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 get_line(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 mp->mnt_pbuf_count = nswbuf_kva / NSWBUF_SPLIT; 303 vfsp->vfc_refcount++; 304 mp->mnt_stat.f_type = vfsp->vfc_typenum; 305 mp->mnt_flag |= vfsp->vfc_flags & MNT_VISFLAGMASK; 306 strncpy(mp->mnt_stat.f_fstypename, vfsp->vfc_name, MFSNAMELEN); 307 mp->mnt_stat.f_owner = cred->cr_uid; 308 vn_unlock(vp); 309 310 /* 311 * Mount the filesystem. 312 */ 313 error = VFS_MOUNT(mp, "/dev", NULL, cred); 314 315 vn_lock(vp, LK_EXCLUSIVE | LK_RETRY); 316 317 /* 318 * Put the new filesystem on the mount list after root. The mount 319 * point gets its own mnt_ncmountpt (unless the VFS already set one 320 * up) which represents the root of the mount. The lookup code 321 * detects the mount point going forward and checks the root of 322 * the mount going backwards. 323 * 324 * It is not necessary to invalidate or purge the vnode underneath 325 * because elements under the mount will be given their own glue 326 * namecache record. 327 */ 328 if (!error) { 329 if (mp->mnt_ncmountpt.ncp == NULL) { 330 /* 331 * allocate, then unlock, but leave the ref intact 332 */ 333 cache_allocroot(&mp->mnt_ncmountpt, mp, NULL); 334 cache_unlock(&mp->mnt_ncmountpt); 335 } 336 vn_unlock(vp); 337 mp->mnt_ncmounton = nch; /* inherits ref */ 338 cache_lock(&nch); 339 nch.ncp->nc_flag |= NCF_ISMOUNTPT; 340 cache_unlock(&nch); 341 vn_lock(vp, LK_EXCLUSIVE | LK_RETRY); 342 343 /* 344 * XXX get the root of the fs and 345 * cache_setvp(mnt_ncmountpt...) 346 */ 347 mountlist_insert(mp, MNTINS_LAST); 348 vn_unlock(vp); 349 //checkdirs(&mp->mnt_ncmounton, &mp->mnt_ncmountpt); 350 error = vfs_allocate_syncvnode(mp); 351 if (error) { 352 devfs_debug(DEVFS_DEBUG_SHOW, "vfs_mountroot_devfs: vfs_allocate_syncvnode failed\n"); 353 } 354 vfs_unbusy(mp); 355 error = VFS_START(mp, 0); 356 vrele(vp); 357 } else { 358 vn_syncer_thr_stop(mp); 359 vfs_rm_vnodeops(mp, NULL, &mp->mnt_vn_coherency_ops); 360 vfs_rm_vnodeops(mp, NULL, &mp->mnt_vn_journal_ops); 361 vfs_rm_vnodeops(mp, NULL, &mp->mnt_vn_norm_ops); 362 vfs_rm_vnodeops(mp, NULL, &mp->mnt_vn_spec_ops); 363 vfs_rm_vnodeops(mp, NULL, &mp->mnt_vn_fifo_ops); 364 mp->mnt_vfc->vfc_refcount--; 365 vfs_unbusy(mp); 366 kfree(mp, M_MOUNT); 367 cache_drop(&nch); 368 vput(vp); 369 devfs_debug(DEVFS_DEBUG_SHOW, "vfs_mountroot_devfs: mount failed\n"); 370 } 371 372 devfs_debug(DEVFS_DEBUG_DEBUG, "rootmount_devfs done with error: %d\n", error); 373 return (error); 374 } 375 376 377 /* 378 * Mount (mountfrom) as the root filesystem. 379 */ 380 static int 381 vfs_mountroot_try(const char *mountfrom) 382 { 383 struct mount *mp; 384 char *vfsname, *devname; 385 int error; 386 char patt[32]; 387 const char *cp, *ep; 388 char *mf; 389 struct proc *p; 390 struct vnode *vp; 391 392 vfsname = NULL; 393 devname = NULL; 394 mp = NULL; 395 error = EINVAL; 396 397 if (mountfrom == NULL) 398 return(error); /* don't complain */ 399 400 crit_enter(); 401 kprintf("Mounting root from %s\n", mountfrom); 402 crit_exit(); 403 404 cp = mountfrom; 405 /* parse vfs name and devname */ 406 vfsname = kmalloc(MFSNAMELEN, M_MOUNT, M_WAITOK); 407 devname = kmalloc(MNAMELEN, M_MOUNT, M_WAITOK); 408 mf = kmalloc(MFSNAMELEN+MNAMELEN, M_MOUNT, M_WAITOK); 409 for(;;) { 410 for (ep = cp; (*ep != 0) && (*ep != ';'); ep++); 411 