Support extended DOSpartitions.

Accept even suspicious partitions.

Moved most handling of the compatibility slice to dsopen().

Report i/o errors.

2 files changed, 362 insertions, 102 deletions

diff --git a/sys/i386/isa/diskslice_machdep.c b/sys/i386/isa/diskslice_machdep.c
index 91641f6..6b2af2b 100644
--- a/sys/i386/isa/diskslice_machdep.c
+++ b/sys/i386/isa/diskslice_machdep.c
@@ -35,17 +35,64 @@
  *
  *	from: @(#)ufs_disksubr.c	7.16 (Berkeley) 5/4/91
  *	from: ufs_disksubr.c,v 1.8 1994/06/07 01:21:39 phk Exp $
- *	$Id: diskslice_machdep.c,v 1.5 1995/02/21 08:37:09 bde Exp $
+ *	$Id: diskslice_machdep.c,v 1.6 1995/02/22 22:46:36 bde Exp $
  */
 
 #include <stddef.h>
 #include <sys/param.h>
 #include <sys/buf.h>
 #include <sys/disklabel.h>
+#define	DOSPTYP_EXTENDED	5
 #include <sys/diskslice.h>
 #include <sys/malloc.h>
+#include <sys/syslog.h>
 #include <sys/systm.h>
 
+#define TRACE(str)	do { if (dsi_debug) printf str; } while (0)
+
+static volatile u_char dsi_debug;
+
+static int check_part __P((char *sname, struct dos_partition *dp,
+			   u_long offset, int nsectors, int ntracks));
+static void extended __P((char *dname, dev_t dev, d_strategy_t *strat,
+			  struct disklabel *lp, struct diskslices *ssp,
+			  u_long ext_offset, u_long ext_size,
+			  u_long base_ext_offset, int nsectors, int ntracks));
+
+static int
+check_part(sname, dp, offset, nsectors, ntracks)
+	char	*sname;
+	struct dos_partition *dp;
+	u_long	offset;
+	int	nsectors;
+	int	ntracks;
+{
+	int	error;
+	u_long	esector;
+	u_long	esector1;
+	u_long	secpercyl;
+	u_long	ssector;
+	u_long	ssector1;
+
+	secpercyl = (u_long)nsectors * ntracks;
+	ssector = DPSECT(dp->dp_ssect) - 1 + dp->dp_shd * nsectors
+		  + DPCYL(dp->dp_scyl, dp->dp_ssect) * secpercyl;
+	ssector1 = offset + dp->dp_start;
+	esector = DPSECT(dp->dp_esect) - 1 + dp->dp_ehd * nsectors
+		  + DPCYL(dp->dp_ecyl, dp->dp_esect) * secpercyl;
+	esector1 = ssector1 + dp->dp_size - 1;
+	error = ssector == ssector1 && esector == esector1 ? 0 : EINVAL;
+	printf("%s: start %lu, end = %lu, size %lu%s\n",
+	       sname, ssector, esector, dp->dp_size, error ? "" : ": OK");
+	if (ssector != ssector1)
+		printf("%s: C/H/S start %lu != start %lu: invalid\n",
+		       sname, ssector, ssector1);
+	if (esector != esector1)
+		printf("%s: C/H/S end %lu != end %lu: invalid\n",
+		       sname, esector, esector1);
+	return (error);
+}
+
 int
 dsinit(dname, dev, strat, lp, sspp)
 	char	*dname;
@@ -56,6 +103,7 @@ dsinit(dname, dev, strat, lp, sspp)
 {
 	struct buf *bp;
 	u_char	*cp;
+	int	dospart;
 	struct dos_partition *dp;
 	struct dos_partition *dp0;
 	int	error;
@@ -92,6 +140,9 @@ dsinit(dname, dev, strat, lp, sspp)
 	bp->b_flags = B_BUSY | B_READ;
 	(*strat)(bp);
 	if (biowait(bp) != 0) {
+		diskerr(bp, dname, "error reading partition table",
+			LOG_PRINTF, 0, lp);
+		printf("\n");
 		error = EIO;
 		goto done;
 	}
@@ -99,6 +150,9 @@ dsinit(dname, dev, strat, lp, sspp)
 	/* Weakly verify it. */
 	cp = bp->b_un.b_addr;
 	if (cp[0x1FE] != 0x55 || cp[0x1FF] != 0xAA) {
+		diskerr(bp, dname, "invalid partition table",
+			LOG_PRINTF, 0, lp);
+		printf("\n");
 		error = EINVAL;
 		goto done;
 	}
@@ -113,10 +167,9 @@ dsinit(dname, dev, strat, lp, sspp)
 	max_nsectors = 0;
 	max_ntracks = 0;
 	dp0 = (struct dos_partition *)(cp + DOSPARTOFF);
-	for (dp = dp0, slice = BASE_SLICE; slice < BASE_SLICE + NDOSPART;
-	     dp++, slice++) {
-		int nsectors;
-		int ntracks;
+	for (dospart = 0, dp = dp0; dospart < NDOSPART; dospart++, dp++) {
+		int	nsectors;
+		int	ntracks;
 
