Loading...
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/*
217 * Function to perform processor-specific cleanup during unregistration
218 */
219__weak void arch_unregister_hw_breakpoint(struct perf_event *bp)
220{
221 /*
222 * A weak stub function here for those archs that don't define
223 * it inside arch/.../kernel/hw_breakpoint.c
224 */
225}
226
227/*
228 * Constraints to check before allowing this new breakpoint counter:
229 *
230 * == Non-pinned counter == (Considered as pinned for now)
231 *
232 * - If attached to a single cpu, check:
233 *
234 * (per_cpu(info->flexible, cpu) || (per_cpu(info->cpu_pinned, cpu)
235 * + max(per_cpu(info->tsk_pinned, cpu)))) < HBP_NUM
236 *
237 * -> If there are already non-pinned counters in this cpu, it means
238 * there is already a free slot for them.
239 * Otherwise, we check that the maximum number of per task
240 * breakpoints (for this cpu) plus the number of per cpu breakpoint
241 * (for this cpu) doesn't cover every registers.
242 *
243 * - If attached to every cpus, check:
244 *
245 * (per_cpu(info->flexible, *) || (max(per_cpu(info->cpu_pinned, *))
246 * + max(per_cpu(info->tsk_pinned, *)))) < HBP_NUM
247 *
248 * -> This is roughly the same, except we check the number of per cpu
249 * bp for every cpu and we keep the max one. Same for the per tasks
250 * breakpoints.
251 *
252 *
253 * == Pinned counter ==
254 *
255 * - If attached to a single cpu, check:
256 *
257 * ((per_cpu(info->flexible, cpu) > 1) + per_cpu(info->cpu_pinned, cpu)
258 * + max(per_cpu(info->tsk_pinned, cpu))) < HBP_NUM
259 *
260 * -> Same checks as before. But now the info->flexible, if any, must keep
261 * one register at least (or they will never be fed).
262 *
263 * - If attached to every cpus, check:
264 *
265 * ((per_cpu(info->flexible, *) > 1) + max(per_cpu(info->cpu_pinned, *))
266 * + max(per_cpu(info->tsk_pinned, *))) < HBP_NUM
267 */
268static int __reserve_bp_slot(struct perf_event *bp, u64 bp_type)
269{
270 struct bp_busy_slots slots = {0};
271 enum bp_type_idx type;
272 int weight;
273
274 /* We couldn't initialize breakpoint constraints on boot */
275 if (!constraints_initialized)
276 return -ENOMEM;
277
278 /* Basic checks */
279 if (bp_type == HW_BREAKPOINT_EMPTY ||
280 bp_type == HW_BREAKPOINT_INVALID)
281 return -EINVAL;
282
283 type = find_slot_idx(bp_type);
284 weight = hw_breakpoint_weight(bp);
285
286 fetch_bp_busy_slots(&slots, bp, type);
287 /*
288 * Simulate the addition of this breakpoint to the constraints
289 * and see the result.
290 */
291 fetch_this_slot(&slots, weight);
292
293 /* Flexible counters need to keep at least one slot */
294 if (slots.pinned + (!!slots.flexible) > nr_slots[type])
295 return -ENOSPC;
296
297 toggle_bp_slot(bp, true, type, weight);
298
299 return 0;
300}
301
302int reserve_bp_slot(struct perf_event *bp)
303{
304 int ret;
305
306 mutex_lock(&nr_bp_mutex);
307
308 ret = __reserve_bp_slot(bp, bp->attr.bp_type);
309
310 mutex_unlock(&nr_bp_mutex);
311
312 return ret;
313}
314
315static void __release_bp_slot(struct perf_event *bp, u64 bp_type)
316{
317 enum bp_type_idx type;
318 int weight;
319
320 type = find_slot_idx(bp_type);
321 weight = hw_breakpoint_weight(bp);
322 toggle_bp_slot(bp, false, type, weight);
323}
324
325void release_bp_slot(struct perf_event *bp)
326{
327 mutex_lock(&nr_bp_mutex);
328
329 arch_unregister_hw_breakpoint(bp);
330 __release_bp_slot(bp, bp->attr.bp_type);
331
332 mutex_unlock(&nr_bp_mutex);
333}
334
335static int __modify_bp_slot(struct perf_event *bp, u64 old_type, u64 new_type)
336{
337 int err;
338
339 __release_bp_slot(bp, old_type);
340
341 err = __reserve_bp_slot(bp, new_type);
342 if (err) {
343 /*
344 * Reserve the old_type slot back in case
345 * there's no space for the new type.
