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1/*
2 * This program is free software; you can redistribute it and/or modify
3 * it under the terms of the GNU General Public License as published by
4 * the Free Software Foundation; either version 2 of the License, or
5 * (at your option) any later version.
6 *
7 * This program is distributed in the hope that it will be useful,
8 * but WITHOUT ANY WARRANTY; without even the implied warranty of
9 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
10 * GNU General Public License for more details.
11 *
12 * You should have received a copy of the GNU General Public License
13 * along with this program; if not, write to the Free Software
14 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
15 *
16 * Copyright (C) 2007 Alan Stern
17 * Copyright (C) IBM Corporation, 2009
18 * Copyright (C) 2009, Frederic Weisbecker <fweisbec@gmail.com>
19 *
20 * Thanks to Ingo Molnar for his many suggestions.
21 *
22 * Authors: Alan Stern <stern@rowland.harvard.edu>
23 * K.Prasad <prasad@linux.vnet.ibm.com>
24 * Frederic Weisbecker <fweisbec@gmail.com>
25 */
26
27/*
28 * HW_breakpoint: a unified kernel/user-space hardware breakpoint facility,
29 * using the CPU's debug registers.
30 * This file contains the arch-independent routines.
31 */
32
33#include <linux/irqflags.h>
34#include <linux/kallsyms.h>
35#include <linux/notifier.h>
36#include <linux/kprobes.h>
37#include <linux/kdebug.h>
38#include <linux/kernel.h>
39#include <linux/module.h>
40#include <linux/percpu.h>
41#include <linux/sched.h>
42#include <linux/init.h>
43#include <linux/slab.h>
44#include <linux/list.h>
45#include <linux/cpu.h>
46#include <linux/smp.h>
47
48#include <linux/hw_breakpoint.h>
49
50
51/*
52 * Constraints data
53 */
54
55/* Number of pinned cpu breakpoints in a cpu */
56static DEFINE_PER_CPU(unsigned int, nr_cpu_bp_pinned[TYPE_MAX]);
57
58/* Number of pinned task breakpoints in a cpu */
59static DEFINE_PER_CPU(unsigned int *, nr_task_bp_pinned[TYPE_MAX]);
60
61/* Number of non-pinned cpu/task breakpoints in a cpu */
62static DEFINE_PER_CPU(unsigned int, nr_bp_flexible[TYPE_MAX]);
63
64static int nr_slots[TYPE_MAX];
65
66/* Keep track of the breakpoints attached to tasks */
67static LIST_HEAD(bp_task_head);
68
69static int constraints_initialized;
70
71/* Gather the number of total pinned and un-pinned bp in a cpuset */
72struct bp_busy_slots {
73 unsigned int pinned;
74 unsigned int flexible;
75};
76
77/* Serialize accesses to the above constraints */
78static DEFINE_MUTEX(nr_bp_mutex);
79
80__weak int hw_breakpoint_weight(struct perf_event *bp)
81{
82 return 1;
83}
84
85static inline enum bp_type_idx find_slot_idx(struct perf_event *bp)
86{
87 if (bp->attr.bp_type & HW_BREAKPOINT_RW)
88 return TYPE_DATA;
89
90 return TYPE_INST;
91}
92
93/*
94 * Report the maximum number of pinned breakpoints a task
95 * have in this cpu
96 */
97static unsigned int max_task_bp_pinned(int cpu, enum bp_type_idx type)
98{
99 int i;
100 unsigned int *tsk_pinned = per_cpu(nr_task_bp_pinned[type], cpu);
101
102 for (i = nr_slots[type] - 1; i >= 0; i--) {
103 if (tsk_pinned[i] > 0)
104 return i + 1;
105 }
106
107 return 0;
108}
109
110/*
111 * Count the number of breakpoints of the same type and same task.
112 * The given event must be not on the list.
113 */
114static int task_bp_pinned(struct perf_event *bp, enum bp_type_idx type)
115{
116 struct task_struct *tsk = bp->hw.bp_target;
117 struct perf_event *iter;
118 int count = 0;
119
120 list_for_each_entry(iter, &bp_task_head, hw.bp_list) {
121 if (iter->hw.bp_target == tsk && find_slot_idx(iter) == type)
122 count += hw_breakpoint_weight(iter);
123 }
124
125 return count;
126}
127
128/*
129 * Report the number of pinned/un-pinned breakpoints we have in
130 * a given cpu (cpu > -1) or in all of them (cpu = -1).
131 */
132static void
133fetch_bp_busy_slots(struct bp_busy_slots *slots, struct perf_event *bp,
134 enum bp_type_idx type)
135{
136 int cpu = bp->cpu;
137 struct task_struct *tsk = bp->hw.bp_target;
138
139 if (cpu >= 0) {
140 slots->pinned = per_cpu(nr_cpu_bp_pinned[type], cpu);
141 if (!tsk)
142 slots->pinned += max_task_bp_pinned(cpu, type);
143 else
144 slots->pinned += task_bp_pinned(bp, type);
145 slots->flexible = per_cpu(nr_bp_flexible[type], cpu);
146
147 return;
148 }
149
150 for_each_online_cpu(cpu) {
151 unsigned int nr;
152
153 nr = per_cpu(nr_cpu_bp_pinned[type], cpu);
154 if (!tsk)
155 nr += max_task_bp_pinned(cpu, type);
156 else
157 nr += task_bp_pinned(bp, type);
158
159 if (nr > slots->pinned)
160 slots->pinned = nr;
161
162 nr = per_cpu(nr_bp_flexible[type], cpu);
163
164 if (nr > slots->flexible)
165 slots->flexible = nr;
166 }
167}
168
169/*
170 * For now, continue to consider flexible as pinned, until we can
171 * ensure no flexible event can ever be scheduled before a pinned event
172 * in a same cpu.
173 */
174static void
175fetch_this_slot(struct bp_busy_slots *slots, int weight)
176{
177 slots->pinned += weight;
178}
179
180/*
181 * Add a pinned breakpoint for the given task in our constraint table
182 */
183static void toggle_bp_task_slot(struct perf_event *bp, int cpu, bool enable,
184 enum bp_type_idx type, int weight)
185{
186 unsigned int *tsk_pinned;
187 int old_count = 0;
188 int old_idx = 0;
189 int idx = 0;
190
191 old_count = task_bp_pinned(bp, type);
192 old_idx = old_count - 1;
193 idx = old_idx + weight;
194
195 /* tsk_pinned[n] is the number of tasks having n breakpoints */
196 tsk_pinned = per_cpu(nr_task_bp_pinned[type], cpu);
197 if (enable) {
198 tsk_pinned[idx]++;
199 if (old_count > 0)
200 tsk_pinned[old_idx]--;
201 } else {
202 tsk_pinned[idx]--;
203 if (old_count > 0)
204 tsk_pinned[old_idx]++;
205 }
206}
207
208/*
209 * Add/remove the given breakpoint in our constraint table
210 */
211static void
212toggle_bp_slot(struct perf_event *bp, bool enable, enum bp_type_idx type,
213 int weight)
214{
215 int cpu = bp->cpu;
216 struct task_struct *tsk = bp->hw.bp_target;
217
218 /* Pinned counter cpu profiling */
219 if (!tsk) {
220
221 if (enable)
222 per_cpu(nr_cpu_bp_pinned[type], bp->cpu) += weight;
223 else
224 per_cpu(nr_cpu_bp_pinned[type], bp->cpu) -= weight;
225 return;
226 }
227
228 /* Pinned counter task profiling */
229
230 if (!enable)
231 list_del(&bp->hw.bp_list);
232
233 if (cpu >= 0) {
234 toggle_bp_task_slot(bp, cpu, enable, type, weight);
235 } else {
236 for_each_online_cpu(cpu)
237 toggle_bp_task_slot(bp, cpu, enable, type, weight);
238 }
239
240 if (enable)
241 list_add_tail(&bp->hw.bp_list, &bp_task_head);
242}
243
244/*
245 * Function to perform processor-specific cleanup during unregistration
246 */
247__weak void arch_unregister_hw_breakpoint(struct perf_event *bp)
248{
249 /*
250 * A weak stub function here for those archs that don't define
251 * it inside arch/.../kernel/hw_breakpoint.c
252 */
253}
254
255/*
256 * Contraints to check before allowing this new breakpoint counter:
257 *
258 * == Non-pinned counter == (Considered as pinned for now)
259 *
260 * - If attached to a single cpu, check:
261 *
262 * (per_cpu(nr_bp_flexible, cpu) || (per_cpu(nr_cpu_bp_pinned, cpu)
263 * + max(per_cpu(nr_task_bp_pinned, cpu)))) < HBP_NUM
264 *
265 * -> If there are already non-pinned counters in this cpu, it means
266 * there is already a free slot for them.
267 * Otherwise, we check that the maximum number of per task
268 * breakpoints (for this cpu) plus the number of per cpu breakpoint
269 * (for this cpu) doesn't cover every registers.
270 *
271 * - If attached to every cpus, check:
272 *
273 * (per_cpu(nr_bp_flexible, *) || (max(per_cpu(nr_cpu_bp_pinned, *))
274 * + max(per_cpu(nr_task_bp_pinned, *)))) < HBP_NUM
275 *
276 * -> This is roughly the same, except we check the number of per cpu
277 * bp for every cpu and we keep the max one. Same for the per tasks
278 * breakpoints.
279 *
280 *
281 * == Pinned counter ==
282 *
283 * - If attached to a single cpu, check:
284 *
285 * ((per_cpu(nr_bp_flexible, cpu) > 1) + per_cpu(nr_cpu_bp_pinned, cpu)
286 * + max(per_cpu(nr_task_bp_pinned, cpu))) < HBP_NUM
287 *
288 * -> Same checks as before. But now the nr_bp_flexible, if any, must keep
289 * one register at least (or they will never be fed).
290 *
291 * - If attached to every cpus, check:
292 *
293 * ((per_cpu(nr_bp_flexible, *) > 1) + max(per_cpu(nr_cpu_bp_pinned, *))
294 * + max(per_cpu(nr_task_bp_pinned, *))) < HBP_NUM
295 */
296static int __reserve_bp_slot(struct perf_event *bp)
297{
298 struct bp_busy_slots slots = {0};
299 enum bp_type_idx type;
300 int weight;
301
302 /* We couldn't initialize breakpoint constraints on boot */
303 if (!constraints_initialized)
304 return -ENOMEM;
305
306 /* Basic checks */
307 if (bp->attr.bp_type == HW_BREAKPOINT_EMPTY ||
308 bp->attr.bp_type == HW_BREAKPOINT_INVALID)
309 return -EINVAL;
310
311 type = find_slot_idx(bp);
312 weight = hw_breakpoint_weight(bp);
313
314 fetch_bp_busy_slots(&slots, bp, type);
315 /*
316 * Simulate the addition of this breakpoint to the constraints
317 * and see the result.
