11ccea77eSThomas Gleixner // SPDX-License-Identifier: GPL-2.0-or-later
2439e7271SJoe Lawrence /*
3439e7271SJoe Lawrence * Copyright (C) 2017 Joe Lawrence <joe.lawrence@redhat.com>
4439e7271SJoe Lawrence */
5439e7271SJoe Lawrence
6439e7271SJoe Lawrence /*
7439e7271SJoe Lawrence * livepatch-shadow-fix2.c - Shadow variables, livepatch demo
8439e7271SJoe Lawrence *
9439e7271SJoe Lawrence * Purpose
10439e7271SJoe Lawrence * -------
11439e7271SJoe Lawrence *
12439e7271SJoe Lawrence * Adds functionality to livepatch-shadow-mod's in-flight data
13439e7271SJoe Lawrence * structures through a shadow variable. The livepatch patches a
14439e7271SJoe Lawrence * routine that periodically inspects data structures, incrementing a
15439e7271SJoe Lawrence * per-data-structure counter, creating the counter if needed.
16439e7271SJoe Lawrence *
17439e7271SJoe Lawrence *
18439e7271SJoe Lawrence * Usage
19439e7271SJoe Lawrence * -----
20439e7271SJoe Lawrence *
21439e7271SJoe Lawrence * This module is not intended to be standalone. See the "Usage"
22439e7271SJoe Lawrence * section of livepatch-shadow-mod.c.
23439e7271SJoe Lawrence */
24439e7271SJoe Lawrence
25439e7271SJoe Lawrence #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
26439e7271SJoe Lawrence
27439e7271SJoe Lawrence #include <linux/module.h>
28439e7271SJoe Lawrence #include <linux/kernel.h>
29439e7271SJoe Lawrence #include <linux/livepatch.h>
30439e7271SJoe Lawrence #include <linux/slab.h>
31439e7271SJoe Lawrence
32439e7271SJoe Lawrence /* Shadow variable enums */
33439e7271SJoe Lawrence #define SV_LEAK 1
34439e7271SJoe Lawrence #define SV_COUNTER 2
35439e7271SJoe Lawrence
36439e7271SJoe Lawrence struct dummy {
37439e7271SJoe Lawrence struct list_head list;
38439e7271SJoe Lawrence unsigned long jiffies_expire;
39439e7271SJoe Lawrence };
40439e7271SJoe Lawrence
livepatch_fix2_dummy_check(struct dummy * d,unsigned long jiffies)41b73d5dc7SNicholas Mc Guire static bool livepatch_fix2_dummy_check(struct dummy *d, unsigned long jiffies)
42439e7271SJoe Lawrence {
43439e7271SJoe Lawrence int *shadow_count;
44439e7271SJoe Lawrence
45439e7271SJoe Lawrence /*
46439e7271SJoe Lawrence * Patch: handle in-flight dummy structures, if they do not
47439e7271SJoe Lawrence * already have a SV_COUNTER shadow variable, then attach a
48439e7271SJoe Lawrence * new one.
49439e7271SJoe Lawrence */
50439e7271SJoe Lawrence shadow_count = klp_shadow_get_or_alloc(d, SV_COUNTER,
51e91c2518SPetr Mladek sizeof(*shadow_count), GFP_NOWAIT,
52e91c2518SPetr Mladek NULL, NULL);
53439e7271SJoe Lawrence if (shadow_count)
54439e7271SJoe Lawrence *shadow_count += 1;
55439e7271SJoe Lawrence
56439e7271SJoe Lawrence return time_after(jiffies, d->jiffies_expire);
57439e7271SJoe Lawrence }
58439e7271SJoe Lawrence
livepatch_fix2_dummy_leak_dtor(void * obj,void * shadow_data)593b2c77d0SPetr Mladek static void livepatch_fix2_dummy_leak_dtor(void *obj, void *shadow_data)
603b2c77d0SPetr Mladek {
613b2c77d0SPetr Mladek void *d = obj;
628f6b8866SPetr Mladek int **shadow_leak = shadow_data;
633b2c77d0SPetr Mladek
643b2c77d0SPetr Mladek pr_info("%s: dummy @ %p, prevented leak @ %p\n",
653b2c77d0SPetr Mladek __func__, d, *shadow_leak);
66*5e6ded2eSTom Rix kfree(*shadow_leak);
673b2c77d0SPetr Mladek }
683b2c77d0SPetr Mladek
livepatch_fix2_dummy_free(struct dummy * d)69b73d5dc7SNicholas Mc Guire static void livepatch_fix2_dummy_free(struct dummy *d)
70439e7271SJoe Lawrence {
718f6b8866SPetr Mladek int **shadow_leak;
72439e7271SJoe Lawrence int *shadow_count;
73439e7271SJoe Lawrence
74439e7271SJoe Lawrence /* Patch: copy the memory leak patch from the fix1 module. */
75439e7271SJoe Lawrence shadow_leak = klp_shadow_get(d, SV_LEAK);
763b2c77d0SPetr Mladek if (shadow_leak)
773b2c77d0SPetr Mladek klp_shadow_free(d, SV_LEAK, livepatch_fix2_dummy_leak_dtor);
783b2c77d0SPetr Mladek else
79439e7271SJoe Lawrence pr_info("%s: dummy @ %p leaked!\n", __func__, d);
80439e7271SJoe Lawrence
81439e7271SJoe Lawrence /*
82439e7271SJoe Lawrence * Patch: fetch the SV_COUNTER shadow variable and display
83439e7271SJoe Lawrence * the final count. Detach the shadow variable.
