kexec_load: Disable at runtime if the kernel is locked down

kexec_load: Disable at runtime if the kernel is locked down

The kexec_load() syscall permits the loading and execution of arbitrary
code in ring 0, which is something that lock-down is meant to prevent. It
makes sense to disable kexec_load() in this situation.

This does not affect kexec_file_load() syscall which can check for a
signature on the image to be booted.

Signed-off-by: Matthew Garrett <mjg59@srcf.ucam.org>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Dave Young <dyoung@redhat.com>
Reviewed-by: "Lee, Chun-Yi" <jlee@suse.com>
Reviewed-by: James Morris <james.l.morris@oracle.com>
cc: kexec@lists.infradead.org

Gbp-Pq: Topic features/all/lockdown
Gbp-Pq: Name 0006-kexec_load-Disable-at-runtime-if-the-kernel-is-locke.patch