Commit 7beebacc authored Mar 12, 2018 by Kirill A. Shutemov Committed by Ingo Molnar Mar 12, 2018

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>

parent a5b162b2

arch/x86/boot/compressed/head_64.S

+10 −0

Original line number	Diff line number	Diff line
		@@ -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