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1/*
2 * This program is free software; you can redistribute it and/or modify
3 * it under the terms of the GNU General Public License 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
32#include <asm/cacheflush.h>
33#include <asm/cputype.h>
34#include <asm/current.h>
35#include <asm/hw_breakpoint.h>
36#include <asm/kdebug.h>
37#include <asm/system.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;
48static int core_num_reserved_brps;
49static int core_num_wrps;
50
51/* Debug architecture version. */
52static u8 debug_arch;
53
54/* Maximum supported watchpoint length. */
55static u8 max_watchpoint_len;
56
57#define READ_WB_REG_CASE(OP2, M, VAL) \
58 case ((OP2 << 4) + M): \
59 ARM_DBG_READ(c ## M, OP2, VAL); \
60 break
61
62#define WRITE_WB_REG_CASE(OP2, M, VAL) \
63 case ((OP2 << 4) + M): \
64 ARM_DBG_WRITE(c ## M, OP2, VAL);\
65 break
66
67#define GEN_READ_WB_REG_CASES(OP2, VAL) \
68 READ_WB_REG_CASE(OP2, 0, VAL); \
69 READ_WB_REG_CASE(OP2, 1, VAL); \
70 READ_WB_REG_CASE(OP2, 2, VAL); \
71 READ_WB_REG_CASE(OP2, 3, VAL); \
72 READ_WB_REG_CASE(OP2, 4, VAL); \
73 READ_WB_REG_CASE(OP2, 5, VAL); \
74 READ_WB_REG_CASE(OP2, 6, VAL); \
75 READ_WB_REG_CASE(OP2, 7, VAL); \
76 READ_WB_REG_CASE(OP2, 8, VAL); \
77 READ_WB_REG_CASE(OP2, 9, VAL); \
78 READ_WB_REG_CASE(OP2, 10, VAL); \
79 READ_WB_REG_CASE(OP2, 11, VAL); \
80 READ_WB_REG_CASE(OP2, 12, VAL); \
81 READ_WB_REG_CASE(OP2, 13, VAL); \
82 READ_WB_REG_CASE(OP2, 14, VAL); \
83 READ_WB_REG_CASE(OP2, 15, VAL)
84
85#define GEN_WRITE_WB_REG_CASES(OP2, VAL) \
86 WRITE_WB_REG_CASE(OP2, 0, VAL); \
87 WRITE_WB_REG_CASE(OP2, 1, VAL); \
88 WRITE_WB_REG_CASE(OP2, 2, VAL); \
89 WRITE_WB_REG_CASE(OP2, 3, VAL); \
90 WRITE_WB_REG_CASE(OP2, 4, VAL); \
91 WRITE_WB_REG_CASE(OP2, 5, VAL); \
92 WRITE_WB_REG_CASE(OP2, 6, VAL); \
93 WRITE_WB_REG_CASE(OP2, 7, VAL); \
94 WRITE_WB_REG_CASE(OP2, 8, VAL); \
95 WRITE_WB_REG_CASE(OP2, 9, VAL); \
96 WRITE_WB_REG_CASE(OP2, 10, VAL); \
97 WRITE_WB_REG_CASE(OP2, 11, VAL); \
98 WRITE_WB_REG_CASE(OP2, 12, VAL); \
99 WRITE_WB_REG_CASE(OP2, 13, VAL); \
100 WRITE_WB_REG_CASE(OP2, 14, VAL); \
101 WRITE_WB_REG_CASE(OP2, 15, VAL)
102
103static u32 read_wb_reg(int n)
104{
105 u32 val = 0;
106
107 switch (n) {
108 GEN_READ_WB_REG_CASES(ARM_OP2_BVR, val);
109 GEN_READ_WB_REG_CASES(ARM_OP2_BCR, val);
110 GEN_READ_WB_REG_CASES(ARM_OP2_WVR, val);
111 GEN_READ_WB_REG_CASES(ARM_OP2_WCR, val);
112 default:
113 pr_warning("attempt to read from unknown breakpoint "
114 "register %d\n", n);
115 }
116
117 return val;
118}
119
120static void write_wb_reg(int n, u32 val)
121{
122 switch (n) {
123 GEN_WRITE_WB_REG_CASES(ARM_OP2_BVR, val);
124 GEN_WRITE_WB_REG_CASES(ARM_OP2_BCR, val);
125 GEN_WRITE_WB_REG_CASES(ARM_OP2_WVR, val);
126 GEN_WRITE_WB_REG_CASES(ARM_OP2_WCR, val);
127 default:
128 pr_warning("attempt to write to unknown breakpoint "
129 "register %d\n", n);
130 }
131 isb();
132}
133
134/* Determine debug architecture. */
135static u8 get_debug_arch(void)
136{
137 u32 didr;
138
139 /* Do we implement the extended CPUID interface? */
140 if (WARN_ONCE((((read_cpuid_id() >> 16) & 0xf) != 0xf),
141 "CPUID feature registers not supported. "
142 "Assuming v6 debug is present.\n"))
143 return ARM_DEBUG_ARCH_V6;
144
145 ARM_DBG_READ(c0, 0, didr);
146 return (didr >> 16) & 0xf;
147}
148
149u8 arch_get_debug_arch(void)
150{
151 return debug_arch;
152}
153
154static int debug_arch_supported(void)
155{
156 u8 arch = get_debug_arch();
157 return arch >= ARM_DEBUG_ARCH_V6 && arch <= ARM_DEBUG_ARCH_V7_ECP14;
158}
159
160/* Determine number of BRP register available. */
161static int get_num_brp_resources(void)
162{
163 u32 didr;
164 ARM_DBG_READ(c0, 0, didr);
165 return ((didr >> 24) & 0xf) + 1;
166}
167
168/* Does this core support mismatch breakpoints? */
169static int core_has_mismatch_brps(void)
170{
171 return (get_debug_arch() >= ARM_DEBUG_ARCH_V7_ECP14 &&
172 get_num_brp_resources() > 1);
173}
174
175/* Determine number of usable WRPs available. */
176static int get_num_wrps(void)
177{
178 /*
179 * FIXME: When a watchpoint fires, the only way to work out which
180 * watchpoint it was is by disassembling the faulting instruction
181 * and working out the address of the memory access.
182 *
183 * Furthermore, we can only do this if the watchpoint was precise
184 * since imprecise watchpoints prevent us from calculating register
185 * based addresses.
186 *
187 * Providing we have more than 1 breakpoint register, we only report
188 * a single watchpoint register for the time being. This way, we always
189 * know which watchpoint fired. In the future we can either add a
190 * disassembler and address generation emulator, or we can insert a
191 * check to see if the DFAR is set on watchpoint exception entry
192 * [the ARM ARM states that the DFAR is UNKNOWN, but experience shows
193 * that it is set on some implementations].
