[PATCH -tip] x86: trampoline_64.S - use predefined constants with simplification

Cyrill Gorcunov
2009-01-28T20:21:39Z

Impact: cleanup

We may use macros from processor-flags.h instead
of hardcoding bits. Actually it's not direct mapping
of old instructions with new ones -- BTS does change
CF flag while MOV does not. But i didn't find any
dependency on CF in this code.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
---

Please review

arch/x86/kernel/trampoline_64.S | 19 +++++++++----------
1 file changed, 9 insertions(+), 10 deletions(-)

Index: linux-2.6.git/arch/x86/kernel/trampoline_64.S
===================================================================
--- linux-2.6.git.orig/arch/x86/kernel/trampoline_64.S
+++ linux-2.6.git/arch/x86/kernel/trampoline_64.S
@@ -29,6 +29,7 @@
#include <asm/page.h>
#include <asm/msr.h>
#include <asm/segment.h>
+#include <asm/processor-flags.h>

.section .rodata, "a", @progbits

@@ -37,7 +38,7 @@
ENTRY(trampoline_data)
r_base = .
cli # We should be safe anyway
- wbinvd
+ wbinvd
mov %cs, %ax # Code and data in the same place
mov %ax, %ds
mov %ax, %es
@@ -73,9 +74,8 @@ r_base = .
lidtl tidt - r_base # load idt with 0, 0
lgdtl tgdt - r_base # load gdt with whatever is appropriate

- xor %ax, %ax
- inc %ax # protected mode (PE) bit
- lmsw %ax # into protected mode
+ mov $X86_CR0_PE, %ax # protected mode (PE) bit
+ lmsw %ax # into protected mode

# flush prefetch and jump to startup_32
ljmpl *(startup_32_vector - r_base)
@@ -86,9 +86,8 @@ startup_32:
movl $__KERNEL_DS, %eax # Initialize the %ds segment register
movl %eax, %ds

- xorl %eax, %eax
- btsl $5, %eax # Enable PAE mode
- movl %eax, %cr4
+ movl $X86_CR4_PAE, %eax
+ movl %eax, %cr4 # Enable PAE mode

# Setup trampoline 4 level pagetables
leal (trampoline_level4_pgt - r_base)(%esi), %eax
@@ -99,9 +98,9 @@ startup_32:
xorl %edx, %edx
wrmsr

- xorl %eax, %eax
- btsl $31, %eax # Enable paging and in turn activate Long Mode
- btsl $0, %eax # Enable protected mode
+ # Enable paging and in turn activate Long Mode
+ # Enable protected mode
+ movl $(X86_CR0_PG | X86_CR0_PE), %eax
movl %eax, %cr0

/*