forked from Minki/linux
93862e385d
Provide livepatch modules a klp_object (un)patching notification mechanism. Pre and post-(un)patch callbacks allow livepatch modules to setup or synchronize changes that would be difficult to support in only patched-or-unpatched code contexts. Callbacks can be registered for target module or vmlinux klp_objects, but each implementation is klp_object specific. - Pre-(un)patch callbacks run before any (un)patching transition starts. - Post-(un)patch callbacks run once an object has been (un)patched and the klp_patch fully transitioned to its target state. Example use cases include modification of global data and registration of newly available services/handlers. See Documentation/livepatch/callbacks.txt for details and samples/livepatch/ for examples. Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Acked-by: Miroslav Benes <mbenes@suse.cz> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
278 lines
6.4 KiB
C
278 lines
6.4 KiB
C
/*
|
|
* patch.c - livepatch patching functions
|
|
*
|
|
* Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
|
|
* Copyright (C) 2014 SUSE
|
|
* Copyright (C) 2015 Josh Poimboeuf <jpoimboe@redhat.com>
|
|
*
|
|
* 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/>.
|
|
*/
|
|
|
|
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
|
|
|
|
#include <linux/livepatch.h>
|
|
#include <linux/list.h>
|
|
#include <linux/ftrace.h>
|
|
#include <linux/rculist.h>
|
|
#include <linux/slab.h>
|
|
#include <linux/bug.h>
|
|
#include <linux/printk.h>
|
|
#include "core.h"
|
|
#include "patch.h"
|
|
#include "transition.h"
|
|
|
|
static LIST_HEAD(klp_ops);
|
|
|
|
struct klp_ops *klp_find_ops(unsigned long old_addr)
|
|
{
|
|
struct klp_ops *ops;
|
|
struct klp_func *func;
|
|
|
|
list_for_each_entry(ops, &klp_ops, node) {
|
|
func = list_first_entry(&ops->func_stack, struct klp_func,
|
|
stack_node);
|
|
if (func->old_addr == old_addr)
|
|
return ops;
|
|
}
|
|
|
|
return NULL;
|
|
}
|
|
|
|
static void notrace klp_ftrace_handler(unsigned long ip,
|
|
unsigned long parent_ip,
|
|
struct ftrace_ops *fops,
|
|
struct pt_regs *regs)
|
|
{
|
|
struct klp_ops *ops;
|
|
struct klp_func *func;
|
|
int patch_state;
|
|
|
|
ops = container_of(fops, struct klp_ops, fops);
|
|
|
|
/*
|
|
* A variant of synchronize_sched() is used to allow patching functions
|
|
* where RCU is not watching, see klp_synchronize_transition().
|
|
*/
|
|
preempt_disable_notrace();
|
|
|
|
func = list_first_or_null_rcu(&ops->func_stack, struct klp_func,
|
|
stack_node);
|
|
|
|
/*
|
|
* func should never be NULL because preemption should be disabled here
|
|
* and unregister_ftrace_function() does the equivalent of a
|
|
* synchronize_sched() before the func_stack removal.
|
|
*/
|
|
if (WARN_ON_ONCE(!func))
|
|
goto unlock;
|
|
|
|
/*
|
|
* In the enable path, enforce the order of the ops->func_stack and
|
|
* func->transition reads. The corresponding write barrier is in
|
|
* __klp_enable_patch().
|
|
*
|
|
* (Note that this barrier technically isn't needed in the disable
|
|
* path. In the rare case where klp_update_patch_state() runs before
|
|
* this handler, its TIF_PATCH_PENDING read and this func->transition
|
|
* read need to be ordered. But klp_update_patch_state() already
|
|
* enforces that.)
|
|
*/
|
|
smp_rmb();
|
|
|
|
if (unlikely(func->transition)) {
|
|
|
|
/*
|
|
* Enforce the order of the func->transition and
|
|
* current->patch_state reads. Otherwise we could read an
|
|
* out-of-date task state and pick the wrong function. The
|
|
* corresponding write barrier is in klp_init_transition().
|
|
*/
|
|
smp_rmb();
|
|
|
|
patch_state = current->patch_state;
|
|
|
|
WARN_ON_ONCE(patch_state == KLP_UNDEFINED);
|
|
|
|
if (patch_state == KLP_UNPATCHED) {
|
|
/*
|
|
* Use the previously patched version of the function.
|
|
* If no previous patches exist, continue with the
|
|
* original function.
|
|
*/
|
|
func = list_entry_rcu(func->stack_node.next,
|
|
struct klp_func, stack_node);
|
|
|
|
if (&func->stack_node == &ops->func_stack)
|
|
goto unlock;
|
|
}
|
|
}
|
|
|
|
klp_arch_set_pc(regs, (unsigned long)func->new_func);
|
|
unlock:
|
|
preempt_enable_notrace();
|
|
}
|
|
|
|
/*
|
|
* Convert a function address into the appropriate ftrace location.
|
|
*
|
|
* Usually this is just the address of the function, but on some architectures
|
|
* it's more complicated so allow them to provide a custom behaviour.
