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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 *
4 * Copyright (C) 2009, 2010 ARM Limited
5 *
6 * Author: Will Deacon <will.deacon@arm.com>
7 */
8
9/*
10 * HW_breakpoint: a unified kernel/user-space hardware breakpoint facility,
11 * using the CPU's debug registers.
12 */
13#define pr_fmt(fmt) "hw-breakpoint: " fmt
14
15#include <linux/errno.h>
16#include <linux/hardirq.h>
17#include <linux/perf_event.h>
18#include <linux/hw_breakpoint.h>
19#include <linux/smp.h>
20#include <linux/cpu_pm.h>
21#include <linux/coresight.h>
22
23#include <asm/cacheflush.h>
24#include <asm/cputype.h>
25#include <asm/current.h>
26#include <asm/hw_breakpoint.h>
27#include <asm/traps.h>
28
29/* Breakpoint currently in use for each BRP. */
30static DEFINE_PER_CPU(struct perf_event *, bp_on_reg[ARM_MAX_BRP]);
31
32/* Watchpoint currently in use for each WRP. */
33static DEFINE_PER_CPU(struct perf_event *, wp_on_reg[ARM_MAX_WRP]);
34
35/* Number of BRP/WRP registers on this CPU. */
36static int core_num_brps __ro_after_init;
37static int core_num_wrps __ro_after_init;
38
39/* Debug architecture version. */
40static u8 debug_arch __ro_after_init;
41
42/* Does debug architecture support OS Save and Restore? */
43static bool has_ossr __ro_after_init;
44
45/* Maximum supported watchpoint length. */
46static u8 max_watchpoint_len __ro_after_init;
47
48#define READ_WB_REG_CASE(OP2, M, VAL) \
49 case ((OP2 << 4) + M): \
50 ARM_DBG_READ(c0, c ## M, OP2, VAL); \
51 break
52
53#define WRITE_WB_REG_CASE(OP2, M, VAL) \
54 case ((OP2 << 4) + M): \
55 ARM_DBG_WRITE(c0, c ## M, OP2, VAL); \
56 break
57
58#define GEN_READ_WB_REG_CASES(OP2, VAL) \
59 READ_WB_REG_CASE(OP2, 0, VAL); \
60 READ_WB_REG_CASE(OP2, 1, VAL); \
61 READ_WB_REG_CASE(OP2, 2, VAL); \
62 READ_WB_REG_CASE(OP2, 3, VAL); \
63 READ_WB_REG_CASE(OP2, 4, VAL); \
64 READ_WB_REG_CASE(OP2, 5, VAL); \
65 READ_WB_REG_CASE(OP2, 6, VAL); \
66 READ_WB_REG_CASE(OP2, 7, VAL); \
67 READ_WB_REG_CASE(OP2, 8, VAL); \
68 READ_WB_REG_CASE(OP2, 9, VAL); \
69 READ_WB_REG_CASE(OP2, 10, VAL); \
70 READ_WB_REG_CASE(OP2, 11, VAL); \
71 READ_WB_REG_CASE(OP2, 12, VAL); \
72 READ_WB_REG_CASE(OP2, 13, VAL); \
73 READ_WB_REG_CASE(OP2, 14, VAL); \
74 READ_WB_REG_CASE(OP2, 15, VAL)
75
76#define GEN_WRITE_WB_REG_CASES(OP2, VAL) \
77 WRITE_WB_REG_CASE(OP2, 0, VAL); \
78 WRITE_WB_REG_CASE(OP2, 1, VAL); \
79 WRITE_WB_REG_CASE(OP2, 2, VAL); \
80 WRITE_WB_REG_CASE(OP2, 3, VAL); \
81 WRITE_WB_REG_CASE(OP2, 4, VAL); \
82 WRITE_WB_REG_CASE(OP2, 5, VAL); \
83 WRITE_WB_REG_CASE(OP2, 6, VAL); \
84 WRITE_WB_REG_CASE(OP2, 7, VAL); \
85 WRITE_WB_REG_CASE(OP2, 8, VAL); \
86 WRITE_WB_REG_CASE(OP2, 9, VAL); \
87 WRITE_WB_REG_CASE(OP2, 10, VAL); \
88 WRITE_WB_REG_CASE(OP2, 11, VAL); \
89 WRITE_WB_REG_CASE(OP2, 12, VAL); \
90 WRITE_WB_REG_CASE(OP2, 13, VAL); \
91 WRITE_WB_REG_CASE(OP2, 14, VAL); \
92 WRITE_WB_REG_CASE(OP2, 15, VAL)
93
94static u32 read_wb_reg(int n)
95{
96 u32 val = 0;
97
98 switch (n) {
99 GEN_READ_WB_REG_CASES(ARM_OP2_BVR, val);
100 GEN_READ_WB_REG_CASES(ARM_OP2_BCR, val);
101 GEN_READ_WB_REG_CASES(ARM_OP2_WVR, val);
102 GEN_READ_WB_REG_CASES(ARM_OP2_WCR, val);
103 default:
104 pr_warn("attempt to read from unknown breakpoint register %d\n",
105 n);
106 }
107
108 return val;
109}
110
111static void write_wb_reg(int n, u32 val)
112{
113 switch (n) {
114 GEN_WRITE_WB_REG_CASES(ARM_OP2_BVR, val);
115 GEN_WRITE_WB_REG_CASES(ARM_OP2_BCR, val);
116 GEN_WRITE_WB_REG_CASES(ARM_OP2_WVR, val);
117 GEN_WRITE_WB_REG_CASES(ARM_OP2_WCR, val);
118 default:
119 pr_warn("attempt to write to unknown breakpoint register %d\n",
120 n);
121 }
122 isb();
123}
124
125/* Determine debug architecture. */
126static u8 get_debug_arch(void)
127{
128 u32 didr;
129
130 /* Do we implement the extended CPUID interface? */
131 if (((read_cpuid_id() >> 16) & 0xf) != 0xf) {
132 pr_warn_once("CPUID feature registers not supported. "
133 "Assuming v6 debug is present.\n");
134 return ARM_DEBUG_ARCH_V6;
135 }
136
137 ARM_DBG_READ(c0, c0, 0, didr);
138 return (didr >> 16) & 0xf;
139}
140
141u8 arch_get_debug_arch(void)
142{
143 return debug_arch;
144}
145
146static int debug_arch_supported(void)
147{
148 u8 arch = get_debug_arch();
149
150 /* We don't support the memory-mapped interface. */
151 return (arch >= ARM_DEBUG_ARCH_V6 && arch <= ARM_DEBUG_ARCH_V7_ECP14) ||
152 arch >= ARM_DEBUG_ARCH_V7_1;
153}
154
155/* Can we determine the watchpoint access type from the fsr? */
156static int debug_exception_updates_fsr(void)
157{
158 return get_debug_arch() >= ARM_DEBUG_ARCH_V8;
159}
160
161/* Determine number of WRP registers available. */
162static int get_num_wrp_resources(void)
163{
164 u32 didr;
165 ARM_DBG_READ(c0, c0, 0, didr);
166 return ((didr >> 28) & 0xf) + 1;
167}
168
169/* Determine number of BRP registers available. */
170static int get_num_brp_resources(void)
171{
172 u32 didr;
173 ARM_DBG_READ(c0, c0, 0, didr);
174 return ((didr >> 24) & 0xf) + 1;
175}
176
177/* Does this core support mismatch breakpoints? */
178static int core_has_mismatch_brps(void)
179{
180 return (get_debug_arch() >= ARM_DEBUG_ARCH_V7_ECP14 &&
181 get_num_brp_resources() > 1);
182}
183
184/* Determine number of usable WRPs available. */
185static int get_num_wrps(void)
186{
187 /*
188 * On debug architectures prior to 7.1, when a watchpoint fires, the
189 * only way to work out which watchpoint it was is by disassembling
190 * the faulting instruction and working out the address of the memory
191 * access.
192 *
193 * Furthermore, we can only do this if the watchpoint was precise
194 * since imprecise watchpoints prevent us from calculating register
195 * based addresses.
196 *
197 * Providing we have more than 1 breakpoint register, we only report
198 * a single watchpoint register for the time being. This way, we always
199 * know which watchpoint fired. In the future we can either add a
200 * disassembler and address generation emulator, or we can insert a
201 * check to see if the DFAR is set on watchpoint exception entry
202 * [the ARM ARM states that the DFAR is UNKNOWN, but experience shows
203 * that it is set on some implementations].
204 */
205 if (get_debug_arch() < ARM_DEBUG_ARCH_V7_1)
206 return 1;
207
208 return get_num_wrp_resources();
209}
210
211/* Determine number of usable BRPs available. */
212static int get_num_brps(void)
213{
214 int brps = get_num_brp_resources();
215 return core_has_mismatch_brps() ? brps - 1 : brps;
216}
217
218/*
219 * In order to access the breakpoint/watchpoint control registers,
220 * we must be running in debug monitor mode. Unfortunately, we can
221 * be put into halting debug mode at any time by an external debugger
222 * but there is nothing we can do to prevent that.
223 */
224static int monitor_mode_enabled(void)
225{
226 u32 dscr;
227 ARM_DBG_READ(c0, c1, 0, dscr);
228 return !!(dscr & ARM_DSCR_MDBGEN);
229}
230
231static int enable_monitor_mode(void)
232{
233 u32 dscr;
234 ARM_DBG_READ(c0, c1, 0, dscr);
235
236 /* If monitor mode is already enabled, just return. */
237 if (dscr & ARM_DSCR_MDBGEN)
238 goto out;
239
240 /* Write to the corresponding DSCR. */
241 switch (get_debug_arch()) {
242 case ARM_DEBUG_ARCH_V6:
243 case ARM_DEBUG_ARCH_V6_1:
244 ARM_DBG_WRITE(c0, c1, 0, (dscr | ARM_DSCR_MDBGEN));
245 break;
246 case ARM_DEBUG_ARCH_V7_ECP14:
247 case ARM_DEBUG_ARCH_V7_1:
248 case ARM_DEBUG_ARCH_V8:
249 case ARM_DEBUG_ARCH_V8_1:
250 case ARM_DEBUG_ARCH_V8_2:
251 case ARM_DEBUG_ARCH_V8_4:
252 ARM_DBG_WRITE(c0, c2, 2, (dscr | ARM_DSCR_MDBGEN));
253 isb();
254 break;
255 default:
256 return -ENODEV;
257 }
258
259 /* Check that the write made it through. */
260 ARM_DBG_READ(c0, c1, 0, dscr);
261 if (!(dscr & ARM_DSCR_MDBGEN)) {
262 pr_warn_once("Failed to enable monitor mode on CPU %d.\n",
263 smp_processor_id());
264 return -EPERM;
265 }
266
267out:
268 return 0;
269}
270
271int hw_breakpoint_slots(int type)
272{
273 if (!debug_arch_supported())
274 return 0;
275
276 /*
277 * We can be called early, so don't rely on
278 * our static variables being initialised.
