Root/kernel/tracepoint.c

1/*
2 * Copyright (C) 2008 Mathieu Desnoyers
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
17 */
18#include <linux/module.h>
19#include <linux/mutex.h>
20#include <linux/types.h>
21#include <linux/jhash.h>
22#include <linux/list.h>
23#include <linux/rcupdate.h>
24#include <linux/tracepoint.h>
25#include <linux/err.h>
26#include <linux/slab.h>
27#include <linux/sched.h>
28#include <linux/jump_label.h>
29
30extern struct tracepoint * const __start___tracepoints_ptrs[];
31extern struct tracepoint * const __stop___tracepoints_ptrs[];
32
33/* Set to 1 to enable tracepoint debug output */
34static const int tracepoint_debug;
35
36/*
37 * tracepoints_mutex nests inside module_mutex. Tracepoints mutex protects the
38 * builtin and module tracepoints and the hash table.
39 */
40static DEFINE_MUTEX(tracepoints_mutex);
41
42/*
43 * Tracepoint hash table, containing the active tracepoints.
44 * Protected by tracepoints_mutex.
45 */
46#define TRACEPOINT_HASH_BITS 6
47#define TRACEPOINT_TABLE_SIZE (1 << TRACEPOINT_HASH_BITS)
48static struct hlist_head tracepoint_table[TRACEPOINT_TABLE_SIZE];
49
50/*
51 * Note about RCU :
52 * It is used to delay the free of multiple probes array until a quiescent
53 * state is reached.
54 * Tracepoint entries modifications are protected by the tracepoints_mutex.
55 */
56struct tracepoint_entry {
57    struct hlist_node hlist;
58    struct tracepoint_func *funcs;
59    int refcount; /* Number of times armed. 0 if disarmed. */
60    char name[0];
61};
62
63struct tp_probes {
64    union {
65        struct rcu_head rcu;
66        struct list_head list;
67    } u;
68    struct tracepoint_func probes[0];
69};
70
71static inline void *allocate_probes(int count)
72{
73    struct tp_probes *p = kmalloc(count * sizeof(struct tracepoint_func)
74            + sizeof(struct tp_probes), GFP_KERNEL);
75    return p == NULL ? NULL : p->probes;
76}
77
78static void rcu_free_old_probes(struct rcu_head *head)
79{
80    kfree(container_of(head, struct tp_probes, u.rcu));
81}
82
83static inline void release_probes(struct tracepoint_func *old)
84{
85    if (old) {
86        struct tp_probes *tp_probes = container_of(old,
87            struct tp_probes, probes[0]);
88        call_rcu_sched(&tp_probes->u.rcu, rcu_free_old_probes);
89    }
90}
91
92static void debug_print_probes(struct tracepoint_entry *entry)
93{
94    int i;
95
96    if (!tracepoint_debug || !entry->funcs)
97        return;
98
99    for (i = 0; entry->funcs[i].func; i++)
100        printk(KERN_DEBUG "Probe %d : %p\n", i, entry->funcs[i].func);
101}
102
103static struct tracepoint_func *
104tracepoint_entry_add_probe(struct tracepoint_entry *entry,
105               void *probe, void *data)
106{
107    int nr_probes = 0;
108    struct tracepoint_func *old, *new;
109
110    WARN_ON(!probe);
111
112    debug_print_probes(entry);
113    old = entry->funcs;
114    if (old) {
115        /* (N -> N+1), (N != 0, 1) probes */
116        for (nr_probes = 0; old[nr_probes].func; nr_probes++)
117            if (old[nr_probes].func == probe &&
118                old[nr_probes].data == data)
119                return ERR_PTR(-EEXIST);
120    }
121    /* + 2 : one for new probe, one for NULL func */
122    new = allocate_probes(nr_probes + 2);
123    if (new == NULL)
124        return ERR_PTR(-ENOMEM);
125    if (old)
126        memcpy(new, old, nr_probes * sizeof(struct tracepoint_func));
127    new[nr_probes].func = probe;
128    new[nr_probes].data = data;
129    new[nr_probes + 1].func = NULL;
130    entry->refcount = nr_probes + 1;
131    entry->funcs = new;
132    debug_print_probes(entry);
133    return old;
134}
135
136static void *
137tracepoint_entry_remove_probe(struct tracepoint_entry *entry,
138                  void *probe, void *data)
139{
140    int nr_probes = 0, nr_del = 0, i;
141    struct tracepoint_func *old, *new;
142
143    old = entry->funcs;
