path: root/kernel/livepatch/core.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * core.c - Kernel Live Patching Core
 *
 * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
 * Copyright (C) 2014 SUSE
 */

#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/list.h>
#include <linux/kallsyms.h>
#include <linux/livepatch.h>
#include <linux/elf.h>
#include <linux/moduleloader.h>
#include <linux/completion.h>
#include <linux/memory.h>
#include <asm/cacheflush.h>
#include "core.h"
#include "patch.h"
#include "state.h"
#include "transition.h"

/*
 * klp_mutex is a coarse lock which serializes access to klp data.  All
 * accesses to klp-related variables and structures must have mutex protection,
 * except within the following functions which carefully avoid the need for it:
 *
 * - klp_ftrace_handler()
 * - klp_update_patch_state()
 */
DEFINE_MUTEX(klp_mutex);

/*
 * Actively used patches: enabled or in transition. Note that replaced
 * or disabled patches are not listed even though the related kernel
 * module still can be loaded.
 */
LIST_HEAD(klp_patches);

static struct kobject *klp_root_kobj;

static bool klp_is_module(struct klp_object *obj)
{
	return obj->name;
}

/* 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
	 * klp_module_going() instead.
	 */
	mod = find_module(obj->name);
	/*
	 * Do not mess work of klp_module_coming() and klp_module_going().
	 * Note that the patch might still be needed before klp_module_going()
	 * 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);
}

static bool klp_initialized(void)
{
	return !!klp_root_kobj;
}

static struct klp_func *klp_find_func(struct klp_object *obj,
				      struct klp_func *old_func)
{
	struct klp_func *func;

	klp_for_each_func(obj, func) {
		if ((strcmp(old_func->old_name, func->old_name) == 0) &&
		    (old_func->old_sympos == func->old_sympos)) {
			return func;
		}
	}

	return NULL;
}

static struct klp_object *klp_find_object(struct klp_patch *patch,
					  struct klp_object *old_obj)
{
	struct klp_object *obj;

	klp_for_each_object(patch, obj) {
		if (klp_is_module(old_obj)) {
			if (klp_is_module(obj) &&
			    strcmp(old_obj->name, obj->name) == 0) {
				return obj;
			}
		} else if (!klp_is_module(obj)) {
			return obj;
		}
	}

	return NULL;
}

struct klp_find_arg {
	const char *objname;
	const char *name;
	unsigned long addr;
	unsigned long count;
	unsigned long pos;
};

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 &&