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1ccea77e | 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
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2 | /* |
3 | * Copyright (C) 2017 Joe Lawrence <joe.lawrence@redhat.com> | |
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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 | ||
b73d5dc7 | 41 | static bool livepatch_fix2_dummy_check(struct dummy *d, unsigned long jiffies) |
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42 | { |
43 | int *shadow_count; | |
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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 | */ | |
439e7271 | 50 | shadow_count = klp_shadow_get_or_alloc(d, SV_COUNTER, |
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51 | sizeof(*shadow_count), GFP_NOWAIT, |
52 | NULL, NULL); | |
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53 | if (shadow_count) |
54 | *shadow_count += 1; | |
55 | ||
56 | return time_after(jiffies, d->jiffies_expire); | |
57 | } | |
58 | ||
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59 | static void livepatch_fix2_dummy_leak_dtor(void *obj, void *shadow_data) |
60 | { | |
61 | void *d = obj; | |
8f6b8866 | 62 | int **shadow_leak = shadow_data; |
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63 | |
64 | kfree(*shadow_leak); | |
65 | pr_info("%s: dummy @ %p, prevented leak @ %p\n", | |
66 | __func__, d, *shadow_leak); | |
67 | } | |
68 | ||
b73d5dc7 | 69 | static void livepatch_fix2_dummy_free(struct dummy *d) |
439e7271 | 70 | { |
8f6b8866 | 71 | int **shadow_leak; |
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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); | |
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76 | if (shadow_leak) |
77 | klp_shadow_free(d, SV_LEAK, livepatch_fix2_dummy_leak_dtor); | |
78 | else | |
439e7271 | 79 | pr_info("%s: dummy @ %p leaked!\n", __func__, d); |
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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); | |
3b2c77d0 | 89 | klp_shadow_free(d, SV_COUNTER, NULL); |
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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 | { | |
958ef1e3 | 120 | return klp_enable_patch(&patch); |
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121 | } |
122 | ||
123 | static void livepatch_shadow_fix2_exit(void) | |
124 | { | |
125 | /* Cleanup any existing SV_COUNTER shadow variables */ | |
3b2c77d0 | 126 | klp_shadow_free_all(SV_COUNTER, NULL); |
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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"); |