1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * HW_breakpoint: a unified kernel/user-space hardware breakpoint facility,
4  * using the CPU's debug registers. Derived from
5  * "arch/x86/kernel/hw_breakpoint.c"
6  *
7  * Copyright 2010 IBM Corporation
8  * Author: K.Prasad <prasad@linux.vnet.ibm.com>
9  */
10 
11 #include <linux/hw_breakpoint.h>
12 #include <linux/notifier.h>
13 #include <linux/kprobes.h>
14 #include <linux/percpu.h>
15 #include <linux/kernel.h>
16 #include <linux/sched.h>
17 #include <linux/smp.h>
18 #include <linux/debugfs.h>
19 #include <linux/init.h>
20 
21 #include <asm/hw_breakpoint.h>
22 #include <asm/processor.h>
23 #include <asm/sstep.h>
24 #include <asm/debug.h>
25 #include <asm/hvcall.h>
26 #include <asm/inst.h>
27 #include <linux/uaccess.h>
28 
29 /*
30  * Stores the breakpoints currently in use on each breakpoint address
31  * register for every cpu
32  */
33 static DEFINE_PER_CPU(struct perf_event *, bp_per_reg[HBP_NUM_MAX]);
34 
35 /*
36  * Returns total number of data or instruction breakpoints available.
37  */
38 int hw_breakpoint_slots(int type)
39 {
40 	if (type == TYPE_DATA)
41 		return nr_wp_slots();
42 	return 0;		/* no instruction breakpoints available */
43 }
44 
45 static bool single_step_pending(void)
46 {
47 	int i;
48 
49 	for (i = 0; i < nr_wp_slots(); i++) {
50 		if (current->thread.last_hit_ubp[i])
51 			return true;
52 	}
53 	return false;
54 }
55 
56 /*
57  * Install a perf counter breakpoint.
58  *
59  * We seek a free debug address register and use it for this
60  * breakpoint.
61  *
62  * Atomic: we hold the counter->ctx->lock and we only handle variables
63  * and registers local to this cpu.
64  */
65 int arch_install_hw_breakpoint(struct perf_event *bp)
66 {
67 	struct arch_hw_breakpoint *info = counter_arch_bp(bp);
68 	struct perf_event **slot;
69 	int i;
70 
71 	for (i = 0; i < nr_wp_slots(); i++) {
72 		slot = this_cpu_ptr(&bp_per_reg[i]);
73 		if (!*slot) {
74 			*slot = bp;
75 			break;
76 		}
77 	}
78 
79 	if (WARN_ONCE(i == nr_wp_slots(), "Can't find any breakpoint slot"))
80 		return -EBUSY;
81 
82 	/*
83 	 * Do not install DABR values if the instruction must be single-stepped.
84 	 * If so, DABR will be populated in single_step_dabr_instruction().
85 	 */
86 	if (!single_step_pending())
87 		__set_breakpoint(i, info);
88 
89 	return 0;
90 }
91 
92 /*
93  * Uninstall the breakpoint contained in the given counter.
94  *
95  * First we search the debug address register it uses and then we disable
96  * it.
97  *
98  * Atomic: we hold the counter->ctx->lock and we only handle variables
99  * and registers local to this cpu.
