/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 2010 Marcel Moolenaar
 * Copyright (c) 1999-2004 Poul-Henning Kamp
 * Copyright (c) 1999 Michael Smith
 * Copyright (c) 1989, 1993
 *      The Regents of the University of California.  All rights reserved.
 * (c) UNIX System Laboratories, Inc.
 * All or some portions of this file are derived from material licensed
 * to the University of California by American Telephone and Telegraph
 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
 * the permission of UNIX System Laboratories, Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include "opt_rootdevname.h"

#include <sys/param.h>
#include <sys/conf.h>
#include <sys/cons.h>
#include <sys/eventhandler.h>
#include <sys/fcntl.h>
#include <sys/jail.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/mdioctl.h>
#include <sys/mount.h>
#include <sys/mutex.h>
#include <sys/namei.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/filedesc.h>
#include <sys/reboot.h>
#include <sys/sbuf.h>
#include <sys/stat.h>
#include <sys/syscallsubr.h>
#include <sys/sysproto.h>
#include <sys/sx.h>
#include <sys/sysctl.h>
#include <sys/systm.h>
#include <sys/vnode.h>

#include <geom/geom.h>

/*
 * The root filesystem is detailed in the kernel environment variable
 * vfs.root.mountfrom, which is expected to be in the general format
 *
 * <vfsname>:[<path>][  <vfsname>:[<path>] ...]
 * vfsname   := the name of a VFS known to the kernel and capable
 *              of being mounted as root
 * path      := disk device name or other data used by the filesystem
 *              to locate its physical store
 *
 * If the environment variable vfs.root.mountfrom is a space separated list,
 * each list element is tried in turn and the root filesystem will be mounted
 * from the first one that succeeds.
 *
 * The environment variable vfs.root.mountfrom.options is a comma delimited
 * set of string mount options.  These mount options must be parseable
 * by nmount() in the kernel.
 */

static int parse_mount(char **);
static struct mntarg *parse_mountroot_options(struct mntarg *, const char *);
static int sysctl_vfs_root_mount_hold(SYSCTL_HANDLER_ARGS);
static void vfs_mountroot_wait(void);
static int vfs_mountroot_wait_if_neccessary(const char *fs, const char *dev);

/*
 * The vnode of the system's root (/ in the filesystem, without chroot
 * active.)
 */
struct vnode *rootvnode;

/*
 * Mount of the system's /dev.
 */
struct mount *rootdevmp;

char *rootdevnames[2] = {NULL, NULL};

struct mtx root_holds_mtx;
MTX_SYSINIT(root_holds, &root_holds_mtx, "root_holds", MTX_DEF);

static TAILQ_HEAD(, root_hold_token)    root_holds =
    TAILQ_HEAD_INITIALIZER(root_holds);

enum action {
        A_CONTINUE,
        A_PANIC,
        A_REBOOT,
        A_RETRY
};

enum rh_flags {
        RH_FREE,
        RH_ALLOC,
        RH_ARG,
};

static enum action root_mount_onfail = A_CONTINUE;

static int root_mount_mddev;
static int root_mount_complete;

/* By default wait up to 3 seconds for devices to appear. */
static int root_mount_timeout = 3;
TUNABLE_INT("vfs.mountroot.timeout", &root_mount_timeout);

static int root_mount_always_wait = 0;
SYSCTL_INT(_vfs, OID_AUTO, root_mount_always_wait, CTLFLAG_RDTUN,
    &root_mount_always_wait, 0,
    "Wait for root mount holds even if the root device already exists");

SYSCTL_PROC(_vfs, OID_AUTO, root_mount_hold,
    CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE,
    NULL, 0, sysctl_vfs_root_mount_hold, "A",
    "List of root mount hold tokens");

static int
sysctl_vfs_root_mount_hold(SYSCTL_HANDLER_ARGS)
{
        struct sbuf sb;
        struct root_hold_token *h;
        int error;

        sbuf_new(&sb, NULL, 256, SBUF_AUTOEXTEND | SBUF_INCLUDENUL);

        mtx_lock(&root_holds_mtx);
        TAILQ_FOREACH(h, &root_holds, list) {
                if (h != TAILQ_FIRST(&root_holds))
                        sbuf_putc(&sb, ' ');
                sbuf_printf(&sb, "%s", h->who);
        }
        mtx_unlock(&root_holds_mtx);

