2 * Copyright (C) 2007 Mathieu Desnoyers
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.
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.
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.
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/marker.h>
25 #include <linux/err.h>
26 #include <linux/slab.h>
28 extern struct marker __start___markers
[];
29 extern struct marker __stop___markers
[];
31 /* Set to 1 to enable marker debug output */
32 static const int marker_debug
;
35 * markers_mutex nests inside module_mutex. Markers mutex protects the builtin
36 * and module markers and the hash table.
38 static DEFINE_MUTEX(markers_mutex
);
41 * Marker hash table, containing the active markers.
42 * Protected by module_mutex.
44 #define MARKER_HASH_BITS 6
45 #define MARKER_TABLE_SIZE (1 << MARKER_HASH_BITS)
49 * It is used to make sure every handler has finished using its private data
50 * between two consecutive operation (add or remove) on a given marker. It is
51 * also used to delay the free of multiple probes array until a quiescent state
53 * marker entries modifications are protected by the markers_mutex.
56 struct hlist_node hlist
;
59 void (*call
)(const struct marker
*mdata
, void *call_private
, ...);
60 struct marker_probe_closure single
;
61 struct marker_probe_closure
*multi
;
62 int refcount
; /* Number of times armed. 0 if disarmed. */
63 unsigned char ptype
:1;
64 char name
[0]; /* Contains name'\0'format'\0' */
67 static struct hlist_head marker_table
[MARKER_TABLE_SIZE
];
70 * __mark_empty_function - Empty probe callback
71 * @probe_private: probe private data
72 * @call_private: call site private data
74 * @...: variable argument list
76 * Empty callback provided as a probe to the markers. By providing this to a
77 * disabled marker, we make sure the execution flow is always valid even
78 * though the function pointer change and the marker enabling are two distinct
79 * operations that modifies the execution flow of preemptible code.
81 void __mark_empty_function(void *probe_private
, void *call_private
,
82 const char *fmt
, va_list *args
)
85 EXPORT_SYMBOL_GPL(__mark_empty_function
);
88 * marker_probe_cb Callback that prepares the variable argument list for probes.
89 * @mdata: pointer of type struct marker
90 * @call_private: caller site private data
91 * @...: Variable argument list.
93 * Since we do not use "typical" pointer based RCU in the 1 argument case, we
94 * need to put a full smp_rmb() in this branch. This is why we do not use
95 * rcu_dereference() for the pointer read.
97 void marker_probe_cb(const struct marker
*mdata
, void *call_private
, ...)
103 * rcu_read_lock_sched does two things : disabling preemption to make
104 * sure the teardown of the callbacks can be done correctly when they
105 * are in modules and they insure RCU read coherency.
107 rcu_read_lock_sched();
108 ptype
= mdata
->ptype
;
109 if (likely(!ptype
)) {
110 marker_probe_func
*func
;
111 /* Must read the ptype before ptr. They are not data dependant,
112 * so we put an explicit smp_rmb() here. */
114 func
= mdata
->single
.func
;
115 /* Must read the ptr before private data. They are not data
116 * dependant, so we put an explicit smp_rmb() here. */
118 va_start(args
, call_private
);
119 func(mdata
->single
.probe_private
, call_private
, mdata
->format
,
123 struct marker_probe_closure
*multi
;
126 * Read mdata->ptype before mdata->multi.
129 multi
= mdata
->multi
;
131 * multi points to an array, therefore accessing the array
132 * depends on reading multi. However, even in this case,
133 * we must insure that the pointer is read _before_ the array
134 * data. Same as rcu_dereference, but we need a full smp_rmb()
135 * in the fast path, so put the explicit barrier here.
137 smp_read_barrier_depends();
138 for (i
= 0; multi
[i
].func
; i
++) {
139 va_start(args
, call_private
);
140 multi
[i
].func(multi
[i
].probe_private
, call_private
,
141 mdata
->format
, &args
);
145 rcu_read_unlock_sched();
147 EXPORT_SYMBOL_GPL(marker_probe_cb
);
150 * marker_probe_cb Callback that does not prepare the variable argument list.
151 * @mdata: pointer of type struct marker
152 * @call_private: caller site private data
153 * @...: Variable argument list.
155 * Should be connected to markers "MARK_NOARGS".
157 void marker_probe_cb_noarg(const struct marker
*mdata
, void *call_private
, ...)
