FreeBSD/Linux Kernel Cross Reference
sys/dev/cgd.c

     /* $NetBSD: cgd.c,v 1.42.2.1 2007/07/01 17:09:24 bouyer Exp $ */
     
     /*-
      * Copyright (c) 2002 The NetBSD Foundation, Inc.
      * All rights reserved.
      *
      * This code is derived from software contributed to The NetBSD Foundation
      * by Roland C. Dowdeswell.
      *
     * 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. All advertising materials mentioning features or use of this software
     *    must display the following acknowledgement:
     *        This product includes software developed by the NetBSD
     *        Foundation, Inc. and its contributors.
     * 4. Neither the name of The NetBSD Foundation 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 NETBSD FOUNDATION, INC. 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 FOUNDATION 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 <sys/cdefs.h>
    __KERNEL_RCSID(0, "$NetBSD: cgd.c,v 1.42.2.1 2007/07/01 17:09:24 bouyer Exp $");
    
    #include <sys/types.h>
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/proc.h>
    #include <sys/errno.h>
    #include <sys/buf.h>
    #include <sys/bufq.h>
    #include <sys/malloc.h>
    #include <sys/pool.h>
    #include <sys/ioctl.h>
    #include <sys/device.h>
    #include <sys/disk.h>
    #include <sys/disklabel.h>
    #include <sys/fcntl.h>
    #include <sys/vnode.h>
    #include <sys/lock.h>
    #include <sys/conf.h>
    
    #include <dev/dkvar.h>
    #include <dev/cgdvar.h>
    
    /* Entry Point Functions */
    
    void    cgdattach(int);
    
    static dev_type_open(cgdopen);
    static dev_type_close(cgdclose);
    static dev_type_read(cgdread);
    static dev_type_write(cgdwrite);
    static dev_type_ioctl(cgdioctl);
    static dev_type_strategy(cgdstrategy);
    static dev_type_dump(cgddump);
    static dev_type_size(cgdsize);
    
    const struct bdevsw cgd_bdevsw = {
            cgdopen, cgdclose, cgdstrategy, cgdioctl,
            cgddump, cgdsize, D_DISK
    };
    
    const struct cdevsw cgd_cdevsw = {
            cgdopen, cgdclose, cgdread, cgdwrite, cgdioctl,
            nostop, notty, nopoll, nommap, nokqfilter, D_DISK
    };
    
    /* Internal Functions */
    
    static int      cgdstart(struct dk_softc *, struct buf *);
    static void     cgdiodone(struct buf *);
    
    static int      cgd_ioctl_set(struct cgd_softc *, void *, struct lwp *);
    static int      cgd_ioctl_clr(struct cgd_softc *, void *, struct lwp *);
    static int      cgdinit(struct cgd_softc *, const char *, struct vnode *,
                            struct lwp *);
    static void     cgd_cipher(struct cgd_softc *, caddr_t, caddr_t,
                               size_t, daddr_t, size_t, int);
    
    /* Pseudo-disk Interface */
    
   static struct dk_intf the_dkintf = {
           DTYPE_CGD,
           "cgd",
           cgdopen,
           cgdclose,
           cgdstrategy,
           cgdstart,
   };
   static struct dk_intf *di = &the_dkintf;
   
   static struct dkdriver cgddkdriver = {
           .d_strategy = cgdstrategy,
           .d_minphys = minphys,
   };
   
   /* DIAGNOSTIC and DEBUG definitions */
   
   #if defined(CGDDEBUG) && !defined(DEBUG)
   #define DEBUG
   #endif
   
   #ifdef DEBUG
   int cgddebug = 0;
   
   #define CGDB_FOLLOW     0x1
   #define CGDB_IO 0x2
   #define CGDB_CRYPTO     0x4
   
   #define IFDEBUG(x,y)            if (cgddebug & (x)) y
   #define DPRINTF(x,y)            IFDEBUG(x, printf y)
   #define DPRINTF_FOLLOW(y)       DPRINTF(CGDB_FOLLOW, y)
   
   static void     hexprint(const char *, void *, int);
   