        error = sbuf_finish(&sb);
        if (error == 0)
                error = SYSCTL_OUT(req, sbuf_data(&sb), sbuf_len(&sb));
        sbuf_delete(&sb);
        return (error);
}

struct root_hold_token *
root_mount_hold(const char *identifier)
{
        struct root_hold_token *h;

        h = malloc(sizeof *h, M_DEVBUF, M_ZERO | M_WAITOK);
        h->flags = RH_ALLOC;
        h->who = identifier;
        mtx_lock(&root_holds_mtx);
        TSHOLD("root mount");
        TAILQ_INSERT_TAIL(&root_holds, h, list);
        mtx_unlock(&root_holds_mtx);
        return (h);
}

void
root_mount_hold_token(const char *identifier, struct root_hold_token *h)
{
#ifdef INVARIANTS
        struct root_hold_token *t;
#endif

        h->flags = RH_ARG;
        h->who = identifier;
        mtx_lock(&root_holds_mtx);
#ifdef INVARIANTS
        TAILQ_FOREACH(t, &root_holds, list) {
                if (t == h) {
                        panic("Duplicate mount hold by '%s' on %p",
                            identifier, h);
                }
        }
#endif
        TSHOLD("root mount");
        TAILQ_INSERT_TAIL(&root_holds, h, list);
        mtx_unlock(&root_holds_mtx);
}

void
root_mount_rel(struct root_hold_token *h)
{

        if (h == NULL || h->flags == RH_FREE)
                return;

        mtx_lock(&root_holds_mtx);
        TAILQ_REMOVE(&root_holds, h, list);
        TSRELEASE("root mount");
        wakeup(&root_holds);
        mtx_unlock(&root_holds_mtx);
        if (h->flags == RH_ALLOC) {
                free(h, M_DEVBUF);
        } else
                h->flags = RH_FREE;
}

int
root_mounted(void)
{

        /* No mutex is acquired here because int stores are atomic. */
        return (root_mount_complete);
}

static void
set_rootvnode(void)
{

        if (VFS_ROOT(TAILQ_FIRST(&mountlist), LK_EXCLUSIVE, &rootvnode))
                panic("set_rootvnode: Cannot find root vnode");

        VOP_UNLOCK(rootvnode);

        pwd_set_rootvnode();
}

static int
vfs_mountroot_devfs(struct thread *td, struct mount **mpp)
{
        struct vfsoptlist *opts;
        struct vfsconf *vfsp;
        struct mount *mp;
        int error;

        *mpp = NULL;

        if (rootdevmp != NULL) {
                /*
                 * Already have /dev; this happens during rerooting.
                 */
                error = vfs_busy(rootdevmp, 0);
                if (error != 0)
                        return (error);
                *mpp = rootdevmp;
        } else {
                vfsp = vfs_byname("devfs");
                KASSERT(vfsp != NULL, ("Could not find devfs by name"));
                if (vfsp == NULL)
                        return (ENOENT);

                mp = vfs_mount_alloc(NULL, vfsp, "/dev", td->td_ucred);

                error = VFS_MOUNT(mp);
                KASSERT(error == 0, ("VFS_MOUNT(devfs) failed %d", error));
                if (error)
                        return (error);

                error = VFS_STATFS(mp, &mp->mnt_stat);
                KASSERT(error == 0, ("VFS_STATFS(devfs) failed %d", error));
                if (error)
                        return (error);

                opts = malloc(sizeof(struct vfsoptlist), M_MOUNT, M_WAITOK);
                TAILQ_INIT(opts);
                mp->mnt_opt = opts;

                mtx_lock(&mountlist_mtx);
                TAILQ_INSERT_HEAD(&mountlist, mp, mnt_list);
                mtx_unlock(&mountlist_mtx);

                *mpp = mp;
                rootdevmp = mp;
                vfs_op_exit(mp);
        }

        set_rootvnode();

        error = kern_symlinkat(td, "/", AT_FDCWD, "dev", UIO_SYSSPACE);
        if (error)
                printf("kern_symlink /dev -> / returns %d\n", error);

        return (error);
}

static void
vfs_mountroot_shuffle(struct thread *td, struct mount *mpdevfs)
{
        struct nameidata nd;
        struct mount *mporoot, *mpnroot;
        struct vnode *vp, *vporoot, *vpdevfs;
        char *fspath;
        int error;

        mpnroot = TAILQ_NEXT(mpdevfs, mnt_list);

