The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_conf.c

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    1 /*-
    2  * Copyright (c) 1999-2002 Poul-Henning Kamp
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  *
   14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   24  * SUCH DAMAGE.
   25  */
   26 
   27 #include <sys/cdefs.h>
   28 __FBSDID("$FreeBSD: releng/5.2/sys/kern/kern_conf.c 120560 2003-09-28 20:50:36Z phk $");
   29 
   30 #include <sys/param.h>
   31 #include <sys/kernel.h>
   32 #include <sys/systm.h>
   33 #include <sys/bio.h>
   34 #include <sys/lock.h>
   35 #include <sys/mutex.h>
   36 #include <sys/sysctl.h>
   37 #include <sys/module.h>
   38 #include <sys/malloc.h>
   39 #include <sys/conf.h>
   40 #include <sys/vnode.h>
   41 #include <sys/queue.h>
   42 #include <sys/poll.h>
   43 #include <sys/ctype.h>
   44 #include <machine/stdarg.h>
   45 
   46 static MALLOC_DEFINE(M_DEVT, "dev_t", "dev_t storage");
   47 
   48 /* Built at compile time from sys/conf/majors */
   49 extern unsigned char reserved_majors[256];
   50 
   51 /*
   52  * This is the number of hash-buckets.  Experiements with 'real-life'
   53  * udev_t's show that a prime halfway between two powers of two works
   54  * best.
   55  */
   56 #define DEVT_HASH 83
   57 
   58 /* The number of dev_t's we can create before malloc(9) kick in.  */
   59 #define DEVT_STASH 50
   60 
   61 static struct cdev devt_stash[DEVT_STASH];
   62 
   63 static LIST_HEAD(, cdev) dev_hash[DEVT_HASH];
   64 
   65 static LIST_HEAD(, cdev) dev_free;
   66 
   67 static int ready_for_devs;
   68 
   69 static int free_devt;
   70 SYSCTL_INT(_debug, OID_AUTO, free_devt, CTLFLAG_RW, &free_devt, 0, "");
   71 
   72 int
   73 nullop(void)
   74 {
   75 
   76         return (0);
   77 }
   78 
   79 int
   80 eopnotsupp(void)
   81 {
   82 
   83         return (EOPNOTSUPP);
   84 }
   85 
   86 static int
   87 enxio(void)
   88 {
   89         return (ENXIO);
   90 }
   91 
   92 static int
   93 enodev(void)
   94 {
   95         return (ENODEV);
   96 }
   97 
   98 /* Define a dead_cdevsw for use when devices leave unexpectedly. */
   99 
  100 #define dead_open       (d_open_t *)enxio
  101 #define dead_close      (d_close_t *)enxio
  102 #define dead_read       (d_read_t *)enxio
  103 #define dead_write      (d_write_t *)enxio
  104 #define dead_ioctl      (d_ioctl_t *)enxio
  105 #define dead_poll       (d_poll_t *)enodev
  106 #define dead_mmap       (d_mmap_t *)enodev
  107 
  108 static void
  109 dead_strategy(struct bio *bp)
  110 {
  111 
  112         biofinish(bp, NULL, ENXIO);
  113 }
  114 
  115 #define dead_dump       (dumper_t *)enxio
  116 #define dead_kqfilter   (d_kqfilter_t *)enxio
  117 
  118 static struct cdevsw dead_cdevsw = {
  119         .d_open =       dead_open,
  120         .d_close =      dead_close,
  121         .d_read =       dead_read,
  122         .d_write =      dead_write,
  123         .d_ioctl =      dead_ioctl,
  124         .d_poll =       dead_poll,
  125         .d_mmap =       dead_mmap,
  126         .d_strategy =   dead_strategy,
  127         .d_name =       "dead",
  128         .d_maj =        255,
  129         .d_dump =       dead_dump,
  130         .d_kqfilter =   dead_kqfilter
  131 };
  132 
  133 /* Default methods if driver does not specify method */
  134 
  135 #define null_open       (d_open_t *)nullop
  136 #define null_close      (d_close_t *)nullop
  137 #define no_read         (d_read_t *)enodev
  138 #define no_write        (d_write_t *)enodev
  139 #define no_ioctl        (d_ioctl_t *)enodev
  140 #define no_mmap         (d_mmap_t *)enodev
  141 
  142 static int
  143 no_kqfilter(dev_t dev __unused, struct knote *kn __unused)
  144 {
  145 
  146         return (1);
  147 }
  148 
  149 static void
  150 no_strategy(struct bio *bp)
  151 {
  152 
  153         biofinish(bp, NULL, ENODEV);
  154 }
  155 
  156 static int
  157 no_poll(dev_t dev __unused, int events, struct thread *td __unused)
  158 {
  159         /*
  160          * Return true for read/write.  If the user asked for something
  161          * special, return POLLNVAL, so that clients have a way of
  162          * determining reliably whether or not the extended
  163          * functionality is present without hard-coding knowledge
  164          * of specific filesystem implementations.
