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Sat, 25 Jul 2020 00:33:04 +0000 (GMT) Received: from b03ledav004.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A9AA47805C; Sat, 25 Jul 2020 00:33:01 +0000 (GMT) Received: from morokweng.localdomain (unknown [9.163.38.252]) by b03ledav004.gho.boulder.ibm.com (Postfix) with ESMTPS; Sat, 25 Jul 2020 00:33:01 +0000 (GMT) References: <159524918900.20855.17709718993097359220.stgit@hbathini.in.ibm.com> <159524954805.20855.1164928096364700614.stgit@hbathini.in.ibm.com> <875zad6ajx.fsf@morokweng.localdomain> <77c606da-8eb2-d831-147b-a204b498c7d7@linux.ibm.com> User-agent: mu4e 1.2.0; emacs 26.3 From: Thiago Jung Bauermann To: Hari Bathini Subject: Re: [PATCH v4 06/12] ppc64/kexec_file: restrict memory usage of kdump kernel In-reply-to: <77c606da-8eb2-d831-147b-a204b498c7d7@linux.ibm.com> Date: Fri, 24 Jul 2020 21:32:59 -0300 Message-ID: <874kpwsabo.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=2020-07-24_10:2020-07-24, 2020-07-24 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 lowpriorityscore=0 mlxlogscore=999 mlxscore=0 suspectscore=0 malwarescore=0 adultscore=0 phishscore=0 spamscore=0 clxscore=1015 priorityscore=1501 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2007240164 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Pingfan Liu , Petr Tesarik , Nayna Jain , Kexec-ml , Mahesh J Salgaonkar , Mimi Zohar , lkml , linuxppc-dev , Sourabh Jain , Andrew Morton , Dave Young , Vivek Goyal , Eric Biederman Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Hari Bathini writes: > On 24/07/20 5:36 am, Thiago Jung Bauermann wrote: >> >> Hari Bathini writes: >> >>> Kdump kernel, used for capturing the kernel core image, is supposed >>> to use only specific memory regions to avoid corrupting the image to >>> be captured. The regions are crashkernel range - the memory reserved >>> explicitly for kdump kernel, memory used for the tce-table, the OPAL >>> region and RTAS region as applicable. Restrict kdump kernel memory >>> to use only these regions by setting up usable-memory DT property. >>> Also, tell the kdump kernel to run at the loaded address by setting >>> the magic word at 0x5c. >>> >>> Signed-off-by: Hari Bathini >>> Tested-by: Pingfan Liu >>> --- >>> >>> v3 -> v4: >>> * Updated get_node_path() to be an iterative function instead of a >>> recursive one. >>> * Added comment explaining why low memory is added to kdump kernel's >>> usable memory ranges though it doesn't fall in crashkernel region. >>> * For correctness, added fdt_add_mem_rsv() for the low memory being >>> added to kdump kernel's usable memory ranges. >> >> Good idea. >> >>> * Fixed prop pointer update in add_usable_mem_property() and changed >>> duple to tuple as suggested by Thiago. >> >> >> >>> +/** >>> + * get_node_pathlen - Get the full path length of the given node. >>> + * @dn: Node. >>> + * >>> + * Also, counts '/' at the end of the path. >>> + * For example, /memory@0 will be "/memory@0/\0" => 11 bytes. >> >> Wouldn't this function return 10 in the case of /memory@0? > > Actually, it does return 11. +1 while returning is for counting %NUL. > On top of that we count an extra '/' for root node.. so, it ends up as 11. > ('/'memory@0'/''\0'). Note the extra '/' before '\0'. Let me handle root node > separately. That should avoid the confusion. Ah, that is true. I forgot to count the iteration for the root node. Sorry about that. -- Thiago Jung Bauermann IBM Linux Technology Center