diff mbox series

[v5,31/75] x86/head/64: Load GDT after switch to virtual addresses

Message ID 20200724160336.5435-32-joro@8bytes.org (mailing list archive)
State New, archived
Headers show
Series x86: SEV-ES Guest Support | expand

Commit Message

Joerg Roedel July 24, 2020, 4:02 p.m. UTC 
From: Joerg Roedel <jroedel@suse.de>

Load the GDT right after switching to virtual addresses to make sure
there is a defined GDT for exception handling.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
 arch/x86/kernel/head_64.S | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

Comments

Kees Cook July 24, 2020, 5:40 p.m. UTC | #1 
On Fri, Jul 24, 2020 at 06:02:52PM +0200, Joerg Roedel wrote:
> From: Joerg Roedel <jroedel@suse.de>
> 
> Load the GDT right after switching to virtual addresses to make sure
> there is a defined GDT for exception handling.
> 
> Signed-off-by: Joerg Roedel <jroedel@suse.de>

Reviewed-by: Kees Cook <keescook@chromium.org>
diff mbox series

Patch

diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 800053219054..f958d4e4ee08 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -166,6 +166,14 @@  SYM_CODE_START(secondary_startup_64)
 1:
 	UNWIND_HINT_EMPTY
 
+	/*
+	 * We must switch to a new descriptor in kernel space for the GDT
+	 * because soon the kernel won't have access anymore to the userspace
+	 * addresses where we're currently running on. We have to do that here
+	 * because in 32bit we couldn't load a 64bit linear address.
+	 */
+	lgdt	early_gdt_descr(%rip)
+
 	/* Check if nx is implemented */
 	movl	$0x80000001, %eax
 	cpuid
@@ -193,14 +201,6 @@  SYM_CODE_START(secondary_startup_64)
 	pushq $0
 	popfq
 
-	/*
-	 * We must switch to a new descriptor in kernel space for the GDT
-	 * because soon the kernel won't have access anymore to the userspace
-	 * addresses where we're currently running on. We have to do that here
-	 * because in 32bit we couldn't load a 64bit linear address.
-	 */
-	lgdt	early_gdt_descr(%rip)
-
 	/* set up data segments */
 	xorl %eax,%eax
 	movl %eax,%ds