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623 lines
16 KiB
623 lines
16 KiB
/* |
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* jump label support |
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* |
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* Copyright (C) 2009 Jason Baron <[email protected]> |
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* Copyright (C) 2011 Peter Zijlstra |
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* |
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*/ |
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#include <linux/memory.h> |
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#include <linux/uaccess.h> |
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#include <linux/module.h> |
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#include <linux/list.h> |
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#include <linux/slab.h> |
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#include <linux/sort.h> |
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#include <linux/err.h> |
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#include <linux/static_key.h> |
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#include <linux/jump_label_ratelimit.h> |
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#include <linux/bug.h> |
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#include <linux/mm.h> |
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|
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#ifdef HAVE_JUMP_LABEL |
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|
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/* mutex to protect coming/going of the the jump_label table */ |
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static DEFINE_MUTEX(jump_label_mutex); |
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|
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void jump_label_lock(void) |
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{ |
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mutex_lock(&jump_label_mutex); |
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} |
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|
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void jump_label_unlock(void) |
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{ |
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mutex_unlock(&jump_label_mutex); |
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} |
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|
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static int jump_label_cmp(const void *a, const void *b) |
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{ |
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const struct jump_entry *jea = a; |
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const struct jump_entry *jeb = b; |
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|
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if (jea->key < jeb->key) |
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return -1; |
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|
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if (jea->key > jeb->key) |
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return 1; |
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|
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return 0; |
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} |
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|
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static void |
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jump_label_sort_entries(struct jump_entry *start, struct jump_entry *stop) |
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{ |
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unsigned long size; |
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|
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size = (((unsigned long)stop - (unsigned long)start) |
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/ sizeof(struct jump_entry)); |
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pax_open_kernel(); |
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sort(start, size, sizeof(struct jump_entry), jump_label_cmp, NULL); |
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pax_close_kernel(); |
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} |
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|
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static void jump_label_update(struct static_key *key); |
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|
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/* |
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* There are similar definitions for the !HAVE_JUMP_LABEL case in jump_label.h. |
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* The use of 'atomic_read()' requires atomic.h and its problematic for some |
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* kernel headers such as kernel.h and others. Since static_key_count() is not |
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* used in the branch statements as it is for the !HAVE_JUMP_LABEL case its ok |
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* to have it be a function here. Similarly, for 'static_key_enable()' and |
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* 'static_key_disable()', which require bug.h. This should allow jump_label.h |
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* to be included from most/all places for HAVE_JUMP_LABEL. |
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*/ |
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int static_key_count(struct static_key *key) |
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{ |
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/* |
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* -1 means the first static_key_slow_inc() is in progress. |
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* static_key_enabled() must return true, so return 1 here. |
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*/ |
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int n = atomic_read(&key->enabled); |
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|
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return n >= 0 ? n : 1; |
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} |
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EXPORT_SYMBOL_GPL(static_key_count); |
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|
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void static_key_enable(struct static_key *key) |
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{ |
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int count = static_key_count(key); |
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|
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WARN_ON_ONCE(count < 0 || count > 1); |
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|
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if (!count) |
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static_key_slow_inc(key); |
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} |
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EXPORT_SYMBOL_GPL(static_key_enable); |
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|
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void static_key_disable(struct static_key *key) |
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{ |
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int count = static_key_count(key); |
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|
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WARN_ON_ONCE(count < 0 || count > 1); |
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|
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if (count) |
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static_key_slow_dec(key); |
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} |
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EXPORT_SYMBOL_GPL(static_key_disable); |
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|
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void static_key_slow_inc(struct static_key *key) |
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{ |
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int v, v1; |
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|
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STATIC_KEY_CHECK_USE(); |
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|
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/* |
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* Careful if we get concurrent static_key_slow_inc() calls; |
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* later calls must wait for the first one to _finish_ the |
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* jump_label_update() process. At the same time, however, |
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* the jump_label_update() call below wants to see |
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* static_key_enabled(&key) for jumps to be updated properly. |
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* |
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* So give a special meaning to negative key->enabled: it sends |
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* static_key_slow_inc() down the slow path, and it is non-zero |
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* so it counts as "enabled" in jump_label_update(). Note that |
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* atomic_inc_unless_negative() checks >= 0, so roll our own. |
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*/ |
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for (v = atomic_read(&key->enabled); v > 0; v = v1) { |
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v1 = atomic_cmpxchg(&key->enabled, v, v + 1); |
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if (likely(v1 == v)) |
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return; |
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} |
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|
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jump_label_lock(); |
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if (atomic_read(&key->enabled) == 0) { |
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atomic_set(&key->enabled, -1); |
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jump_label_update(key); |
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atomic_set(&key->enabled, 1); |
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} else { |
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atomic_inc(&key->enabled); |
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} |
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jump_label_unlock(); |
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} |
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EXPORT_SYMBOL_GPL(static_key_slow_inc); |
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|
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static void __static_key_slow_dec(struct static_key *key, |
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unsigned long rate_limit, struct delayed_work *work) |
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{ |
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/* |
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* The negative count check is valid even when a negative |
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* key->enabled is in use by static_key_slow_inc(); a |
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* __static_key_slow_dec() before the first static_key_slow_inc() |
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* returns is unbalanced, because all other static_key_slow_inc() |
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* instances block while the update is in progress. |
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*/ |
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if (!atomic_dec_and_mutex_lock(&key->enabled, &jump_label_mutex)) { |
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WARN(atomic_read(&key->enabled) < 0, |
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"jump label: negative count!\n"); |
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return; |
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} |
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|
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if (rate_limit) { |
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atomic_inc(&key->enabled); |
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schedule_delayed_work(work, rate_limit); |
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} else { |
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jump_label_update(key); |
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} |
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jump_label_unlock(); |
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} |
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|
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static void jump_label_update_timeout(struct work_struct *work) |
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{ |
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struct static_key_deferred *key = |
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container_of(work, struct static_key_deferred, work.work); |
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__static_key_slow_dec(&key->key, 0, NULL); |
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} |
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|
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void static_key_slow_dec(struct static_key *key) |
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{ |
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STATIC_KEY_CHECK_USE(); |
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__static_key_slow_dec(key, 0, NULL); |
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} |
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EXPORT_SYMBOL_GPL(static_key_slow_dec); |
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|
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void static_key_slow_dec_deferred(struct static_key_deferred *key) |
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{ |
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STATIC_KEY_CHECK_USE(); |
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__static_key_slow_dec(&key->key, key->timeout, &key->work); |
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} |
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EXPORT_SYMBOL_GPL(static_key_slow_dec_deferred); |
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|
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void static_key_deferred_flush(struct static_key_deferred *key) |
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{ |
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STATIC_KEY_CHECK_USE(); |
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flush_delayed_work(&key->work); |
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} |
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EXPORT_SYMBOL_GPL(static_key_deferred_flush); |
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|
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void jump_label_rate_limit(struct static_key_deferred *key, |
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unsigned long rl) |
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{ |
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STATIC_KEY_CHECK_USE(); |
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key->timeout = rl; |
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INIT_DELAYED_WORK(&key->work, jump_label_update_timeout); |
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} |
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EXPORT_SYMBOL_GPL(jump_label_rate_limit); |
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|
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static int addr_conflict(struct jump_entry *entry, void *start, void *end) |
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{ |
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if (entry->code <= (unsigned long)end && |
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entry->code + JUMP_LABEL_NOP_SIZE > (unsigned long)start) |
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return 1; |
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|
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return 0; |
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} |
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|
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static int __jump_label_text_reserved(struct jump_entry *iter_start, |
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struct jump_entry *iter_stop, void *start, void *end) |
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{ |
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struct jump_entry *iter; |
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|
