FreeBSD/Linux Kernel Cross Reference
sys/geom/geom_bsd.c

     /*-
      * Copyright (c) 2002 Poul-Henning Kamp
      * Copyright (c) 2002 Networks Associates Technology, Inc.
      * All rights reserved.
      *
      * This software was developed for the FreeBSD Project by Poul-Henning Kamp
      * and NAI Labs, the Security Research Division of Network Associates, Inc.
      * under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the
      * DARPA CHATS research program.
     *
     * 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. The names of the authors may not 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.
     *
     * $FreeBSD: releng/5.1/sys/geom/geom_bsd.c 114785 2003-05-06 19:36:13Z phk $
     *
     * This is the method for dealing with BSD disklabels.  It has been
     * extensively (by my standards at least) commented, in the vain hope that
     * it will serve as the source in future copy&paste operations.
     */
    
    #include <sys/param.h>
    #include <sys/endian.h>
    #include <sys/systm.h>
    #include <sys/kernel.h>
    #include <sys/conf.h>
    #include <sys/bio.h>
    #include <sys/malloc.h>
    #include <sys/lock.h>
    #include <sys/mutex.h>
    #include <sys/md5.h>
    #include <sys/errno.h>
    #include <sys/disklabel.h>
    #include <geom/geom.h>
    #include <geom/geom_slice.h>
    
    #define BSD_CLASS_NAME "BSD"
    
    #define ALPHA_LABEL_OFFSET      64
    
    #define LABELSIZE (148 + 16 * MAXPARTITIONS)
    
    static void g_bsd_hotwrite(void *arg, int flag);
    /*
     * Our private data about one instance.  All the rest is handled by the
     * slice code and stored in its softc, so this is just the stuff
     * specific to BSD disklabels.
     */
    struct g_bsd_softc {
            off_t   labeloffset;
            off_t   mbroffset;
            off_t   rawoffset;
            struct disklabel ondisk;
            u_char  label[LABELSIZE];
            u_char  labelsum[16];
    };
    
    /*
     * Modify our slicer to match proposed disklabel, if possible.
     * This is where we make sure we don't do something stupid.
     */
    static int
    g_bsd_modify(struct g_geom *gp, u_char *label)
    {
            int i, error;
            struct partition *ppp;
            struct g_slicer *gsp;
            struct g_consumer *cp;
            struct g_bsd_softc *ms;
            u_int secsize, u;
            off_t mediasize, rawoffset, o;
            struct disklabel dl;
            MD5_CTX md5sum;
    
            g_topology_assert();
            gsp = gp->softc;
            ms = gsp->softc;
    
            error = bsd_disklabel_le_dec(label, &dl, MAXPARTITIONS);
           if (error) {
                   return (error);
           }
   
           /* Get dimensions of our device. */
           cp = LIST_FIRST(&gp->consumer);
           secsize = cp->provider->sectorsize;
           mediasize = cp->provider->mediasize;
   
   #ifdef notyet
           /*
            * Indications are that the d_secperunit is not correctly
            * initialized in many cases, and since we don't need it
            * for anything, we dont strictly need this test.
            * Preemptive action to avoid confusing people in disklabel(8)
            * may be in order.
            */
           /* The label cannot claim a larger size than the media. */
           if ((off_t)dl.d_secperunit * dl.d_secsize > mediasize)
                   return (EINVAL);
   #endif
   
           /* ... or a smaller sector size. */
           if (dl.d_secsize < secsize) {
                   return (EINVAL);
           }
   
           /* ... or a non-multiple sector size. */
           if (dl.d_secsize % secsize != 0) {
                   return (EINVAL);
           }
   
           /* Historical braindamage... */
           rawoffset = (off_t)dl.d_partitions[RAW_PART].p_offset * dl.d_secsize;
   
           for (i = 0; i < dl.d_npartitions; i++) {
                   ppp = &dl.d_partitions[i];
                   if (ppp->p_size == 0)
                           continue;
                   o = (off_t)ppp->p_offset * dl.d_secsize;
   
                   if (o < rawoffset)
                           rawoffset = 0;
           }
           
           if (rawoffset != 0 && (off_t)rawoffset != ms->mbroffset)
                   printf("WARNING: Expected rawoffset %jd, found %jd\n",
                       (intmax_t)ms->mbroffset/dl.d_secsize,
                       (intmax_t)rawoffset/dl.d_secsize);
   
