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=-7.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 81A10C388F9 for ; Mon, 26 Oct 2020 17:39:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 426CB22242 for ; Mon, 26 Oct 2020 17:39:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603733940; bh=4hsLrGtQdAKvGeJzi/vIk47xvKfHSh+S6XD3mbba3qk=; h=References:In-Reply-To:From:Date:Subject:To:Cc:List-ID:From; b=CbaQ4rQJh1tYrPPP9kVZlHh0/shJjSjDM0QkRvt4SswtEZAErDQbf8lUjRll531+i qI3k8dhptu7T1wFQ8REqD4/dmUUEN0ZYvSJ7bTPVxoob3WX3UKpBmR0J3LGGzDM6CX sXJT2nIcasptt7TZkATFIoUA4wG0L1HE7iEsZrW4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1788060AbgJZRi7 (ORCPT ); Mon, 26 Oct 2020 13:38:59 -0400 Received: from mail.kernel.org ([198.145.29.99]:39980 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1788049AbgJZRi6 (ORCPT ); Mon, 26 Oct 2020 13:38:58 -0400 Received: from mail-oi1-f182.google.com (mail-oi1-f182.google.com [209.85.167.182]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id B55F722242; Mon, 26 Oct 2020 17:38:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603733937; bh=4hsLrGtQdAKvGeJzi/vIk47xvKfHSh+S6XD3mbba3qk=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=Ki915xzFGnRs6mbfsJxyz6VrVipsqoFJfxPyFxN9QyX5SW+ozpyDKZx/5NHQAJVbo 5bS3+tK0zctHNpZ+vQ/2VCGSj1wSWwMbehU3KGahed2dzr++z2eeAZw7gNhvmsPDHV 9vjJ8VJb2Ae7N7VWu1JyBj5srwfzQhCXsZLlZUNs= Received: by mail-oi1-f182.google.com with SMTP id k27so11267406oij.11; Mon, 26 Oct 2020 10:38:57 -0700 (PDT) X-Gm-Message-State: AOAM530Zbfg6Ejawhe+gHMtf6rJWgxTc4zcZMP24olWv6cjd0fRz2Lfs Pvs7vFYnsdGSQdAU7fvoQikI+VWEgXp4R4Sexb8= X-Google-Smtp-Source: ABdhPJys++sp9LWSs9r1c2XSNx2zB7VYH2ScNF9Mo1eSnVB/rKDXCqHiQFOfh3AQmf1CassoG7sGyWZRDjTFxZxfKxk= X-Received: by 2002:aca:d64f:: with SMTP id n76mr15186195oig.174.1603733937001; Mon, 26 Oct 2020 10:38:57 -0700 (PDT) MIME-Version: 1.0 References: <20200821194310.3089815-1-keescook@chromium.org> <20200821194310.3089815-14-keescook@chromium.org> In-Reply-To: From: Ard Biesheuvel Date: Mon, 26 Oct 2020 18:38:46 +0100 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v6 13/29] arm64/build: Assert for unwanted sections To: Geert Uytterhoeven Cc: Kees Cook , Ingo Molnar , Catalin Marinas , Mark Rutland , Peter Collingbourne , James Morse , Borislav Petkov , Ingo Molnar , Russell King , Masahiro Yamada , Arvind Sankar , Nick Desaulniers , Nathan Chancellor , Arnd Bergmann , "the arch/x86 maintainers" , clang-built-linux , Linux-Arch , linux-efi , Linux ARM , Linux Kernel Mailing List , Linux-Renesas Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 26 Oct 2020 at 17:01, Geert Uytterhoeven wrote: > > On Mon, Oct 26, 2020 at 2:29 PM Geert Uytterhoeven wrote: > > On Mon, Oct 26, 2020 at 1:29 PM Geert Uytterhoeven wrote: > > > On Fri, Aug 21, 2020 at 9:56 PM Kees Cook wrote: > > > > In preparation for warning on orphan sections, discard > > > > unwanted non-zero-sized generated sections, and enforce other > > > > expected-to-be-zero-sized sections (since discarding them might hide > > > > problems with them suddenly gaining unexpected entries). > > > > > > > > Suggested-by: Ard Biesheuvel > > > > Signed-off-by: Kees Cook > > > > > > This is now commit be2881824ae9eb92 ("arm64/build: Assert for unwanted > > > sections") in v5.10-rc1, and is causing the following error with > > > renesas_defconfig[1]: > > > > > > aarch64-linux-gnu-ld: warning: orphan section `.eh_frame' from > > > `kernel/bpf/core.o' being placed in section `.eh_frame' > > > aarch64-linux-gnu-ld: Unexpected GOT/PLT entries detected! > > > aarch64-linux-gnu-ld: Unexpected run-time procedure linkages detected! > > > > > > I cannot reproduce this with the standard arm64 defconfig. > > > > > > I bisected the error to the aforementioned commit, but understand this > > > is not the real reason. If I revert this commit, I still get: > > > > > > aarch64-linux-gnu-ld: warning: orphan section `.got.plt' from > > > `arch/arm64/kernel/head.o' being placed in section `.got.plt' > > > aarch64-linux-gnu-ld: warning: orphan section `.plt' from > > > `arch/arm64/kernel/head.o' being placed in section `.plt' > > > aarch64-linux-gnu-ld: warning: orphan section `.data.rel.ro' from > > > `arch/arm64/kernel/head.o' being placed in section `.data.rel.ro' > > > aarch64-linux-gnu-ld: warning: orphan section `.eh_frame' from > > > `kernel/bpf/core.o' being placed in section `.eh_frame' > > > > > > I.e. including the ".eh_frame" warning. I have tried bisecting that > > > warning (i.e. with be2881824ae9eb92 reverted), but that leads me to > > > commit b3e5d80d0c48c0cc ("arm64/build: Warn on orphan section > > > placement"), which is another red herring. > > > > kernel/bpf/core.o is the only file containing an eh_frame section, > > causing the warning. > > If I compile core.c with "-g" added, like arm64 defconfig does, the > > eh_frame section is no longer emitted. > > > > Hence setting CONFIG_DEBUG_INFO=y, cfr. arm64 defconfig, the warning > > is gone, but I'm back to the the "Unexpected GOT/PLT entries" below... > > > > > Note that even on plain be2881824ae9eb92, I get: > > > > > > aarch64-linux-gnu-ld: Unexpected GOT/PLT entries detected! > > > aarch64-linux-gnu-ld: Unexpected run-time procedure linkages detected! > > > > > > The parent commit obviously doesn't show that (but probably still has > > > the problem). > > Reverting both > b3e5d80d0c48c0cc ("arm64/build: Warn on orphan section placement") > be2881824ae9eb92 ("arm64/build: Assert for unwanted sections") > seems to solve my problems, without any ill effects? > I cannot reproduce the issue here with my distro GCC+binutils (Debian 8.3.0) The presence of .data.rel.ro and .got.plt sections suggests that the toolchain is using -fpie and/or -z relro to build shared objects rather than a fully linked bare metal binary. Which toolchain are you using? Does adding -fno-pie to the compiler command line and/or adding -z norelro to the linker command line make any difference?