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 */
31struct 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}
42EXPORT_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 */
64struct 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
81out:
82	return last_state;
83}
84EXPORT_SYMBOL_GPL(klp_get_prev_state);
85
86/* Check if the patch is able to deal with the existing system state. */
87static 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 */
106bool 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