100  */
101 void arch_uninstall_hw_breakpoint(struct perf_event *bp)
102 {
103 	struct arch_hw_breakpoint null_brk = {0};
104 	struct perf_event **slot;
105 	int i;
106 
107 	for (i = 0; i < nr_wp_slots(); i++) {
108 		slot = this_cpu_ptr(&bp_per_reg[i]);
109 		if (*slot == bp) {
110 			*slot = NULL;
111 			break;
112 		}
113 	}
114 
115 	if (WARN_ONCE(i == nr_wp_slots(), "Can't find any breakpoint slot"))
116 		return;
117 
118 	__set_breakpoint(i, &null_brk);
119 }
120 
121 static bool is_ptrace_bp(struct perf_event *bp)
122 {
123 	return bp->overflow_handler == ptrace_triggered;
124 }
125 
126 struct breakpoint {
127 	struct list_head list;
128 	struct perf_event *bp;
129 	bool ptrace_bp;
130 };
131 
132 static DEFINE_PER_CPU(struct breakpoint *, cpu_bps[HBP_NUM_MAX]);
133 static LIST_HEAD(task_bps);
134 
135 static struct breakpoint *alloc_breakpoint(struct perf_event *bp)
136 {
137 	struct breakpoint *tmp;
138 
139 	tmp = kzalloc(sizeof(*tmp), GFP_KERNEL);
140 	if (!tmp)
141 		return ERR_PTR(-ENOMEM);
142 	tmp->bp = bp;
143 	tmp->ptrace_bp = is_ptrace_bp(bp);
144 	return tmp;
145 }
146 
147 static bool bp_addr_range_overlap(struct perf_event *bp1, struct perf_event *bp2)
148 {
149 	__u64 bp1_saddr, bp1_eaddr, bp2_saddr, bp2_eaddr;
150 
151 	bp1_saddr = ALIGN_DOWN(bp1->attr.bp_addr, HW_BREAKPOINT_SIZE);
152 	bp1_eaddr = ALIGN(bp1->attr.bp_addr + bp1->attr.bp_len, HW_BREAKPOINT_SIZE);
153 	bp2_saddr = ALIGN_DOWN(bp2->attr.bp_addr, HW_BREAKPOINT_SIZE);
154 	bp2_eaddr = ALIGN(bp2->attr.bp_addr + bp2->attr.bp_len, HW_BREAKPOINT_SIZE);
155 
156 	return (bp1_saddr < bp2_eaddr && bp1_eaddr > bp2_saddr);
157 }
158 
159 static bool alternate_infra_bp(struct breakpoint *b, struct perf_event *bp)
160 {
161 	return is_ptrace_bp(bp) ? !b->ptrace_bp : b->ptrace_bp;
162 }
163 
164 static bool can_co_exist(struct breakpoint *b, struct perf_event *bp)
165 {
166 	return !(alternate_infra_bp(b, bp) && bp_addr_range_overlap(b->bp, bp));
167 }
168 
169 static int task_bps_add(struct perf_event *bp)
170 {
171 	struct breakpoint *tmp;
172 
173 	tmp = alloc_breakpoint(bp);
174 	if (IS_ERR(tmp))
175 		return PTR_ERR(tmp);
176 
177 	list_add(&tmp->list, &task_bps);
178 	return 0;
179 }
180 
181 static void task_bps_remove(struct perf_event *bp)
182 {
183 	struct list_head *pos, *q;
184 
185 	list_for_each_safe(pos, q, &task_bps) {
186 		struct breakpoint *tmp = list_entry(pos, struct breakpoint, list);
187 
188 		if (tmp->bp == bp) {
189 			list_del(&tmp->list);
190 			kfree(tmp);
191 			break;
192 		}
193 	}
194 }
195 
196 /*
197  * If any task has breakpoint from alternate infrastructure,
198  * return true. Otherwise return false.
199  */
200 static bool all_task_bps_check(struct perf_event *bp)
201 {
202 	struct breakpoint *tmp;
203 
204 	list_for_each_entry(tmp, &task_bps, list) {
205 		if (!can_co_exist(tmp, bp))
206 			return true;
207 	}
208 	return false;
209 }
210 
211 /*
212  * If same task has breakpoint from alternate infrastructure,
213  * return true. Otherwise return false.
214  */
215 static bool same_task_bps_check(struct perf_event *bp)
216 {
217 	struct breakpoint *tmp;
218 
219 	list_for_each_entry(tmp, &task_bps, list) {
220 		if (tmp->bp->hw.target == bp->hw.target &&
221 		    !can_co_exist(tmp, bp))
222 			return true;
223 	}
224 	return false;
225 }
226 
227 static int cpu_bps_add(struct perf_event *bp)
228 {
229 	struct breakpoint **cpu_bp;
230 	struct breakpoint *tmp;
231 	int i = 0;
232 
233 	tmp = alloc_breakpoint(bp);
234 	if (IS_ERR(tmp))
235 		return PTR_ERR(tmp);
236 
237 	cpu_bp = per_cpu_ptr(cpu_bps, bp->cpu);
238 	for (i = 0; i < nr_wp_slots(); i++) {
239 		if (!cpu_bp[i]) {
240 			cpu_bp[i] = tmp;
241 			break;
242 		}
243 	}
244 	return 0;
245 }
246 
247 static void cpu_bps_remove(struct perf_event *bp)
248 {
249 	struct breakpoint **cpu_bp;
250 	int i = 0;
251 
252 	cpu_bp = per_cpu_ptr(cpu_bps, bp->cpu);
253 	for (i = 0; i < nr_wp_slots(); i++) {
254 		if (!cpu_bp[i])
255 			continue;
256 
257 		if (cpu_bp[i]->bp == bp) {
258 			kfree(cpu_bp[i]);
259 			cpu_bp[i] = NULL;
260 			break;
261 		}
262 	}
263 }
264 
265 static bool cpu_bps_check(int cpu, struct perf_event *bp)
266 {
267 	struct breakpoint **cpu_bp;
268 	int i;
269 
270 	cpu_bp = per_cpu_ptr(cpu_bps, cpu);
271 	for (i = 0; i < nr_wp_slots(); i++) {
272 		if (cpu_bp[i] && !can_co_exist(cpu_bp[i], bp))
273 			return true;
274 	}
275 	return false;
276 }
277 
278 static bool all_cpu_bps_check(struct perf_event *bp)
279 {
280 	int cpu;
281 
282 	for_each_online_cpu(cpu) {
283 		if (cpu_bps_check(cpu, bp))
284 			return true;
285 	}
286 	return false;
287 }
288 
289 /*
290  * We don't use any locks to serialize accesses to cpu_bps or task_bps
291  * because are already inside nr_bp_mutex.
292  */
293 int arch_reserve_bp_slot(struct perf_event *bp)
294 {
295 	int ret;
296 
297 	/* ptrace breakpoint */
298 	if (is_ptrace_bp(bp)) {
299 		if (all_cpu_bps_check(bp))
300 			return -ENOSPC;
301 
302 		if (same_task_bps_check(bp))
303 			return -ENOSPC;
304 
305 		return task_bps_add(bp);
306 	}
307 
308 	/* perf breakpoint */
309 	if (is_kernel_addr(bp->attr.bp_addr))
310 		return 0;
311 
312 	if (bp->hw.target && bp->cpu == -1) {
313 		if (same_task_bps_check(bp))
314 			return -ENOSPC;
315 
316 		return task_bps_add(bp);
317 	} else if (!bp->hw.target && bp->cpu != -1) {
318 		if (all_task_bps_check(bp))
319 			return -ENOSPC;
320 
321 		return cpu_bps_add(bp);
322 	}
323 
324 	if (same_task_bps_check(bp))
325 		return -ENOSPC;
326 
327 	ret = cpu_bps_add(bp);
328 	if (ret)
329 		return ret;
330 	ret = task_bps_add(bp);
331 	if (ret)
332 		cpu_bps_remove(bp);
333 
334 	return ret;
335 }
336 
337 void arch_release_bp_slot(struct perf_event *bp)
338 {
339 	if (!is_kernel_addr(bp->attr.bp_addr)) {
340 		if (bp->hw.target)
341 			task_bps_remove(bp);
342 		if (bp->cpu != -1)
343 			cpu_bps_remove(bp);
344 	}
345 }
346 
347 /*
348  * Perform cleanup of arch-specific counters during unregistration
349  * of the perf-event
350  */
351 void arch_unregister_hw_breakpoint(struct perf_event *bp)
352 {
353 	/*
354 	 * If the breakpoint is unregistered between a hw_breakpoint_handler()
355 	 * and the single_step_dabr_instruction(), then cleanup the breakpoint
356 	 * restoration variables to prevent dangling pointers.
357 	 * FIXME, this should not be using bp->ctx at all! Sayeth peterz.
358 	 */
359 	if (bp->ctx && bp->ctx->task && bp->ctx->task != ((void *)-1L)) {
360 		int i;
361 
362 		for (i = 0; i < nr_wp_slots(); i++) {
363 			if (bp->ctx->task->thread.last_hit_ubp[i] == bp)
364 				bp->ctx->task->thread.last_hit_ubp[i] = NULL;
365 		}
366 	}
367 }
368 
369 /*
370  * Check for virtual address in kernel space.
371  */
372 int arch_check_bp_in_kernelspace(struct arch_hw_breakpoint *hw)
373 {
374 	return is_kernel_addr(hw->address);
375 }
376 
377 int arch_bp_generic_fields(int type, int *gen_bp_type)
378 {
379 	*gen_bp_type = 0;
380 	if (type & HW_BRK_TYPE_READ)
381 		*gen_bp_type |= HW_BREAKPOINT_R;
382 	if (type & HW_BRK_TYPE_WRITE)
383 		*gen_bp_type |= HW_BREAKPOINT_W;
384 	if (*gen_bp_type == 0)
385 		return -EINVAL;
386 	return 0;
387 }
388 
389 /*
390  * Watchpoint match range is always doubleword(8 bytes) aligned on
391  * powerpc. If the given range is crossing doubleword boundary, we
392  * need to increase the length such that next doubleword also get
393  * covered. Ex,
394  *
395  *          address   len = 6 bytes
396  *                |=========.
397  *   |------------v--|------v--------|
398  *   | | | | | | | | | | | | | | | | |
399  *   |---------------|---------------|
400  *    <---8 bytes--->
401  *
402  * In this case, we should configure hw as:
403  *   start_addr = address & ~(HW_BREAKPOINT_SIZE - 1)
404  *   len = 16 bytes
405  *
406  * @start_addr is inclusive but @end_addr is exclusive.
407  */
408 static int hw_breakpoint_validate_len(struct arch_hw_breakpoint *hw)
409 {
410 	u16 max_len = DABR_MAX_LEN;
411 	u16 hw_len;
412 	unsigned long start_addr, end_addr;
413 
414 	start_addr = ALIGN_DOWN(hw->address, HW_BREAKPOINT_SIZE);
415 	end_addr = ALIGN(hw->address + hw->len, HW_BREAKPOINT_SIZE);
416 	hw_len = end_addr - start_addr;
417 
418 	if (dawr_enabled()) {
419 		max_len = DAWR_MAX_LEN;
420 		/* DAWR region can't cross 512 bytes boundary on p10 predecessors */
421 		if (!cpu_has_feature(CPU_FTR_ARCH_31) &&
422 		    (ALIGN_DOWN(start_addr, SZ_512) != ALIGN_DOWN(end_addr - 1, SZ_512)))
423 			return -EINVAL;
424 	} else if (IS_ENABLED(CONFIG_PPC_8xx)) {
425 		/* 8xx can setup a range without limitation */
426 		max_len = U16_MAX;
427 	}
428 
429 	if (hw_len > max_len)
430 		return -EINVAL;
431 
432 	hw->hw_len = hw_len;
433 	return 0;
434 }
435 
436 /*
437  * Validate the arch-specific HW Breakpoint register settings
438  */
439 int hw_breakpoint_arch_parse(struct perf_event *bp,
440 			     const struct perf_event_attr *attr,
441 			     struct arch_hw_breakpoint *hw)
442 {
443 	int ret = -EINVAL;
444 
445 	if (!bp || !attr->bp_len)
446 		return ret;
447 
448 	hw->type = HW_BRK_TYPE_TRANSLATE;
449 	if (attr->bp_type & HW_BREAKPOINT_R)
450 		hw->type |= HW_BRK_TYPE_READ;
451 	if (attr->bp_type & HW_BREAKPOINT_W)
452 		hw->type |= HW_BRK_TYPE_WRITE;
453 	if (hw->type == HW_BRK_TYPE_TRANSLATE)
454 		/* must set alteast read or write */
455 		return ret;
456 	if (!attr->exclude_user)
457 		hw->type |= HW_BRK_TYPE_USER;
458 	if (!attr->exclude_kernel)
459 		hw->type |= HW_BRK_TYPE_KERNEL;
460 	if (!attr->exclude_hv)
461 		hw->type |= HW_BRK_TYPE_HYP;
462 	hw->address = attr->bp_addr;
463 	hw->len = attr->bp_len;
464 
465 	if (!ppc_breakpoint_available())
466 		return -ENODEV;
467 
468 	return hw_breakpoint_validate_len(hw);
469 }
470 
471 /*
472  * Restores the breakpoint on the debug registers.
473  * Invoke this function if it is known that the execution context is
474  * about to change to cause loss of MSR_SE settings.
475  */
476 void thread_change_pc(struct task_struct *tsk, struct pt_regs *regs)
477 {
478 	struct arch_hw_breakpoint *info;
479 	int i;
480 
481 	for (i = 0; i < nr_wp_slots(); i++) {
482 		if (unlikely(tsk->thread.last_hit_ubp[i]))
483 			goto reset;
484 	}
485 	return;
486 
487 reset:
488 	regs_set_return_msr(regs, regs->msr & ~MSR_SE);
489 	for (i = 0; i < nr_wp_slots(); i++) {
490 		info = counter_arch_bp(__this_cpu_read(bp_per_reg[i]));
491 		__set_breakpoint(i, info);
492 		tsk->thread.last_hit_ubp[i] = NULL;
493 	}
494 }
495 
496 static bool is_larx_stcx_instr(int type)
497 {
498 	return type == LARX || type == STCX;
499 }
500 
501 static bool is_octword_vsx_instr(int type, int size)
502 {
503 	return ((type == LOAD_VSX || type == STORE_VSX) && size == 32);
504 }
505 
506 /*
507  * We've failed in reliably handling the hw-breakpoint. Unregister
508  * it and throw a warning message to let the user know about it.
509  */
510 static void handler_error(struct perf_event *bp, struct arch_hw_breakpoint *info)
511 {
512 	WARN(1, "Unable to handle hardware breakpoint. Breakpoint at 0x%lx will be disabled.",
513 	     info->address);
514 	perf_event_disable_inatomic(bp);
515 }
516 
517 static void larx_stcx_err(struct perf_event *bp, struct arch_hw_breakpoint *info)
518 {
519 	printk_ratelimited("Breakpoint hit on instruction that can't be emulated. Breakpoint at 0x%lx will be disabled.\n",
520 			   info->address);
521 	perf_event_disable_inatomic(bp);
522 }
523 
524 static bool stepping_handler(struct pt_regs *regs, struct perf_event **bp,
525 			     struct arch_hw_breakpoint **info, int *hit,
526 			     ppc_inst_t instr)
527 {
528 	int i;
529 	int stepped;
530 
531 	/* Do not emulate user-space instructions, instead single-step them */
532 	if (user_mode(regs)) {
533 		for (i = 0; i < nr_wp_slots(); i++) {
534 			if (!hit[i])
535 				continue;
536 			current->thread.last_hit_ubp[i] = bp[i];
537 			info[i] = NULL;
538 		}
539 		regs_set_return_msr(regs, regs->msr | MSR_SE);
540 		return false;
541 	}
542 
543 	stepped = emulate_step(regs, instr);
544 	if (!stepped) {
545 		for (i = 0; i < nr_wp_slots(); i++) {
546 			if (!hit[i])
547 				continue;
548 			handler_error(bp[i], info[i]);
549 			info[i] = NULL;
550 		}
551 		return false;
552 	}
553 	return true;
554 }
555 
556 static void handle_p10dd1_spurious_exception(struct arch_hw_breakpoint **info,
557 					     int *hit, unsigned long ea)
558 {
559 	int i;
560 	unsigned long hw_end_addr;
561 
562 	/*
563 	 * Handle spurious exception only when any bp_per_reg is set.
564 	 * Otherwise this might be created by xmon and not actually a
565 	 * spurious exception.
566 	 */
567 	for (i = 0; i < nr_wp_slots(); i++) {
568 		if (!info[i])
569 			continue;
570 
571 		hw_end_addr = ALIGN(info[i]->address + info[i]->len, HW_BREAKPOINT_SIZE);
572 
573 		/*
574 		 * Ending address of DAWR range is less than starting
575 		 * address of op.
576 		 */
577 		if ((hw_end_addr - 1) >= ea)
578 			continue;
579 
580 		/*
581 		 * Those addresses need to be in the same or in two
582 		 * consecutive 512B blocks;
583 		 */
584 		if (((hw_end_addr - 1) >> 10) != (ea >> 10))
585 			continue;
586 
587 		/*
588 		 * 'op address + 64B' generates an address that has a
589 		 * carry into bit 52 (crosses 2K boundary).
