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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/hw_breakpoint.h>
21
22#include <linux/atomic.h>
23#include <linux/bug.h>
24#include <linux/cpu.h>
25#include <linux/export.h>
26#include <linux/init.h>
27#include <linux/irqflags.h>
28#include <linux/kdebug.h>
29#include <linux/kernel.h>
30#include <linux/mutex.h>
31#include <linux/notifier.h>
32#include <linux/percpu-rwsem.h>
33#include <linux/percpu.h>
34#include <linux/rhashtable.h>
35#include <linux/sched.h>
36#include <linux/slab.h>
37
38/*
39 * Datastructure to track the total uses of N slots across tasks or CPUs;
40 * bp_slots_histogram::count[N] is the number of assigned N+1 breakpoint slots.
41 */
42struct bp_slots_histogram {
43#ifdef hw_breakpoint_slots
44 atomic_t count[hw_breakpoint_slots(0)];
45#else
46 atomic_t *count;
47#endif
48};
49
50/*
51 * Per-CPU constraints data.
52 */
53struct bp_cpuinfo {
54 /* Number of pinned CPU breakpoints in a CPU. */
55 unsigned int cpu_pinned;
56 /* Histogram of pinned task breakpoints in a CPU. */
57 struct bp_slots_histogram tsk_pinned;
58};
59
60static DEFINE_PER_CPU(struct bp_cpuinfo, bp_cpuinfo[TYPE_MAX]);
61
62static struct bp_cpuinfo *get_bp_info(int cpu, enum bp_type_idx type)
63{
64 return per_cpu_ptr(bp_cpuinfo + type, cpu);
65}
66
67/* Number of pinned CPU breakpoints globally. */
68static struct bp_slots_histogram cpu_pinned[TYPE_MAX];
69/* Number of pinned CPU-independent task breakpoints. */
70static struct bp_slots_histogram tsk_pinned_all[TYPE_MAX];
71
72/* Keep track of the breakpoints attached to tasks */
73static struct rhltable task_bps_ht;
74static const struct rhashtable_params task_bps_ht_params = {
75 .head_offset = offsetof(struct hw_perf_event, bp_list),
76 .key_offset = offsetof(struct hw_perf_event, target),
77 .key_len = sizeof_field(struct hw_perf_event, target),
78 .automatic_shrinking = true,
79};
80
81static bool constraints_initialized __ro_after_init;
82
83/*
84 * Synchronizes accesses to the per-CPU constraints; the locking rules are:
85 *
86 * 1. Atomic updates to bp_cpuinfo::tsk_pinned only require a held read-lock
87 * (due to bp_slots_histogram::count being atomic, no update are lost).
88 *
89 * 2. Holding a write-lock is required for computations that require a
90 * stable snapshot of all bp_cpuinfo::tsk_pinned.
91 *
92 * 3. In all other cases, non-atomic accesses require the appropriately held
93 * lock (read-lock for read-only accesses; write-lock for reads/writes).
94 */
95DEFINE_STATIC_PERCPU_RWSEM(bp_cpuinfo_sem);
96
97/*
98 * Return mutex to serialize accesses to per-task lists in task_bps_ht. Since
99 * rhltable synchronizes concurrent insertions/deletions, independent tasks may
100 * insert/delete concurrently; therefore, a mutex per task is sufficient.
101 *
102 * Uses task_struct::perf_event_mutex, to avoid extending task_struct with a
103 * hw_breakpoint-only mutex, which may be infrequently used. The caveat here is
104 * that hw_breakpoint may contend with per-task perf event list management. The
105 * assumption is that perf usecases involving hw_breakpoints are very unlikely
106 * to result in unnecessary contention.
107 */
108static inline struct mutex *get_task_bps_mutex(struct perf_event *bp)
109{
110 struct task_struct *tsk = bp->hw.target;
111
112 return tsk ? &tsk->perf_event_mutex : NULL;
113}
114
115static struct mutex *bp_constraints_lock(struct perf_event *bp)
116{
117 struct mutex *tsk_mtx = get_task_bps_mutex(bp);
118
119 if (tsk_mtx) {
120 /*
121 * Fully analogous to the perf_try_init_event() nesting
122 * argument in the comment near perf_event_ctx_lock_nested();
123 * this child->perf_event_mutex cannot ever deadlock against
124 * the parent->perf_event_mutex usage from
125 * perf_event_task_{en,dis}able().
126 *
127 * Specifically, inherited events will never occur on
128 * ->perf_event_list.
