x86/mm/sme, objtool: Annotate indirect call in sme_encrypt_execute()

This is boot code and thus Spectre-safe: we run this _way_ before userspace
comes along to have a chance to poison our branch predictor.

Signed-off-by: Peter Zijlstra (Intel) <[e-mail]>
Acked-by: Thomas Gleixner <[e-mail]>
Acked-by: Josh Poimboeuf <[e-mail]>
Cc: Andy Lutomirski <[e-mail]>
Cc: Arjan van de Ven <[e-mail]>
Cc: Borislav Petkov <[e-mail]>
Cc: Borislav Petkov <[e-mail]>
Cc: Dan Williams <[e-mail]>
Cc: Dave Hansen <[e-mail]>
Cc: David Woodhouse <[e-mail]>
Cc: Greg Kroah-Hartman <[e-mail]>
Cc: Linus Torvalds <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Tom Lendacky <[e-mail]>
Signed-off-by: Ingo Molnar <[e-mail]>

arch/x86/mm/mem_encrypt_boot.S

···
 #include <asm/page.h>
 #include <asm/processor-flags.h>
 #include <asm/msr-index.h>
+#include <asm/nospec-branch.h>
 
 	.text
 	.code64
···
 	movq	%rax, %r8		/* Workarea encryption routine */
 	addq	$PAGE_SIZE, %r8		/* Workarea intermediate copy buffer */
 
+	ANNOTATE_RETPOLINE_SAFE
 	call	*%rax			/* Call the encryption routine */
 
 	pop	%r12