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1// SPDX-License-Identifier: GPL-2.0-or-later2/*3 * Copyright (C) 2017 Joe Lawrence <joe.lawrence@redhat.com>4 */5 6/*7 * livepatch-shadow-fix2.c - Shadow variables, livepatch demo8 *9 * Purpose10 * -------11 *12 * Adds functionality to livepatch-shadow-mod's in-flight data13 * structures through a shadow variable. The livepatch patches a14 * routine that periodically inspects data structures, incrementing a15 * per-data-structure counter, creating the counter if needed.16 *17 *18 * Usage19 * -----20 *21 * This module is not intended to be standalone. See the "Usage"22 * section of livepatch-shadow-mod.c.23 */24 25#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt26 27#include <linux/module.h>28#include <linux/kernel.h>29#include <linux/livepatch.h>30#include <linux/slab.h>31 32/* Shadow variable enums */33#define SV_LEAK 134#define SV_COUNTER 235 36struct dummy {37 struct list_head list;38 unsigned long jiffies_expire;39};40 41static bool livepatch_fix2_dummy_check(struct dummy *d, unsigned long jiffies)42{43 int *shadow_count;44 45 /*46 * Patch: handle in-flight dummy structures, if they do not47 * already have a SV_COUNTER shadow variable, then attach a48 * new one.49 */50 shadow_count = klp_shadow_get_or_alloc(d, SV_COUNTER,51 sizeof(*shadow_count), GFP_NOWAIT,52 NULL, NULL);53 if (shadow_count)54 *shadow_count += 1;55 56 return time_after(jiffies, d->jiffies_expire);57}58 59static void livepatch_fix2_dummy_leak_dtor(void *obj, void *shadow_data)60{61 void *d = obj;62 int **shadow_leak = shadow_data;63 64 pr_info("%s: dummy @ %p, prevented leak @ %p\n",65 __func__, d, *shadow_leak);66 kfree(*shadow_leak);67}68 69static void livepatch_fix2_dummy_free(struct dummy *d)70{71 int **shadow_leak;72 int *shadow_count;73 74 /* Patch: copy the memory leak patch from the fix1 module. */75 shadow_leak = klp_shadow_get(d, SV_LEAK);76 if (shadow_leak)77 klp_shadow_free(d, SV_LEAK, livepatch_fix2_dummy_leak_dtor);78 else79 pr_info("%s: dummy @ %p leaked!\n", __func__, d);80 81 /*82 * Patch: fetch the SV_COUNTER shadow variable and display83 * the final count. Detach the shadow variable.84 */85 shadow_count = klp_shadow_get(d, SV_COUNTER);86 if (shadow_count) {87 pr_info("%s: dummy @ %p, check counter = %d\n",88 __func__, d, *shadow_count);89 klp_shadow_free(d, SV_COUNTER, NULL);90 }91 92 kfree(d);93}94 95static struct klp_func funcs[] = {96 {97 .old_name = "dummy_check",98 .new_func = livepatch_fix2_dummy_check,99 },100 {101 .old_name = "dummy_free",102 .new_func = livepatch_fix2_dummy_free,103 }, { }104};105 106static struct klp_object objs[] = {107 {108 .name = "livepatch_shadow_mod",109 .funcs = funcs,110 }, { }111};112 113static struct klp_patch patch = {114 .mod = THIS_MODULE,115 .objs = objs,116};117 118static int livepatch_shadow_fix2_init(void)119{120 return klp_enable_patch(&patch);121}122 123static void livepatch_shadow_fix2_exit(void)124{125 /* Cleanup any existing SV_COUNTER shadow variables */126 klp_shadow_free_all(SV_COUNTER, NULL);127}128 129module_init(livepatch_shadow_fix2_init);130module_exit(livepatch_shadow_fix2_exit);131MODULE_LICENSE("GPL");132MODULE_INFO(livepatch, "Y");133