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/static_key.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 protects the builtin and module tracepoints and the hash
38 * table, as well as the local module list.
39 */
40static DEFINE_MUTEX(tracepoints_mutex);
41
42#ifdef CONFIG_MODULES
43/* Local list of struct module */
44static LIST_HEAD(tracepoint_module_list);
45#endif /* CONFIG_MODULES */
46
47/*
48 * Tracepoint hash table, containing the active tracepoints.
49 * Protected by tracepoints_mutex.
50 */
51#define TRACEPOINT_HASH_BITS 6
52#define TRACEPOINT_TABLE_SIZE (1 << TRACEPOINT_HASH_BITS)
53static struct hlist_head tracepoint_table[TRACEPOINT_TABLE_SIZE];
54
55/*
56 * Note about RCU :
57 * It is used to delay the free of multiple probes array until a quiescent
58 * state is reached.
59 * Tracepoint entries modifications are protected by the tracepoints_mutex.
60 */
61struct tracepoint_entry {
62    struct hlist_node hlist;
63    struct tracepoint_func *funcs;
64    int refcount; /* Number of times armed. 0 if disarmed. */
65    char name[0];
66};
67
68struct tp_probes {
69    union {
70        struct rcu_head rcu;
71        struct list_head list;
72    } u;
73    struct tracepoint_func probes[0];
74};
75
76static inline void *allocate_probes(int count)
77{
78    struct tp_probes *p = kmalloc(count * sizeof(struct tracepoint_func)
79            + sizeof(struct tp_probes), GFP_KERNEL);
80    return p == NULL ? NULL : p->probes;
81}
82
83static void rcu_free_old_probes(struct rcu_head *head)
84{
85    kfree(container_of(head, struct tp_probes, u.rcu));
86}
87
88static inline void release_probes(struct tracepoint_func *old)
89{
90    if (old) {
91        struct tp_probes *tp_probes = container_of(old,
92            struct tp_probes, probes[0]);
93        call_rcu_sched(&tp_probes->u.rcu, rcu_free_old_probes);
94    }
95}
96
97static void debug_print_probes(struct tracepoint_entry *entry)
98{
99    int i;
100
101    if (!tracepoint_debug || !entry->funcs)
102        return;
103
104    for (i = 0; entry->funcs[i].func; i++)
105        printk(KERN_DEBUG "Probe %d : %p\n", i, entry->funcs[i].func);
106}
107
108static struct tracepoint_func *
109tracepoint_entry_add_probe(struct tracepoint_entry *entry,
110               void *probe, void *data)
111{
112    int nr_probes = 0;
113    struct tracepoint_func *old, *new;
114
115    WARN_ON(!probe);
116
117    debug_print_probes(entry);
118    old = entry->funcs;
119    if (old) {
120        /* (N -> N+1), (N != 0, 1) probes */
121        for (nr_probes = 0; old[nr_probes].func; nr_probes++)
122            if (old[nr_probes].func == probe &&
123                old[nr_probes].data == data)
124                return ERR_PTR(-EEXIST);
125    }
126    /* + 2 : one for new probe, one for NULL func */
127    new = allocate_probes(nr_probes + 2);
128    if (new == NULL)
129        return ERR_PTR(-ENOMEM);
130    if (old)
131        memcpy(new, old, nr_probes * sizeof(struct tracepoint_func));
132    new[nr_probes].func = probe;
133    new[nr_probes].data = data;
134    new[nr_probes + 1].func = NULL;
135    entry->refcount = nr_probes + 1;
136    entry->funcs = new;
137    debug_print_probes(entry);
138    return old;
139}
140
141static void *
142tracepoint_entry_remove_probe(struct tracepoint_entry *entry,
143                  void *probe, void *data)
144{
145    int nr_probes = 0, nr_del = 0, i;
146    struct tracepoint_func *old, *new;
147
148    old = entry->funcs;
149
150    if (!old)
151        return ERR_PTR(-ENOENT);
152
153    debug_print_probes(entry);
154    /* (N -> M), (N > 1, M >= 0) probes */
155    for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
156        if (!probe ||
157            (old[nr_probes].func == probe &&
158             old[nr_probes].data == data))
159            nr_del++;
160    }
161
162    if (nr_probes - nr_del == 0) {
163        /* N -> 0, (N > 1) */
164        entry->funcs = NULL;
165        entry->refcount = 0;
166        debug_print_probes(entry);
167        return old;
168    } else {
169        int j = 0;
170        /* N -> M, (N > 1, M > 0) */
171        /* + 1 for NULL */
172        new = allocate_probes(nr_probes - nr_del + 1);
173        if (new == NULL)
174            return ERR_PTR(-ENOMEM);
175        for (i = 0; old[i].func; i++)
176            if (probe &&
177                (old[i].func != probe || old[i].data != data))
178                new[j++] = old[i];
179        new[nr_probes - nr_del].func = NULL;
180        entry->refcount = nr_probes - nr_del;
181        entry->funcs = new;
182    }
183    debug_print_probes(entry);
184    return old;
185}
186
187/*
188 * Get tracepoint if the tracepoint is present in the tracepoint hash table.