279 */
280 switch (type) {
281 case TYPE_INST:
282 return get_num_brps();
283 case TYPE_DATA:
284 return get_num_wrps();
285 default:
286 pr_warn("unknown slot type: %d\n", type);
287 return 0;
288 }
289}
290
291/*
292 * Check if 8-bit byte-address select is available.
293 * This clobbers WRP 0.
294 */
295static u8 get_max_wp_len(void)
296{
297 u32 ctrl_reg;
298 struct arch_hw_breakpoint_ctrl ctrl;
299 u8 size = 4;
300
301 if (debug_arch < ARM_DEBUG_ARCH_V7_ECP14)
302 goto out;
303
304 memset(&ctrl, 0, sizeof(ctrl));
305 ctrl.len = ARM_BREAKPOINT_LEN_8;
306 ctrl_reg = encode_ctrl_reg(ctrl);
307
308 write_wb_reg(ARM_BASE_WVR, 0);
309 write_wb_reg(ARM_BASE_WCR, ctrl_reg);
310 if ((read_wb_reg(ARM_BASE_WCR) & ctrl_reg) == ctrl_reg)
311 size = 8;
312
313out:
314 return size;
315}
316
317u8 arch_get_max_wp_len(void)
318{
319 return max_watchpoint_len;
320}
321
322/*
323 * Install a perf counter breakpoint.
324 */
325int arch_install_hw_breakpoint(struct perf_event *bp)
326{
327 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
328 struct perf_event **slot, **slots;
329 int i, max_slots, ctrl_base, val_base;
330 u32 addr, ctrl;
331
332 addr = info->address;
333 ctrl = encode_ctrl_reg(info->ctrl) | 0x1;
334
335 if (info->ctrl.type == ARM_BREAKPOINT_EXECUTE) {
336 /* Breakpoint */
337 ctrl_base = ARM_BASE_BCR;
338 val_base = ARM_BASE_BVR;
339 slots = this_cpu_ptr(bp_on_reg);
340 max_slots = core_num_brps;
341 } else {
342 /* Watchpoint */
343 ctrl_base = ARM_BASE_WCR;
344 val_base = ARM_BASE_WVR;
345 slots = this_cpu_ptr(wp_on_reg);
346 max_slots = core_num_wrps;
347 }
348
349 for (i = 0; i < max_slots; ++i) {
350 slot = &slots[i];
351
352 if (!*slot) {
353 *slot = bp;
354 break;
355 }
356 }
357
358 if (i == max_slots) {
359 pr_warn("Can't find any breakpoint slot\n");
360 return -EBUSY;
361 }
362
363 /* Override the breakpoint data with the step data. */
364 if (info->step_ctrl.enabled) {
365 addr = info->trigger & ~0x3;
366 ctrl = encode_ctrl_reg(info->step_ctrl);
367 if (info->ctrl.type != ARM_BREAKPOINT_EXECUTE) {
368 i = 0;
369 ctrl_base = ARM_BASE_BCR + core_num_brps;
370 val_base = ARM_BASE_BVR + core_num_brps;
371 }
372 }
373
374 /* Setup the address register. */
375 write_wb_reg(val_base + i, addr);
376
377 /* Setup the control register. */
378 write_wb_reg(ctrl_base + i, ctrl);
379 return 0;
380}
381
382void arch_uninstall_hw_breakpoint(struct perf_event *bp)
383{
384 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
385 struct perf_event **slot, **slots;
386 int i, max_slots, base;
387
388 if (info->ctrl.type == ARM_BREAKPOINT_EXECUTE) {
389 /* Breakpoint */
390 base = ARM_BASE_BCR;
391 slots = this_cpu_ptr(bp_on_reg);
392 max_slots = core_num_brps;
393 } else {
394 /* Watchpoint */
395 base = ARM_BASE_WCR;
396 slots = this_cpu_ptr(wp_on_reg);
397 max_slots = core_num_wrps;
398 }
399
400 /* Remove the breakpoint. */
401 for (i = 0; i < max_slots; ++i) {
402 slot = &slots[i];
403
404 if (*slot == bp) {
405 *slot = NULL;
406 break;
407 }
408 }
409
410 if (i == max_slots) {
411 pr_warn("Can't find any breakpoint slot\n");
412 return;
413 }
414
415 /* Ensure that we disable the mismatch breakpoint. */
416 if (info->ctrl.type != ARM_BREAKPOINT_EXECUTE &&
417 info->step_ctrl.enabled) {
418 i = 0;
419 base = ARM_BASE_BCR + core_num_brps;
420 }
421
422 /* Reset the control register. */
423 write_wb_reg(base + i, 0);
424}
425
426static int get_hbp_len(u8 hbp_len)
427{
428 unsigned int len_in_bytes = 0;
429
430 switch (hbp_len) {
431 case ARM_BREAKPOINT_LEN_1:
432 len_in_bytes = 1;
433 break;
434 case ARM_BREAKPOINT_LEN_2:
435 len_in_bytes = 2;
436 break;
437 case ARM_BREAKPOINT_LEN_4:
438 len_in_bytes = 4;
439 break;
440 case ARM_BREAKPOINT_LEN_8:
441 len_in_bytes = 8;
442 break;
443 }
444
445 return len_in_bytes;
446}
447
448/*
449 * Check whether bp virtual address is in kernel space.
450 */
451int arch_check_bp_in_kernelspace(struct arch_hw_breakpoint *hw)
452{
453 unsigned int len;
454 unsigned long va;
455
456 va = hw->address;
457 len = get_hbp_len(hw->ctrl.len);
458
459 return (va >= TASK_SIZE) && ((va + len - 1) >= TASK_SIZE);
460}
461
462/*
463 * Extract generic type and length encodings from an arch_hw_breakpoint_ctrl.
464 * Hopefully this will disappear when ptrace can bypass the conversion
465 * to generic breakpoint descriptions.
466 */
467int arch_bp_generic_fields(struct arch_hw_breakpoint_ctrl ctrl,
468 int *gen_len, int *gen_type)
469{
470 /* Type */
471 switch (ctrl.type) {
472 case ARM_BREAKPOINT_EXECUTE:
473 *gen_type = HW_BREAKPOINT_X;
474 break;
475 case ARM_BREAKPOINT_LOAD:
476 *gen_type = HW_BREAKPOINT_R;
477 break;
478 case ARM_BREAKPOINT_STORE:
479 *gen_type = HW_BREAKPOINT_W;
480 break;
481 case ARM_BREAKPOINT_LOAD | ARM_BREAKPOINT_STORE:
482 *gen_type = HW_BREAKPOINT_RW;
483 break;
484 default:
485 return -EINVAL;
486 }
487
488 /* Len */
489 switch (ctrl.len) {
490 case ARM_BREAKPOINT_LEN_1:
491 *gen_len = HW_BREAKPOINT_LEN_1;
492 break;
493 case ARM_BREAKPOINT_LEN_2:
494 *gen_len = HW_BREAKPOINT_LEN_2;
495 break;
496 case ARM_BREAKPOINT_LEN_4:
497 *gen_len = HW_BREAKPOINT_LEN_4;
498 break;
499 case ARM_BREAKPOINT_LEN_8:
500 *gen_len = HW_BREAKPOINT_LEN_8;
501 break;
502 default:
503 return -EINVAL;
504 }
505
506 return 0;
507}
508
509/*
510 * Construct an arch_hw_breakpoint from a perf_event.
511 */
512static int arch_build_bp_info(struct perf_event *bp,
513 const struct perf_event_attr *attr,
514 struct arch_hw_breakpoint *hw)
515{
516 /* Type */
517 switch (attr->bp_type) {
518 case HW_BREAKPOINT_X:
519 hw->ctrl.type = ARM_BREAKPOINT_EXECUTE;
520 break;
521 case HW_BREAKPOINT_R:
522 hw->ctrl.type = ARM_BREAKPOINT_LOAD;
523 break;
524 case HW_BREAKPOINT_W:
525 hw->ctrl.type = ARM_BREAKPOINT_STORE;
526 break;
527 case HW_BREAKPOINT_RW:
528 hw->ctrl.type = ARM_BREAKPOINT_LOAD | ARM_BREAKPOINT_STORE;
529 break;
530 default:
531 return -EINVAL;
532 }
533
534 /* Len */
535 switch (attr->bp_len) {
536 case HW_BREAKPOINT_LEN_1:
537 hw->ctrl.len = ARM_BREAKPOINT_LEN_1;
538 break;
539 case HW_BREAKPOINT_LEN_2:
540 hw->ctrl.len = ARM_BREAKPOINT_LEN_2;
541 break;
542 case HW_BREAKPOINT_LEN_4:
543 hw->ctrl.len = ARM_BREAKPOINT_LEN_4;
544 break;
545 case HW_BREAKPOINT_LEN_8:
546 hw->ctrl.len = ARM_BREAKPOINT_LEN_8;
547 if ((hw->ctrl.type != ARM_BREAKPOINT_EXECUTE)
548 && max_watchpoint_len >= 8)
549 break;
550 fallthrough;
551 default:
552 return -EINVAL;
553 }
554
555 /*
556 * Breakpoints must be of length 2 (thumb) or 4 (ARM) bytes.
557 * Watchpoints can be of length 1, 2, 4 or 8 bytes if supported
558 * by the hardware and must be aligned to the appropriate number of
559 * bytes.
