/*
 * 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