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iter = iter_start; |
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while (iter < iter_stop) { |
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if (addr_conflict(iter, start, end)) |
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return 1; |
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iter++; |
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} |
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|
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return 0; |
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} |
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|
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/* |
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* Update code which is definitely not currently executing. |
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* Architectures which need heavyweight synchronization to modify |
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* running code can override this to make the non-live update case |
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* cheaper. |
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*/ |
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void __weak __init_or_module arch_jump_label_transform_static(struct jump_entry *entry, |
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enum jump_label_type type) |
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{ |
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arch_jump_label_transform(entry, type); |
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} |
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|
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static inline struct jump_entry *static_key_entries(struct static_key *key) |
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{ |
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return (struct jump_entry *)((unsigned long)key->entries & ~JUMP_TYPE_MASK); |
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} |
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|
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static inline bool static_key_type(struct static_key *key) |
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{ |
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return (unsigned long)key->entries & JUMP_TYPE_MASK; |
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} |
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|
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static inline struct static_key *jump_entry_key(struct jump_entry *entry) |
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{ |
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return (struct static_key *)((unsigned long)entry->key & ~1UL); |
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} |
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|
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static bool jump_entry_branch(struct jump_entry *entry) |
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{ |
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return (unsigned long)entry->key & 1UL; |
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} |
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|
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static enum jump_label_type jump_label_type(struct jump_entry *entry) |
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{ |
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struct static_key *key = jump_entry_key(entry); |
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bool enabled = static_key_enabled(key); |
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bool branch = jump_entry_branch(entry); |
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|
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/* See the comment in linux/jump_label.h */ |
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return enabled ^ branch; |
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} |
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|
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static void __jump_label_update(struct static_key *key, |
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struct jump_entry *entry, |
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struct jump_entry *stop) |
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{ |
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for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) { |
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/* |
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* entry->code set to 0 invalidates module init text sections |
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* kernel_text_address() verifies we are not in core kernel |
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* init code, see jump_label_invalidate_module_init(). |
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*/ |
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if (entry->code && kernel_text_address(entry->code)) |
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arch_jump_label_transform(entry, jump_label_type(entry)); |
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} |
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} |
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|
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void __init jump_label_init(void) |
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{ |
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struct jump_entry *iter_start = __start___jump_table; |
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struct jump_entry *iter_stop = __stop___jump_table; |
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struct static_key *key = NULL; |
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struct jump_entry *iter; |
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|
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/* |
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* Since we are initializing the static_key.enabled field with |
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* with the 'raw' int values (to avoid pulling in atomic.h) in |
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* jump_label.h, let's make sure that is safe. There are only two |
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* cases to check since we initialize to 0 or 1. |
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*/ |
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BUILD_BUG_ON((int)ATOMIC_INIT(0) != 0); |
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BUILD_BUG_ON((int)ATOMIC_INIT(1) != 1); |
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|
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if (static_key_initialized) |
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return; |
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jump_label_lock(); |
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jump_label_sort_entries(iter_start, iter_stop); |
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for (iter = iter_start; iter < iter_stop; iter++) { |
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struct static_key *iterk; |
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|
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/* rewrite NOPs */ |
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if (jump_label_type(iter) == JUMP_LABEL_NOP) |
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arch_jump_label_transform_static(iter, JUMP_LABEL_NOP); |
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|
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iterk = jump_entry_key(iter); |
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if (iterk == key) |
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continue; |
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|
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key = iterk; |
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/* |
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* Set key->entries to iter, but preserve JUMP_LABEL_TRUE_BRANCH. |
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*/ |
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*((unsigned long *)&key->entries) += (unsigned long)iter; |
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#ifdef CONFIG_MODULES |
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key->next = NULL; |
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#endif |
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} |