560 */
561 if (hw->ctrl.type == ARM_BREAKPOINT_EXECUTE &&
562 hw->ctrl.len != ARM_BREAKPOINT_LEN_2 &&
563 hw->ctrl.len != ARM_BREAKPOINT_LEN_4)
564 return -EINVAL;
565
566 /* Address */
567 hw->address = attr->bp_addr;
568
569 /* Privilege */
570 hw->ctrl.privilege = ARM_BREAKPOINT_USER;
571 if (arch_check_bp_in_kernelspace(hw))
572 hw->ctrl.privilege |= ARM_BREAKPOINT_PRIV;
573
574 /* Enabled? */
575 hw->ctrl.enabled = !attr->disabled;
576
577 /* Mismatch */
578 hw->ctrl.mismatch = 0;
579
580 return 0;
581}
582
583/*
584 * Validate the arch-specific HW Breakpoint register settings.
585 */
586int hw_breakpoint_arch_parse(struct perf_event *bp,
587 const struct perf_event_attr *attr,
588 struct arch_hw_breakpoint *hw)
589{
590 int ret = 0;
591 u32 offset, alignment_mask = 0x3;
592
593 /* Ensure that we are in monitor debug mode. */
594 if (!monitor_mode_enabled())
595 return -ENODEV;
596
597 /* Build the arch_hw_breakpoint. */
598 ret = arch_build_bp_info(bp, attr, hw);
599 if (ret)
600 goto out;
601
602 /* Check address alignment. */
603 if (hw->ctrl.len == ARM_BREAKPOINT_LEN_8)
604 alignment_mask = 0x7;
605 offset = hw->address & alignment_mask;
606 switch (offset) {
607 case 0:
608 /* Aligned */
609 break;
610 case 1:
611 case 2:
612 /* Allow halfword watchpoints and breakpoints. */
613 if (hw->ctrl.len == ARM_BREAKPOINT_LEN_2)
614 break;
615 fallthrough;
616 case 3:
617 /* Allow single byte watchpoint. */
618 if (hw->ctrl.len == ARM_BREAKPOINT_LEN_1)
619 break;
620 fallthrough;
621 default:
622 ret = -EINVAL;
623 goto out;
624 }
625
626 hw->address &= ~alignment_mask;
627 hw->ctrl.len <<= offset;
628
629 if (is_default_overflow_handler(bp)) {
630 /*
631 * Mismatch breakpoints are required for single-stepping
632 * breakpoints.
633 */
634 if (!core_has_mismatch_brps())
635 return -EINVAL;
636
637 /* We don't allow mismatch breakpoints in kernel space. */
638 if (arch_check_bp_in_kernelspace(hw))
639 return -EPERM;
640
641 /*
642 * Per-cpu breakpoints are not supported by our stepping
643 * mechanism.
644 */
645 if (!bp->hw.target)
646 return -EINVAL;
647
648 /*
649 * We only support specific access types if the fsr
650 * reports them.
651 */
652 if (!debug_exception_updates_fsr() &&
653 (hw->ctrl.type == ARM_BREAKPOINT_LOAD ||
654 hw->ctrl.type == ARM_BREAKPOINT_STORE))
655 return -EINVAL;
656 }
657
658out:
659 return ret;
660}
661
662/*
663 * Enable/disable single-stepping over the breakpoint bp at address addr.
664 */
665static void enable_single_step(struct perf_event *bp, u32 addr)
666{
667 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
668
669 arch_uninstall_hw_breakpoint(bp);
670 info->step_ctrl.mismatch = 1;
671 info->step_ctrl.len = ARM_BREAKPOINT_LEN_4;
672 info->step_ctrl.type = ARM_BREAKPOINT_EXECUTE;
673 info->step_ctrl.privilege = info->ctrl.privilege;
674 info->step_ctrl.enabled = 1;
675 info->trigger = addr;
676 arch_install_hw_breakpoint(bp);
677}
678
679static void disable_single_step(struct perf_event *bp)
680{
681 arch_uninstall_hw_breakpoint(bp);
682 counter_arch_bp(bp)->step_ctrl.enabled = 0;
683 arch_install_hw_breakpoint(bp);
684}
685
686static int watchpoint_fault_on_uaccess(struct pt_regs *regs,
687 struct arch_hw_breakpoint *info)
688{
689 return !user_mode(regs) && info->ctrl.privilege == ARM_BREAKPOINT_USER;
690}
691
692static void watchpoint_handler(unsigned long addr, unsigned int fsr,
693 struct pt_regs *regs)
694{
695 int i, access;
696 u32 val, ctrl_reg, alignment_mask;
697 struct perf_event *wp, **slots;
698 struct arch_hw_breakpoint *info;
699 struct arch_hw_breakpoint_ctrl ctrl;
700
701 slots = this_cpu_ptr(wp_on_reg);
702
703 for (i = 0; i < core_num_wrps; ++i) {
704 rcu_read_lock();
705
706 wp = slots[i];
707
708 if (wp == NULL)
709 goto unlock;
710
711 info = counter_arch_bp(wp);
712 /*
713 * The DFAR is an unknown value on debug architectures prior
714 * to 7.1. Since we only allow a single watchpoint on these
715 * older CPUs, we can set the trigger to the lowest possible
716 * faulting address.
717 */
718 if (debug_arch < ARM_DEBUG_ARCH_V7_1) {
719 BUG_ON(i > 0);
720 info->trigger = wp->attr.bp_addr;
721 } else {
722 if (info->ctrl.len == ARM_BREAKPOINT_LEN_8)
723 alignment_mask = 0x7;
724 else
725 alignment_mask = 0x3;
726
727 /* Check if the watchpoint value matches. */
728 val = read_wb_reg(ARM_BASE_WVR + i);
729 if (val != (addr & ~alignment_mask))
730 goto unlock;
731
732 /* Possible match, check the byte address select. */
733 ctrl_reg = read_wb_reg(ARM_BASE_WCR + i);
734 decode_ctrl_reg(ctrl_reg, &ctrl);
735 if (!((1 << (addr & alignment_mask)) & ctrl.len))
736 goto unlock;
737
738 /* Check that the access type matches. */
739 if (debug_exception_updates_fsr()) {
740 access = (fsr & ARM_FSR_ACCESS_MASK) ?
741 HW_BREAKPOINT_W : HW_BREAKPOINT_R;
742 if (!(access & hw_breakpoint_type(wp)))
743 goto unlock;
744 }
745
746 /* We have a winner. */
747 info->trigger = addr;
748 }
749
750 pr_debug("watchpoint fired: address = 0x%x\n", info->trigger);
751
752 /*
753 * If we triggered a user watchpoint from a uaccess routine,
754 * then handle the stepping ourselves since userspace really
755 * can't help us with this.
756 */
757 if (watchpoint_fault_on_uaccess(regs, info))
758 goto step;
759
760 perf_bp_event(wp, regs);
761
762 /*
763 * Defer stepping to the overflow handler if one is installed.
764 * Otherwise, insert a temporary mismatch breakpoint so that
765 * we can single-step over the watchpoint trigger.
766 */
767 if (!is_default_overflow_handler(wp))
768 goto unlock;
769
770step:
771 enable_single_step(wp, instruction_pointer(regs));
772unlock:
773 rcu_read_unlock();
774 }
775}
776
777static void watchpoint_single_step_handler(unsigned long pc)
778{
779 int i;
780 struct perf_event *wp, **slots;
781 struct arch_hw_breakpoint *info;
782
783 slots = this_cpu_ptr(wp_on_reg);
784
785 for (i = 0; i < core_num_wrps; ++i) {
786 rcu_read_lock();
787
788 wp = slots[i];
789
790 if (wp == NULL)
791 goto unlock;
792
793 info = counter_arch_bp(wp);
794 if (!info->step_ctrl.enabled)
795 goto unlock;
796
797 /*
798 * Restore the original watchpoint if we've completed the
799 * single-step.
800 */
801 if (info->trigger != pc)
802 disable_single_step(wp);
803
804unlock:
805 rcu_read_unlock();
806 }
807}
808
809static void breakpoint_handler(unsigned long unknown, struct pt_regs *regs)
810{
811 int i;
812 u32 ctrl_reg, val, addr;
813 struct perf_event *bp, **slots;
814 struct arch_hw_breakpoint *info;
815 struct arch_hw_breakpoint_ctrl ctrl;
816
817 slots = this_cpu_ptr(bp_on_reg);
818
819 /* The exception entry code places the amended lr in the PC. */
820 addr = regs->ARM_pc;
821
822 /* Check the currently installed breakpoints first. */
823 for (i = 0; i < core_num_brps; ++i) {
824 rcu_read_lock();
825
826 bp = slots[i];
827
828 if (bp == NULL)
829 goto unlock;
830
831 info = counter_arch_bp(bp);
832
833 /* Check if the breakpoint value matches. */
834 val = read_wb_reg(ARM_BASE_BVR + i);
835 if (val != (addr & ~0x3))
836 goto mismatch;
837
838 /* Possible match, check the byte address select to confirm. */
839 ctrl_reg = read_wb_reg(ARM_BASE_BCR + i);
840 decode_ctrl_reg(ctrl_reg, &ctrl);
841 if ((1 << (addr & 0x3)) & ctrl.len) {
842 info->trigger = addr;
843 pr_debug("breakpoint fired: address = 0x%x\n", addr);
844 perf_bp_event(bp, regs);
845 if (!bp->overflow_handler)
846 enable_single_step(bp, addr);
847 goto unlock;
848 }
849
850mismatch:
851 /* If we're stepping a breakpoint, it can now be restored. */
852 if (info->step_ctrl.enabled)
853 disable_single_step(bp);
854unlock:
855 rcu_read_unlock();
856 }
857
858 /* Handle any pending watchpoint single-step breakpoints. */
859 watchpoint_single_step_handler(addr);
860}
861
862/*
863 * Called from either the Data Abort Handler [watchpoint] or the
864 * Prefetch Abort Handler [breakpoint] with interrupts disabled.
