From 987e90dc68863b34c6e37d54acc6ae971386547d Mon Sep 17 00:00:00 2001
From: xl222276 <none@none>
Date: Mon, 16 Jun 2008 21:30:50 -0700
Subject: 6613137 write_pmbr() puts garbage in first 446 bytes on disk

---
 usr/src/lib/libefi/common/rdwr_efi.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

(limited to 'usr/src/lib')

diff --git a/usr/src/lib/libefi/common/rdwr_efi.c b/usr/src/lib/libefi/common/rdwr_efi.c
index ddf96923c6..0f50628af0 100644
--- a/usr/src/lib/libefi/common/rdwr_efi.c
+++ b/usr/src/lib/libefi/common/rdwr_efi.c
@@ -540,7 +540,19 @@ write_pmbr(int fd, struct dk_gpt *vtoc)
 	uchar_t		*cp;
 	diskaddr_t	size_in_lba;
 
-	mb.signature = LE_16(MBB_MAGIC);
+	/*
+	 * Preserve any boot code and disk signature if the first block is
+	 * already an MBR.
+	 */
+	dk_ioc.dki_lba = 0;
+	dk_ioc.dki_length = sizeof (mb);
+	/* LINTED -- always longlong aligned */
+	dk_ioc.dki_data = (efi_gpt_t *)&mb;
+	if (efi_ioctl(fd, DKIOCGETEFI, &dk_ioc) == -1 ||
+	    mb.signature != LE_16(MBB_MAGIC)) {
+		bzero(&mb, sizeof (mb));
+		mb.signature = LE_16(MBB_MAGIC);
+	}
 	bzero(&mb.parts, sizeof (mb.parts));
 	cp = (uchar_t *)&mb.parts[0];
 	/* bootable or not */
-- 
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