sys/kern/vfs_conf.c

   1 /*-
   2  * Copyright (c) 1999 Michael Smith
   3  * All rights reserved.
   4  * Copyright (c) 1999 Poul-Henning Kamp
   5  * All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  19  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  26  * SUCH DAMAGE.
  27  *
  28  *      $FreeBSD: src/sys/kern/vfs_conf.c,v 1.49.2.5 2003/01/07 11:56:53 joerg Exp $
  29  */
  30
  31 /*
  32  * Locate and mount the root filesystem.
  33  *
  34  * The root filesystem is detailed in the kernel environment variable
  35  * vfs.root.mountfrom, which is expected to be in the general format
  36  *
  37  * <vfsname>:[<path>]
  38  * vfsname   := the name of a VFS known to the kernel and capable
  39  *              of being mounted as root
  40  * path      := disk device name or other data used by the filesystem
  41  *              to locate its physical store
  42  *
  43  */
  44
  45 #include "opt_rootdevname.h"
  46
  47 #include <sys/param.h>
  48 #include <sys/kernel.h>
  49 #include <sys/systm.h>
  50 #include <sys/proc.h>
  51 #include <sys/vnode.h>
  52 #include <sys/mount.h>
  53 #include <sys/malloc.h>
  54 #include <sys/reboot.h>
  55 #include <sys/diskslice.h>
  56 #include <sys/conf.h>
  57 #include <sys/cons.h>
  58 #include <sys/kbio.h>
  59 #include <sys/device.h>
  60 #include <sys/disk.h>
  61 #include <sys/namecache.h>
  62 #include <sys/paths.h>
  63 #include <sys/thread2.h>
  64 #include <sys/nlookup.h>
  65 #include <sys/devfs.h>
  66 #include <sys/sysctl.h>
  67
  68 #include "opt_ddb.h"
  69 #ifdef DDB
  70 #include <ddb/ddb.h>
  71 #endif
  72
  73 MALLOC_DEFINE(M_MOUNT, "mount", "vfs mount structure");
  74
  75 #define ROOTNAME        "root_device"
  76
  77 struct vnode    *rootvnode;
  78 struct nchandle rootnch;
  79
  80 /*
  81  * The root specifiers we will try if RB_CDROM is specified.  Note that
  82  * with DEVFS we do not use the compatibility slice's whole-disk 'c'
  83  * partition.  Instead we just use the whole disk, e.g. cd0 or cd0s0.
  84  */
  85 static char *cdrom_rootdevnames[] = {
  86         "cd9660:cd0",   /* SCSI (including AHCI and SILI) */
  87         "cd9660:acd0",  /* NATA */
  88         "cd9660:cd1",   /* SCSI (including AHCI and SILI) */
  89         "cd9660:acd1",  /* NATA */
  90         "cd9660:cd8",   /* USB */
  91         "cd9660:cd9",   /* USB */
  92         NULL
  93 };
  94
  95 int vfs_mountroot_devfs(void);
  96 static void     vfs_mountroot(void *junk);
  97 static int      vfs_mountroot_try(const char *mountfrom);
  98 static int      vfs_mountroot_ask(void);
  99 static int      getline(char *cp, int limit);
 100
 101 /* legacy find-root code */
 102 char            *rootdevnames[2] = {NULL, NULL};
 103 static int      setrootbyname(char *name);
 104
 105 SYSINIT(mountroot, SI_SUB_MOUNT_ROOT, SI_ORDER_SECOND, vfs_mountroot, NULL);
 106
 107 static int wakedelay = 2;       /* delay before mounting root in seconds */
 108 TUNABLE_INT("vfs.root.wakedelay", &wakedelay);
 109
 110 /*
 111  * Find and mount the root filesystem
 112  */
 113 static void
 114 vfs_mountroot(void *junk)
 115 {
 116         cdev_t  save_rootdev = rootdev;
 117         int     i;
 118         int     dummy;
 119
 120         /*
 121          * Make sure all disk devices created so far have also been probed,
 122          * and also make sure that the newly created device nodes for
 123          * probed disks are ready, too.
 124          *
 125          * Messages can fly around here so get good synchronization
 126          * coverage.
 127          *
 128          * XXX - Delay some more (default: 2s) to help drivers which pickup
 129          *       devices asynchronously and are not caught by CAM's initial
 130          *       probe.
