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=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 E9E3AC433DF for ; Tue, 7 Jul 2020 17:30:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C9D6D20771 for ; Tue, 7 Jul 2020 17:30:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594143017; bh=y/nx2A612UM8oaRHFRt0pVJEofy/MD08EpnGh5tjD2M=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=rYdEThrTKvGRP4hJ2FJ3oTs6FZqP2YZPeIm5qTvT/BX3Pdioabd3WQOiCjfl1r3Hj xfuB9AZeg0Ky8seQJMGDzyU8ZYXXThYOO/Wlf6DHShhf42/+tYEXUeyJgzQuCe7bjJ CYlBqp9onobKhPobQVU9/YbqpXDbboArmsyAeBik= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728487AbgGGRaP (ORCPT ); Tue, 7 Jul 2020 13:30:15 -0400 Received: from mail.kernel.org ([198.145.29.99]:33158 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727834AbgGGRaO (ORCPT ); Tue, 7 Jul 2020 13:30:14 -0400 Received: from kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com (unknown [163.114.132.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A2E542075B; Tue, 7 Jul 2020 17:30:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594143014; bh=y/nx2A612UM8oaRHFRt0pVJEofy/MD08EpnGh5tjD2M=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=vPwLy/dZrsf2lKc6xY5QZhb/lBO3J7u2UOg6Z2mZZrHboN5O1gXQJch4ETtg93Thk PKaf7C8MJrbvEHq3g7RsJbQsdoIzLcGWhcKnBK+3YH/JpTgls0dA33TnIblRELXwPn TrJEP18+dbybB5rl0khvQJt0tNqdZ6h0juyVMOtk= Date: Tue, 7 Jul 2020 10:30:11 -0700 From: Jakub Kicinski To: Nick Desaulniers Cc: Sami Tolvanen , Masahiro Yamada , Will Deacon , Greg Kroah-Hartman , "Paul E. McKenney" , Kees Cook , 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: <20200707103011.173d38c1@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> In-Reply-To: References: <20200624203200.78870-1-samitolvanen@google.com> <20200629232059.GA3787278@google.com> <20200707155107.GA3357035@google.com> <20200707160528.GA1300535@google.com> <20200707095651.422f0b22@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 7 Jul 2020 10:17:25 -0700 Nick Desaulniers wrote: > On Tue, Jul 7, 2020 at 9:56 AM Jakub Kicinski wrote: > > > > > 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) > > > > I think FIELD_FIT() should not pass the value into __BF_FIELD_CHECK(). > > > > So: > > > > diff --git a/include/linux/bitfield.h b/include/linux/bitfield.h > > index 48ea093ff04c..4e035aca6f7e 100644 > > --- a/include/linux/bitfield.h > > +++ b/include/linux/bitfield.h > > @@ -77,7 +77,7 @@ > > */ > > #define FIELD_FIT(_mask, _val) \ > > ({ \ > > - __BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_FIT: "); \ > > + __BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_FIT: "); \ > > !((((typeof(_mask))_val) << __bf_shf(_mask)) & ~(_mask)); \ > > }) > > > > It's perfectly legal to pass a constant which does not fit, in which > > case FIELD_FIT() should just return false not break the build. > > > > Right? > > I see the value of the __builtin_constant_p check; this is just a very > interesting case where rather than an integer literal appearing in the > source, the compiler is able to deduce that the parameter can only > have one value in one case, and allows __builtin_constant_p to > evaluate to true for it. > > I had definitely asked Sami about the comment above FIELD_FIT: > """ > 76 * Return: true if @_val can fit inside @_mask, false if @_val is > too big. > """ > in which FIELD_FIT doesn't return false if @_val is too big and a > compile time constant. (Rather it breaks the build). > > Of the 14 expansion sites of FIELD_FIT I see in mainline, it doesn't > look like any integral literals are passed, so maybe the compile time > checks of _val are of little value for FIELD_FIT. Also I just double checked and all FIELD_FIT() uses check the return value. > So I think your suggested diff is the most concise fix. Feel free to submit that officially as a patch if it fixes the build for you, here's my sign-off: Signed-off-by: Jakub Kicinski 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=-7.