189 * Must be called with tracepoints_mutex held.
190 * Returns NULL if not present.
191 */
192static struct tracepoint_entry *get_tracepoint(const char *name)
193{
194    struct hlist_head *head;
195    struct hlist_node *node;
196    struct tracepoint_entry *e;
197    u32 hash = jhash(name, strlen(name), 0);
198
199    head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
200    hlist_for_each_entry(e, node, head, hlist) {
201        if (!strcmp(name, e->name))
202            return e;
203    }
204    return NULL;
205}
206
207/*
208 * Add the tracepoint to the tracepoint hash table. Must be called with
209 * tracepoints_mutex held.
210 */
211static struct tracepoint_entry *add_tracepoint(const char *name)
212{
213    struct hlist_head *head;
214    struct hlist_node *node;
215    struct tracepoint_entry *e;
216    size_t name_len = strlen(name) + 1;
217    u32 hash = jhash(name, name_len-1, 0);
218
219    head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
220    hlist_for_each_entry(e, node, head, hlist) {
221        if (!strcmp(name, e->name)) {
222            printk(KERN_NOTICE
223                "tracepoint %s busy\n", name);
224            return ERR_PTR(-EEXIST); /* Already there */
225        }
226    }
227    /*
228     * Using kmalloc here to allocate a variable length element. Could
229     * cause some memory fragmentation if overused.
230     */
231    e = kmalloc(sizeof(struct tracepoint_entry) + name_len, GFP_KERNEL);
232    if (!e)
233        return ERR_PTR(-ENOMEM);
234    memcpy(&e->name[0], name, name_len);
235    e->funcs = NULL;
236    e->refcount = 0;
237    hlist_add_head(&e->hlist, head);
238    return e;
239}
240
241/*
242 * Remove the tracepoint from the tracepoint hash table. Must be called with
243 * mutex_lock held.
244 */
245static inline void remove_tracepoint(struct tracepoint_entry *e)
246{
247    hlist_del(&e->hlist);
248    kfree(e);
249}
250
251/*
252 * Sets the probe callback corresponding to one tracepoint.
253 */
254static void set_tracepoint(struct tracepoint_entry **entry,
255    struct tracepoint *elem, int active)
256{
257    WARN_ON(strcmp((*entry)->name, elem->name) != 0);
258
259    if (elem->regfunc && !static_key_enabled(&elem->key) && active)
260        elem->regfunc();
261    else if (elem->unregfunc && static_key_enabled(&elem->key) && !active)
262        elem->unregfunc();
263
264    /*
265     * rcu_assign_pointer has a smp_wmb() which makes sure that the new
266     * probe callbacks array is consistent before setting a pointer to it.
267     * This array is referenced by __DO_TRACE from
268     * include/linux/tracepoints.h. A matching smp_read_barrier_depends()
269     * is used.
