From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AB8JxZppZ0nTh281gp0k2nSBOGUvL3BKrEZ5LR2koaBUc1Yk+esHsAdlDAsQaM0YCgFfACorNkdy ARC-Seal: i=1; a=rsa-sha256; t=1525789964; cv=none; d=google.com; s=arc-20160816; b=P+5FsfURPWBd6IIdTnOd7hlgu8+EkzPLhOsb8p4lth4/BE9SQvw7N7Z2RzVx5DNFd2 rKndiGsJ/QgX/98KkPLobx6YrAkyFJ9rhcz9WRtIP39QgkuxEq9R7TxHf44ZqLZA5T/W cmnVJM7lhMo3Oey838a/2G7SrBwXt9rGyqH6HogEZ0kZUIKPtvAW0eNweAPjeS/kYUhY DMC4xDAY1uHDXqoxggblYH9H+EPlalb9Sgke4Rj3U8MduxTpNwaGwnhxSFQ3i5JQmCnL 2ORbG7uwQnmvUbuEr/uuzRzAnuObTcfKdnUmUAV9s3NbcIfVZRFWqphv/1idbUXWR97K w5zw== 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=U+CM46/Ow6t31F3ir6ECYPkVUlmtfk9m0lqEK2qoDII=; b=wVTD9Y8ESzK0l1/KC3Fiq7ZJQM3/EekvaduwqI1O/qJcRbyiAvGLvaYa+5D7CT55Om akWNtMF+ttUoJY3ICWPJNvf7cydQCIE0W/cno3N+x9PhSrP/9TJt0xSs/Utrg5DNcwPX VucOPA31TtYcc2gtUC1RzEQrY4mLQdB1UANnamS/Y2mjvYhp4ZzBiaWlVFmcxrcj6sis 5Zw9WJCpQCTh8qT7LQaZsgOXApD5yWr4pJgnLKRNX7grR9i0+5Cfdpd+fT6iJpb4Rho+ bvM+DONcex3+qUbE3cpxc4B1E9Dc5tW3RF7AQWlg389XAYxZYhpoWmrn4szxZUnppq7E ztUw== 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: Tue, 8 May 2018 09:32:41 -0500 From: Josh Poimboeuf To: Greg KH Cc: damian , peterz@infradead.org, linux-kernel@vger.kernel.org Subject: Re: Kernel build with gcc 8 a lot of warnings Message-ID: <20180508143241.5kz4poxcdhajjorl@treble> References: <20180505192112.GA18728@zrhn9910b> <20180507045453.leou4zypnlcck4vr@treble> <20180508055126.GA18724@kroah.com> <20180508133226.uwjbx44fwlxgyzu5@treble> <20180508142515.GA16111@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20180508142515.GA16111@kroah.com> User-Agent: NeoMutt/20180323 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-LABELS: =?utf-8?b?IlxcSW1wb3J0YW50Ig==?= X-GMAIL-THRID: =?utf-8?q?1599903094060891144?= X-GMAIL-MSGID: =?utf-8?q?1599906737569140237?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Tue, May 08, 2018 at 04:25:15PM +0200, Greg KH wrote: > On Tue, May 08, 2018 at 08:34:47AM -0500, Josh Poimboeuf wrote: > > On Tue, May 08, 2018 at 07:51:26AM +0200, Greg KH wrote: > > > On Sun, May 06, 2018 at 11:54:53PM -0500, Josh Poimboeuf wrote: > > > > 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. > > > > > > Any pointers to these patches? Archi linux just changed their default > > > compiler to gcc 8 and now I'm seeing this in my local builds :( > > > > I'm still dusting the code off, but this fixes most of the warnings. > > The rest of the code should hopefully be ready soon. > > > > From: Josh Poimboeuf > > Subject: [PATCH] objtool: Detect GCC 8 cold subfunctions > > > > GCC 8 moves a lot of unlikely code out of line to "cold" subfunctions in > > .text.unlikely. Properly detect the new subfunctions and treat them as > > extensions of the original functions. > > > > This fixes a bunch of warnings like: > > > > kernel/cgroup/cgroup.o: warning: objtool: parse_cgroup_root_flags()+0x33: sibling call from callable instruction with modified stack frame > > kernel/cgroup/cgroup.o: warning: objtool: cgroup_addrm_files()+0x290: sibling call from callable instruction with modified stack frame > > kernel/cgroup/cgroup.o: warning: objtool: cgroup_apply_control_enable()+0x25b: sibling call from callable instruction with modified stack frame > > kernel/cgroup/cgroup.o: warning: objtool: rebind_subsystems()+0x325: sibling call from callable instruction with modified stack frame > > > > Reported-by: Arnd Bergmann > > Signed-off-by: Josh Poimboeuf > > --- > > tools/objtool/check.c | 7 ++++--- > > tools/objtool/elf.c | 3 +++ > > tools/objtool/elf.h | 1 + > > 3 files changed, 8 insertions(+), 3 deletions(-) > > > > Much nicer, thanks for the patch, seems to build things "quieter" now. > For the other warnings, they are "safe" to ignore, right? It's just > objtool checking to see if all is ok, but the result should be fine no > matter what, right? Yeah, from what I can tell, there's nothing catastrophic in the rest of the warnings. Worst case, the ORC unwinder might get confused in a few places. -- Josh