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Thu, 16 Jul 2020 00:20:40 +0000 (GMT) Received: from b01ledav006.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 4F708AC05F; Thu, 16 Jul 2020 00:20:35 +0000 (GMT) Received: from morokweng.localdomain (unknown [9.163.73.114]) by b01ledav006.gho.pok.ibm.com (Postfix) with ESMTPS; Thu, 16 Jul 2020 00:20:34 +0000 (GMT) References: <159466074408.24747.10036072269371204890.stgit@hbathini.in.ibm.com> <159466093748.24747.4655547403463921814.stgit@hbathini.in.ibm.com> User-agent: mu4e 1.2.0; emacs 26.3 From: Thiago Jung Bauermann To: Hari Bathini Subject: Re: [PATCH v3 07/12] ppc64/kexec_file: add support to relocate purgatory In-reply-to: <159466093748.24747.4655547403463921814.stgit@hbathini.in.ibm.com> Date: Wed, 15 Jul 2020 21:20:31 -0300 Message-ID: <871rlc9upc.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=2020-07-15_12:2020-07-15, 2020-07-15 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 adultscore=0 lowpriorityscore=0 impostorscore=0 malwarescore=0 spamscore=0 mlxscore=0 phishscore=0 bulkscore=0 mlxlogscore=999 suspectscore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2007150175 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: kernel test robot , 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 Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Hari Bathini writes: > Right now purgatory implementation is only minimal. But if purgatory > code is to be enhanced to copy memory to the backup region and verify Can't the memcpy be done in asm? We have arch/powerpc/lib/memcpy_64.S for example, perhaps it could be linked in with the purgatory? > sha256 digest, relocations may have to be applied to the purgatory. Do we want to do the sha256 verification? My original patch series for kexec_file_load() had a purgatory in C from kexec-tools which did the sha256 verification but Michael Ellerman thought it was unnecessary and decided to use the simpler purgatory in asm from kexec-lite. As a result, this relocation processing became unnecessary. > So, add support to relocate purgatory in kexec_file_load system call > by setting up TOC pointer and applying RELA relocations as needed. If we do want to use a C purgatory, Michael Ellerman had suggested building it as a Position Independent Executable, which greatly reduces the number and types of relocations that are needed. See patches 4 and 9 here: https://lore.kernel.org/linuxppc-dev/1478748449-3894-1-git-send-email-bauerman@linux.vnet.ibm.com/ In the series above I hadn't converted x86 to PIE. If I had done that, possibly Dave Young's opinion would have been different. :-) If that's still not desirable, he suggested in that discussion lifting some code from x86 to generic code, which I implemented and would simplify this patch as well: https://lore.kernel.org/linuxppc-dev/5009580.5GxAkTrMYA@morokweng/ > Reported-by: kernel test robot > [lkp: In v1, 'struct mem_sym' was declared in parameter list] > Signed-off-by: Hari Bathini > --- > > v2 -> v3: > * Fixed get_toc_section() to return the section info that had relocations > applied, to calculate the correct toc pointer. > * Fixed how relocation value is converted to relative while applying > R_PPC64_REL64 & R_PPC64_REL32 relocations. > > v1 -> v2: > * Fixed wrong use of 'struct mem_sym' in local_entry_offset() as > reported by lkp. lkp report for reference: > - https://lore.kernel.org/patchwork/patch/1264421/ > > > arch/powerpc/kexec/file_load_64.c | 337 ++++++++++++++++++++++++++++++++ > arch/powerpc/purgatory/trampoline_64.S | 8 + > 2 files changed, 345 insertions(+) -- Thiago Jung Bauermann IBM Linux Technology Center