[lvc-project] [PATCH 03/16] x86/boot: Set cr0 to known state in trampoline

[Evgeniy Baskov]

Ensure WP bit to be set to prevent boot code from writing to
non-writable memory pages.

Signed-off-by: Evgeniy Baskov <baskov at ispras.ru>
---
 arch/x86/boot/compressed/head_64.S | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index d33f060900d2..5273367283b7 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -619,9 +619,8 @@ SYM_CODE_START(trampoline_32bit_src)
 	/* Set up new stack */
 	leal	TRAMPOLINE_32BIT_STACK_END(%ecx), %esp
 
-	/* Disable paging */
-	movl	%cr0, %eax
-	btrl	$X86_CR0_PG_BIT, %eax
+	/* Disable paging and setup CR0 */
+	movl	$(CR0_STATE & ~X86_CR0_PG), %eax
 	movl	%eax, %cr0
 
 	/* Check what paging mode we want to be in after the trampoline */
-- 
2.35.1