   #else
   #define IFDEBUG(x,y)
   #define DPRINTF(x,y)
   #define DPRINTF_FOLLOW(y)
   #endif
   
   #ifdef DIAGNOSTIC
   #define DIAGPANIC(x)            panic x
   #define DIAGCONDPANIC(x,y)      if (x) panic y
   #else
   #define DIAGPANIC(x)
   #define DIAGCONDPANIC(x,y)
   #endif
   
   /* Global variables */
   
   struct  cgd_softc *cgd_softc;
   int     numcgd = 0;
   
   /* Utility Functions */
   
   #define CGDUNIT(x)              DISKUNIT(x)
   #define GETCGD_SOFTC(_cs, x)    if (!((_cs) = getcgd_softc(x))) return ENXIO
   
   static struct cgd_softc *
   getcgd_softc(dev_t dev)
   {
           int     unit = CGDUNIT(dev);
   
           DPRINTF_FOLLOW(("getcgd_softc(0x%x): unit = %d\n", dev, unit));
           if (unit >= numcgd)
                   return NULL;
           return &cgd_softc[unit];
   }
   
   /* The code */
   
   static void
   cgdsoftc_init(struct cgd_softc *cs, int num)
   {
           char    sbuf[DK_XNAME_SIZE];
   
           memset(cs, 0x0, sizeof(*cs));
           snprintf(sbuf, DK_XNAME_SIZE, "cgd%d", num);
           simple_lock_init(&cs->sc_slock);
           dk_sc_init(&cs->sc_dksc, cs, sbuf);
           cs->sc_dksc.sc_dkdev.dk_driver = &cgddkdriver;
           pseudo_disk_init(&cs->sc_dksc.sc_dkdev);
   }
   
   void
   cgdattach(int num)
   {
           int     i;
   
           DPRINTF_FOLLOW(("cgdattach(%d)\n", num));
           if (num <= 0) {
                   DIAGPANIC(("cgdattach: count <= 0"));
                   return;
           }
   
           cgd_softc = (void *)malloc(num * sizeof(*cgd_softc), M_DEVBUF, M_NOWAIT);
           if (!cgd_softc) {
                   printf("WARNING: unable to malloc(9) memory for crypt disks\n");
                   DIAGPANIC(("cgdattach: cannot malloc(9) enough memory"));
                   return;
           }
   
           numcgd = num;
           for (i=0; i<num; i++)
                   cgdsoftc_init(&cgd_softc[i], i);
   }
   
   static int
   cgdopen(dev_t dev, int flags, int fmt, struct lwp *l)
   {
           struct  cgd_softc *cs;
   
           DPRINTF_FOLLOW(("cgdopen(%d, %d)\n", dev, flags));
           GETCGD_SOFTC(cs, dev);
           return dk_open(di, &cs->sc_dksc, dev, flags, fmt, l);
   }
   
   static int
   cgdclose(dev_t dev, int flags, int fmt, struct lwp *l)
   {
           struct  cgd_softc *cs;
   
           DPRINTF_FOLLOW(("cgdclose(%d, %d)\n", dev, flags));
           GETCGD_SOFTC(cs, dev);
           return dk_close(di, &cs->sc_dksc, dev, flags, fmt, l);
   }
   
   static void
   cgdstrategy(struct buf *bp)
   {
           struct  cgd_softc *cs = getcgd_softc(bp->b_dev);
   
           DPRINTF_FOLLOW(("cgdstrategy(%p): b_bcount = %ld\n", bp,
               (long)bp->b_bcount));
           /* XXXrcd: Should we test for (cs != NULL)? */
           dk_strategy(di, &cs->sc_dksc, bp);
           return;
   }
   
   static int
   cgdsize(dev_t dev)
   {
           struct cgd_softc *cs = getcgd_softc(dev);
   
           DPRINTF_FOLLOW(("cgdsize(%d)\n", dev));
           if (!cs)
                   return -1;
           return dk_size(di, &cs->sc_dksc, dev);
   }
   
   /*
    * cgd_{get,put}data are functions that deal with getting a buffer
    * for the new encrypted data.  We have a buffer per device so that
    * we can ensure that we can always have a transaction in flight.
    * We use this buffer first so that we have one less piece of
    * malloc'ed data at any given point.
    */
   
   static void *
   cgd_getdata(struct dk_softc *dksc, unsigned long size)
   {
           struct  cgd_softc *cs =dksc->sc_osc;
           caddr_t data = NULL;
   
           simple_lock(&cs->sc_slock);
           if (cs->sc_data_used == 0) {
                   cs->sc_data_used = 1;
                   data = cs->sc_data;
           }
           simple_unlock(&cs->sc_slock);
   
           if (data)
                   return data;
   
           return malloc(size, M_DEVBUF, M_NOWAIT);
   }
   
   static void
   cgd_putdata(struct dk_softc *dksc, caddr_t data)
   {
           struct  cgd_softc *cs =dksc->sc_osc;
   
           if (data == cs->sc_data) {
                   simple_lock(&cs->sc_slock);
                   cs->sc_data_used = 0;
                   simple_unlock(&cs->sc_slock);
           } else {
                   free(data, M_DEVBUF);
           }
   }
   
   static int
   cgdstart(struct dk_softc *dksc, struct buf *bp)
   {
           struct  cgd_softc *cs = dksc->sc_osc;
           struct  buf *nbp;
           caddr_t addr;
           caddr_t newaddr;
           daddr_t bn;
   
           DPRINTF_FOLLOW(("cgdstart(%p, %p)\n", dksc, bp));
           disk_busy(&dksc->sc_dkdev); /* XXX: put in dksubr.c */
   
           bn = bp->b_rawblkno;
   
           /*
            * We attempt to allocate all of our resources up front, so that
            * we can fail quickly if they are unavailable.
            */
   
           nbp = getiobuf_nowait();
           if (nbp == NULL) {
                   disk_unbusy(&dksc->sc_dkdev, 0, (bp->b_flags & B_READ));
                   return -1;
           }
   
           /*
            * If we are writing, then we need to encrypt the outgoing
            * block into a new block of memory.  If we fail, then we
            * return an error and let the dksubr framework deal with it.
            */
           newaddr = addr = bp->b_data;
           if ((bp->b_flags & B_READ) == 0) {
                   newaddr = cgd_getdata(dksc, bp->b_bcount);
                   if (!newaddr) {
                           putiobuf(nbp);
                           disk_unbusy(&dksc->sc_dkdev, 0, (bp->b_flags & B_READ));
                           return -1;
                   }
                   cgd_cipher(cs, newaddr, addr, bp->b_bcount, bn,
                       DEV_BSIZE, CGD_CIPHER_ENCRYPT);
           }
   
           nbp->b_data = newaddr;
           nbp->b_flags = bp->b_flags | B_CALL;
           nbp->b_iodone = cgdiodone;
           nbp->b_proc = bp->b_proc;
           nbp->b_blkno = bn;
           nbp->b_vp = cs->sc_tvn;
           nbp->b_bcount = bp->b_bcount;
           nbp->b_private = bp;
   
           BIO_COPYPRIO(nbp, bp);
   
           if ((nbp->b_flags & B_READ) == 0) {
                   V_INCR_NUMOUTPUT(nbp->b_vp);
           }
           VOP_STRATEGY(cs->sc_tvn, nbp);
           return 0;
   }
   
   /* expected to be called at splbio() */
   static void
   cgdiodone(struct buf *nbp)
   {
           struct  buf *obp = nbp->b_private;
           struct  cgd_softc *cs = getcgd_softc(obp->b_dev);
           struct  dk_softc *dksc = &cs->sc_dksc;
   
           KDASSERT(cs);
   