|
|
*/
|
|
#ifndef klp_get_ftrace_location
|
|
static unsigned long klp_get_ftrace_location(unsigned long faddr)
|
|
{
|
|
return faddr;
|
|
}
|
|
#endif
|
|
|
|
static void klp_unpatch_func(struct klp_func *func)
|
|
{
|
|
struct klp_ops *ops;
|
|
|
|
if (WARN_ON(!func->patched))
|
|
return;
|
|
if (WARN_ON(!func->old_addr))
|
|
return;
|
|
|
|
ops = klp_find_ops(func->old_addr);
|
|
if (WARN_ON(!ops))
|
|
return;
|
|
|
|
if (list_is_singular(&ops->func_stack)) {
|
|
unsigned long ftrace_loc;
|
|
|
|
ftrace_loc = klp_get_ftrace_location(func->old_addr);
|
|
if (WARN_ON(!ftrace_loc))
|
|
return;
|
|
|
|
WARN_ON(unregister_ftrace_function(&ops->fops));
|
|
WARN_ON(ftrace_set_filter_ip(&ops->fops, ftrace_loc, 1, 0));
|
|
|
|
list_del_rcu(&func->stack_node);
|
|
list_del(&ops->node);
|
|
kfree(ops);
|
|
} else {
|
|
list_del_rcu(&func->stack_node);
|
|
}
|
|
|
|
func->patched = false;
|
|
}
|
|
|
|
static int klp_patch_func(struct klp_func *func)
|
|
{
|
|
struct klp_ops *ops;
|
|
int ret;
|
|
|
|
if (WARN_ON(!func->old_addr))
|
|
return -EINVAL;
|
|
|
|
if (WARN_ON(func->patched))
|
|
return -EINVAL;
|
|
|
|
ops = klp_find_ops(func->old_addr);
|
|
if (!ops) {
|
|
unsigned long ftrace_loc;
|
|
|
|
ftrace_loc = klp_get_ftrace_location(func->old_addr);
|
|
if (!ftrace_loc) {
|
|
pr_err("failed to find location for function '%s'\n",
|
|
func->old_name);
|
|
return -EINVAL;
|
|
}
|
|
|
|
ops = kzalloc(sizeof(*ops), GFP_KERNEL);
|
|
if (!ops)
|
|
return -ENOMEM;
|
|
|
|
ops->fops.func = klp_ftrace_handler;
|
|
ops->fops.flags = FTRACE_OPS_FL_SAVE_REGS |
|
|
FTRACE_OPS_FL_DYNAMIC |
|
|
FTRACE_OPS_FL_IPMODIFY;
|
|
|
|
list_add(&ops->node, &klp_ops);
|
|
|
|
INIT_LIST_HEAD(&ops->func_stack);
|
|
list_add_rcu(&func->stack_node, &ops->func_stack);
|
|
|
|
ret = ftrace_set_filter_ip(&ops->fops, ftrace_loc, 0, 0);
|
|
if (ret) {
|
|
pr_err("failed to set ftrace filter for function '%s' (%d)\n",
|
|
func->old_name, ret);
|
|
goto err;
|
|
}
|
|
|
|
ret = register_ftrace_function(&ops->fops);
|
|
if (ret) {
|
|
pr_err("failed to register ftrace handler for function '%s' (%d)\n",
|
|
func->old_name, ret);
|
|
ftrace_set_filter_ip(&ops->fops, ftrace_loc, 1, 0);
|
|
goto err;
|
|
}
|
|
|
|
|
|
} else {
|
|
list_add_rcu(&func->stack_node, &ops->func_stack);
|
|
}
|
|
|
|
func->patched = true;
|
|
|
|
return 0;
|
|
|
|
err:
|
|
list_del_rcu(&func->stack_node);
|
|
list_del(&ops->node);
|
|
kfree(ops);
|
|
return ret;
|
|
}
|
|
|
|
void klp_unpatch_object(struct klp_object *obj)
|
|
{
|
|
struct klp_func *func;
|
|
|
|
klp_for_each_func(obj, func)
|
|
if (func->patched)
|
|
klp_unpatch_func(func);
|
|
|
|
obj->patched = false;
|
|
}
|
|
|
|
int klp_patch_object(struct klp_object *obj)
|
|
{
|
|
struct klp_func *func;
|
|
int ret;
|
|
|
|
if (WARN_ON(obj->patched))
|
|
return -EINVAL;
|
|
|
|
klp_for_each_func(obj, func) {
|
|
ret = klp_patch_func(func);
|
|
if (ret) {
|
|
klp_unpatch_object(obj);
|
|
return ret;
|
|
}
|
|
}
|
|
obj->patched = true;
|
|
|
|
return 0;
|
|
}
|
|
|
|
void klp_unpatch_objects(struct klp_patch *patch)
|
|
{
|
|
struct klp_object *obj;
|
|
|
|
klp_for_each_object(patch, obj)
|
|
if (obj->patched)
|
|
klp_unpatch_object(obj);
|
|
}
|