865 */
866static int hw_breakpoint_pending(unsigned long addr, unsigned int fsr,
867 struct pt_regs *regs)
868{
869 int ret = 0;
870 u32 dscr;
871
872 preempt_disable();
873
874 if (interrupts_enabled(regs))
875 local_irq_enable();
876
877 /* We only handle watchpoints and hardware breakpoints. */
878 ARM_DBG_READ(c0, c1, 0, dscr);
879
880 /* Perform perf callbacks. */
881 switch (ARM_DSCR_MOE(dscr)) {
882 case ARM_ENTRY_BREAKPOINT:
883 breakpoint_handler(addr, regs);
884 break;
885 case ARM_ENTRY_ASYNC_WATCHPOINT:
886 WARN(1, "Asynchronous watchpoint exception taken. Debugging results may be unreliable\n");
887 fallthrough;
888 case ARM_ENTRY_SYNC_WATCHPOINT:
889 watchpoint_handler(addr, fsr, regs);
890 break;
891 default:
892 ret = 1; /* Unhandled fault. */
893 }
894
895 preempt_enable();
896
897 return ret;
898}
899
900/*
901 * One-time initialisation.
902 */
903static cpumask_t debug_err_mask;
904
905static int debug_reg_trap(struct pt_regs *regs, unsigned int instr)
906{
907 int cpu = smp_processor_id();
908
909 pr_warn("Debug register access (0x%x) caused undefined instruction on CPU %d\n",
910 instr, cpu);
911
912 /* Set the error flag for this CPU and skip the faulting instruction. */
913 cpumask_set_cpu(cpu, &debug_err_mask);
914 instruction_pointer(regs) += 4;
915 return 0;
916}
917
918static struct undef_hook debug_reg_hook = {
919 .instr_mask = 0x0fe80f10,
920 .instr_val = 0x0e000e10,
921 .fn = debug_reg_trap,
922};
923
924/* Does this core support OS Save and Restore? */
925static bool core_has_os_save_restore(void)
926{
927 u32 oslsr;
928
929 switch (get_debug_arch()) {
930 case ARM_DEBUG_ARCH_V7_1:
931 return true;
932 case ARM_DEBUG_ARCH_V7_ECP14:
933 ARM_DBG_READ(c1, c1, 4, oslsr);
934 if (oslsr & ARM_OSLSR_OSLM0)
935 return true;
936 fallthrough;
937 default:
938 return false;
939 }
940}
941
942static void reset_ctrl_regs(unsigned int cpu)
943{
944 int i, raw_num_brps, err = 0;
945 u32 val;
946
947 /*
948 * v7 debug contains save and restore registers so that debug state
949 * can be maintained across low-power modes without leaving the debug
950 * logic powered up. It is IMPLEMENTATION DEFINED whether we can access
951 * the debug registers out of reset, so we must unlock the OS Lock
952 * Access Register to avoid taking undefined instruction exceptions
953 * later on.
954 */
955 switch (debug_arch) {
956 case ARM_DEBUG_ARCH_V6:
957 case ARM_DEBUG_ARCH_V6_1:
958 /* ARMv6 cores clear the registers out of reset. */
959 goto out_mdbgen;
960 case ARM_DEBUG_ARCH_V7_ECP14:
961 /*
962 * Ensure sticky power-down is clear (i.e. debug logic is
963 * powered up).
964 */
965 ARM_DBG_READ(c1, c5, 4, val);
966 if ((val & 0x1) == 0)
967 err = -EPERM;
968
969 if (!has_ossr)
970 goto clear_vcr;
971 break;
972 case ARM_DEBUG_ARCH_V7_1:
973 /*
974 * Ensure the OS double lock is clear.
975 */
976 ARM_DBG_READ(c1, c3, 4, val);
977 if ((val & 0x1) == 1)
978 err = -EPERM;
979 break;
980 }
981
982 if (err) {
983 pr_warn_once("CPU %d debug is powered down!\n", cpu);
984 cpumask_or(&debug_err_mask, &debug_err_mask, cpumask_of(cpu));
985 return;
986 }
987
988 /*
989 * Unconditionally clear the OS lock by writing a value
990 * other than CS_LAR_KEY to the access register.
991 */
992 ARM_DBG_WRITE(c1, c0, 4, ~CORESIGHT_UNLOCK);
993 isb();
994
995 /*
996 * Clear any configured vector-catch events before
997 * enabling monitor mode.
998 */
999clear_vcr:
1000 ARM_DBG_WRITE(c0, c7, 0, 0);
1001 isb();
1002
1003 if (cpumask_intersects(&debug_err_mask, cpumask_of(cpu))) {
1004 pr_warn_once("CPU %d failed to disable vector catch\n", cpu);
1005 return;
1006 }
1007
1008 /*
1009 * The control/value register pairs are UNKNOWN out of reset so
1010 * clear them to avoid spurious debug events.
1011 */
1012 raw_num_brps = get_num_brp_resources();
1013 for (i = 0; i < raw_num_brps; ++i) {
1014 write_wb_reg(ARM_BASE_BCR + i, 0UL);
1015 write_wb_reg(ARM_BASE_BVR + i, 0UL);
1016 }
1017
1018 for (i = 0; i < core_num_wrps; ++i) {
1019 write_wb_reg(ARM_BASE_WCR + i, 0UL);
1020 write_wb_reg(ARM_BASE_WVR + i, 0UL);
1021 }
1022
1023 if (cpumask_intersects(&debug_err_mask, cpumask_of(cpu))) {
1024 pr_warn_once("CPU %d failed to clear debug register pairs\n", cpu);
1025 return;
1026 }
1027
1028 /*
1029 * Have a crack at enabling monitor mode. We don't actually need
1030 * it yet, but reporting an error early is useful if it fails.
1031 */
1032out_mdbgen:
1033 if (enable_monitor_mode())
1034 cpumask_or(&debug_err_mask, &debug_err_mask, cpumask_of(cpu));
1035}
1036
1037static int dbg_reset_online(unsigned int cpu)
1038{
1039 local_irq_disable();
1040 reset_ctrl_regs(cpu);
1041 local_irq_enable();
1042 return 0;
1043}
1044
1045#ifdef CONFIG_CPU_PM
1046static int dbg_cpu_pm_notify(struct notifier_block *self, unsigned long action,
1047 void *v)
1048{
1049 if (action == CPU_PM_EXIT)
1050 reset_ctrl_regs(smp_processor_id());
1051
1052 return NOTIFY_OK;
1053}
1054
1055static struct notifier_block dbg_cpu_pm_nb = {
1056 .notifier_call = dbg_cpu_pm_notify,
1057};
1058
1059static void __init pm_init(void)
1060{
1061 cpu_pm_register_notifier(&dbg_cpu_pm_nb);
1062}
1063#else
1064static inline void pm_init(void)
1065{
1066}
1067#endif
1068
1069static int __init arch_hw_breakpoint_init(void)
1070{
1071 int ret;
1072
1073 debug_arch = get_debug_arch();
1074
1075 if (!debug_arch_supported()) {
1076 pr_info("debug architecture 0x%x unsupported.\n", debug_arch);
1077 return 0;
1078 }
1079
1080 /*
1081 * Scorpion CPUs (at least those in APQ8060) seem to set DBGPRSR.SPD
1082 * whenever a WFI is issued, even if the core is not powered down, in
1083 * violation of the architecture. When DBGPRSR.SPD is set, accesses to
1084 * breakpoint and watchpoint registers are treated as undefined, so
1085 * this results in boot time and runtime failures when these are
1086 * accessed and we unexpectedly take a trap.
1087 *
1088 * It's not clear if/how this can be worked around, so we blacklist
1089 * Scorpion CPUs to avoid these issues.
1090 */
1091 if (read_cpuid_part() == ARM_CPU_PART_SCORPION) {
1092 pr_info("Scorpion CPU detected. Hardware breakpoints and watchpoints disabled\n");
1093 return 0;
1094 }
1095
1096 has_ossr = core_has_os_save_restore();
1097
1098 /* Determine how many BRPs/WRPs are available. */
1099 core_num_brps = get_num_brps();
1100 core_num_wrps = get_num_wrps();
1101
1102 /*
1103 * We need to tread carefully here because DBGSWENABLE may be
1104 * driven low on this core and there isn't an architected way to
1105 * determine that.
1106 */
1107 cpus_read_lock();
1108 register_undef_hook(&debug_reg_hook);
1109
1110 /*
1111 * Register CPU notifier which resets the breakpoint resources. We
1112 * assume that a halting debugger will leave the world in a nice state
1113 * for us.
1114 */
1115 ret = cpuhp_setup_state_cpuslocked(CPUHP_AP_ONLINE_DYN,
1116 "arm/hw_breakpoint:online",
1117 dbg_reset_online, NULL);
1118 unregister_undef_hook(&debug_reg_hook);
1119 if (WARN_ON(ret < 0) || !cpumask_empty(&debug_err_mask)) {
1120 core_num_brps = 0;
1121 core_num_wrps = 0;
1122 if (ret > 0)
1123 cpuhp_remove_state_nocalls_cpuslocked(ret);
1124 cpus_read_unlock();
1125 return 0;
1126 }
1127
1128 pr_info("found %d " "%s" "breakpoint and %d watchpoint registers.\n",
1129 core_num_brps, core_has_mismatch_brps() ? "(+1 reserved) " :
1130 "", core_num_wrps);
1131
1132 /* Work out the maximum supported watchpoint length. */
1133 max_watchpoint_len = get_max_wp_len();
1134 pr_info("maximum watchpoint size is %u bytes.\n",
1135 max_watchpoint_len);
1136
1137 /* Register debug fault handler. */
1138 hook_fault_code(FAULT_CODE_DEBUG, hw_breakpoint_pending, SIGTRAP,
1139 TRAP_HWBKPT, "watchpoint debug exception");
1140 hook_ifault_code(FAULT_CODE_DEBUG, hw_breakpoint_pending, SIGTRAP,
1141 TRAP_HWBKPT, "breakpoint debug exception");
1142 cpus_read_unlock();
1143
1144 /* Register PM notifiers. */
1145 pm_init();
1146 return 0;
1147}
1148arch_initcall(arch_hw_breakpoint_init);
1149
1150void hw_breakpoint_pmu_read(struct perf_event *bp)
1151{
1152}
1153
1154/*
1155 * Dummy function to register with die_notifier.