194 */
195
196#if 0
197 int wrps;
198 u32 didr;
199 ARM_DBG_READ(c0, 0, didr);
200 wrps = ((didr >> 28) & 0xf) + 1;
201#endif
202 int wrps = 1;
203
204 if (core_has_mismatch_brps() && wrps >= get_num_brp_resources())
205 wrps = get_num_brp_resources() - 1;
206
207 return wrps;
208}
209
210/* We reserve one breakpoint for each watchpoint. */
211static int get_num_reserved_brps(void)
212{
213 if (core_has_mismatch_brps())
214 return get_num_wrps();
215 return 0;
216}
217
218/* Determine number of usable BRPs available. */
219static int get_num_brps(void)
220{
221 int brps = get_num_brp_resources();
222 if (core_has_mismatch_brps())
223 brps -= get_num_reserved_brps();
224 return brps;
225}
226
227/*
228 * In order to access the breakpoint/watchpoint control registers,
229 * we must be running in debug monitor mode. Unfortunately, we can
230 * be put into halting debug mode at any time by an external debugger
231 * but there is nothing we can do to prevent that.
232 */
233static int enable_monitor_mode(void)
234{
235 u32 dscr;
236 int ret = 0;
237
238 ARM_DBG_READ(c1, 0, dscr);
239
240 /* Ensure that halting mode is disabled. */
241 if (WARN_ONCE(dscr & ARM_DSCR_HDBGEN,
242 "halting debug mode enabled. Unable to access hardware resources.\n")) {
243 ret = -EPERM;
244 goto out;
245 }
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(c1, 0, (dscr | ARM_DSCR_MDBGEN));
256 break;
257 case ARM_DEBUG_ARCH_V7_ECP14:
258 ARM_DBG_WRITE(c2, 2, (dscr | ARM_DSCR_MDBGEN));
259 break;
260 default:
261 ret = -ENODEV;
262 goto out;
263 }
264
265 /* Check that the write made it through. */
266 ARM_DBG_READ(c1, 0, dscr);
267 if (!(dscr & ARM_DSCR_MDBGEN))
268 ret = -EPERM;
269
270out:
271 return ret;
272}
273
274int hw_breakpoint_slots(int type)
275{
276 if (!debug_arch_supported())
277 return 0;
278
279 /*
280 * We can be called early, so don't rely on
281 * our static variables being initialised.
282 */
283 switch (type) {
284 case TYPE_INST:
285 return get_num_brps();
286 case TYPE_DATA:
287 return get_num_wrps();
288 default:
289 pr_warning("unknown slot type: %d\n", type);
290 return 0;
291 }
292}
293
294/*
295 * Check if 8-bit byte-address select is available.
296 * This clobbers WRP 0.
297 */
298static u8 get_max_wp_len(void)
299{
300 u32 ctrl_reg;
301 struct arch_hw_breakpoint_ctrl ctrl;
302 u8 size = 4;
303
304 if (debug_arch < ARM_DEBUG_ARCH_V7_ECP14)
305 goto out;
306
307 memset(&ctrl, 0, sizeof(ctrl));
308 ctrl.len = ARM_BREAKPOINT_LEN_8;
309 ctrl_reg = encode_ctrl_reg(ctrl);
310
311 write_wb_reg(ARM_BASE_WVR, 0);
312 write_wb_reg(ARM_BASE_WCR, ctrl_reg);
313 if ((read_wb_reg(ARM_BASE_WCR) & ctrl_reg) == ctrl_reg)
314 size = 8;
315
316out:
317 return size;
318}
319
320u8 arch_get_max_wp_len(void)
321{
322 return max_watchpoint_len;
323}
324
325/*
326 * Install a perf counter breakpoint.
327 */
328int arch_install_hw_breakpoint(struct perf_event *bp)
329{
330 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
331 struct perf_event **slot, **slots;
332 int i, max_slots, ctrl_base, val_base, ret = 0;
333 u32 addr, ctrl;
334
335 /* Ensure that we are in monitor mode and halting mode is disabled. */
336 ret = enable_monitor_mode();
337 if (ret)
338 goto out;
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 = (struct perf_event **)__get_cpu_var(bp_on_reg);
348 max_slots = core_num_brps;
349 if (info->step_ctrl.enabled) {
350 /* Override the breakpoint data with the step data. */
351 addr = info->trigger & ~0x3;
352 ctrl = encode_ctrl_reg(info->step_ctrl);
353 }
354 } else {
355 /* Watchpoint */
356 if (info->step_ctrl.enabled) {
357 /* Install into the reserved breakpoint region. */
358 ctrl_base = ARM_BASE_BCR + core_num_brps;
359 val_base = ARM_BASE_BVR + core_num_brps;
360 /* Override the watchpoint data with the step data. */
361 addr = info->trigger & ~0x3;
362 ctrl = encode_ctrl_reg(info->step_ctrl);
363 } else {
364 ctrl_base = ARM_BASE_WCR;
365 val_base = ARM_BASE_WVR;
366 }
367 slots = (struct perf_event **)__get_cpu_var(wp_on_reg);
368 max_slots = core_num_wrps;
369 }
370
371 for (i = 0; i < max_slots; ++i) {
372 slot = &slots[i];
373
374 if (!*slot) {
375 *slot = bp;
376 break;
377 }
378 }
379
380 if (WARN_ONCE(i == max_slots, "Can't find any breakpoint slot\n")) {
381 ret = -EBUSY;
382 goto out;
383 }
384
385 /* Setup the address register. */
386 write_wb_reg(val_base + i, addr);
387
388 /* Setup the control register. */
389 write_wb_reg(ctrl_base + i, ctrl);
390
391out:
392 return ret;
393}
394
395void arch_uninstall_hw_breakpoint(struct perf_event *bp)
396{
397 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
398 struct perf_event **slot, **slots;
399 int i, max_slots, base;
400
401 if (info->ctrl.type == ARM_BREAKPOINT_EXECUTE) {
402 /* Breakpoint */
403 base = ARM_BASE_BCR;
404 slots = (struct perf_event **)__get_cpu_var(bp_on_reg);
405 max_slots = core_num_brps;
406 } else {
407 /* Watchpoint */
408 if (info->step_ctrl.enabled)
409 base = ARM_BASE_BCR + core_num_brps;
410 else
411 base = ARM_BASE_WCR;
412 slots = (struct perf_event **)__get_cpu_var(wp_on_reg);
413 max_slots = core_num_wrps;
414 }
415
416 /* Remove the breakpoint. */
417 for (i = 0; i < max_slots; ++i) {
418 slot = &slots[i];
419
420 if (*slot == bp) {
421 *slot = NULL;
422 break;
423 }
424 }
425
426 if (WARN_ONCE(i == max_slots, "Can't find any breakpoint slot\n"))
427 return;
428
429 /* Reset the control register. */
430 write_wb_reg(base + i, 0);
431}
432
433static int get_hbp_len(u8 hbp_len)
434{
435 unsigned int len_in_bytes = 0;
436
437 switch (hbp_len) {
438 case ARM_BREAKPOINT_LEN_1:
439 len_in_bytes = 1;
440 break;
441 case ARM_BREAKPOINT_LEN_2:
442 len_in_bytes = 2;
443 break;
444 case ARM_BREAKPOINT_LEN_4:
445 len_in_bytes = 4;
446 break;
447 case ARM_BREAKPOINT_LEN_8:
448 len_in_bytes = 8;
449 break;
450 }
451
452 return len_in_bytes;
453}
454
455/*
456 * Check whether bp virtual address is in kernel space.