           /* Don't munge open partitions. */
           for (i = 0; i < dl.d_npartitions; i++) {
                   ppp = &dl.d_partitions[i];
   
                   o = (off_t)ppp->p_offset * dl.d_secsize;
                   if (o == 0)
                           o = rawoffset;
                   error = g_slice_config(gp, i, G_SLICE_CONFIG_CHECK,
                       o - rawoffset,
                       (off_t)ppp->p_size * dl.d_secsize,
                        dl.d_secsize,
                       "%s%c", gp->name, 'a' + i);
                   if (error)
                           return (error);
           }
   
           /* Look good, go for it... */
           for (u = 0; u < gsp->nslice; u++) {
                   ppp = &dl.d_partitions[u];
                   o = (off_t)ppp->p_offset * dl.d_secsize;
                   if (o == 0)
                           o = rawoffset;
                   g_slice_config(gp, u, G_SLICE_CONFIG_SET,
                       o - rawoffset,
                       (off_t)ppp->p_size * dl.d_secsize,
                        dl.d_secsize,
                       "%s%c", gp->name, 'a' + u);
           }
   
           /* Update our softc */
           ms->ondisk = dl;
           if (label != ms->label)
                   bcopy(label, ms->label, LABELSIZE);
           ms->rawoffset = rawoffset;
   
           /*
            * In order to avoid recursively attaching to the same
            * on-disk label (it's usually visible through the 'c'
            * partition) we calculate an MD5 and ask if other BSD's
            * below us love that label.  If they do, we don't.
            */
           MD5Init(&md5sum);
           MD5Update(&md5sum, ms->label, sizeof(ms->label));
           MD5Final(ms->labelsum, &md5sum);
   
           return (0);
   }
   
   /*
    * This is an internal helper function, called multiple times from the taste
    * function to try to locate a disklabel on the disk.  More civilized formats
    * will not need this, as there is only one possible place on disk to look
    * for the magic spot.
    */
   
   static int
   g_bsd_try(struct g_geom *gp, struct g_slicer *gsp, struct g_consumer *cp, int secsize, struct g_bsd_softc *ms, off_t offset)
   {
           int error;
           u_char *buf;
           struct disklabel *dl;
           off_t secoff;
   
           /*
            * We need to read entire aligned sectors, and we assume that the
            * disklabel does not span sectors, so one sector is enough.
            */
           error = 0;
           secoff = offset % secsize;
           buf = g_read_data(cp, offset - secoff, secsize, &error);
           if (buf == NULL || error != 0)
                   return (ENOENT);
   
           /* Decode into our native format. */
           dl = &ms->ondisk;
           error = bsd_disklabel_le_dec(buf + secoff, dl, MAXPARTITIONS);
           if (!error)
                   bcopy(buf + secoff, ms->label, LABELSIZE);
   
           /* Remember to free the buffer g_read_data() gave us. */
           g_free(buf);
   
           ms->labeloffset = offset;
           return (error);
   }
   
   /*
    * This function writes the current label to disk, possibly updating
    * the alpha SRM checksum.
    */
   
   static int
   g_bsd_writelabel(struct g_geom *gp, u_char *bootcode)
   {
           off_t secoff;
           u_int secsize;
           struct g_consumer *cp;
           struct g_slicer *gsp;
           struct g_bsd_softc *ms;
           u_char *buf;
           uint64_t sum;
           int error, i;
   
           gsp = gp->softc;
           ms = gsp->softc;
           cp = LIST_FIRST(&gp->consumer);
           /* Get sector size, we need it to read data. */
           secsize = cp->provider->sectorsize;
           secoff = ms->labeloffset % secsize;
           if (bootcode == NULL) {
                   buf = g_read_data(cp, ms->labeloffset - secoff, secsize, &error);
                   if (buf == NULL || error != 0)
                           return (error);
                   bcopy(ms->label, buf + secoff, sizeof(ms->label));
           } else {
                   buf = bootcode;
                   bcopy(ms->label, buf + ms->labeloffset, sizeof(ms->label));
           }
           if (ms->labeloffset == ALPHA_LABEL_OFFSET) {
                   sum = 0;
                   for (i = 0; i < 63; i++)
                           sum += le64dec(buf + i * 8);
                   le64enc(buf + 504, sum);
           }
           if (bootcode == NULL) {
                   error = g_write_data(cp, ms->labeloffset - secoff, buf, secsize);
                   g_free(buf);
           } else {
                   error = g_write_data(cp, 0, bootcode, BBSIZE);
           }
           return(error);
   }
   
