x86/head/64: Load GDT after switch to virtual addresses

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>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/20200907131613.12703-31-joro@8bytes.org

diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 2b2e916..03b03f2 100644 (file)
--- 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