Release 4.15 kernel/livepatch/patch.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;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Josh Poimboeuf | 60 | 100.00% | 1 | 100.00% |
| Total | 60 | 100.00% | 1 | 100.00% |
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();
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Josh Poimboeuf | 168 | 98.25% | 2 | 66.67% |
| Petr Mladek | 3 | 1.75% | 1 | 33.33% |
| Total | 171 | 100.00% | 3 | 100.00% |
/*
* 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;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Josh Poimboeuf | 14 | 100.00% | 1 | 100.00% |
| Total | 14 | 100.00% | 1 | 100.00% |
#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;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Josh Poimboeuf | 156 | 100.00% | 1 | 100.00% |
| Total | 156 | 100.00% | 1 | 100.00% |
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;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Josh Poimboeuf | 300 | 100.00% | 1 | 100.00% |
| Total | 300 | 100.00% | 1 | 100.00% |
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;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Josh Poimboeuf | 38 | 100.00% | 1 | 100.00% |
| Total | 38 | 100.00% | 1 | 100.00% |
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;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Josh Poimboeuf | 69 | 100.00% | 1 | 100.00% |
| Total | 69 | 100.00% | 1 | 100.00% |
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);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Josh Poimboeuf | 32 | 100.00% | 1 | 100.00% |
| Total | 32 | 100.00% | 1 | 100.00% |
Overall Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Josh Poimboeuf | 884 | 99.33% | 2 | 50.00% |
| Joe Lawrence | 3 | 0.34% | 1 | 25.00% |
| Petr Mladek | 3 | 0.34% | 1 | 25.00% |
| Total | 890 | 100.00% | 4 | 100.00% |
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