        /* Shuffle the mountlist. */
        mtx_lock(&mountlist_mtx);
        mporoot = TAILQ_FIRST(&mountlist);
        TAILQ_REMOVE(&mountlist, mpdevfs, mnt_list);
        if (mporoot != mpdevfs) {
                TAILQ_REMOVE(&mountlist, mpnroot, mnt_list);
                TAILQ_INSERT_HEAD(&mountlist, mpnroot, mnt_list);
        }
        TAILQ_INSERT_TAIL(&mountlist, mpdevfs, mnt_list);
        mtx_unlock(&mountlist_mtx);

        cache_purgevfs(mporoot);
        if (mporoot != mpdevfs)
                cache_purgevfs(mpdevfs);

        if (VFS_ROOT(mporoot, LK_EXCLUSIVE, &vporoot))
                panic("vfs_mountroot_shuffle: Cannot find root vnode");

        VI_LOCK(vporoot);
        vporoot->v_iflag &= ~VI_MOUNT;
        vn_irflag_unset_locked(vporoot, VIRF_MOUNTPOINT);
        vporoot->v_mountedhere = NULL;
        VI_UNLOCK(vporoot);
        mporoot->mnt_flag &= ~MNT_ROOTFS;
        mporoot->mnt_vnodecovered = NULL;
        vput(vporoot);

        /* Set up the new rootvnode, and purge the cache */
        mpnroot->mnt_vnodecovered = NULL;
        set_rootvnode();
        cache_purgevfs(rootvnode->v_mount);

        if (mporoot != mpdevfs) {
                /* Remount old root under /.mount or /mnt */
                fspath = "/.mount";
                NDINIT(&nd, LOOKUP, FOLLOW | LOCKLEAF, UIO_SYSSPACE, fspath);
                error = namei(&nd);
                if (error) {
                        fspath = "/mnt";
                        NDINIT(&nd, LOOKUP, FOLLOW | LOCKLEAF, UIO_SYSSPACE,
                            fspath);
                        error = namei(&nd);
                }
                if (!error) {
                        NDFREE_PNBUF(&nd);
                        vp = nd.ni_vp;
                        error = (vp->v_type == VDIR) ? 0 : ENOTDIR;
                        if (!error)
                                error = vinvalbuf(vp, V_SAVE, 0, 0);
                        if (!error) {
                                cache_purge(vp);
                                VI_LOCK(vp);
                                mporoot->mnt_vnodecovered = vp;
                                vn_irflag_set_locked(vp, VIRF_MOUNTPOINT);
                                vp->v_mountedhere = mporoot;
                                strlcpy(mporoot->mnt_stat.f_mntonname,
                                    fspath, MNAMELEN);
                                VI_UNLOCK(vp);
                                VOP_UNLOCK(vp);
                        } else
                                vput(vp);
                }

                if (error)
                        printf("mountroot: unable to remount previous root "
                            "under /.mount or /mnt (error %d)\n", error);
        }

        /* Remount devfs under /dev */
        NDINIT(&nd, LOOKUP, FOLLOW | LOCKLEAF, UIO_SYSSPACE, "/dev");
        error = namei(&nd);
        if (!error) {
                NDFREE_PNBUF(&nd);
                vp = nd.ni_vp;
                error = (vp->v_type == VDIR) ? 0 : ENOTDIR;
                if (!error)
                        error = vinvalbuf(vp, V_SAVE, 0, 0);
                if (!error) {
                        vpdevfs = mpdevfs->mnt_vnodecovered;
                        if (vpdevfs != NULL) {
                                cache_purge(vpdevfs);
                                VI_LOCK(vpdevfs);
                                vn_irflag_unset_locked(vpdevfs, VIRF_MOUNTPOINT);
                                vpdevfs->v_mountedhere = NULL;
                                VI_UNLOCK(vpdevfs);
                                vrele(vpdevfs);
                        }
                        VI_LOCK(vp);
                        mpdevfs->mnt_vnodecovered = vp;
                        vn_irflag_set_locked(vp, VIRF_MOUNTPOINT);
                        vp->v_mountedhere = mpdevfs;
                        VI_UNLOCK(vp);
                        VOP_UNLOCK(vp);
                } else
                        vput(vp);
        }
        if (error)
                printf("mountroot: unable to remount devfs under /dev "
                    "(error %d)\n", error);

        if (mporoot == mpdevfs) {
                vfs_unbusy(mpdevfs);
                /* Unlink the no longer needed /dev/dev -> / symlink */
                error = kern_funlinkat(td, AT_FDCWD, "/dev/dev", FD_NONE,
                    UIO_SYSSPACE, 0, 0);
                if (error)
                        printf("mountroot: unable to unlink /dev/dev "
                            "(error %d)\n", error);
        }
}

