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

H. Peter Anvin
2007-11-05T03:59:25Z

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@zytor.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@zytor.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@zytor.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@zytor.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