[PATCH 10/10] x86/head_64: Simplify kernel load address alignment check

[Borislav Petkov]

From: Alexander Kuleshov <kuleshovmail@xxxxxxxxx>

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 <brgerst@xxxxxxxxx>
Signed-off-by: Alexander Kuleshov <kuleshovmail@xxxxxxxxx>
Cc: Alexander Popov <alpopov@xxxxxxxxxxxxxx>
Cc: Andrey Ryabinin <ryabinin.a.a@xxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1453531828-19291-1-git-send-email-kuleshovmail@xxxxxxxxx
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
---
 arch/x86/kernel/head_64.S | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index ffdc0e860390..7c21029cb733 100644
--- a/arch/x86/kernel/head_64.S
+++ b/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
 
 	/*
-- 
2.3.5