[PATCH] boot-directdisk: mount root by MBR disk signature for Linux 3.8+

[Jonathan Liu <net147@gmail.com>]

Signed-off-by: Jonathan Liu <net147@gmail.com>
---
 meta/classes/boot-directdisk.bbclass | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/meta/classes/boot-directdisk.bbclass b/meta/classes/boot-directdisk.bbclass
index 3169043..736bee0 100644
--- a/meta/classes/boot-directdisk.bbclass
+++ b/meta/classes/boot-directdisk.bbclass
@@ -23,7 +23,8 @@ do_bootdirectdisk[depends] += "dosfstools-native:do_populate_sysroot \
                                syslinux:do_populate_sysroot \
                                syslinux-native:do_populate_sysroot \
                                parted-native:do_populate_sysroot \
-                               mtools-native:do_populate_sysroot "
+                               mtools-native:do_populate_sysroot \
+                               util-linux-native:do_populate_sysroot "
 
 PACKAGES = " "
 EXCLUDE_FROM_WORLD = "1"
@@ -58,6 +59,22 @@ build_boot_dd() {
 	# done in blocks, thus the mod by 16 instead of 32.
 	BLOCKS=$(expr $BLOCKS + $(expr 16 - $(expr $BLOCKS % 16)))
 
+	KERNEL_VERSION=$(grep '^VERSION\s*=' ${STAGING_KERNEL_DIR}/Makefile | grep -o '[0-9]*$')
+	KERNEL_PATCHLEVEL=$(grep '^PATCHLEVEL\s*=' ${STAGING_KERNEL_DIR}/Makefile | grep -o '[0-9]*$')
+
+	rm -rf $IMAGE
+	dd if=/dev/zero of=$IMAGE bs=512 seek=1 count=0
+	parted $IMAGE mklabel msdos
+
+	# If using Linux 3.8 or later, mount root by MBR disk signature
+	if [[ $KERNEL_VERSION -eq 3 && $KERNEL_PATCHLEVEL -ge 8 ]] || [ $KERNEL_VERSION -gt 3 ]; then
+		# The disk signature generated by GNU Parted isn't really random, so regenerate it
+		echo -ne "$(uuidgen | sed 's/-//g;s/\(..\)/\\x&/g')" | dd of=$IMAGE bs=1 seek=440 count=4 conv=notrunc
+
+		DISK_SIGNATURE=$(hexdump -s 440 -n 4 -e '4 1 "%02x\n" "\n"' $IMAGE | tac | paste -sd '')
+		sed -i "s|\broot=[^ ]*|root=PARTUUID=$DISK_SIGNATURE-02|" $HDDDIR/syslinux.cfg
+	fi
+
 	mkdosfs -n ${BOOTDD_VOLUME_ID} -S 512 -C $HDDIMG $BLOCKS 
 	mcopy -i $HDDIMG -s $HDDDIR/* ::/
 
@@ -71,10 +88,8 @@ build_boot_dd() {
 	END3=`expr \( $ROOTFSBLOCKS \* 1024 \) + $END1`
 
 	echo $ROOTFSBLOCKS $TOTALSIZE $END1 $END2 $END3
-	rm -rf $IMAGE
 	dd if=/dev/zero of=$IMAGE bs=1024 seek=$TOTALSIZE count=1
 
-	parted $IMAGE mklabel msdos
 	parted $IMAGE mkpart primary fat16 0 ${END1}B
 	parted $IMAGE unit B mkpart primary ext2 ${END2}B ${END3}B
 	parted $IMAGE set 1 boot on 
-- 
1.8.2.3