1156 */
1157int hw_breakpoint_exceptions_notify(struct notifier_block *unused,
1158 unsigned long val, void *data)
1159{
1160 return NOTIFY_DONE;
1161}
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 version 2 as
4 * published by the Free Software Foundation.
5 *
6 * This program is distributed in the hope that it will be useful,
7 * but WITHOUT ANY WARRANTY; without even the implied warranty of
8 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
9 * GNU General Public License for more details.
10 *
11 * You should have received a copy of the GNU General Public License
12 * along with this program; if not, write to the Free Software
13 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
14 *
15 * Copyright (C) 2009, 2010 ARM Limited
16 *
17 * Author: Will Deacon <will.deacon@arm.com>
18 */
19
20/*
21 * HW_breakpoint: a unified kernel/user-space hardware breakpoint facility,
22 * using the CPU's debug registers.
23 */
24#define pr_fmt(fmt) "hw-breakpoint: " fmt
25
26#include <linux/errno.h>
27#include <linux/hardirq.h>
28#include <linux/perf_event.h>
29#include <linux/hw_breakpoint.h>
30#include <linux/smp.h>
31#include <linux/cpu_pm.h>
32#include <linux/coresight.h>
33
34#include <asm/cacheflush.h>
35#include <asm/cputype.h>
36#include <asm/current.h>
37#include <asm/hw_breakpoint.h>
38#include <asm/traps.h>
39
40/* Breakpoint currently in use for each BRP. */
41static DEFINE_PER_CPU(struct perf_event *, bp_on_reg[ARM_MAX_BRP]);
42
43/* Watchpoint currently in use for each WRP. */
44static DEFINE_PER_CPU(struct perf_event *, wp_on_reg[ARM_MAX_WRP]);
45
46/* Number of BRP/WRP registers on this CPU. */
47static int core_num_brps __ro_after_init;
48static int core_num_wrps __ro_after_init;
49
50/* Debug architecture version. */
51static u8 debug_arch __ro_after_init;
52
53/* Does debug architecture support OS Save and Restore? */
54static bool has_ossr __ro_after_init;
55
56/* Maximum supported watchpoint length. */
57static u8 max_watchpoint_len __ro_after_init;
58
59#define READ_WB_REG_CASE(OP2, M, VAL) \
60 case ((OP2 << 4) + M): \
61 ARM_DBG_READ(c0, c ## M, OP2, VAL); \
62 break
63
64#define WRITE_WB_REG_CASE(OP2, M, VAL) \
65 case ((OP2 << 4) + M): \
66 ARM_DBG_WRITE(c0, c ## M, OP2, VAL); \
67 break
68
69#define GEN_READ_WB_REG_CASES(OP2, VAL) \
70 READ_WB_REG_CASE(OP2, 0, VAL); \
71 READ_WB_REG_CASE(OP2, 1, VAL); \
72 READ_WB_REG_CASE(OP2, 2, VAL); \
73 READ_WB_REG_CASE(OP2, 3, VAL); \
74 READ_WB_REG_CASE(OP2, 4, VAL); \
75 READ_WB_REG_CASE(OP2, 5, VAL); \
76 READ_WB_REG_CASE(OP2, 6, VAL); \
77 READ_WB_REG_CASE(OP2, 7, VAL); \
78 READ_WB_REG_CASE(OP2, 8, VAL); \
79 READ_WB_REG_CASE(OP2, 9, VAL); \
80 READ_WB_REG_CASE(OP2, 10, VAL); \
81 READ_WB_REG_CASE(OP2, 11, VAL); \
82 READ_WB_REG_CASE(OP2, 12, VAL); \
83 READ_WB_REG_CASE(OP2, 13, VAL); \
84 READ_WB_REG_CASE(OP2, 14, VAL); \
85 READ_WB_REG_CASE(OP2, 15, VAL)
86
87#define GEN_WRITE_WB_REG_CASES(OP2, VAL) \
88 WRITE_WB_REG_CASE(OP2, 0, VAL); \
89 WRITE_WB_REG_CASE(OP2, 1, VAL); \
90 WRITE_WB_REG_CASE(OP2, 2, VAL); \
91 WRITE_WB_REG_CASE(OP2, 3, VAL); \
92 WRITE_WB_REG_CASE(OP2, 4, VAL); \
93 WRITE_WB_REG_CASE(OP2, 5, VAL); \
94 WRITE_WB_REG_CASE(OP2, 6, VAL); \
95 WRITE_WB_REG_CASE(OP2, 7, VAL); \
96 WRITE_WB_REG_CASE(OP2, 8, VAL); \
97 WRITE_WB_REG_CASE(OP2, 9, VAL); \
98 WRITE_WB_REG_CASE(OP2, 10, VAL); \
99 WRITE_WB_REG_CASE(OP2, 11, VAL); \
100 WRITE_WB_REG_CASE(OP2, 12, VAL); \
101 WRITE_WB_REG_CASE(OP2, 13, VAL); \
102 WRITE_WB_REG_CASE(OP2, 14, VAL); \
103 WRITE_WB_REG_CASE(OP2, 15, VAL)
104
105static u32 read_wb_reg(int n)
106{
107 u32 val = 0;
108
109 switch (n) {
110 GEN_READ_WB_REG_CASES(ARM_OP2_BVR, val);
111 GEN_READ_WB_REG_CASES(ARM_OP2_BCR, val);
112 GEN_READ_WB_REG_CASES(ARM_OP2_WVR, val);
113 GEN_READ_WB_REG_CASES(ARM_OP2_WCR, val);
114 default:
115 pr_warn("attempt to read from unknown breakpoint register %d\n",
116 n);
117 }
118
119 return val;
120}
121
122static void write_wb_reg(int n, u32 val)
123{
124 switch (n) {
125 GEN_WRITE_WB_REG_CASES(ARM_OP2_BVR, val);
126 GEN_WRITE_WB_REG_CASES(ARM_OP2_BCR, val);
127 GEN_WRITE_WB_REG_CASES(ARM_OP2_WVR, val);
128 GEN_WRITE_WB_REG_CASES(ARM_OP2_WCR, val);
129 default:
130 pr_warn("attempt to write to unknown breakpoint register %d\n",
131 n);
132 }
133 isb();
134}
135
136/* Determine debug architecture. */
137static u8 get_debug_arch(void)
138{
139 u32 didr;
140
141 /* Do we implement the extended CPUID interface? */
142 if (((read_cpuid_id() >> 16) & 0xf) != 0xf) {
143 pr_warn_once("CPUID feature registers not supported. "
144 "Assuming v6 debug is present.\n");
145 return ARM_DEBUG_ARCH_V6;
146 }
147
148 ARM_DBG_READ(c0, c0, 0, didr);
149 return (didr >> 16) & 0xf;
150}
151
152u8 arch_get_debug_arch(void)
153{
154 return debug_arch;
155}
156
157static int debug_arch_supported(void)
158{
159 u8 arch = get_debug_arch();
160
161 /* We don't support the memory-mapped interface. */
162 return (arch >= ARM_DEBUG_ARCH_V6 && arch <= ARM_DEBUG_ARCH_V7_ECP14) ||
163 arch >= ARM_DEBUG_ARCH_V7_1;
164}
165
166/* Can we determine the watchpoint access type from the fsr? */
167static int debug_exception_updates_fsr(void)
168{
169 return get_debug_arch() >= ARM_DEBUG_ARCH_V8;
170}
171
172/* Determine number of WRP registers available. */
173static int get_num_wrp_resources(void)
174{
175 u32 didr;
176 ARM_DBG_READ(c0, c0, 0, didr);
177 return ((didr >> 28) & 0xf) + 1;
178}
179
180/* Determine number of BRP registers available. */
181static int get_num_brp_resources(void)
182{
183 u32 didr;
184 ARM_DBG_READ(c0, c0, 0, didr);
185 return ((didr >> 24) & 0xf) + 1;
186}
187
188/* Does this core support mismatch breakpoints? */
189static int core_has_mismatch_brps(void)
190{
191 return (get_debug_arch() >= ARM_DEBUG_ARCH_V7_ECP14 &&
192 get_num_brp_resources() > 1);
193}
194
195/* Determine number of usable WRPs available. */
196static int get_num_wrps(void)
197{
198 /*
199 * On debug architectures prior to 7.1, when a watchpoint fires, the
200 * only way to work out which watchpoint it was is by disassembling
201 * the faulting instruction and working out the address of the memory
202 * access.
203 *
204 * Furthermore, we can only do this if the watchpoint was precise
205 * since imprecise watchpoints prevent us from calculating register
206 * based addresses.
207 *
208 * Providing we have more than 1 breakpoint register, we only report
209 * a single watchpoint register for the time being. This way, we always
210 * know which watchpoint fired. In the future we can either add a
211 * disassembler and address generation emulator, or we can insert a
212 * check to see if the DFAR is set on watchpoint exception entry
213 * [the ARM ARM states that the DFAR is UNKNOWN, but experience shows
214 * that it is set on some implementations].
215 */
216 if (get_debug_arch() < ARM_DEBUG_ARCH_V7_1)
217 return 1;
218
219 return get_num_wrp_resources();
220}
221
222/* Determine number of usable BRPs available. */
223static int get_num_brps(void)
224{
225 int brps = get_num_brp_resources();
226 return core_has_mismatch_brps() ? brps - 1 : brps;
227}
228
229/*
230 * In order to access the breakpoint/watchpoint control registers,
231 * we must be running in debug monitor mode. Unfortunately, we can
232 * be put into halting debug mode at any time by an external debugger
233 * but there is nothing we can do to prevent that.
