1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * system_state.c - State of the system modified by livepatches
4 *
5 * Copyright (C) 2019 SUSE
6 */
7
8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
9
10 #include <linux/livepatch.h>
11 #include "core.h"
12 #include "state.h"
13 #include "transition.h"
14
15 #define klp_for_each_state(patch, state) \
16 for (state = patch->states; state && state->id; state++)
17
18 /**
19 * klp_get_state() - get information about system state modified by
20 * the given patch
21 * @patch: livepatch that modifies the given system state
22 * @id: custom identifier of the modified system state
23 *
24 * Checks whether the given patch modifies the given system state.
25 *
26 * The function can be called either from pre/post (un)patch
27 * callbacks or from the kernel code added by the livepatch.
28 *
29 * Return: pointer to struct klp_state when found, otherwise NULL.
30 */
31 struct klp_state *klp_get_state(struct klp_patch *patch, unsigned long id)
32 {
33 struct klp_state *state;
34
35 klp_for_each_state(patch, state) {
36 if (state->id == id)
37 return state;
38 }
39
40 return NULL;
41 }
42 EXPORT_SYMBOL_GPL(klp_get_state);
43
44 /**
45 * klp_get_prev_state() - get information about system state modified by
46 * the already installed livepatches
47 * @id: custom identifier of the modified system state
48 *
49 * Checks whether already installed livepatches modify the given
50 * system state.
51 *
52 * The same system state can be modified by more non-cumulative
53 * livepatches. It is expected that the latest livepatch has
54 * the most up-to-date information.
55 *
56 * The function can be called only during transition when a new
57 * livepatch is being enabled or when such a transition is reverted.
58 * It is typically called only from pre/post (un)patch
59 * callbacks.
60 *
61 * Return: pointer to the latest struct klp_state from already
62 * installed livepatches, NULL when not found.
63 */
64 struct klp_state *klp_get_prev_state(unsigned long id)
65 {
66 struct klp_patch *patch;
67 struct klp_state *state, *last_state = NULL;
68
69 if (WARN_ON_ONCE(!klp_transition_patch))
70 return NULL;
71
72 klp_for_each_patch(patch) {
73 if (patch == klp_transition_patch)
74 goto out;
75
76 state = klp_get_state(patch, id);
77 if (state)
78 last_state = state;
79 }
80
81 out:
82 return last_state;
83 }
84 EXPORT_SYMBOL_GPL(klp_get_prev_state);
85
86 /* Check if the patch is able to deal with the existing system state. */
87 static bool klp_is_state_compatible(struct klp_patch *patch,
88 struct klp_state *old_state)
89 {
90 struct klp_state *state;
91
92 state = klp_get_state(patch, old_state->id);
93
94 /* A cumulative livepatch must handle all already modified states. */
95 if (!state)
96 return !patch->replace;
97
98 return state->version >= old_state->version;
99 }
100
101 /*
102 * Check that the new livepatch will not break the existing system states.
103 * Cumulative patches must handle all already modified states.
104 * Non-cumulative patches can touch already modified states.
105 */
106 bool klp_is_patch_compatible(struct klp_patch *patch)
107 {
108 struct klp_patch *old_patch;
109 struct klp_state *old_state;
110
111 klp_for_each_patch(old_patch) {
112 klp_for_each_state(old_patch, old_state) {
113 if (!klp_is_state_compatible(patch, old_state))
114 return false;
115 }
116 }
117
118 return true;
119 }
120
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