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Subject[PATCH 10/10] x86/head_64: Simplify kernel load address alignment check
Date
From: Alexander Kuleshov <kuleshovmail@gmail.com>

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@gmail.com>
Signed-off-by: Alexander Kuleshov <kuleshovmail@gmail.com>
Cc: Alexander Popov <alpopov@ptsecurity.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1453531828-19291-1-git-send-email-kuleshovmail@gmail.com
Signed-off-by: Borislav Petkov <bp@suse.de>
---
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
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