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. */
65 unsigned char rcu_pending
:1;
66 unsigned char ptype
:1;
67 char name
[0]; /* Contains name'\0'format'\0' */
70 static struct hlist_head marker_table
[MARKER_TABLE_SIZE
];
73 * __mark_empty_function - Empty probe callback
74 * @probe_private: probe private data
75 * @call_private: call site private data
77 * @...: variable argument list
79 * Empty callback provided as a probe to the markers. By providing this to a
80 * disabled marker, we make sure the execution flow is always valid even
81 * though the function pointer change and the marker enabling are two distinct
82 * operations that modifies the execution flow of preemptible code.
84 void __mark_empty_function(void *probe_private
, void *call_private
,
85 const char *fmt
, va_list *args
)
88 EXPORT_SYMBOL_GPL(__mark_empty_function
);
91 * marker_probe_cb Callback that prepares the variable argument list for probes.
92 * @mdata: pointer of type struct marker
93 * @call_private: caller site private data
94 * @...: Variable argument list.
96 * Since we do not use "typical" pointer based RCU in the 1 argument case, we
97 * need to put a full smp_rmb() in this branch. This is why we do not use
98 * rcu_dereference() for the pointer read.
100 void marker_probe_cb(const struct marker
*mdata
, void *call_private
, ...)
106 * preempt_disable does two things : disabling preemption to make sure
107 * the teardown of the callbacks can be done correctly when they are in
108 * modules and they insure RCU read coherency.
111 ptype
= mdata
->ptype
;
112 if (likely(!ptype
)) {
113 marker_probe_func
*func
;
114 /* Must read the ptype before ptr. They are not data dependant,
115 * so we put an explicit smp_rmb() here. */
117 func
= mdata
->single
.func
;
118 /* Must read the ptr before private data. They are not data
119 * dependant, so we put an explicit smp_rmb() here. */
121 va_start(args
, call_private
);
122 func(mdata
->single
.probe_private
, call_private
, mdata
->format
,
126 struct marker_probe_closure
*multi
;
129 * multi points to an array, therefore accessing the array
130 * depends on reading multi. However, even in this case,
131 * we must insure that the pointer is read _before_ the array
132 * data. Same as rcu_dereference, but we need a full smp_rmb()
133 * in the fast path, so put the explicit barrier here.
135 smp_read_barrier_depends();
136 multi
= mdata
->multi
;
137 for (i
= 0; multi
[i
].func
; i
++) {
138 va_start(args
, call_private
);
139 multi
[i
].func(multi
[i
].probe_private
, call_private
,
140 mdata
->format
, &args
);
146 EXPORT_SYMBOL_GPL(marker_probe_cb
);
149 * marker_probe_cb Callback that does not prepare the variable argument list.
150 * @mdata: pointer of type struct marker
151 * @call_private: caller site private data
152 * @...: Variable argument list.
154 * Should be connected to markers "MARK_NOARGS".
156 void marker_probe_cb_noarg(const struct marker
*mdata
, void *call_private
, ...)
158 va_list args
; /* not initialized */
162 ptype
= mdata
->ptype
;
163 if (likely(!ptype
)) {
164 marker_probe_func
*func
;
165 /* Must read the ptype before ptr. They are not data dependant,
166 * so we put an explicit smp_rmb() here. */
168 func
= mdata
->single
.func
;
169 /* Must read the ptr before private data. They are not data
170 * dependant, so we put an explicit smp_rmb() here. */
172 func(mdata
->single
.probe_private
, call_private
, mdata
->format
,
175 struct marker_probe_closure
*multi
;
178 * multi points to an array, therefore accessing the array
179 * depends on reading multi. However, even in this case,
180 * we must insure that the pointer is read _before_ the array
181 * data. Same as rcu_dereference, but we need a full smp_rmb()
182 * in the fast path, so put the explicit barrier here.
