used to endorse or promote
  18  *    products derived from this software without specific prior written
  19  *    permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY Julian R. Elischer ``AS IS'' AND ANY
  22  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE TERRENCE R. LAMBERT BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  *
  33  * $FreeBSD: src/sys/kern/kern_conf.c,v 1.73.2.3 2003/03/10 02:18:25 imp Exp $
  34  * $DragonFly: src/sys/kern/kern_conf.c,v 1.11 2005/03/23 02:50:53 dillon Exp $
  35  */
  36
  37 #include <sys/param.h>
  38 #include <sys/kernel.h>
  39 #include <sys/sysctl.h>
  40 #include <sys/systm.h>
  41 #include <sys/module.h>
  42 #include <sys/malloc.h>
  43 #include <sys/conf.h>
  44 #include <sys/vnode.h>
  45 #include <sys/queue.h>
  46 #include <sys/device.h>
  47 #include <machine/stdarg.h>
  48
  49 #define cdevsw_ALLOCSTART       (NUMCDEVSW/2)
  50
  51 MALLOC_DEFINE(M_DEVT, "dev_t", "dev_t storage");
  52
  53 /*
  54  * This is the number of hash-buckets.  Experiements with 'real-life'
  55  * udev_t's show that a prime halfway between two powers of two works
  56  * best.
  57  */
  58 #define DEVT_HASH 83
  59
  60 /* The number of dev_t's we can create before malloc(9) kick in.  */
  61 #define DEVT_STASH 50
  62
  63 static struct specinfo devt_stash[DEVT_STASH];
  64 static LIST_HEAD(, specinfo) dev_hash[DEVT_HASH];
  65 static LIST_HEAD(, specinfo) dev_free_list;
  66
  67 static int free_devt;
  68 SYSCTL_INT(_debug, OID_AUTO, free_devt, CTLFLAG_RW, &free_devt, 0, "");
  69 int dev_ref_debug = 0;
  70 SYSCTL_INT(_debug, OID_AUTO, dev_refs, CTLFLAG_RW, &dev_ref_debug, 0, "");
  71
  72 /*
  73  * dev_t and u_dev_t primitives.  Note that the major number is always
  74  * extracted from si_udev, not from si_devsw, because si_devsw is replaced
  75  * when a device is destroyed.
  76  */
  77 int
  78 major(dev_t x)
  79 {
  80         if (x == NODEV)
  81                 return NOUDEV;
  82         return((x->si_udev >> 8) & 0xff);
  83 }
  84
  85 int
  86 minor(dev_t x)
  87 {
  88         if (x == NODEV)
  89                 return NOUDEV;
  90         return(x->si_udev & 0xffff00ff);
  91 }
  92
  93 int
  94 lminor(dev_t x)
  95 {
  96         int i;
  97
  98         if (x == NODEV)
  99                 return NOUDEV;
 100         i = minor(x);
 101         return ((i & 0xff) | (i >> 8));
 102 }
 103
 104 /*
 105  * This is a bit complex because devices are always created relative to
 106  * a particular cdevsw, including 'hidden' cdevsw's (such as the raw device
 107  * backing a disk subsystem overlay), so we have to compare both the
 108  * devsw and udev fields to locate the correct device.
 109  *
 110  * The device is created if it does not already exist.  If SI_ADHOC is not
 111  * set the device will be referenced (once) and SI_ADHOC will be set.
 112  * The caller must explicitly add additional references to the device if
 113  * the caller wishes to track additional references.
 114  */
 115 static
 116 dev_t
 117 hashdev(struct cdevsw *devsw, int x, int y)
 118 {
 119         struct specinfo *si;
 120         udev_t  udev;
 121         int hash;
 122         static int stashed;
 123
 124         udev = makeudev(x, y);
 125         hash = udev % DEVT_HASH;
 126         LIST_FOREACH(si, &dev_hash[hash], si_hash) {
 127                 if (si->si_devsw == devsw && si->si_udev == udev)
 128                         return (si);
 129         }
 130         if (stashed >= DEVT_STASH) {
 131                 MALLOC(si, struct specinfo *, sizeof(*si), M_DEVT,
 132                     M_WAITOK|M_USE_RESERVE|M_ZERO);
 133         } else if (LIST_FIRST(&dev_free_list)) {
 134                 si = LIST_FIRST(&dev_free_list);
 135                 LIST_REMOVE(si, si_hash);
 136         } else {
 137                 si = devt_stash + stashed++;
 138                 si->si_flags |= SI_STASHED;
 139         }
 140         si->si_devsw = devsw;
 141         si->si_flags |= SI_HASHED | SI_ADHOC;
 142         si->si_udev = udev;
 143         si->si_refs = 1;
 144         LIST_INSERT_HEAD(&dev_hash[hash], si, si_hash);
 145         si->si_port = devsw->d_port;
 146         devsw->d_clone(si);
 147         if (devsw != &dead_cdevsw)
 148                 ++devsw->d_refs;
 149         if (dev_ref_debug) {
 150                 printf("create    dev %p %s(minor=%08x) refs=%d\n",
 151                         si, devtoname(si), uminor(si->si_udev),
 152                         si->si_refs);
 153         }
 154         return (si);
 155 }
 156
 157 /*
 158  * Convert a device pointer to a device number
 159  */
 160 udev_t
 161 dev2udev(dev_t x)
 162 {
 163         if (x == NODEV)
 164                 return NOUDEV;
 165         return (x->si_udev);
 166 }
 167
 168 /*
 169  * Convert a device number to a device pointer.  The device is referenced
 170  * ad-hoc, meaning that the caller should call reference_dev() if it wishes
 171  * to keep ahold of the returned structure long term.
 172  *
 173  * The returned device is associated with the currently installed cdevsw
 174  * for the requested major number.  NODEV is returned if the major number
 175  * has not been registered.
 176  */
 177 dev_t
 178 udev2dev(udev_t x, int b)
 179 {
 180         dev_t dev;
 181         struct cdevsw *devsw;
 182
 183         if (x == NOUDEV || b != 0)
 184                 return(NODEV);
 185         devsw = cdevsw_get(umajor(x), uminor(x));
 186         if (devsw == NULL)
 187                 return(NODEV);
 188         dev = hashdev(devsw, umajor(x), uminor(x));
 189         return(dev);
 190 }
 191
 192 int
 193 dev_is_good(dev_t dev)
 194 {
 195         if (dev != NODEV && dev->si_devsw != &dead_cdevsw)
 196                 return(1);
 197         return(0);
 198 }
 199
 200 /*
 201  * Various user device number extraction and conversion routines
 202  */
 203 int
 204 uminor(udev_t dev)
 205 {
 206         return(dev & 0xffff00ff);
 207 }
 208
 209 int
 210 umajor(udev_t dev)
 211 {
 212         return((dev & 0xff00) >> 8);
 213 }
 214
 215 udev_t
 216 makeudev(int x, int y)
 217 {
 218         return ((x << 8) | y);
 219 }
 220
 221 /*
 222  * Create an internal or external device.
 223  *
 224  * Device majors can be overloaded and used directly by the kernel without
 225  * conflict, but userland will only see the particular device major that
 226  * has been installed with cdevsw_add().
 227  *
 228  * This routine creates and returns an unreferenced ad-hoc entry for the
 229  * device which will remain intact until the device is destroyed.  If the
 230  * caller intends to store the device pointer it must call reference_dev()
 231  * to retain a real reference to the device.
 232  *
 233  * If an entry already exists, this function will set (or override)
 234  * its cred requirements and name (XXX DEVFS interface).
 235  */
 236 dev_t
 237 make_dev(struct cdevsw *devsw, int minor, uid_t uid, gid_t gid,
 238         int perms, const char *fmt, ...)
 239 {
 240         dev_t   dev;
 241         __va_list ap;
 242         int i;
 243
 244         /*
 245          * compile the cdevsw and install the device
 246          */
 247         compile_devsw(devsw);
 248         dev = hashdev(devsw, devsw->d_maj, minor);
 249
 250         /*
 251          * Set additional fields (XXX DEVFS interface goes here)
 252          */
 253         __va_start(ap, fmt);
 254         i = kvprintf(fmt, NULL, dev->si_name, 32, ap);
 255         dev->si_name[i] = '\0';
 256         __va_end(ap);
 257
 258         return (dev);
 259 }
 260
 261 /*
 262  * This function is similar to make_dev() but no cred information or name
 263  * need be specified.
 264  */
 265 dev_t
 266 make_adhoc_dev(struct cdevsw *devsw, int minor)
 267 {
 268         dev_t dev;
 269
 270         dev = hashdev(devsw, devsw->d_maj, minor);
 271         return(dev);
 272 }
 273
 274 /*
 275  * This function is similar to make_dev() except the new device is created
 276  * using an old device as a template.