457 */
458int arch_check_bp_in_kernelspace(struct perf_event *bp)
459{
460 unsigned int len;
461 unsigned long va;
462 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
463
464 va = info->address;
465 len = get_hbp_len(info->ctrl.len);
466
467 return (va >= TASK_SIZE) && ((va + len - 1) >= TASK_SIZE);
468}
469
470/*
471 * Extract generic type and length encodings from an arch_hw_breakpoint_ctrl.
472 * Hopefully this will disappear when ptrace can bypass the conversion
473 * to generic breakpoint descriptions.
474 */
475int arch_bp_generic_fields(struct arch_hw_breakpoint_ctrl ctrl,
476 int *gen_len, int *gen_type)
477{
478 /* Type */
479 switch (ctrl.type) {
480 case ARM_BREAKPOINT_EXECUTE:
481 *gen_type = HW_BREAKPOINT_X;
482 break;
483 case ARM_BREAKPOINT_LOAD:
484 *gen_type = HW_BREAKPOINT_R;
485 break;
486 case ARM_BREAKPOINT_STORE:
487 *gen_type = HW_BREAKPOINT_W;
488 break;
489 case ARM_BREAKPOINT_LOAD | ARM_BREAKPOINT_STORE:
490 *gen_type = HW_BREAKPOINT_RW;
491 break;
492 default:
493 return -EINVAL;
494 }
495
496 /* Len */
497 switch (ctrl.len) {
498 case ARM_BREAKPOINT_LEN_1:
499 *gen_len = HW_BREAKPOINT_LEN_1;
500 break;
501 case ARM_BREAKPOINT_LEN_2:
502 *gen_len = HW_BREAKPOINT_LEN_2;
503 break;
504 case ARM_BREAKPOINT_LEN_4:
505 *gen_len = HW_BREAKPOINT_LEN_4;
506 break;
507 case ARM_BREAKPOINT_LEN_8:
508 *gen_len = HW_BREAKPOINT_LEN_8;
509 break;
510 default:
511 return -EINVAL;
512 }
513
514 return 0;
515}
516
517/*
518 * Construct an arch_hw_breakpoint from a perf_event.
519 */
520static int arch_build_bp_info(struct perf_event *bp)
521{
522 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
523
524 /* Type */
525 switch (bp->attr.bp_type) {
526 case HW_BREAKPOINT_X:
527 info->ctrl.type = ARM_BREAKPOINT_EXECUTE;
528 break;
529 case HW_BREAKPOINT_R:
530 info->ctrl.type = ARM_BREAKPOINT_LOAD;
531 break;
532 case HW_BREAKPOINT_W:
533 info->ctrl.type = ARM_BREAKPOINT_STORE;
534 break;
535 case HW_BREAKPOINT_RW:
536 info->ctrl.type = ARM_BREAKPOINT_LOAD | ARM_BREAKPOINT_STORE;
537 break;
538 default:
539 return -EINVAL;
540 }
541
542 /* Len */
543 switch (bp->attr.bp_len) {
544 case HW_BREAKPOINT_LEN_1:
545 info->ctrl.len = ARM_BREAKPOINT_LEN_1;
546 break;
547 case HW_BREAKPOINT_LEN_2:
548 info->ctrl.len = ARM_BREAKPOINT_LEN_2;
549 break;
550 case HW_BREAKPOINT_LEN_4:
551 info->ctrl.len = ARM_BREAKPOINT_LEN_4;
552 break;
553 case HW_BREAKPOINT_LEN_8:
554 info->ctrl.len = ARM_BREAKPOINT_LEN_8;
555 if ((info->ctrl.type != ARM_BREAKPOINT_EXECUTE)
556 && max_watchpoint_len >= 8)
557 break;
558 default:
559 return -EINVAL;
560 }
561
562 /*
563 * Breakpoints must be of length 2 (thumb) or 4 (ARM) bytes.
564 * Watchpoints can be of length 1, 2, 4 or 8 bytes if supported
565 * by the hardware and must be aligned to the appropriate number of
566 * bytes.
567 */
568 if (info->ctrl.type == ARM_BREAKPOINT_EXECUTE &&
569 info->ctrl.len != ARM_BREAKPOINT_LEN_2 &&
570 info->ctrl.len != ARM_BREAKPOINT_LEN_4)
571 return -EINVAL;
572
573 /* Address */
574 info->address = bp->attr.bp_addr;
575
576 /* Privilege */
577 info->ctrl.privilege = ARM_BREAKPOINT_USER;
578 if (arch_check_bp_in_kernelspace(bp))
579 info->ctrl.privilege |= ARM_BREAKPOINT_PRIV;
580
581 /* Enabled? */
582 info->ctrl.enabled = !bp->attr.disabled;
583
584 /* Mismatch */
585 info->ctrl.mismatch = 0;
586
587 return 0;
588}
589
590/*
591 * Validate the arch-specific HW Breakpoint register settings.
592 */
593int arch_validate_hwbkpt_settings(struct perf_event *bp)
594{
595 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
596 int ret = 0;
597 u32 offset, alignment_mask = 0x3;
598
599 /* Build the arch_hw_breakpoint. */
600 ret = arch_build_bp_info(bp);
601 if (ret)
602 goto out;
603
604 /* Check address alignment. */
605 if (info->ctrl.len == ARM_BREAKPOINT_LEN_8)
606 alignment_mask = 0x7;
607 offset = info->address & alignment_mask;
608 switch (offset) {
609 case 0:
610 /* Aligned */
611 break;
612 case 1:
613 /* Allow single byte watchpoint. */
614 if (info->ctrl.len == ARM_BREAKPOINT_LEN_1)
615 break;
616 case 2:
617 /* Allow halfword watchpoints and breakpoints. */
618 if (info->ctrl.len == ARM_BREAKPOINT_LEN_2)
619 break;
620 default:
621 ret = -EINVAL;
622 goto out;
623 }
624
625 info->address &= ~alignment_mask;
626 info->ctrl.len <<= offset;
627
628 /*
629 * Currently we rely on an overflow handler to take
630 * care of single-stepping the breakpoint when it fires.
631 * In the case of userspace breakpoints on a core with V7 debug,
632 * we can use the mismatch feature as a poor-man's hardware
633 * single-step, but this only works for per-task breakpoints.
