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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_PASS autolearn=ham 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 32195C0044C for ; Thu, 1 Nov 2018 15:18:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D7CDA205F4 for ; Thu, 1 Nov 2018 15:18:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D7CDA205F4 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728458AbeKBAVs (ORCPT ); Thu, 1 Nov 2018 20:21:48 -0400 Received: from mx2.suse.de ([195.135.220.15]:44856 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728117AbeKBAVs (ORCPT ); Thu, 1 Nov 2018 20:21:48 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 6497AAC5E; Thu, 1 Nov 2018 15:18:22 +0000 (UTC) Date: Thu, 1 Nov 2018 16:18:20 +0100 (CET) From: Miroslav Benes To: Jessica Yu cc: Will Deacon , Torsten Duwe , Catalin Marinas , Julien Thierry , Steven Rostedt , Josh Poimboeuf , Ingo Molnar , Ard Biesheuvel , Arnd Bergmann , AKASHI Takahiro , Petr Mladek , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, live-patching@vger.kernel.org Subject: Re: [PATCH v2] arm64/module: use mod->klp_info section header information for livepatch modules In-Reply-To: <20181030131910.zuqw523rq4pi7apb@linux-8ccs> Message-ID: References: <20181001140910.086E768BC7@newverein.lst.de> <20181001141652.5478C68BE1@newverein.lst.de> <20181023175553.gaobskk26koft6s2@linux-8ccs> <20181026172500.g65bl2p7cvey3qsx@linux-8ccs> <20181029152834.GA16289@arm.com> <20181030131910.zuqw523rq4pi7apb@linux-8ccs> User-Agent: Alpine 2.21 (LSU 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > >Does this mean we can drop the plt pointer from this struct altogether, and > >simply offset into the section headers when applying the relocations? > > Hmm, if everyone is OK with dropping the plt pointer from struct > mod_plt_sec, then I think we can simplify this patch even further. > > With the plt shndx saved, we can additionally pass a pointer to > sechdrs to module_emit_plt_entry(), and with that just offset into the > section headers as you suggest. Since livepatch *already* passes in > the correct copy of the section headers (mod->klp_info->sechdrs) to > apply_relocate_add(), we wouldn't even need to modify the arm64 > module_finalize() to change mod->arch.core.plt to point into > mod->klp_info->sechdrs anymore and we can drop all the changes to the > module loader too. > > Something like the following maybe? > > diff --git a/arch/arm64/include/asm/module.h b/arch/arm64/include/asm/module.h > index fef773c94e9d..ac10fa066487 100644 > --- a/arch/arm64/include/asm/module.h > +++ b/arch/arm64/include/asm/module.h > @@ -22,7 +22,7 @@ > > #ifdef CONFIG_ARM64_MODULE_PLTS > struct mod_plt_sec { > - struct elf64_shdr *plt; > + int plt_shndx; > int plt_num_entries; > int plt_max_entries; > }; > @@ -37,10 +37,12 @@ struct mod_arch_specific { > }; > #endif > > -u64 module_emit_plt_entry(struct module *mod, void *loc, const Elf64_Rela > *rela, > +u64 module_emit_plt_entry(struct module *mod, Elf64_Shdr *sechdrs, > + void *loc, const Elf64_Rela *rela, > Elf64_Sym *sym); > > -u64 module_emit_veneer_for_adrp(struct module *mod, void *loc, u64 val); > +u64 module_emit_veneer_for_adrp(struct module *mod, Elf64_Shdr *sechdrs, > + void *loc, u64 val); > > #ifdef CONFIG_RANDOMIZE_BASE > extern u64 module_alloc_base; > diff --git a/arch/arm64/kernel/module-plts.c