From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752015AbeEGEzH (ORCPT ); Mon, 7 May 2018 00:55:07 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:33668 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751908AbeEGEy4 (ORCPT ); Mon, 7 May 2018 00:54:56 -0400 Date: Sun, 6 May 2018 23:54:53 -0500 From: Josh Poimboeuf To: damian Cc: peterz@infradead.org, linux-kernel@vger.kernel.org Subject: Re: Kernel build with gcc 8 a lot of warnings Message-ID: <20180507045453.leou4zypnlcck4vr@treble> References: <20180505192112.GA18728@zrhn9910b> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20180505192112.GA18728@zrhn9910b> User-Agent: NeoMutt/20180323 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, May 05, 2018 at 09:21:12PM +0200, damian wrote: > Helllo together, > > Hello everybody, > > is something special to note when kernel build with gcc 8? I receive various warnings from the objtool: > With GCC 7 works all fine. > > kernel/cgroup/cgroup.o: warning: objtool: parse_cgroup_root_flags()+0x40: sibling call from callable instruction with modified stack frame > kernel/cgroup/cgroup.o: warning: objtool: cgroup_addrm_files()+0x2a3: sibling call from callable instruction with modified stack frame > kernel/cgroup/cgroup.o: warning: objtool: cgroup_apply_control_enable()+0x20b: sibling call from callable instruction with modified stack frame > kernel/cgroup/cgroup.o: warning: objtool: rebind_subsystems()+0x296: sibling call from callable instruction with modified stack frame > kernel/cgroup/cgroup.o: warning: objtool: cgroup_sk_alloc_disable()+0x10: sibling call from callable instruction with modified stack frame > kernel/cgroup/cgroup.o: warning: objtool: parse_cgroup_root_flags.cold.45()+0xa: call without frame pointer save/setup > kernel/cgroup/cgroup.o: warning: objtool: cgroup_addrm_files.cold.46()+0x17: call without frame pointer save/setup > kernel/cgroup/cgroup.o: warning: objtool: cgroup_apply_control_enable.cold.47()+0x24: call without frame pointer save/setup > kernel/cgroup/cgroup.o: warning: objtool: rebind_subsystems.cold.48()+0x10: call without frame pointer save/setup > kernel/cgroup/cgroup.o: warning: objtool: cgroup_sk_alloc_disable.cold.49()+0x7: call without frame pointer save/setup > CC kernel/cgroup/stat.o > CC [M] arch/x86/kvm/../../../virt/kvm/kvm_main.o > arch/x86/kernel/acpi/boot.o: warning: objtool: acpi_register_lapic()+0x10: sibling call from callable instruction with modified stack frame > arch/x86/kernel/acpi/boot.o: warning: objtool: acpi_map_cpu()+0x2c: sibling call from callable instruction with modified stack frame > arch/x86/kernel/acpi/boot.o: warning: objtool: acpi_register_lapic.cold.6()+0x7: call without frame pointer save/setup > arch/x86/kernel/acpi/boot.o: warning: objtool: acpi_map_cpu.cold.7()+0x7: call without frame pointer save/setup Thanks, this is a known issue with GCC 8 that I haven't gotten a chance to fix yet. They're related to the fact that GCC 8 is splitting out 'unlikely' code into 'cold' subfunctions in .text.unlikely. I've got some old patches that fix it. Now that GCC 8 is out, I'll need get the patches dusted off and cleaned up for merging. -- Josh