[tip:x86/efi] x86, efi: Fix 32-bit EFI handover protocol entry point

[tip-bot for David Woodhouse]

Commit-ID:  f791620fa7517e1045742c475a7f005db9a634b8
Gitweb:     http://git.kernel.org/tip/f791620fa7517e1045742c475a7f005db9a634b8
Author:     David Woodhouse <David.Woodhouse@xxxxxxxxx>
AuthorDate: Mon, 7 Jan 2013 22:01:50 +0000
Committer:  H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
CommitDate: Sun, 27 Jan 2013 20:19:37 -0800

x86, efi: Fix 32-bit EFI handover protocol entry point

If the bootloader calls the EFI handover entry point as a standard function
call, then it'll have a return address on the stack. We need to pop that
before calling efi_main(), or the arguments will all be out of position on
the stack.

Signed-off-by: David Woodhouse <David.Woodhouse@xxxxxxxxx>
Cc: <stable@xxxxxxxxxx>
Link: http://lkml.kernel.org/r/1358513837.2397.247.camel@xxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
Cc: Matt Fleming <matt.fleming@xxxxxxxxx>
---
 arch/x86/boot/compressed/head_32.S | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
index aa4aaf1..ccb2f4a 100644
--- a/arch/x86/boot/compressed/head_32.S
+++ b/arch/x86/boot/compressed/head_32.S
@@ -50,8 +50,10 @@ ENTRY(startup_32)
 	pushl	%eax
 	pushl	%esi
 	pushl	%ecx
+	sub	$0x4, %esp
 
 	.org 0x30,0x90
+	add	$0x4, %esp
 	call	efi_main
 	cmpl	$0, %eax
 	movl	%eax, %esi
--
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