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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/cfi.h>
21#include <linux/cpu_pm.h>
22#include <linux/coresight.h>
23
24#include <asm/cacheflush.h>
25#include <asm/cputype.h>
26#include <asm/current.h>
27#include <asm/hw_breakpoint.h>
28#include <asm/traps.h>
29
30/* Breakpoint currently in use for each BRP. */
31static DEFINE_PER_CPU(struct perf_event *, bp_on_reg[ARM_MAX_BRP]);
32
33/* Watchpoint currently in use for each WRP. */
34static DEFINE_PER_CPU(struct perf_event *, wp_on_reg[ARM_MAX_WRP]);
35
36/* Number of BRP/WRP registers on this CPU. */
37static int core_num_brps __ro_after_init;
38static int core_num_wrps __ro_after_init;
39
40/* Debug architecture version. */
41static u8 debug_arch __ro_after_init;
42
43/* Does debug architecture support OS Save and Restore? */
44static bool has_ossr __ro_after_init;
45
46/* Maximum supported watchpoint length. */
47static u8 max_watchpoint_len __ro_after_init;
48
49#define READ_WB_REG_CASE(OP2, M, VAL) \
50 case ((OP2 << 4) + M): \
51 ARM_DBG_READ(c0, c ## M, OP2, VAL); \
52 break
53
54#define WRITE_WB_REG_CASE(OP2, M, VAL) \
55 case ((OP2 << 4) + M): \
56 ARM_DBG_WRITE(c0, c ## M, OP2, VAL); \
57 break
58
59#define GEN_READ_WB_REG_CASES(OP2, VAL) \
60 READ_WB_REG_CASE(OP2, 0, VAL); \
61 READ_WB_REG_CASE(OP2, 1, VAL); \
62 READ_WB_REG_CASE(OP2, 2, VAL); \
63 READ_WB_REG_CASE(OP2, 3, VAL); \
64 READ_WB_REG_CASE(OP2, 4, VAL); \
65 READ_WB_REG_CASE(OP2, 5, VAL); \
66 READ_WB_REG_CASE(OP2, 6, VAL); \
67 READ_WB_REG_CASE(OP2, 7, VAL); \
68 READ_WB_REG_CASE(OP2, 8, VAL); \
69 READ_WB_REG_CASE(OP2, 9, VAL); \
70 READ_WB_REG_CASE(OP2, 10, VAL); \
71 READ_WB_REG_CASE(OP2, 11, VAL); \
72 READ_WB_REG_CASE(OP2, 12, VAL); \
73 READ_WB_REG_CASE(OP2, 13, VAL); \
74 READ_WB_REG_CASE(OP2, 14, VAL); \
75 READ_WB_REG_CASE(OP2, 15, VAL)
76
77#define GEN_WRITE_WB_REG_CASES(OP2, VAL) \
78 WRITE_WB_REG_CASE(OP2, 0, VAL); \
79 WRITE_WB_REG_CASE(OP2, 1, VAL); \
80 WRITE_WB_REG_CASE(OP2, 2, VAL); \
81 WRITE_WB_REG_CASE(OP2, 3, VAL); \
82 WRITE_WB_REG_CASE(OP2, 4, VAL); \
83 WRITE_WB_REG_CASE(OP2, 5, VAL); \
84 WRITE_WB_REG_CASE(OP2, 6, VAL); \
85 WRITE_WB_REG_CASE(OP2, 7, VAL); \
86 WRITE_WB_REG_CASE(OP2, 8, VAL); \
87 WRITE_WB_REG_CASE(OP2, 9, VAL); \
88 WRITE_WB_REG_CASE(OP2, 10, VAL); \
89 WRITE_WB_REG_CASE(OP2, 11, VAL); \
90 WRITE_WB_REG_CASE(OP2, 12, VAL); \
91 WRITE_WB_REG_CASE(OP2, 13, VAL); \
92 WRITE_WB_REG_CASE(OP2, 14, VAL); \
93 WRITE_WB_REG_CASE(OP2, 15, VAL)
94
95static u32 read_wb_reg(int n)
96{
97 u32 val = 0;
98
99 switch (n) {
100 GEN_READ_WB_REG_CASES(ARM_OP2_BVR, val);
101 GEN_READ_WB_REG_CASES(ARM_OP2_BCR, val);
102 GEN_READ_WB_REG_CASES(ARM_OP2_WVR, val);
103 GEN_READ_WB_REG_CASES(ARM_OP2_WCR, val);
104 default:
105 pr_warn("attempt to read from unknown breakpoint register %d\n",
106 n);
107 }
108
109 return val;
110}
111
112static void write_wb_reg(int n, u32 val)
113{
114 switch (n) {
115 GEN_WRITE_WB_REG_CASES(ARM_OP2_BVR, val);
116 GEN_WRITE_WB_REG_CASES(ARM_OP2_BCR, val);
117 GEN_WRITE_WB_REG_CASES(ARM_OP2_WVR, val);
118 GEN_WRITE_WB_REG_CASES(ARM_OP2_WCR, val);
119 default:
120 pr_warn("attempt to write to unknown breakpoint register %d\n",
121 n);
122 }
123 isb();
124}
125
126/* Determine debug architecture. */
127static u8 get_debug_arch(void)
128{
129 u32 didr;
130
131 /* Do we implement the extended CPUID interface? */
132 if (((read_cpuid_id() >> 16) & 0xf) != 0xf) {
133 pr_warn_once("CPUID feature registers not supported. "
134 "Assuming v6 debug is present.\n");
135 return ARM_DEBUG_ARCH_V6;
136 }
137
138 ARM_DBG_READ(c0, c0, 0, didr);
139 return (didr >> 16) & 0xf;
140}
141
142u8 arch_get_debug_arch(void)
143{
144 return debug_arch;
145}
146
147static int debug_arch_supported(void)
148{
149 u8 arch = get_debug_arch();
150
151 /* We don't support the memory-mapped interface. */
152 return (arch >= ARM_DEBUG_ARCH_V6 && arch <= ARM_DEBUG_ARCH_V7_ECP14) ||
153 arch >= ARM_DEBUG_ARCH_V7_1;
154}
155
156/* Can we determine the watchpoint access type from the fsr? */
157static int debug_exception_updates_fsr(void)
158{
159 return get_debug_arch() >= ARM_DEBUG_ARCH_V8;
160}
161
162/* Determine number of WRP registers available. */
163static int get_num_wrp_resources(void)
164{
165 u32 didr;
166 ARM_DBG_READ(c0, c0, 0, didr);
167 return ((didr >> 28) & 0xf) + 1;
168}
169
170/* Determine number of BRP registers available. */
171static int get_num_brp_resources(void)
172{
173 u32 didr;
174 ARM_DBG_READ(c0, c0, 0, didr);
175 return ((didr >> 24) & 0xf) + 1;
176}
177
178/* Does this core support mismatch breakpoints? */
179static int core_has_mismatch_brps(void)
180{
181 return (get_debug_arch() >= ARM_DEBUG_ARCH_V7_ECP14 &&
182 get_num_brp_resources() > 1);
183}
184
185/* Determine number of usable WRPs available. */
186static int get_num_wrps(void)
187{
188 /*
189 * On debug architectures prior to 7.1, when a watchpoint fires, the
190 * only way to work out which watchpoint it was is by disassembling
191 * the faulting instruction and working out the address of the memory
192 * access.
193 *
194 * Furthermore, we can only do this if the watchpoint was precise
195 * since imprecise watchpoints prevent us from calculating register
196 * based addresses.
197 *
198 * Providing we have more than 1 breakpoint register, we only report
199 * a single watchpoint register for the time being. This way, we always
200 * know which watchpoint fired. In the future we can either add a
201 * disassembler and address generation emulator, or we can insert a
202 * check to see if the DFAR is set on watchpoint exception entry
203 * [the ARM ARM states that the DFAR is UNKNOWN, but experience shows
204 * that it is set on some implementations].