159 va_list args
; /* not initialized */
162 rcu_read_lock_sched();
163 ptype
= mdata
->ptype
;
164 if (likely(!ptype
)) {
165 marker_probe_func
*func
;
166 /* Must read the ptype before ptr. They are not data dependant,
167 * so we put an explicit smp_rmb() here. */
169 func
= mdata
->single
.func
;
170 /* Must read the ptr before private data. They are not data
171 * dependant, so we put an explicit smp_rmb() here. */
173 func(mdata
->single
.probe_private
, call_private
, mdata
->format
,
176 struct marker_probe_closure
*multi
;
179 * Read mdata->ptype before mdata->multi.
182 multi
= mdata
->multi
;
184 * multi points to an array, therefore accessing the array
185 * depends on reading multi. However, even in this case,
186 * we must insure that the pointer is read _before_ the array
187 * data. Same as rcu_dereference, but we need a full smp_rmb()
188 * in the fast path, so put the explicit barrier here.
190 smp_read_barrier_depends();
191 for (i
= 0; multi
[i
].func
; i
++)
192 multi
[i
].func(multi
[i
].probe_private
, call_private
,
193 mdata
->format
, &args
);
195 rcu_read_unlock_sched();
197 EXPORT_SYMBOL_GPL(marker_probe_cb_noarg
);
199 static void debug_print_probes(struct marker_entry
*entry
)
207 printk(KERN_DEBUG
"Single probe : %p %p\n",
209 entry
->single
.probe_private
);
211 for (i
= 0; entry
->multi
[i
].func
; i
++)
212 printk(KERN_DEBUG
"Multi probe %d : %p %p\n", i
,
213 entry
->multi
[i
].func
,
214 entry
->multi
[i
].probe_private
);
218 static struct marker_probe_closure
*
219 marker_entry_add_probe(struct marker_entry
*entry
,
220 marker_probe_func
*probe
, void *probe_private
)
223 struct marker_probe_closure
*old
, *new;
227 debug_print_probes(entry
);
230 if (entry
->single
.func
== probe
&&
231 entry
->single
.probe_private
== probe_private
)
232 return ERR_PTR(-EBUSY
);
233 if (entry
->single
.func
== __mark_empty_function
) {
235 entry
->single
.func
= probe
;
236 entry
->single
.probe_private
= probe_private
;
239 debug_print_probes(entry
);
247 /* (N -> N+1), (N != 0, 1) probes */
248 for (nr_probes
= 0; old
[nr_probes
].func
; nr_probes
++)
249 if (old
[nr_probes
].func
== probe
250 && old
[nr_probes
].probe_private
252 return ERR_PTR(-EBUSY
);
254 /* + 2 : one for new probe, one for NULL func */
255 new = kzalloc((nr_probes
+ 2) * sizeof(struct marker_probe_closure
),
258 return ERR_PTR(-ENOMEM
);
260 new[0] = entry
->single
;
263 nr_probes
* sizeof(struct marker_probe_closure
));
264 new[nr_probes
].func
= probe
;
265 new[nr_probes
].probe_private
= probe_private
;
266 entry
->refcount
= nr_probes
+ 1;
269 debug_print_probes(entry
);
273 static struct marker_probe_closure
*
274 marker_entry_remove_probe(struct marker_entry
*entry
,
275 marker_probe_func
*probe
, void *probe_private
)
277 int nr_probes
= 0, nr_del
= 0, i
;
278 struct marker_probe_closure
*old
, *new;
282 debug_print_probes(entry
);
284 /* 0 -> N is an error */
285 WARN_ON(entry
->single
.func
== __mark_empty_function
);
287 WARN_ON(probe
&& entry
->single
.func
!= probe
);
288 WARN_ON(entry
->single
.probe_private
!= probe_private
);
289 entry
->single
.func
= __mark_empty_function
;
292 debug_print_probes(entry
);
295 /* (N -> M), (N > 1, M >= 0) probes */
296 for (nr_probes
= 0; old
[nr_probes
].func
; nr_probes
++) {
297 if ((!probe
|| old
[nr_probes
].func
== probe
)
298 && old
[nr_probes
].probe_private
304 if (nr_probes
- nr_del
== 0) {
305 /* N -> 0, (N > 1) */
306 entry
->single
.func
= __mark_empty_function
;
309 } else if (nr_probes
- nr_del
== 1) {
310 /* N -> 1, (N > 1) */
311 for (i
= 0; old
[i
].func
; i
++)
312 if ((probe
&& old
[i
].func
!= probe
) ||
313 old
[i
].probe_private
!= probe_private
)
314 entry
->single
= old
[i
];
319 /* N -> M, (N > 1, M > 1) */
321 new = kzalloc((nr_probes
- nr_del
+ 1)
322 * sizeof(struct marker_probe_closure
), GFP_KERNEL
);
324 return ERR_PTR(-ENOMEM
);
325 for (i
= 0; old
[i
].func
; i
++)
326 if ((probe
&& old
[i
].func
!= probe
) ||
327 old
[i
].probe_private
!= probe_private
)
329 entry
->refcount
= nr_probes
- nr_del
;
333 debug_print_probes(entry
);
338 * Get marker if the marker is present in the marker hash table.