  165          * Stay in sync with vop_nopoll().
  166          */
  167         if (events & ~POLLSTANDARD)
  168                 return (POLLNVAL);
  169 
  170         return (events & (POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM));
  171 }
  172 
  173 #define no_dump         (dumper_t *)enodev
  174 
  175 struct cdevsw *
  176 devsw(dev_t dev)
  177 {
  178         if (dev->si_devsw)
  179                 return (dev->si_devsw);
  180         return (&dead_cdevsw);
  181 }
  182 
  183 /*
  184  * dev_t and u_dev_t primitives
  185  */
  186 
  187 int
  188 major(dev_t x)
  189 {
  190         if (x == NODEV)
  191                 return NOUDEV;
  192         return((x->si_udev >> 8) & 0xff);
  193 }
  194 
  195 int
  196 minor(dev_t x)
  197 {
  198         if (x == NODEV)
  199                 return NOUDEV;
  200         return(x->si_udev & 0xffff00ff);
  201 }
  202 
  203 int
  204 dev2unit(dev_t x)
  205 {
  206         int i;
  207 
  208         if (x == NODEV)
  209                 return NOUDEV;
  210         i = minor(x);
  211         return ((i & 0xff) | (i >> 8));
  212 }
  213 
  214 int
  215 unit2minor(int unit)
  216 {
  217 
  218         KASSERT(unit <= 0xffffff, ("Invalid unit (%d) in unit2minor", unit));
  219         return ((unit & 0xff) | ((unit << 8) & ~0xffff));
  220 }
  221 
  222 static dev_t
  223 allocdev(void)
  224 {
  225         static int stashed;
  226         struct cdev *si;
  227 
  228         if (LIST_FIRST(&dev_free)) {
  229                 si = LIST_FIRST(&dev_free);
  230                 LIST_REMOVE(si, si_hash);
  231         } else if (stashed >= DEVT_STASH) {
  232                 MALLOC(si, struct cdev *, sizeof(*si), M_DEVT,
  233                     M_USE_RESERVE | M_ZERO | M_WAITOK);
  234         } else {
  235                 si = devt_stash + stashed++;
  236                 bzero(si, sizeof *si);
  237                 si->si_flags |= SI_STASHED;
  238         }
  239         si->__si_namebuf[0] = '\0';
  240         si->si_name = si->__si_namebuf;
  241         LIST_INIT(&si->si_children);
  242         TAILQ_INIT(&si->si_snapshots);
  243         return (si);
  244 }
  245 
  246 dev_t
  247 makedev(int x, int y)
  248 {
  249         struct cdev *si;
  250         udev_t  udev;
  251         int hash;
  252 
  253         if (x == umajor(NOUDEV) && y == uminor(NOUDEV))
  254                 panic("makedev of NOUDEV");
  255         udev = (x << 8) | y;
  256         hash = udev % DEVT_HASH;
  257         LIST_FOREACH(si, &dev_hash[hash], si_hash) {
  258                 if (si->si_udev == udev)
  259                         return (si);
  260         }
  261         si = allocdev();
  262         si->si_udev = udev;
  263         LIST_INSERT_HEAD(&dev_hash[hash], si, si_hash);
  264         return (si);
  265 }
  266 
  267 void
  268 freedev(dev_t dev)
  269 {
  270 
  271         if (!free_devt)
  272                 return;
  273         if (SLIST_FIRST(&dev->si_hlist))
  274                 return;
  275         if (dev->si_devsw || dev->si_drv1 || dev->si_drv2)
  276                 return;
  277         LIST_REMOVE(dev, si_hash);
  278         if (dev->si_flags & SI_STASHED) {
  279                 bzero(dev, sizeof(*dev));
  280                 dev->si_flags |= SI_STASHED;
  281                 LIST_INSERT_HEAD(&dev_free, dev, si_hash);
  282         } else {
  283                 FREE(dev, M_DEVT);
  284         }
  285 }
  286 
  287 udev_t
  288 dev2udev(dev_t x)
  289 {
  290         if (x == NODEV)
  291                 return NOUDEV;
