From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932433AbeCLKDs (ORCPT ); Mon, 12 Mar 2018 06:03:48 -0400 Received: from mga18.intel.com ([134.134.136.126]:10663 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751252AbeCLKC5 (ORCPT ); Mon, 12 Mar 2018 06:02:57 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.47,460,1515484800"; d="scan'208";a="37996177" From: "Kirill A. Shutemov" To: Ingo Molnar , x86@kernel.org, Thomas Gleixner , "H. Peter Anvin" Cc: Linus Torvalds , Andy Lutomirski , Cyrill Gorcunov , Borislav Petkov , Andi Kleen , Matthew Wilcox , linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Kirill A. Shutemov" Subject: [PATCH 1/4] x86/boot/compressed/64: Make sure we have 32-bit code segment Date: Mon, 12 Mar 2018 13:02:43 +0300 Message-Id: <20180312100246.89175-2-kirill.shutemov@linux.intel.com> X-Mailer: git-send-email 2.16.1 In-Reply-To: <20180312100246.89175-1-kirill.shutemov@linux.intel.com> References: <20180312100246.89175-1-kirill.shutemov@linux.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When kernel starts in 64-bit mode we inherit GDT from a bootloader. It may cause a problem if the GDT doesn't have 32-bit code segment where we expect it to be. Load our own GDT with known segments. Signed-off-by: Kirill A. Shutemov --- arch/x86/boot/compressed/head_64.S | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index c813cb004056..f0c3a2f7e528 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -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 -- 2.16.1