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=-6.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,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 C8C90C4363A for ; Tue, 27 Oct 2020 08:51:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7EA78207DE for ; Tue, 27 Oct 2020 08:51:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2509499AbgJ0Ivf (ORCPT ); Tue, 27 Oct 2020 04:51:35 -0400 Received: from mail-oi1-f195.google.com ([209.85.167.195]:39000 "EHLO mail-oi1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2509488AbgJ0Ivf (ORCPT ); Tue, 27 Oct 2020 04:51:35 -0400 Received: by mail-oi1-f195.google.com with SMTP id u127so521821oib.6; Tue, 27 Oct 2020 01:51:32 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=QuQazVJddiiMcHpJSWJ6P15wkN0uJ4Rr3unxje95N5k=; b=TnBULGUOLWENKlxwQUv664xtnuu/tIWVynH1dGeC3cYzW5ge8r/xYJD9YH1D66GrKB Tntlol2KG+3jUOa23+MVVRiZjTYoXr04E9zJQhfS7nAMzliCbcGqBjwIONmDgSyM4Nma vZ4u2yO9Ve2LmIZKj/oGhW0wafC8a7cYY0aurMVojF29Ou3XwykxJ9hcai0QNnIc4ONr RpuGj0k0lvuVcn+ZLJOqmN6hMaHrZMNpGJZXAaRmuH2W6B9e3qn73a/+ilq/NeDt2JcE hBXsqYV76q8bLvTlbswDzt5UN1CNLP0DCca7jGyDPqjSQBYD5f7jkCrDJGF9xGxl1lpL uSQQ== X-Gm-Message-State: AOAM533yQx2IFXa6r/hvOjx9hX3ELOEiLcUmy+gENX4rolcqJU4PxXOi VbhtnFynjLRFmndsLBLcyL72I7PAKyIsWjY6BrE= X-Google-Smtp-Source: ABdhPJySfGkbbKGp0kdsGkoJSUHyBdUu4Vk5rkDPOdc2rZmaJaJzvBeFtHoAEvLtFV2WfesebZxh5ZOmpbeFGptGWx0= X-Received: by 2002:aca:f40c:: with SMTP id s12mr663393oih.153.1603788692533; Tue, 27 Oct 2020 01:51:32 -0700 (PDT) MIME-Version: 1.0 References: <20200821194310.3089815-1-keescook@chromium.org> <20200821194310.3089815-14-keescook@chromium.org> In-Reply-To: From: Geert Uytterhoeven Date: Tue, 27 Oct 2020 09:51:21 +0100 Message-ID: Subject: Re: [PATCH v6 13/29] arm64/build: Assert for unwanted sections To: Ard Biesheuvel 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 Hi Ard, On Mon, Oct 26, 2020 at 6:43 PM Geert Uytterhoeven wrote: > On Mon, Oct 26, 2020 at 6:39 PM Ard Biesheuvel wrote: > > 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 > > gcc version 9.3.0 (Ubuntu 9.3.0-17ubuntu1~20.04) from Ubuntu 20.04LTS. > > > command line and/or adding -z norelro to the linker command line make > > any difference? > > I'll give that a try later... Adding -fno-pie to KBUILD_AFLAGS and KBUILD_CFLAGS doesn't make a difference. Same for adding -z norelno to the final link command: aarch64-linux-gnu-ld: warning: -z norelno ignored 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! Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds