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![Thomas Gleixner](/assets/img/avatar_default.png)
The conversion of the hotplug locking to a percpu rwsem unearthed lock ordering issues all over the place. The jump_label code has two issues: 1) Nested get_online_cpus() invocations 2) Ordering problems vs. the cpus rwsem and the jump_label_mutex To cure these, the following lock order has been established; cpus_rwsem -> jump_label_lock -> text_mutex Even if not all architectures need protection against CPU hotplug, taking cpus_rwsem before jump_label_lock is now mandatory in code pathes which actually modify code and therefor need text_mutex protection. Move the get_online_cpus() invocations into the core jump label code and establish the proper lock order where required. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Ingo Molnar <mingo@kernel.org> Acked-by: "David S. Miller" <davem@davemloft.net> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Chris Metcalf <cmetcalf@mellanox.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Siewior <bigeasy@linutronix.de> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Jason Baron <jbaron@akamai.com> Cc: Ralf Baechle <ralf@linux-mips.org> Link: http://lkml.kernel.org/r/20170524081549.025830817@linutronix.de
727 lines
18 KiB
C
727 lines
18 KiB
C
/*
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* jump label support
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*
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* Copyright (C) 2009 Jason Baron <jbaron@redhat.com>
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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/cpu.h>
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#ifdef HAVE_JUMP_LABEL
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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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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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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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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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if (jea->key < jeb->key)
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return -1;
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if (jea->key > jeb->key)
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return 1;
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return 0;
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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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size = (((unsigned long)stop - (unsigned long)start)
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/ sizeof(struct jump_entry));
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sort(start, size, sizeof(struct jump_entry), jump_label_cmp, NULL);
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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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* 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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return n >= 0 ? n : 1;
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}
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EXPORT_SYMBOL_GPL(static_key_count);
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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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WARN_ON_ONCE(count < 0 || count > 1);
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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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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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WARN_ON_ONCE(count < 0 || count > 1);
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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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void static_key_slow_inc(struct static_key *key)
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{
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int v, v1;
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STATIC_KEY_CHECK_USE();
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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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cpus_read_lock();
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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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cpus_read_unlock();
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}
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EXPORT_SYMBOL_GPL(static_key_slow_inc);
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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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cpus_read_lock();
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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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cpus_read_unlock();
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return;
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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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cpus_read_unlock();
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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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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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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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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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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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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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return 0;
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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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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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return 0;
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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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static inline struct jump_entry *static_key_entries(struct static_key *key)
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{
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WARN_ON_ONCE(key->type & JUMP_TYPE_LINKED);
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return (struct jump_entry *)(key->type & ~JUMP_TYPE_MASK);
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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 key->type & JUMP_TYPE_TRUE;
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}
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static inline bool static_key_linked(struct static_key *key)
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{
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return key->type & JUMP_TYPE_LINKED;
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}
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static inline void static_key_clear_linked(struct static_key *key)
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{
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key->type &= ~JUMP_TYPE_LINKED;
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}
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static inline void static_key_set_linked(struct static_key *key)
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{
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key->type |= JUMP_TYPE_LINKED;
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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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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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* A 'struct static_key' uses a union such that it either points directly
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* to a table of 'struct jump_entry' or to a linked list of modules which in
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* turn point to 'struct jump_entry' tables.
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*
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* The two lower bits of the pointer are used to keep track of which pointer
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* type is in use and to store the initial branch direction, we use an access
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* function which preserves these bits.
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*/
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static void static_key_set_entries(struct static_key *key,
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struct jump_entry *entries)
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{
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unsigned long type;
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WARN_ON_ONCE((unsigned long)entries & JUMP_TYPE_MASK);
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type = key->type & JUMP_TYPE_MASK;
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key->entries = entries;
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key->type |= type;
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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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/* See the comment in linux/jump_label.h */
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return enabled ^ branch;
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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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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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* 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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if (static_key_initialized)
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return;
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cpus_read_lock();
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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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/* 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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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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static_key_set_entries(key, iter);
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}
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static_key_initialized = true;
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jump_label_unlock();
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cpus_read_unlock();
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}
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#ifdef CONFIG_MODULES
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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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/* See the comment in linux/jump_label.h */
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return type ^ branch;
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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 inline struct static_key_mod *static_key_mod(struct static_key *key)
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{
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WARN_ON_ONCE(!(key->type & JUMP_TYPE_LINKED));
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return (struct static_key_mod *)(key->type & ~JUMP_TYPE_MASK);
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}
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/***
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* key->type and key->next are the same via union.
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* This sets key->next and preserves the type bits.
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*
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* See additional comments above static_key_set_entries().