 		max_ncyls = DPCYL(dp->dp_ecyl, dp->dp_esect);
 		if (max_ncyls < max_ncyls)
@@ -137,35 +190,22 @@ dsinit(dname, dev, strat, lp, sspp)
 	 * Check against d_secperunit if the latter is reliable.
 	 */
 	error = 0;
-	secpercyl = max_nsectors * max_ntracks;
-	for (dp = dp0, slice = BASE_SLICE; slice < BASE_SLICE + NDOSPART;
-	     dp++, slice++) {
-		u_long esector;
-		u_long esector1;
-		u_long ssector;
-
+	secpercyl = (u_long)max_nsectors * max_ntracks;
+	for (dospart = 0, dp = dp0; dospart < NDOSPART; dospart++, dp++) {
 		if (dp->dp_scyl == 0 && dp->dp_shd == 0 && dp->dp_ssect == 0
 		    && dp->dp_start == 0 && dp->dp_size == 0)
 			continue;
-		ssector = DPSECT(dp->dp_ssect) - 1 + dp->dp_shd * max_nsectors
-			  + DPCYL(dp->dp_scyl, dp->dp_ssect) * secpercyl;
-		esector = DPSECT(dp->dp_esect) - 1 + dp->dp_ehd * max_nsectors
-			  + DPCYL(dp->dp_ecyl, dp->dp_esect) * secpercyl;
-		esector1 = dp->dp_start + dp->dp_size - 1;
-		sname = dsname(dname, dkunit(dev), slice, RAW_PART, partname);
-		if (ssector != dp->dp_start || esector != esector1)
-			error = EINVAL;
-#if 1
-		else
-			printf("%s: start %lu, end = %lu, size %lu: OK\n",
-			       sname, ssector, esector, dp->dp_size);
-		if (ssector != dp->dp_start)
-			printf("%s: C/H/S start %lu != start %lu: invalid\n",
-			       sname, ssector, dp->dp_start);
-		if (esector != esector1)
-			printf("%s: C/H/S end %lu != end %lu: invalid\n",
-			       sname, esector, esector1);
-#endif
+		sname = dsname(dname, dkunit(dev), BASE_SLICE + dospart,
+			       RAW_PART, partname);
+
+		/*
+		 * Temporarily ignore errors from this check.  We could
+		 * simplify things by accepting the table eariler if we
+		 * always ignore errors here.  Perhaps we should always
+		 * accept the table if the magic is right but not let
+		 * bad entries affect the geometry.
+		 */
+		check_part(sname, dp, (u_long)0, max_nsectors, max_ntracks);
 	}
 	if (error != 0)
 		goto done;
@@ -192,40 +232,35 @@ dsinit(dname, dev, strat, lp, sspp)
 	 */
 	free(ssp, M_DEVBUF);
 	ssp = malloc(offsetof(struct diskslices, dss_slices)
-		     + (BASE_SLICE + NDOSPART) * sizeof *sp,
-		     M_DEVBUF, M_WAITOK);
+#define	MAX_SLICES_SUPPORTED	MAX_SLICES  /* was (BASE_SLICE + NDOSPART) */
+		     + MAX_SLICES_SUPPORTED * sizeof *sp, M_DEVBUF, M_WAITOK);
 	*sspp = ssp;
 	ssp->dss_first_bsd_slice = COMPATIBILITY_SLICE;
 	sp = &ssp->dss_slices[0];
-	bzero(sp, (BASE_SLICE + NDOSPART) * sizeof *sp);
+	bzero(sp, MAX_SLICES_SUPPORTED * sizeof *sp);
 	sp[WHOLE_DISK_SLICE].ds_size = lp->d_secperunit;
 