   
   /*
    * Implement certain ioctls to modify disklabels with.  This function
    * is called by the event handler thread with topology locked as result
    * of the g_post_event() in g_bsd_start().  It is not necessary to keep
    * topology locked all the time but make sure to return with topology
    * locked as well.
    */
   
   static void
   g_bsd_ioctl(void *arg, int flag)
   {
           struct bio *bp;
           struct g_geom *gp;
           struct g_slicer *gsp;
           struct g_bsd_softc *ms;
           struct g_ioctl *gio;
           u_char *label;
           int error;
   
           g_topology_assert();
           bp = arg;
           if (flag == EV_CANCEL) {
                   g_io_deliver(bp, ENXIO);
                   return;
           }
   
           gp = bp->bio_to->geom;
           gsp = gp->softc;
           ms = gsp->softc;
           gio = (struct g_ioctl *)bp->bio_data;
   
           label = g_malloc(LABELSIZE, M_WAITOK);
   
           /* The disklabel to set is the ioctl argument. */
           bsd_disklabel_le_enc(label, gio->data);
   
           /* Validate and modify our slice instance to match. */
           error = g_bsd_modify(gp, label);        /* Picks up topology lock on success. */
           g_free(label);
           if (error || gio->cmd == DIOCSDINFO) {
                   g_io_deliver(bp, error);
                   return;
           }
           
           KASSERT(gio->cmd == DIOCWDINFO, ("Unknown ioctl in g_bsd_ioctl"));
           g_io_deliver(bp, g_bsd_writelabel(gp, NULL));
   }
   
   /*
    * Rewrite the bootblock, which is BBSIZE bytes from the start of the disk.
    * We punch down the disklabel where we expect it to be before writing.
    */
   static int
   g_bsd_diocbsdbb(dev_t dev, u_long cmd __unused, caddr_t data, int fflag __unused, struct thread *td __unused)
   {
           struct g_geom *gp;
           struct g_slicer *gsp;
           struct g_bsd_softc *ms;
           struct g_consumer *cp;
           u_char *buf;
           void *p;
           u_int secsize;
           int error, i;
           uint64_t sum;
   
           /* Get hold of the interesting bits from the bio. */
           gp = (void *)dev;
           gsp = gp->softc;
           ms = gsp->softc;
   
           /* The disklabel to set is the ioctl argument. */
           buf = g_malloc(BBSIZE, M_WAITOK);
           p = *(void **)data;
           error = copyin(p, buf, BBSIZE);
           if (!error) {
                   DROP_GIANT();
                   g_topology_lock();
                   /* Validate and modify our slice instance to match. */
                   error = g_bsd_modify(gp, buf + ms->labeloffset);
                   if (!error) {
                           cp = LIST_FIRST(&gp->consumer);
                           secsize = cp->provider->sectorsize;
                           if (ms->labeloffset == ALPHA_LABEL_OFFSET) {
                                   sum = 0;
                                   for (i = 0; i < 63; i++)
                                           sum += le64dec(buf + i * 8);
                                   le64enc(buf + 504, sum);
                           }
                           error = g_write_data(cp, 0, buf, BBSIZE);
                   }
                   g_topology_unlock();
                   PICKUP_GIANT();
           }
           g_free(buf);
           return (error);
   }
   
   /*
    * If the user tries to overwrite our disklabel through an open partition
    * or via a magicwrite config call, we end up here and try to prevent
    * footshooting as best we can.
    */
   static void
   g_bsd_hotwrite(void *arg, int flag)
   {
           struct bio *bp;
           struct g_geom *gp;
           struct g_slicer *gsp;
           struct g_slice *gsl;
           struct g_bsd_softc *ms;
           u_char *p;
           int error;
           
           g_topology_assert();
           /*
            * We should never get canceled, because that would amount to a removal
            * of the geom while there was outstanding I/O requests.
            */
           KASSERT(flag != EV_CANCEL, ("g_bsd_hotwrite cancelled"));
           bp = arg;
           gp = bp->bio_to->geom;
           gsp = gp->softc;
           ms = gsp->softc;
           gsl = &gsp->slices[bp->bio_to->index];
           p = (u_char*)bp->bio_data + ms->labeloffset 
               - (bp->bio_offset + gsl->offset);
           error = g_bsd_modify(gp, p);
           if (error) {
                   g_io_deliver(bp, EPERM);
                   return;
           }
           g_slice_finish_hot(bp);
   }
   
