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/*
* 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);
}

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
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