From 1f546e5f71af657ae46be3038f09d200ead3182f Mon Sep 17 00:00:00 2001
From: jsing <jsing@openbsd.org>
Date: Sat, 3 Jan 2015 15:50:50 +0000
Subject: [PATCH] Add support for creating a protective MBR for GPT.

Part of a diff by Markus Mueller, which was derived from Bitrig during
Google Summer of Code, with further tweaks by me.

ok krw@ miod@
---
 sbin/fdisk/fdisk.8 | 15 ++++++++++++---
 sbin/fdisk/fdisk.c | 17 ++++++++++++++---
 sbin/fdisk/mbr.c   | 25 +++++++++++++++++++++++--
 3 files changed, 49 insertions(+), 8 deletions(-)

diff --git a/sbin/fdisk/fdisk.8 b/sbin/fdisk/fdisk.8
index bb4f0bc5bbc..dc437808c6d 100644
--- a/sbin/fdisk/fdisk.8
+++ b/sbin/fdisk/fdisk.8
@@ -1,4 +1,4 @@
-.\"	$OpenBSD: fdisk.8,v 1.76 2014/03/06 17:39:23 jmc Exp $
+.\"	$OpenBSD: fdisk.8,v 1.77 2015/01/03 15:50:50 jsing Exp $
 .\"
 .\" Copyright (c) 1997 Tobias Weingartner
 .\" All rights reserved.
@@ -23,7 +23,7 @@
 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd $Mdocdate: March 6 2014 $
+.Dd $Mdocdate: January 3 2015 $
 .Dt FDISK 8
 .Os
 .Sh NAME
@@ -31,7 +31,7 @@
 .Nd MBR partition maintenance program
 .Sh SYNOPSIS
 .Nm fdisk
-.Op Fl eiuy
+.Op Fl egiuy
 .Oo
 .Fl c Ar cylinders
 .Fl h Ar heads
@@ -105,6 +105,12 @@ below, for more information.
 Specifies an alternate MBR template file.
 The default file is
 .Pa /usr/mdec/mbr .
+.It Fl g
+A protective MBR for GPT will be written to disk, instead of an MBR with an
+.Ox
+MBR partition.
+Only valid with
+.Fl i .
 .It Fl i
 Requests that the MBR partition data be re-initialized.
 In this mode,
@@ -120,6 +126,9 @@ In the default template, MBR partition number 3 will be configured as an
 MBR partition spanning the entire disk, except for a zone left at the start
 for booting.
 This mode is designed to initialize the MBR the very first time.
+If the
+.Fl g
+flag is also specified, a protective MBR for GPT will be created.
 .It Fl l Ar blocks
 Specify the number of blocks in the disk, and force the MBR to be in LBA
 mode only.
diff --git a/sbin/fdisk/fdisk.c b/sbin/fdisk/fdisk.c
index 70268385202..2a169bd4923 100644
--- a/sbin/fdisk/fdisk.c
+++ b/sbin/fdisk/fdisk.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: fdisk.c,v 1.63 2014/03/20 13:18:21 krw Exp $	*/
+/*	$OpenBSD: fdisk.c,v 1.64 2015/01/03 15:50:50 jsing Exp $	*/
 
 /*
  * Copyright (c) 1997 Tobias Weingartner
@@ -47,6 +47,7 @@ static unsigned char builtin_mbr[] = {
 #include "mbrcode.h"
 };
 
+int	g_flag;
 int	y_flag;
 
 static void
@@ -55,7 +56,8 @@ usage(void)
 	extern char * __progname;
 
 	fprintf(stderr, "usage: %s "
-	    "[-eiuy] [-c cylinders -h heads -s sectors] [-f mbrfile] [-l blocks] disk\n"
+	    "[-egiuy] [-c cylinders -h heads -s sectors] [-f mbrfile] "
+	    "[-l blocks] disk\n"
 	    "\t-i: initialize disk with virgin MBR\n"
 	    "\t-u: update MBR code, preserve partition table\n"
 	    "\t-e: edit MBRs on disk interactively\n"
@@ -63,6 +65,7 @@ usage(void)
 	    "\t-chs: specify disk geometry\n"
 	    "\t-l: specify LBA block count\n"
 	    "\t-y: do not ask questions\n"
+	    "\t-g: initialize disk with EFI/GPT partition, requires -i\n"
 	    "`disk' may be of the forms: sd0 or /dev/rsd0c.\n",
 	    __progname);
 	exit(1);
@@ -85,7 +88,7 @@ main(int argc, char *argv[])
 	struct mbr mbr;
 	struct dos_mbr dos_mbr;
 
-	while ((ch = getopt(argc, argv, "ieuf:c:h:s:l:y")) != -1) {
+	while ((ch = getopt(argc, argv, "ieguf:c:h:s:l:y")) != -1) {
 		const char *errstr;
 
 		switch(ch) {
@@ -117,6 +120,9 @@ main(int argc, char *argv[])
 			if (errstr)
 				errx(1, "Sector argument %s [1..63].", errstr);
 			break;
+		case 'g':
+			g_flag = 1;
+			break;
 		case 'l':
 			l_arg = strtonum(optarg, 64, UINT32_MAX, &errstr);
 			if (errstr)
@@ -141,6 +147,11 @@ main(int argc, char *argv[])
 	else
 		disk.name = argv[0];
 
+	if (g_flag != 0 && i_flag == 0) {
+		warnx("-g specified without -i");
+		usage();
+	}
+
 	/* Start with the disklabel geometry and get the sector size. */
 	DISK_getlabelgeometry(&disk);
 
diff --git a/sbin/fdisk/mbr.c b/sbin/fdisk/mbr.c
index 825b896deb6..bde9732bfd8 100644
--- a/sbin/fdisk/mbr.c
+++ b/sbin/fdisk/mbr.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: mbr.c,v 1.40 2014/05/21 15:55:19 krw Exp $	*/
+/*	$OpenBSD: mbr.c,v 1.41 2015/01/03 15:50:50 jsing Exp $	*/
 
 /*
  * Copyright (c) 1997 Tobias Weingartner
@@ -45,11 +45,32 @@
 #include "misc.h"
 #include "mbr.h"
 
+void
+MBR_init_GPT(struct disk *disk, struct mbr *mbr)
+{
+	/* Initialize a protective MBR for GPT. */
+	bzero(&mbr->part, sizeof(mbr->part));
+
+	/* Use whole disk, starting after MBR. */
+	mbr->part[0].id = DOSPTYP_EFI;
+	mbr->part[0].bs = 1;
+	mbr->part[0].ns = disk->size - 1;
+
+	/* Fix up start/length fields. */
+	PRT_fix_CHS(disk, &mbr->part[0]);
+}
+
 void
 MBR_init(struct disk *disk, struct mbr *mbr)
 {
-	daddr_t i;
+	extern int g_flag;
 	u_int64_t adj;
+	daddr_t i;
+
+	if (g_flag) {
+		MBR_init_GPT(disk, mbr);
+		return;
+	}
 
 	/* Fix up given mbr for this disk */
 	mbr->part[0].flag = 0;
-- 
2.20.1