290 lines
6.4 KiB
C
290 lines
6.4 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
|
|
/*
|
|
* 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>
|
|
*/
|
|
|
|
#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(void *old_func)
|
|
{
|
|
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_func == old_func)
|
|
return ops;
|
|
}
|
|
|
|
return NULL;
|
|
}
|
|
|
|
static void notrace klp_ftrace_handler(unsigned long ip,
|
|
unsigned long parent_ip,
|
|
struct ftrace_ops *fops,
|
|
struct ftrace_regs *fregs)
|
|
{
|
|
struct klp_ops *ops;
|
|
struct klp_func *func;
|
|
int patch_state;
|
|
int bit;
|
|
|
|
ops = container_of(fops, struct klp_ops, fops);
|
|
|
|
/*
|
|
* The ftrace_test_recursion_trylock() will disable preemption,
|
|
* which is required for the variant of synchronize_rcu() that is
|
|
* used to allow patching functions where RCU is not watching.
|
|
* See klp_synchronize_transition() for more details.
|
|
*/
|
|
bit = ftrace_test_recursion_trylock(ip, parent_ip);
|
|
if (WARN_ON_ONCE(bit < 0))
|
|
return;
|
|
|
|
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_rcu() 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;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* NOPs are used to replace existing patches with original code.
|
|
* Do nothing! Setting pc would cause an infinite loop.
|
|
*/
|
|
if (func->nop)
|
|
goto unlock;
|
|
|
|
ftrace_instruction_pointer_set(fregs, (unsigned long)func->new_func);
|
|
|
|
unlock:
|
|
ftrace_test_recursion_unlock(bit);
|
|
}
|
|
|
|
static void klp_unpatch_func(struct klp_func *func)
|
|
{
|
|
struct klp_ops *ops;
|
|
|
|
if (WARN_ON(!func->patched))
|
|
return;
|
|
if (WARN_ON(!func->old_func))
|
|
return;
|
|
|
|
ops = klp_find_ops(func->old_func);
|
|
if (WARN_ON(!ops))
|
|
return;
|
|
|
|
if (list_is_singular(&ops->func_stack)) {
|
|
unsigned long ftrace_loc;
|
|
|
|
ftrace_loc = ftrace_location((unsigned long)func->old_func);
|
|
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_func))
|
|
return -EINVAL;
|
|
|
|
if (WARN_ON(func->patched))
|
|
return -EINVAL;
|
|
|
|
ops = klp_find_ops(func->old_func);
|
|
if (!ops) {
|
|
unsigned long ftrace_loc;
|
|
|
|
ftrace_loc = ftrace_location((unsigned long)func->old_func);
|
|
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_DYNAMIC |
|
|
#ifndef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
|
|
FTRACE_OPS_FL_SAVE_REGS |
|
|
#endif
|
|
FTRACE_OPS_FL_IPMODIFY |
|
|
FTRACE_OPS_FL_PERMANENT;
|
|
|
|
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;
|
|
}
|
|
|
|
static void __klp_unpatch_object(struct klp_object *obj, bool nops_only)
|
|
{
|
|
struct klp_func *func;
|
|
|
|
klp_for_each_func(obj, func) {
|
|
if (nops_only && !func->nop)
|
|
continue;
|
|
|
|
if (func->patched)
|
|
klp_unpatch_func(func);
|
|
}
|
|
|
|
if (obj->dynamic || !nops_only)
|
|
obj->patched = false;
|
|
}
|
|
|
|
|
|
void klp_unpatch_object(struct klp_object *obj)
|
|
{
|
|
__klp_unpatch_object(obj, 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;
|
|
}
|
|
|
|
static void __klp_unpatch_objects(struct klp_patch *patch, bool nops_only)
|
|
{
|
|
struct klp_object *obj;
|
|
|
|
klp_for_each_object(patch, obj)
|
|
if (obj->patched)
|
|
__klp_unpatch_object(obj, nops_only);
|
|
}
|
|
|
|
void klp_unpatch_objects(struct klp_patch *patch)
|
|
{
|
|
__klp_unpatch_objects(patch, false);
|
|
}
|
|
|
|
void klp_unpatch_objects_dynamic(struct klp_patch *patch)
|
|
{
|
|
__klp_unpatch_objects(patch, true);
|
|
}
|