318 */
319 fetch_this_slot(&slots, weight);
320
321 /* Flexible counters need to keep at least one slot */
322 if (slots.pinned + (!!slots.flexible) > nr_slots[type])
323 return -ENOSPC;
324
325 toggle_bp_slot(bp, true, type, weight);
326
327 return 0;
328}
329
330int reserve_bp_slot(struct perf_event *bp)
331{
332 int ret;
333
334 mutex_lock(&nr_bp_mutex);
335
336 ret = __reserve_bp_slot(bp);
337
338 mutex_unlock(&nr_bp_mutex);
339
340 return ret;
341}
342
343static void __release_bp_slot(struct perf_event *bp)
344{
345 enum bp_type_idx type;
346 int weight;
347
348 type = find_slot_idx(bp);
349 weight = hw_breakpoint_weight(bp);
350 toggle_bp_slot(bp, false, type, weight);
351}
352
353void release_bp_slot(struct perf_event *bp)
354{
355 mutex_lock(&nr_bp_mutex);
356
357 arch_unregister_hw_breakpoint(bp);
358 __release_bp_slot(bp);
359
360 mutex_unlock(&nr_bp_mutex);
361}
362
363/*
364 * Allow the kernel debugger to reserve breakpoint slots without
365 * taking a lock using the dbg_* variant of for the reserve and
366 * release breakpoint slots.
367 */
368int dbg_reserve_bp_slot(struct perf_event *bp)
369{
370 if (mutex_is_locked(&nr_bp_mutex))
371 return -1;
372
373 return __reserve_bp_slot(bp);
374}
375
376int dbg_release_bp_slot(struct perf_event *bp)
377{
378 if (mutex_is_locked(&nr_bp_mutex))
379 return -1;
380
381 __release_bp_slot(bp);
382
383 return 0;
384}
385
386static int validate_hw_breakpoint(struct perf_event *bp)
387{
388 int ret;
389
390 ret = arch_validate_hwbkpt_settings(bp);
391 if (ret)
392 return ret;
393
394 if (arch_check_bp_in_kernelspace(bp)) {
395 if (bp->attr.exclude_kernel)
396 return -EINVAL;
397 /*
398 * Don't let unprivileged users set a breakpoint in the trap
399 * path to avoid trap recursion attacks.
400 */
401 if (!capable(CAP_SYS_ADMIN))
402 return -EPERM;
403 }
404
405 return 0;
406}
407
408int register_perf_hw_breakpoint(struct perf_event *bp)
409{
410 int ret;
411
412 ret = reserve_bp_slot(bp);
413 if (ret)
414 return ret;
415
416 ret = validate_hw_breakpoint(bp);
417
418 /* if arch_validate_hwbkpt_settings() fails then release bp slot */
419 if (ret)
420 release_bp_slot(bp);
421
422 return ret;
423}
424
425/**
426 * register_user_hw_breakpoint - register a hardware breakpoint for user space
427 * @attr: breakpoint attributes
428 * @triggered: callback to trigger when we hit the breakpoint
429 * @tsk: pointer to 'task_struct' of the process to which the address belongs
430 */
431struct perf_event *
432register_user_hw_breakpoint(struct perf_event_attr *attr,
433 perf_overflow_handler_t triggered,
434 void *context,
435 struct task_struct *tsk)
436{
437 return perf_event_create_kernel_counter(attr, -1, tsk, triggered,
438 context);
439}
440EXPORT_SYMBOL_GPL(register_user_hw_breakpoint);
441
442/**
443 * modify_user_hw_breakpoint - modify a user-space hardware breakpoint
444 * @bp: the breakpoint structure to modify
445 * @attr: new breakpoint attributes
446 * @triggered: callback to trigger when we hit the breakpoint
447 * @tsk: pointer to 'task_struct' of the process to which the address belongs
448 */
449int modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *attr)
450{
451 u64 old_addr = bp->attr.bp_addr;
452 u64 old_len = bp->attr.bp_len;
453 int old_type = bp->attr.bp_type;
454 int err = 0;
455
456 perf_event_disable(bp);
457
458 bp->attr.bp_addr = attr->bp_addr;
459 bp->attr.bp_type = attr->bp_type;
460 bp->attr.bp_len = attr->bp_len;
461
462 if (attr->disabled)
463 goto end;
464
465 err = validate_hw_breakpoint(bp);
466 if (!err)
467 perf_event_enable(bp);
468
469 if (err) {
470 bp->attr.bp_addr = old_addr;
471 bp->attr.bp_type = old_type;
472 bp->attr.bp_len = old_len;
473 if (!bp->attr.disabled)
474 perf_event_enable(bp);
475
476 return err;
477 }
478
479end:
480 bp->attr.disabled = attr->disabled;
481
482 return 0;
483}
484EXPORT_SYMBOL_GPL(modify_user_hw_breakpoint);
485
486/**
487 * unregister_hw_breakpoint - unregister a user-space hardware breakpoint
488 * @bp: the breakpoint structure to unregister
489 */
490void unregister_hw_breakpoint(struct perf_event *bp)
491{
492 if (!bp)
493 return;
494 perf_event_release_kernel(bp);
495}
496EXPORT_SYMBOL_GPL(unregister_hw_breakpoint);
497
498/**
499 * register_wide_hw_breakpoint - register a wide breakpoint in the kernel
500 * @attr: breakpoint attributes
501 * @triggered: callback to trigger when we hit the breakpoint
502 *
