| /* |
| * jump label support |
| * |
| * Copyright (C) 2009 Jason Baron <jbaron@redhat.com> |
| * Copyright (C) 2011 Peter Zijlstra |
| * |
| */ |
| #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> |
| #include <linux/jump_label_ratelimit.h> |
| #include <linux/bug.h> |
| #include <linux/cpu.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); |
| |
| /* |
| * There are similar definitions for the !HAVE_JUMP_LABEL case in jump_label.h. |
| * The use of 'atomic_read()' requires atomic.h and its problematic for some |
| * kernel headers such as kernel.h and others. Since static_key_count() is not |
| * used in the branch statements as it is for the !HAVE_JUMP_LABEL case its ok |
| * to have it be a function here. Similarly, for 'static_key_enable()' and |
| * 'static_key_disable()', which require bug.h. This should allow jump_label.h |
| * to be included from most/all places for HAVE_JUMP_LABEL. |
| */ |
| int static_key_count(struct static_key *key) |
| { |
| /* |
| * -1 means the first static_key_slow_inc() is in progress. |
| * static_key_enabled() must return true, so return 1 here. |
| */ |
| int n = atomic_read(&key->enabled); |
| |
| return n >= 0 ? n : 1; |
| } |
| EXPORT_SYMBOL_GPL(static_key_count); |
| |
| void static_key_enable(struct static_key *key) |
| { |
| int count = static_key_count(key); |
| |
| WARN_ON_ONCE(count < 0 || count > 1); |
| |
| if (!count) |
| static_key_slow_inc(key); |
| } |
| EXPORT_SYMBOL_GPL(static_key_enable); |
| |
| void static_key_disable(struct static_key *key) |
| { |
| int count = static_key_count(key); |
| |
| WARN_ON_ONCE(count < 0 || count > 1); |
| |
| if (count) |
| static_key_slow_dec(key); |
| } |
| EXPORT_SYMBOL_GPL(static_key_disable); |
| |
| void static_key_slow_inc(struct static_key *key) |
| { |
| int v, v1; |
| |
| STATIC_KEY_CHECK_USE(); |
| |
| /* |
| * Careful if we get concurrent static_key_slow_inc() calls; |
| * later calls must wait for the first one to _finish_ the |
| * jump_label_update() process. At the same time, however, |
| * the jump_label_update() call below wants to see |
| * static_key_enabled(&key) for jumps to be updated properly. |
| * |
| * So give a special meaning to negative key->enabled: it sends |
| * static_key_slow_inc() down the slow path, and it is non-zero |
| * so it counts as "enabled" in jump_label_update(). Note that |
| * atomic_inc_unless_negative() checks >= 0, so roll our own. |
| */ |
| for (v = atomic_read(&key->enabled); v > 0; v = v1) { |
| v1 = atomic_cmpxchg(&key->enabled, v, v + 1); |
| if (likely(v1 == v)) |
| return; |
| } |
| |
| cpus_read_lock(); |
| jump_label_lock(); |
| if (atomic_read(&key->enabled) == 0) { |
| atomic_set(&key->enabled, -1); |
| jump_label_update(key); |
| atomic_set(&key->enabled, 1); |
| } else { |
| atomic_inc(&key->enabled); |
| } |
| jump_label_unlock(); |
| cpus_read_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) |
| { |
| cpus_read_lock(); |
| /* |
| * The negative count check is valid even when a negative |
| * key->enabled is in use by static_key_slow_inc(); a |
| * __static_key_slow_dec() before the first static_key_slow_inc() |
| * returns is unbalanced, because all other static_key_slow_inc() |
| * instances block while the update is in progress. |
| */ |
| if (!atomic_dec_and_mutex_lock(&key->enabled, &jump_label_mutex)) { |
| WARN(atomic_read(&key->enabled) < 0, |
| "jump label: negative count!\n"); |
| cpus_read_unlock(); |
| return; |
| } |
| |
| if (rate_limit) { |
| atomic_inc(&key->enabled); |
| schedule_delayed_work(work, rate_limit); |
| } else { |
| jump_label_update(key); |
| } |
| jump_label_unlock(); |
| cpus_read_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_CHECK_USE(); |
| __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_CHECK_USE(); |
| __static_key_slow_dec(&key->key, key->timeout, &key->work); |
| } |
| EXPORT_SYMBOL_GPL(static_key_slow_dec_deferred); |
| |
| void static_key_deferred_flush(struct static_key_deferred *key) |
| { |
| STATIC_KEY_CHECK_USE(); |
| flush_delayed_work(&key->work); |
| } |
| EXPORT_SYMBOL_GPL(static_key_deferred_flush); |
| |
| void jump_label_rate_limit(struct static_key_deferred *key, |
| unsigned long rl) |
| { |
| STATIC_KEY_CHECK_USE(); |
| 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 inline struct jump_entry *static_key_entries(struct static_key *key) |
| { |
| WARN_ON_ONCE(key->type & JUMP_TYPE_LINKED); |
| return (struct jump_entry *)(key->type & ~JUMP_TYPE_MASK); |
| } |
| |
| static inline bool static_key_type(struct static_key *key) |
| { |
| return key->type & JUMP_TYPE_TRUE; |
| } |
| |
| static inline bool static_key_linked(struct static_key *key) |
| { |
| return key->type & JUMP_TYPE_LINKED; |
| } |
| |
| static inline void static_key_clear_linked(struct static_key *key) |
| { |
| key->type &= ~JUMP_TYPE_LINKED; |
| } |
| |
| static inline void static_key_set_linked(struct static_key *key) |
| { |
| key->type |= JUMP_TYPE_LINKED; |
| } |
| |
| static inline struct static_key *jump_entry_key(struct jump_entry *entry) |
| { |
| return (struct static_key *)((unsigned long)entry->key & ~1UL); |
