linux-kernel - [PATCH v2 6/7] x86/boot: GDT limit value should be size

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Date:   Sun,  2 Feb 2020 12:13:52 -0500
From:   Arvind Sankar <nivedita@...m.mit.edu>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, Ard Biesheuvel <ardb@...nel.org>
Cc:     linux-efi@...r.kernel.org, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 6/7] x86/boot: GDT limit value should be size - 1

The limit value for the GDTR should be such that adding it to the base
address gives the address of the last byte of the GDT, i.e. it should be
one less than the size, not the size.

Signed-off-by: Arvind Sankar <nivedita@...m.mit.edu>
---
 arch/x86/boot/compressed/head_64.S | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index 69cc6c68741e..c36e6156b6a3 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -624,12 +624,12 @@ SYM_FUNC_END(.Lno_longmode)
 
 	.data
 SYM_DATA_START_LOCAL(gdt64)
-	.word	gdt_end - gdt
+	.word	gdt_end - gdt - 1
 	.quad   0
 SYM_DATA_END(gdt64)
 	.balign	8
 SYM_DATA_START_LOCAL(gdt)
-	.word	gdt_end - gdt
+	.word	gdt_end - gdt - 1
 	.long	gdt
 	.word	0
 	.quad	0x00cf9a000000ffff	/* __KERNEL32_CS */
-- 
2.24.1