/*
 * Configuration parser.
 */

/* Parser character classes. */
#define CC_WHITESPACE           -1
#define CC_NONWHITESPACE        -2

/* Parse errors. */
#define PE_EOF                  -1
#define PE_EOL                  -2

static __inline int
parse_peek(char **conf)
{

        return (**conf);
}

static __inline void
parse_poke(char **conf, int c)
{

        **conf = c;
}

static __inline void
parse_advance(char **conf)
{

        (*conf)++;
}

static int
parse_skipto(char **conf, int mc)
{
        int c, match;

        while (1) {
                c = parse_peek(conf);
                if (c == 0)
                        return (PE_EOF);
                switch (mc) {
                case CC_WHITESPACE:
                        match = (c == ' ' || c == '\t' || c == '\n') ? 1 : 0;
                        break;
                case CC_NONWHITESPACE:
                        if (c == '\n')
                                return (PE_EOL);
                        match = (c != ' ' && c != '\t') ? 1 : 0;
                        break;
                default:
                        match = (c == mc) ? 1 : 0;
                        break;
                }
                if (match)
                        break;
                parse_advance(conf);
        }
        return (0);
}

static int
parse_token(char **conf, char **tok)
{
        char *p;
        size_t len;
        int error;

        *tok = NULL;
        error = parse_skipto(conf, CC_NONWHITESPACE);
        if (error)
                return (error);
        p = *conf;
        error = parse_skipto(conf, CC_WHITESPACE);
        len = *conf - p;
        *tok = malloc(len + 1, M_TEMP, M_WAITOK | M_ZERO);
        bcopy(p, *tok, len);
        return (0);
}

static void
parse_dir_ask_printenv(const char *var)
{
        char *val;

        val = kern_getenv(var);
        if (val != NULL) {
                printf("  %s=%s\n", var, val);
                freeenv(val);
        }
}

static int
parse_dir_ask(char **conf)
{
        char name[80];
        char *mnt;
        int error;

        vfs_mountroot_wait();

        printf("\nLoader variables:\n");
        parse_dir_ask_printenv("vfs.root.mountfrom");
        parse_dir_ask_printenv("vfs.root.mountfrom.options");

        printf("\nManual root filesystem specification:\n");
        printf("  <fstype>:<device> [options]\n");
        printf("      Mount <device> using filesystem <fstype>\n");
        printf("      and with the specified (optional) option list.\n");
        printf("\n");
        printf("    eg. ufs:/dev/da0s1a\n");
        printf("        zfs:zroot/ROOT/default\n");
        printf("        cd9660:/dev/cd0 ro\n");
        printf("          (which is equivalent to: ");
        printf("mount -t cd9660 -o ro /dev/cd0 /)\n");
        printf("\n");
        printf("  ?               List valid disk boot devices\n");
        printf("  .               Yield 1 second (for background tasks)\n");
        printf("  <empty line>    Abort manual input\n");

        do {
                error = EINVAL;
                printf("\nmountroot> ");
                cngets(name, sizeof(name), GETS_ECHO);
                if (name[0] == '\0')
                        break;
                if (name[0] == '?' && name[1] == '\0') {
                        printf("\nList of GEOM managed disk devices:\n  ");
                        g_dev_print();
                        continue;
                }
                if (name[0] == '.' && name[1] == '\0') {
                        pause("rmask", hz);
                        continue;
                }
                mnt = name;
                error = parse_mount(&mnt);
                if (error == -1)
                        printf("Invalid file system specification.\n");
        } while (error != 0);

        return (error);
}

static int
parse_dir_md(char **conf)
{
        struct stat sb;
        struct thread *td;
        struct md_ioctl *mdio;
        char *path, *tok;
        int error, fd, len;

        td = curthread;
        fd = -1;

        error = parse_token(conf, &tok);
        if (error)
                return (error);

        len = strlen(tok);
        mdio = malloc(sizeof(*mdio) + len + 1, M_TEMP, M_WAITOK | M_ZERO);
        path = (void *)(mdio + 1);
        bcopy(tok, path, len);
        free(tok, M_TEMP);

