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(obj: d, SV_COUNTER, |
51 | size: 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(objp: *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(obj: d, SV_LEAK); |
76 | if (shadow_leak) |
77 | klp_shadow_free(obj: d, SV_LEAK, dtor: 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(obj: 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(obj: d, SV_COUNTER, NULL); |
90 | } |
91 | |
92 | kfree(objp: 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" ); |
133 | |