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*/
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static void static_key_set_mod(struct static_key *key,
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struct static_key_mod *mod)
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{
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unsigned long type;
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WARN_ON_ONCE((unsigned long)mod & JUMP_TYPE_MASK);
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type = key->type & JUMP_TYPE_MASK;
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key->next = mod;
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key->type |= type;
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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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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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for (mod = static_key_mod(key); mod; mod = mod->next) {
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struct jump_entry *stop;
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struct module *m;
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/*
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* NULL if the static_key is defined in a module
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* that does not use it
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*/
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if (!mod->entries)
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continue;
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m = mod->mod;
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if (!m)
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stop = __stop___jump_table;
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else
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stop = m->jump_entries + m->num_jump_entries;
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__jump_label_update(key, mod->entries, stop);
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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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/* 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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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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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, *jlm2;
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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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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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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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static_key_set_entries(key, iter);
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continue;
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}
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jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL);
|
|
if (!jlm)
|
|
return -ENOMEM;
|
|
if (!static_key_linked(key)) {
|
|
jlm2 = kzalloc(sizeof(struct static_key_mod),
|
|
GFP_KERNEL);
|
|
if (!jlm2) {
|
|
kfree(jlm);
|
|
return -ENOMEM;
|
|
}
|
|
preempt_disable();
|
|
jlm2->mod = __module_address((unsigned long)key);
|
|
preempt_enable();
|
|
jlm2->entries = static_key_entries(key);
|
|
jlm2->next = NULL;
|
|
static_key_set_mod(key, jlm2);
|
|
static_key_set_linked(key);
|
|
}
|
|
jlm->mod = mod;
|
|
jlm->entries = iter;
|
|
jlm->next = static_key_mod(key);
|
|
static_key_set_mod(key, jlm);
|
|
static_key_set_linked(key);
|
|
|
|
/* Only update if we've changed from our initial state */
|
|
if (jump_label_type(iter) != jump_label_init_type(iter))
|
|
__jump_label_update(key, iter, iter_stop);
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static void jump_label_del_module(struct module *mod)
|
|
{
|
|
struct jump_entry *iter_start = mod->jump_entries;
|
|
struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
|
|
struct jump_entry *iter;
|
|
struct static_key *key = NULL;
|
|
struct static_key_mod *jlm, **prev;
|
|
|
|
for (iter = iter_start; iter < iter_stop; iter++) {
|
|
if (jump_entry_key(iter) == key)
|
|
continue;
|
|
|
|
key = jump_entry_key(iter);
|
|
|
|
if (within_module(iter->key, mod))
|
|
continue;
|
|
|
|
/* No memory during module load */
|
|
if (WARN_ON(!static_key_linked(key)))
|
|
continue;
|
|
|
|
prev = &key->next;
|
|
jlm = static_key_mod(key);
|
|
|
|
while (jlm && jlm->mod != mod) {
|
|
prev = &jlm->next;
|
|
jlm = jlm->next;
|
|
}
|
|
|
|
/* No memory during module load */
|
|
if (WARN_ON(!jlm))
|
|
continue;
|
|
|
|
if (prev == &key->next)
|
|
static_key_set_mod(key, jlm->next);
|
|
else
|
|
*prev = jlm->next;
|
|
|
|
kfree(jlm);
|
|
|
|
jlm = static_key_mod(key);
|
|
/* if only one etry is left, fold it back into the static_key */
|
|
if (jlm->next == NULL) {
|
|
static_key_set_entries(key, jlm->entries);
|
|
static_key_clear_linked(key);
|
|
kfree(jlm);
|
|
}
|
|
}
|
|
}
|
|
|
|
static void jump_label_invalidate_module_init(struct module *mod)
|
|
{
|
|
struct jump_entry *iter_start = mod->jump_entries;
|
|
struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
|
|
struct jump_entry *iter;
|
|
|
|
for (iter = iter_start; iter < iter_stop; iter++) {
|
|
if (within_module_init(iter->code, mod))
|
|
iter->code = 0;
|
|
}
|
|
}
|
|
|
|
static int
|
|
jump_label_module_notify(struct notifier_block *self, unsigned long val,
|
|
void *data)
|
|
{
|
|
struct module *mod = data;
|
|
int ret = 0;
|
|
|
|
cpus_read_lock();
|
|
jump_label_lock();
|
|
|
|
switch (val) {
|
|
case MODULE_STATE_COMING:
|
|
ret = jump_label_add_module(mod);
|
|
if (ret) {
|
|
WARN(1, "Failed to allocatote memory: jump_label may not work properly.\n");
|
|
jump_label_del_module(mod);
|
|
}
|
|
break;
|
|
case MODULE_STATE_GOING:
|
|
jump_label_del_module(mod);
|
|
break;
|
|
case MODULE_STATE_LIVE:
|
|
jump_label_invalidate_module_init(mod);
|
|
break;
|
|
}
|
|
|
|
jump_label_unlock();
|
|
cpus_read_unlock();
|
|
|
|
return notifier_from_errno(ret);
|
|
}
|
|
|
|
static struct notifier_block jump_label_module_nb = {
|
|
.notifier_call = jump_label_module_notify,
|
|
.priority = 1, /* higher than tracepoints */
|
|
};
|
|
|
|
static __init int jump_label_init_module(void)
|
|
{
|
|
return register_module_notifier(&jump_label_module_nb);
|
|
}
|
|
early_initcall(jump_label_init_module);
|
|
|
|
#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;
|
|
|
|
#ifdef CONFIG_MODULES
|
|
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;
|
|
#ifdef CONFIG_MODULES
|
|
struct module *mod;
|
|
|
|
if (static_key_linked(key)) {
|
|
__jump_label_mod_update(key);
|
|
return;
|
|
}
|
|
|
|
preempt_disable();
|
|
mod = __module_address((unsigned long)key);
|
|
if (mod)
|
|
stop = mod->jump_entries + mod->num_jump_entries;
|
|
preempt_enable();
|
|
#endif
|
|
entry = static_key_entries(key);
|
|
/* 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);
|
|
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));
|
|
WARN_ON(!static_branch_likely(&sk_false));
|
|
WARN_ON(!static_branch_unlikely(&sk_false));
|
|
|
|
static_branch_enable(&sk_true);
|
|
static_branch_disable(&sk_false);
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
late_initcall(jump_label_test);
|
|
#endif /* STATIC_KEYS_SELFTEST */
|
|
|
|
#endif /* HAVE_JUMP_LABEL */
|