/* * 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-shadow-fix2.c - Shadow variables, livepatch demo * * Purpose * ------- * * Adds functionality to livepatch-shadow-mod's in-flight data * structures through a shadow variable.  The livepatch patches a * routine that periodically inspects data structures, incrementing a * per-data-structure counter, creating the counter if needed. * * * Usage * ----- * * This module is not intended to be standalone.  See the "Usage" * section of livepatch-shadow-mod.c. */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include <linux/module.h>#include <linux/kernel.h>#include <linux/livepatch.h>#include <linux/slab.h> /* Shadow variable enums */#define SV_LEAK		1#define SV_COUNTER	2 struct dummy {	struct list_head list;	unsigned long jiffies_expire;}; bool livepatch_fix2_dummy_check(struct dummy *d, unsigned long jiffies){	int *shadow_count;	int count; 	/*	 * Patch: handle in-flight dummy structures, if they do not	 * already have a SV_COUNTER shadow variable, then attach a	 * new one.	 */	count = 0;	shadow_count = klp_shadow_get_or_alloc(d, SV_COUNTER,					       &count, sizeof(count),					       GFP_NOWAIT);	if (shadow_count)		*shadow_count += 1; 	return time_after(jiffies, d->jiffies_expire);} void livepatch_fix2_dummy_free(struct dummy *d){	void **shadow_leak, *leak;	int *shadow_count; 	/* Patch: copy the memory leak patch from the fix1 module. */	shadow_leak = klp_shadow_get(d, SV_LEAK);	if (shadow_leak) {		leak = *shadow_leak;		klp_shadow_free(d, SV_LEAK);		kfree(leak);		pr_info("%s: dummy @ %p, prevented leak @ %p\n",			 __func__, d, leak);	} else {		pr_info("%s: dummy @ %p leaked!\n", __func__, d);	} 	/*	 * Patch: fetch the SV_COUNTER shadow variable and display	 * the final count.  Detach the shadow variable.	 */	shadow_count = klp_shadow_get(d, SV_COUNTER);	if (shadow_count) {		pr_info("%s: dummy @ %p, check counter = %d\n",			__func__, d, *shadow_count);		klp_shadow_free(d, SV_COUNTER);	} 	kfree(d);} static struct klp_func funcs[] = {	{		.old_name = "dummy_check",		.new_func = livepatch_fix2_dummy_check,	},	{		.old_name = "dummy_free",		.new_func = livepatch_fix2_dummy_free,	}, { }}; static struct klp_object objs[] = {	{		.name = "livepatch_shadow_mod",		.funcs = funcs,	}, { }}; static struct klp_patch patch = {	.mod = THIS_MODULE,	.objs = objs,}; static int livepatch_shadow_fix2_init(void){	int ret; 	if (!klp_have_reliable_stack() && !patch.immediate) {		/*		 * WARNING: Be very careful when using 'patch.immediate' in		 * your patches.  It's ok to use it for simple patches like		 * this, but for more complex patches which change function		 * semantics, locking semantics, or data structures, it may not		 * be safe.  Use of this option will also prevent removal of		 * the patch.		 *		 * See Documentation/livepatch/livepatch.txt for more details.		 */		patch.immediate = true;		pr_notice("The consistency model isn't supported for your architecture.  Bypassing safety mechanisms and applying the patch immediately.\n");	} 	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_shadow_fix2_exit(void){	/* Cleanup any existing SV_COUNTER shadow variables */	klp_shadow_free_all(SV_COUNTER); 	WARN_ON(klp_unregister_patch(&patch));} module_init(livepatch_shadow_fix2_init);module_exit(livepatch_shadow_fix2_exit);MODULE_LICENSE("GPL");MODULE_INFO(livepatch, "Y");