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 07DC5C433DF for ; Tue, 7 Jul 2020 17:31:45 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id CB1DF2075B for ; Tue, 7 Jul 2020 17:31:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="Z0ROXAC+"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="vPwLy/dZ" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CB1DF2075B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=Yfcut/O5CRpb4/0E/Kn20SC1mEtyY1pbZzmrAVSPZyU=; b=Z0ROXAC+BblwiTg/Kg9PfDDGQ dtIv0CfJDtaNmWQIIVDvRwpbSiX0xCsAAJJoBq7POnTJ/CmOPl6jRQjF5LkqSIvOmua9Hzv4sJwEm QCK+sPsjwdgC9Y00dklw3YbpDmtPXpN4oEZRjNJxy+Y+xGw8UBABaZkqccEm99EOEFF09WT8qCNav 18S8WIp2+KvVnAIeT0jqY8nUAW4CexUshkvt6LS0UFE9Bl9J61d2BfCbkTCK+Hby1ExGTJYlU66TF BaOA8CWDET+D/RbLD6WsmV2dMU0fPDLIPDMmKkzkb+zOAXsZTH3K3xV4mule0sc5KicOeSbn6BxJi CXW/QKATA==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jsrQA-0000C2-3W; Tue, 07 Jul 2020 17:30:18 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jsrQ7-0000BA-4Y for linux-arm-kernel@lists.infradead.org; Tue, 07 Jul 2020 17:30:16 +0000 Received: from kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com (unknown [163.114.132.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A2E542075B; Tue, 7 Jul 2020 17:30:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594143014; bh=y/nx2A612UM8oaRHFRt0pVJEofy/MD08EpnGh5tjD2M=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=vPwLy/dZrsf2lKc6xY5QZhb/lBO3J7u2UOg6Z2mZZrHboN5O1gXQJch4ETtg93Thk PKaf7C8MJrbvEHq3g7RsJbQsdoIzLcGWhcKnBK+3YH/JpTgls0dA33TnIblRELXwPn TrJEP18+dbybB5rl0khvQJt0tNqdZ6h0juyVMOtk= Date: Tue, 7 Jul 2020 10:30:11 -0700 From: Jakub Kicinski To: Nick Desaulniers Subject: Re: [PATCH 00/22] add support for Clang LTO Message-ID: <20200707103011.173d38c1@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> In-Reply-To: References: <20200624203200.78870-1-samitolvanen@google.com> <20200629232059.GA3787278@google.com> <20200707155107.GA3357035@google.com> <20200707160528.GA1300535@google.com> <20200707095651.422f0b22@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200707_133015_351044_B452D286 X-CRM114-Status: GOOD ( 28.01 ) 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 , Masahiro Yamada , Linux Kbuild mailing list , Linux Kernel Mailing List , clang-built-linux , Sami Tolvanen , 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, 7 Jul 2020 10:17:25 -0700 Nick Desaulniers wrote: > On Tue, Jul 7, 2020 at 9:56 AM Jakub Kicinski wrote: > > > > > 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) > > > > I think FIELD_FIT() should not pass the value into __BF_FIELD_CHECK(). > > > > So: > > > > diff --git a/include/linux/bitfield.h b/include/linux/bitfield.h > > index 48ea093ff04c..4e035aca6f7e 100644 > > --- a/include/linux/bitfield.h > > +++ b/include/linux/bitfield.h > > @@ -77,7 +77,7 @@ > > */ > > #define FIELD_FIT(_mask, _val) \ > > ({ \ > > - __BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_FIT: "); \ > > + __BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_FIT: "); \ > > !((((typeof(_mask))_val) << __bf_shf(_mask)) & ~(_mask)); \ > > }) > > > > It's perfectly legal to pass a constant which does not fit, in which > > case FIELD_FIT() should just return false not break the build. > > > > Right? > > I see the value of the __builtin_constant_p check; this is just a very > interesting case where rather than an integer literal appearing in the > source, the compiler is able to deduce that the parameter can only > have one value in one case, and allows __builtin_constant_p to > evaluate to true for it. > > I had definitely asked Sami about the comment above FIELD_FIT: > """ > 76 * Return: true if @_val can fit inside @_mask, false if @_val is > too big. > """ > in which FIELD_FIT doesn't return false if @_val is too big and a > compile time constant. (Rather it breaks the build). > > Of the 14 expansion sites of FIELD_FIT I see in mainline, it doesn't > look like any integral literals are passed, so maybe the compile time > checks of _val are of little value for FIELD_FIT. Also I just double checked and all FIELD_FIT() uses check the return value. > So I think your suggested diff is the most concise fix. Feel free to submit that officially as a patch if it fixes the build for you, here's my sign-off: Signed-off-by: Jakub Kicinski _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel