/* * jump label support * * Copyright (C) 2009 Jason Baron <jbaron@redhat.com> * Copyright (C) 2011 Peter Zijlstra <pzijlstr@redhat.com> * */ #include <linux/memory.h> #include <linux/uaccess.h> #include <linux/module.h> #include <linux/list.h> #include <linux/slab.h> #include <linux/sort.h> #include <linux/err.h> #include <linux/static_key.h> #ifdef HAVE_JUMP_LABEL /* mutex to protect coming/going of the the jump_label table */ static DEFINE_MUTEX(jump_label_mutex); void jump_label_lock(void) { mutex_lock(&jump_label_mutex); } void jump_label_unlock(void) { mutex_unlock(&jump_label_mutex); } static int jump_label_cmp(const void *a, const void *b) { const struct jump_entry *jea = a; const struct jump_entry *jeb = b; if (jea->key < jeb->key) return -1; if (jea->key > jeb->key) return 1; return 0; } static void jump_label_sort_entries(struct jump_entry *start, struct jump_entry *stop) { unsigned long size; size = (((unsigned long)stop - (unsigned long)start) / sizeof(struct jump_entry)); sort(start, size, sizeof(struct jump_entry), jump_label_cmp, NULL); } static void jump_label_update(struct static_key *key, int enable); void static_key_slow_inc(struct static_key *key) { if (atomic_inc_not_zero(&key->enabled)) return; jump_label_lock(); if (atomic_read(&key->enabled) == 0) { if (!jump_label_get_branch_default(key)) jump_label_update(key, JUMP_LABEL_ENABLE); else jump_label_update(key, JUMP_LABEL_DISABLE); } atomic_inc(&key->enabled); jump_label_unlock(); } EXPORT_SYMBOL_GPL(static_key_slow_inc); static void __static_key_slow_dec(struct static_key *key, unsigned long rate_limit, struct delayed_work *work) { if (!atomic_dec_and_mutex_lock(&key->enabled, &jump_label_mutex)) { WARN(atomic_read(&key->enabled) < 0, "jump label: negative count!\n"); return; } if (rate_limit) { atomic_inc(&key->enabled); schedule_delayed_work(work, rate_limit); } else { if (!jump_label_get_branch_default(key)) jump_label_update(key, JUMP_LABEL_DISABLE); else jump_label_update(key, JUMP_LABEL_ENABLE); } jump_label_unlock(); } static void jump_label_update_timeout(struct work_struct *work) { struct static_key_deferred *key = container_of(work, struct static_key_deferred, work.work); __static_key_slow_dec(&key->key, 0, NULL); } void static_key_slow_dec(struct static_key *key) { __static_key_slow_dec(key, 0, NULL); } EXPORT_SYMBOL_GPL(static_key_slow_dec); void static_key_slow_dec_deferred(struct static_key_deferred *key) { __static_key_slow_dec(&key->key, key->timeout, &key->work); } EXPORT_SYMBOL_GPL(static_key_slow_dec_deferred); void jump_label_rate_limit(struct static_key_deferred *key, unsigned long rl) { key->timeout = rl; INIT_DELAYED_WORK(&key->work, jump_label_update_timeout); } EXPORT_SYMBOL_GPL(jump_label_rate_limit); static int addr_conflict(struct jump_entry *entry, void *start, void *end) { if (entry->code <= (unsigned long)end && entry->code + JUMP_LABEL_NOP_SIZE > (unsigned long)start) return 1; return 0; } static int __jump_label_text_reserved(struct jump_entry *iter_start, struct jump_entry *iter_stop, void *start, void *end) { struct jump_entry *iter; iter = iter_start; while (iter < iter_stop) { if (addr_conflict(iter, start, end)) return 1; iter++; } return 0; } /* * Update code which is definitely not currently executing. * Architectures which need heavyweight synchronization to modify * running code can override this to make the non-live update case * cheaper. */ void __weak __init_or_module arch_jump_label_transform_static(struct jump_entry *entry, enum jump_label_type type) { arch_jump_label_transform(entry, type); } static void __jump_label_update(struct static_key *key, struct jump_entry *entry, struct jump_entry *stop, int enable) { for (; (entry < stop) && (entry->key == (jump_label_t)(unsigned long)key); entry++) { /* * entry->code set to 0 invalidates module init text sections * kernel_text_address() verifies we are not in core kernel * init code, see jump_label_invalidate_module_init(). */ if (entry->code && kernel_text_address(entry->code)) arch_jump_label_transform(entry, enable); } } static enum jump_label_type jump_label_type(struct static_key *key) { bool true_branch = jump_label_get_branch_default(key); bool state = static_key_enabled(key); if ((!true_branch && state) || (true_branch && !state)) return JUMP_LABEL_ENABLE; return JUMP_LABEL_DISABLE; } void __init jump_label_init(void) { struct jump_entry *iter_start = __start___jump_table; struct jump_entry *iter_stop = __stop___jump_table; struct static_key *key = NULL; struct jump_entry *iter; jump_label_lock(); jump_label_sort_entries(iter_start, iter_stop); for (iter = iter_start; iter < iter_stop; iter++) { struct static_key *iterk; iterk = (struct static_key *)(unsigned long)iter->key; arch_jump_label_transform_static(iter, jump_label_type(iterk)); if (iterk == key) continue; key = iterk; /* * Set key->entries to iter, but preserve JUMP_LABEL_TRUE_BRANCH. */ *((unsigned long *)&key->entries) += (unsigned long)iter; #ifdef CONFIG_MODULES key->next = NULL; #endif } jump_label_unlock(); } #ifdef CONFIG_MODULES struct static_key_mod { struct static_key_mod *next; struct jump_entry *entries; struct module *mod; }; static int __jump_label_mod_text_reserved(void *start, void *end) { struct module *mod; mod = __module_text_address((unsigned long)start); if (!mod) return 0; WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod); return __jump_label_text_reserved(mod->jump_entries, mod->jump_entries + mod->num_jump_entries, start, end); } static void __jump_label_mod_update(struct static_key *key, int enable) { struct static_key_mod *mod = key->next; while (mod) { struct module *m = mod->mod; __jump_label_update(key, mod->entries, m->jump_entries + m->num_jump_entries, enable); mod = mod->next; } } /*** * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop() * @mod: module to patch * * Allow for run-time selection of the optimal nops. Before the module * loads patch these with arch_get_jump_label_nop(), which is specified by * the arch specific jump label code. */ void jump_label_apply_nops(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; /* if the module doesn't have jump label entries, just return */ if (iter_start == iter_stop) return; for (iter = iter_start; iter < iter_stop; iter++) { arch_jump_label_transform_static(iter, JUMP_LABEL_DISABLE); } } static int jump_label_add_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; /* if the module doesn't have jump label entries, just return */ if (iter_start == iter_stop) return 0; jump_label_sort_entries(iter_start, iter_stop); for (iter = iter_start; iter < iter_stop; iter++) { struct static_key *iterk; iterk = (struct static_key *)(unsigned long)iter->key; if (iterk == key) continue; key = iterk; if (__module_address(iter->key) == mod) { /* * Set key->entries to iter, but preserve JUMP_LABEL_TRUE_BRANCH. */ *((unsigned long *)&key->entries) += (unsigned long)iter; key->next = NULL; continue; } jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL); if (!jlm) return -ENOMEM; jlm->mod = mod; jlm->entries = iter; jlm->next = key->next; key->next = jlm; if (jump_label_type(key) == JUMP_LABEL_ENABLE) __jump_label_update(key, iter, iter_stop, JUMP_LABEL_ENABLE); } 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 (iter->key == (jump_label_t)(unsigned long)key) continue; key = (struct static_key *)(unsigned long)iter->key; if (__module_address(iter->key) == mod) continue; prev = &key->next; jlm = key->next; while (jlm && jlm->mod != mod) { prev = &jlm->next; jlm = jlm->next; } if (jlm) { *prev = jlm->next; 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; switch (val) { case MODULE_STATE_COMING: jump_label_lock(); ret = jump_label_add_module(mod); if (ret) jump_label_del_module(mod); jump_label_unlock(); break; case MODULE_STATE_GOING: jump_label_lock(); jump_label_del_module(mod); jump_label_unlock(); break; case MODULE_STATE_LIVE: jump_label_lock(); jump_label_invalidate_module_init(mod); jump_label_unlock(); break; } return notifier_from_errno(ret); } 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, int enable) { struct jump_entry *stop = __stop___jump_table; struct jump_entry *entry = jump_label_get_entries(key); #ifdef CONFIG_MODULES struct module *mod = __module_address((unsigned long)key); __jump_label_mod_update(key, enable); if (mod) stop = mod->jump_entries + mod->num_jump_entries; #endif /* if there are no users, entry can be NULL */ if (entry) __jump_label_update(key, entry, stop, enable); } #endif