b/arch/arm64/kernel/module-plts.c > index f0690c2ca3e0..3cd744a1cbc2 100644 > --- a/arch/arm64/kernel/module-plts.c > +++ b/arch/arm64/kernel/module-plts.c > @@ -16,13 +16,15 @@ static bool in_init(const struct module *mod, void *loc) > return (u64)loc - (u64)mod->init_layout.base < mod->init_layout.size; > } > > -u64 module_emit_plt_entry(struct module *mod, void *loc, const Elf64_Rela > *rela, > +u64 module_emit_plt_entry(struct module *mod, Elf64_Shdr *sechdrs, > + void *loc, const Elf64_Rela *rela, > Elf64_Sym *sym) > { > - struct mod_plt_sec *pltsec = !in_init(mod, loc) ? &mod->arch.core : > - &mod->arch.init; > - struct plt_entry *plt = (struct plt_entry *)pltsec->plt->sh_addr; > - int i = pltsec->plt_num_entries; > + struct mod_plt_sec *plt_info = !in_init(mod, loc) ? &mod->arch.core : > + &mod->arch.init; > + Elf64_Shdr *pltsec = sechdrs + plt_info->plt_shndx; > + struct plt_entry *plt = (struct plt_entry *)pltsec->sh_addr; > + int i = plt_info->plt_num_entries; > u64 val = sym->st_value + rela->r_addend; > > plt[i] = get_plt_entry(val); > @@ -35,24 +37,26 @@ u64 module_emit_plt_entry(struct module *mod, void *loc, > const Elf64_Rela *rela, > if (i > 0 && plt_entries_equal(plt + i, plt + i - 1)) > return (u64)&plt[i - 1]; > > - pltsec->plt_num_entries++; > - if (WARN_ON(pltsec->plt_num_entries > pltsec->plt_max_entries)) > + plt_info->plt_num_entries++; > + if (WARN_ON(plt_info->plt_num_entries > plt_info->plt_max_entries)) > return 0; > > return (u64)&plt[i]; > } > > #ifdef CONFIG_ARM64_ERRATUM_843419 > -u64 module_emit_veneer_for_adrp(struct module *mod, void *loc, u64 val) > +u64 module_emit_veneer_for_adrp(struct module *mod, Elf64_Shdr *sechdrs, > + void *loc, u64 val) > { > - struct mod_plt_sec *pltsec = !in_init(mod, loc) ? &mod->arch.core : > - &mod->arch.init; > - struct plt_entry *plt = (struct plt_entry *)pltsec->plt->sh_addr; > - int i = pltsec->plt_num_entries++; > + struct mod_plt_sec *plt_info = !in_init(mod, loc) ? &mod->arch.core : > + &mod->arch.init; > + Elf64_Shdr *pltsec = sechdrs + plt_info->plt_shndx; > + struct plt_entry *plt = (struct plt_entry *)pltsec->sh_addr; > + int i = plt_info->plt_num_entries++; > u32 mov0, mov1, mov2, br; > int rd; > > - if (WARN_ON(pltsec->plt_num_entries > pltsec->plt_max_entries)) > + if (WARN_ON(plt_info->plt_num_entries > plt_info->plt_max_entries)) > return 0; > > /* get the destination register of the ADRP instruction */ > @@ -202,7 +206,7 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr > *sechdrs, > unsigned long core_plts = 0; > unsigned long init_plts = 0; > Elf64_Sym *syms = NULL; > - Elf_Shdr *tramp = NULL; > + Elf_Shdr *pltsec, *tramp = NULL; > int i; > > /* > @@ -211,9 +215,9 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr > *sechdrs, > */ > for (i = 0; i < ehdr->e_shnum; i++) { > if (!strcmp(secstrings + sechdrs[i].sh_name, ".plt")) > - mod->arch.core.plt = sechdrs + i; > + mod->arch.core.plt_shndx = i; > else if (!strcmp(secstrings + sechdrs[i].sh_name, > ".init.plt")) > - mod->arch.init.plt = sechdrs + i; > + mod->arch.init.plt_shndx = i; > else if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE) && > !strcmp(secstrings + sechdrs[i].sh_name, > ".text.ftrace_trampoline")) > @@ -222,7 +226,7 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr > *sechdrs, > syms = (Elf64_Sym *)sechdrs[i].sh_addr; > } > > - if (!mod->arch.core.plt || !mod->arch.init.plt) { > + if (!mod->arch.core.plt_shndx || !mod->arch.init.plt_shndx) { > pr_err("%s: module PLT section(s) missing\n", mod->name); > return -ENOEXEC; > } > @@ -254,17 +258,19 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr > *sechdrs, > sechdrs[i].sh_info, dstsec); > } > > - mod->arch.core.plt->sh_type = SHT_NOBITS; > - mod->arch.core.plt->sh_flags = SHF_EXECINSTR | SHF_ALLOC; > - mod->arch.core.plt->sh_addralign = L1_CACHE_BYTES; > - mod->arch.core.plt->sh_size = (core_plts + 1) * sizeof(struct > plt_entry); > + pltsec = sechdrs + mod->arch.core.plt_shndx; > + pltsec->sh_type = SHT_NOBITS; > + pltsec->sh_flags = SHF_EXECINSTR | SHF_ALLOC; > + pltsec->sh_addralign = L1_CACHE_BYTES; > + pltsec->sh_size = (core_plts + 1) * sizeof(struct plt_entry); > mod->arch.core.plt_num_entries = 0; > mod->arch.core.plt_max_entries = core_plts; > > - mod->arch.init.plt->sh_type = SHT_NOBITS; > - mod->arch.init.plt->sh_flags = SHF_EXECINSTR | SHF_ALLOC; > - mod->arch.init.plt->sh_addralign = L1_CACHE_BYTES; > - mod->arch.init.plt->sh_size = (init_plts + 1) * sizeof(struct > plt_entry); > + pltsec = sechdrs + mod->arch.init.plt_shndx; > + pltsec->sh_type = SHT_NOBITS; > + pltsec->sh_flags = SHF_EXECINSTR | SHF_ALLOC; > + pltsec->sh_addralign = L1_CACHE_BYTES; > + pltsec->sh_size = (init_plts + 1) * sizeof(struct plt_entry); > mod->arch.init.plt_num_entries = 0; > mod->arch.init.plt_max_entries = init_plts; > > diff --git a/arch/arm64/kernel/module.c b/arch/arm64/kernel/module.c > index dd23655fda3a..8e6444db2d8e 100644 > --- a/arch/arm64/kernel/module.c > +++ b/arch/arm64/kernel/module.c > @@ -198,7 +198,8 @@ static int reloc_insn_imm(enum aarch64_reloc_op op, __le32 > *place, u64 val, > return 0; > } > > -static int reloc_insn_adrp(struct module *mod, __le32 *place, u64 val) > +static int reloc_insn_adrp(struct module *mod, Elf64_Shdr *sechdrs, > + __le32 *place, u64 val) > { > u32 insn; > > @@ -215,7 +216,7 @@ static int reloc_insn_adrp(struct module *mod, __le32 > *place, u64 val) > insn &= ~BIT(31); > } else { > /* out of range for ADR -> emit a veneer */ > - val = module_emit_veneer_for_adrp(mod, place, val & ~0xfff); > + val = module_emit_veneer_for_adrp(mod, sechdrs, place, val & > ~0xfff); > if (!val) > return -ENOEXEC; > insn = aarch64_insn_gen_branch_imm((u64)place, val, > @@ -368,7 +369,7 @@ int apply_relocate_add(Elf64_Shdr *sechdrs, > case R_AARCH64_ADR_PREL_PG_HI21_NC: > overflow_check = false; > case R_AARCH64_ADR_PREL_PG_HI21: > - ovf = reloc_insn_adrp(me, loc, val); > + ovf = reloc_insn_adrp(me, sechdrs, loc, val); > if (ovf && ovf != -ERANGE) > return ovf; > break; > @@ -413,7 +414,7 @@ int apply_relocate_add(Elf64_Shdr *sechdrs, > > if (IS_ENABLED(CONFIG_ARM64_MODULE_PLTS) && > ovf == -ERANGE) { > - val = module_emit_plt_entry(me, loc, &rel[i], > sym); > + val = module_emit_plt_entry(me, sechdrs, loc, > &rel[i], sym); > if (!val) > return -ENOEXEC; > ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, > 2, > > Perhaps this approach is better. Miroslav and Petr, do you think this > would work? (Apologies for the efforts to review the last two > versions, if we end up scrapping the old patch :-/) No problem. I think it should work and it looks good to me (I did not compile it though). I'm glad we don't have to touch load_module(). The function is complicated enough. Thanks, Miroslav