From: Hari Bathini <hbathini@linux.ibm.com> To: Thiago Jung Bauermann <bauerman@linux.ibm.com> Cc: kernel test robot <lkp@intel.com>, Pingfan Liu <piliu@redhat.com>, Nayna Jain <nayna@linux.ibm.com>, Kexec-ml <kexec@lists.infradead.org>, Mahesh J Salgaonkar <mahesh@linux.ibm.com>, Mimi Zohar <zohar@linux.ibm.com>, lkml <linux-kernel@vger.kernel.org>, linuxppc-dev <linuxppc-dev@ozlabs.org>, Sourabh Jain <sourabhjain@linux.ibm.com>, Petr Tesarik <ptesarik@suse.cz>, Andrew Morton <akpm@linux-foundation.org>, Dave Young <dyoung@redhat.com>, Vivek Goyal <vgoyal@redhat.com>, Eric Biederman <ebiederm@xmission.com> Subject: Re: [PATCH v3 07/12] ppc64/kexec_file: add support to relocate purgatory Date: Fri, 17 Jul 2020 02:41:42 +0530 [thread overview] Message-ID: <6f64a18a-352e-fdec-c902-45aefc31cc0a@linux.ibm.com> (raw) In-Reply-To: <871rlc9upc.fsf@morokweng.localdomain> On 16/07/20 5:50 am, Thiago Jung Bauermann wrote: > > Hari Bathini <hbathini@linux.ibm.com> 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? I wanted to avoid touching common code to make it work for purgatory for now. > >> 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. kexec_file_load could as well be used without IMA or secureboot. With sha256 digest calculated anyway, verifying it would make sense to accommodate that case as well. > >> 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/ > Agreed. But I prefer to work on PIE and/or moving common relocation_add code for x86 & s390 to generic code later when I try to build on these purgatory changes. So, a separate series later to rework purgatory with the things you mentioned above sounds ok? Thanks Hari
WARNING: multiple messages have this Message-ID (diff)
From: Hari Bathini <hbathini@linux.ibm.com> To: Thiago Jung Bauermann <bauerman@linux.ibm.com> Cc: kernel test robot <lkp@intel.com>, Pingfan Liu <piliu@redhat.com>, Petr Tesarik <ptesarik@suse.cz>, Nayna Jain <nayna@linux.ibm.com>, Kexec-ml <kexec@lists.infradead.org>, Mahesh J Salgaonkar <mahesh@linux.ibm.com>, Mimi Zohar <zohar@linux.ibm.com>, lkml <linux-kernel@vger.kernel.org>, linuxppc-dev <linuxppc-dev@ozlabs.org>, Sourabh Jain <sourabhjain@linux.ibm.com>, Andrew Morton <akpm@linux-foundation.org>, Dave Young <dyoung@redhat.com>, Vivek Goyal <vgoyal@redhat.com>, Eric Biederman <ebiederm@xmission.com> Subject: Re: [PATCH v3 07/12] ppc64/kexec_file: add support to relocate purgatory Date: Fri, 17 Jul 2020 02:41:42 +0530 [thread overview] Message-ID: <6f64a18a-352e-fdec-c902-45aefc31cc0a@linux.ibm.com> (raw) In-Reply-To: <871rlc9upc.fsf@morokweng.localdomain> On 16/07/20 5:50 am, Thiago Jung Bauermann wrote: > > Hari Bathini <hbathini@linux.ibm.com> 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? I wanted to avoid touching common code to make it work for purgatory for now. > >> 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. kexec_file_load could as well be used without IMA or secureboot. With sha256 digest calculated anyway, verifying it would make sense to accommodate that case as well. > >> 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/ > Agreed. But I prefer to work on PIE and/or moving common relocation_add code for x86 & s390 to generic code later when I try to build on these purgatory changes. So, a separate series later to rework purgatory with the things you mentioned above sounds ok? Thanks Hari
