tracing: Add tracepoints for hotplug
[linux-2.6.git] / kernel / jump_label.c
1 /*
2  * jump label support
3  *
4  * Copyright (C) 2009 Jason Baron <jbaron@redhat.com>
5  * Copyright (C) 2011 Peter Zijlstra <pzijlstr@redhat.com>
6  *
7  */
8 #include <linux/memory.h>
9 #include <linux/uaccess.h>
10 #include <linux/module.h>
11 #include <linux/list.h>
12 #include <linux/slab.h>
13 #include <linux/sort.h>
14 #include <linux/err.h>
15 #include <linux/jump_label.h>
16
17 #ifdef HAVE_JUMP_LABEL
18
19 /* mutex to protect coming/going of the the jump_label table */
20 static DEFINE_MUTEX(jump_label_mutex);
21
22 void jump_label_lock(void)
23 {
24         mutex_lock(&jump_label_mutex);
25 }
26
27 void jump_label_unlock(void)
28 {
29         mutex_unlock(&jump_label_mutex);
30 }
31
32 bool jump_label_enabled(struct jump_label_key *key)
33 {
34         return !!atomic_read(&key->enabled);
35 }
36
37 static int jump_label_cmp(const void *a, const void *b)
38 {
39         const struct jump_entry *jea = a;
40         const struct jump_entry *jeb = b;
41
42         if (jea->key < jeb->key)
43                 return -1;
44
45         if (jea->key > jeb->key)
46                 return 1;
47
48         return 0;
49 }
50
51 static void
52 jump_label_sort_entries(struct jump_entry *start, struct jump_entry *stop)
53 {
54         unsigned long size;
55
56         size = (((unsigned long)stop - (unsigned long)start)
57                                         / sizeof(struct jump_entry));
58         sort(start, size, sizeof(struct jump_entry), jump_label_cmp, NULL);
59 }
60
61 static void jump_label_update(struct jump_label_key *key, int enable);
62
63 void jump_label_inc(struct jump_label_key *key)
64 {
65         if (atomic_inc_not_zero(&key->enabled))
66                 return;
67
68         jump_label_lock();
69         if (atomic_read(&key->enabled) == 0)
70                 jump_label_update(key, JUMP_LABEL_ENABLE);
71         atomic_inc(&key->enabled);
72         jump_label_unlock();
73 }
74
75 void jump_label_dec(struct jump_label_key *key)
76 {
77         if (!atomic_dec_and_mutex_lock(&key->enabled, &jump_label_mutex))
78                 return;
79
80         jump_label_update(key, JUMP_LABEL_DISABLE);
81         jump_label_unlock();
82 }
83
84 static int addr_conflict(struct jump_entry *entry, void *start, void *end)
85 {
86         if (entry->code <= (unsigned long)end &&
87                 entry->code + JUMP_LABEL_NOP_SIZE > (unsigned long)start)
88                 return 1;
89
90         return 0;
91 }
92
93 static int __jump_label_text_reserved(struct jump_entry *iter_start,
94                 struct jump_entry *iter_stop, void *start, void *end)
95 {
96         struct jump_entry *iter;
97
98         iter = iter_start;
99         while (iter < iter_stop) {
100                 if (addr_conflict(iter, start, end))
101                         return 1;
102                 iter++;
103         }
104
105         return 0;
106 }
107
108 static void __jump_label_update(struct jump_label_key *key,
109                                 struct jump_entry *entry,
110                                 struct jump_entry *stop, int enable)
111 {
112         for (; (entry < stop) &&
113               (entry->key == (jump_label_t)(unsigned long)key);
114               entry++) {
115                 /*
116                  * entry->code set to 0 invalidates module init text sections
117                  * kernel_text_address() verifies we are not in core kernel
118                  * init code, see jump_label_invalidate_module_init().
119                  */
120                 if (entry->code && kernel_text_address(entry->code))
121                         arch_jump_label_transform(entry, enable);
122         }
123 }
124
125 /*
126  * Not all archs need this.