634 */
635 if (WARN_ONCE(!bp->overflow_handler &&
636 (arch_check_bp_in_kernelspace(bp) || !core_has_mismatch_brps()
637 || !bp->hw.bp_target),
638 "overflow handler required but none found\n")) {
639 ret = -EINVAL;
640 }
641out:
642 return ret;
643}
644
645/*
646 * Enable/disable single-stepping over the breakpoint bp at address addr.
647 */
648static void enable_single_step(struct perf_event *bp, u32 addr)
649{
650 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
651
652 arch_uninstall_hw_breakpoint(bp);
653 info->step_ctrl.mismatch = 1;
654 info->step_ctrl.len = ARM_BREAKPOINT_LEN_4;
655 info->step_ctrl.type = ARM_BREAKPOINT_EXECUTE;
656 info->step_ctrl.privilege = info->ctrl.privilege;
657 info->step_ctrl.enabled = 1;
658 info->trigger = addr;
659 arch_install_hw_breakpoint(bp);
660}
661
662static void disable_single_step(struct perf_event *bp)
663{
664 arch_uninstall_hw_breakpoint(bp);
665 counter_arch_bp(bp)->step_ctrl.enabled = 0;
666 arch_install_hw_breakpoint(bp);
667}
668
669static void watchpoint_handler(unsigned long unknown, struct pt_regs *regs)
670{
671 int i;
672 struct perf_event *wp, **slots;
673 struct arch_hw_breakpoint *info;
674
675 slots = (struct perf_event **)__get_cpu_var(wp_on_reg);
676
677 /* Without a disassembler, we can only handle 1 watchpoint. */
678 BUG_ON(core_num_wrps > 1);
679
680 for (i = 0; i < core_num_wrps; ++i) {
681 rcu_read_lock();
682
683 wp = slots[i];
684
685 if (wp == NULL) {
686 rcu_read_unlock();
687 continue;
688 }
689
690 /*
691 * The DFAR is an unknown value. Since we only allow a
692 * single watchpoint, we can set the trigger to the lowest
693 * possible faulting address.
694 */
695 info = counter_arch_bp(wp);
696 info->trigger = wp->attr.bp_addr;
697 pr_debug("watchpoint fired: address = 0x%x\n", info->trigger);
698 perf_bp_event(wp, regs);
699
700 /*
701 * If no overflow handler is present, insert a temporary
702 * mismatch breakpoint so we can single-step over the
703 * watchpoint trigger.
704 */
705 if (!wp->overflow_handler)
706 enable_single_step(wp, instruction_pointer(regs));
707
708 rcu_read_unlock();
709 }
710}
711
712static void watchpoint_single_step_handler(unsigned long pc)
713{
714 int i;
715 struct perf_event *wp, **slots;
716 struct arch_hw_breakpoint *info;
717
718 slots = (struct perf_event **)__get_cpu_var(wp_on_reg);
719
720 for (i = 0; i < core_num_reserved_brps; ++i) {
721 rcu_read_lock();
722
723 wp = slots[i];
724
725 if (wp == NULL)
726 goto unlock;
727
728 info = counter_arch_bp(wp);
729 if (!info->step_ctrl.enabled)
730 goto unlock;
731
732 /*
733 * Restore the original watchpoint if we've completed the
734 * single-step.
735 */
736 if (info->trigger != pc)
737 disable_single_step(wp);
738
739unlock:
740 rcu_read_unlock();
741 }
742}
743
744static void breakpoint_handler(unsigned long unknown, struct pt_regs *regs)
745{
746 int i;
747 u32 ctrl_reg, val, addr;
748 struct perf_event *bp, **slots;
749 struct arch_hw_breakpoint *info;
750 struct arch_hw_breakpoint_ctrl ctrl;
751
752 slots = (struct perf_event **)__get_cpu_var(bp_on_reg);
753
754 /* The exception entry code places the amended lr in the PC. */
755 addr = regs->ARM_pc;
756
757 /* Check the currently installed breakpoints first. */
758 for (i = 0; i < core_num_brps; ++i) {
759 rcu_read_lock();
760
761 bp = slots[i];
762
763 if (bp == NULL)
764 goto unlock;
765
766 info = counter_arch_bp(bp);
767
768 /* Check if the breakpoint value matches. */
769 val = read_wb_reg(ARM_BASE_BVR + i);
770 if (val != (addr & ~0x3))
771 goto mismatch;
772
773 /* Possible match, check the byte address select to confirm. */
774 ctrl_reg = read_wb_reg(ARM_BASE_BCR + i);
775 decode_ctrl_reg(ctrl_reg, &ctrl);
776 if ((1 << (addr & 0x3)) & ctrl.len) {
777 info->trigger = addr;
778 pr_debug("breakpoint fired: address = 0x%x\n", addr);
779 perf_bp_event(bp, regs);
780 if (!bp->overflow_handler)
781 enable_single_step(bp, addr);
782 goto unlock;
783 }
784
785mismatch:
786 /* If we're stepping a breakpoint, it can now be restored. */
787 if (info->step_ctrl.enabled)
788 disable_single_step(bp);
789unlock:
790 rcu_read_unlock();
791 }
792
793 /* Handle any pending watchpoint single-step breakpoints. */
794 watchpoint_single_step_handler(addr);
795}
796
797/*
798 * Called from either the Data Abort Handler [watchpoint] or the
799 * Prefetch Abort Handler [breakpoint] with interrupts disabled.
800 */
801static int hw_breakpoint_pending(unsigned long addr, unsigned int fsr,
802 struct pt_regs *regs)
803{
804 int ret = 0;
805 u32 dscr;
806
807 preempt_disable();
808
809 if (interrupts_enabled(regs))
810 local_irq_enable();
811
812 /* We only handle watchpoints and hardware breakpoints. */
813 ARM_DBG_READ(c1, 0, dscr);
814
815 /* Perform perf callbacks. */
816 switch (ARM_DSCR_MOE(dscr)) {
817 case ARM_ENTRY_BREAKPOINT:
818 breakpoint_handler(addr, regs);
819 break;
820 case ARM_ENTRY_ASYNC_WATCHPOINT:
821 WARN(1, "Asynchronous watchpoint exception taken. Debugging results may be unreliable\n");
822 case ARM_ENTRY_SYNC_WATCHPOINT:
823 watchpoint_handler(addr, regs);
824 break;
825 default:
826 ret = 1; /* Unhandled fault. */
827 }
828
829 preempt_enable();
830
831 return ret;
832}
833
834/*
835 * One-time initialisation.
836 */
837static void reset_ctrl_regs(void *info)
838{
839 int i, cpu = smp_processor_id();
840 u32 dbg_power;
841 cpumask_t *cpumask = info;
842
843 /*
844 * v7 debug contains save and restore registers so that debug state
845 * can be maintained across low-power modes without leaving the debug
846 * logic powered up. It is IMPLEMENTATION DEFINED whether we can access
847 * the debug registers out of reset, so we must unlock the OS Lock
848 * Access Register to avoid taking undefined instruction exceptions
849 * later on.