205 */
206 if (get_debug_arch() < ARM_DEBUG_ARCH_V7_1)
207 return 1;
208
209 return get_num_wrp_resources();
210}
211
212/* Determine number of usable BRPs available. */
213static int get_num_brps(void)
214{
215 int brps = get_num_brp_resources();
216 return core_has_mismatch_brps() ? brps - 1 : brps;
217}
218
219/*
220 * In order to access the breakpoint/watchpoint control registers,
221 * we must be running in debug monitor mode. Unfortunately, we can
222 * be put into halting debug mode at any time by an external debugger
223 * but there is nothing we can do to prevent that.
224 */
225static int monitor_mode_enabled(void)
226{
227 u32 dscr;
228 ARM_DBG_READ(c0, c1, 0, dscr);
229 return !!(dscr & ARM_DSCR_MDBGEN);
230}
231
232static int enable_monitor_mode(void)
233{
234 u32 dscr;
235 ARM_DBG_READ(c0, c1, 0, dscr);
236
237 /* If monitor mode is already enabled, just return. */
238 if (dscr & ARM_DSCR_MDBGEN)
239 goto out;
240
241 /* Write to the corresponding DSCR. */
242 switch (get_debug_arch()) {
243 case ARM_DEBUG_ARCH_V6:
244 case ARM_DEBUG_ARCH_V6_1:
245 ARM_DBG_WRITE(c0, c1, 0, (dscr | ARM_DSCR_MDBGEN));
246 break;
247 case ARM_DEBUG_ARCH_V7_ECP14:
248 case ARM_DEBUG_ARCH_V7_1:
249 case ARM_DEBUG_ARCH_V8:
250 case ARM_DEBUG_ARCH_V8_1:
251 case ARM_DEBUG_ARCH_V8_2:
252 case ARM_DEBUG_ARCH_V8_4:
253 ARM_DBG_WRITE(c0, c2, 2, (dscr | ARM_DSCR_MDBGEN));
254 isb();
255 break;
256 default:
257 return -ENODEV;
258 }
259
260 /* Check that the write made it through. */
261 ARM_DBG_READ(c0, c1, 0, dscr);
262 if (!(dscr & ARM_DSCR_MDBGEN)) {
263 pr_warn_once("Failed to enable monitor mode on CPU %d.\n",
264 smp_processor_id());
265 return -EPERM;
266 }
267
268out:
269 return 0;
270}
271
272int hw_breakpoint_slots(int type)
273{
274 if (!debug_arch_supported())
275 return 0;
276
277 /*
278 * We can be called early, so don't rely on
279 * our static variables being initialised.
280 */
281 switch (type) {
282 case TYPE_INST:
283 return get_num_brps();
284 case TYPE_DATA:
285 return get_num_wrps();
286 default:
287 pr_warn("unknown slot type: %d\n", type);
288 return 0;
289 }
290}
291
292/*
293 * Check if 8-bit byte-address select is available.
294 * This clobbers WRP 0.
295 */
296static u8 get_max_wp_len(void)
297{
298 u32 ctrl_reg;
299 struct arch_hw_breakpoint_ctrl ctrl;
300 u8 size = 4;
301
302 if (debug_arch < ARM_DEBUG_ARCH_V7_ECP14)
303 goto out;
304
305 memset(&ctrl, 0, sizeof(ctrl));
306 ctrl.len = ARM_BREAKPOINT_LEN_8;
307 ctrl_reg = encode_ctrl_reg(ctrl);
308
309 write_wb_reg(ARM_BASE_WVR, 0);
310 write_wb_reg(ARM_BASE_WCR, ctrl_reg);
311 if ((read_wb_reg(ARM_BASE_WCR) & ctrl_reg) == ctrl_reg)
312 size = 8;
313
314out:
315 return size;
316}
317
318u8 arch_get_max_wp_len(void)
319{
320 return max_watchpoint_len;
321}
322
323/*
324 * Install a perf counter breakpoint.
325 */
326int arch_install_hw_breakpoint(struct perf_event *bp)
327{
328 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
329 struct perf_event **slot, **slots;
330 int i, max_slots, ctrl_base, val_base;
331 u32 addr, ctrl;
332
333 addr = info->address;
334 ctrl = encode_ctrl_reg(info->ctrl) | 0x1;
335
336 if (info->ctrl.type == ARM_BREAKPOINT_EXECUTE) {
337 /* Breakpoint */
338 ctrl_base = ARM_BASE_BCR;
339 val_base = ARM_BASE_BVR;
340 slots = this_cpu_ptr(bp_on_reg);
341 max_slots = core_num_brps;
342 } else {
343 /* Watchpoint */
344 ctrl_base = ARM_BASE_WCR;
345 val_base = ARM_BASE_WVR;
346 slots = this_cpu_ptr(wp_on_reg);
347 max_slots = core_num_wrps;
348 }
349
350 for (i = 0; i < max_slots; ++i) {
351 slot = &slots[i];
352
353 if (!*slot) {
354 *slot = bp;
355 break;
356 }
357 }
358
359 if (i == max_slots) {
360 pr_warn("Can't find any breakpoint slot\n");
361 return -EBUSY;
362 }
363
364 /* Override the breakpoint data with the step data. */
365 if (info->step_ctrl.enabled) {
366 addr = info->trigger & ~0x3;
367 ctrl = encode_ctrl_reg(info->step_ctrl);
368 if (info->ctrl.type != ARM_BREAKPOINT_EXECUTE) {
369 i = 0;
370 ctrl_base = ARM_BASE_BCR + core_num_brps;
371 val_base = ARM_BASE_BVR + core_num_brps;
372 }
373 }
374
375 /* Setup the address register. */
376 write_wb_reg(val_base + i, addr);
377
378 /* Setup the control register. */
379 write_wb_reg(ctrl_base + i, ctrl);
380 return 0;
381}
382
383void arch_uninstall_hw_breakpoint(struct perf_event *bp)
384{
385 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
386 struct perf_event **slot, **slots;
387 int i, max_slots, base;
388
389 if (info->ctrl.type == ARM_BREAKPOINT_EXECUTE) {
390 /* Breakpoint */
391 base = ARM_BASE_BCR;
392 slots = this_cpu_ptr(bp_on_reg);
393 max_slots = core_num_brps;
394 } else {
395 /* Watchpoint */
396 base = ARM_BASE_WCR;
397 slots = this_cpu_ptr(wp_on_reg);
398 max_slots = core_num_wrps;
399 }
400
401 /* Remove the breakpoint. */
402 for (i = 0; i < max_slots; ++i) {
403 slot = &slots[i];
404
405 if (*slot == bp) {
406 *slot = NULL;
407 break;
408 }
409 }
410
411 if (i == max_slots) {
412 pr_warn("Can't find any breakpoint slot\n");
413 return;
414 }
415
416 /* Ensure that we disable the mismatch breakpoint. */
417 if (info->ctrl.type != ARM_BREAKPOINT_EXECUTE &&
418 info->step_ctrl.enabled) {
419 i = 0;
420 base = ARM_BASE_BCR + core_num_brps;
421 }
422
423 /* Reset the control register. */
424 write_wb_reg(base + i, 0);
425}
426
427static int get_hbp_len(u8 hbp_len)
428{
429 unsigned int len_in_bytes = 0;
430
431 switch (hbp_len) {
432 case ARM_BREAKPOINT_LEN_1:
433 len_in_bytes = 1;
434 break;
435 case ARM_BREAKPOINT_LEN_2:
436 len_in_bytes = 2;
437 break;
438 case ARM_BREAKPOINT_LEN_4:
439 len_in_bytes = 4;
440 break;
441 case ARM_BREAKPOINT_LEN_8:
442 len_in_bytes = 8;
443 break;
444 }
445
446 return len_in_bytes;
447}
448
449/*
450 * Check whether bp virtual address is in kernel space.
