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