Signed-off-by: Coiby Xu <[email protected]>

Based on the new kernel feature that dm-crypt keys can persist for the
kdump kernel [1], this patch which is adapted from [2]
1) ask the 1st kernel to save a copy of the LUKS volume keys
2) ask the kdump kernel to add the copy of the LUKS volume keys to
   specified keyring and then use --volume-key-keyring the unlock the
   LUKS device.

[1] https://github.com/coiby/linux/blob/dm_crypt_v15/Documentation/ABI/testing/crash_dm_crypt_keys
[2] https://lists.fedorahosted.org/archives/list/[email protected]/message/Y3KUSJQPN3JHUUC2FPIK7H4HTSX2TUCX/

Signed-off-by: Coiby Xu <[email protected]>

Since commit ffc1ec73b3 ("pid1: add ProtectSystem= as system-wide
configuration, and default it to true in the initrd"), systemd makes
/usr read-only by default and it will cause dracut to not wait for the
LUKS-encrypted devices to be unlocked,

    dracut-cmdline[296]: mv: inter-device move failed: '/tmp/294-daemon-reload.sh' to '/lib/dracut/hooks/initqueue/daemon-reload.sh'; unable to remove target: Read-only file syste

    dracut-cmdline[294]: /sbin/initqueue: line 71: /lib/dracut/hooks/initqueue/work: Read-only file system
    dracut-cmdline[221]: /lib/dracut-dev-lib.sh: line 118: /lib/dracut/hooks/initqueue/finished/devexists-\x2fdev\x2fmyvg\x2fluks_lv.sh: Read-only file system
    dracut-cmdline[221]: /lib/dracut-dev-lib.sh: line 103: /lib/dracut/hooks/emergency/80-\x2fdev\x2fmyvg\x2fluks_lv.sh: Read-only file system

Fix the above issue by making /usr writable.

Signed-off-by: Coiby Xu <[email protected]>

Send reuse command to /sys/kernel/crash_dm_crypt_keys [1] to reuse saved dm
crypt keys.

[1] https://github.com/coiby/linux/blob/dm_crypt_v15/Documentation/ABI/testing/crash_dm_crypt_keys

Signed-off-by: Coiby Xu <[email protected]>