451 */
452int arch_check_bp_in_kernelspace(struct arch_hw_breakpoint *hw)
453{
454 unsigned int len;
455 unsigned long va;
456
457 va = hw->address;
458 len = get_hbp_len(hw->ctrl.len);
459
460 return (va >= TASK_SIZE) && ((va + len - 1) >= TASK_SIZE);
461}
462
463/*
464 * Extract generic type and length encodings from an arch_hw_breakpoint_ctrl.
465 * Hopefully this will disappear when ptrace can bypass the conversion
466 * to generic breakpoint descriptions.
467 */
468int arch_bp_generic_fields(struct arch_hw_breakpoint_ctrl ctrl,
469 int *gen_len, int *gen_type)
470{
471 /* Type */
472 switch (ctrl.type) {
473 case ARM_BREAKPOINT_EXECUTE:
474 *gen_type = HW_BREAKPOINT_X;
475 break;
476 case ARM_BREAKPOINT_LOAD:
477 *gen_type = HW_BREAKPOINT_R;
478 break;
479 case ARM_BREAKPOINT_STORE:
480 *gen_type = HW_BREAKPOINT_W;
481 break;
482 case ARM_BREAKPOINT_LOAD | ARM_BREAKPOINT_STORE:
483 *gen_type = HW_BREAKPOINT_RW;
484 break;
485 default:
486 return -EINVAL;
487 }
488
489 /* Len */
490 switch (ctrl.len) {
491 case ARM_BREAKPOINT_LEN_1:
492 *gen_len = HW_BREAKPOINT_LEN_1;
493 break;
494 case ARM_BREAKPOINT_LEN_2:
495 *gen_len = HW_BREAKPOINT_LEN_2;
496 break;
497 case ARM_BREAKPOINT_LEN_4:
498 *gen_len = HW_BREAKPOINT_LEN_4;
499 break;
500 case ARM_BREAKPOINT_LEN_8:
501 *gen_len = HW_BREAKPOINT_LEN_8;
502 break;
503 default:
504 return -EINVAL;
505 }
506
507 return 0;
508}
509
510/*
511 * Construct an arch_hw_breakpoint from a perf_event.
512 */
513static int arch_build_bp_info(struct perf_event *bp,
514 const struct perf_event_attr *attr,
515 struct arch_hw_breakpoint *hw)
516{
517 /* Type */
518 switch (attr->bp_type) {
519 case HW_BREAKPOINT_X:
520 hw->ctrl.type = ARM_BREAKPOINT_EXECUTE;
521 break;
522 case HW_BREAKPOINT_R:
523 hw->ctrl.type = ARM_BREAKPOINT_LOAD;
524 break;
525 case HW_BREAKPOINT_W:
526 hw->ctrl.type = ARM_BREAKPOINT_STORE;
527 break;
528 case HW_BREAKPOINT_RW:
529 hw->ctrl.type = ARM_BREAKPOINT_LOAD | ARM_BREAKPOINT_STORE;
530 break;
531 default:
532 return -EINVAL;
533 }
534
535 /* Len */
536 switch (attr->bp_len) {
537 case HW_BREAKPOINT_LEN_1:
538 hw->ctrl.len = ARM_BREAKPOINT_LEN_1;
539 break;
540 case HW_BREAKPOINT_LEN_2:
541 hw->ctrl.len = ARM_BREAKPOINT_LEN_2;
542 break;
543 case HW_BREAKPOINT_LEN_4:
544 hw->ctrl.len = ARM_BREAKPOINT_LEN_4;
545 break;
546 case HW_BREAKPOINT_LEN_8:
547 hw->ctrl.len = ARM_BREAKPOINT_LEN_8;
548 if ((hw->ctrl.type != ARM_BREAKPOINT_EXECUTE)
549 && max_watchpoint_len >= 8)
550 break;
551 fallthrough;
552 default:
553 return -EINVAL;
554 }
555
556 /*
557 * Breakpoints must be of length 2 (thumb) or 4 (ARM) bytes.
558 * Watchpoints can be of length 1, 2, 4 or 8 bytes if supported
559 * by the hardware and must be aligned to the appropriate number of
560 * bytes.
561 */
562 if (hw->ctrl.type == ARM_BREAKPOINT_EXECUTE &&
563 hw->ctrl.len != ARM_BREAKPOINT_LEN_2 &&
564 hw->ctrl.len != ARM_BREAKPOINT_LEN_4)
565 return -EINVAL;
566
567 /* Address */
568 hw->address = attr->bp_addr;
569
570 /* Privilege */
571 hw->ctrl.privilege = ARM_BREAKPOINT_USER;
572 if (arch_check_bp_in_kernelspace(hw))
573 hw->ctrl.privilege |= ARM_BREAKPOINT_PRIV;
574
575 /* Enabled? */
576 hw->ctrl.enabled = !attr->disabled;
577
578 /* Mismatch */
579 hw->ctrl.mismatch = 0;
580
581 return 0;
582}
583
584/*
585 * Validate the arch-specific HW Breakpoint register settings.
586 */
587int hw_breakpoint_arch_parse(struct perf_event *bp,
588 const struct perf_event_attr *attr,
589 struct arch_hw_breakpoint *hw)
590{
591 int ret = 0;
592 u32 offset, alignment_mask = 0x3;
593
594 /* Ensure that we are in monitor debug mode. */
595 if (!monitor_mode_enabled())
596 return -ENODEV;
597
598 /* Build the arch_hw_breakpoint. */
599 ret = arch_build_bp_info(bp, attr, hw);
600 if (ret)
601 goto out;
602
603 /* Check address alignment. */
604 if (hw->ctrl.len == ARM_BREAKPOINT_LEN_8)
605 alignment_mask = 0x7;
606 offset = hw->address & alignment_mask;
607 switch (offset) {
608 case 0:
609 /* Aligned */
610 break;
611 case 1:
612 case 2:
613 /* Allow halfword watchpoints and breakpoints. */
614 if (hw->ctrl.len == ARM_BREAKPOINT_LEN_2)
615 break;
616 fallthrough;
617 case 3:
618 /* Allow single byte watchpoint. */
619 if (hw->ctrl.len == ARM_BREAKPOINT_LEN_1)
620 break;
621 fallthrough;
622 default:
623 ret = -EINVAL;
624 goto out;
625 }
626
627 hw->address &= ~alignment_mask;
628 hw->ctrl.len <<= offset;
629
630 if (is_default_overflow_handler(bp)) {
631 /*
632 * Mismatch breakpoints are required for single-stepping
633 * breakpoints.
634 */
635 if (!core_has_mismatch_brps())
636 return -EINVAL;
637
638 /* We don't allow mismatch breakpoints in kernel space. */
639 if (arch_check_bp_in_kernelspace(hw))
640 return -EPERM;
641
642 /*
643 * Per-cpu breakpoints are not supported by our stepping
644 * mechanism.
645 */
646 if (!bp->hw.target)
647 return -EINVAL;
648
649 /*
650 * We only support specific access types if the fsr
651 * reports them.
652 */
653 if (!debug_exception_updates_fsr() &&
654 (hw->ctrl.type == ARM_BREAKPOINT_LOAD ||
655 hw->ctrl.type == ARM_BREAKPOINT_STORE))
656 return -EINVAL;
657 }
658
659out:
660 return ret;
661}
662
663/*
664 * Enable/disable single-stepping over the breakpoint bp at address addr.
665 */
666static void enable_single_step(struct perf_event *bp, u32 addr)
667{
668 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
669
670 arch_uninstall_hw_breakpoint(bp);
671 info->step_ctrl.mismatch = 1;
672 info->step_ctrl.len = ARM_BREAKPOINT_LEN_4;
673 info->step_ctrl.type = ARM_BREAKPOINT_EXECUTE;
674 info->step_ctrl.privilege = info->ctrl.privilege;
675 info->step_ctrl.enabled = 1;
676 info->trigger = addr;
677 arch_install_hw_breakpoint(bp);
678}
679
680static void disable_single_step(struct perf_event *bp)
681{
682 arch_uninstall_hw_breakpoint(bp);
683 counter_arch_bp(bp)->step_ctrl.enabled = 0;
684 arch_install_hw_breakpoint(bp);
685}
686
687/*
688 * Arm32 hardware does not always report a watchpoint hit address that matches
689 * one of the watchpoints set. It can also report an address "near" the
690 * watchpoint if a single instruction access both watched and unwatched
691 * addresses. There is no straight-forward way, short of disassembling the
692 * offending instruction, to map that address back to the watchpoint. This
693 * function computes the distance of the memory access from the watchpoint as a
694 * heuristic for the likelyhood that a given access triggered the watchpoint.