270     */
271    rcu_assign_pointer(elem->funcs, (*entry)->funcs);
272    if (active && !static_key_enabled(&elem->key))
273        static_key_slow_inc(&elem->key);
274    else if (!active && static_key_enabled(&elem->key))
275        static_key_slow_dec(&elem->key);
276}
277
278/*
279 * Disable a tracepoint and its probe callback.
280 * Note: only waiting an RCU period after setting elem->call to the empty
281 * function insures that the original callback is not used anymore. This insured
282 * by preempt_disable around the call site.
283 */
284static void disable_tracepoint(struct tracepoint *elem)
285{
286    if (elem->unregfunc && static_key_enabled(&elem->key))
287        elem->unregfunc();
288
289    if (static_key_enabled(&elem->key))
290        static_key_slow_dec(&elem->key);
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 * Called with tracepoints_mutex held.
301 */
302static void tracepoint_update_probe_range(struct tracepoint * const *begin,
303                      struct tracepoint * const *end)
304{
305    struct tracepoint * const *iter;
306    struct tracepoint_entry *mark_entry;
307
308    if (!begin)
309        return;
310
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}
321
322#ifdef CONFIG_MODULES
323void module_update_tracepoints(void)
324{
325    struct tp_module *tp_mod;
326
327    list_for_each_entry(tp_mod, &tracepoint_module_list, list)
328        tracepoint_update_probe_range(tp_mod->tracepoints_ptrs,
329            tp_mod->tracepoints_ptrs + tp_mod->num_tracepoints);
330}
331#else /* CONFIG_MODULES */
332void module_update_tracepoints(void)
333{
334}
335#endif /* CONFIG_MODULES */
336
337
338/*
339 * Update probes, removing the faulty probes.
340 * Called with tracepoints_mutex held.
341 */
342static void tracepoint_update_probes(void)
343{
344    /* Core kernel tracepoints */
345    tracepoint_update_probe_range(__start___tracepoints_ptrs,
346        __stop___tracepoints_ptrs);
347    /* tracepoints in modules. */
348    module_update_tracepoints();
349}
350
351static struct tracepoint_func *
352tracepoint_add_probe(const char *name, void *probe, void *data)
353{
354    struct tracepoint_entry *entry;
355    struct tracepoint_func *old;
356
357    entry = get_tracepoint(name);
358    if (!entry) {
359        entry = add_tracepoint(name);
360        if (IS_ERR(entry))
361            return (struct tracepoint_func *)entry;
362    }
363    old = tracepoint_entry_add_probe(entry, probe, data);
364    if (IS_ERR(old) && !entry->refcount)
365        remove_tracepoint(entry);
366    return old;
367}
368
369/**
370 * tracepoint_probe_register - Connect a probe to a tracepoint
371 * @name: tracepoint name
372 * @probe: probe handler
373 *
374 * Returns 0 if ok, error value on error.
375 * The probe address must at least be aligned on the architecture pointer size.
376 */
377int tracepoint_probe_register(const char *name, void *probe, void *data)
378{
379    struct tracepoint_func *old;
380
381    mutex_lock(&tracepoints_mutex);
382    old = tracepoint_add_probe(name, probe, data);
383    if (IS_ERR(old)) {
384        mutex_unlock(&tracepoints_mutex);
385        return PTR_ERR(old);
386    }
387    tracepoint_update_probes(); /* may update entry */
388    mutex_unlock(&tracepoints_mutex);
389    release_probes(old);
390    return 0;
391}
392EXPORT_SYMBOL_GPL(tracepoint_probe_register);
393
394static struct tracepoint_func *
395tracepoint_remove_probe(const char *name, void *probe, void *data)
396{
397    struct tracepoint_entry *entry;
398    struct tracepoint_func *old;
399
400    entry = get_tracepoint(name);
401    if (!entry)
402        return ERR_PTR(-ENOENT);
403    old = tracepoint_entry_remove_probe(entry, probe, data);
404    if (IS_ERR(old))
405        return old;
406    if (!entry->refcount)
407        remove_tracepoint(entry);
408    return old;
409}
410
411/**
412 * tracepoint_probe_unregister - Disconnect a probe from a tracepoint
413 * @name: tracepoint name
414 * @probe: probe function pointer
415 *
416 * We do not need to call a synchronize_sched to make sure the probes have
417 * finished running before doing a module unload, because the module unload
418 * itself uses stop_machine(), which insures that every preempt disabled section
419 * have finished.
