linux-kernel - [PATCH v2 2/5] x86/pvh: Use correct size value in GDT descriptor

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Message-ID: <20240930071513.909462-9-ardb+git@google.com>
Date: Mon, 30 Sep 2024 09:15:16 +0200
From: Ard Biesheuvel <ardb+git@...gle.com>
To: linux-kernel@...r.kernel.org
Cc: Ard Biesheuvel <ardb@...nel.org>, Jason Andryuk <jason.andryuk@....com>, 
	Juergen Gross <jgross@...e.com>, Boris Ostrovsky <boris.ostrovsky@...cle.com>, x86@...nel.org, 
	xen-devel@...ts.xenproject.org
Subject: [PATCH v2 2/5] x86/pvh: Use correct size value in GDT descriptor

From: Ard Biesheuvel <ardb@...nel.org>

The limit field in a GDT descriptor is an inclusive bound, and therefore
one less than the size of the covered range.

Reviewed-by: Jason Andryuk <jason.andryuk@....com>
Tested-by: Jason Andryuk <jason.andryuk@....com>
Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
---
 arch/x86/platform/pvh/head.S | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/platform/pvh/head.S b/arch/x86/platform/pvh/head.S
index ce4fd8d33da4..5a196fb3ebd8 100644
--- a/arch/x86/platform/pvh/head.S
+++ b/arch/x86/platform/pvh/head.S
@@ -224,7 +224,7 @@ SYM_CODE_END(pvh_start_xen)
 	.section ".init.data","aw"
 	.balign 8
 SYM_DATA_START_LOCAL(gdt)
-	.word gdt_end - gdt_start
+	.word gdt_end - gdt_start - 1
 	.long _pa(gdt_start) /* x86-64 will overwrite if relocated. */
 	.word 0
 SYM_DATA_END(gdt)
-- 
2.46.1.824.gd892dcdcdd-goog