 	/* Initialize normal slices. */
 	sp += BASE_SLICE;
-	for (dp = dp0, slice = BASE_SLICE; slice < BASE_SLICE + NDOSPART;
-	     dp++, slice++, sp++) {
-		if (dp->dp_typ == DOSPTYP_386BSD
-		    && ssp->dss_first_bsd_slice == COMPATIBILITY_SLICE) {
-			ssp->dss_first_bsd_slice = slice;
-			ssp->dss_slices[COMPATIBILITY_SLICE].ds_offset
-			    = dp->dp_start;
-			ssp->dss_slices[COMPATIBILITY_SLICE].ds_size
-			    = dp->dp_size;
-		}
+	for (dospart = 0, dp = dp0; dospart < NDOSPART; dospart++, dp++, sp++) {
 		sp->ds_offset = dp->dp_start;
 		sp->ds_size = dp->dp_size;
+		sp->ds_type = dp->dp_typ;
 #if 0
-		lp->d_subtype |= (lp->d_subtype & 3)
-				 | (slice - BASE_SLICE) | DSTYPE_INDOSPART;
+		lp->d_subtype |= (lp->d_subtype & 3) | dospart
+				 | DSTYPE_INDOSPART;
 #endif
 	}
-
-	/*
-	 * We're not handling extended partitions yet, so there are always
-	 * BASE_SLICE + NDOSPART slices altogether.
-	 */
 	ssp->dss_nslices = BASE_SLICE + NDOSPART;
 