129 */
130 mutex_lock_nested(tsk_mtx, SINGLE_DEPTH_NESTING);
131 percpu_down_read(&bp_cpuinfo_sem);
132 } else {
133 percpu_down_write(&bp_cpuinfo_sem);
134 }
135
136 return tsk_mtx;
137}
138
139static void bp_constraints_unlock(struct mutex *tsk_mtx)
140{
141 if (tsk_mtx) {
142 percpu_up_read(&bp_cpuinfo_sem);
143 mutex_unlock(tsk_mtx);
144 } else {
145 percpu_up_write(&bp_cpuinfo_sem);
146 }
147}
148
149static bool bp_constraints_is_locked(struct perf_event *bp)
150{
151 struct mutex *tsk_mtx = get_task_bps_mutex(bp);
152
153 return percpu_is_write_locked(&bp_cpuinfo_sem) ||
154 (tsk_mtx ? mutex_is_locked(tsk_mtx) :
155 percpu_is_read_locked(&bp_cpuinfo_sem));
156}
157
158static inline void assert_bp_constraints_lock_held(struct perf_event *bp)
159{
160 struct mutex *tsk_mtx = get_task_bps_mutex(bp);
161
162 if (tsk_mtx)
163 lockdep_assert_held(tsk_mtx);
164 lockdep_assert_held(&bp_cpuinfo_sem);
165}
166
167#ifdef hw_breakpoint_slots
168/*
169 * Number of breakpoint slots is constant, and the same for all types.
170 */
171static_assert(hw_breakpoint_slots(TYPE_INST) == hw_breakpoint_slots(TYPE_DATA));
172static inline int hw_breakpoint_slots_cached(int type) { return hw_breakpoint_slots(type); }
173static inline int init_breakpoint_slots(void) { return 0; }
174#else
175/*
176 * Dynamic number of breakpoint slots.
177 */
178static int __nr_bp_slots[TYPE_MAX] __ro_after_init;
179
180static inline int hw_breakpoint_slots_cached(int type)
181{
182 return __nr_bp_slots[type];
183}
184
185static __init bool
186bp_slots_histogram_alloc(struct bp_slots_histogram *hist, enum bp_type_idx type)
187{
188 hist->count = kcalloc(hw_breakpoint_slots_cached(type), sizeof(*hist->count), GFP_KERNEL);
189 return hist->count;
190}
191
192static __init void bp_slots_histogram_free(struct bp_slots_histogram *hist)
193{
194 kfree(hist->count);
195}
196
197static __init int init_breakpoint_slots(void)
198{
199 int i, cpu, err_cpu;
200
201 for (i = 0; i < TYPE_MAX; i++)
202 __nr_bp_slots[i] = hw_breakpoint_slots(i);
203
204 for_each_possible_cpu(cpu) {
205 for (i = 0; i < TYPE_MAX; i++) {
206 struct bp_cpuinfo *info = get_bp_info(cpu, i);
207
208 if (!bp_slots_histogram_alloc(&info->tsk_pinned, i))
209 goto err;
210 }
211 }
212 for (i = 0; i < TYPE_MAX; i++) {
213 if (!bp_slots_histogram_alloc(&cpu_pinned[i], i))
214 goto err;
215 if (!bp_slots_histogram_alloc(&tsk_pinned_all[i], i))
216 goto err;
217 }
218
219 return 0;
220err:
221 for_each_possible_cpu(err_cpu) {
222 for (i = 0; i < TYPE_MAX; i++)
223 bp_slots_histogram_free(&get_bp_info(err_cpu, i)->tsk_pinned);
224 if (err_cpu == cpu)
225 break;
226 }
227 for (i = 0; i < TYPE_MAX; i++) {
228 bp_slots_histogram_free(&cpu_pinned[i]);
229 bp_slots_histogram_free(&tsk_pinned_all[i]);
230 }
231
232 return -ENOMEM;
233}
234#endif
235
236static inline void
237bp_slots_histogram_add(struct bp_slots_histogram *hist, int old, int val)
238{
239 const int old_idx = old - 1;
240 const int new_idx = old_idx + val;
241
242 if (old_idx >= 0)
243 WARN_ON(atomic_dec_return_relaxed(&hist->count[old_idx]) < 0);
244 if (new_idx >= 0)
245 WARN_ON(atomic_inc_return_relaxed(&hist->count[new_idx]) < 0);
246}
247
248static int
249bp_slots_histogram_max(struct bp_slots_histogram *hist, enum bp_type_idx type)
250{
251 for (int i = hw_breakpoint_slots_cached(type) - 1; i >= 0; i--) {
252 const int count = atomic_read(&hist->count[i]);
253
254 /* Catch unexpected writers; we want a stable snapshot. */
255 ASSERT_EXCLUSIVE_WRITER(hist->count[i]);
256 if (count > 0)
257 return i + 1;
258 WARN(count < 0, "inconsistent breakpoint slots histogram");
259 }
260
261 return 0;
262}
263
264static int
265bp_slots_histogram_max_merge(struct bp_slots_histogram *hist1, struct bp_slots_histogram *hist2,
266 enum bp_type_idx type)
267{
268 for (int i = hw_breakpoint_slots_cached(type) - 1; i >= 0; i--) {
269 const int count1 = atomic_read(&hist1->count[i]);
270 const int count2 = atomic_read(&hist2->count[i]);
271
272 /* Catch unexpected writers; we want a stable snapshot. */
273 ASSERT_EXCLUSIVE_WRITER(hist1->count[i]);
274 ASSERT_EXCLUSIVE_WRITER(hist2->count[i]);
275 if (count1 + count2 > 0)
276 return i + 1;
277 WARN(count1 < 0, "inconsistent breakpoint slots histogram");
278 WARN(count2 < 0, "inconsistent breakpoint slots histogram");
279 }
280
281 return 0;
282}
283
284#ifndef hw_breakpoint_weight
285static inline int hw_breakpoint_weight(struct perf_event *bp)
286{
287 return 1;
288}
289#endif
290
291static inline enum bp_type_idx find_slot_idx(u64 bp_type)
292{
293 if (bp_type & HW_BREAKPOINT_RW)
294 return TYPE_DATA;
295
296 return TYPE_INST;
297}
298
299/*
300 * Return the maximum number of pinned breakpoints a task has in this CPU.
