From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl0-f72.google.com (mail-pl0-f72.google.com [209.85.160.72]) by kanga.kvack.org (Postfix) with ESMTP id A92476B0006 for ; Mon, 12 Mar 2018 06:02:58 -0400 (EDT) Received: by mail-pl0-f72.google.com with SMTP id bb5-v6so8339878plb.22 for ; Mon, 12 Mar 2018 03:02:58 -0700 (PDT) Received: from mga02.intel.com (mga02.intel.com. [134.134.136.20]) by mx.google.com with ESMTPS id b66si3050064pgc.148.2018.03.12.03.02.57 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 12 Mar 2018 03:02:57 -0700 (PDT) From: "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> In-Reply-To: <20180312100246.89175-1-kirill.shutemov@linux.intel.com> References: <20180312100246.89175-1-kirill.shutemov@linux.intel.com> Sender: owner-linux-mm@kvack.org List-ID: 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" 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