From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:16465 "EHLO mx0b-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727261AbgCBRR3 (ORCPT ); Mon, 2 Mar 2020 12:17:29 -0500 Received: from pps.filterd (m0127361.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 022GwefA001325 for ; Mon, 2 Mar 2020 12:17:28 -0500 Received: from e06smtp03.uk.ibm.com (e06smtp03.uk.ibm.com [195.75.94.99]) by mx0a-001b2d01.pphosted.com with ESMTP id 2yfkn9qgra-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Mon, 02 Mar 2020 12:17:27 -0500 Received: from localhost by e06smtp03.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 2 Mar 2020 17:17:25 -0000 Date: Mon, 02 Mar 2020 22:47:18 +0530 From: "Naveen N. Rao" Subject: Re: eh_frame confusion References: <3b00b45f-74b5-13e3-9a98-c3d6b3bb7286@rasmusvillemoes.dk> <20200302124442.GI22482@gate.crashing.org> In-Reply-To: <20200302124442.GI22482@gate.crashing.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8BIT Message-Id: <1583169014.zvau4om8mi.naveen@linux.ibm.com> Sender: linux-kbuild-owner@vger.kernel.org List-ID: To: Rasmus Villemoes , Segher Boessenkool , Michael Ellerman Cc: Linux Kbuild mailing list , LKML , "linuxppc-dev@lists.ozlabs.org" Segher Boessenkool wrote: > On Mon, Mar 02, 2020 at 11:56:05AM +0100, Rasmus Villemoes wrote: >> I'm building a ppc32 kernel, and noticed that after upgrading from gcc-7 >> to gcc-8 all object files now end up having .eh_frame section. > > Since GCC 8, we enable -fasynchronous-unwind-tables by default for > PowerPC. See https://gcc.gnu.org/r259298 . > >> For >> vmlinux, that's not a problem, because they all get discarded in >> arch/powerpc/kernel/vmlinux.lds.S . However, they stick around in >> modules, which doesn't seem to be useful - given that everything worked >> just fine with gcc-7, and I don't see anything in the module loader that >> handles .eh_frame. > > It is useful for debugging. Not many people debug the kernel like this, > of course. I'm trying to understand if we need that. Other architectures seems to pass -fasynchronous-unwind-tables only for the vdso, but disable it for the kernel build. I suppose we can do the same. If using -fno-asynchronous-unwind-tables, would crash/perf have problems? - Naveen