linux-kernel - [GIT PULL] x86 setup: correct booting on 486 (revised)

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Message-Id: <200711050358.lA53wlho003349@tazenda.hos.anvin.org>
Date:	Sun, 4 Nov 2007 19:58:47 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Mikael Petterson <mikpe@...uu.se>,
	Eric Biederman <ebiederm@...ssion.com>,
	Jeremy Fitzhardinge <jeremy@...p.org>
Subject: [GIT PULL] x86 setup: correct booting on 486 (revised)

Just for the record, I realized this patch could be done slightly
cleaner and cleaned it up accordingly.

  git://git.kernel.org/pub/scm/linux/kernel/git/hpa/linux-2.6-x86setup.git for-linus

H. Peter Anvin (2):
      x86 setup: add a near jump to serialize %cr0 on 386/486
      x86 setup: set %ebx == %ebp == %edi == 0 on protected mode entry

 arch/x86/boot/pmjump.S |    8 +++++---
 1 files changed, 5 insertions(+), 3 deletions(-)

commit 9f259cc59ba45b8db401d60be9700e275676fb15
Author: H. Peter Anvin <hpa@...or.com>
Date:   Sun Nov 4 17:54:31 2007 -0800

    x86 setup: set %ebx == %ebp == %edi == 0 on protected mode entry
    
    In accordance with the newly formalized 32-bit boot protocol, set
    %ebx == %ebp == %edi == 0 in order to support future extensions to the
    protocol.
    
    Signed-off-by: H. Peter Anvin <hpa@...or.com>

diff --git a/arch/x86/boot/pmjump.S b/arch/x86/boot/pmjump.S
index 26baeab..fa6bed1 100644
--- a/arch/x86/boot/pmjump.S
+++ b/arch/x86/boot/pmjump.S
@@ -28,11 +28,13 @@
  * void protected_mode_jump(u32 entrypoint, u32 bootparams);
  */
 protected_mode_jump:
-	xorl	%ebx, %ebx		# Flag to indicate this is a boot
 	movl	%edx, %esi		# Pointer to boot_params table
 	movl	%eax, 2f		# Patch ljmpl instruction
 
 	movw	$__BOOT_DS, %cx
+	xorl	%ebx, %ebx		# Per the 32-bit boot protocol
+	xorl	%ebp, %ebp		# Per the 32-bit boot protocol
+	xorl	%edi, %edi		# Per the 32-bit boot protocol
 
 	movl	%cr0, %edx
 	orb	$1, %dl			# Protected mode (PE) bit

commit 7ed192906a2144ebc8ca2925a85d27b9c5355668
Author: H. Peter Anvin <hpa@...or.com>
Date:   Sun Nov 4 17:50:12 2007 -0800

    x86 setup: add a near jump to serialize %cr0 on 386/486
    
    The 386 and 486 needs a jump immediately after setting %cr0 in order
    to serialize the pipeline.
    
    Signed-off-by: H. Peter Anvin <hpa@...or.com>

diff --git a/arch/x86/boot/pmjump.S b/arch/x86/boot/pmjump.S
index 2e55923..26baeab 100644
--- a/arch/x86/boot/pmjump.S
+++ b/arch/x86/boot/pmjump.S
@@ -31,14 +31,14 @@ protected_mode_jump:
 	xorl	%ebx, %ebx		# Flag to indicate this is a boot
 	movl	%edx, %esi		# Pointer to boot_params table
 	movl	%eax, 2f		# Patch ljmpl instruction
-	jmp	1f			# Short jump to flush instruction q.
 
-1:
 	movw	$__BOOT_DS, %cx
 
 	movl	%cr0, %edx
 	orb	$1, %dl			# Protected mode (PE) bit
 	movl	%edx, %cr0
+	jmp	1f			# Short jump to serialize on 386/486
+1:
 
 	movw	%cx, %ds
 	movw	%cx, %es
-
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