850 */
851 if (debug_arch >= ARM_DEBUG_ARCH_V7_ECP14) {
852 /*
853 * Ensure sticky power-down is clear (i.e. debug logic is
854 * powered up).
855 */
856 asm volatile("mrc p14, 0, %0, c1, c5, 4" : "=r" (dbg_power));
857 if ((dbg_power & 0x1) == 0) {
858 pr_warning("CPU %d debug is powered down!\n", cpu);
859 cpumask_or(cpumask, cpumask, cpumask_of(cpu));
860 return;
861 }
862
863 /*
864 * Unconditionally clear the lock by writing a value
865 * other than 0xC5ACCE55 to the access register.
866 */
867 asm volatile("mcr p14, 0, %0, c1, c0, 4" : : "r" (0));
868 isb();
869
870 /*
871 * Clear any configured vector-catch events before
872 * enabling monitor mode.
873 */
874 asm volatile("mcr p14, 0, %0, c0, c7, 0" : : "r" (0));
875 isb();
876 }
877
878 if (enable_monitor_mode())
879 return;
880
881 /* We must also reset any reserved registers. */
882 for (i = 0; i < core_num_brps + core_num_reserved_brps; ++i) {
883 write_wb_reg(ARM_BASE_BCR + i, 0UL);
884 write_wb_reg(ARM_BASE_BVR + i, 0UL);
885 }
886
887 for (i = 0; i < core_num_wrps; ++i) {
888 write_wb_reg(ARM_BASE_WCR + i, 0UL);
889 write_wb_reg(ARM_BASE_WVR + i, 0UL);
890 }
891}
892
893static int __cpuinit dbg_reset_notify(struct notifier_block *self,
894 unsigned long action, void *cpu)
895{
896 if (action == CPU_ONLINE)
897 smp_call_function_single((int)cpu, reset_ctrl_regs, NULL, 1);
898 return NOTIFY_OK;
899}
900
901static struct notifier_block __cpuinitdata dbg_reset_nb = {
902 .notifier_call = dbg_reset_notify,
903};
904
905static int __init arch_hw_breakpoint_init(void)
906{
907 u32 dscr;
908 cpumask_t cpumask = { CPU_BITS_NONE };
909
910 debug_arch = get_debug_arch();
911
912 if (!debug_arch_supported()) {
913 pr_info("debug architecture 0x%x unsupported.\n", debug_arch);
914 return 0;
915 }
916
917 /* Determine how many BRPs/WRPs are available. */
918 core_num_brps = get_num_brps();
919 core_num_reserved_brps = get_num_reserved_brps();
920 core_num_wrps = get_num_wrps();
921
922 pr_info("found %d breakpoint and %d watchpoint registers.\n",
923 core_num_brps + core_num_reserved_brps, core_num_wrps);
924
925 if (core_num_reserved_brps)
926 pr_info("%d breakpoint(s) reserved for watchpoint "
927 "single-step.\n", core_num_reserved_brps);
928
929 /*
930 * Reset the breakpoint resources. We assume that a halting
931 * debugger will leave the world in a nice state for us.
932 */
933 on_each_cpu(reset_ctrl_regs, &cpumask, 1);
934 if (!cpumask_empty(&cpumask)) {
935 core_num_brps = 0;
936 core_num_reserved_brps = 0;
937 core_num_wrps = 0;
938 return 0;
939 }
940
941 ARM_DBG_READ(c1, 0, dscr);
942 if (dscr & ARM_DSCR_HDBGEN) {
943 max_watchpoint_len = 4;
944 pr_warning("halting debug mode enabled. Assuming maximum watchpoint size of %u bytes.\n",
945 max_watchpoint_len);
946 } else {
947 /* Work out the maximum supported watchpoint length. */
948 max_watchpoint_len = get_max_wp_len();
949 pr_info("maximum watchpoint size is %u bytes.\n",
950 max_watchpoint_len);
951 }
952
953 /* Register debug fault handler. */
954 hook_fault_code(2, hw_breakpoint_pending, SIGTRAP, TRAP_HWBKPT,
955 "watchpoint debug exception");
956 hook_ifault_code(2, hw_breakpoint_pending, SIGTRAP, TRAP_HWBKPT,
957 "breakpoint debug exception");
958
959 /* Register hotplug notifier. */
960 register_cpu_notifier(&dbg_reset_nb);
961 return 0;
962}
963arch_initcall(arch_hw_breakpoint_init);
964
965void hw_breakpoint_pmu_read(struct perf_event *bp)
966{
967}
968
969/*
970 * Dummy function to register with die_notifier.
971 */
972int hw_breakpoint_exceptions_notify(struct notifier_block *unused,
973 unsigned long val, void *data)
974{
975 return NOTIFY_DONE;
976}
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
32#include <asm/cacheflush.h>
33#include <asm/cputype.h>
34#include <asm/current.h>
35#include <asm/hw_breakpoint.h>
36#include <asm/kdebug.h>
37#include <asm/traps.h>
38
39/* Breakpoint currently in use for each BRP. */
40static DEFINE_PER_CPU(struct perf_event *, bp_on_reg[ARM_MAX_BRP]);
41
42/* Watchpoint currently in use for each WRP. */
43static DEFINE_PER_CPU(struct perf_event *, wp_on_reg[ARM_MAX_WRP]);
44
45/* Number of BRP/WRP registers on this CPU. */
46static int core_num_brps;
47static int core_num_wrps;
48
49/* Debug architecture version. */
50static u8 debug_arch;
51
52/* Maximum supported watchpoint length. */
53static u8 max_watchpoint_len;
54
55#define READ_WB_REG_CASE(OP2, M, VAL) \
56 case ((OP2 << 4) + M): \
57 ARM_DBG_READ(c ## M, OP2, VAL); \
58 break
59
60#define WRITE_WB_REG_CASE(OP2, M, VAL) \
61 case ((OP2 << 4) + M): \
62 ARM_DBG_WRITE(c ## M, OP2, VAL);\
63 break
64
65#define GEN_READ_WB_REG_CASES(OP2, VAL) \
66 READ_WB_REG_CASE(OP2, 0, VAL); \
67 READ_WB_REG_CASE(OP2, 1, VAL); \
68 READ_WB_REG_CASE(OP2, 2, VAL); \
69 READ_WB_REG_CASE(OP2, 3, VAL); \
70 READ_WB_REG_CASE(OP2, 4, VAL); \
