linux-kernel - [PATCH 12/14] x86, boot: zero EFLAGS on 32 bits

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Message-Id: <1241735222-6640-13-git-send-email-hpa@linux.intel.com>
Date:	Thu,  7 May 2009 15:27:00 -0700
From:	"H. Peter Anvin" <hpa@...ux.intel.com>
To:	linux-kernel@...r.kernel.org
Cc:	vgoyal@...hat.com, hbabu@...ibm.com, kexec@...ts.infradead.org,
	ying.huang@...el.com, mingo@...e.hu, tglx@...utronix.de,
	ebiederm@...ssion.com, sam@...nborg.org,
	"H. Peter Anvin" <hpa@...or.com>
Subject: [PATCH 12/14] x86, boot: zero EFLAGS on 32 bits

From: H. Peter Anvin <hpa@...or.com>

The 64-bit code already clears EFLAGS as soon as it has a stack.  This
seems like a reasonable precaution, so do it on 32 bits as well.

[ Impact: extra paranoia ]

Signed-off-by: H. Peter Anvin <hpa@...or.com>
---
 arch/x86/boot/compressed/head_32.S |   10 ++++++++--
 1 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
index 47636b3..48c2047 100644
--- a/arch/x86/boot/compressed/head_32.S
+++ b/arch/x86/boot/compressed/head_32.S
@@ -12,9 +12,9 @@
  * the page directory. [According to comments etc elsewhere on a compressed
  * kernel it will end up at 0x1000 + 1Mb I hope so as I assume this. - AC]
  *
- * Page 0 is deliberately kept safe, since System Management Mode code in 
+ * Page 0 is deliberately kept safe, since System Management Mode code in
  * laptops may need to access the BIOS data stored there.  This is also
- * useful for future device drivers that either access the BIOS via VM86 
+ * useful for future device drivers that either access the BIOS via VM86
  * mode.
  */
 
@@ -84,6 +84,12 @@ ENTRY(startup_32)
 	leal boot_stack_end(%ebx), %esp
 
 /*
+ * Zero EFLAGS
+ */
+	pushl $0
+	popfl
+
+/*
  * Copy the compressed kernel to the end of our buffer
  * where decompression in place becomes safe.
  */
-- 
1.6.0.6

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