+	/* Handle extended partitions. */
+	sp -= NDOSPART;
+	for (dospart = 0; dospart < NDOSPART; dospart++, sp++)
+		if (sp->ds_type == DOSPTYP_EXTENDED)
+			extended(dname, bp->b_dev, strat, lp, ssp,
+				 sp->ds_offset, sp->ds_size, sp->ds_offset,
+				 max_nsectors, max_ntracks);
+
 done:
 	bp->b_flags = B_INVAL | B_AGE;
 	brelse(bp);
@@ -233,3 +268,98 @@ done:
 		error = 0;
 	return (error);
 }
+
+void
+extended(dname, dev, strat, lp, ssp, ext_offset, ext_size, base_ext_offset,
+	 nsectors, ntracks)
+	char	*dname;
+	dev_t	dev;
+	struct disklabel *lp;
+	d_strategy_t *strat;
+	struct diskslices *ssp;
+	u_long	ext_offset;
+	u_long	ext_size;
+	u_long	base_ext_offset;
+	int	nsectors;
+	int	ntracks;
+{
+	struct buf *bp;
+	u_char	*cp;
+	int	dospart;
+	struct dos_partition *dp;
+	int	end_slice;
+	u_long	ext_offsets[NDOSPART];
+	u_long	ext_sizes[NDOSPART];
+	char	partname[2];
+	int	slice;
+	char	*sname;
+	struct diskslice *sp;
+
+	/* Read extended boot record. */
+	bp = geteblk((int)lp->d_secsize);
+	bp->b_dev = dev;
+	bp->b_blkno = ext_offset;
+	bp->b_bcount = lp->d_secsize;
+	bp->b_flags = B_BUSY | B_READ;
+	(*strat)(bp);
+	if (biowait(bp) != 0) {
+		diskerr(bp, dname, "error reading extended partition table",
+			LOG_PRINTF, 0, lp);
+		printf("\n");
+		return;
+	}
+
+	/* Weakly verify it. */
+	cp = bp->b_un.b_addr;
+	if (cp[0x1FE] != 0x55 || cp[0x1FF] != 0xAA) {
+		diskerr(bp, dname, "invalid extended partition table",
+			LOG_PRINTF, 0, lp);
+		printf("\n");
+		return;
+	}
+
+	for (dospart = 0,
+	     dp = (struct dos_partition *)(bp->b_un.b_addr + DOSPARTOFF),
+	     slice = ssp->dss_nslices, sp = &ssp->dss_slices[slice];
+	     dospart < NDOSPART; dospart++, dp++) {
+		ext_sizes[dospart] = 0;
+		if (dp->dp_scyl == 0 && dp->dp_shd == 0 && dp->dp_ssect == 0
+		    && dp->dp_start == 0 && dp->dp_size == 0)
+			continue;
+		if (dp->dp_typ == DOSPTYP_EXTENDED) {
+			char buf[32];
+
+			sname = dsname(dname, dkunit(dev), WHOLE_DISK_SLICE,
+				       RAW_PART, partname);
+			strcpy(buf, sname);
+			if (strlen(buf) < sizeof buf - 11)
+				strcat(buf, "<extended>");
+			check_part(buf, dp, base_ext_offset, nsectors,
+				   ntracks);
+			ext_offsets[dospart] = base_ext_offset + dp->dp_start;
+			ext_sizes[dospart] = dp->dp_size;
+		} else {
+			sname = dsname(dname, dkunit(dev), slice, RAW_PART,
+				       partname);
+			check_part(sname, dp, ext_offset, nsectors, ntracks);
+			if (slice >= MAX_SLICES) {
+				printf("%s: too many slices\n", sname);
+				slice++;
+				continue;
+			}
+			sp->ds_offset = ext_offset + dp->dp_start;
+			sp->ds_size = dp->dp_size;
+			sp->ds_type = dp->dp_typ;
+			ssp->dss_nslices++;
+			slice++;
+			sp++;
+		}
+	}
+
+	/* If we found any more slices, recursively find all the subslices. */
+	for (dospart = 0; dospart < NDOSPART; dospart++)
+		if (ext_sizes[dospart] != 0)
+			extended(dname, dev, strat, lp, ssp,
+				 ext_offsets[dospart], ext_sizes[dospart],
+				 base_ext_offset, nsectors, ntracks);
+}
diff --git a/sys/kern/subr_diskmbr.c b/sys/kern/subr_diskmbr.c
index 91641f6..6b2af2b 100644
--- a/sys/kern/subr_diskmbr.c
+++ b/sys/kern/subr_diskmbr.c
@@ -35,17 +35,64 @@
  *
  *	from: @(#)ufs_disksubr.c	7.16 (Berkeley) 5/4/91
  *	from: ufs_disksubr.c,v 1.8 1994/06/07 01:21:39 phk Exp $
- *	$Id: diskslice_machdep.c,v 1.5 1995/02/21 08:37:09 bde Exp $
+ *	$Id: diskslice_machdep.c,v 1.6 1995/02/22 22:46:36 bde Exp $
  */
 
 #include <stddef.h>
 #include <sys/param.h>
 #include <sys/buf.h>
 #include <sys/disklabel.h>
+#define	DOSPTYP_EXTENDED	5
 #include <sys/diskslice.h>
 #include <sys/malloc.h>
+#include <sys/syslog.h>
 #include <sys/systm.h>
 