 131          */
 132         sync_devs();
 133         tsleep(&dummy, 0, "syncer", hz * wakedelay);
 134
 135
 136         /*
 137          * The root filesystem information is compiled in, and we are
 138          * booted with instructions to use it.
 139          */
 140 #ifdef ROOTDEVNAME
 141         if ((boothowto & RB_DFLTROOT) &&
 142             !vfs_mountroot_try(ROOTDEVNAME))
 143                 return;
 144 #endif
 145         /*
 146          * We are booted with instructions to prompt for the root filesystem,
 147          * or to use the compiled-in default when it doesn't exist.
 148          */
 149         if (boothowto & (RB_DFLTROOT | RB_ASKNAME)) {
 150                 if (!vfs_mountroot_ask())
 151                         return;
 152         }
 153
 154         /*
 155          * We've been given the generic "use CDROM as root" flag.  This is
 156          * necessary because one media may be used in many different
 157          * devices, so we need to search for them.
 158          */
 159         if (boothowto & RB_CDROM) {
 160                 for (i = 0; cdrom_rootdevnames[i] != NULL; i++) {
 161                         if (!vfs_mountroot_try(cdrom_rootdevnames[i]))
 162                                 return;
 163                 }
 164         }
 165
 166         /*
 167          * Try to use the value read by the loader from /etc/fstab, or
 168          * supplied via some other means.  This is the preferred
 169          * mechanism.
 170          */
 171         if (!vfs_mountroot_try(kgetenv("vfs.root.mountfrom")))
 172                 return;
 173
 174         /*
 175          * If a vfs set rootdev, try it (XXX VINUM HACK!)
 176          */
 177         if (save_rootdev != NULL) {
 178                 rootdev = save_rootdev;
 179                 if (!vfs_mountroot_try(""))
 180                         return;
 181         }
 182
 183         /*
 184          * Try values that may have been computed by the machine-dependant
 185          * legacy code.
 186          */
 187         if (rootdevnames[0] && !vfs_mountroot_try(rootdevnames[0]))
 188                 return;
 189         if (rootdevnames[1] && !vfs_mountroot_try(rootdevnames[1]))
 190                 return;
 191
 192         /*
 193          * If we have a compiled-in default, and haven't already tried it, try
 194          * it now.
 195          */
 196 #ifdef ROOTDEVNAME
 197         if (!(boothowto & RB_DFLTROOT))
 198                 if (!vfs_mountroot_try(ROOTDEVNAME))
 199                         return;
 200 #endif
 201
 202         /*
 203          * Everything so far has failed, prompt on the console if we haven't
 204          * already tried that.
 205          */
 206         if (!(boothowto & (RB_DFLTROOT | RB_ASKNAME)) && !vfs_mountroot_ask())
 207                 return;
 208         panic("Root mount failed, startup aborted.");
 209 }
 210
 211
 212 int
 213 vfs_mountroot_devfs(void)
 214 {
 215         struct vnode *vp;
 216         struct nchandle nch;
 217         struct nlookupdata nd;
 218         struct mount *mp;
 219         struct vfsconf *vfsp;
 220         int error;
 221         struct ucred *cred = proc0.p_ucred;
 222         const char *devfs_path, *init_chroot;
 223         char *dev_malloced = NULL;
 224
 225         if ((init_chroot = kgetenv("init_chroot")) != NULL) {
 226                 size_t l;
 227
 228                 l = strlen(init_chroot) + sizeof("/dev");
 229                 dev_malloced = kmalloc(l, M_MOUNT, M_WAITOK);
 230                 ksnprintf(dev_malloced, l, "%s/dev", init_chroot);
 231                 devfs_path = dev_malloced;
 232         } else {
 233                 devfs_path = "/dev";
 234         }
 235         /*
 236          * Lookup the requested path and extract the nch and vnode.
