From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ot0-f195.google.com ([74.125.82.195]:46474 "EHLO mail-ot0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751902AbeA0O0Y (ORCPT ); Sat, 27 Jan 2018 09:26:24 -0500 MIME-Version: 1.0 In-Reply-To: <20180127005554.GM26209@tassilo.jf.intel.com> References: <20171127213423.27218-1-andi@firstfloor.org> <20171127213423.27218-21-andi@firstfloor.org> <20180127005554.GM26209@tassilo.jf.intel.com> From: Arnd Bergmann Date: Sat, 27 Jan 2018 15:26:23 +0100 Message-ID: Subject: Re: [PATCH 20/21] Kbuild, lto: Add Link Time Optimization support Content-Type: text/plain; charset="UTF-8" Sender: linux-kbuild-owner@vger.kernel.org List-ID: To: Andi Kleen Cc: Andi Kleen , Linux Kernel Mailing List , the arch/x86 maintainers , samitolvanen@google.com, alxmtvv@gmail.com, Linux Kbuild mailing list , Masahiro Yamada , Andrew Morton On Sat, Jan 27, 2018 at 1:55 AM, Andi Kleen wrote: > On Sat, Jan 27, 2018 at 01:15:49AM +0100, Arnd Bergmann wrote: >> On Mon, Nov 27, 2017 at 10:34 PM, Andi Kleen wrote: >> > From: Andi Kleen >> > - Add a new LDFINAL variable that controls the final link >> > for vmlinux or module. In this case we call gcc-ld instead >> > of ld, to run the LTO step. >> >> When I tried this out on allmodconfig (following the lwn article), I ran into >> a number of warnings: > > Thanks for testing. Yes it's a known issue: during one module build > when modpost looks at the file it is still in LTO format, and > modpost doesn't understand the LTO symbol table. I had a patch > to teach it to it at some point, but it got lost somewhere. > The LLVM LTO patchkit has a different solution that actually > fixes the sequence to run modpost only after a LTO final link, > but I haven't gotten around to port that one. > > It seems to work already for the single file modules. Ok, I see. I've turned off that warning now for testing. What about this one: kallsyms failure: relative symbol value 0xffffffff81000000 out of range in relative mode I seem to get that all the time here, and have also disabled it for now, but it sounds important (and breaks the build). Arnd