346 *
347 * This must succeed, because we just released
348 * the old_type slot in the __release_bp_slot
349 * call above. If not, something is broken.
350 */
351 WARN_ON(__reserve_bp_slot(bp, old_type));
352 }
353
354 return err;
355}
356
357static int modify_bp_slot(struct perf_event *bp, u64 old_type, u64 new_type)
358{
359 int ret;
360
361 mutex_lock(&nr_bp_mutex);
362 ret = __modify_bp_slot(bp, old_type, new_type);
363 mutex_unlock(&nr_bp_mutex);
364 return ret;
365}
366
367/*
368 * Allow the kernel debugger to reserve breakpoint slots without
369 * taking a lock using the dbg_* variant of for the reserve and
370 * release breakpoint slots.
371 */
372int dbg_reserve_bp_slot(struct perf_event *bp)
373{
374 if (mutex_is_locked(&nr_bp_mutex))
375 return -1;
376
377 return __reserve_bp_slot(bp, bp->attr.bp_type);
378}
379
380int dbg_release_bp_slot(struct perf_event *bp)
381{
382 if (mutex_is_locked(&nr_bp_mutex))
383 return -1;
384
385 __release_bp_slot(bp, bp->attr.bp_type);
386
387 return 0;
388}
389
390static int hw_breakpoint_parse(struct perf_event *bp,
391 const struct perf_event_attr *attr,
392 struct arch_hw_breakpoint *hw)
393{
394 int err;
395
396 err = hw_breakpoint_arch_parse(bp, attr, hw);
397 if (err)
398 return err;
399
400 if (arch_check_bp_in_kernelspace(hw)) {
401 if (attr->exclude_kernel)
402 return -EINVAL;
403 /*
404 * Don't let unprivileged users set a breakpoint in the trap
405 * path to avoid trap recursion attacks.
406 */
407 if (!capable(CAP_SYS_ADMIN))
408 return -EPERM;
409 }
410
411 return 0;
412}
413
414int register_perf_hw_breakpoint(struct perf_event *bp)
415{
416 struct arch_hw_breakpoint hw = { };
417 int err;
418
419 err = reserve_bp_slot(bp);
420 if (err)
421 return err;
422
423 err = hw_breakpoint_parse(bp, &bp->attr, &hw);
424 if (err) {
425 release_bp_slot(bp);
426 return err;
427 }
428
429 bp->hw.info = hw;
430
431 return 0;
432}
433
434/**
435 * register_user_hw_breakpoint - register a hardware breakpoint for user space
436 * @attr: breakpoint attributes
437 * @triggered: callback to trigger when we hit the breakpoint
438 * @tsk: pointer to 'task_struct' of the process to which the address belongs
439 */
440struct perf_event *
441register_user_hw_breakpoint(struct perf_event_attr *attr,
442 perf_overflow_handler_t triggered,
443 void *context,
444 struct task_struct *tsk)
445{
446 return perf_event_create_kernel_counter(attr, -1, tsk, triggered,
447 context);
448}
449EXPORT_SYMBOL_GPL(register_user_hw_breakpoint);
450
451static void hw_breakpoint_copy_attr(struct perf_event_attr *to,
452 struct perf_event_attr *from)
453{
454 to->bp_addr = from->bp_addr;
455 to->bp_type = from->bp_type;
456 to->bp_len = from->bp_len;
457 to->disabled = from->disabled;
458}
459
460int
461modify_user_hw_breakpoint_check(struct perf_event *bp, struct perf_event_attr *attr,
462 bool check)
463{
464 struct arch_hw_breakpoint hw = { };
465 int err;
466
467 err = hw_breakpoint_parse(bp, attr, &hw);
468 if (err)
469 return err;
470
471 if (check) {
472 struct perf_event_attr old_attr;
473
474 old_attr = bp->attr;
