linux-kernel - [tip: x86/seves] x86/boot/compressed/64: Reload CS in startup

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Date:   Thu, 18 Mar 2021 19:34:34 -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>,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: x86/seves] x86/boot/compressed/64: Reload CS in startup_32

The following commit has been merged into the x86/seves branch of tip:

Commit-ID:     0c289ff81c24033777fab23019039f11e1449ba4
Gitweb:        https://git.kernel.org/tip/0c289ff81c24033777fab23019039f11e1449ba4
Author:        Joerg Roedel <jroedel@...e.de>
AuthorDate:    Wed, 10 Mar 2021 09:43:20 +01:00
Committer:     Borislav Petkov <bp@...e.de>
CommitterDate: Thu, 18 Mar 2021 16:44:43 +01:00

x86/boot/compressed/64: Reload CS in startup_32

Exception handling in the startup_32 boot path requires the CS
selector to be correctly set up. Reload it from the current GDT.

Signed-off-by: Joerg Roedel <jroedel@...e.de>
Signed-off-by: Borislav Petkov <bp@...e.de>
Link: https://lkml.kernel.org/r/20210312123824.306-4-joro@8bytes.org
---
 arch/x86/boot/compressed/head_64.S |  9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index e94874f..c59c80c 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -107,9 +107,16 @@ SYM_FUNC_START(startup_32)
 	movl	%eax, %gs
 	movl	%eax, %ss
 
-/* setup a stack and make sure cpu supports long mode. */
+	/* Setup a stack and load CS from current GDT */
 	leal	rva(boot_stack_end)(%ebp), %esp
 
+	pushl	$__KERNEL32_CS
+	leal	rva(1f)(%ebp), %eax
+	pushl	%eax
+	lretl
+1:
+
+	/* Make sure cpu supports long mode. */
 	call	verify_cpu
 	testl	%eax, %eax
 	jnz	.Lno_longmode