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static_key_initialized = true; |
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jump_label_unlock(); |
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} |
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|
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#ifdef CONFIG_MODULES |
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|
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static enum jump_label_type jump_label_init_type(struct jump_entry *entry) |
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{ |
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struct static_key *key = jump_entry_key(entry); |
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bool type = static_key_type(key); |
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bool branch = jump_entry_branch(entry); |
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|
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/* See the comment in linux/jump_label.h */ |
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return type ^ branch; |
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} |
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|
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struct static_key_mod { |
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struct static_key_mod *next; |
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struct jump_entry *entries; |
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struct module *mod; |
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}; |
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static int __jump_label_mod_text_reserved(void *start, void *end) |
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{ |
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struct module *mod; |
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preempt_disable(); |
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mod = __module_text_address((unsigned long)start); |
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WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod); |
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preempt_enable(); |
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if (!mod) |
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return 0; |
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return __jump_label_text_reserved(mod->jump_entries, |
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mod->jump_entries + mod->num_jump_entries, |
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start, end); |
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} |
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|
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static void __jump_label_mod_update(struct static_key *key) |
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{ |
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struct static_key_mod *mod; |
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|
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for (mod = key->next; mod; mod = mod->next) { |
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struct module *m = mod->mod; |
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|
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__jump_label_update(key, mod->entries, |
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m->jump_entries + m->num_jump_entries); |
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} |
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} |
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|
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/*** |
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* apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop() |
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* @mod: module to patch |
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* |
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* Allow for run-time selection of the optimal nops. Before the module |
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* loads patch these with arch_get_jump_label_nop(), which is specified by |
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* the arch specific jump label code. |
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*/ |
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void jump_label_apply_nops(struct module *mod) |
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{ |
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struct jump_entry *iter_start = mod->jump_entries; |
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struct jump_entry *iter_stop = iter_start + mod->num_jump_entries; |
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struct jump_entry *iter; |
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|
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/* if the module doesn't have jump label entries, just return */ |
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if (iter_start == iter_stop) |
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return; |
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|
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for (iter = iter_start; iter < iter_stop; iter++) { |
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/* Only write NOPs for arch_branch_static(). */ |
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if (jump_label_init_type(iter) == JUMP_LABEL_NOP) |
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arch_jump_label_transform_static(iter, JUMP_LABEL_NOP); |
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} |
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} |
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|
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static int jump_label_add_module(struct module *mod) |
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{ |
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struct jump_entry *iter_start = mod->jump_entries; |
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struct jump_entry *iter_stop = iter_start + mod->num_jump_entries; |
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struct jump_entry *iter; |
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struct static_key *key = NULL; |
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struct static_key_mod *jlm; |
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|
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/* if the module doesn't have jump label entries, just return */ |
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if (iter_start == iter_stop) |
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return 0; |
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|
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jump_label_sort_entries(iter_start, iter_stop); |
|
|
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for (iter = iter_start; iter < iter_stop; iter++) { |
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struct static_key *iterk; |
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|
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iterk = jump_entry_key(iter); |
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if (iterk == key) |
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continue; |
|
|
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key = iterk; |
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if (within_module(iter->key, mod)) { |
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/* |
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* Set key->entries to iter, but preserve JUMP_LABEL_TRUE_BRANCH. |
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*/ |
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*((unsigned long *)&key->entries) += (unsigned long)iter; |
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key->next = NULL; |
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continue; |
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} |
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jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL); |
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if (!jlm) |
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return -ENOMEM; |
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jlm->mod = mod; |
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jlm->entries = iter; |
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jlm->next = key->next; |
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key->next = jlm; |
|
|