475 hw_breakpoint_copy_attr(&old_attr, attr);
476 if (memcmp(&old_attr, attr, sizeof(*attr)))
477 return -EINVAL;
478 }
479
480 if (bp->attr.bp_type != attr->bp_type) {
481 err = modify_bp_slot(bp, bp->attr.bp_type, attr->bp_type);
482 if (err)
483 return err;
484 }
485
486 hw_breakpoint_copy_attr(&bp->attr, attr);
487 bp->hw.info = hw;
488
489 return 0;
490}
491
492/**
493 * modify_user_hw_breakpoint - modify a user-space hardware breakpoint
494 * @bp: the breakpoint structure to modify
495 * @attr: new breakpoint attributes
496 */
497int modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *attr)
498{
499 int err;
500
501 /*
502 * modify_user_hw_breakpoint can be invoked with IRQs disabled and hence it
503 * will not be possible to raise IPIs that invoke __perf_event_disable.
504 * So call the function directly after making sure we are targeting the
505 * current task.
506 */
507 if (irqs_disabled() && bp->ctx && bp->ctx->task == current)
508 perf_event_disable_local(bp);
509 else
510 perf_event_disable(bp);
511
512 err = modify_user_hw_breakpoint_check(bp, attr, false);
513
514 if (!bp->attr.disabled)
515 perf_event_enable(bp);
516
517 return err;
518}
519EXPORT_SYMBOL_GPL(modify_user_hw_breakpoint);
520
521/**
522 * unregister_hw_breakpoint - unregister a user-space hardware breakpoint
523 * @bp: the breakpoint structure to unregister
524 */
525void unregister_hw_breakpoint(struct perf_event *bp)
526{
527 if (!bp)
528 return;
529 perf_event_release_kernel(bp);
530}
531EXPORT_SYMBOL_GPL(unregister_hw_breakpoint);
532
533/**
534 * register_wide_hw_breakpoint - register a wide breakpoint in the kernel
535 * @attr: breakpoint attributes
536 * @triggered: callback to trigger when we hit the breakpoint
537 *
538 * @return a set of per_cpu pointers to perf events
539 */
540struct perf_event * __percpu *
541register_wide_hw_breakpoint(struct perf_event_attr *attr,
542 perf_overflow_handler_t triggered,
543 void *context)
544{
545 struct perf_event * __percpu *cpu_events, *bp;
546 long err = 0;
547 int cpu;
548
549 cpu_events = alloc_percpu(typeof(*cpu_events));
550 if (!cpu_events)
551 return (void __percpu __force *)ERR_PTR(-ENOMEM);
552
553 get_online_cpus();
554 for_each_online_cpu(cpu) {
555 bp = perf_event_create_kernel_counter(attr, cpu, NULL,
556 triggered, context);
557 if (IS_ERR(bp)) {
558 err = PTR_ERR(bp);
559 break;
560 }
561
562 per_cpu(*cpu_events, cpu) = bp;
563 }
564 put_online_cpus();
565
566 if (likely(!err))
567 return cpu_events;
568
569 unregister_wide_hw_breakpoint(cpu_events);
570 return (void __percpu __force *)ERR_PTR(err);
571}
572EXPORT_SYMBOL_GPL(register_wide_hw_breakpoint);
573
574/**
575 * unregister_wide_hw_breakpoint - unregister a wide breakpoint in the kernel
576 * @cpu_events: the per cpu set of events to unregister
577 */
578void unregister_wide_hw_breakpoint(struct perf_event * __percpu *cpu_events)
579{
580 int cpu;
581
582 for_each_possible_cpu(cpu)
583 unregister_hw_breakpoint(per_cpu(*cpu_events, cpu));
584
585 free_percpu(cpu_events);
586}
587EXPORT_SYMBOL_GPL(unregister_wide_hw_breakpoint);
588
