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}