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 | |