[PATCH v7 30/72] x86/head/64: Load GDT after switch to virtual addresses

Joerg Roedel
2020-09-07T13:15:31Z

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 at suse.de>
Reviewed-by: Kees Cook <keescook at chromium.org>
---
 arch/x86/kernel/head_64.S | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 2b2e91627221..03b03f266dc1 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -158,6 +158,14 @@ 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
@@ -185,14 +193,6 @@ 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
--
2.28.0