301 */
302static unsigned int max_task_bp_pinned(int cpu, enum bp_type_idx type)
303{
304 struct bp_slots_histogram *tsk_pinned = &get_bp_info(cpu, type)->tsk_pinned;
305
306 /*
307 * At this point we want to have acquired the bp_cpuinfo_sem as a
308 * writer to ensure that there are no concurrent writers in
309 * toggle_bp_task_slot() to tsk_pinned, and we get a stable snapshot.
310 */
311 lockdep_assert_held_write(&bp_cpuinfo_sem);
312 return bp_slots_histogram_max_merge(tsk_pinned, &tsk_pinned_all[type], type);
313}
314
315/*
316 * Count the number of breakpoints of the same type and same task.
317 * The given event must be not on the list.
318 *
319 * If @cpu is -1, but the result of task_bp_pinned() is not CPU-independent,
320 * returns a negative value.
321 */
322static int task_bp_pinned(int cpu, struct perf_event *bp, enum bp_type_idx type)
323{
324 struct rhlist_head *head, *pos;
325 struct perf_event *iter;
326 int count = 0;
327
328 /*
329 * We need a stable snapshot of the per-task breakpoint list.
330 */
331 assert_bp_constraints_lock_held(bp);
332
333 rcu_read_lock();
334 head = rhltable_lookup(&task_bps_ht, &bp->hw.target, task_bps_ht_params);
335 if (!head)
336 goto out;
337
338 rhl_for_each_entry_rcu(iter, pos, head, hw.bp_list) {
339 if (find_slot_idx(iter->attr.bp_type) != type)
340 continue;
341
342 if (iter->cpu >= 0) {
343 if (cpu == -1) {
344 count = -1;
345 goto out;
346 } else if (cpu != iter->cpu)
347 continue;
348 }
349
350 count += hw_breakpoint_weight(iter);
351 }
352
353out:
354 rcu_read_unlock();
355 return count;
356}
357
358static const struct cpumask *cpumask_of_bp(struct perf_event *bp)
359{
360 if (bp->cpu >= 0)
361 return cpumask_of(bp->cpu);
362 return cpu_possible_mask;
363}
364
365/*
366 * Returns the max pinned breakpoint slots in a given
367 * CPU (cpu > -1) or across all of them (cpu = -1).
368 */
369static int
370max_bp_pinned_slots(struct perf_event *bp, enum bp_type_idx type)
371{
372 const struct cpumask *cpumask = cpumask_of_bp(bp);
373 int pinned_slots = 0;
374 int cpu;
375
376 if (bp->hw.target && bp->cpu < 0) {
377 int max_pinned = task_bp_pinned(-1, bp, type);
378
379 if (max_pinned >= 0) {
380 /*
381 * Fast path: task_bp_pinned() is CPU-independent and
382 * returns the same value for any CPU.
383 */
384 max_pinned += bp_slots_histogram_max(&cpu_pinned[type], type);
385 return max_pinned;
386 }
387 }
388
389 for_each_cpu(cpu, cpumask) {
390 struct bp_cpuinfo *info = get_bp_info(cpu, type);
391 int nr;
392
393 nr = info->cpu_pinned;
394 if (!bp->hw.target)
395 nr += max_task_bp_pinned(cpu, type);
396 else
397 nr += task_bp_pinned(cpu, bp, type);
398
399 pinned_slots = max(nr, pinned_slots);
400 }
401
402 return pinned_slots;
403}
404
405/*
406 * Add/remove the given breakpoint in our constraint table
407 */
408static int
409toggle_bp_slot(struct perf_event *bp, bool enable, enum bp_type_idx type, int weight)
410{
411 int cpu, next_tsk_pinned;
412
413 if (!enable)
414 weight = -weight;
415
416 if (!bp->hw.target) {
417 /*
418 * Update the pinned CPU slots, in per-CPU bp_cpuinfo and in the
419 * global histogram.
