// SPDX-License-Identifier: GPL-2.0-or-later/* * Copyright (C) 2017 Joe Lawrence <joe.lawrence@redhat.com> */ /* * 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;}; static bool livepatch_fix2_dummy_check(struct dummy *d, unsigned long jiffies){	int *shadow_count; 	/*	 * Patch: handle in-flight dummy structures, if they do not	 * already have a SV_COUNTER shadow variable, then attach a	 * new one.	 */	shadow_count = klp_shadow_get_or_alloc(d, SV_COUNTER,				sizeof(*shadow_count), GFP_NOWAIT,				NULL, NULL);	if (shadow_count)		*shadow_count += 1; 	return time_after(jiffies, d->jiffies_expire);} static void livepatch_fix2_dummy_leak_dtor(void *obj, void *shadow_data){	void *d = obj;	int **shadow_leak = shadow_data; 	pr_info("%s: dummy @ %p, prevented leak @ %p\n",			 __func__, d, *shadow_leak);	kfree(*shadow_leak);} static void livepatch_fix2_dummy_free(struct dummy *d){	int **shadow_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)		klp_shadow_free(d, SV_LEAK, livepatch_fix2_dummy_leak_dtor);	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, NULL);	} 	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){	return klp_enable_patch(&patch);} static void livepatch_shadow_fix2_exit(void){	/* Cleanup any existing SV_COUNTER shadow variables */	klp_shadow_free_all(SV_COUNTER, NULL);} module_init(livepatch_shadow_fix2_init);module_exit(livepatch_shadow_fix2_exit);MODULE_DESCRIPTION("Live patching demo for shadow variables");MODULE_LICENSE("GPL");MODULE_INFO(livepatch, "Y");