kexec: add machine_kexec_post_load()

It is the same as machine_kexec_prepare(), but is called after segments are
loaded. This way, can do processing work with already loaded relocation
segments. One such example is arm64: it has to have segments loaded in
order to create a page table, but it cannot do it during kexec time,
because at that time allocations won't be possible anymore.

Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Acked-by: Dave Young <dyoung@redhat.com>
Signed-off-by: Will Deacon <will@kernel.org>

kernel/kexec.c

@@ -159,6 +159,10 @@ static int do_kexec_load(unsigned long entry, unsigned long nr_segments,
 
 	kimage_terminate(image);
 
+	ret = machine_kexec_post_load(image);
+	if (ret)
+		goto out;
+
 	/* Install the new kernel and uninstall the old */
 	image = xchg(dest_image, image);