+#define TRACE(str)	do { if (dsi_debug) printf str; } while (0)
+
+static volatile u_char dsi_debug;
+
+static int check_part __P((char *sname, struct dos_partition *dp,
+			   u_long offset, int nsectors, int ntracks));
+static void extended __P((char *dname, dev_t dev, d_strategy_t *strat,
+			  struct disklabel *lp, struct diskslices *ssp,
+			  u_long ext_offset, u_long ext_size,
+			  u_long base_ext_offset, int nsectors, int ntracks));
+
+static int
+check_part(sname, dp, offset, nsectors, ntracks)
+	char	*sname;
+	struct dos_partition *dp;
+	u_long	offset;
+	int	nsectors;
+	int	ntracks;
+{
+	int	error;
+	u_long	esector;
+	u_long	esector1;
+	u_long	secpercyl;
+	u_long	ssector;
+	u_long	ssector1;
+
+	secpercyl = (u_long)nsectors * ntracks;
+	ssector = DPSECT(dp->dp_ssect) - 1 + dp->dp_shd * nsectors
+		  + DPCYL(dp->dp_scyl, dp->dp_ssect) * secpercyl;
+	ssector1 = offset + dp->dp_start;
+	esector = DPSECT(dp->dp_esect) - 1 + dp->dp_ehd * nsectors
+		  + DPCYL(dp->dp_ecyl, dp->dp_esect) * secpercyl;
+	esector1 = ssector1 + dp->dp_size - 1;
+	error = ssector == ssector1 && esector == esector1 ? 0 : EINVAL;
+	printf("%s: start %lu, end = %lu, size %lu%s\n",
+	       sname, ssector, esector, dp->dp_size, error ? "" : ": OK");
+	if (ssector != ssector1)
+		printf("%s: C/H/S start %lu != start %lu: invalid\n",
+		       sname, ssector, ssector1);
+	if (esector != esector1)
+		printf("%s: C/H/S end %lu != end %lu: invalid\n",
+		       sname, esector, esector1);
+	return (error);
+}
+
 int
 dsinit(dname, dev, strat, lp, sspp)
 	char	*dname;
@@ -56,6 +103,7 @@ dsinit(dname, dev, strat, lp, sspp)
 {
 	struct buf *bp;
 	u_char	*cp;
+	int	dospart;
 	struct dos_partition *dp;
 	struct dos_partition *dp0;
 	int	error;
@@ -92,6 +140,9 @@ dsinit(dname, dev, strat, lp, sspp)
 	bp->b_flags = B_BUSY | B_READ;
 	(*strat)(bp);
 	if (biowait(bp) != 0) {
+		diskerr(bp, dname, "error reading partition table",
+			LOG_PRINTF, 0, lp);
+		printf("\n");
 		error = EIO;
 		goto done;
 	}
@@ -99,6 +150,9 @@ dsinit(dname, dev, strat, lp, sspp)
 	/* Weakly verify it. */
 	cp = bp->b_un.b_addr;
 	if (cp[0x1FE] != 0x55 || cp[0x1FF] != 0xAA) {
+		diskerr(bp, dname, "invalid partition table",
+			LOG_PRINTF, 0, lp);
+		printf("\n");
 		error = EINVAL;
 		goto done;
 	}
@@ -113,10 +167,9 @@ dsinit(dname, dev, strat, lp, sspp)
 	max_nsectors = 0;
 	max_ntracks = 0;
 	dp0 = (struct dos_partition *)(cp + DOSPARTOFF);
-	for (dp = dp0, slice = BASE_SLICE; slice < BASE_SLICE + NDOSPART;
-	     dp++, slice++) {
-		int nsectors;
-		int ntracks;
+	for (dospart = 0, dp = dp0; dospart < NDOSPART; dospart++, dp++) {
+		int	nsectors;
+		int	ntracks;
 
