| 1 | |
| 2 | |
| 3 | * system_state.c - State of the system modified by livepatches
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| 4 | *
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| 5 | * Copyright (C) 2019 SUSE
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| 6 |
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| 7 |
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| 8 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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| 9 |
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| 10 | #include <linux/livepatch.h>
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| 11 | #include "core.h"
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| 12 | #include "state.h"
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| 13 | #include "transition.h"
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| 14 |
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| 15 | #define klp_for_each_state(patch, state) \
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| 16 | for (state = patch->states; state && state->id; state++)
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| 17 |
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| 18 | |
| 19 | * klp_get_state() - get information about system state modified by
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| 20 | * the given patch
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| 21 | * @patch: livepatch that modifies the given system state
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| 22 | * @id: custom identifier of the modified system state
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| 23 | *
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| 24 | * Checks whether the given patch modifies the given system state.
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| 25 | *
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| 26 | * The function can be called either from pre/post (un)patch
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| 27 | * callbacks or from the kernel code added by the livepatch.
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| 28 | *
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| 29 | * Return: pointer to struct klp_state when found, otherwise NULL.
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| 30 |
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| 31 | struct klp_state *klp_get_state(struct klp_patch *patch, unsigned long id)
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| 32 | {
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| 33 | struct klp_state *state;
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| 34 |
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| 35 | klp_for_each_state(patch, state) {
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| 36 | if (state->id == id)
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| 37 | return state;
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| 38 | }
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| 39 |
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| 40 | return NULL;
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| 41 | }
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| 42 | EXPORT_SYMBOL_GPL(klp_get_state);
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| 43 |
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| 44 | |
| 45 | * klp_get_prev_state() - get information about system state modified by
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| 46 | * the already installed livepatches
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| 47 | * @id: custom identifier of the modified system state
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| 48 | *
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| 49 | * Checks whether already installed livepatches modify the given
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| 50 | * system state.
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| 51 | *
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| 52 | * The same system state can be modified by more non-cumulative
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| 53 | * livepatches. It is expected that the latest livepatch has
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| 54 | * the most up-to-date information.
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| 55 | *
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| 56 | * The function can be called only during transition when a new
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| 57 | * livepatch is being enabled or when such a transition is reverted.
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| 58 | * It is typically called only from pre/post (un)patch
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| 59 | * callbacks.
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| 60 | *
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| 61 | * Return: pointer to the latest struct klp_state from already
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| 62 | * installed livepatches, NULL when not found.
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| 63 |
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| 64 | struct klp_state *klp_get_prev_state(unsigned long id)
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| 65 | {
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| 66 | struct klp_patch *patch;
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| 67 | struct klp_state *state, *last_state = NULL;
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| 68 |
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| 69 | if (WARN_ON_ONCE(!klp_transition_patch))
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| 70 | return NULL;
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| 71 |
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| 72 | klp_for_each_patch(patch) {
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| 73 | if (patch == klp_transition_patch)
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| 74 | goto out;
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| 75 |
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| 76 | state = klp_get_state(patch, id);
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| 77 | if (state)
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| 78 | last_state = state;
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| 79 | }
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| 80 |
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| 81 | out:
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| 82 | return last_state;
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| 83 | }
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| 84 | EXPORT_SYMBOL_GPL(klp_get_prev_state);
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| 85 |
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| 86 |
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| 87 | static bool klp_is_state_compatible(struct klp_patch *patch,
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| 88 | struct klp_state *old_state)
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| 89 | {
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| 90 | struct klp_state *state;
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| 91 |
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| 92 | state = klp_get_state(patch, old_state->id);
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| 93 |
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| 94 |
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| 95 | if (!state)
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| 96 | return !patch->replace;
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| 97 |
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| 98 | return state->version >= old_state->version;
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| 99 | }
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| 100 |
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| 101 | |
| 102 | * Check that the new livepatch will not break the existing system states.
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| 103 | * Cumulative patches must handle all already modified states.
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| 104 | * Non-cumulative patches can touch already modified states.
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| 105 |
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| 106 | bool klp_is_patch_compatible(struct klp_patch *patch)
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| 107 | {
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| 108 | struct klp_patch *old_patch;
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| 109 | struct klp_state *old_state;
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| 110 |
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| 111 | klp_for_each_patch(old_patch) {
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| 112 | klp_for_each_state(old_patch, old_state) {
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| 113 | if (!klp_is_state_compatible(patch, old_state))
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| 114 | return false;
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| 115 | }
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| 116 | }
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| 117 |
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| 118 | return true;
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| 119 | }
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