144
145    if (!old)
146        return ERR_PTR(-ENOENT);
147
148    debug_print_probes(entry);
149    /* (N -> M), (N > 1, M >= 0) probes */
150    for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
151        if (!probe ||
152            (old[nr_probes].func == probe &&
153             old[nr_probes].data == data))
154            nr_del++;
155    }
156
157    if (nr_probes - nr_del == 0) {
158        /* N -> 0, (N > 1) */
159        entry->funcs = NULL;
160        entry->refcount = 0;
161        debug_print_probes(entry);
162        return old;
163    } else {
164        int j = 0;
165        /* N -> M, (N > 1, M > 0) */
166        /* + 1 for NULL */
167        new = allocate_probes(nr_probes - nr_del + 1);
168        if (new == NULL)
169            return ERR_PTR(-ENOMEM);
170        for (i = 0; old[i].func; i++)
171            if (probe &&
172                (old[i].func != probe || old[i].data != data))
173                new[j++] = old[i];
174        new[nr_probes - nr_del].func = NULL;
175        entry->refcount = nr_probes - nr_del;
176        entry->funcs = new;
177    }
178    debug_print_probes(entry);
179    return old;
180}
181
182/*
183 * Get tracepoint if the tracepoint is present in the tracepoint hash table.
184 * Must be called with tracepoints_mutex held.
185 * Returns NULL if not present.
186 */
187static struct tracepoint_entry *get_tracepoint(const char *name)
188{
189    struct hlist_head *head;
190    struct hlist_node *node;
191    struct tracepoint_entry *e;
192    u32 hash = jhash(name, strlen(name), 0);
193
194    head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
195    hlist_for_each_entry(e, node, head, hlist) {
196        if (!strcmp(name, e->name))
197            return e;
198    }
199    return NULL;
200}
201
202/*
203 * Add the tracepoint to the tracepoint hash table. Must be called with
204 * tracepoints_mutex held.
205 */
206static struct tracepoint_entry *add_tracepoint(const char *name)
207{
208    struct hlist_head *head;
209    struct hlist_node *node;
210    struct tracepoint_entry *e;
211    size_t name_len = strlen(name) + 1;
212    u32 hash = jhash(name, name_len-1, 0);
213
214    head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
215    hlist_for_each_entry(e, node, head, hlist) {
216        if (!strcmp(name, e->name)) {
217            printk(KERN_NOTICE
218                "tracepoint %s busy\n", name);
219            return ERR_PTR(-EEXIST); /* Already there */
220        }
221    }
222    /*
223     * Using kmalloc here to allocate a variable length element. Could
224     * cause some memory fragmentation if overused.
225     */
226    e = kmalloc(sizeof(struct tracepoint_entry) + name_len, GFP_KERNEL);
227    if (!e)
228        return ERR_PTR(-ENOMEM);
229    memcpy(&e->name[0], name, name_len);
230    e->funcs = NULL;
231    e->refcount = 0;
232    hlist_add_head(&e->hlist, head);
233    return e;
234}
235
236/*
237 * Remove the tracepoint from the tracepoint hash table. Must be called with
238 * mutex_lock held.
239 */
240static inline void remove_tracepoint(struct tracepoint_entry *e)
241{
242    hlist_del(&e->hlist);
243    kfree(e);
244}
245
246/*
247 * Sets the probe callback corresponding to one tracepoint.
248 */
249static void set_tracepoint(struct tracepoint_entry **entry,
250    struct tracepoint *elem, int active)
251{
252    WARN_ON(strcmp((*entry)->name, elem->name) != 0);
253
254    if (elem->regfunc && !elem->state && active)
255        elem->regfunc();
256    else if (elem->unregfunc && elem->state && !active)
257        elem->unregfunc();
258
259    /*
260     * rcu_assign_pointer has a smp_wmb() which makes sure that the new
261     * probe callbacks array is consistent before setting a pointer to it.
262     * This array is referenced by __DO_TRACE from
263     * include/linux/tracepoints.h. A matching smp_read_barrier_depends()
264     * is used.