 		max_ncyls = DPCYL(dp->dp_ecyl, dp->dp_esect);
 		if (max_ncyls < max_ncyls)
@@ -137,35 +190,22 @@ dsinit(dname, dev, strat, lp, sspp)
 	 * Check against d_secperunit if the latter is reliable.
 	 */
 	error = 0;
-	secpercyl = max_nsectors * max_ntracks;
-	for (dp = dp0, slice = BASE_SLICE; slice < BASE_SLICE + NDOSPART;
-	     dp++, slice++) {
-		u_long esector;
-		u_long esector1;
-		u_long ssector;
-
+	secpercyl = (u_long)max_nsectors * max_ntracks;
+	for (dospart = 0, dp = dp0; dospart < NDOSPART; dospart++, dp++) {
 		if (dp->dp_scyl == 0 && dp->dp_shd == 0 && dp->dp_ssect == 0
 		    && dp->dp_start == 0 && dp->dp_size == 0)
 			continue;
-		ssector = DPSECT(dp->dp_ssect) - 1 + dp->dp_shd * max_nsectors
-			  + DPCYL(dp->dp_scyl, dp->dp_ssect) * secpercyl;
-		esector = DPSECT(dp->dp_esect) - 1 + dp->dp_ehd * max_nsectors
-			  + DPCYL(dp->dp_ecyl, dp->dp_esect) * secpercyl;
-		esector1 = dp->dp_start + dp->dp_size - 1;
-		sname = dsname(dname, dkunit(dev), slice, RAW_PART, partname);
-		if (ssector != dp->dp_start || esector != esector1)
-			error = EINVAL;
-#if 1
-		else
-			printf("%s: start %lu, end = %lu, size %lu: OK\n",
-			       sname, ssector, esector, dp->dp_size);
-		if (ssector != dp->dp_start)
-			printf("%s: C/H/S start %lu != start %lu: invalid\n",
-			       sname, ssector, dp->dp_start);
-		if (esector != esector1)
-			printf("%s: C/H/S end %lu != end %lu: invalid\n",
-			       sname, esector, esector1);
-#endif
+		sname = dsname(dname, dkunit(dev), BASE_SLICE + dospart,
+			       RAW_PART, partname);
+
+		/*
+		 * Temporarily ignore errors from this check.  We could
+		 * simplify things by accepting the table eariler if we
+		 * always ignore errors here.  Perhaps we should always
+		 * accept the table if the magic is right but not let
+		 * bad entries affect the geometry.
+		 */
+		check_part(sname, dp, (u_long)0, max_nsectors, max_ntracks);
 	}
 	if (error != 0)
 		goto done;
@@ -192,40 +232,35 @@ dsinit(dname, dev, strat, lp, sspp)
 	 */
 	free(ssp, M_DEVBUF);
 	ssp = malloc(offsetof(struct diskslices, dss_slices)
-		     + (BASE_SLICE + NDOSPART) * sizeof *sp,
-		     M_DEVBUF, M_WAITOK);
+#define	MAX_SLICES_SUPPORTED	MAX_SLICES  /* was (BASE_SLICE + NDOSPART) */
+		     + MAX_SLICES_SUPPORTED * sizeof *sp, M_DEVBUF, M_WAITOK);
 	*sspp = ssp;
 	ssp->dss_first_bsd_slice = COMPATIBILITY_SLICE;
 	sp = &ssp->dss_slices[0];
-	bzero(sp, (BASE_SLICE + NDOSPART) * sizeof *sp);
+	bzero(sp, MAX_SLICES_SUPPORTED * sizeof *sp);
 	sp[WHOLE_DISK_SLICE].ds_size = lp->d_secperunit;
 
 	/* Initialize normal slices. */
 	sp += BASE_SLICE;
-	for (dp = dp0, slice = BASE_SLICE; slice < BASE_SLICE + NDOSPART;
-	     dp++, slice++, sp++) {
-		if (dp->dp_typ == DOSPTYP_386BSD
-		    && ssp->dss_first_bsd_slice == COMPATIBILITY_SLICE) {
-			ssp->dss_first_bsd_slice = slice;
-			ssp->dss_slices[COMPATIBILITY_SLICE].ds_offset
-			    = dp->dp_start;
-			ssp->dss_slices[COMPATIBILITY_SLICE].ds_size
-			    = dp->dp_size;
-		}
+	for (dospart = 0, dp = dp0; dospart < NDOSPART; dospart++, dp++, sp++) {
 		sp->ds_offset = dp->dp_start;
 		sp->ds_size = dp->dp_size;
+		sp->ds_type = dp->dp_typ;
 #if 0
-		lp->d_subtype |= (lp->d_subtype & 3)
-				 | (slice - BASE_SLICE) | DSTYPE_INDOSPART;
+		lp->d_subtype |= (lp->d_subtype & 3) | dospart
+				 | DSTYPE_INDOSPART;
 #endif
 	}
-
-	/*
-	 * We're not handling extended partitions yet, so there are always
-	 * BASE_SLICE + NDOSPART slices altogether.
-	 */
 	ssp->dss_nslices = BASE_SLICE + NDOSPART;
 