   /*-
    * This start routine is only called for non-trivial requests, all the
    * trivial ones are handled autonomously by the slice code.
    * For requests we handle here, we must call the g_io_deliver() on the
    * bio, and return non-zero to indicate to the slice code that we did so.
    * This code executes in the "DOWN" I/O path, this means:
    *    * No sleeping.
    *    * Don't grab the topology lock.
    *    * Don't call biowait, g_getattr(), g_setattr() or g_read_data()
    */
   
   static int
   g_bsd_start(struct bio *bp)
   {
           struct g_geom *gp;
           struct g_bsd_softc *ms;
           struct g_slicer *gsp;
           struct g_ioctl *gio;
           int error;
   
           gp = bp->bio_to->geom;
           gsp = gp->softc;
           ms = gsp->softc;
           switch(bp->bio_cmd) {
           case BIO_GETATTR:
                   if (g_handleattr(bp, "BSD::labelsum", ms->labelsum,
                       sizeof(ms->labelsum)))
                           return (1);
                   break;
           default:
                   KASSERT(0 == 1, ("Unknown bio_cmd in g_bsd_start (%d)",
                       bp->bio_cmd));
           }
   
           /* We only handle ioctl(2) requests of the right format. */
           if (strcmp(bp->bio_attribute, "GEOM::ioctl"))
                   return (0);
           else if (bp->bio_length != sizeof(*gio))
                   return (0);
   
           /* Get hold of the ioctl parameters. */
           gio = (struct g_ioctl *)bp->bio_data;
   
           switch (gio->cmd) {
           case DIOCGDINFO:
                   /* Return a copy of the disklabel to userland. */
                   bsd_disklabel_le_dec(ms->label, gio->data, MAXPARTITIONS);
                   g_io_deliver(bp, 0);
                   return (1);
           case DIOCBSDBB:
                   gio->func = g_bsd_diocbsdbb;
                   gio->dev = (void *)gp;
                   g_io_deliver(bp, EDIRIOCTL);
                   return (1);
           case DIOCSDINFO:
           case DIOCWDINFO:
                   /*
                    * These we cannot do without the topology lock and some
                    * some I/O requests.  Ask the event-handler to schedule
                    * us in a less restricted environment.
                    */
                   error = g_post_event(g_bsd_ioctl, bp, M_NOWAIT, gp, NULL);
                   if (error)
                           g_io_deliver(bp, error);
                   /*
                    * We must return non-zero to indicate that we will deal
                    * with this bio, even though we have not done so yet.
                    */
                   return (1);
           default:
                   return (0);
           }
   }
   
   /*
    * Dump configuration information in XML format.
    * Notice that the function is called once for the geom and once for each
    * consumer and provider.  We let g_slice_dumpconf() do most of the work.
    */
   static void
   g_bsd_dumpconf(struct sbuf *sb, const char *indent, struct g_geom *gp, struct g_consumer *cp, struct g_provider *pp)
   {
           struct g_bsd_softc *ms;
           struct g_slicer *gsp;
   
           gsp = gp->softc;
           ms = gsp->softc;
           g_slice_dumpconf(sb, indent, gp, cp, pp);
           if (indent != NULL && pp == NULL && cp == NULL) {
                   sbuf_printf(sb, "%s<labeloffset>%jd</labeloffset>\n",
                       indent, (intmax_t)ms->labeloffset);
                   sbuf_printf(sb, "%s<rawoffset>%jd</rawoffset>\n",
                       indent, (intmax_t)ms->rawoffset);
                   sbuf_printf(sb, "%s<mbroffset>%jd</mbroffset>\n",
                       indent, (intmax_t)ms->mbroffset);
           } else if (pp != NULL) {
                   if (indent == NULL)
                           sbuf_printf(sb, " ty %d",
                               ms->ondisk.d_partitions[pp->index].p_fstype);
                   else
                           sbuf_printf(sb, "%s<type>%d</type>\n", indent,
                               ms->ondisk.d_partitions[pp->index].p_fstype);
           }
   }
   