  292         return (x->si_udev);
  293 }
  294 
  295 dev_t
  296 udev2dev(udev_t x, int b)
  297 {
  298 
  299         if (x == NOUDEV)
  300                 return (NODEV);
  301         switch (b) {
  302                 case 0:
  303                         return makedev(umajor(x), uminor(x));
  304                 case 1:
  305                         return (NODEV);
  306                 default:
  307                         Debugger("udev2dev(...,X)");
  308                         return NODEV;
  309         }
  310 }
  311 
  312 int
  313 uminor(udev_t dev)
  314 {
  315         return(dev & 0xffff00ff);
  316 }
  317 
  318 int
  319 umajor(udev_t dev)
  320 {
  321         return((dev & 0xff00) >> 8);
  322 }
  323 
  324 udev_t
  325 makeudev(int x, int y)
  326 {
  327         return ((x << 8) | y);
  328 }
  329 
  330 dev_t
  331 make_dev(struct cdevsw *devsw, int minor, uid_t uid, gid_t gid, int perms, const char *fmt, ...)
  332 {
  333         dev_t   dev;
  334         va_list ap;
  335         int i;
  336 
  337         KASSERT((minor & ~0xffff00ff) == 0,
  338             ("Invalid minor (0x%x) in make_dev", minor));
  339 
  340         if (devsw->d_open == NULL)      devsw->d_open = null_open;
  341         if (devsw->d_close == NULL)     devsw->d_close = null_close;
  342         if (devsw->d_read == NULL)      devsw->d_read = no_read;
  343         if (devsw->d_write == NULL)     devsw->d_write = no_write;
  344         if (devsw->d_ioctl == NULL)     devsw->d_ioctl = no_ioctl;
  345         if (devsw->d_poll == NULL)      devsw->d_poll = no_poll;
  346         if (devsw->d_mmap == NULL)      devsw->d_mmap = no_mmap;
  347         if (devsw->d_strategy == NULL)  devsw->d_strategy = no_strategy;
  348         if (devsw->d_dump == NULL)      devsw->d_dump = no_dump;
  349         if (devsw->d_kqfilter == NULL)  devsw->d_kqfilter = no_kqfilter;
  350 
  351         if (devsw->d_maj == MAJOR_AUTO) {
  352                 for (i = NUMCDEVSW - 1; i > 0; i--)
  353                         if (reserved_majors[i] != i)
  354                                 break;
  355                 KASSERT(i > 0, ("Out of major numbers (%s)", devsw->d_name));
  356                 devsw->d_maj = i;
  357                 reserved_majors[i] = i;
  358         } else {
  359                 if (devsw->d_maj == 256)        /* XXX: tty_cons.c is magic */
  360                         devsw->d_maj = 0;       
  361                 KASSERT(devsw->d_maj >= 0 && devsw->d_maj < 256,
  362                     ("Invalid major (%d) in make_dev", devsw->d_maj));
  363                 if (reserved_majors[devsw->d_maj] != devsw->d_maj) {
  364                         printf("WARNING: driver \"%s\" used %s %d\n",
  365                             devsw->d_name, "unreserved major device number",
  366                             devsw->d_maj);
  367                         reserved_majors[devsw->d_maj] = devsw->d_maj;
  368                 }
  369         }
  370 
  371         if (!ready_for_devs) {
  372                 printf("WARNING: Driver mistake: make_dev(%s) called before SI_SUB_DRIVERS\n",
  373                        fmt);
  374                 /* XXX panic here once drivers are cleaned up */
  375         }
  376 
  377         dev = makedev(devsw->d_maj, minor);
  378         if (dev->si_flags & SI_CHEAPCLONE &&
  379             dev->si_flags & SI_NAMED &&
  380             dev->si_devsw == devsw) {
  381                 /*
  382                  * This is allowed as it removes races and generally
  383                  * simplifies cloning devices.