           DPRINTF_FOLLOW(("cgdiodone(%p)\n", nbp));
           DPRINTF(CGDB_IO, ("cgdiodone: bp %p bcount %d resid %d\n",
               obp, obp->b_bcount, obp->b_resid));
           DPRINTF(CGDB_IO, (" dev 0x%x, nbp %p bn %" PRId64 " addr %p bcnt %d\n",
               nbp->b_dev, nbp, nbp->b_blkno, nbp->b_data,
               nbp->b_bcount));
           if (nbp->b_flags & B_ERROR) {
                   obp->b_flags |= B_ERROR;
                   obp->b_error  = nbp->b_error ? nbp->b_error : EIO;
   
                   printf("%s: error %d\n", dksc->sc_xname, obp->b_error);
           }
   
           /* Perform the decryption if we are reading.
            *
            * Note: use the blocknumber from nbp, since it is what
            *       we used to encrypt the blocks.
            */
   
           if (nbp->b_flags & B_READ)
                   cgd_cipher(cs, obp->b_data, obp->b_data, obp->b_bcount,
                       nbp->b_blkno, DEV_BSIZE, CGD_CIPHER_DECRYPT);
   
           /* If we allocated memory, free it now... */
           if (nbp->b_data != obp->b_data)
                   cgd_putdata(dksc, nbp->b_data);
   
           putiobuf(nbp);
   
           /* Request is complete for whatever reason */
           obp->b_resid = 0;
           if (obp->b_flags & B_ERROR)
                   obp->b_resid = obp->b_bcount;
           disk_unbusy(&dksc->sc_dkdev, obp->b_bcount - obp->b_resid,
               (obp->b_flags & B_READ));
           biodone(obp);
           dk_iodone(di, dksc);
   }
   
   /* XXX: we should probably put these into dksubr.c, mostly */
   static int
   cgdread(dev_t dev, struct uio *uio, int flags)
   {
           struct  cgd_softc *cs;
           struct  dk_softc *dksc;
   
           DPRINTF_FOLLOW(("cgdread(%d, %p, %d)\n", dev, uio, flags));
           GETCGD_SOFTC(cs, dev);
           dksc = &cs->sc_dksc;
           if ((dksc->sc_flags & DKF_INITED) == 0)
                   return ENXIO;
           return physio(cgdstrategy, NULL, dev, B_READ, minphys, uio);
   }
   
   /* XXX: we should probably put these into dksubr.c, mostly */
   static int
   cgdwrite(dev_t dev, struct uio *uio, int flags)
   {
           struct  cgd_softc *cs;
           struct  dk_softc *dksc;
   
           DPRINTF_FOLLOW(("cgdwrite(%d, %p, %d)\n", dev, uio, flags));
           GETCGD_SOFTC(cs, dev);
           dksc = &cs->sc_dksc;
           if ((dksc->sc_flags & DKF_INITED) == 0)
                   return ENXIO;
           return physio(cgdstrategy, NULL, dev, B_WRITE, minphys, uio);
   }
   
   static int
   cgdioctl(dev_t dev, u_long cmd, caddr_t data, int flag, struct lwp *l)
   {
           struct  cgd_softc *cs;
           struct  dk_softc *dksc;
           struct  disk *dk;
           int     ret;
           int     part = DISKPART(dev);
           int     pmask = 1 << part;
   
           DPRINTF_FOLLOW(("cgdioctl(%d, %ld, %p, %d, %p)\n",
               dev, cmd, data, flag, l));
           GETCGD_SOFTC(cs, dev);
           dksc = &cs->sc_dksc;
           dk = &dksc->sc_dkdev;
           switch (cmd) {
           case CGDIOCSET:
           case CGDIOCCLR:
                   if ((flag & FWRITE) == 0)
                           return EBADF;
           }
   
           switch (cmd) {
           case CGDIOCSET:
                   if (dksc->sc_flags & DKF_INITED)
                           ret = EBUSY;
                   else
                           ret = cgd_ioctl_set(cs, data, l);
                   break;
           case CGDIOCCLR:
                   if (!(dksc->sc_flags & DKF_INITED)) {
                           ret = ENXIO;
                           break;
                   }
                   if (DK_BUSY(&cs->sc_dksc, pmask)) {
                           ret = EBUSY;
                           break;
                   }
                   ret = cgd_ioctl_clr(cs, data, l);
                   break;
           default:
                   ret = dk_ioctl(di, dksc, dev, cmd, data, flag, l);
                   break;
           }
   
           return ret;
   }
   
   static int
   cgddump(dev_t dev, daddr_t blkno, caddr_t va, size_t size)
   {
           struct  cgd_softc *cs;
   
