x86/kexec: Make relocate_kernel_64.S objtool clean

Having fixed the biggest objtool issue in this file; fix up the rest
and remove the exception.
Suggested-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/20200324160924.202621656@infradead.org

arch/x86/kernel/Makefile

@@ -28,7 +28,6 @@ KASAN_SANITIZE_dumpstack_$(BITS).o			:= n
 KASAN_SANITIZE_stacktrace.o				:= n
 KASAN_SANITIZE_paravirt.o				:= n
 
-OBJECT_FILES_NON_STANDARD_relocate_kernel_$(BITS).o	:= y
 OBJECT_FILES_NON_STANDARD_test_nx.o			:= y
 OBJECT_FILES_NON_STANDARD_paravirt_patch.o		:= y
 

arch/x86/kernel/relocate_kernel_64.S

@@ -9,6 +9,8 @@
 #include <asm/kexec.h>
 #include <asm/processor-flags.h>
 #include <asm/pgtable_types.h>
+#include <asm/nospec-branch.h>
+#include <asm/unwind_hints.h>
 
 /*
  * Must be relocatable PIC code callable as a C function
@@ -39,6 +41,7 @@
 	.align PAGE_SIZE
 	.code64
 SYM_CODE_START_NOALIGN(relocate_kernel)
+	UNWIND_HINT_EMPTY
 	/*
 	 * %rdi indirection_page
 	 * %rsi page_list
@@ -105,6 +108,7 @@ SYM_CODE_START_NOALIGN(relocate_kernel)
 SYM_CODE_END(relocate_kernel)
 
 SYM_CODE_START_LOCAL_NOALIGN(identity_mapped)
+	UNWIND_HINT_EMPTY
 	/* set return address to 0 if not preserving context */
 	pushq	$0
 	/* store the start address on the stack */
@@ -192,6 +196,7 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_mapped)
 1:
 	popq	%rdx
 	leaq	PAGE_SIZE(%r10), %rsp
+	ANNOTATE_RETPOLINE_SAFE
 	call	*%rdx
 
 	/* get the re-entry point of the peer system */
@@ -209,6 +214,7 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_mapped)
 SYM_CODE_END(identity_mapped)
 
 SYM_CODE_START_LOCAL_NOALIGN(virtual_mapped)
+	UNWIND_HINT_EMPTY
 	movq	RSP(%r8), %rsp
 	movq	CR4(%r8), %rax
 	movq	%rax, %cr4
@@ -230,6 +236,7 @@ SYM_CODE_END(virtual_mapped)
 
 	/* Do the copies */
 SYM_CODE_START_LOCAL_NOALIGN(swap_pages)
+	UNWIND_HINT_EMPTY
 	movq	%rdi, %rcx 	/* Put the page_list in %rcx */
 	xorl	%edi, %edi
 	xorl	%esi, %esi