184 smp_read_barrier_depends();
185 multi
= mdata
->multi
;
186 for (i
= 0; multi
[i
].func
; i
++)
187 multi
[i
].func(multi
[i
].probe_private
, call_private
,
188 mdata
->format
, &args
);
192 EXPORT_SYMBOL_GPL(marker_probe_cb_noarg
);
194 static void free_old_closure(struct rcu_head
*head
)
196 struct marker_entry
*entry
= container_of(head
,
197 struct marker_entry
, rcu
);
198 kfree(entry
->oldptr
);
199 /* Make sure we free the data before setting the pending flag to 0 */
201 entry
->rcu_pending
= 0;
204 static void debug_print_probes(struct marker_entry
*entry
)
212 printk(KERN_DEBUG
"Single probe : %p %p\n",
214 entry
->single
.probe_private
);
216 for (i
= 0; entry
->multi
[i
].func
; i
++)
217 printk(KERN_DEBUG
"Multi probe %d : %p %p\n", i
,
218 entry
->multi
[i
].func
,
219 entry
->multi
[i
].probe_private
);
223 static struct marker_probe_closure
*
224 marker_entry_add_probe(struct marker_entry
*entry
,
225 marker_probe_func
*probe
, void *probe_private
)
228 struct marker_probe_closure
*old
, *new;
232 debug_print_probes(entry
);
235 if (entry
->single
.func
== probe
&&
236 entry
->single
.probe_private
== probe_private
)
237 return ERR_PTR(-EBUSY
);
238 if (entry
->single
.func
== __mark_empty_function
) {
240 entry
->single
.func
= probe
;
241 entry
->single
.probe_private
= probe_private
;
244 debug_print_probes(entry
);
252 /* (N -> N+1), (N != 0, 1) probes */
253 for (nr_probes
= 0; old
[nr_probes
].func
; nr_probes
++)
254 if (old
[nr_probes
].func
== probe
255 && old
[nr_probes
].probe_private
257 return ERR_PTR(-EBUSY
);
259 /* + 2 : one for new probe, one for NULL func */
260 new = kzalloc((nr_probes
+ 2) * sizeof(struct marker_probe_closure
),
263 return ERR_PTR(-ENOMEM
);
265 new[0] = entry
->single
;
268 nr_probes
* sizeof(struct marker_probe_closure
));
269 new[nr_probes
].func
= probe
;
270 new[nr_probes
].probe_private
= probe_private
;
271 entry
->refcount
= nr_probes
+ 1;
274 debug_print_probes(entry
);
278 static struct marker_probe_closure
*
279 marker_entry_remove_probe(struct marker_entry
*entry
,
280 marker_probe_func
*probe
, void *probe_private
)
282 int nr_probes
= 0, nr_del
= 0, i
;
283 struct marker_probe_closure
*old
, *new;
287 debug_print_probes(entry
);
289 /* 0 -> N is an error */
290 WARN_ON(entry
->single
.func
== __mark_empty_function
);
292 WARN_ON(probe
&& entry
->single
.func
!= probe
);
293 WARN_ON(entry
->single
.probe_private
!= probe_private
);
294 entry
->single
.func
= __mark_empty_function
;
297 debug_print_probes(entry
);
300 /* (N -> M), (N > 1, M >= 0) probes */
301 for (nr_probes
= 0; old
[nr_probes
].func
; nr_probes
++) {
302 if ((!probe
|| old
[nr_probes
].func
== probe
)
303 && old
[nr_probes
].probe_private
309 if (nr_probes
- nr_del
== 0) {
310 /* N -> 0, (N > 1) */
311 entry
->single
.func
= __mark_empty_function
;
314 } else if (nr_probes
- nr_del
== 1) {
315 /* N -> 1, (N > 1) */
316 for (i
= 0; old
[i
].func
; i
++)
317 if ((probe
&& old
[i
].func
!= probe
) ||
318 old
[i
].probe_private
!= probe_private
)
319 entry
->single
= old
[i
];
324 /* N -> M, (N > 1, M > 1) */
326 new = kzalloc((nr_probes
- nr_del
+ 1)
327 * sizeof(struct marker_probe_closure
), GFP_KERNEL
);
329 return ERR_PTR(-ENOMEM
);
330 for (i
= 0; old
[i
].func
; i
++)
331 if ((probe
&& old
[i
].func
!= probe
) ||
332 old
[i
].probe_private
!= probe_private
)
334 entry
->refcount
= nr_probes
- nr_del
;
338 debug_print_probes(entry
);
343 * Get marker if the marker is present in the marker hash table.
344 * Must be called with markers_mutex held.
345 * Returns NULL if not present.