   /*
    * The taste function is called from the event-handler, with the topology
    * lock already held and a provider to examine.  The flags are unused.
    *
    * If flags == G_TF_NORMAL, the idea is to take a bite of the provider and
    * if we find valid, consistent magic on it, build a geom on it.
    * any magic bits which indicate that we should automatically put a BSD
    * geom on it.
    *
    * There may be cases where the operator would like to put a BSD-geom on
    * providers which do not meet all of the requirements.  This can be done
    * by instead passing the G_TF_INSIST flag, which will override these
    * checks.
    *
    * The final flags value is G_TF_TRANSPARENT, which instructs the method
    * to put a geom on top of the provider and configure it to be as transparent
    * as possible.  This is not really relevant to the BSD method and therefore
    * not implemented here.
    */
   
   static struct g_geom *
   g_bsd_taste(struct g_class *mp, struct g_provider *pp, int flags)
   {
           struct g_geom *gp;
           struct g_consumer *cp;
           int error, i;
           struct g_bsd_softc *ms;
           u_int secsize;
           struct g_slicer *gsp;
           u_char hash[16];
           MD5_CTX md5sum;
   
           g_trace(G_T_TOPOLOGY, "bsd_taste(%s,%s)", mp->name, pp->name);
           g_topology_assert();
   
           /* We don't implement transparent inserts. */
           if (flags == G_TF_TRANSPARENT)
                   return (NULL);
   
           /*
            * BSD labels are a subclass of the general "slicing" topology so
            * a lot of the work can be done by the common "slice" code.
            * Create a geom with space for MAXPARTITIONS providers, one consumer
            * and a softc structure for us.  Specify the provider to attach
            * the consumer to and our "start" routine for special requests.
            * The provider is opened with mode (1,0,0) so we can do reads
            * from it.
            */
           gp = g_slice_new(mp, MAXPARTITIONS, pp, &cp, &ms,
                sizeof(*ms), g_bsd_start);
           if (gp == NULL)
                   return (NULL);
   
           /*
            * Fill in the optional details, in our case we have a dumpconf
            * routine which the "slice" code should call at the right time
            */
           gp->dumpconf = g_bsd_dumpconf;
   
           /* Get the geom_slicer softc from the geom. */
           gsp = gp->softc;
   
           /*
            * The do...while loop here allows us to have multiple escapes
            * using a simple "break".  This improves code clarity without
            * ending up in deep nesting and without using goto or come from.
            */
           do {
                   /*
                    * If the provider is an MBR we will only auto attach
                    * to type 165 slices in the G_TF_NORMAL case.  We will
                    * attach to any other type.
                    */
                   error = g_getattr("MBR::type", cp, &i);
                   if (!error) {
                           if (i != 165 && flags == G_TF_NORMAL)
                                   break;
                           error = g_getattr("MBR::offset", cp, &ms->mbroffset);
                           if (error)
                                   break;
                   }
   
                   /* Same thing if we are inside a PC98 */
                   error = g_getattr("PC98::type", cp, &i);
                   if (!error) {
                           if (i != 0xc494 && flags == G_TF_NORMAL)
                                   break;
                           error = g_getattr("PC98::offset", cp, &ms->mbroffset);
                           if (error)
                                   break;
                   }
   
                   /* Get sector size, we need it to read data. */
                   secsize = cp->provider->sectorsize;
                   if (secsize < 512)
                           break;
   
                   /* First look for a label at the start of the second sector. */
                   error = g_bsd_try(gp, gsp, cp, secsize, ms, secsize);
   
                   /* Next, look for alpha labels */
                   if (error)
                           error = g_bsd_try(gp, gsp, cp, secsize, ms,
                               ALPHA_LABEL_OFFSET);
   
                   /* If we didn't find a label, punt. */
                   if (error)
                           break;
   