265     */
266    rcu_assign_pointer(elem->funcs, (*entry)->funcs);
267    if (!elem->state && active) {
268        jump_label_enable(&elem->state);
269        elem->state = active;
270    } else if (elem->state && !active) {
271        jump_label_disable(&elem->state);
272        elem->state = active;
273    }
274}
275
276/*
277 * Disable a tracepoint and its probe callback.
278 * Note: only waiting an RCU period after setting elem->call to the empty
279 * function insures that the original callback is not used anymore. This insured
280 * by preempt_disable around the call site.
281 */
282static void disable_tracepoint(struct tracepoint *elem)
283{
284    if (elem->unregfunc && elem->state)
285        elem->unregfunc();
286
287    if (elem->state) {
288        jump_label_disable(&elem->state);
289        elem->state = 0;
290    }
291    rcu_assign_pointer(elem->funcs, NULL);
292}
293
294/**
295 * tracepoint_update_probe_range - Update a probe range
296 * @begin: beginning of the range
297 * @end: end of the range
298 *
299 * Updates the probe callback corresponding to a range of tracepoints.
300 */
301void tracepoint_update_probe_range(struct tracepoint * const *begin,
302                   struct tracepoint * const *end)
303{
304    struct tracepoint * const *iter;
305    struct tracepoint_entry *mark_entry;
306
307    if (!begin)
308        return;
309
310    mutex_lock(&tracepoints_mutex);
311    for (iter = begin; iter < end; iter++) {
312        mark_entry = get_tracepoint((*iter)->name);
313        if (mark_entry) {
314            set_tracepoint(&mark_entry, *iter,
315                    !!mark_entry->refcount);
316        } else {
317            disable_tracepoint(*iter);
318        }
319    }
320    mutex_unlock(&tracepoints_mutex);
321}
322
323/*
324 * Update probes, removing the faulty probes.
325 */
326static void tracepoint_update_probes(void)
327{
328    /* Core kernel tracepoints */
329    tracepoint_update_probe_range(__start___tracepoints_ptrs,
330        __stop___tracepoints_ptrs);
331    /* tracepoints in modules. */
332    module_update_tracepoints();
333}
334
335static struct tracepoint_func *
336tracepoint_add_probe(const char *name, void *probe, void *data)
337{
338    struct tracepoint_entry *entry;
339    struct tracepoint_func *old;
340
341    entry = get_tracepoint(name);
342    if (!entry) {
343        entry = add_tracepoint(name);
344        if (IS_ERR(entry))
345            return (struct tracepoint_func *)entry;
346    }
347    old = tracepoint_entry_add_probe(entry, probe, data);
348    if (IS_ERR(old) && !entry->refcount)
349        remove_tracepoint(entry);
350    return old;
351}
352
353/**
354 * tracepoint_probe_register - Connect a probe to a tracepoint
355 * @name: tracepoint name
356 * @probe: probe handler
357 *
358 * Returns 0 if ok, error value on error.
359 * The probe address must at least be aligned on the architecture pointer size.
360 */
361int tracepoint_probe_register(const char *name, void *probe, void *data)
362{
363    struct tracepoint_func *old;
364
365    mutex_lock(&tracepoints_mutex);
366    old = tracepoint_add_probe(name, probe, data);
367    mutex_unlock(&tracepoints_mutex);
368    if (IS_ERR(old))
369        return PTR_ERR(old);
370
371    tracepoint_update_probes(); /* may update entry */
372    release_probes(old);
373    return 0;
374}
375EXPORT_SYMBOL_GPL(tracepoint_probe_register);
376
377static struct tracepoint_func *
378tracepoint_remove_probe(const char *name, void *probe, void *data)
379{
380    struct tracepoint_entry *entry;
381    struct tracepoint_func *old;
382
383    entry = get_tracepoint(name);
384    if (!entry)
385        return ERR_PTR(-ENOENT);
386    old = tracepoint_entry_remove_probe(entry, probe, data);
387    if (IS_ERR(old))
388        return old;
389    if (!entry->refcount)
390        remove_tracepoint(entry);
391    return old;
392}
393
394/**
395 * tracepoint_probe_unregister - Disconnect a probe from a tracepoint
396 * @name: tracepoint name
397 * @probe: probe function pointer
398 *
399 * We do not need to call a synchronize_sched to make sure the probes have
400 * finished running before doing a module unload, because the module unload
401 * itself uses stop_machine(), which insures that every preempt disabled section
402 * have finished.