84439e7271SJoe Lawrence */
85439e7271SJoe Lawrence shadow_count = klp_shadow_get(d, SV_COUNTER);
86439e7271SJoe Lawrence if (shadow_count) {
87439e7271SJoe Lawrence pr_info("%s: dummy @ %p, check counter = %d\n",
88439e7271SJoe Lawrence __func__, d, *shadow_count);
893b2c77d0SPetr Mladek klp_shadow_free(d, SV_COUNTER, NULL);
90439e7271SJoe Lawrence }
91439e7271SJoe Lawrence
92439e7271SJoe Lawrence kfree(d);
93439e7271SJoe Lawrence }
94439e7271SJoe Lawrence
95439e7271SJoe Lawrence static struct klp_func funcs[] = {
96439e7271SJoe Lawrence {
97439e7271SJoe Lawrence .old_name = "dummy_check",
98439e7271SJoe Lawrence .new_func = livepatch_fix2_dummy_check,
99439e7271SJoe Lawrence },
100439e7271SJoe Lawrence {
101439e7271SJoe Lawrence .old_name = "dummy_free",
102439e7271SJoe Lawrence .new_func = livepatch_fix2_dummy_free,
103439e7271SJoe Lawrence }, { }
104439e7271SJoe Lawrence };
105439e7271SJoe Lawrence
106439e7271SJoe Lawrence static struct klp_object objs[] = {
107439e7271SJoe Lawrence {
108439e7271SJoe Lawrence .name = "livepatch_shadow_mod",
109439e7271SJoe Lawrence .funcs = funcs,
110439e7271SJoe Lawrence }, { }
111439e7271SJoe Lawrence };
112439e7271SJoe Lawrence
113439e7271SJoe Lawrence static struct klp_patch patch = {
114439e7271SJoe Lawrence .mod = THIS_MODULE,
115439e7271SJoe Lawrence .objs = objs,
116439e7271SJoe Lawrence };
117439e7271SJoe Lawrence
livepatch_shadow_fix2_init(void)118439e7271SJoe Lawrence static int livepatch_shadow_fix2_init(void)
119439e7271SJoe Lawrence {
120958ef1e3SPetr Mladek return klp_enable_patch(&patch);
121439e7271SJoe Lawrence }
122439e7271SJoe Lawrence
livepatch_shadow_fix2_exit(void)123439e7271SJoe Lawrence static void livepatch_shadow_fix2_exit(void)
124439e7271SJoe Lawrence {
125439e7271SJoe Lawrence /* Cleanup any existing SV_COUNTER shadow variables */
1263b2c77d0SPetr Mladek klp_shadow_free_all(SV_COUNTER, NULL);
127439e7271SJoe Lawrence }
128439e7271SJoe Lawrence
129439e7271SJoe Lawrence module_init(livepatch_shadow_fix2_init);
130439e7271SJoe Lawrence module_exit(livepatch_shadow_fix2_exit);
131439e7271SJoe Lawrence MODULE_LICENSE("GPL");
132439e7271SJoe Lawrence MODULE_INFO(livepatch, "Y");
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