695 *
696 * See this same function in the arm64 platform code, which has the same
697 * problem.
698 *
699 * The function returns the distance of the address from the bytes watched by
700 * the watchpoint. In case of an exact match, it returns 0.
701 */
702static u32 get_distance_from_watchpoint(unsigned long addr, u32 val,
703 struct arch_hw_breakpoint_ctrl *ctrl)
704{
705 u32 wp_low, wp_high;
706 u32 lens, lene;
707
708 lens = __ffs(ctrl->len);
709 lene = __fls(ctrl->len);
710
711 wp_low = val + lens;
712 wp_high = val + lene;
713 if (addr < wp_low)
714 return wp_low - addr;
715 else if (addr > wp_high)
716 return addr - wp_high;
717 else
718 return 0;
719}
720
721static int watchpoint_fault_on_uaccess(struct pt_regs *regs,
722 struct arch_hw_breakpoint *info)
723{
724 return !user_mode(regs) && info->ctrl.privilege == ARM_BREAKPOINT_USER;
725}
726
727static void watchpoint_handler(unsigned long addr, unsigned int fsr,
728 struct pt_regs *regs)
729{
730 int i, access, closest_match = 0;
731 u32 min_dist = -1, dist;
732 u32 val, ctrl_reg;
733 struct perf_event *wp, **slots;
734 struct arch_hw_breakpoint *info;
735 struct arch_hw_breakpoint_ctrl ctrl;
736
737 slots = this_cpu_ptr(wp_on_reg);
738
739 /*
740 * Find all watchpoints that match the reported address. If no exact
741 * match is found. Attribute the hit to the closest watchpoint.
742 */
743 rcu_read_lock();
744 for (i = 0; i < core_num_wrps; ++i) {
745 wp = slots[i];
746 if (wp == NULL)
747 continue;
748
749 /*
750 * The DFAR is an unknown value on debug architectures prior
751 * to 7.1. Since we only allow a single watchpoint on these
752 * older CPUs, we can set the trigger to the lowest possible
753 * faulting address.
754 */
755 if (debug_arch < ARM_DEBUG_ARCH_V7_1) {
756 BUG_ON(i > 0);
757 info = counter_arch_bp(wp);
758 info->trigger = wp->attr.bp_addr;
759 } else {
760 /* Check that the access type matches. */
761 if (debug_exception_updates_fsr()) {
762 access = (fsr & ARM_FSR_ACCESS_MASK) ?
763 HW_BREAKPOINT_W : HW_BREAKPOINT_R;
764 if (!(access & hw_breakpoint_type(wp)))
765 continue;
766 }
767
768 val = read_wb_reg(ARM_BASE_WVR + i);
769 ctrl_reg = read_wb_reg(ARM_BASE_WCR + i);
770 decode_ctrl_reg(ctrl_reg, &ctrl);
771 dist = get_distance_from_watchpoint(addr, val, &ctrl);
772 if (dist < min_dist) {
773 min_dist = dist;
774 closest_match = i;
775 }
776 /* Is this an exact match? */
777 if (dist != 0)
778 continue;
779
780 /* We have a winner. */
781 info = counter_arch_bp(wp);
782 info->trigger = addr;
783 }
784
785 pr_debug("watchpoint fired: address = 0x%x\n", info->trigger);
786
787 /*
788 * If we triggered a user watchpoint from a uaccess routine,
789 * then handle the stepping ourselves since userspace really
790 * can't help us with this.
791 */
792 if (watchpoint_fault_on_uaccess(regs, info))
793 goto step;
794
795 perf_bp_event(wp, regs);
796
797 /*
798 * Defer stepping to the overflow handler if one is installed.
799 * Otherwise, insert a temporary mismatch breakpoint so that
800 * we can single-step over the watchpoint trigger.
801 */
802 if (!is_default_overflow_handler(wp))
803 continue;
804step:
805 enable_single_step(wp, instruction_pointer(regs));
806 }
807
808 if (min_dist > 0 && min_dist != -1) {
809 /* No exact match found. */
810 wp = slots[closest_match];
811 info = counter_arch_bp(wp);
812 info->trigger = addr;
813 pr_debug("watchpoint fired: address = 0x%x\n", info->trigger);
814 perf_bp_event(wp, regs);
815 if (is_default_overflow_handler(wp))
816 enable_single_step(wp, instruction_pointer(regs));
817 }
818
819 rcu_read_unlock();
820}
821
822static void watchpoint_single_step_handler(unsigned long pc)
823{
824 int i;
825 struct perf_event *wp, **slots;
826 struct arch_hw_breakpoint *info;
827
828 slots = this_cpu_ptr(wp_on_reg);
829
830 for (i = 0; i < core_num_wrps; ++i) {
831 rcu_read_lock();
832
833 wp = slots[i];
834
835 if (wp == NULL)
836 goto unlock;
837
838 info = counter_arch_bp(wp);
839 if (!info->step_ctrl.enabled)
840 goto unlock;
841
842 /*
843 * Restore the original watchpoint if we've completed the
844 * single-step.
845 */
846 if (info->trigger != pc)
847 disable_single_step(wp);
848
849unlock:
850 rcu_read_unlock();
851 }
852}
853
854static void breakpoint_handler(unsigned long unknown, struct pt_regs *regs)
855{
856 int i;
857 u32 ctrl_reg, val, addr;
858 struct perf_event *bp, **slots;
859 struct arch_hw_breakpoint *info;
860 struct arch_hw_breakpoint_ctrl ctrl;
861
862 slots = this_cpu_ptr(bp_on_reg);
863
864 /* The exception entry code places the amended lr in the PC. */
865 addr = regs->ARM_pc;
866
867 /* Check the currently installed breakpoints first. */
868 for (i = 0; i < core_num_brps; ++i) {
869 rcu_read_lock();
870
871 bp = slots[i];
872
873 if (bp == NULL)
874 goto unlock;
875
876 info = counter_arch_bp(bp);
877
878 /* Check if the breakpoint value matches. */
879 val = read_wb_reg(ARM_BASE_BVR + i);
880 if (val != (addr & ~0x3))
881 goto mismatch;
882
883 /* Possible match, check the byte address select to confirm. */
884 ctrl_reg = read_wb_reg(ARM_BASE_BCR + i);
885 decode_ctrl_reg(ctrl_reg, &ctrl);
886 if ((1 << (addr & 0x3)) & ctrl.len) {
887 info->trigger = addr;
888 pr_debug("breakpoint fired: address = 0x%x\n", addr);
889 perf_bp_event(bp, regs);
890 if (is_default_overflow_handler(bp))
891 enable_single_step(bp, addr);
892 goto unlock;
893 }
894
895mismatch:
896 /* If we're stepping a breakpoint, it can now be restored. */
897 if (info->step_ctrl.enabled)
898 disable_single_step(bp);
899unlock:
900 rcu_read_unlock();
901 }
902
903 /* Handle any pending watchpoint single-step breakpoints. */
904 watchpoint_single_step_handler(addr);
905}
906
907#ifdef CONFIG_CFI_CLANG
908static void hw_breakpoint_cfi_handler(struct pt_regs *regs)
909{
910 /*
911 * TODO: implementing target and type to pass to CFI using the more
912 * elaborate report_cfi_failure() requires compiler work. To be able
913 * to properly extract target information the compiler needs to
914 * emit a stable instructions sequence for the CFI checks so we can
915 * decode the instructions preceding the trap and figure out which
916 * registers were used.
