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Commit 425595a7 authored by Jessica Yu's avatar Jessica Yu Committed by Jiri Kosina
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livepatch: reuse module loader code to write relocations 



Reuse module loader code to write relocations, thereby eliminating the need
for architecture specific relocation code in livepatch. Specifically, reuse
the apply_relocate_add() function in the module loader to write relocations
instead of duplicating functionality in livepatch's arch-dependent
klp_write_module_reloc() function.

In order to accomplish this, livepatch modules manage their own relocation
sections (marked with the SHF_RELA_LIVEPATCH section flag) and
livepatch-specific symbols (marked with SHN_LIVEPATCH symbol section
index). To apply livepatch relocation sections, 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 and the s390
klp_write_module_reloc() function stub. They are no longer needed since
relocation work has been offloaded to module loader.

Lastly, mark the module as a livepatch module so that the module loader
canappropriately identify and initialize it.

Signed-off-by: default avatarJessica Yu <jeyu@redhat.com>
Reviewed-by: default avatarMiroslav Benes <mbenes@suse.cz>
Acked-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com>   # for s390 changes
Signed-off-by: default avatarJiri Kosina <jkosina@suse.cz>
parent f31e0960

arch/s390/include/asm/livepatch.h

+0 −7
Original line number Diff line number Diff line
@@ -24,13 +24,6 @@ static inline int klp_check_compiler_support(void) 
	return 0;

}



static inline int klp_write_module_reloc(struct module *mod, unsigned long

		type, unsigned long loc, unsigned long value)

{

	/* not supported yet */

	return -ENOSYS;

}



static inline void klp_arch_set_pc(struct pt_regs *regs, unsigned long ip)

{

	regs->psw.addr = ip;

arch/x86/include/asm/livepatch.h

+0 −2
Original line number Diff line number Diff line
@@ -32,8 +32,6 @@ 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)

{

arch/x86/kernel/Makefile

+0 −1
Original line number Diff line number Diff line
@@ -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

arch/x86/kernel/livepatch.c

deleted100644 → 0
+0 −70
Original line number Diff line number Diff line 
/*

 * livepatch.c - x86-specific Kernel Live Patching Core

 *

 * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>

 * 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 <http://www.gnu.org/licenses/>.

 */



#include <linux/module.h>

#include <linux/uaccess.h>

#include <asm/elf.h>

#include <asm/livepatch.h>



/**

 * 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)

{

	size_t size = 4;

	unsigned long val;

	unsigned long core = (unsigned long)mod->core_layout.base;

	unsigned long core_size = mod->core_layout.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;



	return probe_kernel_write((void *)loc, &val, size);

}

include/linux/livepatch.h

+0 −20
Original line number Diff line number Diff line
@@ -64,28 +64,9 @@ struct klp_func { 
	struct list_head stack_node;

};



/**

 * struct klp_reloc - relocation structure for live patching

 * @loc:	address where the relocation will be written

 * @sympos:	position in kallsyms to disambiguate symbols (optional)

 * @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 {

	unsigned long loc;

	unsigned long sympos;

	unsigned long type;

	const char *name;

	int addend;

	int external;

};



/**

 * 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

 * @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 +76,6 @@ struct klp_reloc { 
struct klp_object {

	/* external */

	const char *name;

	struct klp_reloc *relocs;

	struct klp_func *funcs;



	/* internal */