x86/boot: Simplify kernel load address alignment check

commit a473314 upstream

We are using %rax as temporary register to check the kernel
address alignment. We don't really have to since the TEST
instruction does not clobber the destination operand.

Suggested-by: Brian Gerst <[email protected]>
Signed-off-by: Alexander Kuleshov <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Cc: Alexander Popov <[email protected]>
Cc: Andrey Ryabinin <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Denys Vlasenko <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
Signed-off-by: Srivatsa S. Bhat <[email protected]>
Reviewed-by: Matt Helsley (VMware) <[email protected]>
Reviewed-by: Alexey Makhalov <[email protected]>
Reviewed-by: Bo Gan <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: 0xAX

arch/x86/kernel/head_64.S

@@ -76,9 +76,7 @@ startup_64:
 	subq	$_text - __START_KERNEL_map, %rbp
 
 	/* Is the address not 2M aligned? */
-	movq	%rbp, %rax
-	andl	$~PMD_PAGE_MASK, %eax
-	testl	%eax, %eax
+	testl	$~PMD_PAGE_MASK, %ebp
 	jnz	bad_address
 
 	/*