           DPRINTF_FOLLOW(("cgddump(%d, %" PRId64 ", %p, %lu)\n", dev, blkno, va,
               (unsigned long)size));
           GETCGD_SOFTC(cs, dev);
           return dk_dump(di, &cs->sc_dksc, dev, blkno, va, size);
   }
   
   /*
    * XXXrcd:
    *  for now we hardcode the maximum key length.
    */
   #define MAX_KEYSIZE     1024
   
   /* ARGSUSED */
   static int
   cgd_ioctl_set(struct cgd_softc *cs, void *data, struct lwp *l)
   {
           struct   cgd_ioctl *ci = data;
           struct   vnode *vp;
           int      ret;
           int      keybytes;                      /* key length in bytes */
           const char *cp;
           char     *inbuf;
   
           cp = ci->ci_disk;
           if ((ret = dk_lookup(cp, l, &vp, UIO_USERSPACE)) != 0)
                   return ret;
   
           inbuf = malloc(MAX_KEYSIZE, M_TEMP, M_WAITOK);
   
           if ((ret = cgdinit(cs, cp, vp, l)) != 0)
                   goto bail;
   
           (void)memset(inbuf, 0, MAX_KEYSIZE);
           ret = copyinstr(ci->ci_alg, inbuf, 256, NULL);
           if (ret)
                   goto bail;
           cs->sc_cfuncs = cryptfuncs_find(inbuf);
           if (!cs->sc_cfuncs) {
                   ret = EINVAL;
                   goto bail;
           }
   
           /* right now we only support encblkno, so hard-code it */
           (void)memset(inbuf, 0, sizeof(inbuf));
           ret = copyinstr(ci->ci_ivmethod, inbuf, MAX_KEYSIZE, NULL);
           if (ret)
                   goto bail;
           if (strcmp("encblkno", inbuf)) {
                   ret = EINVAL;
                   goto bail;
           }
   
           keybytes = ci->ci_keylen / 8 + 1;
           if (keybytes > MAX_KEYSIZE) {
                   ret = EINVAL;
                   goto bail;
           }
           (void)memset(inbuf, 0, MAX_KEYSIZE);
           ret = copyin(ci->ci_key, inbuf, keybytes);
           if (ret)
                   goto bail;
   
           cs->sc_cdata.cf_blocksize = ci->ci_blocksize;
           cs->sc_cdata.cf_mode = CGD_CIPHER_CBC_ENCBLKNO;
           cs->sc_cdata.cf_priv = cs->sc_cfuncs->cf_init(ci->ci_keylen, inbuf,
               &cs->sc_cdata.cf_blocksize);
           (void)memset(inbuf, 0, MAX_KEYSIZE);
           if (!cs->sc_cdata.cf_priv) {
                   printf("cgd: unable to initialize cipher\n");
                   ret = EINVAL;           /* XXX is this the right error? */
                   goto bail;
           }
           free(inbuf, M_TEMP);
   
           bufq_alloc(&cs->sc_dksc.sc_bufq, "fcfs", 0);
   
           cs->sc_data = malloc(MAXPHYS, M_DEVBUF, M_WAITOK);
           cs->sc_data_used = 0;
   
           cs->sc_dksc.sc_flags |= DKF_INITED;
   
           /* Attach the disk. */
           pseudo_disk_attach(&cs->sc_dksc.sc_dkdev);
   
           /* Try and read the disklabel. */
           dk_getdisklabel(di, &cs->sc_dksc, 0 /* XXX ? */);
   
           /* Discover wedges on this disk. */
           dkwedge_discover(&cs->sc_dksc.sc_dkdev);
   
           return 0;
   
   bail:
           free(inbuf, M_TEMP);
           (void)vn_close(vp, FREAD|FWRITE, l->l_cred, l);
           return ret;
   }
   
   /* ARGSUSED */
   static int
   cgd_ioctl_clr(struct cgd_softc *cs, void *data, struct lwp *l)
   {
           int     s;
   