917 */
918
919 switch (report_cfi_failure_noaddr(regs, instruction_pointer(regs))) {
920 case BUG_TRAP_TYPE_BUG:
921 die("Oops - CFI", regs, 0);
922 break;
923 case BUG_TRAP_TYPE_WARN:
924 /* Skip the breaking instruction */
925 instruction_pointer(regs) += 4;
926 break;
927 default:
928 die("Unknown CFI error", regs, 0);
929 break;
930 }
931}
932#else
933static void hw_breakpoint_cfi_handler(struct pt_regs *regs)
934{
935}
936#endif
937
938/*
939 * Called from either the Data Abort Handler [watchpoint] or the
940 * Prefetch Abort Handler [breakpoint] with interrupts disabled.
941 */
942static int hw_breakpoint_pending(unsigned long addr, unsigned int fsr,
943 struct pt_regs *regs)
944{
945 int ret = 0;
946 u32 dscr;
947
948 preempt_disable();
949
950 if (interrupts_enabled(regs))
951 local_irq_enable();
952
953 /* We only handle watchpoints and hardware breakpoints. */
954 ARM_DBG_READ(c0, c1, 0, dscr);
955
956 /* Perform perf callbacks. */
957 switch (ARM_DSCR_MOE(dscr)) {
958 case ARM_ENTRY_BREAKPOINT:
959 breakpoint_handler(addr, regs);
960 break;
961 case ARM_ENTRY_ASYNC_WATCHPOINT:
962 WARN(1, "Asynchronous watchpoint exception taken. Debugging results may be unreliable\n");
963 fallthrough;
964 case ARM_ENTRY_SYNC_WATCHPOINT:
965 watchpoint_handler(addr, fsr, regs);
966 break;
967 case ARM_ENTRY_CFI_BREAKPOINT:
968 hw_breakpoint_cfi_handler(regs);
969 break;
970 default:
971 ret = 1; /* Unhandled fault. */
972 }
973
974 preempt_enable();
975
976 return ret;
977}
978
979#ifdef CONFIG_ARM_ERRATA_764319
980static int oslsr_fault;
981
982static int debug_oslsr_trap(struct pt_regs *regs, unsigned int instr)
983{
984 oslsr_fault = 1;
985 instruction_pointer(regs) += 4;
986 return 0;
987}
988
989static struct undef_hook debug_oslsr_hook = {
990 .instr_mask = 0xffffffff,
991 .instr_val = 0xee115e91,
992 .fn = debug_oslsr_trap,
993};
994#endif
995
996/*
997 * One-time initialisation.
998 */
999static cpumask_t debug_err_mask;
1000
1001static int debug_reg_trap(struct pt_regs *regs, unsigned int instr)
1002{
1003 int cpu = smp_processor_id();
1004
1005 pr_warn("Debug register access (0x%x) caused undefined instruction on CPU %d\n",
1006 instr, cpu);
1007
1008 /* Set the error flag for this CPU and skip the faulting instruction. */
1009 cpumask_set_cpu(cpu, &debug_err_mask);
1010 instruction_pointer(regs) += 4;
1011 return 0;
1012}
1013
1014static struct undef_hook debug_reg_hook = {
1015 .instr_mask = 0x0fe80f10,
1016 .instr_val = 0x0e000e10,
1017 .fn = debug_reg_trap,
1018};
1019
1020/* Does this core support OS Save and Restore? */
1021static bool core_has_os_save_restore(void)
1022{
1023 u32 oslsr;
1024
1025 switch (get_debug_arch()) {
1026 case ARM_DEBUG_ARCH_V7_1:
1027 return true;
1028 case ARM_DEBUG_ARCH_V7_ECP14:
1029#ifdef CONFIG_ARM_ERRATA_764319
1030 oslsr_fault = 0;
1031 register_undef_hook(&debug_oslsr_hook);
1032 ARM_DBG_READ(c1, c1, 4, oslsr);
1033 unregister_undef_hook(&debug_oslsr_hook);
1034 if (oslsr_fault)
1035 return false;
1036#else
1037 ARM_DBG_READ(c1, c1, 4, oslsr);
1038#endif
1039 if (oslsr & ARM_OSLSR_OSLM0)
1040 return true;
1041 fallthrough;
1042 default:
1043 return false;
1044 }
1045}
1046
1047static void reset_ctrl_regs(unsigned int cpu)
1048{
1049 int i, raw_num_brps, err = 0;
1050 u32 val;
1051
1052 /*
1053 * v7 debug contains save and restore registers so that debug state
1054 * can be maintained across low-power modes without leaving the debug
1055 * logic powered up. It is IMPLEMENTATION DEFINED whether we can access
1056 * the debug registers out of reset, so we must unlock the OS Lock
1057 * Access Register to avoid taking undefined instruction exceptions
1058 * later on.
1059 */
1060 switch (debug_arch) {
1061 case ARM_DEBUG_ARCH_V6:
1062 case ARM_DEBUG_ARCH_V6_1:
1063 /* ARMv6 cores clear the registers out of reset. */
1064 goto out_mdbgen;
1065 case ARM_DEBUG_ARCH_V7_ECP14:
1066 /*
1067 * Ensure sticky power-down is clear (i.e. debug logic is
1068 * powered up).
1069 */
1070 ARM_DBG_READ(c1, c5, 4, val);
1071 if ((val & 0x1) == 0)
1072 err = -EPERM;
1073
1074 if (!has_ossr)
1075 goto clear_vcr;
1076 break;
1077 case ARM_DEBUG_ARCH_V7_1:
1078 /*
1079 * Ensure the OS double lock is clear.
1080 */
1081 ARM_DBG_READ(c1, c3, 4, val);
1082 if ((val & 0x1) == 1)
1083 err = -EPERM;
1084 break;
1085 }
1086
1087 if (err) {
1088 pr_warn_once("CPU %d debug is powered down!\n", cpu);
1089 cpumask_or(&debug_err_mask, &debug_err_mask, cpumask_of(cpu));
1090 return;
1091 }
1092
1093 /*
1094 * Unconditionally clear the OS lock by writing a value
1095 * other than CS_LAR_KEY to the access register.
1096 */
1097 ARM_DBG_WRITE(c1, c0, 4, ~CORESIGHT_UNLOCK);
1098 isb();
1099
1100 /*
1101 * Clear any configured vector-catch events before
1102 * enabling monitor mode.
1103 */
1104clear_vcr:
1105 ARM_DBG_WRITE(c0, c7, 0, 0);
1106 isb();
1107
1108 if (cpumask_intersects(&debug_err_mask, cpumask_of(cpu))) {
1109 pr_warn_once("CPU %d failed to disable vector catch\n", cpu);
1110 return;
1111 }
1112
1113 /*
1114 * The control/value register pairs are UNKNOWN out of reset so
1115 * clear them to avoid spurious debug events.
1116 */
1117 raw_num_brps = get_num_brp_resources();
1118 for (i = 0; i < raw_num_brps; ++i) {
1119 write_wb_reg(ARM_BASE_BCR + i, 0UL);
1120 write_wb_reg(ARM_BASE_BVR + i, 0UL);
1121 }
1122
1123 for (i = 0; i < core_num_wrps; ++i) {
1124 write_wb_reg(ARM_BASE_WCR + i, 0UL);
1125 write_wb_reg(ARM_BASE_WVR + i, 0UL);
1126 }
1127
1128 if (cpumask_intersects(&debug_err_mask, cpumask_of(cpu))) {
1129 pr_warn_once("CPU %d failed to clear debug register pairs\n", cpu);
1130 return;
1131 }
1132
1133 /*
1134 * Have a crack at enabling monitor mode. We don't actually need
1135 * it yet, but reporting an error early is useful if it fails.
