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=-4.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 61EC1C433DF for ; Tue, 7 Jul 2020 17:12:11 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id B752C206F6 for ; Tue, 7 Jul 2020 17:12:10 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="WfluW2mA" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B752C206F6 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-19226-kernel-hardening=archiver.kernel.org@lists.openwall.com Received: (qmail 29842 invoked by uid 550); 7 Jul 2020 17:12:03 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Received: (qmail 24574 invoked from network); 7 Jul 2020 16:57:06 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594141014; bh=Pxamgvc2FYcqKzB/kO/K+pvItVmdREDTa9V2Uq/pm90=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=WfluW2mALu5v2u4IsB9+2+vbjc5luGQpkCpWji2UWyn5eJGKh2+w3PCRaCORF0/YN +46mUvg1IPuLlsjfbJFei4Opj8gC35QmxI1XVnc0h/gl29judPMY7nyXTpvF+QwI80 oPi+MhkEYdPflHpFGc+lNEnz/Mg7+kCFEw68dC9I= Date: Tue, 7 Jul 2020 09:56:51 -0700 From: Jakub Kicinski To: Sami Tolvanen Cc: Masahiro Yamada , 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: <20200707095651.422f0b22@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> In-Reply-To: <20200707160528.GA1300535@google.com> References: <20200624203200.78870-1-samitolvanen@google.com> <20200629232059.GA3787278@google.com> <20200707155107.GA3357035@google.com> <20200707160528.GA1300535@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Tue, 7 Jul 2020 09:05:28 -0700 Sami Tolvanen 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) > > Should be __imm > 255, of course, which means the compiler will generate > a call to __compiletime_assert. 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?