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