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 */ 424 if ((strcmp(vfsname, "hammer") != 0) && (devname[0] != 0) && 425 setrootbyname(devname)) 426 kprintf("setrootbyname failed\n"); 427 428 /* If the root device is a type "memory disk", mount RW */ 429 if (rootdev != NULL && dev_is_good(rootdev) && 430 (dev_dflags(rootdev) & D_MEMDISK)) { 431 mp->mnt_flag &= ~MNT_RDONLY; 432 } 433 434 error = VFS_MOUNT(mp, NULL, NULL, proc0.p_ucred); 435 436 if (!error) 437 break; 438 end: 439 if(*ep == 0) 440 break; 441 cp = ep + 1; 442 } 443 444 if (vfsname != NULL) 445 kfree(vfsname, M_MOUNT); 446 if (devname != NULL) 447 kfree(devname, M_MOUNT); 448 if (mf != NULL) 449 kfree(mf, M_MOUNT); 450 if (error == 0) { 451 /* register with list of mounted filesystems */ 452 mountlist_insert(mp, MNTINS_FIRST); 453 454 /* sanity check system clock against root fs timestamp */ 455 inittodr(mp->mnt_time); 456 457 /* Get the vnode for '/'. Set p->p_fd->fd_cdir to reference it. */ 458 mp = mountlist_boot_getfirst(); 459 if (VFS_ROOT(mp, &vp)) 460 panic("cannot find root vnode"); 461 if (mp->mnt_ncmountpt.ncp == NULL) { 462 cache_allocroot(&mp->mnt_ncmountpt, mp, vp); 463 cache_unlock(&mp->mnt_ncmountpt); /* leave ref intact */ 464 } 465 p = curproc; 466 p->p_fd->fd_cdir = vp; 467 vref(p->p_fd->fd_cdir); 468 p->p_fd->fd_rdir = vp; 469 vref(p->p_fd->fd_rdir); 470 vfs_cache_setroot(vp, cache_hold(&mp->mnt_ncmountpt)); 471 vn_unlock(vp); /* leave ref intact */ 472 cache_copy(&mp->mnt_ncmountpt, &p->p_fd->fd_ncdir); 473 cache_copy(&mp->mnt_ncmountpt, &p->p_fd->fd_nrdir); 474 475 vfs_unbusy(mp); 476 if (mp->mnt_syncer == NULL) { 477 error = vfs_allocate_syncvnode(mp); 478 if (error) 479 kprintf("Warning: no syncer vp for root!\n"); 480 error = 0; 481 } 482 VFS_START( mp, 0 ); 483 } else { 484 if (mp != NULL) { 485 vn_syncer_thr_stop(mp); 486 vfs_unbusy(mp); 487 kfree(mp, M_MOUNT); 488 } 489 kprintf("Root mount failed: %d\n", error); 490 } 491 return(error); 492 } 493 494 495 static void 496 vfs_mountroot_ask_callback(char *name, cdev_t dev, bool is_alias, 497 void *arg __unused) 498 { 499 if (!is_alias && dev_is_good(dev) && (dev_dflags(dev) & D_DISK)) 500 kprintf(" \"%s\" ", name); 501 } 502 503 504 /* 505 * Spin prompting on the console for a suitable root filesystem 506 */ 507 static int 508 vfs_mountroot_ask(void) 509 { 510 char name[128]; 511 int llimit = 100; 512 513 kprintf("\nManual root filesystem specification:\n"); 514 kprintf(" <fstype>:<device> Specify root (e.g. ufs:da0s1a)\n"); 515 kprintf(" ? List valid disk boot devices\n"); 516 kprintf(" panic Just panic\n"); 517 kprintf(" abort Abort manual input\n"); 518 while (llimit--) { 519 kprintf("\nmountroot> "); 520 521 if (getline(name, 128) < 0) 522 break; 523 if (name[0] == 0) { 524 ; 525 } else if (name[0] == '?') { 526 kprintf("Possibly valid devices for root FS:\n"); 527 //enumerate all disk devices 528 devfs_scan_callback(vfs_mountroot_ask_callback, NULL); 529 kprintf("\n"); 530 continue; 531 } else if (strcmp(name, "panic") == 0) { 