71 READ_WB_REG_CASE(OP2, 5, VAL); \
72 READ_WB_REG_CASE(OP2, 6, VAL); \
73 READ_WB_REG_CASE(OP2, 7, VAL); \
74 READ_WB_REG_CASE(OP2, 8, VAL); \
75 READ_WB_REG_CASE(OP2, 9, VAL); \
76 READ_WB_REG_CASE(OP2, 10, VAL); \
77 READ_WB_REG_CASE(OP2, 11, VAL); \
78 READ_WB_REG_CASE(OP2, 12, VAL); \
79 READ_WB_REG_CASE(OP2, 13, VAL); \
80 READ_WB_REG_CASE(OP2, 14, VAL); \
81 READ_WB_REG_CASE(OP2, 15, VAL)
82
83#define GEN_WRITE_WB_REG_CASES(OP2, VAL) \
84 WRITE_WB_REG_CASE(OP2, 0, VAL); \
85 WRITE_WB_REG_CASE(OP2, 1, VAL); \
86 WRITE_WB_REG_CASE(OP2, 2, VAL); \
87 WRITE_WB_REG_CASE(OP2, 3, VAL); \
88 WRITE_WB_REG_CASE(OP2, 4, VAL); \
89 WRITE_WB_REG_CASE(OP2, 5, VAL); \
90 WRITE_WB_REG_CASE(OP2, 6, VAL); \
91 WRITE_WB_REG_CASE(OP2, 7, VAL); \
92 WRITE_WB_REG_CASE(OP2, 8, VAL); \
93 WRITE_WB_REG_CASE(OP2, 9, VAL); \
94 WRITE_WB_REG_CASE(OP2, 10, VAL); \
95 WRITE_WB_REG_CASE(OP2, 11, VAL); \
96 WRITE_WB_REG_CASE(OP2, 12, VAL); \
97 WRITE_WB_REG_CASE(OP2, 13, VAL); \
98 WRITE_WB_REG_CASE(OP2, 14, VAL); \
99 WRITE_WB_REG_CASE(OP2, 15, VAL)
100
101static u32 read_wb_reg(int n)
102{
103 u32 val = 0;
104
105 switch (n) {
106 GEN_READ_WB_REG_CASES(ARM_OP2_BVR, val);
107 GEN_READ_WB_REG_CASES(ARM_OP2_BCR, val);
108 GEN_READ_WB_REG_CASES(ARM_OP2_WVR, val);
109 GEN_READ_WB_REG_CASES(ARM_OP2_WCR, val);
110 default:
111 pr_warning("attempt to read from unknown breakpoint "
112 "register %d\n", n);
113 }
114
115 return val;
116}
117
118static void write_wb_reg(int n, u32 val)
119{
120 switch (n) {
121 GEN_WRITE_WB_REG_CASES(ARM_OP2_BVR, val);
122 GEN_WRITE_WB_REG_CASES(ARM_OP2_BCR, val);
123 GEN_WRITE_WB_REG_CASES(ARM_OP2_WVR, val);
124 GEN_WRITE_WB_REG_CASES(ARM_OP2_WCR, val);
125 default:
126 pr_warning("attempt to write to unknown breakpoint "
127 "register %d\n", n);
128 }
129 isb();
130}
131
132/* Determine debug architecture. */
133static u8 get_debug_arch(void)
134{
135 u32 didr;
136
137 /* Do we implement the extended CPUID interface? */
138 if (((read_cpuid_id() >> 16) & 0xf) != 0xf) {
139 pr_warning("CPUID feature registers not supported. "
140 "Assuming v6 debug is present.\n");
141 return ARM_DEBUG_ARCH_V6;
142 }
143
144 ARM_DBG_READ(c0, 0, didr);
145 return (didr >> 16) & 0xf;
146}
147
148u8 arch_get_debug_arch(void)
149{
150 return debug_arch;
151}
152
153static int debug_arch_supported(void)
154{
155 u8 arch = get_debug_arch();
156
157 /* We don't support the memory-mapped interface. */
158 return (arch >= ARM_DEBUG_ARCH_V6 && arch <= ARM_DEBUG_ARCH_V7_ECP14) ||
159 arch >= ARM_DEBUG_ARCH_V7_1;
160}
161
162/* Can we determine the watchpoint access type from the fsr? */
163static int debug_exception_updates_fsr(void)
164{
165 return 0;
166}
167
168/* Determine number of WRP registers available. */
169static int get_num_wrp_resources(void)
170{
171 u32 didr;
172 ARM_DBG_READ(c0, 0, didr);
173 return ((didr >> 28) & 0xf) + 1;
174}
175
176/* Determine number of BRP registers available. */
177static int get_num_brp_resources(void)
178{
179 u32 didr;
180 ARM_DBG_READ(c0, 0, didr);
181 return ((didr >> 24) & 0xf) + 1;
182}
183
184/* Does this core support mismatch breakpoints? */
185static int core_has_mismatch_brps(void)
186{
187 return (get_debug_arch() >= ARM_DEBUG_ARCH_V7_ECP14 &&
188 get_num_brp_resources() > 1);
189}
190
191/* Determine number of usable WRPs available. */
192static int get_num_wrps(void)
193{
194 /*
195 * On debug architectures prior to 7.1, when a watchpoint fires, the
196 * only way to work out which watchpoint it was is by disassembling
197 * the faulting instruction and working out the address of the memory
198 * access.
199 *
200 * Furthermore, we can only do this if the watchpoint was precise
201 * since imprecise watchpoints prevent us from calculating register
202 * based addresses.
203 *
204 * Providing we have more than 1 breakpoint register, we only report
205 * a single watchpoint register for the time being. This way, we always
206 * know which watchpoint fired. In the future we can either add a
207 * disassembler and address generation emulator, or we can insert a
208 * check to see if the DFAR is set on watchpoint exception entry
209 * [the ARM ARM states that the DFAR is UNKNOWN, but experience shows
210 * that it is set on some implementations].
211 */
212 if (get_debug_arch() < ARM_DEBUG_ARCH_V7_1)
213 return 1;
214
215 return get_num_wrp_resources();
216}
217
218/* Determine number of usable BRPs available. */
219static int get_num_brps(void)
220{
221 int brps = get_num_brp_resources();
222 return core_has_mismatch_brps() ? brps - 1 : brps;
223}
224
225/*
226 * In order to access the breakpoint/watchpoint control registers,
227 * we must be running in debug monitor mode. Unfortunately, we can
228 * be put into halting debug mode at any time by an external debugger
229 * but there is nothing we can do to prevent that.
