Add a new flag to mkimg (-a num) to specify the active partition for

those partitioning schemes that have this concept. Implement it as an
override for mbr's setting 0x80 in the flags for the first partition
when we have boot code.

Differential Revision: https://reviews.freebsd.org/D4403

usr.bin/mkimg/mbr.c

@@ -92,7 +92,12 @@ mbr_write(lba_t imgsz __unused, void *bootcode)
 	TAILQ_FOREACH(part, &partlist, link) {
 		size = round_track(part->size);
 		dp = dpbase + part->index;
-		dp->dp_flag = (part->index == 0 && bootcode != NULL) ? 0x80 : 0;
+		if (active_partition != 0)
+			dp->dp_flag =
+			    (part->index + 1 == active_partition) ? 0x80 : 0;
+		else
+			dp->dp_flag =
+			    (part->index == 0 && bootcode != NULL) ? 0x80 : 0;
 		mbr_chs(&dp->dp_scyl, &dp->dp_shd, &dp->dp_ssect,
 		    part->block);
 		dp->dp_typ = ALIAS_TYPE2INT(part->type);

usr.bin/mkimg/mkimg.1

@@ -40,6 +40,7 @@
 .Op Fl c Ar capacity
 .Op Fl f Ar format
 .Op Fl o Ar outfile
+.Op Fl a Ar active
 .Op Fl v
 .Op Fl y
 .Op Fl s Ar scheme Op Fl p Ar partition ...
@@ -119,7 +120,7 @@ An empty partition table can be written to the disk when specifying a
 partitioning scheme with the
 .Fl s
 option, but without specifying any partitions.
-When the size required to for all the partitions is larger than the
+When the size required for all the partitions is larger than the
 given capacity, then the disk image will be larger than the capacity
 given.
 .Pp
@@ -139,6 +140,26 @@ utility will generate predictable values for Universally Unique Identifiers
 .Nm
 utility will create images that are identical.
 .Pp
+The
+.Ar active
+option marks a partition as active, if the partitioning
+scheme supports it.
+Currently, only the
+.Ar mbr
+scheme supports this concept.
+By default,
+.Nm
+will only mark the first partition as active when boot code is
+specified.
+Use the
+.Ar active
+option to override the active partition.
+The number specified corresponds to the number after the 's' in the
+partition's
+.Xr geom 8
+name.
+No partitions are marked active when the value is 0.
+.Pp
 A set of long options exist to query about the
 .Nm
 utility itself.

usr.bin/mkimg/mkimg.c

@@ -70,6 +70,7 @@ u_int nheads = 1;
 u_int nsecs = 1;
 u_int secsz = 512;
 u_int blksz = 0;
+uint32_t active_partition = 0;
 
 static void
 print_formats(int usage)
@@ -145,6 +146,7 @@ usage(const char *why)
 	fprintf(stderr, "\t--schemes\t-  list partition schemes\n");
 	fprintf(stderr, "\t--version\t-  show version information\n");
 	fputc('\n', stderr);
+	fprintf(stderr, "\t-a <num>\t-  mark num'th partion as active\n");
 	fprintf(stderr, "\t-b <file>\t-  file containing boot code\n");
 	fprintf(stderr, "\t-c <num>\t-  capacity (in bytes) of the disk\n");
 	fprintf(stderr, "\t-f <format>\n");
@@ -468,9 +470,14 @@ main(int argc, char *argv[])
 
 	bcfd = -1;
 	outfd = 1;	/* Write to stdout by default */
-	while ((c = getopt_long(argc, argv, "b:c:f:o:p:s:vyH:P:S:T:",
+	while ((c = getopt_long(argc, argv, "a:b:c:f:o:p:s:vyH:P:S:T:",
 	    longopts, NULL)) != -1) {
 		switch (c) {
+		case 'a':	/* ACTIVE PARTITION, if supported */
+			error = parse_uint32(&active_partition, 1, 100, optarg);
+			if (error)
+				errc(EX_DATAERR, error, "Partition ordinal");
+			break;
 		case 'b':	/* BOOT CODE */
 			if (bcfd != -1)
 				usage("multiple bootcode given");

usr.bin/mkimg/mkimg.h

@@ -59,6 +59,7 @@ extern u_int nheads;
 extern u_int nsecs;
 extern u_int secsz;	/* Logical block size. */
 extern u_int blksz;	/* Physical block size. */
+extern uint32_t active_partition;
 
 static inline lba_t
 round_block(lba_t n)