           /* Delete all of our wedges. */
           dkwedge_delall(&cs->sc_dksc.sc_dkdev);
   
           /* Kill off any queued buffers. */
           s = splbio();
           bufq_drain(cs->sc_dksc.sc_bufq);
           splx(s);
           bufq_free(cs->sc_dksc.sc_bufq);
   
           (void)vn_close(cs->sc_tvn, FREAD|FWRITE, l->l_cred, l);
           cs->sc_cfuncs->cf_destroy(cs->sc_cdata.cf_priv);
           free(cs->sc_tpath, M_DEVBUF);
           free(cs->sc_data, M_DEVBUF);
           cs->sc_data_used = 0;
           cs->sc_dksc.sc_flags &= ~DKF_INITED;
           pseudo_disk_detach(&cs->sc_dksc.sc_dkdev);
   
           return 0;
   }
   
   static int
   cgdinit(struct cgd_softc *cs, const char *cpath, struct vnode *vp,
           struct lwp *l)
   {
           struct  dk_geom *pdg;
           struct  partinfo dpart;
           struct  vattr va;
           size_t  size;
           int     maxsecsize = 0;
           int     ret;
           char    *tmppath;
   
           cs->sc_dksc.sc_size = 0;
           cs->sc_tvn = vp;
           cs->sc_tpath = NULL;
   
           tmppath = malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
           ret = copyinstr(cpath, tmppath, MAXPATHLEN, &cs->sc_tpathlen);
           if (ret)
                   goto bail;
           cs->sc_tpath = malloc(cs->sc_tpathlen, M_DEVBUF, M_WAITOK);
           memcpy(cs->sc_tpath, tmppath, cs->sc_tpathlen);
   
           if ((ret = VOP_GETATTR(vp, &va, l->l_cred, l)) != 0)
                   goto bail;
   
           cs->sc_tdev = va.va_rdev;
   
           ret = VOP_IOCTL(vp, DIOCGPART, &dpart, FREAD, l->l_cred, l);
           if (ret)
                   goto bail;
   
           maxsecsize =
               ((dpart.disklab->d_secsize > maxsecsize) ?
               dpart.disklab->d_secsize : maxsecsize);
           size = dpart.part->p_size;
   
           if (!size) {
                   ret = ENODEV;
                   goto bail;
           }
   
           cs->sc_dksc.sc_size = size;
   
           /*
            * XXX here we should probe the underlying device.  If we
            *     are accessing a partition of type RAW_PART, then
            *     we should populate our initial geometry with the
            *     geometry that we discover from the device.
            */
           pdg = &cs->sc_dksc.sc_geom;
           pdg->pdg_secsize = DEV_BSIZE;
           pdg->pdg_ntracks = 1;
           pdg->pdg_nsectors = 1024 * (1024 / pdg->pdg_secsize);
           pdg->pdg_ncylinders = cs->sc_dksc.sc_size / pdg->pdg_nsectors;
   
   bail:
           free(tmppath, M_TEMP);
           if (ret && cs->sc_tpath)
                   free(cs->sc_tpath, M_DEVBUF);
           return ret;
   }
   
   /*
    * Our generic cipher entry point.  This takes care of the
    * IV mode and passes off the work to the specific cipher.
    * We implement here the IV method ``encrypted block
    * number''.
    *
    * For the encryption case, we accomplish this by setting
    * up a struct uio where the first iovec of the source is
    * the blocknumber and the first iovec of the dest is a
    * sink.  We then call the cipher with an IV of zero, and
    * the right thing happens.
    *
    * For the decryption case, we use the same basic mechanism
    * for symmetry, but we encrypt the block number in the
    * first iovec.
    *
    * We mainly do this to avoid requiring the definition of
    * an ECB mode.
    *
    * XXXrcd: for now we rely on our own crypto framework defined
    *         in dev/cgd_crypto.c.  This will change when we
    *         get a generic kernel crypto framework.
    */
   
   static void
   blkno2blkno_buf(char *sbuf, daddr_t blkno)
   {
           int     i;
   