230 */
231static int enable_monitor_mode(void)
232{
233 u32 dscr;
234 int ret = 0;
235
236 ARM_DBG_READ(c1, 0, dscr);
237
238 /* Ensure that halting mode is disabled. */
239 if (WARN_ONCE(dscr & ARM_DSCR_HDBGEN,
240 "halting debug mode enabled. Unable to access hardware resources.\n")) {
241 ret = -EPERM;
242 goto out;
243 }
244
245 /* If monitor mode is already enabled, just return. */
246 if (dscr & ARM_DSCR_MDBGEN)
247 goto out;
248
249 /* Write to the corresponding DSCR. */
250 switch (get_debug_arch()) {
251 case ARM_DEBUG_ARCH_V6:
252 case ARM_DEBUG_ARCH_V6_1:
253 ARM_DBG_WRITE(c1, 0, (dscr | ARM_DSCR_MDBGEN));
254 break;
255 case ARM_DEBUG_ARCH_V7_ECP14:
256 case ARM_DEBUG_ARCH_V7_1:
257 ARM_DBG_WRITE(c2, 2, (dscr | ARM_DSCR_MDBGEN));
258 break;
259 default:
260 ret = -ENODEV;
261 goto out;
262 }
263
264 /* Check that the write made it through. */
265 ARM_DBG_READ(c1, 0, dscr);
266 if (!(dscr & ARM_DSCR_MDBGEN))
267 ret = -EPERM;
268
269out:
270 return ret;
271}
272
273int hw_breakpoint_slots(int type)
274{
275 if (!debug_arch_supported())
276 return 0;
277
278 /*
279 * We can be called early, so don't rely on
280 * our static variables being initialised.
281 */
282 switch (type) {
283 case TYPE_INST:
284 return get_num_brps();
285 case TYPE_DATA:
286 return get_num_wrps();
287 default:
288 pr_warning("unknown slot type: %d\n", type);
289 return 0;
290 }
291}
292
293/*
294 * Check if 8-bit byte-address select is available.
295 * This clobbers WRP 0.
296 */
297static u8 get_max_wp_len(void)
298{
299 u32 ctrl_reg;
300 struct arch_hw_breakpoint_ctrl ctrl;
301 u8 size = 4;
302
303 if (debug_arch < ARM_DEBUG_ARCH_V7_ECP14)
304 goto out;
305
306 memset(&ctrl, 0, sizeof(ctrl));
307 ctrl.len = ARM_BREAKPOINT_LEN_8;
308 ctrl_reg = encode_ctrl_reg(ctrl);
309
310 write_wb_reg(ARM_BASE_WVR, 0);
311 write_wb_reg(ARM_BASE_WCR, ctrl_reg);
312 if ((read_wb_reg(ARM_BASE_WCR) & ctrl_reg) == ctrl_reg)
313 size = 8;
314
315out:
316 return size;
317}
318
319u8 arch_get_max_wp_len(void)
320{
321 return max_watchpoint_len;
322}
323
324/*
325 * Install a perf counter breakpoint.
326 */
327int arch_install_hw_breakpoint(struct perf_event *bp)
328{
329 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
330 struct perf_event **slot, **slots;
331 int i, max_slots, ctrl_base, val_base, ret = 0;
332 u32 addr, ctrl;
333
334 /* Ensure that we are in monitor mode and halting mode is disabled. */
335 ret = enable_monitor_mode();
336 if (ret)
337 goto out;
338
339 addr = info->address;
340 ctrl = encode_ctrl_reg(info->ctrl) | 0x1;
341
342 if (info->ctrl.type == ARM_BREAKPOINT_EXECUTE) {
343 /* Breakpoint */
344 ctrl_base = ARM_BASE_BCR;
345 val_base = ARM_BASE_BVR;
346 slots = (struct perf_event **)__get_cpu_var(bp_on_reg);
347 max_slots = core_num_brps;
348 } else {
349 /* Watchpoint */
350 ctrl_base = ARM_BASE_WCR;
351 val_base = ARM_BASE_WVR;
352 slots = (struct perf_event **)__get_cpu_var(wp_on_reg);
353 max_slots = core_num_wrps;
354 }
355
356 for (i = 0; i < max_slots; ++i) {
357 slot = &slots[i];
358
359 if (!*slot) {
360 *slot = bp;
361 break;
362 }
363 }
364
365 if (WARN_ONCE(i == max_slots, "Can't find any breakpoint slot\n")) {
366 ret = -EBUSY;
367 goto out;
368 }
369
370 /* Override the breakpoint data with the step data. */
371 if (info->step_ctrl.enabled) {
372 addr = info->trigger & ~0x3;
373 ctrl = encode_ctrl_reg(info->step_ctrl);
374 if (info->ctrl.type != ARM_BREAKPOINT_EXECUTE) {
375 i = 0;
376 ctrl_base = ARM_BASE_BCR + core_num_brps;
377 val_base = ARM_BASE_BVR + core_num_brps;
378 }
379 }
380
381 /* Setup the address register. */
382 write_wb_reg(val_base + i, addr);
383
384 /* Setup the control register. */
385 write_wb_reg(ctrl_base + i, ctrl);
386
387out:
388 return ret;
389}
390
391void arch_uninstall_hw_breakpoint(struct perf_event *bp)
392{
393 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
394 struct perf_event **slot, **slots;
395 int i, max_slots, base;
396
397 if (info->ctrl.type == ARM_BREAKPOINT_EXECUTE) {
398 /* Breakpoint */
399 base = ARM_BASE_BCR;
400 slots = (struct perf_event **)__get_cpu_var(bp_on_reg);
401 max_slots = core_num_brps;
402 } else {
403 /* Watchpoint */
404 base = ARM_BASE_WCR;
405 slots = (struct perf_event **)__get_cpu_var(wp_on_reg);
406 max_slots = core_num_wrps;
407 }
408
409 /* Remove the breakpoint. */
410 for (i = 0; i < max_slots; ++i) {
411 slot = &slots[i];
412
413 if (*slot == bp) {
414 *slot = NULL;
415 break;
416 }
417 }
418
419 if (WARN_ONCE(i == max_slots, "Can't find any breakpoint slot\n"))
420 return;
421
422 /* Ensure that we disable the mismatch breakpoint. */
423 if (info->ctrl.type != ARM_BREAKPOINT_EXECUTE &&
424 info->step_ctrl.enabled) {
425 i = 0;
426 base = ARM_BASE_BCR + core_num_brps;
427 }
428
429 /* Reset the control register. */
430 write_wb_reg(base + i, 0);
431}
432
433static int get_hbp_len(u8 hbp_len)
434{
435 unsigned int len_in_bytes = 0;
436
437 switch (hbp_len) {
438 case ARM_BREAKPOINT_LEN_1:
439 len_in_bytes = 1;
440 break;
441 case ARM_BREAKPOINT_LEN_2:
442 len_in_bytes = 2;
443 break;
444 case ARM_BREAKPOINT_LEN_4:
445 len_in_bytes = 4;
446 break;
447 case ARM_BREAKPOINT_LEN_8:
448 len_in_bytes = 8;
449 break;
450 }
451
452 return len_in_bytes;
453}
454
455/*
456 * Check whether bp virtual address is in kernel space.
457 */
458int arch_check_bp_in_kernelspace(struct perf_event *bp)
459{
460 unsigned int len;
461 unsigned long va;
462 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
463
464 va = info->address;
465 len = get_hbp_len(info->ctrl.len);
466
467 return (va >= TASK_SIZE) && ((va + len - 1) >= TASK_SIZE);
468}
469
470/*
471 * Extract generic type and length encodings from an arch_hw_breakpoint_ctrl.