234 */
235static int monitor_mode_enabled(void)
236{
237 u32 dscr;
238 ARM_DBG_READ(c0, c1, 0, dscr);
239 return !!(dscr & ARM_DSCR_MDBGEN);
240}
241
242static int enable_monitor_mode(void)
243{
244 u32 dscr;
245 ARM_DBG_READ(c0, c1, 0, dscr);
246
247 /* If monitor mode is already enabled, just return. */
248 if (dscr & ARM_DSCR_MDBGEN)
249 goto out;
250
251 /* Write to the corresponding DSCR. */
252 switch (get_debug_arch()) {
253 case ARM_DEBUG_ARCH_V6:
254 case ARM_DEBUG_ARCH_V6_1:
255 ARM_DBG_WRITE(c0, c1, 0, (dscr | ARM_DSCR_MDBGEN));
256 break;
257 case ARM_DEBUG_ARCH_V7_ECP14:
258 case ARM_DEBUG_ARCH_V7_1:
259 case ARM_DEBUG_ARCH_V8:
260 ARM_DBG_WRITE(c0, c2, 2, (dscr | ARM_DSCR_MDBGEN));
261 isb();
262 break;
263 default:
264 return -ENODEV;
265 }
266
267 /* Check that the write made it through. */
268 ARM_DBG_READ(c0, c1, 0, dscr);
269 if (!(dscr & ARM_DSCR_MDBGEN)) {
270 pr_warn_once("Failed to enable monitor mode on CPU %d.\n",
271 smp_processor_id());
272 return -EPERM;
273 }
274
275out:
276 return 0;
277}
278
279int hw_breakpoint_slots(int type)
280{
281 if (!debug_arch_supported())
282 return 0;
283
284 /*
285 * We can be called early, so don't rely on
286 * our static variables being initialised.
287 */
288 switch (type) {
289 case TYPE_INST:
290 return get_num_brps();
291 case TYPE_DATA:
292 return get_num_wrps();
293 default:
294 pr_warn("unknown slot type: %d\n", type);
295 return 0;
296 }
297}
298
299/*
300 * Check if 8-bit byte-address select is available.
301 * This clobbers WRP 0.
302 */
303static u8 get_max_wp_len(void)
304{
305 u32 ctrl_reg;
306 struct arch_hw_breakpoint_ctrl ctrl;
307 u8 size = 4;
308
309 if (debug_arch < ARM_DEBUG_ARCH_V7_ECP14)
310 goto out;
311
312 memset(&ctrl, 0, sizeof(ctrl));
313 ctrl.len = ARM_BREAKPOINT_LEN_8;
314 ctrl_reg = encode_ctrl_reg(ctrl);
315
316 write_wb_reg(ARM_BASE_WVR, 0);
317 write_wb_reg(ARM_BASE_WCR, ctrl_reg);
318 if ((read_wb_reg(ARM_BASE_WCR) & ctrl_reg) == ctrl_reg)
319 size = 8;
320
321out:
322 return size;
323}
324
325u8 arch_get_max_wp_len(void)
326{
327 return max_watchpoint_len;
328}
329
330/*
331 * Install a perf counter breakpoint.
332 */
333int arch_install_hw_breakpoint(struct perf_event *bp)
334{
335 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
336 struct perf_event **slot, **slots;
337 int i, max_slots, ctrl_base, val_base;
338 u32 addr, ctrl;
339
340 addr = info->address;
341 ctrl = encode_ctrl_reg(info->ctrl) | 0x1;
342
343 if (info->ctrl.type == ARM_BREAKPOINT_EXECUTE) {
344 /* Breakpoint */
345 ctrl_base = ARM_BASE_BCR;
346 val_base = ARM_BASE_BVR;
347 slots = this_cpu_ptr(bp_on_reg);
348 max_slots = core_num_brps;
349 } else {
350 /* Watchpoint */
351 ctrl_base = ARM_BASE_WCR;
352 val_base = ARM_BASE_WVR;
353 slots = this_cpu_ptr(wp_on_reg);
354 max_slots = core_num_wrps;
355 }
356
357 for (i = 0; i < max_slots; ++i) {
358 slot = &slots[i];
359
360 if (!*slot) {
361 *slot = bp;
362 break;
363 }
364 }
365
366 if (i == max_slots) {
367 pr_warn("Can't find any breakpoint slot\n");
368 return -EBUSY;
369 }
370
371 /* Override the breakpoint data with the step data. */
372 if (info->step_ctrl.enabled) {
373 addr = info->trigger & ~0x3;
374 ctrl = encode_ctrl_reg(info->step_ctrl);
375 if (info->ctrl.type != ARM_BREAKPOINT_EXECUTE) {
376 i = 0;
377 ctrl_base = ARM_BASE_BCR + core_num_brps;
378 val_base = ARM_BASE_BVR + core_num_brps;
379 }
380 }
381
382 /* Setup the address register. */
383 write_wb_reg(val_base + i, addr);
384
385 /* Setup the control register. */
386 write_wb_reg(ctrl_base + i, ctrl);
387 return 0;
388}
389
390void arch_uninstall_hw_breakpoint(struct perf_event *bp)
391{
392 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
393 struct perf_event **slot, **slots;
394 int i, max_slots, base;
395
396 if (info->ctrl.type == ARM_BREAKPOINT_EXECUTE) {
397 /* Breakpoint */
398 base = ARM_BASE_BCR;
399 slots = this_cpu_ptr(bp_on_reg);
400 max_slots = core_num_brps;
401 } else {
402 /* Watchpoint */
403 base = ARM_BASE_WCR;
404 slots = this_cpu_ptr(wp_on_reg);
405 max_slots = core_num_wrps;
406 }
407
408 /* Remove the breakpoint. */
409 for (i = 0; i < max_slots; ++i) {
410 slot = &slots[i];
411
412 if (*slot == bp) {
413 *slot = NULL;
414 break;
415 }
416 }
417
418 if (i == max_slots) {
419 pr_warn("Can't find any breakpoint slot\n");
420 return;
421 }
422
423 /* Ensure that we disable the mismatch breakpoint. */
424 if (info->ctrl.type != ARM_BREAKPOINT_EXECUTE &&
425 info->step_ctrl.enabled) {
426 i = 0;
427 base = ARM_BASE_BCR + core_num_brps;
428 }
429
430 /* Reset the control register. */
431 write_wb_reg(base + i, 0);
432}
433
434static int get_hbp_len(u8 hbp_len)
435{
436 unsigned int len_in_bytes = 0;
437
438 switch (hbp_len) {
439 case ARM_BREAKPOINT_LEN_1:
440 len_in_bytes = 1;
441 break;
442 case ARM_BREAKPOINT_LEN_2:
443 len_in_bytes = 2;
444 break;
445 case ARM_BREAKPOINT_LEN_4:
446 len_in_bytes = 4;
447 break;
448 case ARM_BREAKPOINT_LEN_8:
449 len_in_bytes = 8;
450 break;
451 }
452
453 return len_in_bytes;
454}
455
456/*
457 * Check whether bp virtual address is in kernel space.
458 */
459int arch_check_bp_in_kernelspace(struct perf_event *bp)
460{
461 unsigned int len;
462 unsigned long va;
463 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
464
465 va = info->address;
466 len = get_hbp_len(info->ctrl.len);
467
468 return (va >= TASK_SIZE) && ((va + len - 1) >= TASK_SIZE);
469}
470
471/*
472 * Extract generic type and length encodings from an arch_hw_breakpoint_ctrl.
473 * Hopefully this will disappear when ptrace can bypass the conversion
474 * to generic breakpoint descriptions.
475 */
476int arch_bp_generic_fields(struct arch_hw_breakpoint_ctrl ctrl,
477 int *gen_len, int *gen_type)
478{
479 /* Type */
480 switch (ctrl.type) {
481 case ARM_BREAKPOINT_EXECUTE:
482 *gen_type = HW_BREAKPOINT_X;
483 break;
484 case ARM_BREAKPOINT_LOAD:
485 *gen_type = HW_BREAKPOINT_R;
486 break;
487 case ARM_BREAKPOINT_STORE:
488 *gen_type = HW_BREAKPOINT_W;
489 break;
490 case ARM_BREAKPOINT_LOAD | ARM_BREAKPOINT_STORE:
491 *gen_type = HW_BREAKPOINT_RW;
492 break;
493 default:
494 return -EINVAL;
495 }
496
497 /* Len */
498 switch (ctrl.len) {
499 case ARM_BREAKPOINT_LEN_1:
500 *gen_len = HW_BREAKPOINT_LEN_1;
501 break;
502 case ARM_BREAKPOINT_LEN_2:
503 *gen_len = HW_BREAKPOINT_LEN_2;
504 break;
505 case ARM_BREAKPOINT_LEN_4:
506 *gen_len = HW_BREAKPOINT_LEN_4;
507 break;
508 case ARM_BREAKPOINT_LEN_8:
509 *gen_len = HW_BREAKPOINT_LEN_8;
510 break;
511 default:
512 return -EINVAL;
513 }
514
515 return 0;
516}
517
518/*
519 * Construct an arch_hw_breakpoint from a perf_event.
520 */
521static int arch_build_bp_info(struct perf_event *bp)
522{
523 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
524
525 /* Type */
526 switch (bp->attr.bp_type) {
527 case HW_BREAKPOINT_X:
528 info->ctrl.type = ARM_BREAKPOINT_EXECUTE;
529 break;
530 case HW_BREAKPOINT_R:
531 info->ctrl.type = ARM_BREAKPOINT_LOAD;
532 break;
533 case HW_BREAKPOINT_W:
534 info->ctrl.type = ARM_BREAKPOINT_STORE;
535 break;
536 case HW_BREAKPOINT_RW:
537 info->ctrl.type = ARM_BREAKPOINT_LOAD | ARM_BREAKPOINT_STORE;
538 break;
539 default:
540 return -EINVAL;
541 }
542
543 /* Len */
544 switch (bp->attr.bp_len) {
545 case HW_BREAKPOINT_LEN_1:
546 info->ctrl.len = ARM_BREAKPOINT_LEN_1;
547 break;
548 case HW_BREAKPOINT_LEN_2:
549 info->ctrl.len = ARM_BREAKPOINT_LEN_2;
550 break;
551 case HW_BREAKPOINT_LEN_4:
552 info->ctrl.len = ARM_BREAKPOINT_LEN_4;
553 break;
554 case HW_BREAKPOINT_LEN_8:
555 info->ctrl.len = ARM_BREAKPOINT_LEN_8;
556 if ((info->ctrl.type != ARM_BREAKPOINT_EXECUTE)
557 && max_watchpoint_len >= 8)
558 break;
559 default:
560 return -EINVAL;
561 }
562
563 /*
564 * Breakpoints must be of length 2 (thumb) or 4 (ARM) bytes.