1136 */
1137out_mdbgen:
1138 if (enable_monitor_mode())
1139 cpumask_or(&debug_err_mask, &debug_err_mask, cpumask_of(cpu));
1140}
1141
1142static int dbg_reset_online(unsigned int cpu)
1143{
1144 local_irq_disable();
1145 reset_ctrl_regs(cpu);
1146 local_irq_enable();
1147 return 0;
1148}
1149
1150#ifdef CONFIG_CPU_PM
1151static int dbg_cpu_pm_notify(struct notifier_block *self, unsigned long action,
1152 void *v)
1153{
1154 if (action == CPU_PM_EXIT)
1155 reset_ctrl_regs(smp_processor_id());
1156
1157 return NOTIFY_OK;
1158}
1159
1160static struct notifier_block dbg_cpu_pm_nb = {
1161 .notifier_call = dbg_cpu_pm_notify,
1162};
1163
1164static void __init pm_init(void)
1165{
1166 cpu_pm_register_notifier(&dbg_cpu_pm_nb);
1167}
1168#else
1169static inline void pm_init(void)
1170{
1171}
1172#endif
1173
1174static int __init arch_hw_breakpoint_init(void)
1175{
1176 int ret;
1177
1178 debug_arch = get_debug_arch();
1179
1180 if (!debug_arch_supported()) {
1181 pr_info("debug architecture 0x%x unsupported.\n", debug_arch);
1182 return 0;
1183 }
1184
1185 /*
1186 * Scorpion CPUs (at least those in APQ8060) seem to set DBGPRSR.SPD
1187 * whenever a WFI is issued, even if the core is not powered down, in
1188 * violation of the architecture. When DBGPRSR.SPD is set, accesses to
1189 * breakpoint and watchpoint registers are treated as undefined, so
1190 * this results in boot time and runtime failures when these are
1191 * accessed and we unexpectedly take a trap.
1192 *
1193 * It's not clear if/how this can be worked around, so we blacklist
1194 * Scorpion CPUs to avoid these issues.
1195 */
1196 if (read_cpuid_part() == ARM_CPU_PART_SCORPION) {
1197 pr_info("Scorpion CPU detected. Hardware breakpoints and watchpoints disabled\n");
1198 return 0;
1199 }
1200
1201 has_ossr = core_has_os_save_restore();
1202
1203 /* Determine how many BRPs/WRPs are available. */
1204 core_num_brps = get_num_brps();
1205 core_num_wrps = get_num_wrps();
1206
1207 /*
1208 * We need to tread carefully here because DBGSWENABLE may be
1209 * driven low on this core and there isn't an architected way to
1210 * determine that.
1211 */
1212 cpus_read_lock();
1213 register_undef_hook(&debug_reg_hook);
1214
1215 /*
1216 * Register CPU notifier which resets the breakpoint resources. We
1217 * assume that a halting debugger will leave the world in a nice state
1218 * for us.
1219 */
1220 ret = cpuhp_setup_state_cpuslocked(CPUHP_AP_ONLINE_DYN,
1221 "arm/hw_breakpoint:online",
1222 dbg_reset_online, NULL);
1223 unregister_undef_hook(&debug_reg_hook);
1224 if (WARN_ON(ret < 0) || !cpumask_empty(&debug_err_mask)) {
1225 core_num_brps = 0;
1226 core_num_wrps = 0;
1227 if (ret > 0)
1228 cpuhp_remove_state_nocalls_cpuslocked(ret);
1229 cpus_read_unlock();
1230 return 0;
1231 }
1232
1233 pr_info("found %d " "%s" "breakpoint and %d watchpoint registers.\n",
1234 core_num_brps, core_has_mismatch_brps() ? "(+1 reserved) " :
1235 "", core_num_wrps);
1236
1237 /* Work out the maximum supported watchpoint length. */
1238 max_watchpoint_len = get_max_wp_len();
1239 pr_info("maximum watchpoint size is %u bytes.\n",
1240 max_watchpoint_len);
1241
1242 /* Register debug fault handler. */
1243 hook_fault_code(FAULT_CODE_DEBUG, hw_breakpoint_pending, SIGTRAP,
1244 TRAP_HWBKPT, "watchpoint debug exception");
1245 hook_ifault_code(FAULT_CODE_DEBUG, hw_breakpoint_pending, SIGTRAP,
1246 TRAP_HWBKPT, "breakpoint debug exception");
1247 cpus_read_unlock();
1248
1249 /* Register PM notifiers. */
1250 pm_init();
1251 return 0;
1252}
1253arch_initcall(arch_hw_breakpoint_init);
1254
1255void hw_breakpoint_pmu_read(struct perf_event *bp)
1256{
1257}
1258
1259/*
1260 * Dummy function to register with die_notifier.
1261 */
1262int hw_breakpoint_exceptions_notify(struct notifier_block *unused,
1263 unsigned long val, void *data)
1264{
1265 return NOTIFY_DONE;
1266}
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 (uses_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
686/*
687 * Arm32 hardware does not always report a watchpoint hit address that matches
688 * one of the watchpoints set. It can also report an address "near" the
689 * watchpoint if a single instruction access both watched and unwatched
690 * addresses. There is no straight-forward way, short of disassembling the
691 * offending instruction, to map that address back to the watchpoint. This
692 * function computes the distance of the memory access from the watchpoint as a
693 * heuristic for the likelyhood that a given access triggered the watchpoint.
694 *
695 * See this same function in the arm64 platform code, which has the same
696 * problem.
697 *
698 * The function returns the distance of the address from the bytes watched by
699 * the watchpoint. In case of an exact match, it returns 0.
700 */
701static u32 get_distance_from_watchpoint(unsigned long addr, u32 val,
702 struct arch_hw_breakpoint_ctrl *ctrl)
703{
704 u32 wp_low, wp_high;
705 u32 lens, lene;
706
707 lens = __ffs(ctrl->len);
708 lene = __fls(ctrl->len);
709
710 wp_low = val + lens;
711 wp_high = val + lene;
712 if (addr < wp_low)
713 return wp_low - addr;
714 else if (addr > wp_high)
715 return addr - wp_high;
716 else
717 return 0;
718}
719
720static int watchpoint_fault_on_uaccess(struct pt_regs *regs,
721 struct arch_hw_breakpoint *info)
722{
723 return !user_mode(regs) && info->ctrl.privilege == ARM_BREAKPOINT_USER;
724}
725
726static void watchpoint_handler(unsigned long addr, unsigned int fsr,
727 struct pt_regs *regs)
728{
729 int i, access, closest_match = 0;
730 u32 min_dist = -1, dist;
731 u32 val, ctrl_reg;
732 struct perf_event *wp, **slots;
733 struct arch_hw_breakpoint *info;
734 struct arch_hw_breakpoint_ctrl ctrl;
735
736 slots = this_cpu_ptr(wp_on_reg);
737
738 /*
739 * Find all watchpoints that match the reported address. If no exact
740 * match is found. Attribute the hit to the closest watchpoint.
741 */
742 rcu_read_lock();
743 for (i = 0; i < core_num_wrps; ++i) {
744 wp = slots[i];
745 if (wp == NULL)
746 continue;
747
748 /*
749 * The DFAR is an unknown value on debug architectures prior
750 * to 7.1. Since we only allow a single watchpoint on these
751 * older CPUs, we can set the trigger to the lowest possible
752 * faulting address.
753 */
754 if (debug_arch < ARM_DEBUG_ARCH_V7_1) {
755 BUG_ON(i > 0);
756 info = counter_arch_bp(wp);
757 info->trigger = wp->attr.bp_addr;
758 } else {
759 /* Check that the access type matches. */
760 if (debug_exception_updates_fsr()) {
761 access = (fsr & ARM_FSR_ACCESS_MASK) ?
