From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B9856C43387 for ; Sat, 12 Jan 2019 10:00:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 91EDC20675 for ; Sat, 12 Jan 2019 10:00:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725863AbfALKAh convert rfc822-to-8bit (ORCPT ); Sat, 12 Jan 2019 05:00:37 -0500 Received: from mail.accesssoftek.com ([12.202.173.242]:47677 "EHLO mail.accesssoftek.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725816AbfALKAh (ORCPT ); Sat, 12 Jan 2019 05:00:37 -0500 Received: from vm-mail2k13.accesssoftek.com (172.16.0.242) by vm-mail2k13.accesssoftek.com (172.16.0.242) with Microsoft SMTP Server (TLS) id 15.0.1395.4; Sat, 12 Jan 2019 02:00:36 -0800 Received: from vm-mail2k13.accesssoftek.com ([::1]) by vm-mail2k13.accesssoftek.com ([::1]) with mapi id 15.00.1395.000; Sat, 12 Jan 2019 02:00:36 -0800 From: George Rimar To: Tri Vo , "x86@kernel.org" , "tglx@linutronix.de" , "mingo@redhat.com" , "bp@alien8.de" , "hpa@zytor.com" CC: "dima@golovin.in" , "morbo@google.com" , "ndesaulniers@google.com" , "matz@suse.de" , "ruiu@google.com" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH v3] x86_64: Add "-m elf_i386" when linking i386 object files. Thread-Topic: [PATCH v3] x86_64: Add "-m elf_i386" when linking i386 object files. Thread-Index: AQHUqemzjPdoQZ+FoUOJC0WuWoOLa6WrZ3sx Date: Sat, 12 Jan 2019 10:00:36 +0000 Message-ID: <1547286899727.75112@accesssoftek.com> References: ,<20190111201012.71210-1-trong@android.com> In-Reply-To: <20190111201012.71210-1-trong@android.com> Accept-Language: ru-RU, en-US Content-Language: ru-RU X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [95.174.98.187] Content-Type: text/plain; charset="koi8-r" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Signed-off-by: George Rimar Best regards, George | Developer | Access Softek, Inc ________________________________________ От: Tri Vo Отправлено: 11 января 2019 г. 23:10 Кому: x86@kernel.org; tglx@linutronix.de; mingo@redhat.com; bp@alien8.de; hpa@zytor.com Копия: George Rimar; dima@golovin.in; morbo@google.com; ndesaulniers@google.com; matz@suse.de; ruiu@google.com; linux-kernel@vger.kernel.org; Tri Vo Тема: [PATCH v3] x86_64: Add "-m elf_i386" when linking i386 object files. CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe. If you suspect potential phishing or spam email, report it to ReportSpam@accesssoftek.com From: George Rimar Linux kernel uses OUTPUT_FORMAT in it's linker scripts. Most of the time -m option is passed to the linker with correct architecture, but sometimes (at least for x86_64) the -m option contradicts OUTPUT_FORMAT directive. Specifically, arch/x86/boot and arch/x86/realmode/rm modules have i386 object files, but are linked with -m elf_x86_64 linker flag when building for x86_64. "man ld" doesn't explicitly state any tie-breakers between -m and OUTPUT_FORMAT. BFD and Gold linkers override -m value with OUTPUT_FORMAT. But LLVM lld has a different behavior. When supplied with contradicting -m and OUTPUT_FORMAT values it fails with the following error message: ld.lld: error: arch/x86/realmode/rm/header.o is incompatible with elf_x86_64 Suggested fix: just add correct -m after incorrect one (it overrides it), so the linker invocation looks like this: ld -m elf_x86_64 -z max-page-size=0x200000 -m elf_i386 --emit-relocs -T realmode.lds header.o trampoline_64.o stack.o reboot.o -o realmode.elf This is not a functional change for GNU ld, because (although not explicitly documented) it already overrides -m EMULATION with OUTPUT_FORMAT. Tested by building x86_64 kernel with GNU gcc/ld toolchain and booting it in QEMU. Suggested-by: Dmitry Golovin Signed-off-by: George Rimar Signed-off-by: Tri Vo Tested-by: Tri Vo Tested-by: Nick Desaulniers --- v2: updated commit message to clarify that ld documentation is ambiguous w.r.t -m vs OUTPUT_FORMAT behavior. v3: fixed/added SOB and "Tested-by" fields. arch/x86/boot/Makefile | 2 +- arch/x86/realmode/rm/Makefile | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/boot/Makefile b/arch/x86/boot/Makefile index 9b5adae9cc40..e2839b5c246c 100644 --- a/arch/x86/boot/Makefile +++ b/arch/x86/boot/Makefile @@ -100,7 +100,7 @@ $(obj)/zoffset.h: $(obj)/compressed/vmlinux FORCE AFLAGS_header.o += -I$(objtree)/$(obj) $(obj)/header.o: $(obj)/zoffset.h -LDFLAGS_setup.elf := -T +LDFLAGS_setup.elf := -m elf_i386 -T $(obj)/setup.elf: $(src)/setup.ld $(SETUP_OBJS) FORCE $(call if_changed,ld) diff --git a/arch/x86/realmode/rm/Makefile b/arch/x86/realmode/rm/Makefile index 4463fa72db94..96cb20de08af 100644 --- a/arch/x86/realmode/rm/Makefile +++ b/arch/x86/realmode/rm/Makefile @@ -47,7 +47,7 @@ $(obj)/pasyms.h: $(REALMODE_OBJS) FORCE targets += realmode.lds $(obj)/realmode.lds: $(obj)/pasyms.h -LDFLAGS_realmode.elf := --emit-relocs -T +LDFLAGS_realmode.elf := -m elf_i386 --emit-relocs -T CPPFLAGS_realmode.lds += -P -C -I$(objtree)/$(obj) targets += realmode.elf -- 2.20.1.97.g81188d93c3-goog