565 * Watchpoints can be of length 1, 2, 4 or 8 bytes if supported
566 * by the hardware and must be aligned to the appropriate number of
567 * bytes.
568 */
569 if (info->ctrl.type == ARM_BREAKPOINT_EXECUTE &&
570 info->ctrl.len != ARM_BREAKPOINT_LEN_2 &&
571 info->ctrl.len != ARM_BREAKPOINT_LEN_4)
572 return -EINVAL;
573
574 /* Address */
575 info->address = bp->attr.bp_addr;
576
577 /* Privilege */
578 info->ctrl.privilege = ARM_BREAKPOINT_USER;
579 if (arch_check_bp_in_kernelspace(bp))
580 info->ctrl.privilege |= ARM_BREAKPOINT_PRIV;
581
582 /* Enabled? */
583 info->ctrl.enabled = !bp->attr.disabled;
584
585 /* Mismatch */
586 info->ctrl.mismatch = 0;
587
588 return 0;
589}
590
591/*
592 * Validate the arch-specific HW Breakpoint register settings.
593 */
594int arch_validate_hwbkpt_settings(struct perf_event *bp)
595{
596 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
597 int ret = 0;
598 u32 offset, alignment_mask = 0x3;
599
600 /* Ensure that we are in monitor debug mode. */
601 if (!monitor_mode_enabled())
602 return -ENODEV;
603
604 /* Build the arch_hw_breakpoint. */
605 ret = arch_build_bp_info(bp);
606 if (ret)
607 goto out;
608
609 /* Check address alignment. */
610 if (info->ctrl.len == ARM_BREAKPOINT_LEN_8)
611 alignment_mask = 0x7;
612 offset = info->address & alignment_mask;
613 switch (offset) {
614 case 0:
615 /* Aligned */
616 break;
617 case 1:
618 case 2:
619 /* Allow halfword watchpoints and breakpoints. */
620 if (info->ctrl.len == ARM_BREAKPOINT_LEN_2)
621 break;
622 case 3:
623 /* Allow single byte watchpoint. */
624 if (info->ctrl.len == ARM_BREAKPOINT_LEN_1)
625 break;
626 default:
627 ret = -EINVAL;
628 goto out;
629 }
630
631 info->address &= ~alignment_mask;
632 info->ctrl.len <<= offset;
633
634 if (is_default_overflow_handler(bp)) {
635 /*
636 * Mismatch breakpoints are required for single-stepping
637 * breakpoints.
638 */
639 if (!core_has_mismatch_brps())
640 return -EINVAL;
641
642 /* We don't allow mismatch breakpoints in kernel space. */
643 if (arch_check_bp_in_kernelspace(bp))
644 return -EPERM;
645
646 /*
647 * Per-cpu breakpoints are not supported by our stepping
648 * mechanism.
649 */
650 if (!bp->hw.target)
651 return -EINVAL;
652
653 /*
654 * We only support specific access types if the fsr
655 * reports them.
656 */
657 if (!debug_exception_updates_fsr() &&
658 (info->ctrl.type == ARM_BREAKPOINT_LOAD ||
659 info->ctrl.type == ARM_BREAKPOINT_STORE))
660 return -EINVAL;
661 }
662
663out:
664 return ret;
665}
666
667/*
668 * Enable/disable single-stepping over the breakpoint bp at address addr.
669 */
670static void enable_single_step(struct perf_event *bp, u32 addr)
671{
672 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
673
674 arch_uninstall_hw_breakpoint(bp);
675 info->step_ctrl.mismatch = 1;
676 info->step_ctrl.len = ARM_BREAKPOINT_LEN_4;
677 info->step_ctrl.type = ARM_BREAKPOINT_EXECUTE;
678 info->step_ctrl.privilege = info->ctrl.privilege;
679 info->step_ctrl.enabled = 1;
680 info->trigger = addr;
681 arch_install_hw_breakpoint(bp);
682}
683
684static void disable_single_step(struct perf_event *bp)
685{
686 arch_uninstall_hw_breakpoint(bp);
687 counter_arch_bp(bp)->step_ctrl.enabled = 0;
688 arch_install_hw_breakpoint(bp);
689}
690
691static void watchpoint_handler(unsigned long addr, unsigned int fsr,
692 struct pt_regs *regs)
693{
694 int i, access;
695 u32 val, ctrl_reg, alignment_mask;
696 struct perf_event *wp, **slots;
697 struct arch_hw_breakpoint *info;
698 struct arch_hw_breakpoint_ctrl ctrl;
699
700 slots = this_cpu_ptr(wp_on_reg);
701
702 for (i = 0; i < core_num_wrps; ++i) {
703 rcu_read_lock();
704
705 wp = slots[i];
706
707 if (wp == NULL)
708 goto unlock;
709
710 info = counter_arch_bp(wp);
711 /*
712 * The DFAR is an unknown value on debug architectures prior
713 * to 7.1. Since we only allow a single watchpoint on these
714 * older CPUs, we can set the trigger to the lowest possible
715 * faulting address.
716 */
717 if (debug_arch < ARM_DEBUG_ARCH_V7_1) {
718 BUG_ON(i > 0);
719 info->trigger = wp->attr.bp_addr;
720 } else {
721 if (info->ctrl.len == ARM_BREAKPOINT_LEN_8)
722 alignment_mask = 0x7;
723 else
724 alignment_mask = 0x3;
725
726 /* Check if the watchpoint value matches. */
727 val = read_wb_reg(ARM_BASE_WVR + i);
728 if (val != (addr & ~alignment_mask))
729 goto unlock;
730
731 /* Possible match, check the byte address select. */
732 ctrl_reg = read_wb_reg(ARM_BASE_WCR + i);
733 decode_ctrl_reg(ctrl_reg, &ctrl);
734 if (!((1 << (addr & alignment_mask)) & ctrl.len))
735 goto unlock;
736
737 /* Check that the access type matches. */
738 if (debug_exception_updates_fsr()) {
739 access = (fsr & ARM_FSR_ACCESS_MASK) ?
740 HW_BREAKPOINT_W : HW_BREAKPOINT_R;
741 if (!(access & hw_breakpoint_type(wp)))
742 goto unlock;
743 }
744
745 /* We have a winner. */
746 info->trigger = addr;
747 }
748
749 pr_debug("watchpoint fired: address = 0x%x\n", info->trigger);
750 perf_bp_event(wp, regs);
751
752 /*
753 * If no overflow handler is present, insert a temporary
754 * mismatch breakpoint so we can single-step over the
755 * watchpoint trigger.
756 */
757 if (is_default_overflow_handler(wp))
758 enable_single_step(wp, instruction_pointer(regs));
759
760unlock:
761 rcu_read_unlock();
762 }
763}
764
765static void watchpoint_single_step_handler(unsigned long pc)
766{
767 int i;
768 struct perf_event *wp, **slots;
769 struct arch_hw_breakpoint *info;
770
771 slots = this_cpu_ptr(wp_on_reg);
772
773 for (i = 0; i < core_num_wrps; ++i) {
774 rcu_read_lock();
775
776 wp = slots[i];
777
778 if (wp == NULL)
779 goto unlock;
780
781 info = counter_arch_bp(wp);
782 if (!info->step_ctrl.enabled)
783 goto unlock;
784
785 /*
786 * Restore the original watchpoint if we've completed the
787 * single-step.
788 */
789 if (info->trigger != pc)
790 disable_single_step(wp);
791
792unlock:
793 rcu_read_unlock();
794 }
795}
796
797static void breakpoint_handler(unsigned long unknown, struct pt_regs *regs)
798{
799 int i;
800 u32 ctrl_reg, val, addr;
801 struct perf_event *bp, **slots;
802 struct arch_hw_breakpoint *info;
803 struct arch_hw_breakpoint_ctrl ctrl;
804
805 slots = this_cpu_ptr(bp_on_reg);
806
807 /* The exception entry code places the amended lr in the PC. */
808 addr = regs->ARM_pc;
809
810 /* Check the currently installed breakpoints first. */
811 for (i = 0; i < core_num_brps; ++i) {
812 rcu_read_lock();
813
814 bp = slots[i];
815
816 if (bp == NULL)
817 goto unlock;
818
819 info = counter_arch_bp(bp);
820
821 /* Check if the breakpoint value matches. */
822 val = read_wb_reg(ARM_BASE_BVR + i);
823 if (val != (addr & ~0x3))
824 goto mismatch;
825
826 /* Possible match, check the byte address select to confirm. */
827 ctrl_reg = read_wb_reg(ARM_BASE_BCR + i);
828 decode_ctrl_reg(ctrl_reg, &ctrl);
829 if ((1 << (addr & 0x3)) & ctrl.len) {
830 info->trigger = addr;
831 pr_debug("breakpoint fired: address = 0x%x\n", addr);
832 perf_bp_event(bp, regs);
833 if (!bp->overflow_handler)
834 enable_single_step(bp, addr);
835 goto unlock;
836 }
837
838mismatch:
839 /* If we're stepping a breakpoint, it can now be restored. */
840 if (info->step_ctrl.enabled)
841 disable_single_step(bp);
842unlock:
843 rcu_read_unlock();
844 }
845
846 /* Handle any pending watchpoint single-step breakpoints. */
847 watchpoint_single_step_handler(addr);
848}
849
850/*
851 * Called from either the Data Abort Handler [watchpoint] or the
852 * Prefetch Abort Handler [breakpoint] with interrupts disabled.
