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460 lines
11 KiB
460 lines
11 KiB
/*
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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 <pzijlstr@redhat.com>
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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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#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, int enable);
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void static_key_slow_inc(struct static_key *key)
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{
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STATIC_KEY_CHECK_USE();
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if (atomic_inc_not_zero(&key->enabled))
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return;
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jump_label_lock();
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if (atomic_read(&key->enabled) == 0) {
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if (!jump_label_get_branch_default(key))
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jump_label_update(key, JUMP_LABEL_ENABLE);
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else
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jump_label_update(key, JUMP_LABEL_DISABLE);
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}
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atomic_inc(&key->enabled);
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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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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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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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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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if (!jump_label_get_branch_default(key))
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jump_label_update(key, JUMP_LABEL_DISABLE);
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else
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jump_label_update(key, JUMP_LABEL_ENABLE);
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}
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jump_label_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 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 void __jump_label_update(struct static_key *key,
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struct jump_entry *entry,
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struct jump_entry *stop, int enable)
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{
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for (; (entry < stop) &&
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(entry->key == (jump_label_t)(unsigned long)key);
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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, enable);
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}
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}
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static enum jump_label_type jump_label_type(struct static_key *key)
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{
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bool true_branch = jump_label_get_branch_default(key);
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bool state = static_key_enabled(key);
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if ((!true_branch && state) || (true_branch && !state))
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return JUMP_LABEL_ENABLE;
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return JUMP_LABEL_DISABLE;
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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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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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iterk = (struct static_key *)(unsigned long)iter->key;
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arch_jump_label_transform_static(iter, jump_label_type(iterk));
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if (iterk == key)
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continue;
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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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#ifdef CONFIG_MODULES
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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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mod = __module_text_address((unsigned long)start);
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if (!mod)
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return 0;
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WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
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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, int enable)
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{
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struct static_key_mod *mod = key->next;
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while (mod) {
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struct module *m = mod->mod;
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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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enable);
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mod = mod->next;
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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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arch_jump_label_transform_static(iter, JUMP_LABEL_DISABLE);
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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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/* 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 = (struct static_key *)(unsigned long)iter->key;
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if (iterk == key)
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continue;
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key = iterk;
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if (__module_address(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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if (jump_label_type(key) == JUMP_LABEL_ENABLE)
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__jump_label_update(key, iter, iter_stop, JUMP_LABEL_ENABLE);
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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 (iter->key == (jump_label_t)(unsigned long)key)
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continue;
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key = (struct static_key *)(unsigned long)iter->key;
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if (__module_address(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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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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}
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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,
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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);
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if (ret)
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jump_label_del_module(mod);
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jump_label_unlock();
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break;
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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();
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break;
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case MODULE_STATE_LIVE:
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jump_label_lock();
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jump_label_invalidate_module_init(mod);
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jump_label_unlock();
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break;
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}
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return notifier_from_errno(ret);
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}
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struct notifier_block jump_label_module_nb = {
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.notifier_call = jump_label_module_notify,
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.priority = 1, /* higher than tracepoints */
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};
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static __init int jump_label_init_module(void)
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{
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return register_module_notifier(&jump_label_module_nb);
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}
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early_initcall(jump_label_init_module);
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#endif /* CONFIG_MODULES */
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/***
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* jump_label_text_reserved - check if addr range is reserved
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* @start: start text addr
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* @end: end text addr
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*
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* checks if the text addr located between @start and @end
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* overlaps with any of the jump label patch addresses. Code
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* that wants to modify kernel text should first verify that
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* it does not overlap with any of the jump label addresses.
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* Caller must hold jump_label_mutex.
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*
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* returns 1 if there is an overlap, 0 otherwise
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*/
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int jump_label_text_reserved(void *start, void *end)
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{
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int ret = __jump_label_text_reserved(__start___jump_table,
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__stop___jump_table, start, end);
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if (ret)
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return ret;
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#ifdef CONFIG_MODULES
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ret = __jump_label_mod_text_reserved(start, end);
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#endif
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return ret;
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}
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static void jump_label_update(struct static_key *key, int enable)
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{
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struct jump_entry *stop = __stop___jump_table;
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struct jump_entry *entry = jump_label_get_entries(key);
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#ifdef CONFIG_MODULES
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struct module *mod = __module_address((unsigned long)key);
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__jump_label_mod_update(key, enable);
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if (mod)
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stop = mod->jump_entries + mod->num_jump_entries;
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#endif
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/* if there are no users, entry can be NULL */
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if (entry)
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__jump_label_update(key, entry, stop, enable);
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}
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#endif
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