a465359a5d
During early dom0 boot, before xenstored is started any access to it
through /proc/xen/xenbus (or /dev/xen/xenbus) will wait until xenstored
is started. If that happens in script ordered to start before xenstored,
we have a deadlock. Prevent this by using `xenstore-ls -s` in dom0,
which will fail immediately when xenstored isn't running yet. This fail
isn't a problem, because when xenstored isn't running yet, surely device
isn't attached anywhere.
QubesOS/qubes-issues#1081
(cherry picked from commit cdbcb2eb55)
144 lines
3.5 KiB
Bash
Executable File
144 lines
3.5 KiB
Bash
Executable File
#!/bin/bash
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shopt -s nullglob
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export LC_CTYPE=en_US.UTF-8
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NAME=${DEVNAME#/dev/}
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DESC="`echo "${ID_MODEL} (${ID_FS_LABEL})" | iconv -f utf8 -t ascii//TRANSLIT`"
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SIZE=$[ $(cat /sys/$DEVPATH/size) * 512 ]
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MODE=w
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QDB_KEY="/qubes-block-devices/$NAME"
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xs_remove() {
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if [ "$QUBES_EXPOSED" == "1" ]; then
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qubesdb-rm "$QDB_KEY/"
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qubesdb-write /qubes-block-devices ''
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fi
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echo QUBES_EXPOSED=0
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}
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is_used() {
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local sys_devpath=$1
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# mounted
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if fgrep -q $(basename $sys_devpath) /proc/mounts; then
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return 0
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fi
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# part of other device-mapper
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if [ -n "`ls -A $sys_devpath/holders 2> /dev/null`" ]; then
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return 0
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fi
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# open device-mapper device
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if [ -f "$sys_devpath/dm/name" ] && \
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/sbin/dmsetup info "$(cat $sys_devpath/dm/name)" |\
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grep -q "^Open count:.*[1-9]"; then
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return 0
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fi
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return 1
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}
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# communicate with xenstored through socket in dom0
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# trying to access xenstore before xenstored is started, hang forever (in
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# non-killable state), so better fail ('-s' in VM if /proc/xen isn't mounted
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# yet) than hang dom0 boot
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if [ ! -r /proc/xen/capabilities ] || grep -q control_d /proc/xen/capabilities; then
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XENSTORE_LS="xenstore-ls -s"
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else
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XENSTORE_LS="xenstore-ls"
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fi
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is_attached() {
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dev_hex=$(stat -c %t:%T /dev/$(basename $1))
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$XENSTORE_LS backend/vbd | grep -q "physical-device = \"$dev_hex\""
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}
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# update info about parent devices, if any:
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if [ -f /sys$DEVPATH/partition ]; then
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parent=$(dirname $(readlink -f /sys$DEVPATH))
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udevadm trigger \
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--property-match=DEVPATH=/$(realpath --relative-to=/sys $parent)
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# if parent device is already attached, skip its partitions
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if is_attached $parent; then
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xs_remove
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exit 0
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fi
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fi
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# and underlying devices of device-mapper (if any)
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for dev in /sys$DEVPATH/slaves/*; do
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udevadm trigger \
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--property-match=DEVPATH=/$(realpath --relative-to=/sys $dev)
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done
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# then take care of this device:
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# device itself is already used
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if is_used /sys$DEVPATH; then
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xs_remove
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exit 0
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fi
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# or one of its partitions is used
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# or already attached (prevent attaching both device and its partition(s) at
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# the same time)
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for part in /sys$DEVPATH/$NAME*; do
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if [ -d $part ]; then
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if is_used $part; then
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xs_remove
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exit 0
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fi
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if is_attached $part; then
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xs_remove
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exit 0
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fi
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fi
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done
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# or "empty" loop device
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if [ "$MAJOR" -eq 7 -a ! -d /sys/$DEVPATH/loop ]; then
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xs_remove
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exit 0
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fi
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# ... and temporary devices used during VM startup
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if [[ "$NAME" = 'loop'* ]] && \
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[[ "`cat /sys/block/${NAME%p*}/loop/backing_file`" = \
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'/var/lib/qubes/'*'/volatile.img' ]]; then
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xs_remove
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exit 0
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fi
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# Check if device is read-only
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if [ "`cat /sys/$DEVPATH/ro`" -eq 1 ]; then
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MODE=r
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fi
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# Special case for CD
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if [ "$ID_TYPE" = "cd" ]; then
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if [ "$ID_CDROM_MEDIA" != "1" ]; then
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# Hide empty cdrom drive
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xs_remove
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exit 0
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fi
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MODE=r
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fi
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# Special description for loop devices
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if [ -d /sys/$DEVPATH/loop ]; then
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DESC=$(cat /sys/$DEVPATH/loop/backing_file)
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fi
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# and for device-mapper
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if [ -n "$DM_NAME" ]; then
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DESC="$DM_NAME"
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fi
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# The last one is meant to trigger watches
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qubesdb-write \
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"$QDB_KEY/desc" "$DESC" \
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"$QDB_KEY/size" "$SIZE" \
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"$QDB_KEY/mode" "$MODE" \
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/qubes-block-devices ''
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echo QUBES_EXPOSED=1
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# Make sure that block backend is loaded
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/sbin/modprobe xen-blkback 2> /dev/null || /sbin/modprobe blkbk
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