762 HW_BREAKPOINT_W : HW_BREAKPOINT_R;
763 if (!(access & hw_breakpoint_type(wp)))
764 continue;
765 }
766
767 val = read_wb_reg(ARM_BASE_WVR + i);
768 ctrl_reg = read_wb_reg(ARM_BASE_WCR + i);
769 decode_ctrl_reg(ctrl_reg, &ctrl);
770 dist = get_distance_from_watchpoint(addr, val, &ctrl);
771 if (dist < min_dist) {
772 min_dist = dist;
773 closest_match = i;
774 }
775 /* Is this an exact match? */
776 if (dist != 0)
777 continue;
778
779 /* We have a winner. */
780 info = counter_arch_bp(wp);
781 info->trigger = addr;
782 }
783
784 pr_debug("watchpoint fired: address = 0x%x\n", info->trigger);
785
786 /*
787 * If we triggered a user watchpoint from a uaccess routine,
788 * then handle the stepping ourselves since userspace really
789 * can't help us with this.
790 */
791 if (watchpoint_fault_on_uaccess(regs, info))
792 goto step;
793
794 perf_bp_event(wp, regs);
795
796 /*
797 * Defer stepping to the overflow handler if one is installed.
798 * Otherwise, insert a temporary mismatch breakpoint so that
799 * we can single-step over the watchpoint trigger.
800 */
801 if (!uses_default_overflow_handler(wp))
802 continue;
803step:
804 enable_single_step(wp, instruction_pointer(regs));
805 }
806
807 if (min_dist > 0 && min_dist != -1) {
808 /* No exact match found. */
809 wp = slots[closest_match];
810 info = counter_arch_bp(wp);
811 info->trigger = addr;
812 pr_debug("watchpoint fired: address = 0x%x\n", info->trigger);
813 perf_bp_event(wp, regs);
814 if (uses_default_overflow_handler(wp))
815 enable_single_step(wp, instruction_pointer(regs));
816 }
817
818 rcu_read_unlock();
819}
820
821static void watchpoint_single_step_handler(unsigned long pc)
822{
823 int i;
824 struct perf_event *wp, **slots;
825 struct arch_hw_breakpoint *info;
826
827 slots = this_cpu_ptr(wp_on_reg);
828
829 for (i = 0; i < core_num_wrps; ++i) {
830 rcu_read_lock();
831
832 wp = slots[i];
833
834 if (wp == NULL)
835 goto unlock;
836
837 info = counter_arch_bp(wp);
838 if (!info->step_ctrl.enabled)
839 goto unlock;
840
841 /*
842 * Restore the original watchpoint if we've completed the
843 * single-step.
844 */
845 if (info->trigger != pc)
846 disable_single_step(wp);
847
848unlock:
849 rcu_read_unlock();
850 }
851}
852
853static void breakpoint_handler(unsigned long unknown, struct pt_regs *regs)
854{
855 int i;
856 u32 ctrl_reg, val, addr;
857 struct perf_event *bp, **slots;
858 struct arch_hw_breakpoint *info;
859 struct arch_hw_breakpoint_ctrl ctrl;
860
861 slots = this_cpu_ptr(bp_on_reg);
862
863 /* The exception entry code places the amended lr in the PC. */
864 addr = regs->ARM_pc;
865
866 /* Check the currently installed breakpoints first. */
867 for (i = 0; i < core_num_brps; ++i) {
868 rcu_read_lock();
869
870 bp = slots[i];
871
872 if (bp == NULL)
873 goto unlock;
874
875 info = counter_arch_bp(bp);
876
877 /* Check if the breakpoint value matches. */
878 val = read_wb_reg(ARM_BASE_BVR + i);
879 if (val != (addr & ~0x3))
880 goto mismatch;
881
882 /* Possible match, check the byte address select to confirm. */
883 ctrl_reg = read_wb_reg(ARM_BASE_BCR + i);
884 decode_ctrl_reg(ctrl_reg, &ctrl);
885 if ((1 << (addr & 0x3)) & ctrl.len) {
886 info->trigger = addr;
887 pr_debug("breakpoint fired: address = 0x%x\n", addr);
888 perf_bp_event(bp, regs);
889 if (uses_default_overflow_handler(bp))
890 enable_single_step(bp, addr);
891 goto unlock;
892 }
893
894mismatch:
895 /* If we're stepping a breakpoint, it can now be restored. */
896 if (info->step_ctrl.enabled)
897 disable_single_step(bp);
898unlock:
899 rcu_read_unlock();
900 }
901
902 /* Handle any pending watchpoint single-step breakpoints. */
903 watchpoint_single_step_handler(addr);
904}
905
906/*
907 * Called from either the Data Abort Handler [watchpoint] or the
908 * Prefetch Abort Handler [breakpoint] with interrupts disabled.
909 */
910static int hw_breakpoint_pending(unsigned long addr, unsigned int fsr,
911 struct pt_regs *regs)
912{
913 int ret = 0;
914 u32 dscr;
915
916 preempt_disable();
917
918 if (interrupts_enabled(regs))
919 local_irq_enable();
920
921 /* We only handle watchpoints and hardware breakpoints. */
922 ARM_DBG_READ(c0, c1, 0, dscr);
923
924 /* Perform perf callbacks. */
925 switch (ARM_DSCR_MOE(dscr)) {
926 case ARM_ENTRY_BREAKPOINT:
927 breakpoint_handler(addr, regs);
928 break;
929 case ARM_ENTRY_ASYNC_WATCHPOINT:
930 WARN(1, "Asynchronous watchpoint exception taken. Debugging results may be unreliable\n");
931 fallthrough;
932 case ARM_ENTRY_SYNC_WATCHPOINT:
933 watchpoint_handler(addr, fsr, regs);
934 break;
935 default:
936 ret = 1; /* Unhandled fault. */
937 }
938
939 preempt_enable();
940
941 return ret;
942}
943
944#ifdef CONFIG_ARM_ERRATA_764319
945static int oslsr_fault;
946
947static int debug_oslsr_trap(struct pt_regs *regs, unsigned int instr)
948{
949 oslsr_fault = 1;
950 instruction_pointer(regs) += 4;
951 return 0;
952}
953
954static struct undef_hook debug_oslsr_hook = {
955 .instr_mask = 0xffffffff,
956 .instr_val = 0xee115e91,
957 .fn = debug_oslsr_trap,
958};
959#endif
960
961/*
962 * One-time initialisation.
963 */
964static cpumask_t debug_err_mask;
965
966static int debug_reg_trap(struct pt_regs *regs, unsigned int instr)
967{
968 int cpu = smp_processor_id();
969
970 pr_warn("Debug register access (0x%x) caused undefined instruction on CPU %d\n",
971 instr, cpu);
972
973 /* Set the error flag for this CPU and skip the faulting instruction. */
974 cpumask_set_cpu(cpu, &debug_err_mask);
975 instruction_pointer(regs) += 4;
976 return 0;
977}
978
979static struct undef_hook debug_reg_hook = {
980 .instr_mask = 0x0fe80f10,
981 .instr_val = 0x0e000e10,
982 .fn = debug_reg_trap,
983};
984
985/* Does this core support OS Save and Restore? */
986static bool core_has_os_save_restore(void)
987{
988 u32 oslsr;
989
990 switch (get_debug_arch()) {
991 case ARM_DEBUG_ARCH_V7_1:
992 return true;
993 case ARM_DEBUG_ARCH_V7_ECP14:
994#ifdef CONFIG_ARM_ERRATA_764319
995 oslsr_fault = 0;
996 register_undef_hook(&debug_oslsr_hook);
997 ARM_DBG_READ(c1, c1, 4, oslsr);
998 unregister_undef_hook(&debug_oslsr_hook);
999 if (oslsr_fault)
1000 return false;
1001#else
1002 ARM_DBG_READ(c1, c1, 4, oslsr);
1003#endif
1004 if (oslsr & ARM_OSLSR_OSLM0)
1005 return true;
1006 fallthrough;
1007 default:
1008 return false;
1009 }
1010}
1011
1012static void reset_ctrl_regs(unsigned int cpu)
1013{
1014 int i, raw_num_brps, err = 0;
1015 u32 val;
1016
1017 /*
1018 * v7 debug contains save and restore registers so that debug state
1019 * can be maintained across low-power modes without leaving the debug
1020 * logic powered up. It is IMPLEMENTATION DEFINED whether we can access
1021 * the debug registers out of reset, so we must unlock the OS Lock
1022 * Access Register to avoid taking undefined instruction exceptions
1023 * later on.
