Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/livepatching (ddc4e6d2) · Commits · 戴 / test

Documentation/livepatch/module-elf-format.txt

+16 −4

Original line number	Diff line number	Diff line
		@@ -25,7 +25,8 @@ Table of Contents
		3.3.2 Required name format
		3.3.3 Example livepatch symbol names
		3.3.4 Example `readelf --symbols` output
		4. Symbol table and Elf section access
		4. Architecture-specific sections
		5. Symbol table and Elf section access

		----------------------------
		0. Background and motivation
		@@ -46,7 +47,7 @@ architecture.

		Since apply_relocate_add() requires access to a module's section header
		table, symbol table, and relocation section indices, Elf information is
		preserved for livepatch modules (see section 4). Livepatch manages its own
		preserved for livepatch modules (see section 5). Livepatch manages its own
		relocation sections and symbols, which are described in this document. The
		Elf constants used to mark livepatch symbols and relocation sections were
		selected from OS-specific ranges according to the definitions from glibc.
		@@ -117,7 +118,7 @@ also possible for a livepatch module to have no livepatch relocation
		sections, as in the case of the sample livepatch module (see
		samples/livepatch).

		Since Elf information is preserved for livepatch modules (see Section 4), a
		Since Elf information is preserved for livepatch modules (see Section 5), a
		livepatch relocation section can be applied simply by passing in the
		appropriate section index to apply_relocate_add(), which then uses it to
		access the relocation section and apply the relocations.
		@@ -292,8 +293,19 @@ Symbol table '.symtab' contains 127 entries:
		[*] Note that the 'Ndx' (Section index) for these symbols is SHN_LIVEPATCH (0xff20).
		"OS" means OS-specific.

		---------------------------------
		4. Architecture-specific sections
		---------------------------------
		Architectures may override arch_klp_init_object_loaded() to perform
		additional arch-specific tasks when a target module loads, such as applying
		arch-specific sections. On x86 for example, we must apply per-object
		.altinstructions and .parainstructions sections when a target module loads.
		These sections must be prefixed with ".klp.arch.$objname." so that they can
		be easily identified when iterating through a patch module's Elf sections
		(See arch/x86/kernel/livepatch.c for a complete example).

		--------------------------------------
		4. Symbol table and Elf section access
		5. Symbol table and Elf section access
		--------------------------------------
		A livepatch module's symbol table is accessible through module->symtab.

arch/x86/kernel/Makefile

+1 −0

Original line number	Diff line number	Diff line
		@@ -83,6 +83,7 @@ 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

arch/x86/kernel/livepatch.c

0 → 100644

+65 −0

Original line number	Diff line number	Diff line
		/*
		* livepatch.c - x86-specific Kernel Live Patching Core
		*
		* 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 <http://www.gnu.org/licenses/>.
		*/

		#include <linux/module.h>
		#include <linux/kallsyms.h>
		#include <linux/livepatch.h>
		#include <asm/text-patching.h>

		/* Apply per-object alternatives. Based on x86 module_finalize() */
		void arch_klp_init_object_loaded(struct klp_patch *patch,
		struct klp_object *obj)
		{
		int cnt;
		struct klp_modinfo *info;
		Elf_Shdr s, alt = NULL, *para = NULL;
		void aseg, pseg;
		const char *objname;
		char sec_objname[MODULE_NAME_LEN];
		char secname[KSYM_NAME_LEN];

		info = patch->mod->klp_info;
		objname = obj->name ? obj->name : "vmlinux";

		/* See livepatch core code for BUILD_BUG_ON() explanation */
		BUILD_BUG_ON(MODULE_NAME_LEN < 56 \|\| KSYM_NAME_LEN != 128);

		for (s = info->sechdrs; s < info->sechdrs + info->hdr.e_shnum; s++) {
		/* Apply per-object .klp.arch sections */
		cnt = sscanf(info->secstrings + s->sh_name,
		".klp.arch.%55[^.].%127s",
		sec_objname, secname);
		if (cnt != 2)
		continue;
		if (strcmp(sec_objname, objname))
		continue;
		if (!strcmp(".altinstructions", secname))
		alt = s;
		if (!strcmp(".parainstructions", secname))
		para = s;
		}

		if (alt) {
		aseg = (void *) alt->sh_addr;
		apply_alternatives(aseg, aseg + alt->sh_size);
		}

		if (para) {
		pseg = (void *) para->sh_addr;
		apply_paravirt(pseg, pseg + para->sh_size);
		}
		}

include/linux/livepatch.h

+3 −0

Original line number	Diff line number	Diff line
		@@ -116,6 +116,9 @@ int klp_unregister_patch(struct klp_patch *);
		int klp_enable_patch(struct klp_patch *);
		int klp_disable_patch(struct klp_patch *);

		void arch_klp_init_object_loaded(struct klp_patch *patch,
		struct klp_object *obj);

		/* Called from the module loader during module coming/going states */
		int klp_module_coming(struct module *mod);
		void klp_module_going(struct module *mod);

kernel/livepatch/core.c

+13 −6

Original line number	Diff line number	Diff line
		@@ -274,7 +274,6 @@ static int klp_write_object_relocations(struct module *pmod,

		objname = klp_is_module(obj) ? obj->name : "vmlinux";

		module_disable_ro(pmod);
		/* For each klp relocation section */
		for (i = 1; i < pmod->klp_info->hdr.e_shnum; i++) {
		sec = pmod->klp_info->sechdrs + i;
		@@ -309,7 +308,6 @@ static int klp_write_object_relocations(struct module *pmod,
		break;
		}

		module_enable_ro(pmod, true);
		return ret;
		}

		@@ -547,9 +545,6 @@ static int __klp_enable_patch(struct klp_patch *patch)
		list_prev_entry(patch, list)->state == KLP_DISABLED)
		return -EBUSY;

		pr_notice_once("tainting kernel with TAINT_LIVEPATCH\n");
		add_taint(TAINT_LIVEPATCH, LOCKDEP_STILL_OK);

		pr_notice("enabling patch '%s'\n", patch->mod->name);

		klp_for_each_object(patch, obj) {
		@@ -763,6 +758,12 @@ static int klp_init_func(struct klp_object obj, struct klp_func func)
		func->old_sympos ? func->old_sympos : 1);
		}

		/* Arches may override this to finish any remaining arch-specific tasks */
		void __weak arch_klp_init_object_loaded(struct klp_patch *patch,
		struct klp_object *obj)
		{
		}

		/* parts of the initialization that is done only when the object is loaded */
		static int klp_init_object_loaded(struct klp_patch *patch,
		struct klp_object *obj)
		@@ -770,9 +771,15 @@ static int klp_init_object_loaded(struct klp_patch *patch,
		struct klp_func *func;
		int ret;

		module_disable_ro(patch->mod);
		ret = klp_write_object_relocations(patch->mod, obj);
		if (ret)
		if (ret) {
		module_enable_ro(patch->mod, true);
		return ret;
		}

		arch_klp_init_object_loaded(patch, obj);
		module_enable_ro(patch->mod, true);

		klp_for_each_func(obj, func) {
		ret = klp_find_object_symbol(obj->name, func->old_name,

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