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

H. Peter Anvin
2007-11-05T02:16:49Z

Hi Linus; please pull:

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 | 12 ++++++++----
1 files changed, 8 insertions(+), 4 deletions(-)

commit 142a92e61f9c405a114cb2bfaf3ce3f537a48a89
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 18732f7..0d24e96 100644
--- a/arch/x86/boot/pmjump.S
+++ b/arch/x86/boot/pmjump.S
@@ -28,13 +28,15 @@
* 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, 3f # Patch ljmpl instruction
jmp 1f # Short jump to flush instruction q.
1:

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 ad676d0fdf2e59ccc28ee9f6f9593ff14a3d8a5a
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..18732f7 100644
--- a/arch/x86/boot/pmjump.S
+++ b/arch/x86/boot/pmjump.S
@@ -30,15 +30,17 @@
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
+ movl %eax, 3f # 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 2f # Short jump to serialize on 386/486
+2:

movw %cx, %ds
movw %cx, %es
@@ -48,7 +50,7 @@ protected_mode_jump:

# Jump to the 32-bit entrypoint
.byte 0x66, 0xea # ljmpl opcode
-2: .long 0 # offset
+3: .long 0 # offset
.word __BOOT_CS # segment

.size protected_mode_jump, .-protected_mode_jump