420 */
421 struct bp_cpuinfo *info = get_bp_info(bp->cpu, type);
422
423 lockdep_assert_held_write(&bp_cpuinfo_sem);
424 bp_slots_histogram_add(&cpu_pinned[type], info->cpu_pinned, weight);
425 info->cpu_pinned += weight;
426 return 0;
427 }
428
429 /*
430 * If bp->hw.target, tsk_pinned is only modified, but not used
431 * otherwise. We can permit concurrent updates as long as there are no
432 * other uses: having acquired bp_cpuinfo_sem as a reader allows
433 * concurrent updates here. Uses of tsk_pinned will require acquiring
434 * bp_cpuinfo_sem as a writer to stabilize tsk_pinned's value.
435 */
436 lockdep_assert_held_read(&bp_cpuinfo_sem);
437
438 /*
439 * Update the pinned task slots, in per-CPU bp_cpuinfo and in the global
440 * histogram. We need to take care of 4 cases:
441 *
442 * 1. This breakpoint targets all CPUs (cpu < 0), and there may only
443 * exist other task breakpoints targeting all CPUs. In this case we
444 * can simply update the global slots histogram.
445 *
446 * 2. This breakpoint targets a specific CPU (cpu >= 0), but there may
447 * only exist other task breakpoints targeting all CPUs.
448 *
449 * a. On enable: remove the existing breakpoints from the global
450 * slots histogram and use the per-CPU histogram.
451 *
452 * b. On disable: re-insert the existing breakpoints into the global
453 * slots histogram and remove from per-CPU histogram.
454 *
455 * 3. Some other existing task breakpoints target specific CPUs. Only
456 * update the per-CPU slots histogram.
457 */
458
459 if (!enable) {
460 /*
461 * Remove before updating histograms so we can determine if this
462 * was the last task breakpoint for a specific CPU.
463 */
464 int ret = rhltable_remove(&task_bps_ht, &bp->hw.bp_list, task_bps_ht_params);
465
466 if (ret)
467 return ret;
468 }
469 /*
470 * Note: If !enable, next_tsk_pinned will not count the to-be-removed breakpoint.
471 */
472 next_tsk_pinned = task_bp_pinned(-1, bp, type);
473
474 if (next_tsk_pinned >= 0) {
475 if (bp->cpu < 0) { /* Case 1: fast path */
476 if (!enable)
477 next_tsk_pinned += hw_breakpoint_weight(bp);
478 bp_slots_histogram_add(&tsk_pinned_all[type], next_tsk_pinned, weight);
479 } else if (enable) { /* Case 2.a: slow path */
480 /* Add existing to per-CPU histograms. */
481 for_each_possible_cpu(cpu) {
482 bp_slots_histogram_add(&get_bp_info(cpu, type)->tsk_pinned,
483 0, next_tsk_pinned);
484 }
485 /* Add this first CPU-pinned task breakpoint. */
486 bp_slots_histogram_add(&get_bp_info(bp->cpu, type)->tsk_pinned,
487 next_tsk_pinned, weight);
488 /* Rebalance global task pinned histogram. */
489 bp_slots_histogram_add(&tsk_pinned_all[type], next_tsk_pinned,
490 -next_tsk_pinned);
491 } else { /* Case 2.b: slow path */
492 /* Remove this last CPU-pinned task breakpoint. */
493 bp_slots_histogram_add(&get_bp_info(bp->cpu, type)->tsk_pinned,
494 next_tsk_pinned + hw_breakpoint_weight(bp), weight);
495 /* Remove all from per-CPU histograms. */
496 for_each_possible_cpu(cpu) {
497 bp_slots_histogram_add(&get_bp_info(cpu, type)->tsk_pinned,
498 next_tsk_pinned, -next_tsk_pinned);
499 }
500 /* Rebalance global task pinned histogram. */
501 bp_slots_histogram_add(&tsk_pinned_all[type], 0, next_tsk_pinned);
502 }
503 } else { /* Case 3: slow path */
504 const struct cpumask *cpumask = cpumask_of_bp(bp);
505
506 for_each_cpu(cpu, cpumask) {
507 next_tsk_pinned = task_bp_pinned(cpu, bp, type);
508 if (!enable)
509 next_tsk_pinned += hw_breakpoint_weight(bp);
510 bp_slots_histogram_add(&get_bp_info(cpu, type)->tsk_pinned,
511 next_tsk_pinned, weight);
512 }
513 }
514
515 /*
516 * Readers want a stable snapshot of the per-task breakpoint list.
517 */
518 assert_bp_constraints_lock_held(bp);
519
520 if (enable)
521 return rhltable_insert(&task_bps_ht, &bp->hw.bp_list, task_bps_ht_params);
522
523 return 0;
524}
525
526__weak int arch_reserve_bp_slot(struct perf_event *bp)
527{
528 return 0;
529}
530
531__weak void arch_release_bp_slot(struct perf_event *bp)
532{
533}
534
535/*
536 * Function to perform processor-specific cleanup during unregistration
537 */
538__weak void arch_unregister_hw_breakpoint(struct perf_event *bp)
539{
540 /*
541 * A weak stub function here for those archs that don't define
542 * it inside arch/.../kernel/hw_breakpoint.c
543 */
544}
545
546/*
547 * Constraints to check before allowing this new breakpoint counter.
548 *
549 * Note: Flexible breakpoints are currently unimplemented, but outlined in the
550 * below algorithm for completeness. The implementation treats flexible as
551 * pinned due to no guarantee that we currently always schedule flexible events
552 * before a pinned event in a same CPU.
553 *
554 * == Non-pinned counter == (Considered as pinned for now)
555 *
556 * - If attached to a single cpu, check:
557 *
558 * (per_cpu(info->flexible, cpu) || (per_cpu(info->cpu_pinned, cpu)
559 * + max(per_cpu(info->tsk_pinned, cpu)))) < HBP_NUM
560 *
561 * -> If there are already non-pinned counters in this cpu, it means
562 * there is already a free slot for them.
563 * Otherwise, we check that the maximum number of per task
564 * breakpoints (for this cpu) plus the number of per cpu breakpoint
565 * (for this cpu) doesn't cover every registers.
566 *
567 * - If attached to every cpus, check:
568 *
569 * (per_cpu(info->flexible, *) || (max(per_cpu(info->cpu_pinned, *))
570 * + max(per_cpu(info->tsk_pinned, *)))) < HBP_NUM
571 *
572 * -> This is roughly the same, except we check the number of per cpu
573 * bp for every cpu and we keep the max one. Same for the per tasks
574 * breakpoints.
575 *
576 *
577 * == Pinned counter ==
578 *
579 * - If attached to a single cpu, check:
580 *
581 * ((per_cpu(info->flexible, cpu) > 1) + per_cpu(info->cpu_pinned, cpu)
582 * + max(per_cpu(info->tsk_pinned, cpu))) < HBP_NUM
583 *
584 * -> Same checks as before. But now the info->flexible, if any, must keep
585 * one register at least (or they will never be fed).
586 *
587 * - If attached to every cpus, check:
588 *
589 * ((per_cpu(info->flexible, *) > 1) + max(per_cpu(info->cpu_pinned, *))
590 * + max(per_cpu(info->tsk_pinned, *))) < HBP_NUM
591 */
592static int __reserve_bp_slot(struct perf_event *bp, u64 bp_type)
593{
594 enum bp_type_idx type;
595 int max_pinned_slots;
596 int weight;
597 int ret;
598
599 /* We couldn't initialize breakpoint constraints on boot */
600 if (!constraints_initialized)
601 return -ENOMEM;
602
603 /* Basic checks */
604 if (bp_type == HW_BREAKPOINT_EMPTY ||
605 bp_type == HW_BREAKPOINT_INVALID)
606 return -EINVAL;
607
608 type = find_slot_idx(bp_type);
609 weight = hw_breakpoint_weight(bp);
610
611 /* Check if this new breakpoint can be satisfied across all CPUs. */
612 max_pinned_slots = max_bp_pinned_slots(bp, type) + weight;
613 if (max_pinned_slots > hw_breakpoint_slots_cached(type))
614 return -ENOSPC;
615
616 ret = arch_reserve_bp_slot(bp);
617 if (ret)
618 return ret;
619
620 return toggle_bp_slot(bp, true, type, weight);
621}
622
623int reserve_bp_slot(struct perf_event *bp)
624{
625 struct mutex *mtx = bp_constraints_lock(bp);
626 int ret = __reserve_bp_slot(bp, bp->attr.bp_type);
627
628 bp_constraints_unlock(mtx);
629 return ret;
630}
631
632static void __release_bp_slot(struct perf_event *bp, u64 bp_type)
633{
634 enum bp_type_idx type;
635 int weight;
636
637 arch_release_bp_slot(bp);
638
639 type = find_slot_idx(bp_type);
640 weight = hw_breakpoint_weight(bp);
641 WARN_ON(toggle_bp_slot(bp, false, type, weight));
642}
643
644void release_bp_slot(struct perf_event *bp)
645{
646 struct mutex *mtx = bp_constraints_lock(bp);
647
648 arch_unregister_hw_breakpoint(bp);
649 __release_bp_slot(bp, bp->attr.bp_type);
650 bp_constraints_unlock(mtx);
651}
652
653static int __modify_bp_slot(struct perf_event *bp, u64 old_type, u64 new_type)
654{
655 int err;
656
657 __release_bp_slot(bp, old_type);
658
659 err = __reserve_bp_slot(bp, new_type);
660 if (err) {
661 /*
662 * Reserve the old_type slot back in case
663 * there's no space for the new type.