403 */
404int tracepoint_probe_unregister(const char *name, void *probe, void *data)
405{
406    struct tracepoint_func *old;
407
408    mutex_lock(&tracepoints_mutex);
409    old = tracepoint_remove_probe(name, probe, data);
410    mutex_unlock(&tracepoints_mutex);
411    if (IS_ERR(old))
412        return PTR_ERR(old);
413
414    tracepoint_update_probes(); /* may update entry */
415    release_probes(old);
416    return 0;
417}
418EXPORT_SYMBOL_GPL(tracepoint_probe_unregister);
419
420static LIST_HEAD(old_probes);
421static int need_update;
422
423static void tracepoint_add_old_probes(void *old)
424{
425    need_update = 1;
426    if (old) {
427        struct tp_probes *tp_probes = container_of(old,
428            struct tp_probes, probes[0]);
429        list_add(&tp_probes->u.list, &old_probes);
430    }
431}
432
433/**
434 * tracepoint_probe_register_noupdate - register a probe but not connect
435 * @name: tracepoint name
436 * @probe: probe handler
437 *
438 * caller must call tracepoint_probe_update_all()
439 */
440int tracepoint_probe_register_noupdate(const char *name, void *probe,
441                       void *data)
442{
443    struct tracepoint_func *old;
444
445    mutex_lock(&tracepoints_mutex);
446    old = tracepoint_add_probe(name, probe, data);
447    if (IS_ERR(old)) {
448        mutex_unlock(&tracepoints_mutex);
449        return PTR_ERR(old);
450    }
451    tracepoint_add_old_probes(old);
452    mutex_unlock(&tracepoints_mutex);
453    return 0;
454}
455EXPORT_SYMBOL_GPL(tracepoint_probe_register_noupdate);
456
457/**
458 * tracepoint_probe_unregister_noupdate - remove a probe but not disconnect
459 * @name: tracepoint name
460 * @probe: probe function pointer
461 *
462 * caller must call tracepoint_probe_update_all()
463 */
464int tracepoint_probe_unregister_noupdate(const char *name, void *probe,
465                     void *data)
466{
467    struct tracepoint_func *old;
468
469    mutex_lock(&tracepoints_mutex);
470    old = tracepoint_remove_probe(name, probe, data);
471    if (IS_ERR(old)) {
472        mutex_unlock(&tracepoints_mutex);
473        return PTR_ERR(old);
474    }
475    tracepoint_add_old_probes(old);
476    mutex_unlock(&tracepoints_mutex);
477    return 0;
478}
479EXPORT_SYMBOL_GPL(tracepoint_probe_unregister_noupdate);
480
481/**
482 * tracepoint_probe_update_all - update tracepoints
483 */
484void tracepoint_probe_update_all(void)
485{
486    LIST_HEAD(release_probes);
487    struct tp_probes *pos, *next;
488
489    mutex_lock(&tracepoints_mutex);
490    if (!need_update) {
491        mutex_unlock(&tracepoints_mutex);
492        return;
493    }
494    if (!list_empty(&old_probes))
495        list_replace_init(&old_probes, &release_probes);
496    need_update = 0;
497    mutex_unlock(&tracepoints_mutex);
498
499    tracepoint_update_probes();
500    list_for_each_entry_safe(pos, next, &release_probes, u.list) {
501        list_del(&pos->u.list);
502        call_rcu_sched(&pos->u.rcu, rcu_free_old_probes);
503    }
504}
505EXPORT_SYMBOL_GPL(tracepoint_probe_update_all);
506
507/**
508 * tracepoint_get_iter_range - Get a next tracepoint iterator given a range.
509 * @tracepoint: current tracepoints (in), next tracepoint (out)
510 * @begin: beginning of the range
511 * @end: end of the range
512 *
513 * Returns whether a next tracepoint has been found (1) or not (0).
514 * Will return the first tracepoint in the range if the input tracepoint is
515 * NULL.