347 static struct marker_entry
*get_marker(const char *name
)
349 struct hlist_head
*head
;
350 struct hlist_node
*node
;
351 struct marker_entry
*e
;
352 u32 hash
= jhash(name
, strlen(name
), 0);
354 head
= &marker_table
[hash
& ((1 << MARKER_HASH_BITS
)-1)];
355 hlist_for_each_entry(e
, node
, head
, hlist
) {
356 if (!strcmp(name
, e
->name
))
363 * Add the marker to the marker hash table. Must be called with markers_mutex
366 static struct marker_entry
*add_marker(const char *name
, const char *format
)
368 struct hlist_head
*head
;
369 struct hlist_node
*node
;
370 struct marker_entry
*e
;
371 size_t name_len
= strlen(name
) + 1;
372 size_t format_len
= 0;
373 u32 hash
= jhash(name
, name_len
-1, 0);
376 format_len
= strlen(format
) + 1;
377 head
= &marker_table
[hash
& ((1 << MARKER_HASH_BITS
)-1)];
378 hlist_for_each_entry(e
, node
, head
, hlist
) {
379 if (!strcmp(name
, e
->name
)) {
381 "Marker %s busy\n", name
);
382 return ERR_PTR(-EBUSY
); /* Already there */
386 * Using kmalloc here to allocate a variable length element. Could
387 * cause some memory fragmentation if overused.
389 e
= kmalloc(sizeof(struct marker_entry
) + name_len
+ format_len
,
392 return ERR_PTR(-ENOMEM
);
393 memcpy(&e
->name
[0], name
, name_len
);
395 e
->format
= &e
->name
[name_len
];
396 memcpy(e
->format
, format
, format_len
);
397 if (strcmp(e
->format
, MARK_NOARGS
) == 0)
398 e
->call
= marker_probe_cb_noarg
;
400 e
->call
= marker_probe_cb
;
401 trace_mark(core_marker_format
, "name %s format %s",
405 e
->call
= marker_probe_cb
;
407 e
->single
.func
= __mark_empty_function
;
408 e
->single
.probe_private
= NULL
;
413 hlist_add_head(&e
->hlist
, head
);
418 * Remove the marker from the marker hash table. Must be called with mutex_lock
421 static int remove_marker(const char *name
)
423 struct hlist_head
*head
;
424 struct hlist_node
*node
;
425 struct marker_entry
*e
;
427 size_t len
= strlen(name
) + 1;
428 u32 hash
= jhash(name
, len
-1, 0);
430 head
= &marker_table
[hash
& ((1 << MARKER_HASH_BITS
)-1)];
431 hlist_for_each_entry(e
, node
, head
, hlist
) {
432 if (!strcmp(name
, e
->name
)) {
439 if (e
->single
.func
!= __mark_empty_function
)
441 hlist_del(&e
->hlist
);
442 /* Make sure the call_rcu has been executed */
450 * Set the mark_entry format to the format found in the element.
452 static int marker_set_format(struct marker_entry
**entry
, const char *format
)
454 struct marker_entry
*e
;
455 size_t name_len
= strlen((*entry
)->name
) + 1;
456 size_t format_len
= strlen(format
) + 1;
459 e
= kmalloc(sizeof(struct marker_entry
) + name_len
+ format_len
,
463 memcpy(&e
->name
[0], (*entry
)->name
, name_len
);
464 e
->format
= &e
->name
[name_len
];
465 memcpy(e
->format
, format
, format_len
);
466 if (strcmp(e
->format
, MARK_NOARGS
) == 0)
467 e
->call
= marker_probe_cb_noarg
;
469 e
->call
= marker_probe_cb
;
470 e
->single
= (*entry
)->single
;
471 e
->multi
= (*entry
)->multi
;
472 e
->ptype
= (*entry
)->ptype
;
473 e
->refcount
= (*entry
)->refcount
;
475 hlist_add_before(&e
->hlist
, &(*entry
)->hlist
);
476 hlist_del(&(*entry
)->hlist
);
477 /* Make sure the call_rcu has been executed */
478 if ((*entry
)->rcu_pending
)
482 trace_mark(core_marker_format
, "name %s format %s",
488 * Sets the probe callback corresponding to one marker.
490 static int set_marker(struct marker_entry
**entry
, struct marker
*elem
,
494 WARN_ON(strcmp((*entry
)->name
, elem
->name
) != 0);
496 if ((*entry
)->format
) {
497 if (strcmp((*entry
)->format
, elem
->format
) != 0) {
499 "Format mismatch for probe %s "
500 "(%s), marker (%s)\n",
507 ret
= marker_set_format(entry
, elem
->format
);
513 * probe_cb setup (statically known) is done here. It is
514 * asynchronous with the rest of execution, therefore we only
515 * pass from a "safe" callback (with argument) to an "unsafe"
516 * callback (does not set arguments).