           /* Set up the blkno in blkno_buf, here we do not care much
            * about the final layout of the information as long as we
            * can guarantee that each sector will have a different IV
            * and that the endianness of the machine will not affect
            * the representation that we have chosen.
            *
            * We choose this representation, because it does not rely
            * on the size of buf (which is the blocksize of the cipher),
            * but allows daddr_t to grow without breaking existing
            * disks.
            *
            * Note that blkno2blkno_buf does not take a size as input,
            * and hence must be called on a pre-zeroed buffer of length
            * greater than or equal to sizeof(daddr_t).
            */
           for (i=0; i < sizeof(daddr_t); i++) {
                   *sbuf++ = blkno & 0xff;
                   blkno >>= 8;
           }
   }
   
   static void
   cgd_cipher(struct cgd_softc *cs, caddr_t dst, caddr_t src,
              size_t len, daddr_t blkno, size_t secsize, int dir)
   {
           cfunc_cipher    *cipher = cs->sc_cfuncs->cf_cipher;
           struct uio      dstuio;
           struct uio      srcuio;
           struct iovec    dstiov[2];
           struct iovec    srciov[2];
           size_t          blocksize = cs->sc_cdata.cf_blocksize;
           char            sink[blocksize];
           char            zero_iv[blocksize];
           char            blkno_buf[blocksize];
   
           DPRINTF_FOLLOW(("cgd_cipher() dir=%d\n", dir));
   
           DIAGCONDPANIC(len % blocksize != 0,
               ("cgd_cipher: len %% blocksize != 0"));
   
           /* ensure that sizeof(daddr_t) <= blocksize (for encblkno IVing) */
           DIAGCONDPANIC(sizeof(daddr_t) > blocksize,
               ("cgd_cipher: sizeof(daddr_t) > blocksize"));
   
           memset(zero_iv, 0x0, sizeof(zero_iv));
   
           dstuio.uio_iov = dstiov;
           dstuio.uio_iovcnt = 2;
   
           srcuio.uio_iov = srciov;
           srcuio.uio_iovcnt = 2;
   
           dstiov[0].iov_base = sink;
           dstiov[0].iov_len  = blocksize;
           srciov[0].iov_base = blkno_buf;
           srciov[0].iov_len  = blocksize;
           dstiov[1].iov_len  = secsize;
           srciov[1].iov_len  = secsize;
   
           for (; len > 0; len -= secsize) {
                   dstiov[1].iov_base = dst;
                   srciov[1].iov_base = src;
   
                   memset(blkno_buf, 0x0, sizeof(blkno_buf));
                   blkno2blkno_buf(blkno_buf, blkno);
                   if (dir == CGD_CIPHER_DECRYPT) {
                           dstuio.uio_iovcnt = 1;
                           srcuio.uio_iovcnt = 1;
                           IFDEBUG(CGDB_CRYPTO, hexprint("step 0: blkno_buf",
                               blkno_buf, sizeof(blkno_buf)));
                           cipher(cs->sc_cdata.cf_priv, &dstuio, &srcuio,
                               zero_iv, CGD_CIPHER_ENCRYPT);
                           memcpy(blkno_buf, sink, blocksize);
                           dstuio.uio_iovcnt = 2;
                           srcuio.uio_iovcnt = 2;
                   }
   
                   IFDEBUG(CGDB_CRYPTO, hexprint("step 1: blkno_buf",
                       blkno_buf, sizeof(blkno_buf)));
                   cipher(cs->sc_cdata.cf_priv, &dstuio, &srcuio, zero_iv, dir);
                   IFDEBUG(CGDB_CRYPTO, hexprint("step 2: sink",
                       sink, sizeof(sink)));
   
                   dst += secsize;
                   src += secsize;
                   blkno++;
           }
   }
   
   #ifdef DEBUG
   static void
   hexprint(const char *start, void *buf, int len)
   {
           char    *c = buf;
   
           DIAGCONDPANIC(len < 0, ("hexprint: called with len < 0"));
           printf("%s: len=%06d 0x", start, len);
           while (len--)
                   printf("%02x", (unsigned) *c++);
   }
   #endif

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