From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3sJFZZ4FRvzDrJy for ; Tue, 23 Aug 2016 13:01:26 +1000 (AEST) Received: from pps.filterd (m0098410.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.11/8.16.0.11) with SMTP id u7N2wR7a073691 for ; Mon, 22 Aug 2016 23:01:24 -0400 Received: from e24smtp03.br.ibm.com (e24smtp03.br.ibm.com [32.104.18.24]) by mx0a-001b2d01.pphosted.com with ESMTP id 24y8310xak-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Mon, 22 Aug 2016 23:01:24 -0400 Received: from localhost by e24smtp03.br.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 23 Aug 2016 00:01:21 -0300 Received: from d24relay02.br.ibm.com (d24relay02.br.ibm.com [9.13.184.26]) by d24dlp01.br.ibm.com (Postfix) with ESMTP id 3D9E7352006C for ; Mon, 22 Aug 2016 23:00:58 -0400 (EDT) Received: from d24av05.br.ibm.com (d24av05.br.ibm.com [9.18.232.44]) by d24relay02.br.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id u7N31Jx933751442 for ; Tue, 23 Aug 2016 00:01:19 -0300 Received: from d24av05.br.ibm.com (localhost [127.0.0.1]) by d24av05.br.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id u7N31I4D008287 for ; Tue, 23 Aug 2016 00:01:19 -0300 From: Thiago Jung Bauermann To: Balbir Singh Cc: kexec@lists.infradead.org, Stewart Smith , Benjamin Herrenschmidt , Baoquan He , linuxppc-dev@lists.ozlabs.org, x86@kernel.org, "H. Peter Anvin" , linux-kernel@vger.kernel.org, Ingo Molnar , Paul Mackerras , Eric Biederman , Michael Ellerman , Thomas Gleixner , Dave Young , Andrew Morton , Vivek Goyal Subject: Re: [PATCH v5 04/13] powerpc: Factor out relocation code from module_64.c to elf_util_64.c. Date: Tue, 23 Aug 2016 00:01:15 -0300 In-Reply-To: <3ca4a2de-0d44-dbc6-b57b-c149d10b048f@gmail.com> References: <1470956898-5991-1-git-send-email-bauerman@linux.vnet.ibm.com> <4126991.2tm6WB17SD@hactar> <3ca4a2de-0d44-dbc6-b57b-c149d10b048f@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Message-Id: <4586138.sszncvQpYx@hactar> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Am Dienstag, 16 August 2016, 16:52:54 schrieb Balbir Singh: > On 16/08/16 09:25, Thiago Jung Bauermann wrote: > > Am Montag, 15 August 2016, 17:46:34 schrieb Balbir Singh: > >> On Thu, Aug 11, 2016 at 08:08:09PM -0300, Thiago Jung Bauermann wrote: > >>> +/** > >>> + * elf64_apply_relocate_add - apply 64 bit RELA relocations > >>> + * @elf_info: Support information for the ELF binary being > > > > relocated. > > > >>> + * @strtab: String table for the associated symbol > > > > table. > > > >>> + * @symindex: Section header index for the associated > > > > symbol table. > > > >>> + * @relsec: Section header index for the relocations to > > > > apply. > > > >>> + * @obj_name: The name of the ELF binary, for information > > > > messages. > > > >>> + */ > >>> +int elf64_apply_relocate_add(const struct elf_info *elf_info, > >>> + const char *strtab, unsigned int symindex, > >>> + unsigned int relsec, const char *obj_name) > >>> +{ > >>> + unsigned int i; > >>> + Elf64_Shdr *sechdrs = elf_info->sechdrs; > >>> + Elf64_Rela *rela = (void *)sechdrs[relsec].sh_addr; > >>> + Elf64_Sym *sym; > >>> + unsigned long *location; > >>> + unsigned long value; > >>> + > >> > >> For the relocatable kernel we expect only > >> > >> R_PPC64_RELATIVE > >> R_PPC64_NONE > >> R_PPC64_ADDR64 > >> > >> In the future we can use this to check/assert the usage of this > >> for the core kernel (vmlinux) when loaded. > >> > >> Did we check elf64_apply_relocate_add with zImage and vmlinux? > > > > kexec_file_load doesn't call call elf64_apply_relocate_add on the kernel > > image, it only uses it to relocate the purgatory. So whether it is > > loading a zImage or a vmlinux file, the function will work in the same > > way since the purgatory binary is the same regardless of the kernel > > image format. > Thanks for clarifying. > > > For the same reason, as it currently stands kexec_file_load can't check > > the relocation types used in the kernel image. But it is possible to > > add such a check/assertion in kexec_elf_64.c:build_elf_exec_info if we > > want. > > > > I tested kexec_file_load on both relocatable and non-relocatable vmlinux > > and it works correctly. > > > > I hadn't tested with zImage yet. I just did, and I had two problems: > > > > 1. For some reason, it has an INTERP segment. This patch series doesn't > > support loading program interpreters for ELF binaries, so > > kexec_elf_64.c:build_elf_exec_info refuses to load them. > > > > 2. If I disable the check for the INTERP segment, the zImage file loads > > correctly, but then I get an exception during reboot when loading the > > kexec image, right before jumping into the purgatory. I suspect this is > > because the LOAD segment has a virtual address of 0, and the first > > kernel is not coping well with that. But I still have to debug it > > further. > > > > Is there a reason for the zImage ELF header to request an interpreter > > and to have a virtual address of 0? > > Not that I am aware of. zImage on ppc64 BE is an ELF32 file. This patch set only supports loading ELF files of the same class as the kernel, so a 64 bit kernel can't load an ELF32 file. It would be possible to add such support, but it would be a new feature. The distros I was able to check on ppc64 LE and BE all use vmlinux. kexec-tools with kexec_load also doesn't support zImage. Do you think it is important to support zImage? -- []'s Thiago Jung Bauermann IBM Linux Technology Center