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@alum.mit.edu>
Link: https://lore.kernel.org/r/20200202171353.3736319-7-nivedita@alum.mit.edu
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index 69cc6c6..c36e615 100644 (file)
--- 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 */