cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
Log | Files | Refs | README | LICENSE | sfeed.txt

state.c (3148B)

      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}