120 lines
3.1 KiB
C
120 lines
3.1 KiB
C
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// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* system_state.c - State of the system modified by livepatches
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*
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* Copyright (C) 2019 SUSE
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/livepatch.h>
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#include "core.h"
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#include "state.h"
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#include "transition.h"
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#define klp_for_each_state(patch, state) \
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for (state = patch->states; state && state->id; state++)
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/**
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* klp_get_state() - get information about system state modified by
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* the given patch
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* @patch: livepatch that modifies the given system state
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* @id: custom identifier of the modified system state
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*
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* Checks whether the given patch modifies the given system state.
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*
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* The function can be called either from pre/post (un)patch
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* callbacks or from the kernel code added by the livepatch.
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*
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* Return: pointer to struct klp_state when found, otherwise NULL.
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*/
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struct klp_state *klp_get_state(struct klp_patch *patch, unsigned long id)
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{
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struct klp_state *state;
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klp_for_each_state(patch, state) {
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if (state->id == id)
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return state;
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}
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return NULL;
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}
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EXPORT_SYMBOL_GPL(klp_get_state);
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/**
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* klp_get_prev_state() - get information about system state modified by
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* the already installed livepatches
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* @id: custom identifier of the modified system state
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*
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* Checks whether already installed livepatches modify the given
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* system state.
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*
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* The same system state can be modified by more non-cumulative
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* livepatches. It is expected that the latest livepatch has
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* the most up-to-date information.
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*
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* The function can be called only during transition when a new
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* livepatch is being enabled or when such a transition is reverted.
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* It is typically called only from pre/post (un)patch
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* callbacks.
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*
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* Return: pointer to the latest struct klp_state from already
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* installed livepatches, NULL when not found.
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*/
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struct klp_state *klp_get_prev_state(unsigned long id)
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{
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struct klp_patch *patch;
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struct klp_state *state, *last_state = NULL;
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if (WARN_ON_ONCE(!klp_transition_patch))
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return NULL;
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klp_for_each_patch(patch) {
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if (patch == klp_transition_patch)
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goto out;
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state = klp_get_state(patch, id);
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if (state)
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last_state = state;
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}
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out:
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return last_state;
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}
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EXPORT_SYMBOL_GPL(klp_get_prev_state);
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/* Check if the patch is able to deal with the existing system state. */
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static bool klp_is_state_compatible(struct klp_patch *patch,
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struct klp_state *old_state)
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{
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struct klp_state *state;
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state = klp_get_state(patch, old_state->id);
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/* A cumulative livepatch must handle all already modified states. */
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if (!state)
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return !patch->replace;
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return state->version >= old_state->version;
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}
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/*
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* Check that the new livepatch will not break the existing system states.
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* Cumulative patches must handle all already modified states.
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* Non-cumulative patches can touch already modified states.
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*/
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bool klp_is_patch_compatible(struct klp_patch *patch)
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{
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struct klp_patch *old_patch;
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struct klp_state *old_state;
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klp_for_each_patch(old_patch) {
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klp_for_each_state(old_patch, old_state) {
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if (!klp_is_state_compatible(patch, old_state))
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return false;
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}
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}
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return true;
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}
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