420 */
421int tracepoint_probe_unregister(const char *name, void *probe, void *data)
422{
423    struct tracepoint_func *old;
424
425    mutex_lock(&tracepoints_mutex);
426    old = tracepoint_remove_probe(name, probe, data);
427    if (IS_ERR(old)) {
428        mutex_unlock(&tracepoints_mutex);
429        return PTR_ERR(old);
430    }
431    tracepoint_update_probes(); /* may update entry */
432    mutex_unlock(&tracepoints_mutex);
433    release_probes(old);
434    return 0;
435}
436EXPORT_SYMBOL_GPL(tracepoint_probe_unregister);
437
438static LIST_HEAD(old_probes);
439static int need_update;
440
441static void tracepoint_add_old_probes(void *old)
442{
443    need_update = 1;
444    if (old) {
445        struct tp_probes *tp_probes = container_of(old,
446            struct tp_probes, probes[0]);
447        list_add(&tp_probes->u.list, &old_probes);
448    }
449}
450
451/**
452 * tracepoint_probe_register_noupdate - register a probe but not connect
453 * @name: tracepoint name
454 * @probe: probe handler
455 *
456 * caller must call tracepoint_probe_update_all()
457 */
458int tracepoint_probe_register_noupdate(const char *name, void *probe,
459                       void *data)
460{
461    struct tracepoint_func *old;
462
463    mutex_lock(&tracepoints_mutex);
464    old = tracepoint_add_probe(name, probe, data);
465    if (IS_ERR(old)) {
466        mutex_unlock(&tracepoints_mutex);
467        return PTR_ERR(old);
468    }
469    tracepoint_add_old_probes(old);
470    mutex_unlock(&tracepoints_mutex);
471    return 0;
472}
473EXPORT_SYMBOL_GPL(tracepoint_probe_register_noupdate);
474
475/**
476 * tracepoint_probe_unregister_noupdate - remove a probe but not disconnect
477 * @name: tracepoint name
478 * @probe: probe function pointer
479 *
480 * caller must call tracepoint_probe_update_all()
481 */
482int tracepoint_probe_unregister_noupdate(const char *name, void *probe,
483                     void *data)
484{
485    struct tracepoint_func *old;
486
487    mutex_lock(&tracepoints_mutex);
488    old = tracepoint_remove_probe(name, probe, data);
489    if (IS_ERR(old)) {
490        mutex_unlock(&tracepoints_mutex);
491        return PTR_ERR(old);
492    }
493    tracepoint_add_old_probes(old);
494    mutex_unlock(&tracepoints_mutex);
495    return 0;
496}
497EXPORT_SYMBOL_GPL(tracepoint_probe_unregister_noupdate);
498
499/**
500 * tracepoint_probe_update_all - update tracepoints
501 */
502void tracepoint_probe_update_all(void)
503{
504    LIST_HEAD(release_probes);
505    struct tp_probes *pos, *next;
506
507    mutex_lock(&tracepoints_mutex);
508    if (!need_update) {
509        mutex_unlock(&tracepoints_mutex);
510        return;
511    }
512    if (!list_empty(&old_probes))
513        list_replace_init(&old_probes, &release_probes);
514    need_update = 0;
515    tracepoint_update_probes();
516    mutex_unlock(&tracepoints_mutex);
517    list_for_each_entry_safe(pos, next, &release_probes, u.list) {
518        list_del(&pos->u.list);
519        call_rcu_sched(&pos->u.rcu, rcu_free_old_probes);
520    }
521}
522EXPORT_SYMBOL_GPL(tracepoint_probe_update_all);
523
524/**
525 * tracepoint_get_iter_range - Get a next tracepoint iterator given a range.
526 * @tracepoint: current tracepoints (in), next tracepoint (out)
527 * @begin: beginning of the range
528 * @end: end of the range
529 *
530 * Returns whether a next tracepoint has been found (1) or not (0).