1024 */
1025 switch (debug_arch) {
1026 case ARM_DEBUG_ARCH_V6:
1027 case ARM_DEBUG_ARCH_V6_1:
1028 /* ARMv6 cores clear the registers out of reset. */
1029 goto out_mdbgen;
1030 case ARM_DEBUG_ARCH_V7_ECP14:
1031 /*
1032 * Ensure sticky power-down is clear (i.e. debug logic is
1033 * powered up).
1034 */
1035 ARM_DBG_READ(c1, c5, 4, val);
1036 if ((val & 0x1) == 0)
1037 err = -EPERM;
1038
1039 if (!has_ossr)
1040 goto clear_vcr;
1041 break;
1042 case ARM_DEBUG_ARCH_V7_1:
1043 /*
1044 * Ensure the OS double lock is clear.
1045 */
1046 ARM_DBG_READ(c1, c3, 4, val);
1047 if ((val & 0x1) == 1)
1048 err = -EPERM;
1049 break;
1050 }
1051
1052 if (err) {
1053 pr_warn_once("CPU %d debug is powered down!\n", cpu);
1054 cpumask_or(&debug_err_mask, &debug_err_mask, cpumask_of(cpu));
1055 return;
1056 }
1057
1058 /*
1059 * Unconditionally clear the OS lock by writing a value
1060 * other than CS_LAR_KEY to the access register.
1061 */
1062 ARM_DBG_WRITE(c1, c0, 4, ~CORESIGHT_UNLOCK);
1063 isb();
1064
1065 /*
1066 * Clear any configured vector-catch events before
1067 * enabling monitor mode.
1068 */
1069clear_vcr:
1070 ARM_DBG_WRITE(c0, c7, 0, 0);
1071 isb();
1072
1073 if (cpumask_intersects(&debug_err_mask, cpumask_of(cpu))) {
1074 pr_warn_once("CPU %d failed to disable vector catch\n", cpu);
1075 return;
1076 }
1077
1078 /*
1079 * The control/value register pairs are UNKNOWN out of reset so
1080 * clear them to avoid spurious debug events.
1081 */
1082 raw_num_brps = get_num_brp_resources();
1083 for (i = 0; i < raw_num_brps; ++i) {
1084 write_wb_reg(ARM_BASE_BCR + i, 0UL);
1085 write_wb_reg(ARM_BASE_BVR + i, 0UL);
1086 }
1087
1088 for (i = 0; i < core_num_wrps; ++i) {
1089 write_wb_reg(ARM_BASE_WCR + i, 0UL);
1090 write_wb_reg(ARM_BASE_WVR + i, 0UL);
1091 }
1092
1093 if (cpumask_intersects(&debug_err_mask, cpumask_of(cpu))) {
1094 pr_warn_once("CPU %d failed to clear debug register pairs\n", cpu);
1095 return;
1096 }
1097
1098 /*
1099 * Have a crack at enabling monitor mode. We don't actually need
1100 * it yet, but reporting an error early is useful if it fails.
1101 */
1102out_mdbgen:
1103 if (enable_monitor_mode())
1104 cpumask_or(&debug_err_mask, &debug_err_mask, cpumask_of(cpu));
1105}
1106
1107static int dbg_reset_online(unsigned int cpu)
1108{
1109 local_irq_disable();
1110 reset_ctrl_regs(cpu);
1111 local_irq_enable();
1112 return 0;
1113}
1114
1115#ifdef CONFIG_CPU_PM
1116static int dbg_cpu_pm_notify(struct notifier_block *self, unsigned long action,
1117 void *v)
1118{
1119 if (action == CPU_PM_EXIT)
1120 reset_ctrl_regs(smp_processor_id());
1121
1122 return NOTIFY_OK;
1123}
1124
1125static struct notifier_block dbg_cpu_pm_nb = {
1126 .notifier_call = dbg_cpu_pm_notify,
1127};
1128
1129static void __init pm_init(void)
1130{
1131 cpu_pm_register_notifier(&dbg_cpu_pm_nb);
1132}
1133#else
1134static inline void pm_init(void)
1135{
1136}
1137#endif
1138
1139static int __init arch_hw_breakpoint_init(void)
1140{
1141 int ret;
1142
1143 debug_arch = get_debug_arch();
1144
1145 if (!debug_arch_supported()) {
1146 pr_info("debug architecture 0x%x unsupported.\n", debug_arch);
1147 return 0;
1148 }
1149
1150 /*
1151 * Scorpion CPUs (at least those in APQ8060) seem to set DBGPRSR.SPD
1152 * whenever a WFI is issued, even if the core is not powered down, in
1153 * violation of the architecture. When DBGPRSR.SPD is set, accesses to
1154 * breakpoint and watchpoint registers are treated as undefined, so
1155 * this results in boot time and runtime failures when these are
1156 * accessed and we unexpectedly take a trap.
1157 *
1158 * It's not clear if/how this can be worked around, so we blacklist
1159 * Scorpion CPUs to avoid these issues.
1160 */
1161 if (read_cpuid_part() == ARM_CPU_PART_SCORPION) {
1162 pr_info("Scorpion CPU detected. Hardware breakpoints and watchpoints disabled\n");
1163 return 0;
1164 }
1165
1166 has_ossr = core_has_os_save_restore();
1167
1168 /* Determine how many BRPs/WRPs are available. */
1169 core_num_brps = get_num_brps();
1170 core_num_wrps = get_num_wrps();
1171
1172 /*
1173 * We need to tread carefully here because DBGSWENABLE may be
1174 * driven low on this core and there isn't an architected way to
1175 * determine that.
1176 */
1177 cpus_read_lock();
1178 register_undef_hook(&debug_reg_hook);
1179
1180 /*
1181 * Register CPU notifier which resets the breakpoint resources. We
1182 * assume that a halting debugger will leave the world in a nice state
1183 * for us.
1184 */
1185 ret = cpuhp_setup_state_cpuslocked(CPUHP_AP_ONLINE_DYN,
1186 "arm/hw_breakpoint:online",
1187 dbg_reset_online, NULL);
1188 unregister_undef_hook(&debug_reg_hook);
1189 if (WARN_ON(ret < 0) || !cpumask_empty(&debug_err_mask)) {
1190 core_num_brps = 0;
1191 core_num_wrps = 0;
1192 if (ret > 0)
1193 cpuhp_remove_state_nocalls_cpuslocked(ret);
1194 cpus_read_unlock();
1195 return 0;
1196 }
1197
1198 pr_info("found %d " "%s" "breakpoint and %d watchpoint registers.\n",
1199 core_num_brps, core_has_mismatch_brps() ? "(+1 reserved) " :
1200 "", core_num_wrps);
1201
1202 /* Work out the maximum supported watchpoint length. */
1203 max_watchpoint_len = get_max_wp_len();
1204 pr_info("maximum watchpoint size is %u bytes.\n",
1205 max_watchpoint_len);
1206
1207 /* Register debug fault handler. */
1208 hook_fault_code(FAULT_CODE_DEBUG, hw_breakpoint_pending, SIGTRAP,
1209 TRAP_HWBKPT, "watchpoint debug exception");
1210 hook_ifault_code(FAULT_CODE_DEBUG, hw_breakpoint_pending, SIGTRAP,
1211 TRAP_HWBKPT, "breakpoint debug exception");
1212 cpus_read_unlock();
1213
1214 /* Register PM notifiers. */
1215 pm_init();
1216 return 0;
1217}
1218arch_initcall(arch_hw_breakpoint_init);
1219
1220void hw_breakpoint_pmu_read(struct perf_event *bp)
1221{
1222}
1223
1224/*
1225 * Dummy function to register with die_notifier.
1226 */
1227int hw_breakpoint_exceptions_notify(struct notifier_block *unused,
1228 unsigned long val, void *data)
1229{
1230 return NOTIFY_DONE;
1231}