853 */
854static int hw_breakpoint_pending(unsigned long addr, unsigned int fsr,
855 struct pt_regs *regs)
856{
857 int ret = 0;
858 u32 dscr;
859
860 preempt_disable();
861
862 if (interrupts_enabled(regs))
863 local_irq_enable();
864
865 /* We only handle watchpoints and hardware breakpoints. */
866 ARM_DBG_READ(c0, c1, 0, dscr);
867
868 /* Perform perf callbacks. */
869 switch (ARM_DSCR_MOE(dscr)) {
870 case ARM_ENTRY_BREAKPOINT:
871 breakpoint_handler(addr, regs);
872 break;
873 case ARM_ENTRY_ASYNC_WATCHPOINT:
874 WARN(1, "Asynchronous watchpoint exception taken. Debugging results may be unreliable\n");
875 case ARM_ENTRY_SYNC_WATCHPOINT:
876 watchpoint_handler(addr, fsr, regs);
877 break;
878 default:
879 ret = 1; /* Unhandled fault. */
880 }
881
882 preempt_enable();
883
884 return ret;
885}
886
887/*
888 * One-time initialisation.
889 */
890static cpumask_t debug_err_mask;
891
892static int debug_reg_trap(struct pt_regs *regs, unsigned int instr)
893{
894 int cpu = smp_processor_id();
895
896 pr_warn("Debug register access (0x%x) caused undefined instruction on CPU %d\n",
897 instr, cpu);
898
899 /* Set the error flag for this CPU and skip the faulting instruction. */
900 cpumask_set_cpu(cpu, &debug_err_mask);
901 instruction_pointer(regs) += 4;
902 return 0;
903}
904
905static struct undef_hook debug_reg_hook = {
906 .instr_mask = 0x0fe80f10,
907 .instr_val = 0x0e000e10,
908 .fn = debug_reg_trap,
909};
910
911/* Does this core support OS Save and Restore? */
912static bool core_has_os_save_restore(void)
913{
914 u32 oslsr;
915
916 switch (get_debug_arch()) {
917 case ARM_DEBUG_ARCH_V7_1:
918 return true;
919 case ARM_DEBUG_ARCH_V7_ECP14:
920 ARM_DBG_READ(c1, c1, 4, oslsr);
921 if (oslsr & ARM_OSLSR_OSLM0)
922 return true;
923 default:
924 return false;
925 }
926}
927
928static void reset_ctrl_regs(unsigned int cpu)
929{
930 int i, raw_num_brps, err = 0;
931 u32 val;
932
933 /*
934 * v7 debug contains save and restore registers so that debug state
935 * can be maintained across low-power modes without leaving the debug
936 * logic powered up. It is IMPLEMENTATION DEFINED whether we can access
937 * the debug registers out of reset, so we must unlock the OS Lock
938 * Access Register to avoid taking undefined instruction exceptions
939 * later on.
940 */
941 switch (debug_arch) {
942 case ARM_DEBUG_ARCH_V6:
943 case ARM_DEBUG_ARCH_V6_1:
944 /* ARMv6 cores clear the registers out of reset. */
945 goto out_mdbgen;
946 case ARM_DEBUG_ARCH_V7_ECP14:
947 /*
948 * Ensure sticky power-down is clear (i.e. debug logic is
949 * powered up).
950 */
951 ARM_DBG_READ(c1, c5, 4, val);
952 if ((val & 0x1) == 0)
953 err = -EPERM;
954
955 if (!has_ossr)
956 goto clear_vcr;
957 break;
958 case ARM_DEBUG_ARCH_V7_1:
959 /*
960 * Ensure the OS double lock is clear.
961 */
962 ARM_DBG_READ(c1, c3, 4, val);
963 if ((val & 0x1) == 1)
964 err = -EPERM;
965 break;
966 }
967
968 if (err) {
969 pr_warn_once("CPU %d debug is powered down!\n", cpu);
970 cpumask_or(&debug_err_mask, &debug_err_mask, cpumask_of(cpu));
971 return;
972 }
973
974 /*
975 * Unconditionally clear the OS lock by writing a value
976 * other than CS_LAR_KEY to the access register.
977 */
978 ARM_DBG_WRITE(c1, c0, 4, ~CORESIGHT_UNLOCK);
979 isb();
980
981 /*
982 * Clear any configured vector-catch events before
983 * enabling monitor mode.
984 */
985clear_vcr:
986 ARM_DBG_WRITE(c0, c7, 0, 0);
987 isb();
988
989 if (cpumask_intersects(&debug_err_mask, cpumask_of(cpu))) {
990 pr_warn_once("CPU %d failed to disable vector catch\n", cpu);
991 return;
992 }
993
994 /*
995 * The control/value register pairs are UNKNOWN out of reset so
996 * clear them to avoid spurious debug events.
997 */
998 raw_num_brps = get_num_brp_resources();
999 for (i = 0; i < raw_num_brps; ++i) {
1000 write_wb_reg(ARM_BASE_BCR + i, 0UL);
1001 write_wb_reg(ARM_BASE_BVR + i, 0UL);
1002 }
1003
1004 for (i = 0; i < core_num_wrps; ++i) {
1005 write_wb_reg(ARM_BASE_WCR + i, 0UL);
1006 write_wb_reg(ARM_BASE_WVR + i, 0UL);
1007 }
1008
1009 if (cpumask_intersects(&debug_err_mask, cpumask_of(cpu))) {
1010 pr_warn_once("CPU %d failed to clear debug register pairs\n", cpu);
1011 return;
1012 }
1013
1014 /*
1015 * Have a crack at enabling monitor mode. We don't actually need
1016 * it yet, but reporting an error early is useful if it fails.
1017 */
1018out_mdbgen:
1019 if (enable_monitor_mode())
1020 cpumask_or(&debug_err_mask, &debug_err_mask, cpumask_of(cpu));
1021}
1022
1023static int dbg_reset_online(unsigned int cpu)
1024{
1025 local_irq_disable();
1026 reset_ctrl_regs(cpu);
1027 local_irq_enable();
1028 return 0;
1029}
1030
1031#ifdef CONFIG_CPU_PM
1032static int dbg_cpu_pm_notify(struct notifier_block *self, unsigned long action,
1033 void *v)
1034{
1035 if (action == CPU_PM_EXIT)
1036 reset_ctrl_regs(smp_processor_id());
1037
1038 return NOTIFY_OK;
1039}
1040
1041static struct notifier_block dbg_cpu_pm_nb = {
1042 .notifier_call = dbg_cpu_pm_notify,
1043};
1044
1045static void __init pm_init(void)
1046{
1047 cpu_pm_register_notifier(&dbg_cpu_pm_nb);
1048}
1049#else
1050static inline void pm_init(void)
1051{
1052}
1053#endif
1054
1055static int __init arch_hw_breakpoint_init(void)
1056{
1057 int ret;
1058
1059 debug_arch = get_debug_arch();
1060
1061 if (!debug_arch_supported()) {
1062 pr_info("debug architecture 0x%x unsupported.\n", debug_arch);
1063 return 0;
1064 }
1065
1066 /*
1067 * Scorpion CPUs (at least those in APQ8060) seem to set DBGPRSR.SPD
1068 * whenever a WFI is issued, even if the core is not powered down, in
1069 * violation of the architecture. When DBGPRSR.SPD is set, accesses to
1070 * breakpoint and watchpoint registers are treated as undefined, so
1071 * this results in boot time and runtime failures when these are
1072 * accessed and we unexpectedly take a trap.
1073 *
1074 * It's not clear if/how this can be worked around, so we blacklist
1075 * Scorpion CPUs to avoid these issues.
1076 */
1077 if (read_cpuid_part() == ARM_CPU_PART_SCORPION) {
1078 pr_info("Scorpion CPU detected. Hardware breakpoints and watchpoints disabled\n");
1079 return 0;
1080 }
1081
1082 has_ossr = core_has_os_save_restore();
1083
1084 /* Determine how many BRPs/WRPs are available. */
1085 core_num_brps = get_num_brps();
1086 core_num_wrps = get_num_wrps();
1087
1088 /*
1089 * We need to tread carefully here because DBGSWENABLE may be
1090 * driven low on this core and there isn't an architected way to
1091 * determine that.
1092 */
1093 cpus_read_lock();
1094 register_undef_hook(&debug_reg_hook);
1095
1096 /*
1097 * Register CPU notifier which resets the breakpoint resources. We
1098 * assume that a halting debugger will leave the world in a nice state
1099 * for us.
1100 */
1101 ret = cpuhp_setup_state_cpuslocked(CPUHP_AP_ONLINE_DYN,
1102 "arm/hw_breakpoint:online",
1103 dbg_reset_online, NULL);
1104 unregister_undef_hook(&debug_reg_hook);
1105 if (WARN_ON(ret < 0) || !cpumask_empty(&debug_err_mask)) {
1106 core_num_brps = 0;
1107 core_num_wrps = 0;
1108 if (ret > 0)
1109 cpuhp_remove_state_nocalls_cpuslocked(ret);
1110 cpus_read_unlock();
1111 return 0;
1112 }
1113
1114 pr_info("found %d " "%s" "breakpoint and %d watchpoint registers.\n",
1115 core_num_brps, core_has_mismatch_brps() ? "(+1 reserved) " :
1116 "", core_num_wrps);
1117
1118 /* Work out the maximum supported watchpoint length. */
1119 max_watchpoint_len = get_max_wp_len();
1120 pr_info("maximum watchpoint size is %u bytes.\n",
1121 max_watchpoint_len);
1122
1123 /* Register debug fault handler. */
1124 hook_fault_code(FAULT_CODE_DEBUG, hw_breakpoint_pending, SIGTRAP,
1125 TRAP_HWBKPT, "watchpoint debug exception");
1126 hook_ifault_code(FAULT_CODE_DEBUG, hw_breakpoint_pending, SIGTRAP,
1127 TRAP_HWBKPT, "breakpoint debug exception");
1128 cpus_read_unlock();
1129
1130 /* Register PM notifiers. */
1131 pm_init();
1132 return 0;
1133}
1134arch_initcall(arch_hw_breakpoint_init);
1135
1136void hw_breakpoint_pmu_read(struct perf_event *bp)
1137{
1138}
1139
1140/*
1141 * Dummy function to register with die_notifier.
1142 */
1143int hw_breakpoint_exceptions_notify(struct notifier_block *unused,
1144 unsigned long val, void *data)
1145{
1146 return NOTIFY_DONE;
1147}