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x86/boot/compressed/64: Make sure we have a 32-bit code segment 

When kernel starts in 64-bit mode we inherit the GDT from the bootloader.
It may cause a problem if the GDT doesn't have a 32-bit code segment
where we expect it to be.

Load our own GDT with known segments.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20180312100246.89175-2-kirill.shutemov@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Kirill A. Shutemov 2018-03-12 13:02:43 +03:00 committed by Ingo Molnar
parent a5b162b2ec
commit 7beebaccd5
1 changed files with 10 additions and 0 deletions
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10
arch/x86/boot/compressed/head_64.S
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@ -313,6 +313,11 @@ ENTRY(startup_64)
* first.
*/
/* Make sure we have GDT with 32-bit code segment */
leaq gdt(%rip), %rax
movq %rax, gdt64+2(%rip)
lgdt gdt64(%rip)
/*
* paging_prepare() sets up the trampoline and checks if we need to
* enable 5-level paging.
@ -547,6 +552,11 @@ no_longmode:
#include "../../kernel/verify_cpu.S"
.data
gdt64:
.word gdt_end - gdt
.long 0
.word 0
.quad 0
gdt:
.word gdt_end - gdt
.long gdt