590 		 */
591 		if ((ea & 0x800) == ((ea + 64) & 0x800))
592 			continue;
593 
594 		break;
595 	}
596 
597 	if (i == nr_wp_slots())
598 		return;
599 
600 	for (i = 0; i < nr_wp_slots(); i++) {
601 		if (info[i]) {
602 			hit[i] = 1;
603 			info[i]->type |= HW_BRK_TYPE_EXTRANEOUS_IRQ;
604 		}
605 	}
606 }
607 
608 int hw_breakpoint_handler(struct die_args *args)
609 {
610 	bool err = false;
611 	int rc = NOTIFY_STOP;
612 	struct perf_event *bp[HBP_NUM_MAX] = { NULL };
613 	struct pt_regs *regs = args->regs;
614 	struct arch_hw_breakpoint *info[HBP_NUM_MAX] = { NULL };
615 	int i;
616 	int hit[HBP_NUM_MAX] = {0};
617 	int nr_hit = 0;
618 	bool ptrace_bp = false;
619 	ppc_inst_t instr = ppc_inst(0);
620 	int type = 0;
621 	int size = 0;
622 	unsigned long ea;
623 
624 	/* Disable breakpoints during exception handling */
625 	hw_breakpoint_disable();
626 
627 	/*
628 	 * The counter may be concurrently released but that can only
629 	 * occur from a call_rcu() path. We can then safely fetch
630 	 * the breakpoint, use its callback, touch its counter
631 	 * while we are in an rcu_read_lock() path.
632 	 */
633 	rcu_read_lock();
634 
635 	if (!IS_ENABLED(CONFIG_PPC_8xx))
636 		wp_get_instr_detail(regs, &instr, &type, &size, &ea);
637 
638 	for (i = 0; i < nr_wp_slots(); i++) {
639 		bp[i] = __this_cpu_read(bp_per_reg[i]);
640 		if (!bp[i])
641 			continue;
642 
643 		info[i] = counter_arch_bp(bp[i]);
644 		info[i]->type &= ~HW_BRK_TYPE_EXTRANEOUS_IRQ;
645 
646 		if (wp_check_constraints(regs, instr, ea, type, size, info[i])) {
647 			if (!IS_ENABLED(CONFIG_PPC_8xx) &&
648 			    ppc_inst_equal(instr, ppc_inst(0))) {
649 				handler_error(bp[i], info[i]);
650 				info[i] = NULL;
651 				err = 1;
652 				continue;
653 			}
654 
655 			if (is_ptrace_bp(bp[i]))
656 				ptrace_bp = true;
657 			hit[i] = 1;
658 			nr_hit++;
659 		}
660 	}
661 
662 	if (err)
663 		goto reset;
664 
665 	if (!nr_hit) {
666 		/* Workaround for Power10 DD1 */
667 		if (!IS_ENABLED(CONFIG_PPC_8xx) && mfspr(SPRN_PVR) == 0x800100 &&
668 		    is_octword_vsx_instr(type, size)) {
669 			handle_p10dd1_spurious_exception(info, hit, ea);
670 		} else {
671 			rc = NOTIFY_DONE;
672 			goto out;
673 		}
674 	}
675 
676 	/*
677 	 * Return early after invoking user-callback function without restoring
678 	 * DABR if the breakpoint is from ptrace which always operates in
679 	 * one-shot mode. The ptrace-ed process will receive the SIGTRAP signal
680 	 * generated in do_dabr().
681 	 */
682 	if (ptrace_bp) {
683 		for (i = 0; i < nr_wp_slots(); i++) {
684 			if (!hit[i])
685 				continue;
686 			perf_bp_event(bp[i], regs);
687 			info[i] = NULL;
688 		}
689 		rc = NOTIFY_DONE;
690 		goto reset;
691 	}
692 
693 	if (!IS_ENABLED(CONFIG_PPC_8xx)) {
694 		if (is_larx_stcx_instr(type)) {
695 			for (i = 0; i < nr_wp_slots(); i++) {
696 				if (!hit[i])
697 					continue;
698 				larx_stcx_err(bp[i], info[i]);
699 				info[i] = NULL;
700 			}
701 			goto reset;
702 		}
703 
704 		if (!stepping_handler(regs, bp, info, hit, instr))
705 			goto reset;
706 	}
707 
708 	/*
709 	 * As a policy, the callback is invoked in a 'trigger-after-execute'
710 	 * fashion
711 	 */
712 	for (i = 0; i < nr_wp_slots(); i++) {
713 		if (!hit[i])
714 			continue;
715 		if (!(info[i]->type & HW_BRK_TYPE_EXTRANEOUS_IRQ))
716 			perf_bp_event(bp[i], regs);
717 	}
718 
719 reset:
720 	for (i = 0; i < nr_wp_slots(); i++) {
721 		if (!info[i])
722 			continue;
723 		__set_breakpoint(i, info[i]);
724 	}
725 
726 out:
727 	rcu_read_unlock();
728 	return rc;
729 }
730 NOKPROBE_SYMBOL(hw_breakpoint_handler);
731 
732 /*
733  * Handle single-step exceptions following a DABR hit.