532 panic("panic from console"); 533 } else if (strcmp(name, "abort") == 0) { 534 break; 535 } else if (vfs_mountroot_try(name) == 0) { 536 return(0); 537 } 538 } 539 return(1); 540 } 541 542 543 static int 544 getline(char *cp, int limit) 545 { 546 char *lp; 547 int dummy; 548 int c; 549 550 lp = cp; 551 cnpoll(TRUE); 552 for (;;) { 553 c = cncheckc(); 554 555 switch (c) { 556 case NOKEY: 557 tsleep(&dummy, 0, "cnpoll", hz / 25); 558 break; 559 case -1: 560 goto done; 561 case '\n': 562 case '\r': 563 kprintf("\n"); 564 *lp++ = '\0'; 565 c = 0; 566 goto done; 567 case '\b': 568 case '\177': 569 if (lp > cp) { 570 kprintf("\b \b"); 571 lp--; 572 } else { 573 kprintf("%c", 7); 574 } 575 continue; 576 case '#': 577 kprintf("#"); 578 lp--; 579 if (lp < cp) 580 lp = cp; 581 continue; 582 case '@': 583 case 'u' & 037: 584 lp = cp; 585 kprintf("%c", '\n'); 586 continue; 587 default: 588 if (lp - cp >= limit - 1) { 589 kprintf("%c", 7); 590 } else { 591 kprintf("%c", c); 592 *lp++ = c; 593 } 594 continue; 595 } 596 } 597 done: 598 cnpoll(FALSE); 599 return c; 600 } 601 602 /* 603 * Convert a given name to the cdev_t of the disk-like device 604 * it refers to. 605 */ 606 cdev_t 607 kgetdiskbyname(const char *name) 608 { 609 cdev_t rdev; 610 611 /* 612 * Get the base name of the device 613 */ 614 if (strncmp(name, __SYS_PATH_DEV, sizeof(__SYS_PATH_DEV) - 1) == 0) 615 name += sizeof(__SYS_PATH_DEV) - 1; 616 617 /* 618 * Locate the device 619 */ 620 rdev = devfs_find_device_by_name("%s", name); 621 if (rdev == NULL) { 622 kprintf("no disk named '%s'\n", name); 623 } 624 /* 625 * FOUND DEVICE 626 */ 627 return(rdev); 628 } 629 630 /* 631 * Set rootdev to match (name), given that we expect it to 632 * refer to a disk-like device. 633 */ 634 static int 635 setrootbyname(char *name) 636 { 637 cdev_t diskdev; 638 639 diskdev = kgetdiskbyname(name); 640 if (diskdev != NULL) { 641 rootdev = diskdev; 642 return (0); 643 } 644 /* set to NULL if kgetdiskbyname() fails so that if the first rootdev is 645 * found by fails to mount and the second one isn't found, mountroot_try 646 * doesn't try again with the first one 647 */ 648 rootdev = NULL; 649 return (1); 650 } 651 652 #ifdef DDB 653 DB_SHOW_COMMAND(disk, db_getdiskbyname) 654 { 655 cdev_t dev; 656 657 if (modif[0] == '\0') { 658 db_error("usage: show disk/devicename"); 659 return; 660 } 661 dev = kgetdiskbyname(modif); 662 if (dev != NULL) 663 db_printf("cdev_t = %p\n", dev); 664 else 665 db_printf("No disk device matched.\n"); 666 } 667 #endif 668 669 static int 670 vfs_sysctl_real_root(SYSCTL_HANDLER_ARGS) 671 { 672 char *real_root; 673 size_t len; 674 int error; 675 676 real_root = kgetenv("vfs.root.realroot"); 677 678 if (real_root == NULL) 679 real_root = ""; 680 681 len = strlen(real_root) + 1; 682 683 error = sysctl_handle_string(oidp, real_root, len, req); 684 685 return error; 686 } 687 688 SYSCTL_PROC(_vfs, OID_AUTO, real_root, 689 CTLTYPE_STRING | CTLFLAG_RD, 0, 0, vfs_sysctl_real_root, 690 "A", "Real root mount string"); 691