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Subject[tip: x86/seves] x86/head/64: Load GDT after switch to virtual addresses
The following commit has been merged into the x86/seves branch of tip:

Commit-ID: e04b88336360e101329add0c05e5cb1cebae64fd
Gitweb: https://git.kernel.org/tip/e04b88336360e101329add0c05e5cb1cebae64fd
Author: Joerg Roedel <jroedel@suse.de>
AuthorDate: Mon, 07 Sep 2020 15:15:31 +02:00
Committer: Borislav Petkov <bp@suse.de>
CommitterDate: Mon, 07 Sep 2020 21:35:54 +02:00

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
---
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 2b2e916..03b03f2 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
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