        /* Get file status. */
        error = kern_statat(td, 0, AT_FDCWD, path, UIO_SYSSPACE, &sb);
        if (error)
                goto out;

        /* Open /dev/mdctl so that we can attach/detach. */
        error = kern_openat(td, AT_FDCWD, "/dev/" MDCTL_NAME, UIO_SYSSPACE,
            O_RDWR, 0);
        if (error)
                goto out;

        fd = td->td_retval[0];
        mdio->md_version = MDIOVERSION;
        mdio->md_type = MD_VNODE;

        if (root_mount_mddev != -1) {
                mdio->md_unit = root_mount_mddev;
                (void)kern_ioctl(td, fd, MDIOCDETACH, (void *)mdio);
                /* Ignore errors. We don't care. */
                root_mount_mddev = -1;
        }

        mdio->md_file = (void *)(mdio + 1);
        mdio->md_options = MD_AUTOUNIT | MD_READONLY;
        mdio->md_mediasize = sb.st_size;
        mdio->md_unit = 0;
        error = kern_ioctl(td, fd, MDIOCATTACH, (void *)mdio);
        if (error)
                goto out;

        if (mdio->md_unit > 9) {
                printf("rootmount: too many md units\n");
                mdio->md_file = NULL;
                mdio->md_options = 0;
                mdio->md_mediasize = 0;
                error = kern_ioctl(td, fd, MDIOCDETACH, (void *)mdio);
                /* Ignore errors. We don't care. */
                error = ERANGE;
                goto out;
        }

        root_mount_mddev = mdio->md_unit;
        printf(MD_NAME "%u attached to %s\n", root_mount_mddev, mdio->md_file);

 out:
        if (fd >= 0)
                (void)kern_close(td, fd);
        free(mdio, M_TEMP);
        return (error);
}

static int
parse_dir_onfail(char **conf)
{
        char *action;
        int error;

        error = parse_token(conf, &action);
        if (error)
                return (error);

        if (!strcmp(action, "continue"))
                root_mount_onfail = A_CONTINUE;
        else if (!strcmp(action, "panic"))
                root_mount_onfail = A_PANIC;
        else if (!strcmp(action, "reboot"))
                root_mount_onfail = A_REBOOT;
        else if (!strcmp(action, "retry"))
                root_mount_onfail = A_RETRY;
        else {
                printf("rootmount: %s: unknown action\n", action);
                error = EINVAL;
        }

        free(action, M_TEMP);
        return (0);
}

static int
parse_dir_timeout(char **conf)
{
        char *tok, *endtok;
        long secs;
        int error;

        error = parse_token(conf, &tok);
        if (error)
                return (error);

        secs = strtol(tok, &endtok, 0);
        error = (secs < 0 || *endtok != '\0') ? EINVAL : 0;
        if (!error)
                root_mount_timeout = secs;
        free(tok, M_TEMP);
        return (error);
}

static int
parse_directive(char **conf)
{
        char *dir;
        int error;

        error = parse_token(conf, &dir);
        if (error)
                return (error);

        if (strcmp(dir, ".ask") == 0)
                error = parse_dir_ask(conf);
        else if (strcmp(dir, ".md") == 0)
                error = parse_dir_md(conf);
        else if (strcmp(dir, ".onfail") == 0)
                error = parse_dir_onfail(conf);
        else if (strcmp(dir, ".timeout") == 0)
                error = parse_dir_timeout(conf);
        else {
                printf("mountroot: invalid directive `%s'\n", dir);
                /* Ignore the rest of the line. */
                (void)parse_skipto(conf, '\n');
                error = EINVAL;
        }
        free(dir, M_TEMP);
        return (error);
}

static bool
parse_mount_dev_present(const char *dev)
{
        struct nameidata nd;
        int error;

        NDINIT(&nd, LOOKUP, FOLLOW, UIO_SYSSPACE, dev);
        error = namei(&nd);
        if (error != 0)
                return (false);
        vrele(nd.ni_vp);
        NDFREE_PNBUF(&nd);
        return (true);
}