next prev parent reply other threads:[~2020-07-16 21:13 UTC|newest] Thread overview: 125+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-07-13 17:20 [PATCH v3 00/12] ppc64: enable kdump support for kexec_file_load syscall Hari Bathini 2020-07-13 17:20 ` Hari Bathini 2020-07-13 17:20 ` Hari Bathini 2020-07-13 17:20 ` [PATCH v3 01/12] kexec_file: allow archs to handle special regions while locating memory hole Hari Bathini 2020-07-13 17:20 ` Hari Bathini 2020-07-13 17:20 ` Hari Bathini 2020-07-14 21:00 ` Thiago Jung Bauermann 2020-07-14 21:00 ` Thiago Jung Bauermann 2020-07-14 21:00 ` Thiago Jung Bauermann 2020-07-13 17:21 ` [PATCH v3 02/12] powerpc/kexec_file: mark PPC64 specific code Hari Bathini 2020-07-13 17:21 ` Hari Bathini 2020-07-13 17:21 ` Hari Bathini 2020-07-16 1:49 ` Thiago Jung Bauermann 2020-07-16 1:49 ` Thiago Jung Bauermann 2020-07-16 1:49 ` Thiago Jung Bauermann 2020-07-17 4:46 ` Hari Bathini 2020-07-17 4:46 ` Hari Bathini 2020-07-17 4:46 ` Hari Bathini 2020-07-17 18:34 ` Thiago Jung Bauermann 2020-07-17 18:34 ` Thiago Jung Bauermann 2020-07-13 17:21 ` [PATCH v3 03/12] powerpc/kexec_file: add helper functions for getting memory ranges Hari Bathini 2020-07-13 17:21 ` Hari Bathini 2020-07-13 17:21 ` Hari Bathini 2020-07-14 23:49 ` Thiago Jung Bauermann 2020-07-14 23:49 ` Thiago Jung Bauermann 2020-07-14 23:49 ` Thiago Jung Bauermann 2020-07-16 21:08 ` Hari Bathini 2020-07-16 21:08 ` Hari Bathini 2020-07-17 4:32 ` Hari Bathini 2020-07-17 4:32 ` Hari Bathini 2020-07-17 4:32 ` Hari Bathini 2020-07-17 20:00 ` Hari Bathini 2020-07-17 20:00 ` Hari Bathini 2020-07-13 17:21 ` [PATCH v3 04/12] ppc64/kexec_file: avoid stomping memory used by special regions Hari Bathini 2020-07-13 17:21 ` Hari Bathini 2020-07-13 17:21 ` Hari Bathini 2020-07-15 2:39 ` Thiago Jung Bauermann 2020-07-15 2:39 ` Thiago Jung Bauermann 2020-07-15 2:39 ` Thiago Jung Bauermann 2020-07-16 5:58 ` Thiago Jung Bauermann 2020-07-16 5:58 ` Thiago Jung Bauermann 2020-07-16 5:58 ` Thiago Jung Bauermann 2020-07-16 21:09 ` Hari Bathini 2020-07-16 21:09 ` Hari Bathini 2020-07-16 21:59 ` Thiago Jung Bauermann 2020-07-16 21:59 ` Thiago Jung Bauermann 2020-07-16 21:59 ` Thiago Jung Bauermann 2020-07-13 17:21 ` [PATCH v3 05/12] powerpc/drmem: make lmb walk a bit more flexible Hari Bathini 2020-07-13 17:21 ` Hari Bathini 2020-07-13 17:21 ` Hari Bathini 2020-07-15 3:50 ` Thiago Jung Bauermann 2020-07-15 3:50 ` Thiago Jung Bauermann 2020-07-15 3:50 ` Thiago Jung Bauermann 2020-07-16 21:09 ` Hari Bathini 2020-07-16 21:09 ` Hari Bathini 2020-07-16 22:01 ` Thiago Jung Bauermann 2020-07-16 22:01 ` Thiago Jung Bauermann 2020-07-16 22:01 ` Thiago Jung Bauermann 2020-07-13 