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 5E77AC2BC11 for ; Tue, 8 Sep 2020 23:28:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2449F21D20 for ; Tue, 8 Sep 2020 23:28:54 +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 S1729622AbgIHX2q (ORCPT ); Tue, 8 Sep 2020 19:28:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40430 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726591AbgIHX2o (ORCPT ); Tue, 8 Sep 2020 19:28:44 -0400 Received: from mail-pf1-x441.google.com (mail-pf1-x441.google.com [IPv6:2607:f8b0:4864:20::441]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AEC7EC061755 for ; Tue, 8 Sep 2020 16:28:43 -0700 (PDT) Received: by mail-pf1-x441.google.com with SMTP id f18so463149pfa.10 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=p9WlmC/FyQ7yO6eftA0jJQK0/ypyDBs/V4Omgy7iEC35vkbXnDpTSSnC+SULqPfQWl LHKIzy01DfZgXRQDHGbfc4dNrVqqInbpyddHgMnyw2ULUBWJBI/Tci9rsVzdUIDtQ+bC 6+9jPU6u/tOEgzIZn0uXKb9PzZ0vv2ImRa0/3z41Qi3HZOfkQoa8Ri3p0Xm1psekR0Ai ziKB82UskKFWgQEfPktA/MH5yAkBxia7zhTZMSKbnaaS2krxilMcn+99SbKMN+CkpGSX CjyaWrhhdWqOXIIwRRSLAWpFgdPIWKFUgPHH1S9Gqv9P/X3SPJ3hyqg0FJ1VudloLtP/ 15PA== X-Gm-Message-State: AOAM531YVZcIha+FNQOFRcnDjh8N8wiUZLZglK+zNKChSU9JONhJ8nGM jS2cIfw85LZN2QL3ftalyXSJHw== 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-kbuild-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kbuild@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