516 */
517int tracepoint_get_iter_range(struct tracepoint * const **tracepoint,
518    struct tracepoint * const *begin, struct tracepoint * const *end)
519{
520    if (!*tracepoint && begin != end) {
521        *tracepoint = begin;
522        return 1;
523    }
524    if (*tracepoint >= begin && *tracepoint < end)
525        return 1;
526    return 0;
527}
528EXPORT_SYMBOL_GPL(tracepoint_get_iter_range);
529
530static void tracepoint_get_iter(struct tracepoint_iter *iter)
531{
532    int found = 0;
533
534    /* Core kernel tracepoints */
535    if (!iter->module) {
536        found = tracepoint_get_iter_range(&iter->tracepoint,
537                __start___tracepoints_ptrs,
538                __stop___tracepoints_ptrs);
539        if (found)
540            goto end;
541    }
542    /* tracepoints in modules. */
543    found = module_get_iter_tracepoints(iter);
544end:
545    if (!found)
546        tracepoint_iter_reset(iter);
547}
548
549void tracepoint_iter_start(struct tracepoint_iter *iter)
550{
551    tracepoint_get_iter(iter);
552}
553EXPORT_SYMBOL_GPL(tracepoint_iter_start);
554
555void tracepoint_iter_next(struct tracepoint_iter *iter)
556{
557    iter->tracepoint++;
558    /*
559     * iter->tracepoint may be invalid because we blindly incremented it.
560     * Make sure it is valid by marshalling on the tracepoints, getting the
561     * tracepoints from following modules if necessary.
562     */
563    tracepoint_get_iter(iter);
564}
565EXPORT_SYMBOL_GPL(tracepoint_iter_next);
566
567void tracepoint_iter_stop(struct tracepoint_iter *iter)
568{
569}
570EXPORT_SYMBOL_GPL(tracepoint_iter_stop);
571
572void tracepoint_iter_reset(struct tracepoint_iter *iter)
573{
574    iter->module = NULL;
575    iter->tracepoint = NULL;
576}
577EXPORT_SYMBOL_GPL(tracepoint_iter_reset);
578
579#ifdef CONFIG_MODULES
580
581int tracepoint_module_notify(struct notifier_block *self,
582                 unsigned long val, void *data)
583{
584    struct module *mod = data;
585
586    switch (val) {
587    case MODULE_STATE_COMING:
588    case MODULE_STATE_GOING:
589        tracepoint_update_probe_range(mod->tracepoints_ptrs,
590            mod->tracepoints_ptrs + mod->num_tracepoints);
591        break;
592    }
593    return 0;
594}
595
596struct notifier_block tracepoint_module_nb = {
597    .notifier_call = tracepoint_module_notify,
598    .priority = 0,
599};
600
601static int init_tracepoints(void)
602{
603    return register_module_notifier(&tracepoint_module_nb);
604}
605__initcall(init_tracepoints);
606
607#endif /* CONFIG_MODULES */
608
609#ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
610
611/* NB: reg/unreg are called while guarded with the tracepoints_mutex */
612static int sys_tracepoint_refcount;
613
614void syscall_regfunc(void)
615{
616    unsigned long flags;
617    struct task_struct *g, *t;
618
619    if (!sys_tracepoint_refcount) {
620        read_lock_irqsave(&tasklist_lock, flags);
621        do_each_thread(g, t) {
622            /* Skip kernel threads. */
623            if (t->mm)
624                set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
625        } while_each_thread(g, t);
626        read_unlock_irqrestore(&tasklist_lock, flags);
627    }
628    sys_tracepoint_refcount++;
629}
630
631void syscall_unregfunc(void)
632{
633    unsigned long flags;
634    struct task_struct *g, *t;
635
636    sys_tracepoint_refcount--;
637    if (!sys_tracepoint_refcount) {
638        read_lock_irqsave(&tasklist_lock, flags);
639        do_each_thread(g, t) {
640            clear_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
641        } while_each_thread(g, t);
642        read_unlock_irqrestore(&tasklist_lock, flags);
643    }
644}
645#endif
646

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jz-3.13
jz-3.15
jz-3.16
jz-3.18-dt
jz-3.2
jz-3.3
jz-3.4
jz-3.5
jz-3.6
jz-3.6-rc2-pwm
jz-3.9
jz-3.9-clk
jz-3.9-rc8
jz47xx
jz47xx-2.6.38
master

Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
v2.6.34-rc7
v3.9



interactive