589static struct notifier_block hw_breakpoint_exceptions_nb = {
590 .notifier_call = hw_breakpoint_exceptions_notify,
591 /* we need to be notified first */
592 .priority = 0x7fffffff
593};
594
595static void bp_perf_event_destroy(struct perf_event *event)
596{
597 release_bp_slot(event);
598}
599
600static int hw_breakpoint_event_init(struct perf_event *bp)
601{
602 int err;
603
604 if (bp->attr.type != PERF_TYPE_BREAKPOINT)
605 return -ENOENT;
606
607 /*
608 * no branch sampling for breakpoint events
609 */
610 if (has_branch_stack(bp))
611 return -EOPNOTSUPP;
612
613 err = register_perf_hw_breakpoint(bp);
614 if (err)
615 return err;
616
617 bp->destroy = bp_perf_event_destroy;
618
619 return 0;
620}
621
622static int hw_breakpoint_add(struct perf_event *bp, int flags)
623{
624 if (!(flags & PERF_EF_START))
625 bp->hw.state = PERF_HES_STOPPED;
626
627 if (is_sampling_event(bp)) {
628 bp->hw.last_period = bp->hw.sample_period;
629 perf_swevent_set_period(bp);
630 }
631
632 return arch_install_hw_breakpoint(bp);
633}
634
635static void hw_breakpoint_del(struct perf_event *bp, int flags)
636{
637 arch_uninstall_hw_breakpoint(bp);
638}
639
640static void hw_breakpoint_start(struct perf_event *bp, int flags)
641{
642 bp->hw.state = 0;
643}
644
645static void hw_breakpoint_stop(struct perf_event *bp, int flags)
646{
647 bp->hw.state = PERF_HES_STOPPED;
648}
649
650static struct pmu perf_breakpoint = {
651 .task_ctx_nr = perf_sw_context, /* could eventually get its own */
652
653 .event_init = hw_breakpoint_event_init,
654 .add = hw_breakpoint_add,
655 .del = hw_breakpoint_del,
656 .start = hw_breakpoint_start,
657 .stop = hw_breakpoint_stop,
658 .read = hw_breakpoint_pmu_read,
659};
660
661int __init init_hw_breakpoint(void)
662{
663 int cpu, err_cpu;
664 int i;
665
666 for (i = 0; i < TYPE_MAX; i++)
667 nr_slots[i] = hw_breakpoint_slots(i);
668
669 for_each_possible_cpu(cpu) {
670 for (i = 0; i < TYPE_MAX; i++) {
671 struct bp_cpuinfo *info = get_bp_info(cpu, i);
672
673 info->tsk_pinned = kcalloc(nr_slots[i], sizeof(int),
674 GFP_KERNEL);
675 if (!info->tsk_pinned)
676 goto err_alloc;
677 }
678 }
679
680 constraints_initialized = 1;
681
682 perf_pmu_register(&perf_breakpoint, "breakpoint", PERF_TYPE_BREAKPOINT);
683
684 return register_die_notifier(&hw_breakpoint_exceptions_nb);
685
686 err_alloc:
687 for_each_possible_cpu(err_cpu) {
688 for (i = 0; i < TYPE_MAX; i++)
689 kfree(get_bp_info(err_cpu, i)->tsk_pinned);
690 if (err_cpu == cpu)
691 break;
692 }
693
694 return -ENOMEM;
695}
696
697
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 * @context: context data could be used in the triggered callback
455 * @tsk: pointer to 'task_struct' of the process to which the address belongs
456 */
457struct perf_event *
458register_user_hw_breakpoint(struct perf_event_attr *attr,
459 perf_overflow_handler_t triggered,
460 void *context,
461 struct task_struct *tsk)
462{
463 return perf_event_create_kernel_counter(attr, -1, tsk, triggered,
464 context);
465}
466EXPORT_SYMBOL_GPL(register_user_hw_breakpoint);
467
468static void hw_breakpoint_copy_attr(struct perf_event_attr *to,