664 *
665 * This must succeed, because we just released
666 * the old_type slot in the __release_bp_slot
667 * call above. If not, something is broken.
668 */
669 WARN_ON(__reserve_bp_slot(bp, old_type));
670 }
671
672 return err;
673}
674
675static int modify_bp_slot(struct perf_event *bp, u64 old_type, u64 new_type)
676{
677 struct mutex *mtx = bp_constraints_lock(bp);
678 int ret = __modify_bp_slot(bp, old_type, new_type);
679
680 bp_constraints_unlock(mtx);
681 return ret;
682}
683
684/*
685 * Allow the kernel debugger to reserve breakpoint slots without
686 * taking a lock using the dbg_* variant of for the reserve and
687 * release breakpoint slots.
688 */
689int dbg_reserve_bp_slot(struct perf_event *bp)
690{
691 int ret;
692
693 if (bp_constraints_is_locked(bp))
694 return -1;
695
696 /* Locks aren't held; disable lockdep assert checking. */
697 lockdep_off();
698 ret = __reserve_bp_slot(bp, bp->attr.bp_type);
699 lockdep_on();
700
701 return ret;
702}
703
704int dbg_release_bp_slot(struct perf_event *bp)
705{
706 if (bp_constraints_is_locked(bp))
707 return -1;
708
709 /* Locks aren't held; disable lockdep assert checking. */
710 lockdep_off();
711 __release_bp_slot(bp, bp->attr.bp_type);
712 lockdep_on();
713
714 return 0;
715}
716
717static int hw_breakpoint_parse(struct perf_event *bp,
718 const struct perf_event_attr *attr,
719 struct arch_hw_breakpoint *hw)
720{
721 int err;
722
723 err = hw_breakpoint_arch_parse(bp, attr, hw);
724 if (err)
725 return err;
726
727 if (arch_check_bp_in_kernelspace(hw)) {
728 if (attr->exclude_kernel)
729 return -EINVAL;
730 /*
731 * Don't let unprivileged users set a breakpoint in the trap
732 * path to avoid trap recursion attacks.
733 */
734 if (!capable(CAP_SYS_ADMIN))
735 return -EPERM;
736 }
737
738 return 0;
739}
740
741int register_perf_hw_breakpoint(struct perf_event *bp)
742{
743 struct arch_hw_breakpoint hw = { };
744 int err;
745
746 err = reserve_bp_slot(bp);
747 if (err)
748 return err;
749
750 err = hw_breakpoint_parse(bp, &bp->attr, &hw);
751 if (err) {
752 release_bp_slot(bp);
753 return err;
754 }
755
756 bp->hw.info = hw;
757
758 return 0;
759}
760
761/**
762 * register_user_hw_breakpoint - register a hardware breakpoint for user space
763 * @attr: breakpoint attributes
764 * @triggered: callback to trigger when we hit the breakpoint
765 * @context: context data could be used in the triggered callback
766 * @tsk: pointer to 'task_struct' of the process to which the address belongs
767 */
768struct perf_event *
769register_user_hw_breakpoint(struct perf_event_attr *attr,
770 perf_overflow_handler_t triggered,
771 void *context,
772 struct task_struct *tsk)
773{
774 return perf_event_create_kernel_counter(attr, -1, tsk, triggered,
775 context);
776}
777EXPORT_SYMBOL_GPL(register_user_hw_breakpoint);
778
779static void hw_breakpoint_copy_attr(struct perf_event_attr *to,
780 struct perf_event_attr *from)
781{
782 to->bp_addr = from->bp_addr;
783 to->bp_type = from->bp_type;
784 to->bp_len = from->bp_len;
785 to->disabled = from->disabled;
786}
787
788int
789modify_user_hw_breakpoint_check(struct perf_event *bp, struct perf_event_attr *attr,
790 bool check)
791{
792 struct arch_hw_breakpoint hw = { };
793 int err;
794
795 err = hw_breakpoint_parse(bp, attr, &hw);
796 if (err)
797 return err;
798
799 if (check) {
800 struct perf_event_attr old_attr;
801
802 old_attr = bp->attr;
803 hw_breakpoint_copy_attr(&old_attr, attr);
804 if (memcmp(&old_attr, attr, sizeof(*attr)))
805 return -EINVAL;
806 }
807
808 if (bp->attr.bp_type != attr->bp_type) {
809 err = modify_bp_slot(bp, bp->attr.bp_type, attr->bp_type);
810 if (err)
811 return err;
812 }
813
814 hw_breakpoint_copy_attr(&bp->attr, attr);
815 bp->hw.info = hw;
816
817 return 0;
818}
819
820/**
821 * modify_user_hw_breakpoint - modify a user-space hardware breakpoint
822 * @bp: the breakpoint structure to modify
823 * @attr: new breakpoint attributes
824 */
825int modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *attr)
826{
827 int err;
828
829 /*
830 * modify_user_hw_breakpoint can be invoked with IRQs disabled and hence it
831 * will not be possible to raise IPIs that invoke __perf_event_disable.
