/*
* The system call that results in changing the rootfs.
*/
static int
kern_reroot(void)
{
struct vnode *oldrootvnode, *vp;
struct mount *mp, *devmp;
int error;
if (curproc != initproc)
return (EPERM);
/*
* Mark the filesystem containing currently-running executable
* (the temporary copy of init(8)) busy.
*/
vp = curproc->p_textvp;
error = vn_lock(vp, LK_SHARED);
if (error != 0)
return (error);
mp = vp->v_mount;
error = vfs_busy(mp, MBF_NOWAIT);
if (error != 0) {
vfs_ref(mp);
VOP_UNLOCK(vp, 0);
error = vfs_busy(mp, 0);
vn_lock(vp, LK_SHARED | LK_RETRY);
vfs_rel(mp);
if (error != 0) {
VOP_UNLOCK(vp, 0);
return (ENOENT);
}
if (vp->v_iflag & VI_DOOMED) {
VOP_UNLOCK(vp, 0);
vfs_unbusy(mp);
return (ENOENT);
}
}
VOP_UNLOCK(vp, 0);
/*
* Remove the filesystem containing currently-running executable
* from the mount list, to prevent it from being unmounted
* by vfs_unmountall(), and to avoid confusing vfs_mountroot().
*
* Also preserve /dev - forcibly unmounting it could cause driver
* reinitialization.
*/
vfs_ref(rootdevmp);
devmp = rootdevmp;
rootdevmp = NULL;
mtx_lock(&mountlist_mtx);
TAILQ_REMOVE(&mountlist, mp, mnt_list);
TAILQ_REMOVE(&mountlist, devmp, mnt_list);
mtx_unlock(&mountlist_mtx);
oldrootvnode = rootvnode;
/*
* Unmount everything except for the two filesystems preserved above.
*/
vfs_unmountall();
/*
* Add /dev back; vfs_mountroot() will move it into its new place.
*/
mtx_lock(&mountlist_mtx);
TAILQ_INSERT_HEAD(&mountlist, devmp, mnt_list);
mtx_unlock(&mountlist_mtx);
rootdevmp = devmp;
vfs_rel(rootdevmp);
/*
* Mount the new rootfs.
*/
vfs_mountroot();
/*
* Update all references to the old rootvnode.
*/
mountcheckdirs(oldrootvnode, rootvnode);
/*
* Add the temporary filesystem back and unbusy it.
*/
mtx_lock(&mountlist_mtx);
TAILQ_INSERT_TAIL(&mountlist, mp, mnt_list);
mtx_unlock(&mountlist_mtx);
vfs_unbusy(mp);
return (0);
}
int
domount(kthread_t *td, vnode_t *vp, const char *fstype, char *fspath,
char *fspec, int fsflags)
{
struct mount *mp;
struct vfsconf *vfsp;
struct ucred *newcr, *oldcr;
int error;
/*
* Be ultra-paranoid about making sure the type and fspath
* variables will fit in our mp buffers, including the
* terminating NUL.
*/
if (strlen(fstype) >= MFSNAMELEN || strlen(fspath) >= MNAMELEN)
return (ENAMETOOLONG);
vfsp = vfs_byname_kld(fstype, td, &error);
if (vfsp == NULL)
return (ENODEV);
if (vp->v_type != VDIR)
return (ENOTDIR);
simple_lock(&vp->v_interlock);
if ((vp->v_iflag & VI_MOUNT) != 0 ||
vp->v_mountedhere != NULL) {
simple_unlock(&vp->v_interlock);
return (EBUSY);
}
vp->v_iflag |= VI_MOUNT;
simple_unlock(&vp->v_interlock);
/*
* Allocate and initialize the filesystem.
*/
vn_lock(vp, LK_SHARED | LK_RETRY);
mp = vfs_mount_alloc(vp, vfsp, fspath, td);
VOP_UNLOCK(vp);
mp->mnt_optnew = NULL;
vfs_setmntopt(mp, "from", fspec, 0);
mp->mnt_optnew = mp->mnt_opt;
mp->mnt_opt = NULL;
/*
* Set the mount level flags.
* crdup() can sleep, so do it before acquiring a mutex.
*/
newcr = crdup(kcred);
MNT_ILOCK(mp);
if (fsflags & MNT_RDONLY)
mp->mnt_flag |= MNT_RDONLY;
mp->mnt_flag &=~ MNT_UPDATEMASK;
mp->mnt_flag |= fsflags & (MNT_UPDATEMASK | MNT_FORCE | MNT_ROOTFS);
/*
* Unprivileged user can trigger mounting a snapshot, but we don't want
* him to unmount it, so we switch to privileged credentials.
*/
oldcr = mp->mnt_cred;
mp->mnt_cred = newcr;
mp->mnt_stat.f_owner = mp->mnt_cred->cr_uid;
MNT_IUNLOCK(mp);
crfree(oldcr);
/*
* Mount the filesystem.
* XXX The final recipients of VFS_MOUNT just overwrite the ndp they
* get. No freeing of cn_pnbuf.
*/
error = VFS_MOUNT(mp, td);
if (!error) {
if (mp->mnt_opt != NULL)
vfs_freeopts(mp->mnt_opt);
mp->mnt_opt = mp->mnt_optnew;
(void)VFS_STATFS(mp, &mp->mnt_stat, td);
}
/*
* Prevent external consumers of mount options from reading
* mnt_optnew.
*/
mp->mnt_optnew = NULL;
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
/*
* Put the new filesystem on the mount list after root.
*/
#ifdef FREEBSD_NAMECACHE
cache_purge(vp);
#endif
if (!error) {
vnode_t *mvp;
simple_lock(&vp->v_interlock);
vp->v_iflag &= ~VI_MOUNT;
simple_unlock(&vp->v_interlock);
vp->v_mountedhere = mp;
mountlist_append(mp);
vfs_event_signal(NULL, VQ_MOUNT, 0);
if (VFS_ROOT(mp, LK_EXCLUSIVE, &mvp, td))
panic("mount: lost mount");
mountcheckdirs(vp, mvp);
vput(mvp);
VOP_UNLOCK(vp);
if ((mp->mnt_flag & MNT_RDONLY) == 0)
vfs_syncer_add_to_worklist(mp);
vfs_unbusy(mp, td);
vfs_mountedfrom(mp, fspec);
} else {
simple_lock(&vp->v_interlock);
vp->v_iflag &= ~VI_MOUNT;
simple_unlock(&vp->v_interlock);
VOP_UNLOCK(vp);
vfs_unbusy(mp, td);
vfs_mount_destroy(mp);
}
return (error);
}
