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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id EC508C00140 for ; Mon, 8 Aug 2022 19:23:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244314AbiHHTXi (ORCPT ); Mon, 8 Aug 2022 15:23:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40698 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229765AbiHHTXg (ORCPT ); Mon, 8 Aug 2022 15:23:36 -0400 Received: from mail-pf1-x44a.google.com (mail-pf1-x44a.google.com [IPv6:2607:f8b0:4864:20::44a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AE1D4D113 for ; Mon, 8 Aug 2022 12:23:35 -0700 (PDT) Received: by mail-pf1-x44a.google.com with SMTP id y7-20020a056a00180700b0052d90ab2314so4176549pfa.10 for ; Mon, 08 Aug 2022 12:23:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:message-id:mime-version:subject:from:to:cc; bh=GneeJVrYoG9YO7ZVBQ9roargUyo6x8eaPqj/O9PmIjg=; b=PIX0Xvjp/psqCIpXyZsRobhPhs2TzYQFsuZPXBNMMWA8BM92Cy/2q7ct1X88kr8KGH 7LIjxxbb/p+4B57iyfmG3/1g2STyUV8l0cA6ebYrUMd1j6WJRqX2JMQD1XDpkkahk3qG JLCAlmInzAt+Fs+Ei4agNnLT5ofyAUcrkKFQqn6cYS2hwelTRK5T52d0S0FsgGzpNPRK kDWiZtcfulr+3H+X+KB2s7DBw0OZalFFLFGPbqMLqDLJgYHTys8ojtieKNAQdp43JmDP ytwJ8+Pxm6pQzmDG9NYnQExVRIv/+2xdBwD3430MbtNNV9Fk+Ho2MGTYTgvnbryZF0un Furg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=GneeJVrYoG9YO7ZVBQ9roargUyo6x8eaPqj/O9PmIjg=; b=Bwv4g4N9uj4HVZPVUqK7hlTqEnOMG04xWbhu5ZmxbGjrVZ098D3RkdBVdQeOi53sF3 DjXLQmoTFX3qu6j13/hVsRu8/Okbes/oNEplWeG7YNLJRHAV8zSKDNziGnBj21nWh8Lv Ld+cVhn1WbdjmiwtgzgQ2oSfBEpw9ClU+vMXmcodbW3ZI8F9LcQoBFZHO1xUmqx6Zw6L 2HAoz8r6wjPVqrUOk2WDV85aWEwR8N9AXejat328Z7FVPutJFHWxBTU8+VVnn02iNe2L pawChBjZAE2fAnZ50Am2JcWbIqmf4T17urvTkMWtCN/GUdUFWo7pyhCSGP+/xROjCLa0 6mNQ== X-Gm-Message-State: ACgBeo3u6QYh1HBZLFQs2wEtk4MmoRXKEbcImzas9dM4kW4+EGEFtqTW l6HD8kniBE+fhFxZ4RUpLgNovj0wqWA/RjAUye4= X-Google-Smtp-Source: AA6agR4dxq9DJfSTVilC1n/kp/hoTsSutuEiPmCPg8tP3fAN7B392n7C1mVY9NCskkWBahvtEWgLfkd8kE90hGAxxi4= X-Received: from ndesaulniers1.mtv.corp.google.com ([2620:15c:211:202:88f6:faa7:16e5:a8d5]) (user=ndesaulniers job=sendgmr) by 2002:a17:90b:384e:b0:1f5:6330:8294 with SMTP id nl14-20020a17090b384e00b001f563308294mr24331796pjb.35.1659986615163; Mon, 08 Aug 2022 12:23:35 -0700 (PDT) Date: Mon, 8 Aug 2022 12:23:05 -0700 Message-Id: <20220808192321.3490995-1-ndesaulniers@google.com> Mime-Version: 1.0 X-Developer-Key: i=ndesaulniers@google.com; a=ed25519; pk=lvO/pmg+aaCb6dPhyGC1GyOCvPueDrrc8Zeso5CaGKE= X-Developer-Signature: v=1; a=ed25519-sha256; t=1659986577; l=4052; i=ndesaulniers@google.com; s=20211004; h=from:subject; bh=S/N2aGgnwD6VqRx44sfulwh57Bc3dypr+izb3FyWnRA=; b=DZ081uVs3rB4foY4W8D7Zp7TalB8H+rUw3W1lvSVan42TCmLsWwfqDyPcdMFj6FGtFnehgoiDoQj EZFMwm3TDQsyViNCnY19yVp93g588Rf/YSlPlp1hF4CED/F/NB4x X-Mailer: git-send-email 2.37.1.559.g78731f0fdb-goog Subject: [PATCH] x86: assemble with -Wa,--noexecstack to avoid BFD 2.39 warning From: Nick Desaulniers To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen Cc: Nick Clifton , Fangrui Song , Linus Torvalds , Nick Desaulniers , Jens Axboe , x86@kernel.org, "H. Peter Anvin" , Nathan Chancellor , Tom Rix , Masahiro Yamada , "Kirill A. Shutemov" , Nicolas Schier , Brijesh Singh , Michael Roth , Kuppuswamy Sathyanarayanan , linux-kernel@vger.kernel.org, llvm@lists.linux.dev Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Users of GNU ld (BFD) from binutils 2.39+ will observe multiple instance of a new warning when linking kernels in the form: ld: warning: arch/x86/realmode/rm/bioscall.o: missing .note.GNU-stack section implies executable stack ld: NOTE: This behaviour is deprecated and will be removed in a future version of the linker The object files producing these all happen to be out of line assembler sources (*.S files). Generally, we would like to avoid the stack being executable. Because there could be a need for the stack to be executable, assembler sources have to opt-in to this security feature via explicit creation of the .note.GNU-stack feature (which compilers create by default) or command line flag --noexecstack. Boot tested defconfig and i386_defconfig in QEMU. If any assembler sources do require executable stack, they can be built with -Wa,--execstack, though the linker warning would have to be disabled. We might need to extend this more generally to the top level Makefile for all architectures, but I'm not equipped to test the result of such a change. LLVM's LLD linker defaults to -z noexecstack, so this flag isn't strictly necessary when linking with LLD, only BFD, but it doesn't hurt to be explicit here for all linkers IMO. Link: https://lore.kernel.org/linux-block/3af4127a-f453-4cf7-f133-a181cce06f73@kernel.dk/ Link: https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=ba951afb99912da01a6e8434126b8fac7aa75107 Link: https://github.com/llvm/llvm-project/issues/57009 Reported-by: Jens Axboe Signed-off-by: Nick Desaulniers --- arch/x86/Makefile | 2 ++ arch/x86/boot/Makefile | 2 +- arch/x86/boot/compressed/Makefile | 2 +- arch/x86/realmode/rm/Makefile | 2 +- 4 files changed, 5 insertions(+), 3 deletions(-) diff --git a/arch/x86/Makefile b/arch/x86/Makefile index 7854685c5f25..571546775725 100644 --- a/arch/x86/Makefile +++ b/arch/x86/Makefile @@ -159,6 +159,8 @@ else KBUILD_CFLAGS += -mcmodel=kernel endif +KBUILD_AFLAGS += -Wa,--noexecstack + # # If the function graph tracer is used with mcount instead of fentry, # '-maccumulate-outgoing-args' is needed to prevent a GCC bug diff --git a/arch/x86/boot/Makefile b/arch/x86/boot/Makefile index b5aecb524a8a..d7f2130f2277 100644 --- a/arch/x86/boot/Makefile +++ b/arch/x86/boot/Makefile @@ -67,7 +67,7 @@ targets += cpustr.h # --------------------------------------------------------------------------- KBUILD_CFLAGS := $(REALMODE_CFLAGS) -D_SETUP -KBUILD_AFLAGS := $(KBUILD_CFLAGS) -D__ASSEMBLY__ +KBUILD_AFLAGS := $(KBUILD_CFLAGS) -D__ASSEMBLY__ -Wa,--noexecstack KBUILD_CFLAGS += $(call cc-option,-fmacro-prefix-map=$(srctree)/=) KBUILD_CFLAGS += -fno-asynchronous-unwind-tables GCOV_PROFILE := n diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile index 19e1905dcbf6..1587a21a132d 100644 --- a/arch/x86/boot/compressed/Makefile +++ b/arch/x86/boot/compressed/Makefile @@ -57,7 +57,7 @@ KBUILD_CFLAGS += -include $(srctree)/include/linux/hidden.h # that the compiler finds it even with out-of-tree builds (make O=/some/path). CFLAGS_sev.o += -I$(objtree)/arch/x86/lib/ -KBUILD_AFLAGS := $(KBUILD_CFLAGS) -D__ASSEMBLY__ +KBUILD_AFLAGS := $(KBUILD_CFLAGS) -D__ASSEMBLY__ -Wa,--noexecstack GCOV_PROFILE := n UBSAN_SANITIZE :=n diff --git a/arch/x86/realmode/rm/Makefile b/arch/x86/realmode/rm/Makefile index 83f1b6a56449..5f2fdafaa034 100644 --- a/arch/x86/realmode/rm/Makefile +++ b/arch/x86/realmode/rm/Makefile @@ -73,7 +73,7 @@ $(obj)/realmode.relocs: $(obj)/realmode.elf FORCE KBUILD_CFLAGS := $(REALMODE_CFLAGS) -D_SETUP -D_WAKEUP \ -I$(srctree)/arch/x86/boot -KBUILD_AFLAGS := $(KBUILD_CFLAGS) -D__ASSEMBLY__ +KBUILD_AFLAGS := $(KBUILD_CFLAGS) -D__ASSEMBLY__ -Wa,--noexecstack KBUILD_CFLAGS += -fno-asynchronous-unwind-tables GCOV_PROFILE := n UBSAN_SANITIZE := n -- 2.37.1.559.g78731f0fdb-goog