Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754101AbbKLR7G (ORCPT ); Thu, 12 Nov 2015 12:59:06 -0500 Received: from mx1.redhat.com ([209.132.183.28]:38416 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753542AbbKLR7D (ORCPT ); Thu, 12 Nov 2015 12:59:03 -0500 Date: Thu, 12 Nov 2015 11:59:01 -0600 From: Josh Poimboeuf To: Jessica Yu Cc: Rusty Russell , Seth Jennings , Jiri Kosina , Vojtech Pavlik , Miroslav Benes , linux-api@vger.kernel.org, live-patching@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH 3/5] livepatch: reuse module loader code to write relocations Message-ID: <20151112175901.GH4038@treble.hsd1.ky.comcast.net> References: <1447130755-17383-1-git-send-email-jeyu@redhat.com> <1447130755-17383-4-git-send-email-jeyu@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1447130755-17383-4-git-send-email-jeyu@redhat.com> User-Agent: Mutt/1.5.23.1-rc1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7197 Lines: 217 On Mon, Nov 09, 2015 at 11:45:53PM -0500, Jessica Yu wrote: > Reuse module loader code to write relocations, thereby eliminating the > need for architecture specific code in livepatch. Namely, we reuse > apply_relocate_add() in the module loader to write relocs instead of > duplicating functionality in livepatch's klp_write_module_reloc(). To > apply relocation sections, remaining SHN_LIVEPATCH symbols referenced by > relocs are resolved and then apply_relocate_add() is called to apply > those relocations. > > Signed-off-by: Jessica Yu > --- > include/linux/livepatch.h | 11 ++++-- > include/linux/module.h | 6 ++++ > kernel/livepatch/core.c | 89 +++++++++++++++++++++++++++++------------------ > 3 files changed, 70 insertions(+), 36 deletions(-) > > diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h > index 31db7a0..601e892 100644 > --- a/include/linux/livepatch.h > +++ b/include/linux/livepatch.h > @@ -85,7 +85,7 @@ struct klp_reloc { > /** > * struct klp_object - kernel object structure for live patching > * @name: module name (or NULL for vmlinux) > - * @relocs: relocation entries to be applied at load time > + * @reloc_secs: relocation sections to be applied at load time > * @funcs: function entries for functions to be patched in the object > * @kobj: kobject for sysfs resources > * @mod: kernel module associated with the patched object > @@ -95,7 +95,7 @@ struct klp_reloc { > struct klp_object { > /* external */ > const char *name; > - struct klp_reloc *relocs; > + struct list_head reloc_secs; > struct klp_func *funcs; > > /* internal */ > @@ -129,6 +129,13 @@ struct klp_patch { > #define klp_for_each_func(obj, func) \ > for (func = obj->funcs; func->old_name; func++) > > +struct klp_reloc_sec { > + unsigned int index; > + char *name; > + char *objname; > + struct list_head list; > +}; > + > int klp_register_patch(struct klp_patch *); > int klp_unregister_patch(struct klp_patch *); > int klp_enable_patch(struct klp_patch *); > diff --git a/include/linux/module.h b/include/linux/module.h > index c8680b1..3c34eb8 100644 > --- a/include/linux/module.h > +++ b/include/linux/module.h > @@ -793,9 +793,15 @@ extern int module_sysfs_initialized; > #ifdef CONFIG_DEBUG_SET_MODULE_RONX > extern void set_all_modules_text_rw(void); > extern void set_all_modules_text_ro(void); > +extern void > +set_page_attributes(void *start, void *end, > + int (*set)(unsigned long start, int num_pages)); > #else > static inline void set_all_modules_text_rw(void) { } > static inline void set_all_modules_text_ro(void) { } > +static inline void > +set_page_attributes(void *start, void *end, > + int (*set)(unsigned long start, int num_pages)) { } > #endif > > #ifdef CONFIG_GENERIC_BUG > diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c > index 087a8c7..26c419f 100644 > --- a/kernel/livepatch/core.c > +++ b/kernel/livepatch/core.c > @@ -28,6 +28,8 @@ > #include > #include > #include > +#include > +#include > > /** > * struct klp_ops - structure for tracking registered ftrace ops structs > @@ -281,46 +283,54 @@ static int klp_find_external_symbol(struct module *pmod, const char *name, > } > > static int klp_write_object_relocations(struct module *pmod, > - struct klp_object *obj) > + struct klp_object *obj, > + struct klp_patch *patch) > { > - int ret; > - struct klp_reloc *reloc; > + int relindex, num_relas; > + int i, ret = 0; > + unsigned long addr; > + unsigned int bind; > + char *symname; > + struct klp_reloc_sec *reloc_sec; > + struct load_info *info; > + Elf_Rela *rela; > + Elf_Sym *sym, *symtab; > + Elf_Shdr *symsect; > > if (WARN_ON(!klp_is_object_loaded(obj))) > return -EINVAL; > > - if (WARN_ON(!obj->relocs)) > - return -EINVAL; > - > - for (reloc = obj->relocs; reloc->name; reloc++) { > - if (!klp_is_module(obj)) { > - ret = klp_verify_vmlinux_symbol(reloc->name, > - reloc->val); > - if (ret) > - return ret; > - } else { > - /* module, reloc->val needs to be discovered */ > - if (reloc->external) > - ret = klp_find_external_symbol(pmod, > - reloc->name, > - &reloc->val); > - else > - ret = klp_find_object_symbol(obj->mod->name, > - reloc->name, > - &reloc->val); > - if (ret) > - return ret; > - } > - ret = klp_write_module_reloc(pmod, reloc->type, reloc->loc, > - reloc->val + reloc->addend); > - if (ret) { > - pr_err("relocation failed for symbol '%s' at 0x%016lx (%d)\n", > - reloc->name, reloc->val, ret); > - return ret; > + info = pmod->info; > + symsect = info->sechdrs + info->index.sym; > + symtab = (void *)info->hdr + symsect->sh_offset; > + > + /* For each __klp_rela section for this object */ > + list_for_each_entry(reloc_sec, &obj->reloc_secs, list) { > + relindex = reloc_sec->index; > + num_relas = info->sechdrs[relindex].sh_size / sizeof(Elf_Rela); > + rela = (Elf_Rela *) info->sechdrs[relindex].sh_addr; > + > + /* For each rela in this __klp_rela section */ > + for (i = 0; i < num_relas; i++, rela++) { > + sym = symtab + ELF_R_SYM(rela->r_info); > + symname = info->strtab + sym->st_name; > + bind = ELF_ST_BIND(sym->st_info); > + > + if (sym->st_shndx == SHN_LIVEPATCH) { > + if (bind == STB_LIVEPATCH_EXT) > + ret = klp_find_external_symbol(pmod, symname, &addr); > + else > + ret = klp_find_object_symbol(obj->name, symname, &addr); > + if (ret) > + return ret; > + sym->st_value = addr; > + } This is missing an important piece, I think. There's no way to disambiguate duplicate symbols. Before, there was reloc->val, which contained the symbol's address. There's nothing like that here. I think we could use sym->st_value for that purpose. After Chris's patch set gets merged, it could contain the sympos. > } > + ret = apply_relocate_add(info->sechdrs, info->strtab, > + info->index.sym, relindex, pmod); > } > > - return 0; > + return ret; > } > > static void notrace klp_ftrace_handler(unsigned long ip, > @@ -741,12 +751,23 @@ static int klp_init_object_loaded(struct klp_patch *patch, > struct klp_object *obj) > { > struct klp_func *func; > + struct module *pmod; > int ret; > > - if (obj->relocs) { > - ret = klp_write_object_relocations(patch->mod, obj); > + pmod = patch->mod; > + > + if (!list_empty(&obj->reloc_secs)) { > + set_page_attributes(pmod->module_core, > + pmod->module_core + pmod->core_text_size, > + set_memory_rw); > + > + ret = klp_write_object_relocations(pmod, obj, patch); > if (ret) > return ret; > + > + set_page_attributes(pmod->module_core, > + pmod->module_core + pmod->core_text_size, > + set_memory_ro); > } > > klp_for_each_func(obj, func) { > -- > 2.4.3 > -- Josh -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/