kernel/livepatch/state.c

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