 237          */
 238         error = nlookup_init_raw(&nd,
 239              devfs_path, UIO_SYSSPACE, NLC_FOLLOW,
 240              cred, &rootnch);
 241
 242         if (error == 0) {
 243                 devfs_debug(DEVFS_DEBUG_DEBUG, "vfs_mountroot_devfs: nlookup_init is ok...\n");
 244                 if ((error = nlookup(&nd)) == 0) {
 245                         devfs_debug(DEVFS_DEBUG_DEBUG, "vfs_mountroot_devfs: nlookup is ok...\n");
 246                         if (nd.nl_nch.ncp->nc_vp == NULL) {
 247                                 devfs_debug(DEVFS_DEBUG_SHOW, "vfs_mountroot_devfs: nlookup: simply not found\n");
 248                                 error = ENOENT;
 249                         }
 250                 }
 251         }
 252         if (dev_malloced != NULL)
 253                 kfree(dev_malloced, M_MOUNT), dev_malloced = NULL;
 254         devfs_path = NULL;
 255         if (error) {
 256                 nlookup_done(&nd);
 257                 devfs_debug(DEVFS_DEBUG_SHOW, "vfs_mountroot_devfs: nlookup failed, error: %d\n", error);
 258                 return (error);
 259         }
 260
 261         /*
 262          * Extract the locked+refd ncp and cleanup the nd structure
 263          */
 264         nch = nd.nl_nch;
 265         cache_zero(&nd.nl_nch);
 266         nlookup_done(&nd);
 267
 268         /*
 269          * now we have the locked ref'd nch and unreferenced vnode.
 270          */
 271         vp = nch.ncp->nc_vp;
 272         if ((error = vget(vp, LK_EXCLUSIVE)) != 0) {
 273                 cache_put(&nch);
 274                 devfs_debug(DEVFS_DEBUG_SHOW, "vfs_mountroot_devfs: vget failed\n");
 275                 return (error);
 276         }
 277         cache_unlock(&nch);
 278
 279         if ((error = vinvalbuf(vp, V_SAVE, 0, 0)) != 0) {
 280                 cache_drop(&nch);
 281                 vput(vp);
 282                 devfs_debug(DEVFS_DEBUG_SHOW, "vfs_mountroot_devfs: vinvalbuf failed\n");
 283                 return (error);
 284         }
 285         if (vp->v_type != VDIR) {
 286                 cache_drop(&nch);
 287                 vput(vp);
 288                 devfs_debug(DEVFS_DEBUG_SHOW, "vfs_mountroot_devfs: vp is not VDIR\n");
 289                 return (ENOTDIR);
 290         }
 291
 292         vfsp = vfsconf_find_by_name("devfs");
 293
 294         /*
 295          * Allocate and initialize the filesystem.
 296          */
 297         mp = kmalloc(sizeof(struct mount), M_MOUNT, M_ZERO|M_WAITOK);
 298         mount_init(mp);
 299         vfs_busy(mp, LK_NOWAIT);
 300         mp->mnt_op = vfsp->vfc_vfsops;
 301         mp->mnt_vfc = vfsp;
 302         vfsp->vfc_refcount++;
 303         mp->mnt_stat.f_type = vfsp->vfc_typenum;
 304         mp->mnt_flag |= vfsp->vfc_flags & MNT_VISFLAGMASK;
 305         strncpy(mp->mnt_stat.f_fstypename, vfsp->vfc_name, MFSNAMELEN);
 306         mp->mnt_stat.f_owner = cred->cr_uid;
 307         vn_unlock(vp);
 308
 309         /*
 310          * Mount the filesystem.
 311          */
 312         error = VFS_MOUNT(mp, "/dev", NULL, cred);
 313
 314         vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
 315
 316         /*
 317          * Put the new filesystem on the mount list after root.  The mount
 318          * point gets its own mnt_ncmountpt (unless the VFS already set one
 319          * up) which represents the root of the mount.  The lookup code
 320          * detects the mount point going forward and checks the root of
 321          * the mount going backwards.
 322          *
 323          * It is not necessary to invalidate or purge the vnode underneath
 324          * because elements under the mount will be given their own glue
 325          * namecache record.
