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=-8.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,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 A026AC433E0 for ; Tue, 7 Jul 2020 16:05:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7FF0B206C3 for ; Tue, 7 Jul 2020 16:05:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="Kh7nComz" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728568AbgGGQFj (ORCPT ); Tue, 7 Jul 2020 12:05:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39166 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728194AbgGGQFg (ORCPT ); Tue, 7 Jul 2020 12:05:36 -0400 Received: from mail-pg1-x542.google.com (mail-pg1-x542.google.com [IPv6:2607:f8b0:4864:20::542]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A17FBC08C5DC for ; Tue, 7 Jul 2020 09:05:36 -0700 (PDT) Received: by mail-pg1-x542.google.com with SMTP id j19so13346646pgm.11 for ; Tue, 07 Jul 2020 09:05:36 -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=BauIxngYcl8jd5OtL8hzkCrhdMv4YPyYU2tM2gh0/zA=; b=Kh7nComzMNl6xsg1nwO6fTiV+447hKNoK6M36Sv6NGey7FnS2nbTYWy8lHEpSDOcWo 4SZpHdhE0vPOCZrLWLvUJOXmOSR8Gz0owQI+bbcY+s+LsNbCgXfdxmGINNOc3+OKJSEQ 2u6uTR/n4oEx4IA4WPkbLFvCRTsqJQgdkA4/RHz0JUrD5DCmtPUS6lEOlEKwOu+XAqvh gr91UwjGRhE2Bo40UIkl4Z5vIAwl8OKTz32MsAM4e2vgnAlsinZ/e9QSyBdyERrQzk4E y2Omj76am6hjUTfQD5hz2Tiyvs2LsHeHNRlGxwsexsoYrijIaIiXs/D6btrWCA81JdA6 s9vQ== 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=BauIxngYcl8jd5OtL8hzkCrhdMv4YPyYU2tM2gh0/zA=; b=GYk1GOlvEO7x3nCLmiSgZ8IfpKGOVvxzQRn4wNgdyydmUc3pHBo8K87LD5LQ19xa8b XvVghKmACCp135g403UhUeYkgh56t94Qax2NsmoevBboSMicAnkoWd48TteNCv/IDmMl GItOt3GZq2XzOcVAK8s4GRhJp4V/dnVKzYXwv3uJeMN8hJzyxgrKu3MSrt6VxD6xVnWM ecmo4Kwiu/SUAvJltTW4dOSOkXfEO1L3HQDZp4Py3Crq2WuMovy8PaeO0Aqooy5+JSLM j+pLieGjh6ps90TW9CX+SVVX7UC3LLGARqSbeQRrHNPQCcISvY0G9H8uYjI5ciJyQVss cJYA== X-Gm-Message-State: AOAM531xWY6w+jHTE3blfBQ8bIfqX9HKLIqwHHZpviAsqERU5ncolue0 uoYSdkrkNfxOZR+uBnQwbgQp2w== X-Google-Smtp-Source: ABdhPJzJoQVw/SVeuV11W977gCqEtq+6LHotqK+2sy2PsCIQUHIzgnZiA2b8Kfx/70bokWXpdDZzGg== X-Received: by 2002:a63:5110:: with SMTP id f16mr44344138pgb.377.1594137935802; Tue, 07 Jul 2020 09:05:35 -0700 (PDT) Received: from google.com ([2620:15c:201:2:f693:9fff:fef4:1b6d]) by smtp.gmail.com with ESMTPSA id j17sm1222342pgn.87.2020.07.07.09.05.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 07 Jul 2020 09:05:34 -0700 (PDT) Date: Tue, 7 Jul 2020 09:05:28 -0700 From: Sami Tolvanen To: Masahiro Yamada , Jakub Kicinski Cc: Will Deacon , Greg Kroah-Hartman , "Paul E. McKenney" , Kees Cook , Nick Desaulniers , clang-built-linux , Kernel Hardening , linux-arch , linux-arm-kernel , Linux Kbuild mailing list , Linux Kernel Mailing List , linux-pci@vger.kernel.org, X86 ML Subject: Re: [PATCH 00/22] add support for Clang LTO Message-ID: <20200707160528.GA1300535@google.com> References: <20200624203200.78870-1-samitolvanen@google.com> <20200629232059.GA3787278@google.com> <20200707155107.GA3357035@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200707155107.GA3357035@google.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 07, 2020 at 08:51:07AM -0700, Sami Tolvanen wrote: > After spending some time debugging this with Nick, it looks like the > error is caused by a recent optimization change in LLVM, which together > with the inlining of ur_load_imm_any into jeq_imm, changes a runtime > check in FIELD_FIT that would always fail, to a compile-time check that > breaks the build. In jeq_imm, we have: > > /* struct bpf_insn: _s32 imm */ > u64 imm = insn->imm; /* sign extend */ > ... > if (imm >> 32) { /* non-zero only if insn->imm is negative */ > /* inlined from ur_load_imm_any */ > u32 __imm = imm >> 32; /* therefore, always 0xffffffff */ > > /* > * __imm has a value known at compile-time, which means > * __builtin_constant_p(__imm) is true and we end up with > * essentially this in __BF_FIELD_CHECK: > */ > if (__builtin_constant_p(__imm) && __imm <= 255) Should be __imm > 255, of course, which means the compiler will generate a call to __compiletime_assert. > Jiong, Jakub, do you see any issues here? (Jiong's email bounced, so removing from the recipient list.) 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Tue, 07 Jul 2020 09:05:34 -0700 (PDT) Date: Tue, 7 Jul 2020 09:05:28 -0700 From: Sami Tolvanen To: Masahiro Yamada , Jakub Kicinski Subject: Re: [PATCH 00/22] add support for Clang LTO Message-ID: <20200707160528.GA1300535@google.com> References: <20200624203200.78870-1-samitolvanen@google.com> <20200629232059.GA3787278@google.com> <20200707155107.GA3357035@google.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200707155107.GA3357035@google.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200707_120538_628522_BC11868D X-CRM114-Status: GOOD ( 16.03 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch , X86 ML , Kees Cook , "Paul E. McKenney" , Kernel Hardening , Greg Kroah-Hartman , Linux Kbuild mailing list , Nick Desaulniers , Linux Kernel Mailing List , clang-built-linux , linux-pci@vger.kernel.org, Will Deacon , linux-arm-kernel Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Jul 07, 2020 at 08:51:07AM -0700, Sami Tolvanen wrote: > After spending some time debugging this with Nick, it looks like the > error is caused by a recent optimization change in LLVM, which together > with the inlining of ur_load_imm_any into jeq_imm, changes a runtime > check in FIELD_FIT that would always fail, to a compile-time check that > breaks the build. In jeq_imm, we have: > > /* struct bpf_insn: _s32 imm */ > u64 imm = insn->imm; /* sign extend */ > ... > if (imm >> 32) { /* non-zero only if insn->imm is negative */ > /* inlined from ur_load_imm_any */ > u32 __imm = imm >> 32; /* therefore, always 0xffffffff */ > > /* > * __imm has a value known at compile-time, which means > * __builtin_constant_p(__imm) is true and we end up with > * essentially this in __BF_FIELD_CHECK: > */ > if (__builtin_constant_p(__imm) && __imm <= 255) Should be __imm > 255, of course, which means the compiler will generate a call to __compiletime_assert. > Jiong, Jakub, do you see any issues here? (Jiong's email bounced, so removing from the recipient list.) Sami _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel