GNU Linux-libre 6.6.15-gnu
[releases.git] / samples / livepatch / livepatch-shadow-fix2.c
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * Copyright (C) 2017 Joe Lawrence <joe.lawrence@redhat.com>
4  */
5
6 /*
7  * livepatch-shadow-fix2.c - Shadow variables, livepatch demo
8  *
9  * Purpose
10  * -------
11  *
12  * Adds functionality to livepatch-shadow-mod's in-flight data
13  * structures through a shadow variable.  The livepatch patches a
14  * routine that periodically inspects data structures, incrementing a
15  * per-data-structure counter, creating the counter if needed.
16  *
17  *
18  * Usage
19  * -----
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 ": " fmt
26
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         1
34 #define SV_COUNTER      2
35
36 struct dummy {
37         struct list_head list;
38         unsigned long jiffies_expire;
39 };
40
41 static 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 not
47          * already have a SV_COUNTER shadow variable, then attach a
48          * 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
59 static 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
69 static 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         else
79                 pr_info("%s: dummy @ %p leaked!\n", __func__, d);
80
81         /*
82          * Patch: fetch the SV_COUNTER shadow variable and display
83          * 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
95 static 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
106 static struct klp_object objs[] = {
107         {
108                 .name = "livepatch_shadow_mod",
109                 .funcs = funcs,
110         }, { }
111 };
112
113 static struct klp_patch patch = {
114         .mod = THIS_MODULE,
115         .objs = objs,
116 };
117
118 static int livepatch_shadow_fix2_init(void)
119 {
120         return klp_enable_patch(&patch);
121 }
122
123 static 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
129 module_init(livepatch_shadow_fix2_init);
130 module_exit(livepatch_shadow_fix2_exit);
131 MODULE_LICENSE("GPL");
132 MODULE_INFO(livepatch, "Y");