4 * Copyright (C) 2009 Jason Baron <jbaron@redhat.com>
7 #include <linux/jump_label.h>
8 #include <linux/memory.h>
9 #include <linux/uaccess.h>
10 #include <linux/module.h>
11 #include <linux/list.h>
12 #include <linux/jhash.h>
13 #include <linux/slab.h>
14 #include <linux/sort.h>
15 #include <linux/err.h>
17 #ifdef HAVE_JUMP_LABEL
19 #define JUMP_LABEL_HASH_BITS 6
20 #define JUMP_LABEL_TABLE_SIZE (1 << JUMP_LABEL_HASH_BITS)
21 static struct hlist_head jump_label_table[JUMP_LABEL_TABLE_SIZE];
23 /* mutex to protect coming/going of the the jump_label table */
24 static DEFINE_MUTEX(jump_label_mutex);
26 struct jump_label_entry {
27 struct hlist_node hlist;
28 struct jump_entry *table;
30 /* hang modules off here */
31 struct hlist_head modules;
35 struct jump_label_module_entry {
36 struct hlist_node hlist;
37 struct jump_entry *table;
42 static int jump_label_cmp(const void *a, const void *b)
44 const struct jump_entry *jea = a;
45 const struct jump_entry *jeb = b;
47 if (jea->key < jeb->key)
50 if (jea->key > jeb->key)
57 sort_jump_label_entries(struct jump_entry *start, struct jump_entry *stop)
61 size = (((unsigned long)stop - (unsigned long)start)
62 / sizeof(struct jump_entry));
63 sort(start, size, sizeof(struct jump_entry), jump_label_cmp, NULL);
66 static struct jump_label_entry *get_jump_label_entry(jump_label_t key)
68 struct hlist_head *head;
69 struct hlist_node *node;
70 struct jump_label_entry *e;
71 u32 hash = jhash((void *)&key, sizeof(jump_label_t), 0);
73 head = &jump_label_table[hash & (JUMP_LABEL_TABLE_SIZE - 1)];
74 hlist_for_each_entry(e, node, head, hlist) {
81 static struct jump_label_entry *
82 add_jump_label_entry(jump_label_t key, int nr_entries, struct jump_entry *table)
84 struct hlist_head *head;
85 struct jump_label_entry *e;
88 e = get_jump_label_entry(key);
90 return ERR_PTR(-EEXIST);
92 e = kmalloc(sizeof(struct jump_label_entry), GFP_KERNEL);
94 return ERR_PTR(-ENOMEM);
96 hash = jhash((void *)&key, sizeof(jump_label_t), 0);
97 head = &jump_label_table[hash & (JUMP_LABEL_TABLE_SIZE - 1)];
100 e->nr_entries = nr_entries;
101 INIT_HLIST_HEAD(&(e->modules));
102 hlist_add_head(&e->hlist, head);
107 build_jump_label_hashtable(struct jump_entry *start, struct jump_entry *stop)
109 struct jump_entry *iter, *iter_begin;
110 struct jump_label_entry *entry;
113 sort_jump_label_entries(start, stop);
115 while (iter < stop) {
116 entry = get_jump_label_entry(iter->key);
120 while ((iter < stop) &&
121 (iter->key == iter_begin->key)) {
125 entry = add_jump_label_entry(iter_begin->key,
128 return PTR_ERR(entry);
130 WARN_ONCE(1, KERN_ERR "build_jump_hashtable: unexpected entry!\n");
138 * jump_label_update - update jump label text
139 * @key - key value associated with a a jump label
140 * @type - enum set to JUMP_LABEL_ENABLE or JUMP_LABEL_DISABLE
142 * Will enable/disable the jump for jump label @key, depending on the
147 void jump_label_update(unsigned long key, enum jump_label_type type)
149 struct jump_entry *iter;
150 struct jump_label_entry *entry;
151 struct hlist_node *module_node;
152 struct jump_label_module_entry *e_module;
155 mutex_lock(&jump_label_mutex);
156 entry = get_jump_label_entry((jump_label_t)key);
158 count = entry->nr_entries;
161 if (kernel_text_address(iter->code))
162 arch_jump_label_transform(iter, type);
165 /* eanble/disable jump labels in modules */
166 hlist_for_each_entry(e_module, module_node, &(entry->modules),
168 count = e_module->nr_entries;
169 iter = e_module->table;
171 if (kernel_text_address(iter->code))
172 arch_jump_label_transform(iter, type);
177 mutex_unlock(&jump_label_mutex);
180 static int addr_conflict(struct jump_entry *entry, void *start, void *end)
182 if (entry->code <= (unsigned long)end &&
183 entry->code + JUMP_LABEL_NOP_SIZE > (unsigned long)start)
189 #ifdef CONFIG_MODULES
191 static int module_conflict(void *start, void *end)
193 struct hlist_head *head;
194 struct hlist_node *node, *node_next, *module_node, *module_node_next;
195 struct jump_label_entry *e;
196 struct jump_label_module_entry *e_module;
197 struct jump_entry *iter;
201 for (i = 0; i < JUMP_LABEL_TABLE_SIZE; i++) {
202 head = &jump_label_table[i];
203 hlist_for_each_entry_safe(e, node, node_next, head, hlist) {
204 hlist_for_each_entry_safe(e_module, module_node,
206 &(e->modules), hlist) {
207 count = e_module->nr_entries;
208 iter = e_module->table;
210 if (addr_conflict(iter, start, end)) {
226 * jump_label_text_reserved - check if addr range is reserved
227 * @start: start text addr
228 * @end: end text addr
230 * checks if the text addr located between @start and @end
231 * overlaps with any of the jump label patch addresses. Code
232 * that wants to modify kernel text should first verify that
233 * it does not overlap with any of the jump label addresses.