503 * @return a set of per_cpu pointers to perf events
504 */
505struct perf_event * __percpu *
506register_wide_hw_breakpoint(struct perf_event_attr *attr,
507 perf_overflow_handler_t triggered,
508 void *context)
509{
510 struct perf_event * __percpu *cpu_events, **pevent, *bp;
511 long err;
512 int cpu;
513
514 cpu_events = alloc_percpu(typeof(*cpu_events));
515 if (!cpu_events)
516 return (void __percpu __force *)ERR_PTR(-ENOMEM);
517
518 get_online_cpus();
519 for_each_online_cpu(cpu) {
520 pevent = per_cpu_ptr(cpu_events, cpu);
521 bp = perf_event_create_kernel_counter(attr, cpu, NULL,
522 triggered, context);
523
524 *pevent = bp;
525
526 if (IS_ERR(bp)) {
527 err = PTR_ERR(bp);
528 goto fail;
529 }
530 }
531 put_online_cpus();
532
533 return cpu_events;
534
535fail:
536 for_each_online_cpu(cpu) {
537 pevent = per_cpu_ptr(cpu_events, cpu);
538 if (IS_ERR(*pevent))
539 break;
540 unregister_hw_breakpoint(*pevent);
541 }
542 put_online_cpus();
543
544 free_percpu(cpu_events);
545 return (void __percpu __force *)ERR_PTR(err);
546}
547EXPORT_SYMBOL_GPL(register_wide_hw_breakpoint);
548
549/**
550 * unregister_wide_hw_breakpoint - unregister a wide breakpoint in the kernel
551 * @cpu_events: the per cpu set of events to unregister
552 */
553void unregister_wide_hw_breakpoint(struct perf_event * __percpu *cpu_events)
554{
555 int cpu;
556 struct perf_event **pevent;
557
558 for_each_possible_cpu(cpu) {
559 pevent = per_cpu_ptr(cpu_events, cpu);
560 unregister_hw_breakpoint(*pevent);
561 }
562 free_percpu(cpu_events);
563}
564EXPORT_SYMBOL_GPL(unregister_wide_hw_breakpoint);
565
566static struct notifier_block hw_breakpoint_exceptions_nb = {
567 .notifier_call = hw_breakpoint_exceptions_notify,
568 /* we need to be notified first */
569 .priority = 0x7fffffff
570};
571
572static void bp_perf_event_destroy(struct perf_event *event)
573{
574 release_bp_slot(event);
575}
576
577static int hw_breakpoint_event_init(struct perf_event *bp)
578{
579 int err;
580
581 if (bp->attr.type != PERF_TYPE_BREAKPOINT)
582 return -ENOENT;
583
584 /*
585 * no branch sampling for breakpoint events
586 */
587 if (has_branch_stack(bp))
588 return -EOPNOTSUPP;
589
590 err = register_perf_hw_breakpoint(bp);
591 if (err)
592 return err;
593
594 bp->destroy = bp_perf_event_destroy;
595
596 return 0;
597}
598
599static int hw_breakpoint_add(struct perf_event *bp, int flags)
600{
601 if (!(flags & PERF_EF_START))
602 bp->hw.state = PERF_HES_STOPPED;
603
604 return arch_install_hw_breakpoint(bp);
605}
606
607static void hw_breakpoint_del(struct perf_event *bp, int flags)
608{
609 arch_uninstall_hw_breakpoint(bp);
610}
611
612static void hw_breakpoint_start(struct perf_event *bp, int flags)
613{
614 bp->hw.state = 0;
615}
616
617static void hw_breakpoint_stop(struct perf_event *bp, int flags)
618{
619 bp->hw.state = PERF_HES_STOPPED;
620}
621
622static int hw_breakpoint_event_idx(struct perf_event *bp)
623{
624 return 0;
625}
626
627static struct pmu perf_breakpoint = {
628 .task_ctx_nr = perf_sw_context, /* could eventually get its own */
629
630 .event_init = hw_breakpoint_event_init,
631 .add = hw_breakpoint_add,
632 .del = hw_breakpoint_del,
633 .start = hw_breakpoint_start,
634 .stop = hw_breakpoint_stop,
635 .read = hw_breakpoint_pmu_read,
636
637 .event_idx = hw_breakpoint_event_idx,
638};
639
640int __init init_hw_breakpoint(void)
641{
642 unsigned int **task_bp_pinned;
643 int cpu, err_cpu;
644 int i;
645
646 for (i = 0; i < TYPE_MAX; i++)
647 nr_slots[i] = hw_breakpoint_slots(i);
648
649 for_each_possible_cpu(cpu) {
650 for (i = 0; i < TYPE_MAX; i++) {
651 task_bp_pinned = &per_cpu(nr_task_bp_pinned[i], cpu);
652 *task_bp_pinned = kzalloc(sizeof(int) * nr_slots[i],
653 GFP_KERNEL);
654 if (!*task_bp_pinned)
655 goto err_alloc;
656 }
657 }
658
659 constraints_initialized = 1;
660
661 perf_pmu_register(&perf_breakpoint, "breakpoint", PERF_TYPE_BREAKPOINT);
662
663 return register_die_notifier(&hw_breakpoint_exceptions_nb);
664
665 err_alloc:
666 for_each_possible_cpu(err_cpu) {
667 for (i = 0; i < TYPE_MAX; i++)
668 kfree(per_cpu(nr_task_bp_pinned[i], cpu));
669 if (err_cpu == cpu)
670 break;
671 }
672
673 return -ENOMEM;
674}
675
676
1// SPDX-License-Identifier: GPL-2.0+
2/*
3 * Copyright (C) 2007 Alan Stern
4 * Copyright (C) IBM Corporation, 2009
5 * Copyright (C) 2009, Frederic Weisbecker <fweisbec@gmail.com>
6 *
7 * Thanks to Ingo Molnar for his many suggestions.
8 *
9 * Authors: Alan Stern <stern@rowland.harvard.edu>
10 * K.Prasad <prasad@linux.vnet.ibm.com>
11 * Frederic Weisbecker <fweisbec@gmail.com>
12 */
13
14/*
15 * HW_breakpoint: a unified kernel/user-space hardware breakpoint facility,
16 * using the CPU's debug registers.
17 * This file contains the arch-independent routines.
18 */
19
20#include <linux/irqflags.h>
21#include <linux/kallsyms.h>
22#include <linux/notifier.h>
23#include <linux/kprobes.h>
24#include <linux/kdebug.h>
25#include <linux/kernel.h>
26#include <linux/module.h>
27#include <linux/percpu.h>
28#include <linux/sched.h>
29#include <linux/init.h>
30#include <linux/slab.h>
31#include <linux/list.h>
32#include <linux/cpu.h>
33#include <linux/smp.h>
34#include <linux/bug.h>
35
36#include <linux/hw_breakpoint.h>
37/*
38 * Constraints data
39 */
40struct bp_cpuinfo {
41 /* Number of pinned cpu breakpoints in a cpu */
42 unsigned int cpu_pinned;
43 /* tsk_pinned[n] is the number of tasks having n+1 breakpoints */
44 unsigned int *tsk_pinned;
45 /* Number of non-pinned cpu/task breakpoints in a cpu */
46 unsigned int flexible; /* XXX: placeholder, see fetch_this_slot() */
47};
48
49static DEFINE_PER_CPU(struct bp_cpuinfo, bp_cpuinfo[TYPE_MAX]);
50static int nr_slots[TYPE_MAX];
51
52static struct bp_cpuinfo *get_bp_info(int cpu, enum bp_type_idx type)
53{
54 return per_cpu_ptr(bp_cpuinfo + type, cpu);
55}
56
57/* Keep track of the breakpoints attached to tasks */
58static LIST_HEAD(bp_task_head);
59
60static int constraints_initialized;
61
62/* Gather the number of total pinned and un-pinned bp in a cpuset */
63struct bp_busy_slots {
64 unsigned int pinned;
65 unsigned int flexible;
66};
67
68/* Serialize accesses to the above constraints */
69static DEFINE_MUTEX(nr_bp_mutex);
70
71__weak int hw_breakpoint_weight(struct perf_event *bp)
72{
73 return 1;
74}
75
76static inline enum bp_type_idx find_slot_idx(u64 bp_type)
77{
78 if (bp_type & HW_BREAKPOINT_RW)
79 return TYPE_DATA;
80
81 return TYPE_INST;
82}
83
84/*
85 * Report the maximum number of pinned breakpoints a task
86 * have in this cpu
87 */
88static unsigned int max_task_bp_pinned(int cpu, enum bp_type_idx type)
89{
90 unsigned int *tsk_pinned = get_bp_info(cpu, type)->tsk_pinned;
91 int i;
92
93 for (i = nr_slots[type] - 1; i >= 0; i--) {
94 if (tsk_pinned[i] > 0)
95 return i + 1;
96 }
97
98 return 0;
99}
100
101/*
102 * Count the number of breakpoints of the same type and same task.
103 * The given event must be not on the list.
104 */
105static int task_bp_pinned(int cpu, struct perf_event *bp, enum bp_type_idx type)
106{
107 struct task_struct *tsk = bp->hw.target;
108 struct perf_event *iter;
109 int count = 0;
110
111 list_for_each_entry(iter, &bp_task_head, hw.bp_list) {
112 if (iter->hw.target == tsk &&
113 find_slot_idx(iter->attr.bp_type) == type &&
114 (iter->cpu < 0 || cpu == iter->cpu))
115 count += hw_breakpoint_weight(iter);
116 }
117
118 return count;
119}
120
121static const struct cpumask *cpumask_of_bp(struct perf_event *bp)
122{
123 if (bp->cpu >= 0)
124 return cpumask_of(bp->cpu);
125 return cpu_possible_mask;
126}
127
128/*
129 * Report the number of pinned/un-pinned breakpoints we have in
130 * a given cpu (cpu > -1) or in all of them (cpu = -1).
131 */
132static void
133fetch_bp_busy_slots(struct bp_busy_slots *slots, struct perf_event *bp,
134 enum bp_type_idx type)
135{
136 const struct cpumask *cpumask = cpumask_of_bp(bp);
137 int cpu;
138
139 for_each_cpu(cpu, cpumask) {
140 struct bp_cpuinfo *info = get_bp_info(cpu, type);
141 int nr;
142
143 nr = info->cpu_pinned;
144 if (!bp->hw.target)
145 nr += max_task_bp_pinned(cpu, type);
146 else
147 nr += task_bp_pinned(cpu, bp, type);
148
149 if (nr > slots->pinned)
150 slots->pinned = nr;
151
152 nr = info->flexible;
153 if (nr > slots->flexible)
154 slots->flexible = nr;
155 }
156}
157
158/*
159 * For now, continue to consider flexible as pinned, until we can
160 * ensure no flexible event can ever be scheduled before a pinned event
161 * in a same cpu.
