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livepatch/x86: apply alternatives and paravirt patches after relocations 

Implement arch_klp_init_object_loaded() for x86, which applies
alternatives/paravirt patches. This fixes the order in which relocations
and alternatives/paravirt patches are applied.

Previously, if a patch module had alternatives or paravirt patches,
these were applied first by the module loader before livepatch can apply
per-object relocations. The (buggy) sequence of events was:

(1) Load patch module
(2) Apply alternatives and paravirt patches to patch module
    * Note that these are applied to the new functions in the patch module
(3) Apply per-object relocations to patch module when target module loads.
    * This clobbers what was written in step 2

This lead to crashes and corruption in general, since livepatch would
overwrite or step on previously applied alternative/paravirt patches.
The correct sequence of events should be:

(1) Load patch module
(2) Apply per-object relocations to patch module
(3) Apply alternatives and paravirt patches to patch module

This is fixed by delaying paravirt/alternatives patching until after
relocations are applied. Any .altinstructions or .parainstructions
sections are prefixed with ".klp.arch.${objname}" and applied in
arch_klp_init_object_loaded().

Signed-off-by: Jessica Yu <jeyu@redhat.com>
Acked-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
steinar/wifi_calib_4_9_kernel
Jessica Yu 2016-08-17 20:58:29 -04:00 committed by Jiri Kosina
parent 255e732c61
commit d4c3e6e1b1
2 changed files with 66 additions and 0 deletions
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1
arch/x86/kernel/Makefile
View File

@ -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

65
arch/x86/kernel/livepatch.c 100644
View File

@ -0,0 +1,65 @@
/*
* 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);
}
}