339 * Must be called with markers_mutex held.
340 * Returns NULL if not present.
342 static struct marker_entry
*get_marker(const char *name
)
344 struct hlist_head
*head
;
345 struct hlist_node
*node
;
346 struct marker_entry
*e
;
347 u32 hash
= jhash(name
, strlen(name
), 0);
349 head
= &marker_table
[hash
& ((1 << MARKER_HASH_BITS
)-1)];
350 hlist_for_each_entry(e
, node
, head
, hlist
) {
351 if (!strcmp(name
, e
->name
))
358 * Add the marker to the marker hash table. Must be called with markers_mutex
361 static struct marker_entry
*add_marker(const char *name
, const char *format
)
363 struct hlist_head
*head
;
364 struct hlist_node
*node
;
365 struct marker_entry
*e
;
366 size_t name_len
= strlen(name
) + 1;
367 size_t format_len
= 0;
368 u32 hash
= jhash(name
, name_len
-1, 0);
371 format_len
= strlen(format
) + 1;
372 head
= &marker_table
[hash
& ((1 << MARKER_HASH_BITS
)-1)];
373 hlist_for_each_entry(e
, node
, head
, hlist
) {
374 if (!strcmp(name
, e
->name
)) {
376 "Marker %s busy\n", name
);
377 return ERR_PTR(-EBUSY
); /* Already there */
381 * Using kmalloc here to allocate a variable length element. Could
382 * cause some memory fragmentation if overused.
384 e
= kmalloc(sizeof(struct marker_entry
) + name_len
+ format_len
,
387 return ERR_PTR(-ENOMEM
);
388 memcpy(&e
->name
[0], name
, name_len
);
390 e
->format
= &e
->name
[name_len
];
391 memcpy(e
->format
, format
, format_len
);
392 if (strcmp(e
->format
, MARK_NOARGS
) == 0)
393 e
->call
= marker_probe_cb_noarg
;
395 e
->call
= marker_probe_cb
;
396 trace_mark(core_marker_format
, "name %s format %s",
400 e
->call
= marker_probe_cb
;
402 e
->single
.func
= __mark_empty_function
;
403 e
->single
.probe_private
= NULL
;
407 hlist_add_head(&e
->hlist
, head
);
412 * Remove the marker from the marker hash table. Must be called with mutex_lock
415 static int remove_marker(const char *name
)
417 struct hlist_head
*head
;
418 struct hlist_node
*node
;
419 struct marker_entry
*e
;
421 size_t len
= strlen(name
) + 1;
422 u32 hash
= jhash(name
, len
-1, 0);
424 head
= &marker_table
[hash
& ((1 << MARKER_HASH_BITS
)-1)];
425 hlist_for_each_entry(e
, node
, head
, hlist
) {
426 if (!strcmp(name
, e
->name
)) {
433 if (e
->single
.func
!= __mark_empty_function
)
435 hlist_del(&e
->hlist
);
441 * Set the mark_entry format to the format found in the element.
443 static int marker_set_format(struct marker_entry
**entry
, const char *format
)
445 struct marker_entry
*e
;
446 size_t name_len
= strlen((*entry
)->name
) + 1;
447 size_t format_len
= strlen(format
) + 1;
450 e
= kmalloc(sizeof(struct marker_entry
) + name_len
+ format_len
,
454 memcpy(&e
->name
[0], (*entry
)->name
, name_len
);
455 e
->format
= &e
->name
[name_len
];
456 memcpy(e
->format
, format
, format_len
);
457 if (strcmp(e
->format
, MARK_NOARGS
) == 0)
458 e
->call
= marker_probe_cb_noarg
;
460 e
->call
= marker_probe_cb
;
461 e
->single
= (*entry
)->single
;
462 e
->multi
= (*entry
)->multi
;
463 e
->ptype
= (*entry
)->ptype
;
464 e
->refcount
= (*entry
)->refcount
;
465 hlist_add_before(&e
->hlist
, &(*entry
)->hlist
);
466 hlist_del(&(*entry
)->hlist
);
469 trace_mark(core_marker_format
, "name %s format %s",
475 * Sets the probe callback corresponding to one marker.