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/* Only update if we've changed from our initial state */ |
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if (jump_label_type(iter) != jump_label_init_type(iter)) |
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__jump_label_update(key, iter, iter_stop); |
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} |
|
|
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return 0; |
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} |
|
|
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static void jump_label_del_module(struct module *mod) |
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{ |
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struct jump_entry *iter_start = mod->jump_entries; |
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struct jump_entry *iter_stop = iter_start + mod->num_jump_entries; |
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struct jump_entry *iter; |
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struct static_key *key = NULL; |
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struct static_key_mod *jlm, **prev; |
|
|
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for (iter = iter_start; iter < iter_stop; iter++) { |
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if (jump_entry_key(iter) == key) |
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continue; |
|
|
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key = jump_entry_key(iter); |
|
|
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if (within_module(iter->key, mod)) |
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continue; |
|
|
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prev = &key->next; |
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jlm = key->next; |
|
|
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while (jlm && jlm->mod != mod) { |
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prev = &jlm->next; |
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jlm = jlm->next; |
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} |
|
|
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if (jlm) { |
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*prev = jlm->next; |
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kfree(jlm); |
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} |
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} |
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} |
|
|
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static void jump_label_invalidate_module_init(struct module *mod) |
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{ |
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struct jump_entry *iter_start = mod->jump_entries; |
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struct jump_entry *iter_stop = iter_start + mod->num_jump_entries; |
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struct jump_entry *iter; |
|
|
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pax_open_kernel(); |
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for (iter = iter_start; iter < iter_stop; iter++) { |
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if (within_module_init(iter->code, mod)) |
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iter->code = 0; |
|
} |
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pax_close_kernel(); |
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} |
|
|
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static int |
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jump_label_module_notify(struct notifier_block *self, unsigned long val, |
|
void *data) |
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{ |
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struct module *mod = data; |
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int ret = 0; |
|
|
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switch (val) { |
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case MODULE_STATE_COMING: |
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jump_label_lock(); |
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ret = jump_label_add_module(mod); |
|
if (ret) |
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jump_label_del_module(mod); |
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jump_label_unlock(); |
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break; |
|
case MODULE_STATE_GOING: |
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jump_label_lock(); |
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jump_label_del_module(mod); |
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jump_label_unlock(); |
|
break; |
|
case MODULE_STATE_LIVE: |
|
jump_label_lock(); |
|
jump_label_invalidate_module_init(mod); |
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jump_label_unlock(); |
|
break; |
|
} |
|
|
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return notifier_from_errno(ret); |
|
} |
|
|
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static struct notifier_block jump_label_module_nb = { |
|
.notifier_call = jump_label_module_notify, |
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.priority = 1, /* higher than tracepoints */ |
|
}; |
|
|
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static __init int jump_label_init_module(void) |
|
{ |
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return register_module_notifier(&jump_label_module_nb); |
|
} |
|
early_initcall(jump_label_init_module); |
|
|
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#endif /* CONFIG_MODULES */ |
|
|
|
/*** |
|
* jump_label_text_reserved - check if addr range is reserved |
|
* @start: start text addr |
|
* @end: end text addr |
|
* |
|
* checks if the text addr located between @start and @end |
|
* overlaps with any of the jump label patch addresses. Code |
|
* that wants to modify kernel text should first verify that |
|
* it does not overlap with any of the jump label addresses. |
|
* Caller must hold jump_label_mutex. |
|
* |
|
* returns 1 if there is an overlap, 0 otherwise |
|
*/ |
|
int jump_label_text_reserved(void *start, void *end) |
|
{ |
|
int ret = __jump_label_text_reserved(__start___jump_table, |
|
__stop___jump_table, start, end); |
|
|
|
if (ret) |
|
return ret; |
|
|
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#ifdef CONFIG_MODULES |
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ret = __jump_label_mod_text_reserved(start, end); |
|
#endif |
|
return ret; |
|
} |
|
|
|
static void jump_label_update(struct static_key *key) |
|
{ |
|
struct jump_entry *stop = __stop___jump_table; |
|
struct jump_entry *entry = static_key_entries(key); |
|
#ifdef CONFIG_MODULES |
|
struct module *mod; |
|
|
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__jump_label_mod_update(key); |
|
|
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preempt_disable(); |
|
mod = __module_address((unsigned long)key); |
|
if (mod) |
|
stop = mod->jump_entries + mod->num_jump_entries; |
|
preempt_enable(); |
|
#endif |
|
/* if there are no users, entry can be NULL */ |
|
if (entry) |
|
__jump_label_update(key, entry, stop); |
|
} |
|
|
|
#ifdef CONFIG_STATIC_KEYS_SELFTEST |
|
static DEFINE_STATIC_KEY_TRUE(sk_true); |
|
static DEFINE_STATIC_KEY_FALSE(sk_false); |
|
|
|
static __init int jump_label_test(void) |
|
{ |
|
int i; |
|
|
|
for (i = 0; i < 2; i++) { |
|
WARN_ON(static_key_enabled(&sk_true.key) != true); |
|
WARN_ON(static_key_enabled(&sk_false.key) != false); |
|
|
|
WARN_ON(!static_branch_likely(&sk_true)); |
|
WARN_ON(!static_branch_unlikely(&sk_true)); |
|
WARN_ON(static_branch_likely(&sk_false)); |
|
WARN_ON(static_branch_unlikely(&sk_false)); |
|
|
|
static_branch_disable(&sk_true); |
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static_branch_enable(&sk_false); |
|
|
|
WARN_ON(static_key_enabled(&sk_true.key) == true); |
|
WARN_ON(static_key_enabled(&sk_false.key) == false); |
|
|
|
WARN_ON(static_branch_likely(&sk_true)); |
|
WARN_ON(static_branch_unlikely(&sk_true)); |
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WARN_ON(!static_branch_likely(&sk_false)); |
|
WARN_ON(!static_branch_unlikely(&sk_false)); |
|
|
|
static_branch_enable(&sk_true); |
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static_branch_disable(&sk_false); |
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} |
|
|
|
return 0; |
|
} |
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late_initcall(jump_label_test); |
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#endif /* STATIC_KEYS_SELFTEST */ |
|
|
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#endif /* HAVE_JUMP_LABEL */
|
|
|