From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752302AbdLGGQa (ORCPT ); Thu, 7 Dec 2017 01:16:30 -0500 Received: from mail-wr0-f194.google.com ([209.85.128.194]:43579 "EHLO mail-wr0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750780AbdLGGQ2 (ORCPT ); Thu, 7 Dec 2017 01:16:28 -0500 X-Google-Smtp-Source: AGs4zMbs1fM9CcPq9rYz1uMmuDKnn/de0TDZV4AMpJXWlIM73NPf/gMYq0PFY71k5qckxvd17okG9Q== Date: Thu, 7 Dec 2017 07:16:24 +0100 From: Ingo Molnar To: "Kirill A. Shutemov" Cc: Ingo Molnar , x86@kernel.org, Thomas Gleixner , "H. Peter Anvin" , Linus Torvalds , Andy Lutomirski , Cyrill Gorcunov , Borislav Petkov , Andi Kleen , linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCHv4 1/4] x86/boot/compressed/64: Fix build with GCC < 5 Message-ID: <20171207061624.6sx3f67fmpzkrueh@gmail.com> References: <20171205135942.24634-1-kirill.shutemov@linux.intel.com> <20171205135942.24634-2-kirill.shutemov@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171205135942.24634-2-kirill.shutemov@linux.intel.com> User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Kirill A. Shutemov wrote: > 0-day reported this build error: > > arch/x86/boot/compressed/pgtable_64.o: In function `l5_paging_required': > pgtable_64.c:(.text+0x22): undefined reference to `__force_order' > > The issue is only with GCC < 5 and when KASLR is disabled. Newer GCC > works fine. > > __force_order is used by special_insns.h asm code to force instruction > serialization. s/is used by special_insns.h asm code /is used by the special_insns.h asm code > It doesn't actually referenced from the code, but GCC < 5 with -fPIE > would still generate undefined symbol. s/It doesn't actually referenced from the code /It isn't actually referenced from the code s/would still generate undefined symbol. /would still generate an undefined symbol. > I didn't noticed this before and failed to move __force_order definition > from pagetable.c (which compiles only with KASLR enabled) to > pgtable_64.c. > > Signed-off-by: Kirill A. Shutemov > Fixes: 10c9a5346f72 ("x86/boot/compressed/64: Detect and handle 5-level paging at boot-time") > Cc: stable@vger.kernel.org > --- > arch/x86/boot/compressed/pagetable.c | 3 --- > arch/x86/boot/compressed/pgtable_64.c | 11 +++++++++++ > 2 files changed, 11 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/boot/compressed/pagetable.c b/arch/x86/boot/compressed/pagetable.c > index 6bd51de4475c..250826ac216e 100644 > --- a/arch/x86/boot/compressed/pagetable.c > +++ b/arch/x86/boot/compressed/pagetable.c > @@ -38,9 +38,6 @@ > #define __PAGE_OFFSET __PAGE_OFFSET_BASE > #include "../../mm/ident_map.c" > > -/* Used by pgtable.h asm code to force instruction serialization. */ > -unsigned long __force_order; > - > /* Used to track our page table allocation area. */ > struct alloc_pgt_data { > unsigned char *pgt_buf; > diff --git a/arch/x86/boot/compressed/pgtable_64.c b/arch/x86/boot/compressed/pgtable_64.c > index 7bcf03b376da..491fa2d08bca 100644 > --- a/arch/x86/boot/compressed/pgtable_64.c > +++ b/arch/x86/boot/compressed/pgtable_64.c > @@ -1,5 +1,16 @@ > #include > > +/* > + * __force_order is used by special_insns.h asm code to force instruction > + * serialization. s/is used by special_insns.h asm code /is used by the special_insns.h asm code > + * > + * It doesn't actually referenced from the code, but GCC < 5 with -fPIE > + * would still generate undefined symbol. s/It doesn't actually referenced from the code /It isn't actually referenced from the code s/would still generate undefined symbol. /would still generate an undefined symbol. > + * > + * Let's workaround this by defining the variable. s/Let's workaround /Let's work around Also, for the title: s/Fix build with GCC < 5 /Fix the build with GCC < 5 Thanks, Ingo