Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755704AbbLAEWB (ORCPT ); Mon, 30 Nov 2015 23:22:01 -0500 Received: from mx1.redhat.com ([209.132.183.28]:47170 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754744AbbLAEVf (ORCPT ); Mon, 30 Nov 2015 23:21:35 -0500 From: Jessica Yu To: Rusty Russell , Josh Poimboeuf , Seth Jennings , Jiri Kosina , Vojtech Pavlik , Jonathan Corbet , Miroslav Benes Cc: linux-api@vger.kernel.org, live-patching@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, linux-doc@vger.kernel.org Subject: [RFC PATCH v2 4/6] livepatch: reuse module loader code to write relocations Date: Mon, 30 Nov 2015 23:21:17 -0500 Message-Id: <1448943679-3412-5-git-send-email-jeyu@redhat.com> In-Reply-To: <1448943679-3412-1-git-send-email-jeyu@redhat.com> References: <1448943679-3412-1-git-send-email-jeyu@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 11517 Lines: 363 Reuse module loader code to write relocations, thereby eliminating the need for architecture specific relocation code in livepatch. Namely, we reuse apply_relocate_add() in the module loader to write relocations 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. In addition, remove x86 livepatch relocation code. It is no longer needed since symbol resolution and relocation work have been offloaded to module loader. Signed-off-by: Jessica Yu --- arch/x86/include/asm/livepatch.h | 2 - arch/x86/kernel/Makefile | 1 - arch/x86/kernel/livepatch.c | 91 -------------------------------------- include/linux/livepatch.h | 30 ++++++------- include/linux/module.h | 6 +++ kernel/livepatch/core.c | 94 ++++++++++++++++++++++------------------ 6 files changed, 70 insertions(+), 154 deletions(-) delete mode 100644 arch/x86/kernel/livepatch.c diff --git a/arch/x86/include/asm/livepatch.h b/arch/x86/include/asm/livepatch.h index 19c099a..7312e25 100644 --- a/arch/x86/include/asm/livepatch.h +++ b/arch/x86/include/asm/livepatch.h @@ -33,8 +33,6 @@ static inline int klp_check_compiler_support(void) #endif return 0; } -int klp_write_module_reloc(struct module *mod, unsigned long type, - unsigned long loc, unsigned long value); static inline void klp_arch_set_pc(struct pt_regs *regs, unsigned long ip) { diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile index b1b78ff..c5e9a5c 100644 --- a/arch/x86/kernel/Makefile +++ b/arch/x86/kernel/Makefile @@ -67,7 +67,6 @@ obj-$(CONFIG_X86_MPPARSE) += mpparse.o obj-y += apic/ obj-$(CONFIG_X86_REBOOTFIXUPS) += reboot_fixups_32.o obj-$(CONFIG_DYNAMIC_FTRACE) += ftrace.o -obj-$(CONFIG_LIVEPATCH) += livepatch.o obj-$(CONFIG_FUNCTION_GRAPH_TRACER) += ftrace.o obj-$(CONFIG_FTRACE_SYSCALLS) += ftrace.o obj-$(CONFIG_X86_TSC) += trace_clock.o diff --git a/arch/x86/kernel/livepatch.c b/arch/x86/kernel/livepatch.c deleted file mode 100644 index d1d35cc..0000000 --- a/arch/x86/kernel/livepatch.c +++ /dev/null @@ -1,91 +0,0 @@ -/* - * livepatch.c - x86-specific Kernel Live Patching Core - * - * Copyright (C) 2014 Seth Jennings - * Copyright (C) 2014 SUSE - * - * This program is free software; you can redistribute it and/or - * modify it under the terms of the GNU General Public License - * as published by the Free Software Foundation; either version 2 - * of the License, or (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, see . - */ - -#include -#include -#include -#include -#include -#include - -/** - * klp_write_module_reloc() - write a relocation in a module - * @mod: module in which the section to be modified is found - * @type: ELF relocation type (see asm/elf.h) - * @loc: address that the relocation should be written to - * @value: relocation value (sym address + addend) - * - * This function writes a relocation to the specified location for - * a particular module. - */ -int klp_write_module_reloc(struct module *mod, unsigned long type, - unsigned long loc, unsigned long value) -{ - int ret, numpages, size = 4; - bool readonly; - unsigned long val; - unsigned long core = (unsigned long)mod->module_core; - unsigned long core_size = mod->core_size; - - switch (type) { - case R_X86_64_NONE: - return 0; - case R_X86_64_64: - val = value; - size = 8; - break; - case R_X86_64_32: - val = (u32)value; - break; - case R_X86_64_32S: - val = (s32)value; - break; - case R_X86_64_PC32: - val = (u32)(value - loc); - break; - default: - /* unsupported relocation type */ - return -EINVAL; - } - - if (loc < core || loc >= core + core_size) - /* loc does not point to any symbol inside the module */ - return -EINVAL; - - readonly = false; - -#ifdef CONFIG_DEBUG_SET_MODULE_RONX - if (loc < core + mod->core_ro_size) - readonly = true; -#endif - - /* determine if the relocation spans a page boundary */ - numpages = ((loc & PAGE_MASK) == ((loc + size) & PAGE_MASK)) ? 1 : 2; - - if (readonly) - set_memory_rw(loc & PAGE_MASK, numpages); - - ret = probe_kernel_write((void *)loc, &val, size); - - if (readonly) - set_memory_ro(loc & PAGE_MASK, numpages); - - return ret; -} diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h index 31db7a0..54f62a6 100644 --- a/include/linux/livepatch.h +++ b/include/linux/livepatch.h @@ -64,28 +64,21 @@ struct klp_func { }; /** - * struct klp_reloc - relocation structure for live patching - * @loc: address where the relocation will be written - * @val: address of the referenced symbol (optional, - * vmlinux patches only) - * @type: ELF relocation type - * @name: name of the referenced symbol (for lookup/verification) - * @addend: offset from the referenced symbol - * @external: symbol is either exported or within the live patch module itself + * struct klp_reloc_sec - relocation section struct for live patching + * @index: Elf section index of the relocation section + * @name: name of the relocation section + * @objname: name of the object associated with the klp reloc section */ -struct klp_reloc { - unsigned long loc; - unsigned long val; - unsigned long type; - const char *name; - int addend; - int external; +struct klp_reloc_sec { + unsigned int index; + char *name; + char *objname; }; /** * 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 +88,7 @@ struct klp_reloc { struct klp_object { /* external */ const char *name; - struct klp_reloc *relocs; + struct klp_reloc_sec *reloc_secs; struct klp_func *funcs; /* internal */ @@ -129,6 +122,9 @@ struct klp_patch { #define klp_for_each_func(obj, func) \ for (func = obj->funcs; func->old_name; func++) +#define klp_for_each_reloc_sec(obj, reloc_sec) \ + for (reloc_sec = obj->reloc_secs; reloc_sec->name; reloc_sec++) + 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 9b46256..ea61147 100644 --- a/include/linux/module.h +++ b/include/linux/module.h @@ -777,9 +777,15 @@ 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 db545cb..17b7278 100644 --- a/kernel/livepatch/core.c +++ b/kernel/livepatch/core.c @@ -28,6 +28,9 @@ #include #include #include +#include +#include +#include /** * struct klp_ops - structure for tracking registered ftrace ops structs @@ -281,52 +284,48 @@ 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; + char *symname; + struct klp_reloc_sec *reloc_sec; + Elf_Rela *rela; + Elf_Sym *sym, *symtab; 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)) { - -#if defined(CONFIG_RANDOMIZE_BASE) - /* If KASLR has been enabled, adjust old value accordingly */ - if (kaslr_enabled()) - reloc->val += kaslr_offset(); -#endif - 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; + symtab = (void *)pmod->core_symtab; + + /* For each __klp_rela section for this object */ + klp_for_each_reloc_sec(obj, reloc_sec) { + relindex = reloc_sec->index; + num_relas = pmod->sechdrs[relindex].sh_size / sizeof(Elf_Rela); + rela = (Elf_Rela *) pmod->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 = pmod->core_strtab + sym->st_name; + + if (sym->st_shndx == SHN_LIVEPATCH) { + if (sym->st_info == 'K') + 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; + } } + ret = apply_relocate_add(pmod->sechdrs, pmod->core_strtab, + pmod->index.sym, relindex, pmod); } - return 0; + return ret; } static void notrace klp_ftrace_handler(unsigned long ip, @@ -747,13 +746,22 @@ 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); - if (ret) - return ret; - } + pmod = patch->mod; + + 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) { ret = klp_find_verify_func_addr(obj, func); -- 2.4.3 -- 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/