531 * Will return the first tracepoint in the range if the input tracepoint is
532 * NULL.
533 */
534static int tracepoint_get_iter_range(struct tracepoint * const **tracepoint,
535    struct tracepoint * const *begin, struct tracepoint * const *end)
536{
537    if (!*tracepoint && begin != end) {
538        *tracepoint = begin;
539        return 1;
540    }
541    if (*tracepoint >= begin && *tracepoint < end)
542        return 1;
543    return 0;
544}
545
546#ifdef CONFIG_MODULES
547static void tracepoint_get_iter(struct tracepoint_iter *iter)
548{
549    int found = 0;
550    struct tp_module *iter_mod;
551
552    /* Core kernel tracepoints */
553    if (!iter->module) {
554        found = tracepoint_get_iter_range(&iter->tracepoint,
555                __start___tracepoints_ptrs,
556                __stop___tracepoints_ptrs);
557        if (found)
558            goto end;
559    }
560    /* Tracepoints in modules */
561    mutex_lock(&tracepoints_mutex);
562    list_for_each_entry(iter_mod, &tracepoint_module_list, list) {
563        /*
564         * Sorted module list
565         */
566        if (iter_mod < iter->module)
567            continue;
568        else if (iter_mod > iter->module)
569            iter->tracepoint = NULL;
570        found = tracepoint_get_iter_range(&iter->tracepoint,
571            iter_mod->tracepoints_ptrs,
572            iter_mod->tracepoints_ptrs
573                + iter_mod->num_tracepoints);
574        if (found) {
575            iter->module = iter_mod;
576            break;
577        }
578    }
579    mutex_unlock(&tracepoints_mutex);
580end:
581    if (!found)
582        tracepoint_iter_reset(iter);
583}
584#else /* CONFIG_MODULES */
585static void tracepoint_get_iter(struct tracepoint_iter *iter)
586{
587    int found = 0;
588
589    /* Core kernel tracepoints */
590    found = tracepoint_get_iter_range(&iter->tracepoint,
591            __start___tracepoints_ptrs,
592            __stop___tracepoints_ptrs);
593    if (!found)
594        tracepoint_iter_reset(iter);
595}
596#endif /* CONFIG_MODULES */
597
598void tracepoint_iter_start(struct tracepoint_iter *iter)
599{
600    tracepoint_get_iter(iter);
601}
602EXPORT_SYMBOL_GPL(tracepoint_iter_start);
603
604void tracepoint_iter_next(struct tracepoint_iter *iter)
605{
606    iter->tracepoint++;
607    /*
608     * iter->tracepoint may be invalid because we blindly incremented it.
609     * Make sure it is valid by marshalling on the tracepoints, getting the
610     * tracepoints from following modules if necessary.
611     */
612    tracepoint_get_iter(iter);
613}
614EXPORT_SYMBOL_GPL(tracepoint_iter_next);
615
616void tracepoint_iter_stop(struct tracepoint_iter *iter)
617{
618}
619EXPORT_SYMBOL_GPL(tracepoint_iter_stop);
620
621void tracepoint_iter_reset(struct tracepoint_iter *iter)
622{
623#ifdef CONFIG_MODULES
624    iter->module = NULL;
625#endif /* CONFIG_MODULES */
626    iter->tracepoint = NULL;
627}
628EXPORT_SYMBOL_GPL(tracepoint_iter_reset);
629
630#ifdef CONFIG_MODULES
631static int tracepoint_module_coming(struct module *mod)
632{
633    struct tp_module *tp_mod, *iter;
634    int ret = 0;
635
636    /*
637     * We skip modules that taint the kernel, especially those with different
638     * module headers (for forced load), to make sure we don't cause a crash.
639     * Staging and out-of-tree GPL modules are fine.
