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=-11.7 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,FSL_HELO_FAKE, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_IN_DEF_DKIM_WL 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 DE36AC433E2 for ; Tue, 8 Sep 2020 23:28:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 773DF2087C for ; Tue, 8 Sep 2020 23:28:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="E/YiH9PD" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729719AbgIHX2q (ORCPT ); Tue, 8 Sep 2020 19:28:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40428 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726340AbgIHX2o (ORCPT ); Tue, 8 Sep 2020 19:28:44 -0400 Received: from mail-pf1-x443.google.com (mail-pf1-x443.google.com [IPv6:2607:f8b0:4864:20::443]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 99E7AC061573 for ; Tue, 8 Sep 2020 16:28:43 -0700 (PDT) Received: by mail-pf1-x443.google.com with SMTP id d9so490762pfd.3 for ; Tue, 08 Sep 2020 16:28:43 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=jUriBxBgOoiBsn5aO7jNWcqqf+vaiVxUYWRnLqNR1jM=; b=E/YiH9PD3ihV0IVAR5rz+kH+b53wXLSIKmpoiOzCUGIjKpPkUvepTJzZ9+NUfPet6f GjaxzmgrBjNjqjo0f2ixc8d1ESWRgiXmk3RC5UCTuoEZePHlVeleHkJJVCXbHB4Iy0lP zLqt5AipHKpsckEr1GfvlWy6tszT/wsVnsbnykJcDboXcXvM/ADW0EnFJR3kQ6JqRDJF dSHe06Qm/HcGK8ogoctsoW5WtSXiP+swQULLf66N1XBjDhEHsTBRP9zhxOTsHLpYe4Th 9lAz0y/0D5FyUST+gVXhf1nWDMBty0024ty3DlA3ziBDE0uWDvAZu1LLk2dJzbpawFdm KS8Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=jUriBxBgOoiBsn5aO7jNWcqqf+vaiVxUYWRnLqNR1jM=; b=GNkMEpO8vJplboQN1FF2T2T9evsdYr04nCbwDN8kuW9rgp7Ki50+kCZkAG+XHDf7iV FKqcivCkxYNyg9/PWXXtlqcFekJhgBGwb7loke73FKQLRNri0CatNI8xf4BwrXruztR1 AJQUyDd+ndErd5Zi7VKR7nhhBz7DGxKVoK91AhDq+C1Ysdv4scmL0vbQBU77RH7B/Loj lTVSL7w5Yc6XjgN4DpEbxvoMnhxYu/NGg1DshXdJrgSLr/2XaQziaXQmcfCACYI7u4AU XgN8xeyw8g52Tva5j4mXgjYnd5hpBBrip01tW2cvz/5DZd4dhxaXxGl2/eHdL+1OAvpp y1Cg== X-Gm-Message-State: AOAM532Z8Sz3HJoBULU1bov+eMjYQ2knImJf7/izs+knwLHN3xE65k01 7EEiGZzakhVQJWkibpcEEhQTtw== X-Google-Smtp-Source: ABdhPJxtrczatAsJe/2asERi0zZusFb9ssrn7lKjqOGwCxb8YO5oCcKiBSLXYms184w0IymH7gdSoA== X-Received: by 2002:a17:902:b108:b029:d0:cbe1:e770 with SMTP id q8-20020a170902b108b02900d0cbe1e770mr1342847plr.23.1599607722874; Tue, 08 Sep 2020 16:28:42 -0700 (PDT) Received: from google.com ([2620:15c:201:2:f693:9fff:fef4:1b6d]) by smtp.gmail.com with ESMTPSA id w192sm465817pfd.156.2020.09.08.16.28.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 08 Sep 2020 16:28:42 -0700 (PDT) Date: Tue, 8 Sep 2020 16:28:35 -0700 From: Sami Tolvanen To: Kees Cook Cc: Masahiro Yamada , Will Deacon , Peter Zijlstra , Steven Rostedt , Greg Kroah-Hartman , "Paul E. McKenney" , Nick Desaulniers , clang-built-linux@googlegroups.com, kernel-hardening@lists.openwall.com, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, x86@kernel.org Subject: Re: [PATCH v2 27/28] x86, relocs: Ignore L4_PAGE_OFFSET relocations Message-ID: <20200908232835.GE1060586@google.com> References: <20200624203200.78870-1-samitolvanen@google.com> <20200903203053.3411268-1-samitolvanen@google.com> <20200903203053.3411268-28-samitolvanen@google.com> <202009031546.4854633F7@keescook> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <202009031546.4854633F7@keescook> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 03, 2020 at 03:47:32PM -0700, Kees Cook wrote: > On Thu, Sep 03, 2020 at 01:30:52PM -0700, Sami Tolvanen wrote: > > L4_PAGE_OFFSET is a constant value, so don't warn about absolute > > relocations. > > > > Signed-off-by: Sami Tolvanen > > Any other details on this? I assume this is an ld.lld-ism. Any idea why > this is only a problem under LTO? (Or is this an LLVM integrated > assembler-ism?) Regardless, yes, let's nail it down: With the LTO v1 series, LLD generated this relocation somewhere in the .init.data section, but only with LTO: $ arch/x86/tools/relocs --abs-relocs vmlinux WARNING: Absolute relocations present Offset Info Type Sym.Value Sym.Name ffffffff828e7fe0 0000000100000001 R_X86_64_64 0000000000000111 L4_PAGE_OFFSET It actually looks like this might not be a problem anymore with the current ToT kernel and the v2 series, but I'll do some more testing to confirm this and drop the patch from v3 if it's no longer needed. Sami