235 * returns 1 if there is an overlap, 0 otherwise
237 int jump_label_text_reserved(void *start, void *end)
239 struct jump_entry *iter;
240 struct jump_entry *iter_start = __start___jump_table;
241 struct jump_entry *iter_stop = __start___jump_table;
244 mutex_lock(&jump_label_mutex);
246 while (iter < iter_stop) {
247 if (addr_conflict(iter, start, end)) {
254 /* now check modules */
255 #ifdef CONFIG_MODULES
256 conflict = module_conflict(start, end);
259 mutex_unlock(&jump_label_mutex);
263 static __init int init_jump_label(void)
266 struct jump_entry *iter_start = __start___jump_table;
267 struct jump_entry *iter_stop = __stop___jump_table;
268 struct jump_entry *iter;
270 mutex_lock(&jump_label_mutex);
271 ret = build_jump_label_hashtable(__start___jump_table,
272 __stop___jump_table);
274 while (iter < iter_stop) {
275 arch_jump_label_text_poke_early(iter->code);
278 mutex_unlock(&jump_label_mutex);
281 early_initcall(init_jump_label);
283 #ifdef CONFIG_MODULES
285 static struct jump_label_module_entry *
286 add_jump_label_module_entry(struct jump_label_entry *entry,
287 struct jump_entry *iter_begin,
288 int count, struct module *mod)
290 struct jump_label_module_entry *e;
292 e = kmalloc(sizeof(struct jump_label_module_entry), GFP_KERNEL);
294 return ERR_PTR(-ENOMEM);
296 e->nr_entries = count;
297 e->table = iter_begin;
298 hlist_add_head(&e->hlist, &entry->modules);
302 static int add_jump_label_module(struct module *mod)
304 struct jump_entry *iter, *iter_begin;
305 struct jump_label_entry *entry;
306 struct jump_label_module_entry *module_entry;
309 /* if the module doesn't have jump label entries, just return */
310 if (!mod->num_jump_entries)
313 sort_jump_label_entries(mod->jump_entries,
314 mod->jump_entries + mod->num_jump_entries);
315 iter = mod->jump_entries;
316 while (iter < mod->jump_entries + mod->num_jump_entries) {
317 entry = get_jump_label_entry(iter->key);
320 while ((iter < mod->jump_entries + mod->num_jump_entries) &&
321 (iter->key == iter_begin->key)) {
326 entry = add_jump_label_entry(iter_begin->key, 0, NULL);
328 return PTR_ERR(entry);
330 module_entry = add_jump_label_module_entry(entry, iter_begin,
332 if (IS_ERR(module_entry))
333 return PTR_ERR(module_entry);
338 static void remove_jump_label_module(struct module *mod)
340 struct hlist_head *head;
341 struct hlist_node *node, *node_next, *module_node, *module_node_next;
342 struct jump_label_entry *e;
343 struct jump_label_module_entry *e_module;
346 /* if the module doesn't have jump label entries, just return */
347 if (!mod->num_jump_entries)
350 for (i = 0; i < JUMP_LABEL_TABLE_SIZE; i++) {
351 head = &jump_label_table[i];
352 hlist_for_each_entry_safe(e, node, node_next, head, hlist) {
353 hlist_for_each_entry_safe(e_module, module_node,
355 &(e->modules), hlist) {
356 if (e_module->mod == mod) {
357 hlist_del(&e_module->hlist);
361 if (hlist_empty(&e->modules) && (e->nr_entries == 0)) {
362 hlist_del(&e->hlist);
370 jump_label_module_notify(struct notifier_block *self, unsigned long val,
373 struct module *mod = data;
377 case MODULE_STATE_COMING:
378 mutex_lock(&jump_label_mutex);
379 ret = add_jump_label_module(mod);
381 remove_jump_label_module(mod);
382 mutex_unlock(&jump_label_mutex);
384 case MODULE_STATE_GOING:
385 mutex_lock(&jump_label_mutex);
386 remove_jump_label_module(mod);
387 mutex_unlock(&jump_label_mutex);
394 * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop()
395 * @mod: module to patch
397 * Allow for run-time selection of the optimal nops. Before the module
398 * loads patch these with arch_get_jump_label_nop(), which is specified by
399 * the arch specific jump label code.
401 void jump_label_apply_nops(struct module *mod)
403 struct jump_entry *iter;
405 /* if the module doesn't have jump label entries, just return */
406 if (!mod->num_jump_entries)
409 iter = mod->jump_entries;
410 while (iter < mod->jump_entries + mod->num_jump_entries) {
411 arch_jump_label_text_poke_early(iter->code);
416 struct notifier_block jump_label_module_nb = {
417 .notifier_call = jump_label_module_notify,
421 static __init int init_jump_label_module(void)
423 return register_module_notifier(&jump_label_module_nb);
425 early_initcall(init_jump_label_module);
427 #endif /* CONFIG_MODULES */