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Subject[PATCH 12/14] x86, boot: zero EFLAGS on 32 bits
Date
From: H. Peter Anvin <hpa@zytor.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@zytor.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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