832 * So call the function directly after making sure we are targeting the
833 * current task.
834 */
835 if (irqs_disabled() && bp->ctx && bp->ctx->task == current)
836 perf_event_disable_local(bp);
837 else
838 perf_event_disable(bp);
839
840 err = modify_user_hw_breakpoint_check(bp, attr, false);
841
842 if (!bp->attr.disabled)
843 perf_event_enable(bp);
844
845 return err;
846}
847EXPORT_SYMBOL_GPL(modify_user_hw_breakpoint);
848
849/**
850 * unregister_hw_breakpoint - unregister a user-space hardware breakpoint
851 * @bp: the breakpoint structure to unregister
852 */
853void unregister_hw_breakpoint(struct perf_event *bp)
854{
855 if (!bp)
856 return;
857 perf_event_release_kernel(bp);
858}
859EXPORT_SYMBOL_GPL(unregister_hw_breakpoint);
860
861/**
862 * register_wide_hw_breakpoint - register a wide breakpoint in the kernel
863 * @attr: breakpoint attributes
864 * @triggered: callback to trigger when we hit the breakpoint
865 * @context: context data could be used in the triggered callback
866 *
867 * @return a set of per_cpu pointers to perf events
868 */
869struct perf_event * __percpu *
870register_wide_hw_breakpoint(struct perf_event_attr *attr,
871 perf_overflow_handler_t triggered,
872 void *context)
873{
874 struct perf_event * __percpu *cpu_events, *bp;
875 long err = 0;
876 int cpu;
877
878 cpu_events = alloc_percpu(typeof(*cpu_events));
879 if (!cpu_events)
880 return (void __percpu __force *)ERR_PTR(-ENOMEM);
881
882 cpus_read_lock();
883 for_each_online_cpu(cpu) {
884 bp = perf_event_create_kernel_counter(attr, cpu, NULL,
885 triggered, context);
886 if (IS_ERR(bp)) {
887 err = PTR_ERR(bp);
888 break;
889 }
890
891 per_cpu(*cpu_events, cpu) = bp;
892 }
893 cpus_read_unlock();
894
895 if (likely(!err))
896 return cpu_events;
897
898 unregister_wide_hw_breakpoint(cpu_events);
899 return (void __percpu __force *)ERR_PTR(err);
900}
901EXPORT_SYMBOL_GPL(register_wide_hw_breakpoint);
902
903/**
904 * unregister_wide_hw_breakpoint - unregister a wide breakpoint in the kernel
905 * @cpu_events: the per cpu set of events to unregister
906 */
907void unregister_wide_hw_breakpoint(struct perf_event * __percpu *cpu_events)
908{
909 int cpu;
910
911 for_each_possible_cpu(cpu)
912 unregister_hw_breakpoint(per_cpu(*cpu_events, cpu));
913
914 free_percpu(cpu_events);
915}
916EXPORT_SYMBOL_GPL(unregister_wide_hw_breakpoint);
917
918/**
919 * hw_breakpoint_is_used - check if breakpoints are currently used
920 *
921 * Returns: true if breakpoints are used, false otherwise.
922 */
923bool hw_breakpoint_is_used(void)
924{
925 int cpu;
926
927 if (!constraints_initialized)
928 return false;
929
930 for_each_possible_cpu(cpu) {
931 for (int type = 0; type < TYPE_MAX; ++type) {
932 struct bp_cpuinfo *info = get_bp_info(cpu, type);
933
934 if (info->cpu_pinned)
935 return true;
936
937 for (int slot = 0; slot < hw_breakpoint_slots_cached(type); ++slot) {
938 if (atomic_read(&info->tsk_pinned.count[slot]))
939 return true;
940 }
941 }
942 }
943
944 for (int type = 0; type < TYPE_MAX; ++type) {
945 for (int slot = 0; slot < hw_breakpoint_slots_cached(type); ++slot) {
946 /*
947 * Warn, because if there are CPU pinned counters,
948 * should never get here; bp_cpuinfo::cpu_pinned should
949 * be consistent with the global cpu_pinned histogram.