518 elem
->call
= (*entry
)->call
;
521 * We only update the single probe private data when the ptr is
522 * set to a _non_ single probe! (0 -> 1 and N -> 1, N != 1)
524 WARN_ON(elem
->single
.func
!= __mark_empty_function
525 && elem
->single
.probe_private
526 != (*entry
)->single
.probe_private
&&
528 elem
->single
.probe_private
= (*entry
)->single
.probe_private
;
530 * Make sure the private data is valid when we update the
534 elem
->single
.func
= (*entry
)->single
.func
;
536 * We also make sure that the new probe callbacks array is consistent
537 * before setting a pointer to it.
539 rcu_assign_pointer(elem
->multi
, (*entry
)->multi
);
541 * Update the function or multi probe array pointer before setting the
545 elem
->ptype
= (*entry
)->ptype
;
546 elem
->state
= active
;
552 * Disable a marker and its probe callback.
553 * Note: only waiting an RCU period after setting elem->call to the empty
554 * function insures that the original callback is not used anymore. This insured
555 * by preempt_disable around the call site.
557 static void disable_marker(struct marker
*elem
)
559 /* leave "call" as is. It is known statically. */
561 elem
->single
.func
= __mark_empty_function
;
562 /* Update the function before setting the ptype */
564 elem
->ptype
= 0; /* single probe */
566 * Leave the private data and id there, because removal is racy and
567 * should be done only after an RCU period. These are never used until
568 * the next initialization anyway.
573 * marker_update_probe_range - Update a probe range
574 * @begin: beginning of the range
575 * @end: end of the range
577 * Updates the probe callback corresponding to a range of markers.
579 void marker_update_probe_range(struct marker
*begin
,
583 struct marker_entry
*mark_entry
;
585 mutex_lock(&markers_mutex
);
586 for (iter
= begin
; iter
< end
; iter
++) {
587 mark_entry
= get_marker(iter
->name
);
589 set_marker(&mark_entry
, iter
,
590 !!mark_entry
->refcount
);
592 * ignore error, continue
595 disable_marker(iter
);
598 mutex_unlock(&markers_mutex
);
602 * Update probes, removing the faulty probes.
604 * Internal callback only changed before the first probe is connected to it.
605 * Single probe private data can only be changed on 0 -> 1 and 2 -> 1
606 * transitions. All other transitions will leave the old private data valid.
607 * This makes the non-atomicity of the callback/private data updates valid.
609 * "special case" updates :
614 * Other updates all behave the same, just like the 2 -> 3 or 3 -> 2 updates.
615 * Site effect : marker_set_format may delete the marker entry (creating a
618 static void marker_update_probes(void)
620 /* Core kernel markers */
621 marker_update_probe_range(__start___markers
, __stop___markers
);
622 /* Markers in modules. */
623 module_update_markers();
627 * marker_probe_register - Connect a probe to a marker
629 * @format: format string
630 * @probe: probe handler
631 * @probe_private: probe private data
633 * private data must be a valid allocated memory address, or NULL.
634 * Returns 0 if ok, error value on error.
635 * The probe address must at least be aligned on the architecture pointer size.
637 int marker_probe_register(const char *name
, const char *format
,
638 marker_probe_func
*probe
, void *probe_private
)
640 struct marker_entry
*entry
;
642 struct marker_probe_closure
*old
;
644 mutex_lock(&markers_mutex
);
645 entry
= get_marker(name
);
647 entry
= add_marker(name
, format
);
649 ret
= PTR_ERR(entry
);
654 * If we detect that a call_rcu is pending for this marker,
655 * make sure it's executed now.
657 if (entry
->rcu_pending
)
659 old
= marker_entry_add_probe(entry
, probe
, probe_private
);
664 mutex_unlock(&markers_mutex
);
665 marker_update_probes(); /* may update entry */
666 mutex_lock(&markers_mutex
);
667 entry
= get_marker(name
);
670 entry
->rcu_pending
= 1;
671 /* write rcu_pending before calling the RCU callback */
673 call_rcu_sched(&entry
->rcu
, free_old_closure
);
675 mutex_unlock(&markers_mutex
);
678 EXPORT_SYMBOL_GPL(marker_probe_register
);
681 * marker_probe_unregister - Disconnect a probe from a marker
683 * @probe: probe function pointer
684 * @probe_private: probe private data
686 * Returns the private data given to marker_probe_register, or an ERR_PTR().
