From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AIpwx495zEpbiMQUaIgZrXL5XIj541jdWKr7J8x7xyfDivDRHH6g0XoUjt+S5SvBu8PKRXyiP8wL ARC-Seal: i=1; a=rsa-sha256; t=1522870368; cv=none; d=google.com; s=arc-20160816; b=OcsPcZogv8lDLcgmsT8yh8yuzU/JFy8cGoyzv1bk5r+v4sfiCS4W52JRhKYD2/dTle c6kr+LhceWzkpHBDLj/k3YAms81kzNX49WEzIkZEJmyc23cUPCYAWgvMYSVsd76zapJv m6pFKoaOuDPLMBTaftQjp5Ri8/GGIQFsr81VdcMhQt8x6b1tX5icK1xVXUTkpoPGqjhg 7QCy0BfI2RvgGqOxf71rWN6h7OOkdIFL7r2TiVm4lrLURG2AeBGJ8k/4hNoRnhmA3JoD pQ8ddmopjAuMadMUjupW5t9M527knVv5AkughL6Gr8R3n2rYNeiRq5+AR93X3l9mqvQD ulFg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=user-agent:in-reply-to:content-disposition:mime-version:references :message-id:subject:cc:to:from:date:arc-authentication-results; bh=NwQiVVI02bDvarG+aUYtvtB8DN2aJB7MazSG5MuybAk=; b=IbY0xxM1R4hcXKW6vYqpmRHPtMCZrirg9xQsnGDMD2qN/Rv9BA7brPkSqJsj4rj1R/ QqPZvWcFI8cFvBtGnNXa2Kzu1aaeIe+BnFn27Ud/vgjH2QlBHbndI04E/AvxNUqktBiY VYQ3+P2izb5z9d3M/82UB4srByqcFa05sD9EDovMjHAcIKcFEXIQpCuaRuCvxCSg/Iaj aH3la1u1yCyXmUz3kpojIULHJDc55SWhf/z+ORDvRLMpw9vFTxMgJdlwk5Kr8ul+qL78 Z3UFADpbmrBucjD7XbCpIhx9Ft0RcOvv2J1Xo7YgsAnjlb2oIsuBlYCCuUOh7OjmrwCg R+Hg== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of jpoimboe@redhat.com designates 66.187.233.73 as permitted sender) smtp.mailfrom=jpoimboe@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Authentication-Results: mx.google.com; spf=pass (google.com: domain of jpoimboe@redhat.com designates 66.187.233.73 as permitted sender) smtp.mailfrom=jpoimboe@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Date: Wed, 4 Apr 2018 14:32:47 -0500 From: Josh Poimboeuf To: Nick Desaulniers Cc: Greg KH , Matthias Kaehlcke , Ingo Molnar , Peter Zijlstra , Linus Torvalds , LKML , Thomas Gleixner , Andrew Morton , James Y Knight , Chandler Carruth , Stephen Hines , Kees Cook , groeck@chromium.org, Greg Hackmann Subject: Re: [GIT PULL] x86/build changes for v4.17 Message-ID: <20180404193247.lsoxe3xjcidwtlgv@treble> References: <20180402095033.nfzcrmxvpm46dhbl@gmail.com> <20180403085904.GY4082@hirez.programming.kicks-ass.net> <20180403095118.rpf7tj577dppvx7d@gmail.com> <20180403180658.GE87376@google.com> <20180404093823.GC25996@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.6.0.1 (2016-04-01) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-LABELS: =?utf-8?b?IlxcSW1wb3J0YW50Ig==?= X-GMAIL-THRID: =?utf-8?q?1596675801568391777?= X-GMAIL-MSGID: =?utf-8?q?1596845319349905193?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Wed, Apr 04, 2018 at 04:53:52PM +0000, Nick Desaulniers wrote: > (re-sending as plain text) > > On Wed, Apr 4, 2018 at 2:38 AM Greg KH wrote: > > There are known-bugs with building a kernel with clang right now (I > > pointed one out a few days ago about NULL checks being deleted from the > > clang output for no good reason, which really is scary for obvious > > reasons). > > Is this the thread you are referring to? > https://lkml.org/lkml/2018/3/27/1286 > > It's definitely something curious that I'll need to sit down and > investigate more. If there are other known instances, it would be good to > let me know. As Matthias mentioned elsewhere, it sounds like they're planning to implement -fno-delete-null-pointer-checks, which would presumably fix the above issue. Aside from the above-mentioned debugfs NULL checks, there was also another (seemingly valid) objtool warning: arch/x86/mm/pti.o: warning: objtool: pti_init() falls through to next function pti_user_pagetable_walk_pmd() I don't know if that one was also caused by removed NULL checks, but it's worth investigating. More details (and the .o file) here: https://lkml.kernel.org/r/20180319232255.GF37438@google.com -- Josh