#define ERRMSGL 255
static int
parse_mount(char **conf)
{
        char *errmsg;
        struct mntarg *ma;
        char *dev, *fs, *opts, *tok;
        int delay, error, timeout;

        error = parse_token(conf, &tok);
        if (error)
                return (error);
        fs = tok;
        error = parse_skipto(&tok, ':');
        if (error) {
                free(fs, M_TEMP);
                return (error);
        }
        parse_poke(&tok, '\0');
        parse_advance(&tok);
        dev = tok;

        if (root_mount_mddev != -1) {
                /* Handle substitution for the md unit number. */
                tok = strstr(dev, "md#");
                if (tok != NULL)
                        tok[2] = '0' + root_mount_mddev;
        }

        /* Parse options. */
        error = parse_token(conf, &tok);
        opts = (error == 0) ? tok : NULL;

        printf("Trying to mount root from %s:%s [%s]...\n", fs, dev,
            (opts != NULL) ? opts : "");

        errmsg = malloc(ERRMSGL, M_TEMP, M_WAITOK | M_ZERO);

        if (vfs_byname(fs) == NULL) {
                strlcpy(errmsg, "unknown file system", ERRMSGL);
                error = ENOENT;
                goto out;
        }

        error = vfs_mountroot_wait_if_neccessary(fs, dev);
        if (error != 0)
                goto out;

        delay = hz / 10;
        timeout = root_mount_timeout * hz;

        for (;;) {
                ma = NULL;
                ma = mount_arg(ma, "fstype", fs, -1);
                ma = mount_arg(ma, "fspath", "/", -1);
                ma = mount_arg(ma, "from", dev, -1);
                ma = mount_arg(ma, "errmsg", errmsg, ERRMSGL);
                ma = mount_arg(ma, "ro", NULL, 0);
                ma = parse_mountroot_options(ma, opts);

                error = kernel_mount(ma, MNT_ROOTFS);
                if (error == 0 || error == EILSEQ || timeout <= 0)
                        break;

                if (root_mount_timeout * hz == timeout ||
                    (bootverbose && timeout % hz == 0)) {
                        printf("Mounting from %s:%s failed with error %d; "
                            "retrying for %d more second%s\n", fs, dev, error,
                            timeout / hz, (timeout / hz > 1) ? "s" : "");
                }
                pause("rmretry", delay);
                timeout -= delay;
        }
 out:
        if (error) {
                printf("Mounting from %s:%s failed with error %d",
                    fs, dev, error);
                if (errmsg[0] != '\0')
                        printf(": %s", errmsg);
                printf(".\n");
        }
        free(fs, M_TEMP);
        free(errmsg, M_TEMP);
        if (opts != NULL)
                free(opts, M_TEMP);
        /* kernel_mount can return -1 on error. */
        return ((error < 0) ? EDOOFUS : error);
}
#undef ERRMSGL

static int
vfs_mountroot_parse(struct sbuf *sb, struct mount *mpdevfs)
{
        struct mount *mp;
        char *conf;
        int error;

        root_mount_mddev = -1;

retry:
        conf = sbuf_data(sb);
        mp = TAILQ_NEXT(mpdevfs, mnt_list);
        error = (mp == NULL) ? 0 : EDOOFUS;
        root_mount_onfail = A_CONTINUE;
        while (mp == NULL) {
                error = parse_skipto(&conf, CC_NONWHITESPACE);
                if (error == PE_EOL) {
                        parse_advance(&conf);
                        continue;
                }
                if (error < 0)
                        break;
                switch (parse_peek(&conf)) {
                case '#':
                        error = parse_skipto(&conf, '\n');
                        break;
                case '.':
                        error = parse_directive(&conf);
                        break;
                default:
                        error = parse_mount(&conf);
                        if (error == -1) {
                                printf("mountroot: invalid file system "
                                    "specification.\n");
                                error = 0;
                        }
                        break;
                }
                if (error < 0)
                        break;
                /* Ignore any trailing garbage on the line. */
                if (parse_peek(&conf) != '\n') {
                        printf("mountroot: advancing to next directive...\n");
                        (void)parse_skipto(&conf, '\n');
                }
                mp = TAILQ_NEXT(mpdevfs, mnt_list);
        }
        if (mp != NULL)
                return (0);

        /*
         * We failed to mount (a new) root.
         */
        switch (root_mount_onfail) {
        case A_CONTINUE:
                break;
        case A_PANIC:
                panic("mountroot: unable to (re-)mount root.");
                /* NOTREACHED */
        case A_RETRY:
                goto retry;
        case A_REBOOT:
                kern_reboot(RB_NOSYNC);
                /* NOTREACHED */
        }

        return (error);
}

static void
vfs_mountroot_conf0(struct sbuf *sb)
{
        char *s, *tok, *mnt, *opt;
        int error;

        sbuf_cat(sb, ".onfail panic\n");
        sbuf_printf(sb, ".timeout %d\n", root_mount_timeout);
        if (boothowto & RB_ASKNAME)
                sbuf_cat(sb, ".ask\n");
#ifdef ROOTDEVNAME
        if (boothowto & RB_DFLTROOT)
                sbuf_printf(sb, "%s\n", ROOTDEVNAME);
#endif
        if (boothowto & RB_CDROM) {
                sbuf_cat(sb, "cd9660:/dev/cd0 ro\n");
                sbuf_cat(sb, ".timeout 0\n");
                sbuf_cat(sb, "cd9660:/dev/cd1 ro\n");
                sbuf_printf(sb, ".timeout %d\n", root_mount_timeout);
        }
        s = kern_getenv("vfs.root.mountfrom");
        if (s != NULL) {
                opt = kern_getenv("vfs.root.mountfrom.options");
                tok = s;
                error = parse_token(&tok, &mnt);
                while (!error) {
                        sbuf_printf(sb, "%s %s\n", mnt,
                            (opt != NULL) ? opt : "");
                        free(mnt, M_TEMP);
                        error = parse_token(&tok, &mnt);
                }
                if (opt != NULL)
                        freeenv(opt);
                freeenv(s);
        }
        if (rootdevnames[0] != NULL)
                sbuf_printf(sb, "%s\n", rootdevnames[0]);
        if (rootdevnames[1] != NULL)
                sbuf_printf(sb, "%s\n", rootdevnames[1]);
#ifdef ROOTDEVNAME
        if (!(boothowto & RB_DFLTROOT))
                sbuf_printf(sb, "%s\n", ROOTDEVNAME);
#endif
        if (!(boothowto & RB_ASKNAME))
                sbuf_cat(sb, ".ask\n");
}

static int
vfs_mountroot_readconf(struct thread *td, struct sbuf *sb)
{
        static char buf[128];
        struct nameidata nd;
        off_t ofs;
        ssize_t resid;
        int error, flags, len;

        NDINIT(&nd, LOOKUP, FOLLOW, UIO_SYSSPACE, "/.mount.conf");
        flags = FREAD;
        error = vn_open(&nd, &flags, 0, NULL);
        if (error)
                return (error);

        NDFREE_PNBUF(&nd);
        ofs = 0;
        len = sizeof(buf) - 1;
        while (1) {
                error = vn_rdwr(UIO_READ, nd.ni_vp, buf, len, ofs,
                    UIO_SYSSPACE, IO_NODELOCKED, td->td_ucred,
                    NOCRED, &resid, td);
                if (error)
                        break;
                if (resid == len)
                        break;
                buf[len - resid] = 0;
                sbuf_printf(sb, "%s", buf);
                ofs += len - resid;
        }

        VOP_UNLOCK(nd.ni_vp);
        vn_close(nd.ni_vp, FREAD, td->td_ucred, td);
        return (error);
}

static void
vfs_mountroot_wait(void)
{
        struct root_hold_token *h;
        struct thread *td;
        struct timeval lastfail;
        int curfail;

        TSENTER();

        curfail = 0;
        lastfail.tv_sec = 0;
        eventratecheck(&lastfail, &curfail, 1);
        td = curthread;
        while (1) {
                g_waitidle(td);
                mtx_lock(&root_holds_mtx);
                if (TAILQ_EMPTY(&root_holds)) {
                        mtx_unlock(&root_holds_mtx);
                        break;
                }
                if (eventratecheck(&lastfail, &curfail, 1)) {
                        printf("Root mount waiting for:");
                        TAILQ_FOREACH(h, &root_holds, list)
                                printf(" %s", h->who);
                        printf("\n");
                }
                TSWAIT("root mount");
                msleep(&root_holds, &root_holds_mtx, PZERO | PDROP, "roothold",
                    hz);
                TSUNWAIT("root mount");
        }
        g_waitidle(td);

        TSEXIT();
}

static int
vfs_mountroot_wait_if_neccessary(const char *fs, const char *dev)
{
        int delay, timeout;

        /*
         * In case of ZFS and NFS we don't have a way to wait for
         * specific device.  Also do the wait if the user forced that
         * behaviour by setting vfs.root_mount_always_wait=1.
         */
        if (strcmp(fs, "zfs") == 0 || strstr(fs, "nfs") != NULL ||
            strcmp(fs, "p9fs") == 0 ||
            dev[0] == '\0' || root_mount_always_wait != 0) {
                vfs_mountroot_wait();
                return (0);
        }

        /*
         * Otherwise, no point in waiting if the device is already there.
         * Note that we must wait for GEOM to finish reconfiguring itself,
         * eg for geom_part(4) to finish tasting.
         */
        g_waitidle(curthread);
        if (parse_mount_dev_present(dev))
                return (0);

        /*
         * No luck.  Let's wait.  This code looks weird, but it's that way
         * to behave exactly as it used to work before.
         */
        vfs_mountroot_wait();
        if (parse_mount_dev_present(dev))
                return (0);
        printf("mountroot: waiting for device %s...\n", dev);
        delay = hz / 10;
        timeout = root_mount_timeout * hz;
        do {
                pause("rmdev", delay);
                timeout -= delay;
        } while (timeout > 0 && !parse_mount_dev_present(dev));

        if (timeout <= 0)
                return (ENODEV);

        return (0);
}

void
vfs_mountroot(void)
{
        struct mount *mp;
        struct sbuf *sb;
        struct thread *td;
        time_t timebase;
        int error;

        mtx_assert(&Giant, MA_NOTOWNED);

        TSENTER();

        td = curthread;

        sb = sbuf_new_auto();
        vfs_mountroot_conf0(sb);
        sbuf_finish(sb);

        error = vfs_mountroot_devfs(td, &mp);
        while (!error) {
                error = vfs_mountroot_parse(sb, mp);
                if (!error) {
                        vfs_mountroot_shuffle(td, mp);
                        sbuf_clear(sb);
                        error = vfs_mountroot_readconf(td, sb);
                        sbuf_finish(sb);
                }
        }

        sbuf_delete(sb);

        /*
         * Iterate over all currently mounted file systems and use
         * the time stamp found to check and/or initialize the RTC.
         * Call inittodr() only once and pass it the largest of the
         * timestamps we encounter.
         */
        timebase = 0;
        mtx_lock(&mountlist_mtx);
        mp = TAILQ_FIRST(&mountlist);
        while (mp != NULL) {
                if (mp->mnt_time > timebase)
                        timebase = mp->mnt_time;
                mp = TAILQ_NEXT(mp, mnt_list);
        }
        mtx_unlock(&mountlist_mtx);
        inittodr(timebase);

        /* Keep prison0's root in sync with the global rootvnode. */
        mtx_lock(&prison0.pr_mtx);
        prison0.pr_root = rootvnode;
        vref(prison0.pr_root);
        mtx_unlock(&prison0.pr_mtx);

        mtx_lock(&root_holds_mtx);
        atomic_store_rel_int(&root_mount_complete, 1);
        wakeup(&root_mount_complete);
        mtx_unlock(&root_holds_mtx);

        EVENTHANDLER_INVOKE(mountroot);

        TSEXIT();
}

static struct mntarg *
parse_mountroot_options(struct mntarg *ma, const char *options)
{
        char *p;
        char *name, *name_arg;
        char *val, *val_arg;
        char *opts;

        if (options == NULL || options[0] == '\0')
                return (ma);

        p = opts = strdup(options, M_MOUNT);
        if (opts == NULL) {
                return (ma);
        }

        while((name = strsep(&p, ",")) != NULL) {
                if (name[0] == '\0')
                        break;

                val = strchr(name, '=');
                if (val != NULL) {
                        *val = '\0';
                        ++val;
                }
                if (strcmp(name, "rw") == 0 || strcmp(name, "noro") == 0) {
                        /*
                         * The first time we mount the root file system,
                         * we need to mount 'ro', so We need to ignore
                         * 'rw' and 'noro' mount options.
                         */
                        continue;
                }
                name_arg = strdup(name, M_MOUNT);
                val_arg = NULL;
                if (val != NULL)
                        val_arg = strdup(val, M_MOUNT);

                ma = mount_arg(ma, name_arg, val_arg,
                    (val_arg != NULL ? -1 : 0));
        }
        free(opts, M_MOUNT);
        return (ma);
}