17:22 ` [PATCH v3 06/12] ppc64/kexec_file: restrict memory usage of kdump kernel Hari Bathini 2020-07-13 17:22 ` Hari Bathini 2020-07-13 17:22 ` Hari Bathini 2020-07-15 22:52 ` Thiago Jung Bauermann 2020-07-15 22:52 ` Thiago Jung Bauermann 2020-07-15 22:52 ` Thiago Jung Bauermann 2020-07-16 21:10 ` Hari Bathini 2020-07-16 21:10 ` Hari Bathini 2020-07-16 22:03 ` Thiago Jung Bauermann 2020-07-16 22:03 ` Thiago Jung Bauermann 2020-07-16 22:03 ` Thiago Jung Bauermann 2020-07-17 4:17 ` Hari Bathini 2020-07-17 4:17 ` Hari Bathini 2020-07-13 17:22 ` [PATCH v3 07/12] ppc64/kexec_file: add support to relocate purgatory Hari Bathini 2020-07-13 17:22 ` Hari Bathini 2020-07-13 17:22 ` Hari Bathini 2020-07-16 0:20 ` Thiago Jung Bauermann 2020-07-16 0:20 ` Thiago Jung Bauermann 2020-07-16 0:20 ` Thiago Jung Bauermann 2020-07-16 21:11 ` Hari Bathini [this message] 2020-07-16 21:11 ` Hari Bathini 2020-07-16 22:12 ` Thiago Jung Bauermann 2020-07-16 22:12 ` Thiago Jung Bauermann 2020-07-16 22:12 ` Thiago Jung Bauermann 2020-07-13 17:22 ` [PATCH v3 08/12] ppc64/kexec_file: setup the stack for purgatory Hari Bathini 2020-07-13 17:22 ` Hari Bathini 2020-07-13 17:22 ` Hari Bathini 2020-07-16 0:35 ` Thiago Jung Bauermann 2020-07-16 0:35 ` Thiago Jung Bauermann 2020-07-16 0:35 ` Thiago Jung Bauermann 2020-07-16 1:40 ` Thiago Jung Bauermann 2020-07-16 1:40 ` Thiago Jung Bauermann 2020-07-16 1:40 ` Thiago Jung Bauermann 2020-07-13 17:22 ` [PATCH v3 09/12] ppc64/kexec_file: setup backup region for kdump kernel Hari Bathini 2020-07-13 17:22 ` Hari Bathini 2020-07-13 17:22 ` Hari Bathini 2020-07-16 1:38 ` Thiago Jung Bauermann 2020-07-16 1:38 ` Thiago Jung Bauermann 2020-07-16 1:38 ` Thiago Jung Bauermann 2020-07-16 21:10 ` Hari Bathini 2020-07-16 21:10 ` Hari Bathini 2020-07-16 22:06 ` Thiago Jung Bauermann 2020-07-16 22:06 ` Thiago Jung Bauermann 2020-07-16 22:06 ` Thiago Jung Bauermann 2020-07-13 17:23 ` [PATCH v3 10/12] ppc64/kexec_file: prepare elfcore header for crashing kernel Hari Bathini 2020-07-13 17:23 ` Hari Bathini 2020-07-13 17:23 ` Hari Bathini 2020-07-16 2:22 ` Thiago Jung Bauermann 2020-07-16 2:22 ` Thiago Jung Bauermann 2020-07-16 2:22 ` Thiago Jung Bauermann 2020-07-16 21:07 ` Hari Bathini 2020-07-16 21:07 ` Hari Bathini 2020-07-16 21:57 ` Thiago Jung Bauermann 2020-07-16 21:57 ` Thiago Jung Bauermann 2020-07-16 21:57 ` Thiago Jung Bauermann 2020-07-13 17:23 ` [PATCH v3 11/12] ppc64/kexec_file: add appropriate regions for memory reserve map Hari Bathini 2020-07-13 17:23 ` Hari Bathini 2020-07-13 17:23 ` Hari Bathini 2020-07-16 2:27 ` Thiago Jung Bauermann 2020-07-16 2:27 ` Thiago Jung Bauermann 2020-07-16 2:27 ` Thiago Jung Bauermann 2020-07-13 17:23 ` [PATCH v3 12/12] ppc64/kexec_file: fix kexec load failure with lack of memory hole Hari Bathini 2020-07-13 17:23 ` Hari Bathini 2020-07-13 17:23 ` Hari Bathini 2020-07-16 5:43 ` Thiago Jung Bauermann 2020-07-16 5:43 ` Thiago Jung Bauermann 2020-07-16 5:43 ` Thiago Jung Bauermann
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