734  */
735 static int single_step_dabr_instruction(struct die_args *args)
736 {
737 	struct pt_regs *regs = args->regs;
738 	struct perf_event *bp = NULL;
739 	struct arch_hw_breakpoint *info;
740 	int i;
741 	bool found = false;
742 
743 	/*
744 	 * Check if we are single-stepping as a result of a
745 	 * previous HW Breakpoint exception
746 	 */
747 	for (i = 0; i < nr_wp_slots(); i++) {
748 		bp = current->thread.last_hit_ubp[i];
749 
750 		if (!bp)
751 			continue;
752 
753 		found = true;
754 		info = counter_arch_bp(bp);
755 
756 		/*
757 		 * We shall invoke the user-defined callback function in the
758 		 * single stepping handler to confirm to 'trigger-after-execute'
759 		 * semantics
760 		 */
761 		if (!(info->type & HW_BRK_TYPE_EXTRANEOUS_IRQ))
762 			perf_bp_event(bp, regs);
763 		current->thread.last_hit_ubp[i] = NULL;
764 	}
765 
766 	if (!found)
767 		return NOTIFY_DONE;
768 
769 	for (i = 0; i < nr_wp_slots(); i++) {
770 		bp = __this_cpu_read(bp_per_reg[i]);
771 		if (!bp)
772 			continue;
773 
774 		info = counter_arch_bp(bp);
775 		__set_breakpoint(i, info);
776 	}
777 
778 	/*
779 	 * If the process was being single-stepped by ptrace, let the
780 	 * other single-step actions occur (e.g. generate SIGTRAP).
781 	 */
782 	if (test_thread_flag(TIF_SINGLESTEP))
783 		return NOTIFY_DONE;
784 
785 	return NOTIFY_STOP;
786 }
787 NOKPROBE_SYMBOL(single_step_dabr_instruction);
788 
789 /*
790  * Handle debug exception notifications.
791  */
792 int hw_breakpoint_exceptions_notify(
793 		struct notifier_block *unused, unsigned long val, void *data)
794 {
795 	int ret = NOTIFY_DONE;
796 
797 	switch (val) {
798 	case DIE_DABR_MATCH:
799 		ret = hw_breakpoint_handler(data);
800 		break;
801 	case DIE_SSTEP:
802 		ret = single_step_dabr_instruction(data);
803 		break;
804 	}
805 
806 	return ret;
807 }
808 NOKPROBE_SYMBOL(hw_breakpoint_exceptions_notify);
809 
810 /*
811  * Release the user breakpoints used by ptrace
812  */
813 void flush_ptrace_hw_breakpoint(struct task_struct *tsk)
814 {
815 	int i;
816 	struct thread_struct *t = &tsk->thread;
817 
818 	for (i = 0; i < nr_wp_slots(); i++) {
819 		unregister_hw_breakpoint(t->ptrace_bps[i]);
820 		t->ptrace_bps[i] = NULL;
821 	}
822 }
823 
824 void hw_breakpoint_pmu_read(struct perf_event *bp)
825 {
826 	/* TODO */
827 }
828 
829 void ptrace_triggered(struct perf_event *bp,
830 		      struct perf_sample_data *data, struct pt_regs *regs)
831 {
832 	struct perf_event_attr attr;
833 
834 	/*
835 	 * Disable the breakpoint request here since ptrace has defined a
836 	 * one-shot behaviour for breakpoint exceptions in PPC64.
837 	 * The SIGTRAP signal is generated automatically for us in do_dabr().
838 	 * We don't have to do anything about that here
839 	 */
840 	attr = bp->attr;
841 	attr.disabled = true;
842 	modify_user_hw_breakpoint(bp, &attr);
843 }
844