From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4FBB2C433EF for ; Thu, 26 May 2022 11:52:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242594AbiEZLwk (ORCPT ); Thu, 26 May 2022 07:52:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58220 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238114AbiEZLwh (ORCPT ); Thu, 26 May 2022 07:52:37 -0400 Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 596A3D028A for ; Thu, 26 May 2022 04:52:36 -0700 (PDT) Received: from pps.filterd (m0098414.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.17.1.5/8.17.1.5) with ESMTP id 24QBhuvC022369; Thu, 26 May 2022 11:51:13 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=date : from : subject : to : cc : references : in-reply-to : mime-version : message-id : content-type : content-transfer-encoding; s=pp1; bh=ynPlZyBaNKCcm0CiJDgThFxPrRBhCGbeVI8OA7nVc8o=; b=sGJ6FYY0ksdqK5Gilghmv3kKnIMhcL/jN7NS24uSiR2jRRy84JL2psZgB7bPAMz4ALRN 7YMZGsiA0d0WfL8ZMrYHrNAwbpoU1fH945DGoKYYYt7J/qDKlV9FY35iN0g13TlfOAtL LK8UAckdDHDhw8frfEfd1pO2Jdkm5FAt5SJMVl8BWEdXVhJXHrbdcmHa3Dol+V/8Hom3 xgtOdK1uMcP2IGsI3u8lCUqQYqPyISVeAoPPOVQrtf5ib0MCGs7MLH3qs+uSBJl7zryh Ny+BKUSWhZiD7yiwEm8cx+7pVWPb2bLrlosLdmbuh9ZlhnthOLKtipz7GAv9gIzNRzIi bg== Received: from pps.reinject (localhost [127.0.0.1]) by mx0b-001b2d01.pphosted.com (PPS) with ESMTPS id 3ga8x583xn-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 26 May 2022 11:51:13 +0000 Received: from m0098414.ppops.net (m0098414.ppops.net [127.0.0.1]) by pps.reinject (8.17.1.5/8.17.1.5) with ESMTP id 24QBjwD7029256; Thu, 26 May 2022 11:51:12 GMT Received: from ppma03ams.nl.ibm.com (62.31.33a9.ip4.static.sl-reverse.com [169.51.49.98]) by mx0b-001b2d01.pphosted.com (PPS) with ESMTPS id 3ga8x583wr-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 26 May 2022 11:51:12 +0000 Received: from pps.filterd (ppma03ams.nl.ibm.com [127.0.0.1]) by ppma03ams.nl.ibm.com (8.16.1.2/8.16.1.2) with SMTP id 24QBmWbP024191; Thu, 26 May 2022 11:51:11 GMT Received: from b06cxnps3074.portsmouth.uk.ibm.com (d06relay09.portsmouth.uk.ibm.com [9.149.109.194]) by ppma03ams.nl.ibm.com with ESMTP id 3g93ux2j5j-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 26 May 2022 11:51:10 +0000 Received: from d06av21.portsmouth.uk.ibm.com (d06av21.portsmouth.uk.ibm.com [9.149.105.232]) by b06cxnps3074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 24QBp88545678892 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 26 May 2022 11:51:08 GMT Received: from d06av21.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 985C352050; Thu, 26 May 2022 11:51:08 +0000 (GMT) Received: from localhost (unknown [9.43.88.34]) by d06av21.portsmouth.uk.ibm.com (Postfix) with ESMTP id EFD345204F; Thu, 26 May 2022 11:51:07 +0000 (GMT) Date: Thu, 26 May 2022 17:21:02 +0530 From: "Naveen N. Rao" Subject: Re: [RFC PATCH 1/4] objtool: Add --mnop as an option to --mcount To: Peter Zijlstra Cc: "aik@ozlabs.ru" , Christophe Leroy , "jpoimboe@redhat.com" , "linux-kernel@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" , "mbenes@suse.cz" , "mpe@ellerman.id.au" , "rostedt@goodmis.org" , Sathvika Vasireddy References: <20220523175548.922671-1-sv@linux.ibm.com> <20220523175548.922671-2-sv@linux.ibm.com> <26c7bfc8-3089-034a-70c0-8857d7cd3a99@csgroup.eu> <1653386854.o7nss9hzc9.naveen@linux.ibm.com> <1653388084.w21cyb07gc.naveen@linux.ibm.com> In-Reply-To: MIME-Version: 1.0 User-Agent: astroid/4d6b06ad (https://github.com/astroidmail/astroid) Message-Id: <1653564857.f06fbbl3vg.naveen@linux.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable X-TM-AS-GCONF: 00 X-Proofpoint-GUID: VqH70ghrPi37x42qUQ2pBbdsMKAQow1X X-Proofpoint-ORIG-GUID: Peo3i2FCPjcZkXQWaKkjXDOKpPv7Iwnc X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.874,Hydra:6.0.486,FMLib:17.11.64.514 definitions=2022-05-26_06,2022-05-25_02,2022-02-23_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 phishscore=0 clxscore=1015 suspectscore=0 bulkscore=0 mlxlogscore=654 spamscore=0 adultscore=0 impostorscore=0 malwarescore=0 priorityscore=1501 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2204290000 definitions=main-2205260054 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Peter Zijlstra wrote: > On Tue, May 24, 2022 at 04:01:48PM +0530, Naveen N. Rao wrote: >=20 >> We need to know for sure either way. Nop'ing out the _mcount locations a= t >> boot allows us to discover existing long branch trampolines. If we want = to >> avoid it, we need to note down those locations during build time. >>=20 >> Do you have a different approach in mind? >=20 > If you put _mcount in a separate section then the compiler cannot tell > where it is and is forced to always emit a long branch trampoline. >=20 > Does that help? That's an interesting thought. Depending on the type of trampoline the=20 compiler emits, I might be able to use this approach. We will still need=20 objtool on powerpc so that we can note down those trampoline locations. Thanks, Naveen