469 struct perf_event_attr *from)
470{
471 to->bp_addr = from->bp_addr;
472 to->bp_type = from->bp_type;
473 to->bp_len = from->bp_len;
474 to->disabled = from->disabled;
475}
476
477int
478modify_user_hw_breakpoint_check(struct perf_event *bp, struct perf_event_attr *attr,
479 bool check)
480{
481 struct arch_hw_breakpoint hw = { };
482 int err;
483
484 err = hw_breakpoint_parse(bp, attr, &hw);
485 if (err)
486 return err;
487
488 if (check) {
489 struct perf_event_attr old_attr;
490
491 old_attr = bp->attr;
492 hw_breakpoint_copy_attr(&old_attr, attr);
493 if (memcmp(&old_attr, attr, sizeof(*attr)))
494 return -EINVAL;
495 }
496
497 if (bp->attr.bp_type != attr->bp_type) {
498 err = modify_bp_slot(bp, bp->attr.bp_type, attr->bp_type);
499 if (err)
500 return err;
501 }
502
503 hw_breakpoint_copy_attr(&bp->attr, attr);
504 bp->hw.info = hw;
505
506 return 0;
507}
508
509/**
510 * modify_user_hw_breakpoint - modify a user-space hardware breakpoint
511 * @bp: the breakpoint structure to modify
512 * @attr: new breakpoint attributes
513 */
514int modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *attr)
515{
516 int err;
517
518 /*
519 * modify_user_hw_breakpoint can be invoked with IRQs disabled and hence it
520 * will not be possible to raise IPIs that invoke __perf_event_disable.
521 * So call the function directly after making sure we are targeting the
522 * current task.
523 */
524 if (irqs_disabled() && bp->ctx && bp->ctx->task == current)
525 perf_event_disable_local(bp);
526 else
527 perf_event_disable(bp);
528
529 err = modify_user_hw_breakpoint_check(bp, attr, false);
530
531 if (!bp->attr.disabled)
532 perf_event_enable(bp);
533
534 return err;
535}
536EXPORT_SYMBOL_GPL(modify_user_hw_breakpoint);
537
538/**
539 * unregister_hw_breakpoint - unregister a user-space hardware breakpoint
540 * @bp: the breakpoint structure to unregister
541 */
542void unregister_hw_breakpoint(struct perf_event *bp)
543{
544 if (!bp)
545 return;
546 perf_event_release_kernel(bp);
547}
548EXPORT_SYMBOL_GPL(unregister_hw_breakpoint);
549
550/**
551 * register_wide_hw_breakpoint - register a wide breakpoint in the kernel
552 * @attr: breakpoint attributes
553 * @triggered: callback to trigger when we hit the breakpoint
554 * @context: context data could be used in the triggered callback
555 *
556 * @return a set of per_cpu pointers to perf events
557 */
558struct perf_event * __percpu *
559register_wide_hw_breakpoint(struct perf_event_attr *attr,
560 perf_overflow_handler_t triggered,
561 void *context)
562{
563 struct perf_event * __percpu *cpu_events, *bp;
564 long err = 0;
565 int cpu;
566
567 cpu_events = alloc_percpu(typeof(*cpu_events));
568 if (!cpu_events)
569 return (void __percpu __force *)ERR_PTR(-ENOMEM);
570
571 get_online_cpus();
572 for_each_online_cpu(cpu) {
573 bp = perf_event_create_kernel_counter(attr, cpu, NULL,
574 triggered, context);
575 if (IS_ERR(bp)) {
576 err = PTR_ERR(bp);
577 break;
578 }
579
580 per_cpu(*cpu_events, cpu) = bp;
581 }
582 put_online_cpus();
583
584 if (likely(!err))
585 return cpu_events;
586
587 unregister_wide_hw_breakpoint(cpu_events);