687 * We do not need to call a synchronize_sched to make sure the probes have
688 * finished running before doing a module unload, because the module unload
689 * itself uses stop_machine(), which insures that every preempt disabled section
692 int marker_probe_unregister(const char *name
,
693 marker_probe_func
*probe
, void *probe_private
)
695 struct marker_entry
*entry
;
696 struct marker_probe_closure
*old
;
699 mutex_lock(&markers_mutex
);
700 entry
= get_marker(name
);
703 if (entry
->rcu_pending
)
705 old
= marker_entry_remove_probe(entry
, probe
, probe_private
);
706 mutex_unlock(&markers_mutex
);
707 marker_update_probes(); /* may update entry */
708 mutex_lock(&markers_mutex
);
709 entry
= get_marker(name
);
713 entry
->rcu_pending
= 1;
714 /* write rcu_pending before calling the RCU callback */
716 call_rcu_sched(&entry
->rcu
, free_old_closure
);
717 remove_marker(name
); /* Ignore busy error message */
720 mutex_unlock(&markers_mutex
);
723 EXPORT_SYMBOL_GPL(marker_probe_unregister
);
725 static struct marker_entry
*
726 get_marker_from_private_data(marker_probe_func
*probe
, void *probe_private
)
728 struct marker_entry
*entry
;
730 struct hlist_head
*head
;
731 struct hlist_node
*node
;
733 for (i
= 0; i
< MARKER_TABLE_SIZE
; i
++) {
734 head
= &marker_table
[i
];
735 hlist_for_each_entry(entry
, node
, head
, hlist
) {
737 if (entry
->single
.func
== probe
738 && entry
->single
.probe_private
742 struct marker_probe_closure
*closure
;
743 closure
= entry
->multi
;
744 for (i
= 0; closure
[i
].func
; i
++) {
745 if (closure
[i
].func
== probe
&&
746 closure
[i
].probe_private
757 * marker_probe_unregister_private_data - Disconnect a probe from a marker
758 * @probe: probe function
759 * @probe_private: probe private data
761 * Unregister a probe by providing the registered private data.
762 * Only removes the first marker found in hash table.
763 * Return 0 on success or error value.
764 * We do not need to call a synchronize_sched to make sure the probes have
765 * finished running before doing a module unload, because the module unload
766 * itself uses stop_machine(), which insures that every preempt disabled section
769 int marker_probe_unregister_private_data(marker_probe_func
*probe
,
772 struct marker_entry
*entry
;
774 struct marker_probe_closure
*old
;
776 mutex_lock(&markers_mutex
);
777 entry
= get_marker_from_private_data(probe
, probe_private
);
782 if (entry
->rcu_pending
)
784 old
= marker_entry_remove_probe(entry
, NULL
, probe_private
);
785 mutex_unlock(&markers_mutex
);
786 marker_update_probes(); /* may update entry */
787 mutex_lock(&markers_mutex
);
788 entry
= get_marker_from_private_data(probe
, probe_private
);
791 entry
->rcu_pending
= 1;
792 /* write rcu_pending before calling the RCU callback */
794 call_rcu_sched(&entry
->rcu
, free_old_closure
);
795 remove_marker(entry
->name
); /* Ignore busy error message */
797 mutex_unlock(&markers_mutex
);
800 EXPORT_SYMBOL_GPL(marker_probe_unregister_private_data
);
803 * marker_get_private_data - Get a marker's probe private data
805 * @probe: probe to match
806 * @num: get the nth matching probe's private data
808 * Returns the nth private data pointer (starting from 0) matching, or an
810 * Returns the private data pointer, or an ERR_PTR.
811 * The private data pointer should _only_ be dereferenced if the caller is the
812 * owner of the data, or its content could vanish. This is mostly used to
813 * confirm that a caller is the owner of a registered probe.
815 void *marker_get_private_data(const char *name
, marker_probe_func
*probe
,
818 struct hlist_head
*head
;
819 struct hlist_node
*node
;
820 struct marker_entry
*e
;
821 size_t name_len
= strlen(name
) + 1;
822 u32 hash
= jhash(name
, name_len
-1, 0);
825 head
= &marker_table
[hash
& ((1 << MARKER_HASH_BITS
)-1)];
826 hlist_for_each_entry(e
, node
, head
, hlist
) {
827 if (!strcmp(name
, e
->name
)) {
829 if (num
== 0 && e
->single
.func
== probe
)
830 return e
->single
.probe_private
;
834 struct marker_probe_closure
*closure
;
837 for (i
= 0; closure
[i
].func
; i
++) {
838 if (closure
[i
].func
!= probe
)
841 return closure
[i
].probe_private
;
846 return ERR_PTR(-ENOENT
);
848 EXPORT_SYMBOL_GPL(marker_get_private_data
);