/* * Copyright (C) 2017 Joe Lawrence <joe.lawrence@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/>. */ /* * livepatch-callbacks-demo.c - (un)patching callbacks livepatch demo * * * Purpose * ------- * * Demonstration of registering livepatch (un)patching callbacks. * * * Usage * ----- * * Step 1 - load the simple module * *   insmod samples/livepatch/livepatch-callbacks-mod.ko * * * Step 2 - load the demonstration livepatch (with callbacks) * *   insmod samples/livepatch/livepatch-callbacks-demo.ko * * * Step 3 - cleanup * *   echo 0 > /sys/kernel/livepatch/livepatch_callbacks_demo/enabled *   rmmod livepatch_callbacks_demo *   rmmod livepatch_callbacks_mod * * Watch dmesg output to see livepatch enablement, callback execution * and patching operations for both vmlinux and module targets. * * NOTE: swap the insmod order of livepatch-callbacks-mod.ko and *       livepatch-callbacks-demo.ko to observe what happens when a *       target module is loaded after a livepatch with callbacks. * * NOTE: 'pre_patch_ret' is a module parameter that sets the pre-patch *       callback return status.  Try setting up a non-zero status *       such as -19 (-ENODEV): * *       # Load demo livepatch, vmlinux is patched *       insmod samples/livepatch/livepatch-callbacks-demo.ko * *       # Setup next pre-patch callback to return -ENODEV *       echo -19 > /sys/module/livepatch_callbacks_demo/parameters/pre_patch_ret * *       # Module loader refuses to load the target module *       insmod samples/livepatch/livepatch-callbacks-mod.ko *       insmod: ERROR: could not insert module samples/livepatch/livepatch-callbacks-mod.ko: No such device * * NOTE: There is a second target module, *       livepatch-callbacks-busymod.ko, available for experimenting *       with livepatch (un)patch callbacks.  This module contains *       a 'sleep_secs' parameter that parks the module on one of the *       functions that the livepatch demo module wants to patch. *       Modifying this value and tweaking the order of module loads can *       effectively demonstrate stalled patch transitions: * *       # Load a target module, let it park on 'busymod_work_func' for *       # thirty seconds *       insmod samples/livepatch/livepatch-callbacks-busymod.ko sleep_secs=30 * *       # Meanwhile load the livepatch *       insmod samples/livepatch/livepatch-callbacks-demo.ko * *       # ... then load and unload another target module while the *       # transition is in progress *       insmod samples/livepatch/livepatch-callbacks-mod.ko *       rmmod samples/livepatch/livepatch-callbacks-mod.ko * *       # Finally cleanup *       echo 0 > /sys/kernel/livepatch/livepatch_callbacks_demo/enabled *       rmmod samples/livepatch/livepatch-callbacks-demo.ko */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include <linux/module.h>#include <linux/kernel.h>#include <linux/livepatch.h> static int pre_patch_ret;module_param(pre_patch_ret, int, 0644);MODULE_PARM_DESC(pre_patch_ret, "pre_patch_ret (default=0)"); static const char *const module_state[] = {	[MODULE_STATE_LIVE]	= "[MODULE_STATE_LIVE] Normal state",	[MODULE_STATE_COMING]	= "[MODULE_STATE_COMING] Full formed, running module_init",	[MODULE_STATE_GOING]	= "[MODULE_STATE_GOING] Going away",	[MODULE_STATE_UNFORMED]	= "[MODULE_STATE_UNFORMED] Still setting it up",}; static void callback_info(const char *callback, struct klp_object *obj){	if (obj->mod)		pr_info("%s: %s -> %s\n", callback, obj->mod->name,			module_state[obj->mod->state]);	else		pr_info("%s: vmlinux\n", callback);} /* Executed on object patching (ie, patch enablement) */static int pre_patch_callback(struct klp_object *obj){	callback_info(__func__, obj);	return pre_patch_ret;} /* Executed on object unpatching (ie, patch disablement) */static void post_patch_callback(struct klp_object *obj){	callback_info(__func__, obj);} /* Executed on object unpatching (ie, patch disablement) */static void pre_unpatch_callback(struct klp_object *obj){	callback_info(__func__, obj);} /* Executed on object unpatching (ie, patch disablement) */static void post_unpatch_callback(struct klp_object *obj){	callback_info(__func__, obj);} static void patched_work_func(struct work_struct *work){	pr_info("%s\n", __func__);} static struct klp_func no_funcs[] = {	{ }}; static struct klp_func busymod_funcs[] = {	{		.old_name = "busymod_work_func",		.new_func = patched_work_func,	}, { }}; static struct klp_object objs[] = {	{		.name = NULL,	/* vmlinux */		.funcs = no_funcs,		.callbacks = {			.pre_patch = pre_patch_callback,			.post_patch = post_patch_callback,			.pre_unpatch = pre_unpatch_callback,			.post_unpatch = post_unpatch_callback,		},	},	{		.name = "livepatch_callbacks_mod",		.funcs = no_funcs,		.callbacks = {			.pre_patch = pre_patch_callback,			.post_patch = post_patch_callback,			.pre_unpatch = pre_unpatch_callback,			.post_unpatch = post_unpatch_callback,		},	},	{		.name = "livepatch_callbacks_busymod",		.funcs = busymod_funcs,		.callbacks = {			.pre_patch = pre_patch_callback,			.post_patch = post_patch_callback,			.pre_unpatch = pre_unpatch_callback,			.post_unpatch = post_unpatch_callback,		},	}, { }}; static struct klp_patch patch = {	.mod = THIS_MODULE,	.objs = objs,}; static int livepatch_callbacks_demo_init(void){	int ret; 	ret = klp_register_patch(&patch);	if (ret)		return ret;	ret = klp_enable_patch(&patch);	if (ret) {		WARN_ON(klp_unregister_patch(&patch));		return ret;	}	return 0;} static void livepatch_callbacks_demo_exit(void){	WARN_ON(klp_unregister_patch(&patch));} module_init(livepatch_callbacks_demo_init);module_exit(livepatch_callbacks_demo_exit);MODULE_LICENSE("GPL");MODULE_INFO(livepatch, "Y");