640     */
641    if (mod->taints & ~((1 << TAINT_OOT_MODULE) | (1 << TAINT_CRAP)))
642        return 0;
643    mutex_lock(&tracepoints_mutex);
644    tp_mod = kmalloc(sizeof(struct tp_module), GFP_KERNEL);
645    if (!tp_mod) {
646        ret = -ENOMEM;
647        goto end;
648    }
649    tp_mod->num_tracepoints = mod->num_tracepoints;
650    tp_mod->tracepoints_ptrs = mod->tracepoints_ptrs;
651
652    /*
653     * tracepoint_module_list is kept sorted by struct module pointer
654     * address for iteration on tracepoints from a seq_file that can release
655     * the mutex between calls.
656     */
657    list_for_each_entry_reverse(iter, &tracepoint_module_list, list) {
658        BUG_ON(iter == tp_mod); /* Should never be in the list twice */
659        if (iter < tp_mod) {
660            /* We belong to the location right after iter. */
661            list_add(&tp_mod->list, &iter->list);
662            goto module_added;
663        }
664    }
665    /* We belong to the beginning of the list */
666    list_add(&tp_mod->list, &tracepoint_module_list);
667module_added:
668    tracepoint_update_probe_range(mod->tracepoints_ptrs,
669        mod->tracepoints_ptrs + mod->num_tracepoints);
670end:
671    mutex_unlock(&tracepoints_mutex);
672    return ret;
673}
674
675static int tracepoint_module_going(struct module *mod)
676{
677    struct tp_module *pos;
678
679    mutex_lock(&tracepoints_mutex);
680    tracepoint_update_probe_range(mod->tracepoints_ptrs,
681        mod->tracepoints_ptrs + mod->num_tracepoints);
682    list_for_each_entry(pos, &tracepoint_module_list, list) {
683        if (pos->tracepoints_ptrs == mod->tracepoints_ptrs) {
684            list_del(&pos->list);
685            kfree(pos);
686            break;
687        }
688    }
689    /*
690     * In the case of modules that were tainted at "coming", we'll simply
691     * walk through the list without finding it. We cannot use the "tainted"
692     * flag on "going", in case a module taints the kernel only after being
693     * loaded.
694     */
695    mutex_unlock(&tracepoints_mutex);
696    return 0;
697}
698
699int tracepoint_module_notify(struct notifier_block *self,
700                 unsigned long val, void *data)
701{
702    struct module *mod = data;
703    int ret = 0;
704
705    switch (val) {
706    case MODULE_STATE_COMING:
707        ret = tracepoint_module_coming(mod);
708        break;
709    case MODULE_STATE_LIVE:
710        break;
711    case MODULE_STATE_GOING:
712        ret = tracepoint_module_going(mod);
713        break;
714    }
715    return ret;
716}
717
718struct notifier_block tracepoint_module_nb = {
719    .notifier_call = tracepoint_module_notify,
720    .priority = 0,
721};
722
723static int init_tracepoints(void)
724{
725    return register_module_notifier(&tracepoint_module_nb);
726}
727__initcall(init_tracepoints);
728#endif /* CONFIG_MODULES */
729
730#ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
731
732/* NB: reg/unreg are called while guarded with the tracepoints_mutex */
733static int sys_tracepoint_refcount;
734
735void syscall_regfunc(void)
736{
737    unsigned long flags;
738    struct task_struct *g, *t;
739
740    if (!sys_tracepoint_refcount) {
741        read_lock_irqsave(&tasklist_lock, flags);
742        do_each_thread(g, t) {
743            /* Skip kernel threads. */
744            if (t->mm)
745                set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
746        } while_each_thread(g, t);
747        read_unlock_irqrestore(&tasklist_lock, flags);
748    }
749    sys_tracepoint_refcount++;
750}
751
752void syscall_unregfunc(void)
753{
754    unsigned long flags;
755    struct task_struct *g, *t;
756
757    sys_tracepoint_refcount--;
758    if (!sys_tracepoint_refcount) {
759        read_lock_irqsave(&tasklist_lock, flags);
760        do_each_thread(g, t) {
761            clear_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
762        } while_each_thread(g, t);
763        read_unlock_irqrestore(&tasklist_lock, flags);
764    }
765}
766#endif
767

Archive Download this file



interactive