/*
* core.c - 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/>.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/ftrace.h>
#include <linux/list.h>
#include <linux/kallsyms.h>
#include <linux/livepatch.h>
/**
* struct klp_ops - structure for tracking registered ftrace ops structs
*
* A single ftrace_ops is shared between all enabled replacement functions
* (klp_func structs) which have the same old_addr. This allows the switch
* between function versions to happen instantaneously by updating the klp_ops
* struct's func_stack list. The winner is the klp_func at the top of the
* func_stack (front of the list).
*
* @node: node for the global klp_ops list
* @func_stack: list head for the stack of klp_func's (active func is on top)
* @fops: registered ftrace ops struct
*/
struct klp_ops {
struct list_head node;
struct list_head func_stack;
struct ftrace_ops fops;
};
/*
* The klp_mutex protects the global lists and state transitions of any
* structure reachable from them. References to any structure must be obtained
* under mutex protection (except in klp_ftrace_handler(), which uses RCU to
* ensure it gets consistent data).
*/
static DEFINE_MUTEX(klp_mutex);
static LIST_HEAD(klp_patches);
static LIST_HEAD(klp_ops);
static struct kobject *klp_root_kobj;
static 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 bool klp_is_module(struct klp_object *obj)
{
return obj->name;
}
static bool klp_is_object_loaded(struct klp_object *obj)
{
return !obj->name || obj->mod;
}
/* sets obj->mod if object is not vmlinux and module is found */
static void klp_find_object_module(struct klp_object *obj)
{
struct module *mod;
if (!klp_is_module(obj))
return;
mutex_lock(&module_mutex);
/*
* We do not want to block removal of patched modules and therefore
* we do not take a reference here. The patches are removed by
* a going module handler instead.
*/
mod = find_module(obj->name);
/*
* Do not mess work of the module coming and going notifiers.
* Note that the patch might still be needed before the going handler
* is called. Module functions can be called even in the GOING state
* until mod->exit() finishes. This is especially important for
* patches that modify semantic of the functions.
*/
if (mod && mod->klp_alive)
obj->mod = mod;
mutex_unlock(&module_mutex);
}
/* klp_mutex must be held by caller */
static bool klp_is_patch_registered(struct klp_patch *patch)
{
struct klp_patch *mypatch;
list_for_each_entry(mypatch, &klp_patches, list)
if (mypatch == patch)
return true;
return false;
}
static bool klp_initialized(void)
{
return !!klp_root_kobj;
}
struct klp_find_arg {
const char *objname;
const char *name;
unsigned long addr;
/*
* If count == 0, the symbol was not found. If count == 1, a unique
* match was found and addr is set. If count > 1, there is
* unresolvable ambiguity among "count" number of symbols with the same
* name in the same object.
*/
unsigned long count;
};
static int klp_find_callback(void *data, const char *name,
struct module *mod, unsigned long addr)
{
struct klp_find_arg *args = data;
if ((mod && !args->objname) || (!mod && args->objname))
return 0;
if (strcmp(args->name, name))
return 0;
if (args->objname && strcmp(args->objname, mod->name))
return 0;
/*
* args->addr might be overwritten if another match is found
* but klp_find_object_symbol() handles this and only returns the
* addr if count == 1.
*/
args->addr = addr;
args->count++;
return 0;
}
static int klp_find_object_symbol(const char *objname, const char *name,
unsigned long *addr)
{
struct klp_find_arg args = {
.objname = objname,
.name = name,
.addr = 0,
.count = 0
};
mutex_lock(&module_mutex);
kallsyms_on_each_symbol(klp_find_callback, &args);
mutex_unlock(&module_mutex);
if (args.count == 0)
pr_err