bzero(vfsname, MFSNAMELEN); 412 bzero(devname, MNAMELEN); 413 bzero(mf, MFSNAMELEN+MNAMELEN); 414 strncpy(mf, cp, MFSNAMELEN+MNAMELEN); 415 416 vfsname[0] = devname[0] = 0; 417 ksprintf(patt, "%%%d[a-z0-9]:%%%ds", MFSNAMELEN, MNAMELEN); 418 if (ksscanf(mf, patt, vfsname, devname) < 1) 419 goto end; 420 421 /* allocate a root mount */ 422 error = vfs_rootmountalloc(vfsname, 423 devname[0] != 0 ? devname : ROOTNAME, &mp); 424 if (error != 0) { 425 kprintf("Can't allocate root mount for filesystem '%s': %d\n", 426 vfsname, error); 427 goto end; 428 } 429 mp->mnt_flag |= MNT_ROOTFS; 430 431 /* do our best to set rootdev (really just for UFS) */ 432 if (strcmp(vfsname, "hammer") != 0 && 433 strcmp(vfsname, "hammer2") != 0 && 434 (devname[0] != 0) && setrootbyname(devname)) { 435 kprintf("setrootbyname failed\n"); 436 } 437 438 /* If the root device is a type "memory disk", mount RW */ 439 if (rootdev != NULL && dev_is_good(rootdev) && 440 (dev_dflags(rootdev) & D_MEMDISK)) { 441 mp->mnt_flag &= ~MNT_RDONLY; 442 } 443 444 error = VFS_MOUNT(mp, NULL, NULL, proc0.p_ucred); 445 446 if (!error) 447 break; 448 end: 449 if(*ep == 0) 450 break; 451 cp = ep + 1; 452 } 453 454 if (vfsname != NULL) 455 kfree(vfsname, M_MOUNT); 456 if (devname != NULL) 457 kfree(devname, M_MOUNT); 458 if (mf != NULL) 459 kfree(mf, M_MOUNT); 460 if (error == 0) { 461 /* register with list of mounted filesystems */ 462 mountlist_insert(mp, MNTINS_FIRST); 463 464 /* sanity check system clock against root fs timestamp */ 465 inittodr(mp->mnt_time); 466 467 /* Get the vnode for '/'. Set p->p_fd->fd_cdir to reference it. */ 468 mp = mountlist_boot_getfirst(); 469 if (VFS_ROOT(mp, &vp)) 470 panic("cannot find root vnode"); 471 if (mp->mnt_ncmountpt.ncp == NULL) { 472 cache_allocroot(&mp->mnt_ncmountpt, mp, vp); 473 cache_unlock(&mp->mnt_ncmountpt); /* leave ref intact */ 474 } 475 p = curproc; 476 p->p_fd->fd_cdir = vp; 477 vref(p->p_fd->fd_cdir); 478 p->p_fd->fd_rdir = vp; 479 vref(p->p_fd->fd_rdir); 480 vfs_cache_setroot(vp, cache_hold(&mp->mnt_ncmountpt)); 481 vn_unlock(vp); /* leave ref intact */ 482 cache_copy(&mp->mnt_ncmountpt, &p->p_fd->fd_ncdir); 483 cache_copy(&mp->mnt_ncmountpt, &p->p_fd->fd_nrdir); 484 485 vfs_unbusy(mp); 486 if (mp->mnt_syncer == NULL) { 487 error = vfs_allocate_syncvnode(mp); 488 if (error) 489 kprintf("Warning: no syncer vp for root!\n"); 490 error = 0; 491 } 492 VFS_START( mp, 0 ); 493 } else { 494 if (mp != NULL) { 495 vn_syncer_thr_stop(mp); 496 vfs_unbusy(mp); 497 kfree(mp, M_MOUNT); 498 } 499 kprintf("Root mount failed: %d\n", error); 500 } 501 return(error); 502 } 503 504 505 static void 506 vfs_mountroot_ask_callback(char *name, cdev_t dev, bool is_alias, 507 void *arg __unused) 508 { 509 if (!is_alias && dev_is_good(dev) && (dev_dflags(dev) & D_DISK)) 510 kprintf(" \"%s\" ", name); 511 } 512 513 514 /* 515 * Spin prompting on the console for a suitable root filesystem 516 */ 517 static int 518 vfs_mountroot_ask(void) 519 { 520 char name[128]; 521 int llimit = 100; 522 523 kprintf("\nManual root filesystem specification:\n"); 524 kprintf(" <fstype>:<device> Specify root (e.g. ufs:da0s1a)\n"); 525 kprintf(" ? List valid disk boot devices\n"); 526 kprintf(" panic Just panic\n"); 527 kprintf(" abort Abort manual input\n"); 528 while (llimit--) { 529 kprintf("\nmountroot> "); 530 531 if (get_line(name, 128) < 0) 532 