Fix up the GPT in the initramfs

This adjusts the GPT in the initramfs, and (obviously) requires the
previous commit.

Fixes: QubesOS/qubes-issues#4974

dracut/full-dmroot/module-setup.sh

@@ -18,5 +18,6 @@ install() {
     inst_multiple \
         sfdisk \
         swapon \
-        mkswap
+        mkswap \
+        gptfix
 }

dracut/full-dmroot/qubes_cow_setup.sh

@@ -54,19 +54,32 @@ modprobe xenblk || modprobe xen-blkfront || warn "Qubes: Cannot load Xen Block F
 
 log_begin "Waiting for /dev/xvda* devices..."
 udevadm settle --exit-if-exists=/dev/xvda
-log_end
 
 # prefer partition if exists
-if [ -b /dev/xvda1 ]; then
+if /usr/sbin/gptfix fix /dev/xvda; then
+    udevadm settle --exit-if-exists=/dev/xvda1
     if [ -e "/dev/disk/by-partlabel/Root\\x20filesystem" ]; then
         ROOT_DEV=$(readlink "/dev/disk/by-partlabel/Root\\x20filesystem")
         ROOT_DEV=${ROOT_DEV##*/}
     else
         ROOT_DEV=xvda3
     fi
+    if ! [ -b "/dev/$ROOT_DEV" ]; then udevadm settle "--exit-if-exists=/dev/$ROOT_DEV"; fi
 else
-    ROOT_DEV=xvda
+    status=$?
+    case $status in
+    (1|2) # EIO, ENOMEM, or bug.  Fatal.
+        die 'Fatal error reading partition table';;
+    (4|5|8) # Bad or no partition table
+        ROOT_DEV=xvda;;
+    (*)
+        # TODO: what should be done?
+        # This is things like:
+        # - "Partition table not supported"
+        die 'GPT cannot be fixed';;
+    esac
 fi
+log_end
 
 SWAP_SIZE_GiB=1
 SWAP_SIZE_512B=$(( SWAP_SIZE_GiB * 1024 * 1024 * 2 ))

dracut/simple/init.sh

@@ -28,22 +28,33 @@ die() {
 
 echo "Waiting for /dev/xvda* devices..."
 while ! [ -e /dev/xvda ]; do sleep 0.1; done
-
-# prefer partition if exists
-if [ -b /dev/xvda1 ]; then
+# Fix up partition tables
+if /usr/sbin/gptfix fix /dev/xvda; then
+    while ! [ -e /dev/xvda1 ]; do sleep 0.01; done
     if [ -d /dev/disk/by-partlabel ]; then
         ROOT_DEV=$(readlink "/dev/disk/by-partlabel/Root\\x20filesystem")
         ROOT_DEV=${ROOT_DEV##*/}
     else
-        ROOT_DEV=$(grep -l "PARTNAME=Root filesystem" /sys/block/xvda/xvda*/uevent |\
+        ROOT_DEV=$(grep -l "PARTNAME=Root filesystem" /sys/block/xvda/xvda*/uevent |
             grep -o "xvda[0-9]")
     fi
     if [ -z "$ROOT_DEV" ]; then
         # fallback to third partition
         ROOT_DEV=xvda3
     fi
+    while ! [ -b "/dev/$ROOT_DEV" ]; do sleep 0.01; done
 else
-    ROOT_DEV=xvda
+    case $? in
+    (1|2) # EIO, ENOMEM, or bug.  Fatal.
+        die 'Fatal error reading partition table';;
+    (4|5|8) # Bad or no partition table
+        ROOT_DEV=xvda;;
+    (*)
+        # TODO: what should be done?
+        # - "Partition table not supported"
+        # - "Disk truncated"
+        die 'GPT cannot be fixed or disk truncated';;
+    esac
 fi
 
 SWAP_SIZE_GiB=1

dracut/simple/module-setup.sh

@@ -29,5 +29,6 @@ install() {
         rmdir \
         sleep \
         sfdisk \
-        mkswap
+        mkswap \
+        gptfix
 }