588 return (void __percpu __force *)ERR_PTR(err);
589}
590EXPORT_SYMBOL_GPL(register_wide_hw_breakpoint);
591
592/**
593 * unregister_wide_hw_breakpoint - unregister a wide breakpoint in the kernel
594 * @cpu_events: the per cpu set of events to unregister
595 */
596void unregister_wide_hw_breakpoint(struct perf_event * __percpu *cpu_events)
597{
598 int cpu;
599
600 for_each_possible_cpu(cpu)
601 unregister_hw_breakpoint(per_cpu(*cpu_events, cpu));
602
603 free_percpu(cpu_events);
604}
605EXPORT_SYMBOL_GPL(unregister_wide_hw_breakpoint);
606
607static struct notifier_block hw_breakpoint_exceptions_nb = {
608 .notifier_call = hw_breakpoint_exceptions_notify,
609 /* we need to be notified first */
610 .priority = 0x7fffffff
611};
612
613static void bp_perf_event_destroy(struct perf_event *event)
614{
615 release_bp_slot(event);
616}
617
618static int hw_breakpoint_event_init(struct perf_event *bp)
619{
620 int err;
621
622 if (bp->attr.type != PERF_TYPE_BREAKPOINT)
623 return -ENOENT;
624
625 /*
626 * no branch sampling for breakpoint events
627 */
628 if (has_branch_stack(bp))
629 return -EOPNOTSUPP;
630
631 err = register_perf_hw_breakpoint(bp);
632 if (err)
633 return err;
634
635 bp->destroy = bp_perf_event_destroy;
636
637 return 0;
638}
639
640static int hw_breakpoint_add(struct perf_event *bp, int flags)
641{
642 if (!(flags & PERF_EF_START))
643 bp->hw.state = PERF_HES_STOPPED;
644
645 if (is_sampling_event(bp)) {
646 bp->hw.last_period = bp->hw.sample_period;
647 perf_swevent_set_period(bp);
648 }
649
650 return arch_install_hw_breakpoint(bp);
651}
652
653static void hw_breakpoint_del(struct perf_event *bp, int flags)
654{
655 arch_uninstall_hw_breakpoint(bp);
656}
657
658static void hw_breakpoint_start(struct perf_event *bp, int flags)
659{
660 bp->hw.state = 0;
661}
662
663static void hw_breakpoint_stop(struct perf_event *bp, int flags)
664{
665 bp->hw.state = PERF_HES_STOPPED;
666}
667
668static struct pmu perf_breakpoint = {
669 .task_ctx_nr = perf_sw_context, /* could eventually get its own */
670
671 .event_init = hw_breakpoint_event_init,
672 .add = hw_breakpoint_add,
673 .del = hw_breakpoint_del,
674 .start = hw_breakpoint_start,
675 .stop = hw_breakpoint_stop,
676 .read = hw_breakpoint_pmu_read,
677};
678
679int __init init_hw_breakpoint(void)
680{
681 int cpu, err_cpu;
682 int i;
683
684 for (i = 0; i < TYPE_MAX; i++)
685 nr_slots[i] = hw_breakpoint_slots(i);
686
687 for_each_possible_cpu(cpu) {
688 for (i = 0; i < TYPE_MAX; i++) {
689 struct bp_cpuinfo *info = get_bp_info(cpu, i);
690
691 info->tsk_pinned = kcalloc(nr_slots[i], sizeof(int),
692 GFP_KERNEL);
693 if (!info->tsk_pinned)
694 goto err_alloc;
695 }
696 }
697
698 constraints_initialized = 1;
699
700 perf_pmu_register(&perf_breakpoint, "breakpoint", PERF_TYPE_BREAKPOINT);
701
702 return register_die_notifier(&hw_breakpoint_exceptions_nb);
703
704 err_alloc:
705 for_each_possible_cpu(err_cpu) {
706 for (i = 0; i < TYPE_MAX; i++)
707 kfree(get_bp_info(err_cpu, i)->tsk_pinned);
708 if (err_cpu == cpu)
709 break;
710 }
711
712 return -ENOMEM;
713}
714
715