162 */
163static void
164fetch_this_slot(struct bp_busy_slots *slots, int weight)
165{
166 slots->pinned += weight;
167}
168
169/*
170 * Add a pinned breakpoint for the given task in our constraint table
171 */
172static void toggle_bp_task_slot(struct perf_event *bp, int cpu,
173 enum bp_type_idx type, int weight)
174{
175 unsigned int *tsk_pinned = get_bp_info(cpu, type)->tsk_pinned;
176 int old_idx, new_idx;
177
178 old_idx = task_bp_pinned(cpu, bp, type) - 1;
179 new_idx = old_idx + weight;
180
181 if (old_idx >= 0)
182 tsk_pinned[old_idx]--;
183 if (new_idx >= 0)
184 tsk_pinned[new_idx]++;
185}
186
187/*
188 * Add/remove the given breakpoint in our constraint table
189 */
190static void
191toggle_bp_slot(struct perf_event *bp, bool enable, enum bp_type_idx type,
192 int weight)
193{
194 const struct cpumask *cpumask = cpumask_of_bp(bp);
195 int cpu;
196
197 if (!enable)
198 weight = -weight;
199
200 /* Pinned counter cpu profiling */
201 if (!bp->hw.target) {
202 get_bp_info(bp->cpu, type)->cpu_pinned += weight;
203 return;
204 }
205
206 /* Pinned counter task profiling */
207 for_each_cpu(cpu, cpumask)
208 toggle_bp_task_slot(bp, cpu, type, weight);
209
210 if (enable)
211 list_add_tail(&bp->hw.bp_list, &bp_task_head);
212 else
213 list_del(&bp->hw.bp_list);
214}
215
216__weak int arch_reserve_bp_slot(struct perf_event *bp)
217{
218 return 0;
219}
220
221__weak void arch_release_bp_slot(struct perf_event *bp)
222{
223}
224
225/*
226 * Function to perform processor-specific cleanup during unregistration
227 */
228__weak void arch_unregister_hw_breakpoint(struct perf_event *bp)
229{
230 /*
231 * A weak stub function here for those archs that don't define
232 * it inside arch/.../kernel/hw_breakpoint.c
233 */
234}
235
236/*
237 * Constraints to check before allowing this new breakpoint counter:
238 *
239 * == Non-pinned counter == (Considered as pinned for now)
240 *
241 * - If attached to a single cpu, check:
242 *
243 * (per_cpu(info->flexible, cpu) || (per_cpu(info->cpu_pinned, cpu)
244 * + max(per_cpu(info->tsk_pinned, cpu)))) < HBP_NUM
245 *
246 * -> If there are already non-pinned counters in this cpu, it means
247 * there is already a free slot for them.
248 * Otherwise, we check that the maximum number of per task
249 * breakpoints (for this cpu) plus the number of per cpu breakpoint
250 * (for this cpu) doesn't cover every registers.
251 *
252 * - If attached to every cpus, check:
253 *
254 * (per_cpu(info->flexible, *) || (max(per_cpu(info->cpu_pinned, *))
255 * + max(per_cpu(info->tsk_pinned, *)))) < HBP_NUM
256 *
257 * -> This is roughly the same, except we check the number of per cpu
258 * bp for every cpu and we keep the max one. Same for the per tasks
259 * breakpoints.
260 *
261 *
262 * == Pinned counter ==
263 *
264 * - If attached to a single cpu, check:
265 *
266 * ((per_cpu(info->flexible, cpu) > 1) + per_cpu(info->cpu_pinned, cpu)
267 * + max(per_cpu(info->tsk_pinned, cpu))) < HBP_NUM
268 *
269 * -> Same checks as before. But now the info->flexible, if any, must keep
270 * one register at least (or they will never be fed).
271 *
272 * - If attached to every cpus, check:
273 *
274 * ((per_cpu(info->flexible, *) > 1) + max(per_cpu(info->cpu_pinned, *))
275 * + max(per_cpu(info->tsk_pinned, *))) < HBP_NUM
276 */
277static int __reserve_bp_slot(struct perf_event *bp, u64 bp_type)
278{
279 struct bp_busy_slots slots = {0};
280 enum bp_type_idx type;
281 int weight;
282 int ret;
283
284 /* We couldn't initialize breakpoint constraints on boot */
285 if (!constraints_initialized)
286 return -ENOMEM;
287
288 /* Basic checks */
289 if (bp_type == HW_BREAKPOINT_EMPTY ||
290 bp_type == HW_BREAKPOINT_INVALID)
291 return -EINVAL;
292
293 type = find_slot_idx(bp_type);
294 weight = hw_breakpoint_weight(bp);
295
296 fetch_bp_busy_slots(&slots, bp, type);
297 /*
298 * Simulate the addition of this breakpoint to the constraints
299 * and see the result.
300 */
301 fetch_this_slot(&slots, weight);
302
303 /* Flexible counters need to keep at least one slot */
304 if (slots.pinned + (!!slots.flexible) > nr_slots[type])
305 return -ENOSPC;
306
307 ret = arch_reserve_bp_slot(bp);
308 if (ret)
309 return ret;
310
311 toggle_bp_slot(bp, true, type, weight);
312
313 return 0;
314}
315
316int reserve_bp_slot(struct perf_event *bp)
317{
318 int ret;
319
320 mutex_lock(&nr_bp_mutex);
321
322 ret = __reserve_bp_slot(bp, bp->attr.bp_type);
323
324 mutex_unlock(&nr_bp_mutex);
325
326 return ret;
327}
328
329static void __release_bp_slot(struct perf_event *bp, u64 bp_type)
330{
331 enum bp_type_idx type;
332 int weight;
333
334 arch_release_bp_slot(bp);
335
336 type = find_slot_idx(bp_type);
337 weight = hw_breakpoint_weight(bp);
338 toggle_bp_slot(bp, false, type, weight);
339}
340
341void release_bp_slot(struct perf_event *bp)
342{
343 mutex_lock(&nr_bp_mutex);
344
345 arch_unregister_hw_breakpoint(bp);
346 __release_bp_slot(bp, bp->attr.bp_type);
347
348 mutex_unlock(&nr_bp_mutex);
349}
350
351static int __modify_bp_slot(struct perf_event *bp, u64 old_type, u64 new_type)
352{
353 int err;
354
355 __release_bp_slot(bp, old_type);
356
357 err = __reserve_bp_slot(bp, new_type);
358 if (err) {
359 /*
360 * Reserve the old_type slot back in case
361 * there's no space for the new type.