 277  */
 278 dev_t
 279 make_sub_dev(dev_t odev, int minor)
 280 {
 281         dev_t   dev;
 282
 283         dev = hashdev(odev->si_devsw, umajor(odev->si_udev), minor);
 284
 285         /*
 286          * Copy cred requirements and name info XXX DEVFS.
 287          */
 288         if (dev->si_name[0] == 0 && odev->si_name[0])
 289                 bcopy(odev->si_name, dev->si_name, sizeof(dev->si_name));
 290         return (dev);
 291 }
 292
 293 /*
 294  * destroy_dev() removes the adhoc association for a device and revectors
 295  * its devsw to &dead_cdevsw.
 296  *
 297  * This routine releases the reference count associated with the ADHOC
 298  * entry, plus releases the reference count held by the caller.  What this
 299  * means is that you should not call destroy_dev(make_dev(...)), because
 300  * make_dev() does not bump the reference count (beyond what it needs to
 301  * create the ad-hoc association).  Any procedure that intends to destroy
 302  * a device must have its own reference to it first.
 303  */
 304 void
 305 destroy_dev(dev_t dev)
 306 {
 307         int hash;
 308
 309         if (dev == NODEV)
 310                 return;
 311         if ((dev->si_flags & SI_ADHOC) == 0) {
 312                 release_dev(dev);
 313                 return;
 314         }
 315         if (dev_ref_debug) {
 316                 printf("destroy   dev %p %s(minor=%08x) refs=%d\n",
 317                         dev, devtoname(dev), uminor(dev->si_udev),
 318                         dev->si_refs);
 319         }
 320         if (dev->si_refs < 2) {
 321                 printf("destroy_dev(): too few references on device! "
 322                         "%p %s(minor=%08x) refs=%d\n",
 323                     dev, devtoname(dev), uminor(dev->si_udev),
 324                     dev->si_refs);
 325         }
 326         dev->si_flags &= ~SI_ADHOC;
 327         if (dev->si_flags & SI_HASHED) {
 328                 hash = dev->si_udev % DEVT_HASH;
 329                 LIST_REMOVE(dev, si_hash);
 330                 dev->si_flags &= ~SI_HASHED;
 331         }
 332
 333         /*
 334          * We have to release the cdevsw reference before we replace the
 335          * device switch with dead_cdevsw.
 336          */
 337         if (dead_cdevsw.d_port == NULL)
 338                 compile_devsw(&dead_cdevsw);
 339         if (dev->si_devsw && dev->si_devsw != &dead_cdevsw)
 340                 cdevsw_release(dev->si_devsw);
 341         dev->si_drv1 = NULL;
 342         dev->si_drv2 = NULL;
 343         dev->si_devsw = &dead_cdevsw;
 344         dev->si_port = dev->si_devsw->d_port;
 345         --dev->si_refs;         /* release adhoc association reference */
 346         release_dev(dev);       /* release callers reference */
 347 }
 348
 349 /*
 350  * Destroy all ad-hoc device associations associated with a domain within a
 351  * device switch.  Only the minor numbers are included in the mask/match
 352  * values.
 353  *
 354  * Unlike the cdevsw functions whos link structures do not contain
 355  * any major bits, this function scans through the dev list via si_udev
 356  * which is a 32 bit field that contains both major and minor bits.
 357  * Because of this, we must mask the minor bits in the passed mask variable
 358  * to allow -1 to be specified generically.
 359  *
 360  * The caller must not include any major bits in the match value.
 361  */
 362 void
 363 destroy_all_dev(struct cdevsw *devsw, u_int mask, u_int match)
 364 {
 365         int i;
 366         dev_t dev;
 367         dev_t ndev;
 368
 369         mask = uminor(mask);
 370         for (i = 0; i < DEVT_HASH; ++i) {
 371                 ndev = LIST_FIRST(&dev_hash[i]);
 372                 while ((dev = ndev) != NULL) {
 373                     ndev = LIST_NEXT(dev, si_hash);
 374                     KKASSERT(dev->si_flags & SI_ADHOC);
 375                     if (dev->si_devsw == devsw &&
 376                         (dev->si_udev & mask) == match
 377                     ) {
 378                         ++dev->si_refs;
 379                         destroy_dev(dev);
 380                     }
 381                 }
 382         }
 383 }
 384
 385 /*
 386  * Add a reference to a device.  Callers generally add their own references
 387  * when they are going to store a device node in a variable for long periods
 388  * of time, to prevent a disassociation from free()ing the node.