 326          */
 327         if (!error) {
 328                 if (mp->mnt_ncmountpt.ncp == NULL) {
 329                         /*
 330                          * allocate, then unlock, but leave the ref intact
 331                          */
 332                         cache_allocroot(&mp->mnt_ncmountpt, mp, NULL);
 333                         cache_unlock(&mp->mnt_ncmountpt);
 334                 }
 335                 mp->mnt_ncmounton = nch;                /* inherits ref */
 336                 nch.ncp->nc_flag |= NCF_ISMOUNTPT;
 337
 338                 /* XXX get the root of the fs and cache_setvp(mnt_ncmountpt...) */
 339                 mountlist_insert(mp, MNTINS_LAST);
 340                 vn_unlock(vp);
 341                 //checkdirs(&mp->mnt_ncmounton, &mp->mnt_ncmountpt);
 342                 error = vfs_allocate_syncvnode(mp);
 343                 if (error) {
 344                         devfs_debug(DEVFS_DEBUG_SHOW, "vfs_mountroot_devfs: vfs_allocate_syncvnode failed\n");
 345                 }
 346                 vfs_unbusy(mp);
 347                 error = VFS_START(mp, 0);
 348                 vrele(vp);
 349         } else {
 350                 vn_syncer_thr_stop(mp);
 351                 vfs_rm_vnodeops(mp, NULL, &mp->mnt_vn_coherency_ops);
 352                 vfs_rm_vnodeops(mp, NULL, &mp->mnt_vn_journal_ops);
 353                 vfs_rm_vnodeops(mp, NULL, &mp->mnt_vn_norm_ops);
 354                 vfs_rm_vnodeops(mp, NULL, &mp->mnt_vn_spec_ops);
 355                 vfs_rm_vnodeops(mp, NULL, &mp->mnt_vn_fifo_ops);
 356                 mp->mnt_vfc->vfc_refcount--;
 357                 vfs_unbusy(mp);
 358                 kfree(mp, M_MOUNT);
 359                 cache_drop(&nch);
 360                 vput(vp);
 361                 devfs_debug(DEVFS_DEBUG_SHOW, "vfs_mountroot_devfs: mount failed\n");
 362         }
 363
 364         devfs_debug(DEVFS_DEBUG_DEBUG, "rootmount_devfs done with error: %d\n", error);
 365         return (error);
 366 }
 367
 368
 369 /*
 370  * Mount (mountfrom) as the root filesystem.
 371  */
 372 static int
 373 vfs_mountroot_try(const char *mountfrom)
 374 {
 375         struct mount    *mp;
 376         char            *vfsname, *devname;
 377         int             error;
 378         char            patt[32];
 379         const char      *cp, *ep;
 380         char            *mf;
 381         struct proc     *p;
 382         struct vnode    *vp;
 383
 384         vfsname = NULL;
 385         devname = NULL;
 386         mp      = NULL;
 387         error   = EINVAL;
 388
 389         if (mountfrom == NULL)
 390                 return(error);          /* don't complain */
 391
 392         crit_enter();
 393         kprintf("Mounting root from %s\n", mountfrom);
 394         crit_exit();
 395
 396         cp = mountfrom;
 397         /* parse vfs name and devname */
 398         vfsname = kmalloc(MFSNAMELEN, M_MOUNT, M_WAITOK);
 399         devname = kmalloc(MNAMELEN, M_MOUNT, M_WAITOK);
 400         mf = kmalloc(MFSNAMELEN+MNAMELEN, M_MOUNT, M_WAITOK);
 401         for(;;) {
 402                 for (ep = cp; (*ep != 0) && (*ep != ';'); ep++);
 403                 bzero(vfsname, MFSNAMELEN);
 404                 bzero(devname, MNAMELEN);
 405                 bzero(mf, MFSNAMELEN+MNAMELEN);
 406                 strncpy(mf, cp, MFSNAMELEN+MNAMELEN);
 407
 408                 vfsname[0] = devname[0] = 0;
 409                 ksprintf(patt, "%%%d[a-z0-9]:%%%ds", MFSNAMELEN, MNAMELEN);
 410                 if (ksscanf(mf, patt, vfsname, devname) < 1)
 411                         goto end;
 412
 413                 /* allocate a root mount */
 414                 error = vfs_rootmountalloc(vfsname,
 415                                 devname[0] != 0 ? devname : ROOTNAME, &mp);
 416                 if (error != 0) {
 417                         kprintf("Can't allocate root mount for filesystem '%s': %d\n",
 418                                vfsname, error);
 419                         goto end;
 420                 }
 421                 mp->mnt_flag |= MNT_ROOTFS;
 422
 423                 /* do our best to set rootdev (really just for UFS) */
 424                 if (strcmp(vfsname, "hammer") != 0 &&
 425                     strcmp(vfsname, "hammer2") != 0 &&
 426                     (devname[0] != 0) && setrootbyname(devname)) {
 427                         kprintf("setrootbyname failed\n");
 428                 }
 429
 430                 /* If the root device is a type "memory disk", mount RW */