950 */
951 if (WARN_ON(atomic_read(&cpu_pinned[type].count[slot])))
952 return true;
953
954 if (atomic_read(&tsk_pinned_all[type].count[slot]))
955 return true;
956 }
957 }
958
959 return false;
960}
961
962static struct notifier_block hw_breakpoint_exceptions_nb = {
963 .notifier_call = hw_breakpoint_exceptions_notify,
964 /* we need to be notified first */
965 .priority = 0x7fffffff
966};
967
968static void bp_perf_event_destroy(struct perf_event *event)
969{
970 release_bp_slot(event);
971}
972
973static int hw_breakpoint_event_init(struct perf_event *bp)
974{
975 int err;
976
977 if (bp->attr.type != PERF_TYPE_BREAKPOINT)
978 return -ENOENT;
979
980 /*
981 * no branch sampling for breakpoint events
982 */
983 if (has_branch_stack(bp))
984 return -EOPNOTSUPP;
985
986 err = register_perf_hw_breakpoint(bp);
987 if (err)
988 return err;
989
990 bp->destroy = bp_perf_event_destroy;
991
992 return 0;
993}
994
995static int hw_breakpoint_add(struct perf_event *bp, int flags)
996{
997 if (!(flags & PERF_EF_START))
998 bp->hw.state = PERF_HES_STOPPED;
999
1000 if (is_sampling_event(bp)) {
1001 bp->hw.last_period = bp->hw.sample_period;
1002 perf_swevent_set_period(bp);
1003 }
1004
1005 return arch_install_hw_breakpoint(bp);
1006}
1007
1008static void hw_breakpoint_del(struct perf_event *bp, int flags)
1009{
1010 arch_uninstall_hw_breakpoint(bp);
1011}
1012
1013static void hw_breakpoint_start(struct perf_event *bp, int flags)
1014{
1015 bp->hw.state = 0;
1016}
1017
1018static void hw_breakpoint_stop(struct perf_event *bp, int flags)
1019{
1020 bp->hw.state = PERF_HES_STOPPED;
1021}
1022
1023static struct pmu perf_breakpoint = {
1024 .task_ctx_nr = perf_sw_context, /* could eventually get its own */
1025
1026 .event_init = hw_breakpoint_event_init,
1027 .add = hw_breakpoint_add,
1028 .del = hw_breakpoint_del,
1029 .start = hw_breakpoint_start,
1030 .stop = hw_breakpoint_stop,
1031 .read = hw_breakpoint_pmu_read,
1032};
1033
1034int __init init_hw_breakpoint(void)
1035{
1036 int ret;
1037
1038 ret = rhltable_init(&task_bps_ht, &task_bps_ht_params);
1039 if (ret)
1040 return ret;
1041
1042 ret = init_breakpoint_slots();
1043 if (ret)
1044 return ret;
1045
1046 constraints_initialized = true;
1047
1048 perf_pmu_register(&perf_breakpoint, "breakpoint", PERF_TYPE_BREAKPOINT);
1049
1050 return register_die_notifier(&hw_breakpoint_exceptions_nb);
1051}
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 err = register_perf_hw_breakpoint(bp);
585 if (err)
586 return err;
587
588 bp->destroy = bp_perf_event_destroy;
589
590 return 0;
591}
592
593static int hw_breakpoint_add(struct perf_event *bp, int flags)
594{
595 if (!(flags & PERF_EF_START))
596 bp->hw.state = PERF_HES_STOPPED;
597
598 return arch_install_hw_breakpoint(bp);
599}
600
601static void hw_breakpoint_del(struct perf_event *bp, int flags)
602{
603 arch_uninstall_hw_breakpoint(bp);
604}
605
606static void hw_breakpoint_start(struct perf_event *bp, int flags)
607{
608 bp->hw.state = 0;
609}
610
611static void hw_breakpoint_stop(struct perf_event *bp, int flags)
612{
613 bp->hw.state = PERF_HES_STOPPED;
614}
615
616static struct pmu perf_breakpoint = {
617 .task_ctx_nr = perf_sw_context, /* could eventually get its own */
618
619 .event_init = hw_breakpoint_event_init,
620 .add = hw_breakpoint_add,
621 .del = hw_breakpoint_del,
622 .start = hw_breakpoint_start,
623 .stop = hw_breakpoint_stop,
624 .read = hw_breakpoint_pmu_read,
625};
626
627int __init init_hw_breakpoint(void)
628{
629 unsigned int **task_bp_pinned;
630 int cpu, err_cpu;
631 int i;
632
633 for (i = 0; i < TYPE_MAX; i++)
634 nr_slots[i] = hw_breakpoint_slots(i);
635
636 for_each_possible_cpu(cpu) {
637 for (i = 0; i < TYPE_MAX; i++) {
638 task_bp_pinned = &per_cpu(nr_task_bp_pinned[i], cpu);
639 *task_bp_pinned = kzalloc(sizeof(int) * nr_slots[i],
640 GFP_KERNEL);
641 if (!*task_bp_pinned)
642 goto err_alloc;
643 }
644 }
645
646 constraints_initialized = 1;
647
648 perf_pmu_register(&perf_breakpoint, "breakpoint", PERF_TYPE_BREAKPOINT);
649
650 return register_die_notifier(&hw_breakpoint_exceptions_nb);
651
652 err_alloc:
653 for_each_possible_cpu(err_cpu) {
654 if (err_cpu == cpu)
655 break;
656 for (i = 0; i < TYPE_MAX; i++)
657 kfree(per_cpu(nr_task_bp_pinned[i], cpu));
658 }
659
660 return -ENOMEM;
661}
662
663