break; 533 if (name[0] == 0) { 534 ; 535 } else if (name[0] == '?') { 536 kprintf("Possibly valid devices for root FS:\n"); 537 //enumerate all disk devices 538 devfs_scan_callback(vfs_mountroot_ask_callback, NULL); 539 kprintf("\n"); 540 continue; 541 } else if (strcmp(name, "panic") == 0) { 542 panic("panic from console"); 543 } else if (strcmp(name, "abort") == 0) { 544 break; 545 } else if (vfs_mountroot_try(name) == 0) { 546 return(0); 547 } 548 } 549 return(1); 550 } 551 552 553 static int 554 get_line(char *cp, int limit) 555 { 556 char *lp; 557 int dummy; 558 int c; 559 560 lp = cp; 561 cnpoll(TRUE); 562 for (;;) { 563 c = cncheckc(); 564 565 switch (c) { 566 case NOKEY: 567 tsleep(&dummy, 0, "cnpoll", hz / 25); 568 break; 569 case -1: 570 goto done; 571 case '\n': 572 case '\r': 573 kprintf("\n"); 574 *lp++ = '\0'; 575 c = 0; 576 goto done; 577 case '\b': 578 case '\177': 579 if (lp > cp) { 580 kprintf("\b \b"); 581 lp--; 582 } else { 583 kprintf("%c", 7); 584 } 585 continue; 586 case '#': 587 kprintf("#"); 588 lp--; 589 if (lp < cp) 590 lp = cp; 591 continue; 592 case 'u' & 037: 593 /* NOTE: '@' no longer processed here, used for H2 */ 594 lp = cp; 595 kprintf("%c", '\n'); 596 continue; 597 default: 598 if (lp - cp >= limit - 1) { 599 kprintf("%c", 7); 600 } else { 601 kprintf("%c", c); 602 *lp++ = c; 603 } 604 continue; 605 } 606 } 607 done: 608 cnpoll(FALSE); 609 return c; 610 } 611 612 /* 613 * Convert a given name to the cdev_t of the disk-like device 614 * it refers to. 615 */ 616 cdev_t 617 kgetdiskbyname(const char *name) 618 { 619 cdev_t rdev; 620 621 /* 622 * Get the base name of the device 623 */ 624 if (strncmp(name, __SYS_PATH_DEV, sizeof(__SYS_PATH_DEV) - 1) == 0) 625 name += sizeof(__SYS_PATH_DEV) - 1; 626 627 /* 628 * Locate the device 629 */ 630 rdev = devfs_find_device_by_name("%s", name); 631 if (rdev == NULL) { 632 kprintf("no disk named '%s'\n", name); 633 } 634 /* 635 * FOUND DEVICE 636 */ 637 return(rdev); 638 } 639 640 /* 641 * Set rootdev to match (name), given that we expect it to 642 * refer to a disk-like device. 643 */ 644 static int 645 setrootbyname(char *name) 646 { 647 cdev_t diskdev; 648 649 diskdev = kgetdiskbyname(name); 650 if (diskdev != NULL) { 651 rootdev = diskdev; 652 return (0); 653 } 654 /* set to NULL if kgetdiskbyname() fails so that if the first rootdev is 655 * found by fails to mount and the second one isn't found, mountroot_try 656 * doesn't try again with the first one 657 */ 658 rootdev = NULL; 659 return (1); 660 } 661 662 #ifdef DDB 663 DB_SHOW_COMMAND(disk, db_getdiskbyname) 664 { 665 cdev_t dev; 666 667 if (modif[0] == '\0') { 668 db_error("usage: show disk/devicename"); 669 return; 670 } 671 dev = kgetdiskbyname(modif); 672 if (dev != NULL) 673 db_printf("cdev_t = %p\n", dev); 674 else 675 db_printf("No disk device matched.\n"); 676 } 677 #endif 678 679 static int 680 vfs_sysctl_real_root(SYSCTL_HANDLER_ARGS) 681 { 682 char *real_root; 683 size_t len; 684 int error; 685 686 real_root = kgetenv("vfs.root.realroot"); 687 688 if (real_root == NULL) 689 real_root = ""; 690 691 len = strlen(real_root) + 1; 692 693 error = sysctl_handle_string(oidp, real_root, len, req); 694 695 return error; 696 } 697 698 SYSCTL_PROC(_vfs, OID_AUTO, real_root, 699 CTLTYPE_STRING | CTLFLAG_RD, 0, 0, vfs_sysctl_real_root, 700 "A", "Real root mount string"); 701