 431                 if (rootdev != NULL && dev_is_good(rootdev) &&
 432                     (dev_dflags(rootdev) & D_MEMDISK)) {
 433                         mp->mnt_flag &= ~MNT_RDONLY;
 434                 }
 435
 436                 error = VFS_MOUNT(mp, NULL, NULL, proc0.p_ucred);
 437
 438                 if (!error)
 439                         break;
 440 end:
 441                 if(*ep == 0)
 442                         break;
 443                 cp = ep + 1;
 444         }
 445
 446         if (vfsname != NULL)
 447                 kfree(vfsname, M_MOUNT);
 448         if (devname != NULL)
 449                 kfree(devname, M_MOUNT);
 450         if (mf != NULL)
 451                 kfree(mf, M_MOUNT);
 452         if (error == 0) {
 453                 /* register with list of mounted filesystems */
 454                 mountlist_insert(mp, MNTINS_FIRST);
 455
 456                 /* sanity check system clock against root fs timestamp */
 457                 inittodr(mp->mnt_time);
 458
 459                 /* Get the vnode for '/'.  Set p->p_fd->fd_cdir to reference it. */
 460                 mp = mountlist_boot_getfirst();
 461                 if (VFS_ROOT(mp, &vp))
 462                         panic("cannot find root vnode");
 463                 if (mp->mnt_ncmountpt.ncp == NULL) {
 464                         cache_allocroot(&mp->mnt_ncmountpt, mp, vp);
 465                         cache_unlock(&mp->mnt_ncmountpt);       /* leave ref intact */
 466                 }
 467                 p = curproc;
 468                 p->p_fd->fd_cdir = vp;
 469                 vref(p->p_fd->fd_cdir);
 470                 p->p_fd->fd_rdir = vp;
 471                 vref(p->p_fd->fd_rdir);
 472                 vfs_cache_setroot(vp, cache_hold(&mp->mnt_ncmountpt));
 473                 vn_unlock(vp);                  /* leave ref intact */
 474                 cache_copy(&mp->mnt_ncmountpt, &p->p_fd->fd_ncdir);
 475                 cache_copy(&mp->mnt_ncmountpt, &p->p_fd->fd_nrdir);
 476
 477                 vfs_unbusy(mp);
 478                 if (mp->mnt_syncer == NULL) {
 479                         error = vfs_allocate_syncvnode(mp);
 480                         if (error)
 481                                 kprintf("Warning: no syncer vp for root!\n");
 482                         error = 0;
 483                 }
 484                 VFS_START( mp, 0 );
 485         } else {
 486                 if (mp != NULL) {
 487                         vn_syncer_thr_stop(mp);
 488                         vfs_unbusy(mp);
 489                         kfree(mp, M_MOUNT);
 490                 }
 491                 kprintf("Root mount failed: %d\n", error);
 492         }
 493         return(error);
 494 }
 495
 496
 497 static void
 498 vfs_mountroot_ask_callback(char *name, cdev_t dev, bool is_alias,
 499     void *arg __unused)
 500 {
 501         if (!is_alias && dev_is_good(dev) && (dev_dflags(dev) & D_DISK))
 502                 kprintf(" \"%s\" ", name);
 503 }
 504
 505
 506 /*
 507  * Spin prompting on the console for a suitable root filesystem
 508  */
 509 static int
 510 vfs_mountroot_ask(void)
 511 {
 512         char name[128];
 513         int llimit = 100;
 514
 515         kprintf("\nManual root filesystem specification:\n");
 516         kprintf("  <fstype>:<device>  Specify root (e.g. ufs:da0s1a)\n");
 517         kprintf("  ?                  List valid disk boot devices\n");
 518         kprintf("  panic              Just panic\n");
 519         kprintf("  abort              Abort manual input\n");
 520         while (llimit--) {
 521                 kprintf("\nmountroot> ");
 522
 523                 if (getline(name, 128) < 0)
 524                         break;
 525                 if (name[0] == 0) {
 526                         ;
 527                 } else if (name[0] == '?') {
 528                         kprintf("Possibly valid devices for root FS:\n");
 529                         //enumerate all disk devices
 530                         devfs_scan_callback(vfs_mountroot_ask_callback, NULL);
 531                         kprintf("\n");
 532                         continue;
 533                 } else if (strcmp(name, "panic") == 0) {
 534                         panic("panic from console");
 535                 } else if (strcmp(name, "abort") == 0) {
 536                         break;
 537                 } else if (vfs_mountroot_try(name) == 0) {
 538                         return(0);
 539                 }
 540         }
 541         return(1);
 542 }
 543