127  */
128 void __weak arch_jump_label_text_poke_early(jump_label_t addr)
129 {
130 }
131
132 static __init int jump_label_init(void)
133 {
134         struct jump_entry *iter_start = __start___jump_table;
135         struct jump_entry *iter_stop = __stop___jump_table;
136         struct jump_label_key *key = NULL;
137         struct jump_entry *iter;
138
139         jump_label_lock();
140         jump_label_sort_entries(iter_start, iter_stop);
141
142         for (iter = iter_start; iter < iter_stop; iter++) {
143                 arch_jump_label_text_poke_early(iter->code);
144                 if (iter->key == (jump_label_t)(unsigned long)key)
145                         continue;
146
147                 key = (struct jump_label_key *)(unsigned long)iter->key;
148                 atomic_set(&key->enabled, 0);
149                 key->entries = iter;
150 #ifdef CONFIG_MODULES
151                 key->next = NULL;
152 #endif
153         }
154         jump_label_unlock();
155
156         return 0;
157 }
158 early_initcall(jump_label_init);
159
160 #ifdef CONFIG_MODULES
161
162 struct jump_label_mod {
163         struct jump_label_mod *next;
164         struct jump_entry *entries;
165         struct module *mod;
166 };
167
168 static int __jump_label_mod_text_reserved(void *start, void *end)
169 {
170         struct module *mod;
171
172         mod = __module_text_address((unsigned long)start);
173         if (!mod)
174                 return 0;
175
176         WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
177
178         return __jump_label_text_reserved(mod->jump_entries,
179                                 mod->jump_entries + mod->num_jump_entries,
180                                 start, end);
181 }
182
183 static void __jump_label_mod_update(struct jump_label_key *key, int enable)
184 {
185         struct jump_label_mod *mod = key->next;
186
187         while (mod) {
188                 struct module *m = mod->mod;
189
190                 __jump_label_update(key, mod->entries,
191                                     m->jump_entries + m->num_jump_entries,
192                                     enable);
193                 mod = mod->next;
194         }
195 }
196
197 /***
198  * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop()
199  * @mod: module to patch
200  *
201  * Allow for run-time selection of the optimal nops. Before the module
202  * loads patch these with arch_get_jump_label_nop(), which is specified by
203  * the arch specific jump label code.
204  */
205 void jump_label_apply_nops(struct module *mod)
206 {
207         struct jump_entry *iter_start = mod->jump_entries;
208         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
209         struct jump_entry *iter;
210
211         /* if the module doesn't have jump label entries, just return */
212         if (iter_start == iter_stop)
213                 return;
214
215         for (iter = iter_start; iter < iter_stop; iter++)
216                 arch_jump_label_text_poke_early(iter->code);
217 }
218
219 static int jump_label_add_module(struct module *mod)
220 {
221         struct jump_entry *iter_start = mod->jump_entries;
222         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
223         struct jump_entry *iter;
224         struct jump_label_key *key = NULL;
225         struct jump_label_mod *jlm;
226
227         /* if the module doesn't have jump label entries, just return */
228         if (iter_start == iter_stop)
229                 return 0;
230
231         jump_label_sort_entries(iter_start, iter_stop);
232
233         for (iter = iter_start; iter < iter_stop; iter++) {
234                 if (iter->key == (jump_label_t)(unsigned long)key)
235                         continue;
236
237                 key = (struct jump_label_key *)(unsigned long)iter->key;
238
239                 if (__module_address(iter->key) == mod) {
240                         atomic_set(&key->enabled, 0);
241                         key->entries = iter;
242                         key->next = NULL;
243                         continue;
244                 }
245
246                 jlm = kzalloc(sizeof(struct jump_label_mod), GFP_KERNEL);
247                 if (!jlm)
248                         return -ENOMEM;
249
250                 jlm->mod = mod;
251                 jlm->entries = iter;
252                 jlm->next = key->next;
253                 key->next = jlm;
254
255                 if (jump_label_enabled(key))
256                         __jump_label_update(key, iter, iter_stop,
257                                             JUMP_LABEL_ENABLE);
258         }
259
260         return 0;
261 }
262
263 static void jump_label_del_module(struct module *mod)
264 {
265         struct jump_entry *iter_start = mod->jump_entries;
266         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
267         struct jump_entry *iter;
268         struct jump_label_key *key = NULL;
269         struct jump_label_mod *jlm, **prev;
270
271         for (iter = iter_start; iter < iter_stop; iter++) {
272                 if (iter->key == (jump_label_t)(unsigned long)key)
273                         continue;
274
275                 key = (struct jump_label_key *)(unsigned long)iter->key;
276
277                 if (__module_address(iter->key) == mod)
278                         continue;
279
280                 prev = &key->next;
281                 jlm = key->next;
282
283                 while (jlm && jlm->mod != mod) {
284                         prev = &jlm->next;
285                         jlm = jlm->next;
286                 }
287
288                 if (jlm) {
289                         *prev = jlm->next;
290                         kfree(jlm);
291                 }
292         }
293 }
294
295 static void jump_label_invalidate_module_init(struct module *mod)
296 {
297         struct jump_entry *iter_start = mod->jump_entries;
298         struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
299         struct jump_entry *iter;
300
301         for (iter = iter_start; iter < iter_stop; iter++) {
302                 if (within_module_init(iter->code, mod))
303                         iter->code = 0;
304         }
305 }
306
307 static int
308 jump_label_module_notify(struct notifier_block *self, unsigned long val,
309                          void *data)
310 {
311         struct module *mod = data;
312         int ret = 0;
313
314         switch (val) {
315         case MODULE_STATE_COMING:
316                 jump_label_lock();
317                 ret = jump_label_add_module(mod);
318                 if (ret)
319                         jump_label_del_module(mod);
320                 jump_label_unlock();
321                 break;
322         case MODULE_STATE_GOING:
323                 jump_label_lock();
324                 jump_label_del_module(mod);
325                 jump_label_unlock();
326                 break;
327         case MODULE_STATE_LIVE:
328                 jump_label_lock();
329                 jump_label_invalidate_module_init(mod);
330                 jump_label_unlock();
331                 break;
332         }
333
334         return notifier_from_errno(ret);
335 }
336
337 struct notifier_block jump_label_module_nb = {
338         .notifier_call = jump_label_module_notify,
339         .priority = 1, /* higher than tracepoints */
340 };
341
342 static __init int jump_label_init_module(void)
343 {
344         return register_module_notifier(&jump_label_module_nb);
345 }
346 early_initcall(jump_label_init_module);
347
348 #endif /* CONFIG_MODULES */
349
350 /***
351  * jump_label_text_reserved - check if addr range is reserved
352  * @start: start text addr
353  * @end: end text addr
354  *
355  * checks if the text addr located between @start and @end
356  * overlaps with any of the jump label patch addresses. Code
357  * that wants to modify kernel text should first verify that
358  * it does not overlap with any of the jump label addresses.
359  * Caller must hold jump_label_mutex.
360  *
361  * returns 1 if there is an overlap, 0 otherwise
362  */
363 int jump_label_text_reserved(void *start, void *end)
364 {
365         int ret = __jump_label_text_reserved(__start___jump_table,
366                         __stop___jump_table, start, end);
367
368         if (ret)
369                 return ret;
370
371 #ifdef CONFIG_MODULES
372         ret = __jump_label_mod_text_reserved(start, end);
373 #endif
374         return ret;
375 }
376
377 static void jump_label_update(struct jump_label_key *key, int enable)
378 {
379         struct jump_entry *entry = key->entries, *stop = __stop___jump_table;
380
381 #ifdef CONFIG_MODULES
382         struct module *mod = __module_address((jump_label_t)key);
383
384         __jump_label_mod_update(key, enable);
385
386         if (mod)
387                 stop = mod->jump_entries + mod->num_jump_entries;
388 #endif
389         /* if there are no users, entry can be NULL */
390         if (entry)
391                 __jump_label_update(key, entry, stop, enable);
392 }
393
394 #endif