+	/* Handle extended partitions. */
+	sp -= NDOSPART;
+	for (dospart = 0; dospart < NDOSPART; dospart++, sp++)
+		if (sp->ds_type == DOSPTYP_EXTENDED)
+			extended(dname, bp->b_dev, strat, lp, ssp,
+				 sp->ds_offset, sp->ds_size, sp->ds_offset,
+				 max_nsectors, max_ntracks);
+
 done:
 	bp->b_flags = B_INVAL | B_AGE;
 	brelse(bp);
@@ -233,3 +268,98 @@ done:
 		error = 0;
 	return (error);
 }
+
+void
+extended(dname, dev, strat, lp, ssp, ext_offset, ext_size, base_ext_offset,
+	 nsectors, ntracks)
+	char	*dname;
+	dev_t	dev;
+	struct disklabel *lp;
+	d_strategy_t *strat;
+	struct diskslices *ssp;
+	u_long	ext_offset;
+	u_long	ext_size;
+	u_long	base_ext_offset;
+	int	nsectors;
+	int	ntracks;
+{
+	struct buf *bp;
+	u_char	*cp;
+	int	dospart;
+	struct dos_partition *dp;
+	int	end_slice;
+	u_long	ext_offsets[NDOSPART];
+	u_long	ext_sizes[NDOSPART];
+	char	partname[2];
+	int	slice;
+	char	*sname;
+	struct diskslice *sp;
+
+	/* Read extended boot record. */
+	bp = geteblk((int)lp->d_secsize);
+	bp->b_dev = dev;
+	bp->b_blkno = ext_offset;
+	bp->b_bcount = lp->d_secsize;
+	bp->b_flags = B_BUSY | B_READ;
+	(*strat)(bp);
+	if (biowait(bp) != 0) {
+		diskerr(bp, dname, "error reading extended partition table",
+			LOG_PRINTF, 0, lp);
+		printf("\n");
+		return;
+	}
+
+	/* Weakly verify it. */
+	cp = bp->b_un.b_addr;
+	if (cp[0x1FE] != 0x55 || cp[0x1FF] != 0xAA) {
+		diskerr(bp, dname, "invalid extended partition table",
+			LOG_PRINTF, 0, lp);
+		printf("\n");
+		return;
+	}
+
+	for (dospart = 0,
+	     dp = (struct dos_partition *)(bp->b_un.b_addr + DOSPARTOFF),
+	     slice = ssp->dss_nslices, sp = &ssp->dss_slices[slice];
+	     dospart < NDOSPART; dospart++, dp++) {
+		ext_sizes[dospart] = 0;
+		if (dp->dp_scyl == 0 && dp->dp_shd == 0 && dp->dp_ssect == 0
+		    && dp->dp_start == 0 && dp->dp_size == 0)
+			continue;
+		if (dp->dp_typ == DOSPTYP_EXTENDED) {
+			char buf[32];
+
+			sname = dsname(dname, dkunit(dev), WHOLE_DISK_SLICE,
+				       RAW_PART, partname);
+			strcpy(buf, sname);
+			if (strlen(buf) < sizeof buf - 11)
+				strcat(buf, "<extended>");
+			check_part(buf, dp, base_ext_offset, nsectors,
+				   ntracks);
+			ext_offsets[dospart] = base_ext_offset + dp->dp_start;
+			ext_sizes[dospart] = dp->dp_size;
+		} else {
+			sname = dsname(dname, dkunit(dev), slice, RAW_PART,
+				       partname);
+			check_part(sname, dp, ext_offset, nsectors, ntracks);
+			if (slice >= MAX_SLICES) {
+				printf("%s: too many slices\n", sname);
+				slice++;
+				continue;
+			}
+			sp->ds_offset = ext_offset + dp->dp_start;
+			sp->ds_size = dp->dp_size;
+			sp->ds_type = dp->dp_typ;
+			ssp->dss_nslices++;
+			slice++;
+			sp++;
+		}
+	}
+
+	/* If we found any more slices, recursively find all the subslices. */
+	for (dospart = 0; dospart < NDOSPART; dospart++)
+		if (ext_sizes[dospart] != 0)
+			extended(dname, dev, strat, lp, ssp,
+				 ext_offsets[dospart], ext_sizes[dospart],
+				 base_ext_offset, nsectors, ntracks);
+}