Index: sys/boot/common/disk.c
===================================================================
--- sys/boot/common/disk.c
+++ sys/boot/common/disk.c
@@ -46,6 +46,7 @@
 struct open_disk {
 	struct ptable		*table;
 	off_t			mediasize;
+	off_t			entrysize;
 	u_int			sectorsize;
 	u_int			flags;
 	int			rcnt;
@@ -264,13 +265,28 @@
 }
 
 int
-disk_ioctl(struct disk_devdesc *dev, u_long cmd, void *buf)
+disk_ioctl(struct disk_devdesc *dev, u_long cmd, void *data)
 {
+	struct open_disk *od = dev->d_opendata;
 
-	if (dev->d_dev->dv_ioctl)
-		return ((*dev->d_dev->dv_ioctl)(dev->d_opendata, cmd, buf));
+	if (od == NULL)
+		return (ENOTTY);
 
-	return (ENXIO);
+	switch (cmd) {
+	case DIOCGSECTORSIZE:
+		*(u_int *)data = od->sectorsize;
+		break;
+	case DIOCGMEDIASIZE:
+		if (dev->d_offset == 0)
+			*(off_t *)data = od->mediasize;
+		else
+			*(off_t *)data = od->entrysize * od->sectorsize;
+		break;
+	default:
+		return (ENOTTY);
+	}
+
+	return (0);
 }
 
 int
@@ -315,6 +331,7 @@
 		}
 		dev->d_opendata = od;
 		od->rcnt = 0;
+		od->entrysize = 0;
 	}
 	od->mediasize = mediasize;
 	od->sectorsize = sectorsize;
@@ -330,14 +347,20 @@
 		rc = ENXIO;
 		goto out;
 	}
+	mediasize = ptable_getsize(od->table);
+	if (mediasize > od->mediasize) {
+		od->mediasize = mediasize;
+	}
 opened:
 	rc = 0;
 	if (ptable_gettype(od->table) == PTABLE_BSD &&
 	    partition >= 0) {
 		/* It doesn't matter what value has d_slice */
 		rc = ptable_getpart(od->table, &part, partition);
-		if (rc == 0)
+		if (rc == 0) {
 			dev->d_offset = part.start;
+			od->entrysize = part.end - part.start + 1;
+		}
 	} else if (slice >= 0) {
 		/* Try to get information about partition */
 		if (slice == 0)
@@ -347,6 +370,7 @@
 		if (rc != 0) /* Partition doesn't exist */
 			goto out;
 		dev->d_offset = part.start;
+		od->entrysize = part.end - part.start + 1;
 		slice = part.index;
 		if (ptable_gettype(od->table) == PTABLE_GPT) {
 			partition = 255;
@@ -389,6 +413,7 @@
 		if (rc != 0)
 			goto out;
 		dev->d_offset += part.start;
+		od->entrysize = part.end - part.start + 1;
 	}
 out:
 	if (table != NULL)
Index: sys/boot/common/part.h
===================================================================
--- sys/boot/common/part.h
+++ sys/boot/common/part.h
@@ -70,6 +70,7 @@
     diskread_t *dread);
 void ptable_close(struct ptable *table);
 enum ptable_type ptable_gettype(const struct ptable *table);
+uint64_t ptable_getsize(const struct ptable *table);
 
 int ptable_getpart(const struct ptable *table, struct ptable_entry *part,
     int index);
Index: sys/boot/common/part.c
===================================================================
--- sys/boot/common/part.c
+++ sys/boot/common/part.c
@@ -310,6 +310,11 @@
 	DEBUG("GPT detected");
 	size = MIN(hdr.hdr_entries * hdr.hdr_entsz,
 	    MAXTBLSZ * table->sectorsize);
+
+	/* Reset table->sectors if needed. */
+	if (hdr.hdr_lba_alt + 1 > table->sectors)
+		table->sectors = hdr.hdr_lba_alt + 1;
+
 	for (i = 0; i < size / hdr.hdr_entsz; i++) {
 		ent = (struct gpt_ent *)(tbl + i * hdr.hdr_entsz);
 		if (uuid_equal(&ent->ent_type, &gpt_uuid_unused, NULL))
@@ -734,6 +739,13 @@
 	return (table->type);
 }
 
+uint64_t
+ptable_getsize(const struct ptable *table)
+{
+
+	return (table->sectors * table->sectorsize);
+}
+
 int
 ptable_getpart(const struct ptable *table, struct ptable_entry *part, int index)
 {