362 *
363 * This must succeed, because we just released
364 * the old_type slot in the __release_bp_slot
365 * call above. If not, something is broken.
366 */
367 WARN_ON(__reserve_bp_slot(bp, old_type));
368 }
369
370 return err;
371}
372
373static int modify_bp_slot(struct perf_event *bp, u64 old_type, u64 new_type)
374{
375 int ret;
376
377 mutex_lock(&nr_bp_mutex);
378 ret = __modify_bp_slot(bp, old_type, new_type);
379 mutex_unlock(&nr_bp_mutex);
380 return ret;
381}
382
383/*
384 * Allow the kernel debugger to reserve breakpoint slots without
385 * taking a lock using the dbg_* variant of for the reserve and
386 * release breakpoint slots.
387 */
388int dbg_reserve_bp_slot(struct perf_event *bp)
389{
390 if (mutex_is_locked(&nr_bp_mutex))
391 return -1;
392
393 return __reserve_bp_slot(bp, bp->attr.bp_type);
394}
395
396int dbg_release_bp_slot(struct perf_event *bp)
397{
398 if (mutex_is_locked(&nr_bp_mutex))
399 return -1;
400
401 __release_bp_slot(bp, bp->attr.bp_type);
402
403 return 0;
404}
405
406static int hw_breakpoint_parse(struct perf_event *bp,
407 const struct perf_event_attr *attr,
408 struct arch_hw_breakpoint *hw)
409{
410 int err;
411
412 err = hw_breakpoint_arch_parse(bp, attr, hw);
413 if (err)
414 return err;
415
416 if (arch_check_bp_in_kernelspace(hw)) {
417 if (attr->exclude_kernel)
418 return -EINVAL;
419 /*
420 * Don't let unprivileged users set a breakpoint in the trap
421 * path to avoid trap recursion attacks.
422 */
423 if (!capable(CAP_SYS_ADMIN))
424 return -EPERM;
425 }
426
427 return 0;
428}
429
430int register_perf_hw_breakpoint(struct perf_event *bp)
431{
432 struct arch_hw_breakpoint hw = { };
433 int err;
434
435 err = reserve_bp_slot(bp);
436 if (err)
437 return err;
438
439 err = hw_breakpoint_parse(bp, &bp->attr, &hw);
440 if (err) {
441 release_bp_slot(bp);
442 return err;
443 }
444
445 bp->hw.info = hw;
446
447 return 0;
448}
449
450/**
451 * register_user_hw_breakpoint - register a hardware breakpoint for user space
452 * @attr: breakpoint attributes
453 * @triggered: callback to trigger when we hit the breakpoint
454 * @tsk: pointer to 'task_struct' of the process to which the address belongs
455 */
456struct perf_event *
457register_user_hw_breakpoint(struct perf_event_attr *attr,
458 perf_overflow_handler_t triggered,
459 void *context,
460 struct task_struct *tsk)
461{
462 return perf_event_create_kernel_counter(attr, -1, tsk, triggered,
463 context);
464}
465EXPORT_SYMBOL_GPL(register_user_hw_breakpoint);
466
467static void hw_breakpoint_copy_attr(struct perf_event_attr *to,
468 struct perf_event_attr *from)
469{
470 to->bp_addr = from->bp_addr;
471 to->bp_type = from->bp_type;
472 to->bp_len = from->bp_len;
473 to->disabled = from->disabled;
474}
475
476int
477modify_user_hw_breakpoint_check(struct perf_event *bp, struct perf_event_attr *attr,
478 bool check)
479{
480 struct arch_hw_breakpoint hw = { };
481 int err;
482
483 err = hw_breakpoint_parse(bp, attr, &hw);
484 if (err)
485 return err;
486
487 if (check) {
488 struct perf_event_attr old_attr;
489
490 old_attr = bp->attr;
491 hw_breakpoint_copy_attr(&old_attr, attr);
492 if (memcmp(&old_attr, attr, sizeof(*attr)))
493 return -EINVAL;
494 }
495
496 if (bp->attr.bp_type != attr->bp_type) {
497 err = modify_bp_slot(bp, bp->attr.bp_type, attr->bp_type);
498 if (err)
499 return err;
500 }
501
502 hw_breakpoint_copy_attr(&bp->attr, attr);
503 bp->hw.info = hw;
504
505 return 0;
506}
507
508/**
509 * modify_user_hw_breakpoint - modify a user-space hardware breakpoint
510 * @bp: the breakpoint structure to modify
511 * @attr: new breakpoint attributes
512 */
513int modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *attr)
514{
515 int err;
516
517 /*
518 * modify_user_hw_breakpoint can be invoked with IRQs disabled and hence it
519 * will not be possible to raise IPIs that invoke __perf_event_disable.
520 * So call the function directly after making sure we are targeting the
521 * current task.