  384                  */
  385                 return (dev);
  386         }
  387         if (dev->si_flags & SI_NAMED) {
  388                 printf( "WARNING: Driver mistake: repeat make_dev(\"%s\")\n",
  389                     dev->si_name);
  390                 panic("don't do that");
  391         }
  392         va_start(ap, fmt);
  393         i = vsnrprintf(dev->__si_namebuf, sizeof dev->__si_namebuf, 32, fmt, ap);
  394         if (i > (sizeof dev->__si_namebuf - 1)) {
  395                 printf("WARNING: Device name truncated! (%s)", 
  396                     dev->__si_namebuf);
  397         }
  398         va_end(ap);
  399         dev->si_devsw = devsw;
  400         dev->si_uid = uid;
  401         dev->si_gid = gid;
  402         dev->si_mode = perms;
  403         dev->si_flags |= SI_NAMED;
  404 
  405         devfs_create(dev);
  406         return (dev);
  407 }
  408 
  409 int
  410 dev_named(dev_t pdev, const char *name)
  411 {
  412         dev_t cdev;
  413 
  414         if (strcmp(devtoname(pdev), name) == 0)
  415                 return (1);
  416         LIST_FOREACH(cdev, &pdev->si_children, si_siblings)
  417                 if (strcmp(devtoname(cdev), name) == 0)
  418                         return (1);
  419         return (0);
  420 }
  421 
  422 void
  423 dev_depends(dev_t pdev, dev_t cdev)
  424 {
  425 
  426         cdev->si_parent = pdev;
  427         cdev->si_flags |= SI_CHILD;
  428         LIST_INSERT_HEAD(&pdev->si_children, cdev, si_siblings);
  429 }
  430 
  431 dev_t
  432 make_dev_alias(dev_t pdev, const char *fmt, ...)
