blob: 7be868bf25c69268e78c7eb7b50a7fb0d83dd1b4 [file] [log] [blame]
/*
* jump label support
*
* Copyright (C) 2009 Jason Baron <jbaron@redhat.com>
*
*/
#include <linux/jump_label.h>
#include <linux/memory.h>
#include <linux/uaccess.h>
#include <linux/module.h>
#include <linux/list.h>
#include <linux/jhash.h>
#include <linux/slab.h>
#include <linux/sort.h>
#include <linux/err.h>
#ifdef HAVE_JUMP_LABEL
#define JUMP_LABEL_HASH_BITS 6
#define JUMP_LABEL_TABLE_SIZE (1 << JUMP_LABEL_HASH_BITS)
static struct hlist_head jump_label_table[JUMP_LABEL_TABLE_SIZE];
/* mutex to protect coming/going of the the jump_label table */
static DEFINE_MUTEX(jump_label_mutex);
struct jump_label_entry {
struct hlist_node hlist;
struct jump_entry *table;
int nr_entries;
/* hang modules off here */
struct hlist_head modules;
unsigned long key;
};
struct jump_label_module_entry {
struct hlist_node hlist;
struct jump_entry *table;
int nr_entries;
struct module *mod;
};
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
sort_jump_label_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 struct jump_label_entry *get_jump_label_entry(jump_label_t key)
{
struct hlist_head *head;
struct hlist_node *node;
struct jump_label_entry *e;
u32 hash = jhash((void *)&key, sizeof(jump_label_t), 0);
head = &jump_label_table[hash & (JUMP_LABEL_TABLE_SIZE - 1)];
hlist_for_each_entry(e, node, head, hlist) {
if (key == e->key)
return e;
}
return NULL;
}
static struct jump_label_entry *
add_jump_label_entry(jump_label_t key, int nr_entries, struct jump_entry *table)
{
struct hlist_head *head;
struct jump_label_entry *e;
u32 hash;
e = get_jump_label_entry(key);
if (e)
return ERR_PTR(-EEXIST);
e = kmalloc(sizeof(struct jump_label_entry), GFP_KERNEL);
if (!e)
return ERR_PTR(-ENOMEM);
hash = jhash((void *)&key, sizeof(jump_label_t), 0);
head = &jump_label_table[hash & (JUMP_LABEL_TABLE_SIZE - 1)];
e->key = key;
e->table = table;
e->nr_entries = nr_entries;
INIT_HLIST_HEAD(&(e->modules));
hlist_add_head(&e->hlist, head);
return e;
}
static int
build_jump_label_hashtable(struct jump_entry *start, struct jump_entry *stop)
{
struct jump_entry *iter, *iter_begin;
struct jump_label_entry *entry;
int count;
sort_jump_label_entries(start, stop);
iter = start;
while (iter < stop) {
entry = get_jump_label_entry(iter->key);
if (!entry) {
iter_begin = iter;
count = 0;
while ((iter < stop) &&
(iter->key == iter_begin->key)) {
iter++;
count++;
}
entry = add_jump_label_entry(iter_begin->key,
count, iter_begin);
if (IS_ERR(entry))
return PTR_ERR(entry);
} else {
WARN_ONCE(1, KERN_ERR "build_jump_hashtable: unexpected entry!\n");
return -1;
}
}
return 0;
}
/***
* jump_label_update - update jump label text
* @key - key value associated with a a jump label
* @type - enum set to JUMP_LABEL_ENABLE or JUMP_LABEL_DISABLE
*
* Will enable/disable the jump for jump label @key, depending on the
* value of @type.
*
*/
void jump_label_update(unsigned long key, enum jump_label_type type)
{
struct jump_entry *iter;
struct jump_label_entry *entry;
struct hlist_node *module_node;
struct jump_label_module_entry *e_module;
int count;
mutex_lock(&jump_label_mutex);
entry = get_jump_label_entry((jump_label_t)key);
if (entry) {
count = entry->nr_entries;
iter = entry->table;
while (count--) {
if (kernel_text_address(iter->code))
arch_jump_label_transform(iter, type);
iter++;
}
/* eanble/disable jump labels in modules */
hlist_for_each_entry(e_module, module_node, &(entry->modules),
hlist) {
count = e_module->nr_entries;
iter = e_module->table;
while (count--) {
if (kernel_text_address(iter->code))
arch_jump_label_transform(iter, type);
iter++;
}
}
}
mutex_unlock(&jump_label_mutex);
}
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;
}
#ifdef CONFIG_MODULES
static int module_conflict(void *start, void *end)
{
struct hlist_head *head;
struct hlist_node *node, *node_next, *module_node, *module_node_next;
struct jump_label_entry *e;
struct jump_label_module_entry *e_module;
struct jump_entry *iter;
int i, count;
int conflict = 0;
for (i = 0; i < JUMP_LABEL_TABLE_SIZE; i++) {
head = &jump_label_table[i];
hlist_for_each_entry_safe(e, node, node_next, head, hlist) {
hlist_for_each_entry_safe(e_module, module_node,
module_node_next,
&(e->modules), hlist) {
count = e_module->nr_entries;
iter = e_module->table;
while (count--) {
if (addr_conflict(iter, start, end)) {
conflict = 1;
goto out;
}
iter++;
}
}
}
}
out:
return conflict;
}
#endif
/***
* 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.
*
* returns 1 if there is an overlap, 0 otherwise
*/
int jump_label_text_reserved(void *start, void *end)
{
struct jump_entry *iter;
struct jump_entry *iter_start = __start___jump_table;
struct jump_entry *iter_stop = __start___jump_table;
int conflict = 0;
mutex_lock(&jump_label_mutex);
iter = iter_start;
while (iter < iter_stop) {
if (addr_conflict(iter, start, end)) {
conflict = 1;
goto out;
}
iter++;
}
/* now check modules */
#ifdef CONFIG_MODULES
conflict = module_conflict(start, end);
#endif
out:
mutex_unlock(&jump_label_mutex);
return conflict;
}
static __init int init_jump_label(void)
{
int ret;
struct jump_entry *iter_start = __start___jump_table;
struct jump_entry *iter_stop = __stop___jump_table;
struct jump_entry *iter;
mutex_lock(&jump_label_mutex);
ret = build_jump_label_hashtable(__start___jump_table,
__stop___jump_table);
iter = iter_start;
while (iter < iter_stop) {
arch_jump_label_text_poke_early(iter->code);
iter++;
}
mutex_unlock(&jump_label_mutex);
return ret;
}
early_initcall(init_jump_label);
#ifdef CONFIG_MODULES
static struct jump_label_module_entry *
add_jump_label_module_entry(struct jump_label_entry *entry,
struct jump_entry *iter_begin,
int count, struct module *mod)
{
struct jump_label_module_entry *e;
e = kmalloc(sizeof(struct jump_label_module_entry), GFP_KERNEL);
if (!e)
return ERR_PTR(-ENOMEM);
e->mod = mod;
e->nr_entries = count;
e->table = iter_begin;
hlist_add_head(&e->hlist, &entry->modules);
return e;
}
static int add_jump_label_module(struct module *mod)
{
struct jump_entry *iter, *iter_begin;
struct jump_label_entry *entry;
struct jump_label_module_entry *module_entry;
int count;
/* if the module doesn't have jump label entries, just return */
if (!mod->num_jump_entries)
return 0;
sort_jump_label_entries(mod->jump_entries,
mod->jump_entries + mod->num_jump_entries);
iter = mod->jump_entries;
while (iter < mod->jump_entries + mod->num_jump_entries) {
entry = get_jump_label_entry(iter->key);
iter_begin = iter;
count = 0;
while ((iter < mod->jump_entries + mod->num_jump_entries) &&
(iter->key == iter_begin->key)) {
iter++;
count++;
}
if (!entry) {
entry = add_jump_label_entry(iter_begin->key, 0, NULL);
if (IS_ERR(entry))
return PTR_ERR(entry);
}
module_entry = add_jump_label_module_entry(entry, iter_begin,
count, mod);
if (IS_ERR(module_entry))
return PTR_ERR(module_entry);
}
return 0;
}
static void remove_jump_label_module(struct module *mod)
{
struct hlist_head *head;
struct hlist_node *node, *node_next, *module_node, *module_node_next;
struct jump_label_entry *e;
struct jump_label_module_entry *e_module;
int i;
/* if the module doesn't have jump label entries, just return */
if (!mod->num_jump_entries)
return;
for (i = 0; i < JUMP_LABEL_TABLE_SIZE; i++) {
head = &jump_label_table[i];
hlist_for_each_entry_safe(e, node, node_next, head, hlist) {
hlist_for_each_entry_safe(e_module, module_node,
module_node_next,
&(e->modules), hlist) {
if (e_module->mod == mod) {
hlist_del(&e_module->hlist);
kfree(e_module);
}
}
if (hlist_empty(&e->modules) && (e->nr_entries == 0)) {
hlist_del(&e->hlist);
kfree(e);
}
}
}
}
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:
mutex_lock(&jump_label_mutex);
ret = add_jump_label_module(mod);
if (ret)
remove_jump_label_module(mod);
mutex_unlock(&jump_label_mutex);
break;
case MODULE_STATE_GOING:
mutex_lock(&jump_label_mutex);
remove_jump_label_module(mod);
mutex_unlock(&jump_label_mutex);
break;
}
return ret;
}
/***
* 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;
/* if the module doesn't have jump label entries, just return */
if (!mod->num_jump_entries)
return;
iter = mod->jump_entries;
while (iter < mod->jump_entries + mod->num_jump_entries) {
arch_jump_label_text_poke_early(iter->code);
iter++;
}
}
struct notifier_block jump_label_module_nb = {
.notifier_call = jump_label_module_notify,
.priority = 0,
};
static __init int init_jump_label_module(void)
{
return register_module_notifier(&jump_label_module_nb);
}
early_initcall(init_jump_label_module);
#endif /* CONFIG_MODULES */
#endif