477 static int set_marker(struct marker_entry
**entry
, struct marker
*elem
,
481 WARN_ON(strcmp((*entry
)->name
, elem
->name
) != 0);
483 if ((*entry
)->format
) {
484 if (strcmp((*entry
)->format
, elem
->format
) != 0) {
486 "Format mismatch for probe %s "
487 "(%s), marker (%s)\n",
494 ret
= marker_set_format(entry
, elem
->format
);
500 * probe_cb setup (statically known) is done here. It is
501 * asynchronous with the rest of execution, therefore we only
502 * pass from a "safe" callback (with argument) to an "unsafe"
503 * callback (does not set arguments).
505 elem
->call
= (*entry
)->call
;
508 * We only update the single probe private data when the ptr is
509 * set to a _non_ single probe! (0 -> 1 and N -> 1, N != 1)
511 WARN_ON(elem
->single
.func
!= __mark_empty_function
512 && elem
->single
.probe_private
513 != (*entry
)->single
.probe_private
&&
515 elem
->single
.probe_private
= (*entry
)->single
.probe_private
;
517 * Make sure the private data is valid when we update the
521 elem
->single
.func
= (*entry
)->single
.func
;
523 * We also make sure that the new probe callbacks array is consistent
524 * before setting a pointer to it.
526 rcu_assign_pointer(elem
->multi
, (*entry
)->multi
);
528 * Update the function or multi probe array pointer before setting the
532 elem
->ptype
= (*entry
)->ptype
;
533 elem
->state
= active
;
539 * Disable a marker and its probe callback.
540 * Note: only waiting an RCU period after setting elem->call to the empty
541 * function insures that the original callback is not used anymore. This insured
542 * by rcu_read_lock_sched around the call site.
544 static void disable_marker(struct marker
*elem
)
546 /* leave "call" as is. It is known statically. */
548 elem
->single
.func
= __mark_empty_function
;
549 /* Update the function before setting the ptype */
551 elem
->ptype
= 0; /* single probe */
553 * Leave the private data and id there, because removal is racy and
554 * should be done only after an RCU period. These are never used until
555 * the next initialization anyway.
560 * marker_update_probe_range - Update a probe range
561 * @begin: beginning of the range
562 * @end: end of the range
564 * Updates the probe callback corresponding to a range of markers.
566 void marker_update_probe_range(struct marker
*begin
,
570 struct marker_entry
*mark_entry
;
572 mutex_lock(&markers_mutex
);
573 for (iter
= begin
; iter
< end
; iter
++) {
574 mark_entry
= get_marker(iter
->name
);
576 set_marker(&mark_entry
, iter
,
577 !!mark_entry
->refcount
);
579 * ignore error, continue
582 disable_marker(iter
);
585 mutex_unlock(&markers_mutex
);
589 * Update probes, removing the faulty probes.
591 * Internal callback only changed before the first probe is connected to it.
592 * Single probe private data can only be changed on 0 -> 1 and 2 -> 1
593 * transitions. All other transitions will leave the old private data valid.
594 * This makes the non-atomicity of the callback/private data updates valid.
596 * "special case" updates :
601 * Other updates all behave the same, just like the 2 -> 3 or 3 -> 2 updates.
602 * Site effect : marker_set_format may delete the marker entry (creating a
605 static void marker_update_probes(void)
607 /* Core kernel markers */
608 marker_update_probe_range(__start___markers
, __stop___markers
);
609 /* Markers in modules. */
610 module_update_markers();
614 * marker_probe_register - Connect a probe to a marker
616 * @format: format string
617 * @probe: probe handler
618 * @probe_private: probe private data
620 * private data must be a valid allocated memory address, or NULL.
621 * Returns 0 if ok, error value on error.
622 * The probe address must at least be aligned on the architecture pointer size.
624 int marker_probe_register(const char *name
, const char *format
,
625 marker_probe_func
*probe
, void *probe_private
)
627 struct marker_entry
*entry
;
629 struct marker_probe_closure
*old
;
631 mutex_lock(&markers_mutex
);
632 entry
= get_marker(name
);
634 entry
= add_marker(name
, format
);
636 ret
= PTR_ERR(entry
);
640 old
= marker_entry_add_probe(entry
, probe
, probe_private
);
645 mutex_unlock(&markers_mutex
);
646 marker_update_probes(); /* may update entry */
649 mutex_lock(&markers_mutex
);
650 entry
= get_marker(name
);
653 mutex_unlock(&markers_mutex
);
656 EXPORT_SYMBOL_GPL(marker_probe_register
);
659 * marker_probe_unregister - Disconnect a probe from a marker
661 * @probe: probe function pointer
662 * @probe_private: probe private data
664 * Returns the private data given to marker_probe_register, or an ERR_PTR().
