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 X-Spam-Level: X-Spam-Status: No, score=-4.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C4A94C433E1 for ; Thu, 16 Jul 2020 22:03:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A56EB2076D for ; Thu, 16 Jul 2020 22:03:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726229AbgGPWDZ (ORCPT ); Thu, 16 Jul 2020 18:03:25 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:40676 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726002AbgGPWDY (ORCPT ); Thu, 16 Jul 2020 18:03:24 -0400 Received: from pps.filterd (m0098394.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 06GM2Wtq059669; Thu, 16 Jul 2020 18:03:17 -0400 Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com with ESMTP id 32a45by6mx-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 16 Jul 2020 18:03:17 -0400 Received: from m0098394.ppops.net (m0098394.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.36/8.16.0.36) with SMTP id 06GM3H0N062253; Thu, 16 Jul 2020 18:03:17 -0400 Received: from ppma01wdc.us.ibm.com (fd.55.37a9.ip4.static.sl-reverse.com [169.55.85.253]) by mx0a-001b2d01.pphosted.com with ESMTP id 32a45by6mh-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 16 Jul 2020 18:03:17 -0400 Received: from pps.filterd (ppma01wdc.us.ibm.com [127.0.0.1]) by ppma01wdc.us.ibm.com (8.16.0.42/8.16.0.42) with SMTP id 06GLjTAM023747; Thu, 16 Jul 2020 22:03:15 GMT Received: from b03cxnp08027.gho.boulder.ibm.com (b03cxnp08027.gho.boulder.ibm.com [9.17.130.19]) by ppma01wdc.us.ibm.com with ESMTP id 3275294272-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 16 Jul 2020 22:03:15 +0000 Received: from b03ledav006.gho.boulder.ibm.com (b03ledav006.gho.boulder.ibm.com [9.17.130.237]) by b03cxnp08027.gho.boulder.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 06GM3CuA31851182 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 16 Jul 2020 22:03:12 GMT Received: from b03ledav006.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 79F82C6062; Thu, 16 Jul 2020 22:03:14 +0000 (GMT) Received: from b03ledav006.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 4DAC1C606C; Thu, 16 Jul 2020 22:03:11 +0000 (GMT) Received: from morokweng.localdomain (unknown [9.163.8.110]) by b03ledav006.gho.boulder.ibm.com (Postfix) with ESMTPS; Thu, 16 Jul 2020 22:03:10 +0000 (GMT) References: <159466074408.24747.10036072269371204890.stgit@hbathini.in.ibm.com> <159466091925.24747.6840028682768745598.stgit@hbathini.in.ibm.com> <87365s9ysj.fsf@morokweng.localdomain> User-agent: mu4e 1.2.0; emacs 26.3 From: Thiago Jung Bauermann To: Hari Bathini Cc: Pingfan Liu , Nayna Jain , Kexec-ml , Mahesh J Salgaonkar , Mimi Zohar , lkml , linuxppc-dev , Sourabh Jain , Petr Tesarik , Andrew Morton , Dave Young , Vivek Goyal , Eric Biederman Subject: Re: [PATCH v3 06/12] ppc64/kexec_file: restrict memory usage of kdump kernel In-reply-to: Date: Thu, 16 Jul 2020 19:03:08 -0300 Message-ID: <875zance3n.fsf@morokweng.localdomain> MIME-Version: 1.0 Content-Type: text/plain X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235,18.0.687 definitions=2020-07-16_11:2020-07-16,2020-07-16 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_spam_definite policy=outbound score=100 phishscore=0 spamscore=100 priorityscore=1501 lowpriorityscore=0 suspectscore=0 impostorscore=0 mlxscore=100 bulkscore=0 adultscore=0 malwarescore=0 mlxlogscore=-1000 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2007160142 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hari Bathini writes: > On 16/07/20 4:22 am, Thiago Jung Bauermann wrote: >> >> Hari Bathini writes: >> > > > >>> +/** >>> + * get_node_path - Get the full path of the given node. >>> + * @dn: Node. >>> + * @path: Updated with the full path of the node. >>> + * >>> + * Returns nothing. >>> + */ >>> +static void get_node_path(struct device_node *dn, char *path) >>> +{ >>> + if (!dn) >>> + return; >>> + >>> + get_node_path(dn->parent, path); >> >> Is it ok to do recursion in the kernel? In this case I believe it's not >> problematic since the maximum call depth will be the maximum depth of a >> device tree node which shouldn't be too much. Also, there are no local >> variables in this function. But I thought it was worth mentioning. > > You are right. We are better off avoiding the recursion here. Will > change it to an iterative version instead. Ok. >>> + * each representing a memory range. >>> + */ >>> + ranges = (len >> 2) / (n_mem_addr_cells + n_mem_size_cells); >>> + >>> + for (i = 0; i < ranges; i++) { >>> + base = of_read_number(prop, n_mem_addr_cells); >>> + prop += n_mem_addr_cells; >>> + end = base + of_read_number(prop, n_mem_size_cells) - 1; > > prop is not used after the above. > >> You need to `prop += n_mem_size_cells` here. > > But yeah, adding it would make it look complete in some sense.. Isn't it used in the next iteration of the loop? -- Thiago Jung Bauermann IBM Linux Technology Center