 389  *
 390  * Also note that a caller that intends to call destroy_dev() must first
 391  * obtain a reference on the device.  The ad-hoc reference you get with
 392  * make_dev() and friends is NOT sufficient to be able to call destroy_dev().
 393  */
 394 dev_t
 395 reference_dev(dev_t dev)
 396 {
 397         if (dev != NODEV) {
 398                 ++dev->si_refs;
 399                 if (dev_ref_debug) {
 400                         printf("reference dev %p %s(minor=%08x) refs=%d\n",
 401                             dev, devtoname(dev), uminor(dev->si_udev),
 402                             dev->si_refs);
 403                 }
 404         }
 405         return(dev);
 406 }
 407
 408 /*
 409  * release a reference on a device.  The device will be freed when the last
 410  * reference has been released.
 411  *
 412  * NOTE: we must use si_udev to figure out the original (major, minor),
 413  * because si_devsw could already be pointing at dead_cdevsw.
 414  */
 415 void
 416 release_dev(dev_t dev)
 417 {
 418         if (dev == NODEV)
 419                 return;
 420         if (free_devt) {
 421                 KKASSERT(dev->si_refs > 0);
 422         } else {
 423                 if (dev->si_refs <= 0) {
 424                         printf("Warning: extra release of dev %p(%s)\n",
 425                             dev, devtoname(dev));
 426                         free_devt = 0;  /* prevent bad things from occuring */
 427                 }
 428         }
 429         --dev->si_refs;
 430         if (dev_ref_debug) {
 431                 printf("release   dev %p %s(minor=%08x) refs=%d\n",
 432                         dev, devtoname(dev), uminor(dev->si_udev),
 433                         dev->si_refs);
 434         }
 435         if (dev->si_refs == 0) {
 436                 if (dev->si_flags & SI_ADHOC) {
 437                         printf("Warning: illegal final release on ADHOC"
 438                                 " device %p(%s), the device was never"
 439                                 " destroyed!\n",
 440                                 dev, devtoname(dev));
 441                 }
 442                 if (dev->si_flags & SI_HASHED) {
 443                         printf("Warning: last release on device, no call"
 444                                 " to destroy_dev() was made! dev %p(%s)\n",
 445                                 dev, devtoname(dev));
 446                         dev->si_refs = 3;
 447                         destroy_dev(dev);
 448                         dev->si_refs = 0;
 449                 }
 450                 if (SLIST_FIRST(&dev->si_hlist) != NULL) {
 451                         printf("Warning: last release on device, vnode"
 452                                 " associations still exist! dev %p(%s)\n",
 453                                 dev, devtoname(dev));
 454                         free_devt = 0;  /* prevent bad things from occuring */
 455                 }
 456                 if (dev->si_devsw && dev->si_devsw != &dead_cdevsw) {
 457                         cdevsw_release(dev->si_devsw);
 458                         dev->si_devsw = NULL;
 459                 }
 460                 if (free_devt) {
 461                         if (dev->si_flags & SI_STASHED) {
 462                                 bzero(dev, sizeof(*dev));
 463                                 LIST_INSERT_HEAD(&dev_free_list, dev, si_hash);
 464                         } else {
 465                                 FREE(dev, M_DEVT);
 466                         }
 467                 }
 468         }
 469 }
 470
 471 const char *
 472 devtoname(dev_t dev)
 473 {
 474         int mynor;
 475         int len;
 476         char *p;
 477         const char *dname;
 478
 479         if (dev == NODEV)
 480                 return("#nodev");
 481         if (dev->si_name[0] == '#' || dev->si_name[0] == '\0') {
 482                 p = dev->si_name;
 483                 len = sizeof(dev->si_name);
 484                 if ((dname = dev_dname(dev)) != NULL)
 485                         snprintf(p, len, "#%s/", dname);
 486                 else
 487                         snprintf(p, len, "#%d/", major(dev));
 488                 len -= strlen(p);
 489                 p += strlen(p);
 490                 mynor = minor(dev);
 491                 if (mynor < 0 || mynor > 255)
 492                         snprintf(p, len, "%#x", (u_int)mynor);
 493                 else
 494                         snprintf(p, len, "%d", mynor);
 495         }
 496         return (dev->si_name);
 497 }
 498