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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Mon, 2 Mar 2020 17:17:21 -0000 Received: from d06av23.portsmouth.uk.ibm.com (d06av23.portsmouth.uk.ibm.com [9.149.105.59]) by b06cxnps4074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 022HHK3l54722608 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 2 Mar 2020 17:17:21 GMT Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id E35E3A4051; Mon, 2 Mar 2020 17:17:20 +0000 (GMT) Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 7EC02A404D; Mon, 2 Mar 2020 17:17:20 +0000 (GMT) Received: from localhost (unknown [9.199.48.41]) by d06av23.portsmouth.uk.ibm.com (Postfix) with ESMTP; Mon, 2 Mar 2020 17:17:20 +0000 (GMT) Date: Mon, 02 Mar 2020 22:47:18 +0530 From: "Naveen N. Rao" Subject: Re: eh_frame confusion To: Rasmus Villemoes , Segher Boessenkool , Michael Ellerman Cc: Linux Kbuild mailing list , LKML , "linuxppc-dev@lists.ozlabs.org" 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 User-Agent: astroid/v0.15-13-gb675b421 (https://github.com/astroidmail/astroid) Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8BIT X-TM-AS-GCONF: 00 x-cbid: 20030217-0012-0000-0000-0000038C5B92 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 20030217-0013-0000-0000-000021C90F71 Message-Id: <1583169014.zvau4om8mi.naveen@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.572 definitions=2020-03-02_06:2020-03-02,2020-03-02 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxlogscore=883 clxscore=1015 lowpriorityscore=0 malwarescore=0 adultscore=0 suspectscore=0 priorityscore=1501 spamscore=0 mlxscore=0 bulkscore=0 phishscore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2003020115 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.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