  433 {
  434         dev_t   dev;
  435         va_list ap;
  436         int i;
  437 
  438         dev = allocdev();
  439         dev->si_flags |= SI_ALIAS;
  440         dev->si_flags |= SI_NAMED;
  441         dev_depends(pdev, dev);
  442         va_start(ap, fmt);
  443         i = vsnrprintf(dev->__si_namebuf, sizeof dev->__si_namebuf, 32, fmt, ap);
  444         if (i > (sizeof dev->__si_namebuf - 1)) {
  445                 printf("WARNING: Device name truncated! (%s)", 
  446                     dev->__si_namebuf);
  447         }
  448         va_end(ap);
  449 
  450         devfs_create(dev);
  451         return (dev);
  452 }
  453 
  454 void
  455 destroy_dev(dev_t dev)
  456 {
  457         
  458         if (!(dev->si_flags & SI_NAMED)) {
  459                 printf( "WARNING: Driver mistake: destroy_dev on %d/%d\n",
  460                     major(dev), minor(dev));
  461                 panic("don't do that");
  462         }
  463                 
  464         devfs_destroy(dev);
  465         if (dev->si_flags & SI_CHILD) {
  466                 LIST_REMOVE(dev, si_siblings);
  467                 dev->si_flags &= ~SI_CHILD;
  468         }
  469         while (!LIST_EMPTY(&dev->si_children))
  470                 destroy_dev(LIST_FIRST(&dev->si_children));
  471         dev->si_drv1 = 0;
  472         dev->si_drv2 = 0;
  473         dev->si_devsw = 0;
  474         bzero(&dev->__si_u, sizeof(dev->__si_u));
  475         dev->si_flags &= ~SI_NAMED;
  476         dev->si_flags &= ~SI_ALIAS;
  477         freedev(dev);
  478 }
  479 
  480 const char *
  481 devtoname(dev_t dev)
  482 {
  483         char *p;
  484         int mynor;
  485 
  486         if (dev->si_name[0] == '#' || dev->si_name[0] == '\0') {
  487                 p = dev->si_name;
  488                 if (devsw(dev))
  489                         sprintf(p, "#%s/", devsw(dev)->d_name);
  490                 else
  491                         sprintf(p, "#%d/", major(dev));
  492                 p += strlen(p);
  493                 mynor = minor(dev);
  494                 if (mynor < 0 || mynor > 255)
  495                         sprintf(p, "%#x", (u_int)mynor);
  496                 else
  497                         sprintf(p, "%d", mynor);
  498         }
  499         return (dev->si_name);
  500 }
  501 
  502 int
  503 dev_stdclone(char *name, char **namep, const char *stem, int *unit)
  504 {
  505         int u, i;
  506 
  507         i = strlen(stem);
  508         if (bcmp(stem, name, i) != 0)
  509                 return (0);
  510         if (!isdigit(name[i]))
  511                 return (0);
  512         u = 0;
  513         if (name[i] == '' && isdigit(name[i+1]))
  514                 return (0);
  515         while (isdigit(name[i])) {
  516                 u *= 10;
  517                 u += name[i++] - '';
  518         }
  519         if (u > 0xffffff)
  520                 return (0);
  521         *unit = u;
  522         if (namep)
  523                 *namep = &name[i];
  524         if (name[i]) 
  525                 return (2);
  526         return (1);
  527 }
  528 
  529 /*
  530  * Helper sysctl for devname(3).  We're given a {u}dev_t and return
  531  * the name, if any, registered by the device driver.
  532  */
  533 static int
  534 sysctl_devname(SYSCTL_HANDLER_ARGS)
  535 {
  536         int error;
  537         udev_t ud;
  538         dev_t dev;
  539 
  540         error = SYSCTL_IN(req, &ud, sizeof (ud));
  541         if (error)
  542                 return (error);
  543         if (ud == NOUDEV)
  544                 return(EINVAL);
  545         dev = makedev(umajor(ud), uminor(ud));
  546         if (dev->si_name[0] == '\0')
  547                 error = ENOENT;
  548         else
  549                 error = SYSCTL_OUT(req, dev->si_name, strlen(dev->si_name) + 1);
  550         freedev(dev);
  551         return (error);
  552 }
  553 
  554 SYSCTL_PROC(_kern, OID_AUTO, devname, CTLTYPE_OPAQUE|CTLFLAG_RW|CTLFLAG_ANYBODY,
  555         NULL, 0, sysctl_devname, "", "devname(3) handler");
  556 
  557 /*
  558  * Set ready_for_devs; prior to this point, device creation is not allowed.
  559  */     
  560 static void
  561 dev_set_ready(void *junk)
  562 {
  563         ready_for_devs = 1;
  564 }
  565 
  566 SYSINIT(dev_ready, SI_SUB_DEVFS, SI_ORDER_FIRST, dev_set_ready, NULL);

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