| } |
| |
| static bool jump_entry_branch(struct jump_entry *entry) |
| { |
| return (unsigned long)entry->key & 1UL; |
| } |
| |
| /*** |
| * A 'struct static_key' uses a union such that it either points directly |
| * to a table of 'struct jump_entry' or to a linked list of modules which in |
| * turn point to 'struct jump_entry' tables. |
| * |
| * The two lower bits of the pointer are used to keep track of which pointer |
| * type is in use and to store the initial branch direction, we use an access |
| * function which preserves these bits. |
| */ |
| static void static_key_set_entries(struct static_key *key, |
| struct jump_entry *entries) |
| { |
| unsigned long type; |
| |
| WARN_ON_ONCE((unsigned long)entries & JUMP_TYPE_MASK); |
| type = key->type & JUMP_TYPE_MASK; |
| key->entries = entries; |
| key->type |= type; |
| } |
| |
| static enum jump_label_type jump_label_type(struct jump_entry *entry) |
| { |
| struct static_key *key = jump_entry_key(entry); |
| bool enabled = static_key_enabled(key); |
| bool branch = jump_entry_branch(entry); |
| |
| /* See the comment in linux/jump_label.h */ |
| return enabled ^ branch; |
| } |
| |
| static void __jump_label_update(struct static_key *key, |
| struct jump_entry *entry, |
| struct jump_entry *stop) |
| { |
| for (; (entry < stop) && (jump_entry_key(entry) == 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, jump_label_type(entry)); |
| } |
| } |
| |
| 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; |
| |
| /* |
| * Since we are initializing the static_key.enabled field with |
| * with the 'raw' int values (to avoid pulling in atomic.h) in |
| * jump_label.h, let's make sure that is safe. There are only two |
| * cases to check since we initialize to 0 or 1. |
| */ |
| BUILD_BUG_ON((int)ATOMIC_INIT(0) != 0); |
| BUILD_BUG_ON((int)ATOMIC_INIT(1) != 1); |
| |
| if (static_key_initialized) |
| return; |
| |
| cpus_read_lock(); |
| jump_label_lock(); |
| jump_label_sort_entries(iter_start, iter_stop); |
| |
| for (iter = iter_start; iter < iter_stop; iter++) { |
| struct static_key *iterk; |
| |
| /* rewrite NOPs */ |
| if (jump_label_type(iter) == JUMP_LABEL_NOP) |
| arch_jump_label_transform_static(iter, JUMP_LABEL_NOP); |
| |
| iterk = jump_entry_key(iter); |
| if (iterk == key) |
| continue; |
| |
| key = iterk; |
| static_key_set_entries(key, iter); |
| } |
| static_key_initialized = true; |
| jump_label_unlock(); |
| cpus_read_unlock(); |
| } |
| |
| #ifdef CONFIG_MODULES |
| |
| static enum jump_label_type jump_label_init_type(struct jump_entry *entry) |
| { |
| struct static_key *key = jump_entry_key(entry); |
| bool type = static_key_type(key); |
| bool branch = jump_entry_branch(entry); |
| |
| /* See the comment in linux/jump_label.h */ |
| return type ^ branch; |
| } |
| |
| struct static_key_mod { |
| struct static_key_mod *next; |
| struct jump_entry *entries; |
| struct module *mod; |
| }; |
| |
| static inline struct static_key_mod *static_key_mod(struct static_key *key) |
| { |
| WARN_ON_ONCE(!(key->type & JUMP_TYPE_LINKED)); |
| return (struct static_key_mod *)(key->type & ~JUMP_TYPE_MASK); |
| } |
| |
| /*** |
| * key->type and key->next are the same via union. |
| * This sets key->next and preserves the type bits. |
| * |
| * See additional comments above static_key_set_entries(). |
| */ |
| static void static_key_set_mod(struct static_key *key, |
| struct static_key_mod *mod) |
| { |
| unsigned long type; |
| |
| WARN_ON_ONCE((unsigned long)mod & JUMP_TYPE_MASK); |
| type = key->type & JUMP_TYPE_MASK; |
| key->next = mod; |
| key->type |= type; |
| } |
| |
| static int __jump_label_mod_text_reserved(void *start, void *end) |
| { |
| struct module *mod; |
| |
| preempt_disable(); |
| mod = __module_text_address((unsigned long)start); |
| WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod); |
| preempt_enable(); |
| |
| if (!mod) |
| return 0; |
| |
| |
| 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) |
| { |
| struct static_key_mod *mod; |
| |
| for (mod = static_key_mod(key); mod; mod = mod->next) { |
| struct jump_entry *stop; |
| struct module *m; |
| |
| /* |
| * NULL if the static_key is defined in a module |
| * that does not use it |
| */ |
| if (!mod->entries) |
| continue; |
| |
| m = mod->mod; |
| if (!m) |
| stop = __stop___jump_table; |
| else |
| stop = m->jump_entries + m->num_jump_entries; |
| __jump_label_update(key, mod->entries, stop); |
| } |
| } |
| |
| /*** |
| * 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++) { |
| /* Only write NOPs for arch_branch_static(). */ |
| if (jump_label_init_type(iter) == JUMP_LABEL_NOP) |
| arch_jump_label_transform_static(iter, JUMP_LABEL_NOP); |
| } |
| } |
| |
| 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, *jlm2; |
| |
| /* 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 = jump_entry_key(iter); |
| if (iterk == key) |
| continue; |
| |
| key = iterk; |
| if (within_module(iter->key, mod)) { |
| static_key_set_entries(key, iter); |
| continue; |
| } |
| 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 */ |