                   /*
                    * In order to avoid recursively attaching to the same
                    * on-disk label (it's usually visible through the 'c'
                    * partition) we calculate an MD5 and ask if other BSD's
                    * below us love that label.  If they do, we don't.
                    */
                   MD5Init(&md5sum);
                   MD5Update(&md5sum, ms->label, sizeof(ms->label));
                   MD5Final(ms->labelsum, &md5sum);
   
                   error = g_getattr("BSD::labelsum", cp, &hash);
                   if (!error && !strncmp(ms->labelsum, hash, sizeof(hash)))
                           break;
   
                   /*
                    * Process the found disklabel, and modify our "slice"
                    * instance to match it, if possible.
                    */
                   error = g_bsd_modify(gp, ms->label);
           } while (0);
   
           /* Success or failure, we can close our provider now. */
           error = g_access_rel(cp, -1, 0, 0);
   
           /* If we have configured any providers, return the new geom. */
           if (gsp->nprovider > 0) {
                   g_slice_conf_hot(gp, 0, ms->labeloffset, LABELSIZE,
                       G_SLICE_HOT_ALLOW, G_SLICE_HOT_DENY, G_SLICE_HOT_CALL);
                   gsp->hot = g_bsd_hotwrite;
                   return (gp);
           }
           /*
            * ...else push the "self-destruct" button, by spoiling our own
            * consumer.  This triggers a call to g_slice_spoiled which will
            * dismantle what was setup.
            */
           g_slice_spoiled(cp);
           return (NULL);
   }
   
   struct h0h0 {
           struct g_geom *gp;
           struct g_bsd_softc *ms;
           u_char *label;
           int error;
   };
   
   static void
   g_bsd_callconfig(void *arg, int flag)
   {
           struct h0h0 *hp;
   
           hp = arg;
           hp->error = g_bsd_modify(hp->gp, hp->label);
           if (!hp->error)
                   hp->error = g_bsd_writelabel(hp->gp, NULL);
   }
   
   /*
    * NB! curthread is user process which GCTL'ed.
    */
   static int
   g_bsd_config(struct gctl_req *req, struct g_geom *gp, const char *verb)
   {
           u_char *label;
           int error, i;
           struct h0h0 h0h0;
           struct g_slicer *gsp;
           struct g_consumer *cp;
           struct g_bsd_softc *ms;
   
           i = 0;
           g_topology_assert();
           cp = LIST_FIRST(&gp->consumer);
           gsp = gp->softc;
           ms = gsp->softc;
           if (!strcmp(verb, "read mbroffset")) {
                   error = gctl_set_param(req, "mbroffset",
                       &ms->mbroffset, sizeof(ms->mbroffset));
                   return (error);
           } else if (!strcmp(verb, "write label")) {
                   label = gctl_get_paraml(req, "label", LABELSIZE);
                   if (label == NULL)
                           return (EINVAL);
                   h0h0.gp = gp;
                   h0h0.ms = gsp->softc;
                   h0h0.label = label;
                   h0h0.error = -1;
                   /* XXX: Does this reference register with our selfdestruct code ? */
                   error = g_access_rel(cp, 1, 1, 1);
                   if (error) {
                           g_free(label);
                           return (error);
                   }
                   g_topology_unlock();
                   g_waitfor_event(g_bsd_callconfig, &h0h0, M_WAITOK, gp, NULL);
                   g_topology_lock();
                   error = h0h0.error;
                   g_access_rel(cp, -1, -1, -1);
                   g_free(label);
           } else if (!strcmp(verb, "write bootcode")) {
                   label = gctl_get_paraml(req, "bootcode", BBSIZE);
                   if (label == NULL)
                           return (EINVAL);
                   /* XXX: Does this reference register with our selfdestruct code ? */
                   error = g_access_rel(cp, 1, 1, 1);
                   if (error) {
                           g_free(label);
                           return (error);
                   }
                   error = g_bsd_writelabel(gp, label);
                   g_access_rel(cp, -1, -1, -1);
                   g_free(label);
           } else {
                   return (gctl_error(req, "Unknown verb parameter"));
           }
   
           return (error);
   }
   
   /* Finally, register with GEOM infrastructure. */
   static struct g_class g_bsd_class = {
           .name = BSD_CLASS_NAME,
           .taste = g_bsd_taste,
           .config_geom = g_bsd_config,
           G_CLASS_INITIALIZER
   };
   
   DECLARE_GEOM_CLASS(g_bsd_class, g_bsd);

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