522 */
523 if (irqs_disabled() && bp->ctx && bp->ctx->task == current)
524 perf_event_disable_local(bp);
525 else
526 perf_event_disable(bp);
527
528 err = modify_user_hw_breakpoint_check(bp, attr, false);
529
530 if (!bp->attr.disabled)
531 perf_event_enable(bp);
532
533 return err;
534}
535EXPORT_SYMBOL_GPL(modify_user_hw_breakpoint);
536
537/**
538 * unregister_hw_breakpoint - unregister a user-space hardware breakpoint
539 * @bp: the breakpoint structure to unregister
540 */
541void unregister_hw_breakpoint(struct perf_event *bp)
542{
543 if (!bp)
544 return;
545 perf_event_release_kernel(bp);
546}
547EXPORT_SYMBOL_GPL(unregister_hw_breakpoint);
548
549/**
550 * register_wide_hw_breakpoint - register a wide breakpoint in the kernel
551 * @attr: breakpoint attributes
552 * @triggered: callback to trigger when we hit the breakpoint
553 *
554 * @return a set of per_cpu pointers to perf events
555 */
556struct perf_event * __percpu *
557register_wide_hw_breakpoint(struct perf_event_attr *attr,
558 perf_overflow_handler_t triggered,
559 void *context)
560{
561 struct perf_event * __percpu *cpu_events, *bp;
562 long err = 0;
563 int cpu;
564
565 cpu_events = alloc_percpu(typeof(*cpu_events));
566 if (!cpu_events)
567 return (void __percpu __force *)ERR_PTR(-ENOMEM);
568
569 get_online_cpus();
570 for_each_online_cpu(cpu) {
571 bp = perf_event_create_kernel_counter(attr, cpu, NULL,
572 triggered, context);
573 if (IS_ERR(bp)) {
574 err = PTR_ERR(bp);
575 break;
576 }
577
578 per_cpu(*cpu_events, cpu) = bp;
579 }
580 put_online_cpus();
581
582 if (likely(!err))
583 return cpu_events;
584
585 unregister_wide_hw_breakpoint(cpu_events);
586 return (void __percpu __force *)ERR_PTR(err);
587}
588EXPORT_SYMBOL_GPL(register_wide_hw_breakpoint);
589
590/**
591 * unregister_wide_hw_breakpoint - unregister a wide breakpoint in the kernel
592 * @cpu_events: the per cpu set of events to unregister
593 */
594void unregister_wide_hw_breakpoint(struct perf_event * __percpu *cpu_events)
595{
596 int cpu;
597
598 for_each_possible_cpu(cpu)
599 unregister_hw_breakpoint(per_cpu(*cpu_events, cpu));
600
601 free_percpu(cpu_events);
602}
603EXPORT_SYMBOL_GPL(unregister_wide_hw_breakpoint);
604
605static struct notifier_block hw_breakpoint_exceptions_nb = {
606 .notifier_call = hw_breakpoint_exceptions_notify,
607 /* we need to be notified first */
608 .priority = 0x7fffffff
609};
610
611static void bp_perf_event_destroy(struct perf_event *event)
612{
613 release_bp_slot(event);
614}
615
616static int hw_breakpoint_event_init(struct perf_event *bp)
617{
618 int err;
619
620 if (bp->attr.type != PERF_TYPE_BREAKPOINT)
621 return -ENOENT;
622
623 /*
624 * no branch sampling for breakpoint events
625 */
626 if (has_branch_stack(bp))
627 return -EOPNOTSUPP;
628
629 err = register_perf_hw_breakpoint(bp);
630 if (err)
631 return err;
632
633 bp->destroy = bp_perf_event_destroy;
634
635 return 0;
636}
637
638static int hw_breakpoint_add(struct perf_event *bp, int flags)
639{
640 if (!(flags & PERF_EF_START))
641 bp->hw.state = PERF_HES_STOPPED;
642
643 if (is_sampling_event(bp)) {
644 bp->hw.last_period = bp->hw.sample_period;
645 perf_swevent_set_period(bp);
646 }
647
648 return arch_install_hw_breakpoint(bp);
649}
650
651static void hw_breakpoint_del(struct perf_event *bp, int flags)
652{
653 arch_uninstall_hw_breakpoint(bp);
654}
655
656static void hw_breakpoint_start(struct perf_event *bp, int flags)
657{
658 bp->hw.state = 0;
659}
660
661static void hw_breakpoint_stop(struct perf_event *bp, int flags)
662{
663 bp->hw.state = PERF_HES_STOPPED;
664}
665
666static struct pmu perf_breakpoint = {
667 .task_ctx_nr = perf_sw_context, /* could eventually get its own */
668
669 .event_init = hw_breakpoint_event_init,
670 .add = hw_breakpoint_add,
671 .del = hw_breakpoint_del,
672 .start = hw_breakpoint_start,
673 .stop = hw_breakpoint_stop,
674 .read = hw_breakpoint_pmu_read,
675};
676
677int __init init_hw_breakpoint(void)
678{
679 int cpu, err_cpu;
680 int i;
681
682 for (i = 0; i < TYPE_MAX; i++)
683 nr_slots[i] = hw_breakpoint_slots(i);
684
685 for_each_possible_cpu(cpu) {
686 for (i = 0; i < TYPE_MAX; i++) {
687 struct bp_cpuinfo *info = get_bp_info(cpu, i);
688
689 info->tsk_pinned = kcalloc(nr_slots[i], sizeof(int),
690 GFP_KERNEL);
691 if (!info->tsk_pinned)
692 goto err_alloc;
693 }
694 }
695
696 constraints_initialized = 1;
697
698 perf_pmu_register(&perf_breakpoint, "breakpoint", PERF_TYPE_BREAKPOINT);
699
700 return register_die_notifier(&hw_breakpoint_exceptions_nb);
701
702 err_alloc:
703 for_each_possible_cpu(err_cpu) {
704 for (i = 0; i < TYPE_MAX; i++)
705 kfree(get_bp_info(err_cpu, i)->tsk_pinned);
706 if (err_cpu == cpu)
707 break;
708 }
709
710 return -ENOMEM;
711}
712
713