665 * We do not need to call a synchronize_sched to make sure the probes have
666 * finished running before doing a module unload, because the module unload
667 * itself uses stop_machine(), which insures that every preempt disabled section
670 int marker_probe_unregister(const char *name
,
671 marker_probe_func
*probe
, void *probe_private
)
673 struct marker_entry
*entry
;
674 struct marker_probe_closure
*old
;
677 mutex_lock(&markers_mutex
);
678 entry
= get_marker(name
);
681 old
= marker_entry_remove_probe(entry
, probe
, probe_private
);
682 mutex_unlock(&markers_mutex
);
683 marker_update_probes(); /* may update entry */
686 mutex_lock(&markers_mutex
);
687 entry
= get_marker(name
);
690 remove_marker(name
); /* Ignore busy error message */
693 mutex_unlock(&markers_mutex
);
696 EXPORT_SYMBOL_GPL(marker_probe_unregister
);
698 static struct marker_entry
*
699 get_marker_from_private_data(marker_probe_func
*probe
, void *probe_private
)
701 struct marker_entry
*entry
;
703 struct hlist_head
*head
;
704 struct hlist_node
*node
;
706 for (i
= 0; i
< MARKER_TABLE_SIZE
; i
++) {
707 head
= &marker_table
[i
];
708 hlist_for_each_entry(entry
, node
, head
, hlist
) {
710 if (entry
->single
.func
== probe
711 && entry
->single
.probe_private
715 struct marker_probe_closure
*closure
;
716 closure
= entry
->multi
;
717 for (i
= 0; closure
[i
].func
; i
++) {
718 if (closure
[i
].func
== probe
&&
719 closure
[i
].probe_private
730 * marker_probe_unregister_private_data - Disconnect a probe from a marker
731 * @probe: probe function
732 * @probe_private: probe private data
734 * Unregister a probe by providing the registered private data.
735 * Only removes the first marker found in hash table.
736 * Return 0 on success or error value.
737 * We do not need to call a synchronize_sched to make sure the probes have
738 * finished running before doing a module unload, because the module unload
739 * itself uses stop_machine(), which insures that every preempt disabled section
742 int marker_probe_unregister_private_data(marker_probe_func
*probe
,
745 struct marker_entry
*entry
;
747 struct marker_probe_closure
*old
;
749 mutex_lock(&markers_mutex
);
750 entry
= get_marker_from_private_data(probe
, probe_private
);
755 old
= marker_entry_remove_probe(entry
, NULL
, probe_private
);
756 mutex_unlock(&markers_mutex
);
757 marker_update_probes(); /* may update entry */
760 mutex_lock(&markers_mutex
);
761 entry
= get_marker_from_private_data(probe
, probe_private
);
763 remove_marker(entry
->name
); /* Ignore busy error message */
765 mutex_unlock(&markers_mutex
);
768 EXPORT_SYMBOL_GPL(marker_probe_unregister_private_data
);
771 * marker_get_private_data - Get a marker's probe private data
773 * @probe: probe to match
774 * @num: get the nth matching probe's private data
776 * Returns the nth private data pointer (starting from 0) matching, or an
778 * Returns the private data pointer, or an ERR_PTR.
779 * The private data pointer should _only_ be dereferenced if the caller is the
780 * owner of the data, or its content could vanish. This is mostly used to
781 * confirm that a caller is the owner of a registered probe.
783 void *marker_get_private_data(const char *name
, marker_probe_func
*probe
,
786 struct hlist_head
*head
;
787 struct hlist_node
*node
;
788 struct marker_entry
*e
;
789 size_t name_len
= strlen(name
) + 1;
790 u32 hash
= jhash(name
, name_len
-1, 0);
793 head
= &marker_table
[hash
& ((1 << MARKER_HASH_BITS
)-1)];
794 hlist_for_each_entry(e
, node
, head
, hlist
) {
795 if (!strcmp(name
, e
->name
)) {
797 if (num
== 0 && e
->single
.func
== probe
)
798 return e
->single
.probe_private
;
802 struct marker_probe_closure
*closure
;
805 for (i
= 0; closure
[i
].func
; i
++) {
806 if (closure
[i
].func
!= probe
)
809 return closure
[i
].probe_private
;
814 return ERR_PTR(-ENOENT
);
816 EXPORT_SYMBOL_GPL(marker_get_private_data
);