linux-kernel - [tip: x86/seves] x86/head/64: Load GDT after switch to virtual addresses

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Message-ID: <159972974006.20229.13724907581434195856.tip-bot2@tip-bot2>
Date:   Thu, 10 Sep 2020 09:22:20 -0000
From:   "tip-bot2 for Joerg Roedel" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Joerg Roedel <jroedel@...e.de>, Borislav Petkov <bp@...e.de>,
        Kees Cook <keescook@...omium.org>, x86 <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
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@...e.de>
AuthorDate:    Mon, 07 Sep 2020 15:15:31 +02:00
Committer:     Borislav Petkov <bp@...e.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@...e.de>
Signed-off-by: Borislav Petkov <bp@...e.de>
Reviewed-by: Kees Cook <keescook@...omium.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