 544
 545 static int
 546 getline(char *cp, int limit)
 547 {
 548         char *lp;
 549         int dummy;
 550         int c;
 551
 552         lp = cp;
 553         cnpoll(TRUE);
 554         for (;;) {
 555                 c = cncheckc();
 556
 557                 switch (c) {
 558                 case NOKEY:
 559                         tsleep(&dummy, 0, "cnpoll", hz / 25);
 560                         break;
 561                 case -1:
 562                         goto done;
 563                 case '\n':
 564                 case '\r':
 565                         kprintf("\n");
 566                         *lp++ = '\0';
 567                         c = 0;
 568                         goto done;
 569                 case '\b':
 570                 case '\177':
 571                         if (lp > cp) {
 572                                 kprintf("\b \b");
 573                                 lp--;
 574                         } else {
 575                                 kprintf("%c", 7);
 576                         }
 577                         continue;
 578                 case '#':
 579                         kprintf("#");
 580                         lp--;
 581                         if (lp < cp)
 582                                 lp = cp;
 583                         continue;
 584                 case 'u' & 037:
 585                         /* NOTE: '@' no longer processed here, used for H2 */
 586                         lp = cp;
 587                         kprintf("%c", '\n');
 588                         continue;
 589                 default:
 590                         if (lp - cp >= limit - 1) {
 591                                 kprintf("%c", 7);
 592                         } else {
 593                                 kprintf("%c", c);
 594                                 *lp++ = c;
 595                         }
 596                         continue;
 597                 }
 598         }
 599 done:
 600         cnpoll(FALSE);
 601         return c;
 602 }
 603
 604 /*
 605  * Convert a given name to the cdev_t of the disk-like device
 606  * it refers to.
 607  */
 608 cdev_t
 609 kgetdiskbyname(const char *name)
 610 {
 611         cdev_t rdev;
 612
 613         /*
 614          * Get the base name of the device
 615          */
 616         if (strncmp(name, __SYS_PATH_DEV, sizeof(__SYS_PATH_DEV) - 1) == 0)
 617                 name += sizeof(__SYS_PATH_DEV) - 1;
 618
 619         /*
 620          * Locate the device
 621          */
 622         rdev = devfs_find_device_by_name("%s", name);
 623         if (rdev == NULL) {
 624                 kprintf("no disk named '%s'\n", name);
 625         }
 626         /*
 627          * FOUND DEVICE
 628          */
 629         return(rdev);
 630 }
 631
 632 /*
 633  * Set rootdev to match (name), given that we expect it to
 634  * refer to a disk-like device.
 635  */
 636 static int
 637 setrootbyname(char *name)
 638 {
 639         cdev_t diskdev;
 640
 641         diskdev = kgetdiskbyname(name);
 642         if (diskdev != NULL) {
 643                 rootdev = diskdev;
 644                 return (0);
 645         }
 646         /* set to NULL if kgetdiskbyname() fails so that if the first rootdev is
 647          * found by fails to mount and the second one isn't found, mountroot_try
 648          * doesn't try again with the first one
 649          */
 650         rootdev = NULL;
 651         return (1);
 652 }
 653
 654 #ifdef DDB
 655 DB_SHOW_COMMAND(disk, db_getdiskbyname)
 656 {
 657         cdev_t dev;
 658
 659         if (modif[0] == '\0') {
 660                 db_error("usage: show disk/devicename");
 661                 return;
 662         }
 663         dev = kgetdiskbyname(modif);
 664         if (dev != NULL)
 665                 db_printf("cdev_t = %p\n", dev);
 666         else
 667                 db_printf("No disk device matched.\n");
 668 }
 669 #endif
 670
 671 static int
 672 vfs_sysctl_real_root(SYSCTL_HANDLER_ARGS)
 673 {
 674         char *real_root;
 675         size_t len;
 676         int error;
 677
 678         real_root = kgetenv("vfs.root.realroot");
 679
 680         if (real_root == NULL)
 681                 real_root = "";
 682
 683         len = strlen(real_root) + 1;
 684
 685         error = sysctl_handle_string(oidp, real_root, len, req);
 686
 687         return error;
 688 }
 689
 690 SYSCTL_PROC(_vfs, OID_AUTO, real_root,
 691             CTLTYPE_STRING | CTLFLAG_RD, 0, 0, vfs_sysctl_real_root,
 692             "A", "Real root mount string");