472 * Hopefully this will disappear when ptrace can bypass the conversion
473 * to generic breakpoint descriptions.
474 */
475int arch_bp_generic_fields(struct arch_hw_breakpoint_ctrl ctrl,
476 int *gen_len, int *gen_type)
477{
478 /* Type */
479 switch (ctrl.type) {
480 case ARM_BREAKPOINT_EXECUTE:
481 *gen_type = HW_BREAKPOINT_X;
482 break;
483 case ARM_BREAKPOINT_LOAD:
484 *gen_type = HW_BREAKPOINT_R;
485 break;
486 case ARM_BREAKPOINT_STORE:
487 *gen_type = HW_BREAKPOINT_W;
488 break;
489 case ARM_BREAKPOINT_LOAD | ARM_BREAKPOINT_STORE:
490 *gen_type = HW_BREAKPOINT_RW;
491 break;
492 default:
493 return -EINVAL;
494 }
495
496 /* Len */
497 switch (ctrl.len) {
498 case ARM_BREAKPOINT_LEN_1:
499 *gen_len = HW_BREAKPOINT_LEN_1;
500 break;
501 case ARM_BREAKPOINT_LEN_2:
502 *gen_len = HW_BREAKPOINT_LEN_2;
503 break;
504 case ARM_BREAKPOINT_LEN_4:
505 *gen_len = HW_BREAKPOINT_LEN_4;
506 break;
507 case ARM_BREAKPOINT_LEN_8:
508 *gen_len = HW_BREAKPOINT_LEN_8;
509 break;
510 default:
511 return -EINVAL;
512 }
513
514 return 0;
515}
516
517/*
518 * Construct an arch_hw_breakpoint from a perf_event.
519 */
520static int arch_build_bp_info(struct perf_event *bp)
521{
522 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
523
524 /* Type */
525 switch (bp->attr.bp_type) {
526 case HW_BREAKPOINT_X:
527 info->ctrl.type = ARM_BREAKPOINT_EXECUTE;
528 break;
529 case HW_BREAKPOINT_R:
530 info->ctrl.type = ARM_BREAKPOINT_LOAD;
531 break;
532 case HW_BREAKPOINT_W:
533 info->ctrl.type = ARM_BREAKPOINT_STORE;
534 break;
535 case HW_BREAKPOINT_RW:
536 info->ctrl.type = ARM_BREAKPOINT_LOAD | ARM_BREAKPOINT_STORE;
537 break;
538 default:
539 return -EINVAL;
540 }
541
542 /* Len */
543 switch (bp->attr.bp_len) {
544 case HW_BREAKPOINT_LEN_1:
545 info->ctrl.len = ARM_BREAKPOINT_LEN_1;
546 break;
547 case HW_BREAKPOINT_LEN_2:
548 info->ctrl.len = ARM_BREAKPOINT_LEN_2;
549 break;
550 case HW_BREAKPOINT_LEN_4:
551 info->ctrl.len = ARM_BREAKPOINT_LEN_4;
552 break;
553 case HW_BREAKPOINT_LEN_8:
554 info->ctrl.len = ARM_BREAKPOINT_LEN_8;
555 if ((info->ctrl.type != ARM_BREAKPOINT_EXECUTE)
556 && max_watchpoint_len >= 8)
557 break;
558 default:
559 return -EINVAL;
560 }
561
562 /*
563 * Breakpoints must be of length 2 (thumb) or 4 (ARM) bytes.
564 * Watchpoints can be of length 1, 2, 4 or 8 bytes if supported
565 * by the hardware and must be aligned to the appropriate number of
566 * bytes.
567 */
568 if (info->ctrl.type == ARM_BREAKPOINT_EXECUTE &&
569 info->ctrl.len != ARM_BREAKPOINT_LEN_2 &&
570 info->ctrl.len != ARM_BREAKPOINT_LEN_4)
571 return -EINVAL;
572
573 /* Address */
574 info->address = bp->attr.bp_addr;
575
576 /* Privilege */
577 info->ctrl.privilege = ARM_BREAKPOINT_USER;
578 if (arch_check_bp_in_kernelspace(bp))
579 info->ctrl.privilege |= ARM_BREAKPOINT_PRIV;
580
581 /* Enabled? */
582 info->ctrl.enabled = !bp->attr.disabled;
583
584 /* Mismatch */
585 info->ctrl.mismatch = 0;
586
587 return 0;
588}
589
590/*
591 * Validate the arch-specific HW Breakpoint register settings.
592 */
593int arch_validate_hwbkpt_settings(struct perf_event *bp)
594{
595 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
596 int ret = 0;
597 u32 offset, alignment_mask = 0x3;
598
599 /* Build the arch_hw_breakpoint. */
600 ret = arch_build_bp_info(bp);
601 if (ret)
602 goto out;
603
604 /* Check address alignment. */
605 if (info->ctrl.len == ARM_BREAKPOINT_LEN_8)
606 alignment_mask = 0x7;
607 offset = info->address & alignment_mask;
608 switch (offset) {
609 case 0:
610 /* Aligned */
611 break;
612 case 1:
613 /* Allow single byte watchpoint. */
614 if (info->ctrl.len == ARM_BREAKPOINT_LEN_1)
615 break;
616 case 2:
617 /* Allow halfword watchpoints and breakpoints. */
618 if (info->ctrl.len == ARM_BREAKPOINT_LEN_2)
619 break;
620 default:
621 ret = -EINVAL;
622 goto out;
623 }
624
625 info->address &= ~alignment_mask;
626 info->ctrl.len <<= offset;
627
628 if (!bp->overflow_handler) {
629 /*
630 * Mismatch breakpoints are required for single-stepping
631 * breakpoints.
632 */
633 if (!core_has_mismatch_brps())
634 return -EINVAL;
635
636 /* We don't allow mismatch breakpoints in kernel space. */
637 if (arch_check_bp_in_kernelspace(bp))
638 return -EPERM;
639
640 /*
641 * Per-cpu breakpoints are not supported by our stepping
642 * mechanism.
643 */
644 if (!bp->hw.bp_target)
645 return -EINVAL;
646
647 /*
648 * We only support specific access types if the fsr
649 * reports them.
650 */
651 if (!debug_exception_updates_fsr() &&
652 (info->ctrl.type == ARM_BREAKPOINT_LOAD ||
653 info->ctrl.type == ARM_BREAKPOINT_STORE))
654 return -EINVAL;
655 }
656
657out:
658 return ret;
659}
660
661/*
662 * Enable/disable single-stepping over the breakpoint bp at address addr.
663 */
664static void enable_single_step(struct perf_event *bp, u32 addr)
665{
666 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
667
668 arch_uninstall_hw_breakpoint(bp);
669 info->step_ctrl.mismatch = 1;
670 info->step_ctrl.len = ARM_BREAKPOINT_LEN_4;
671 info->step_ctrl.type = ARM_BREAKPOINT_EXECUTE;
672 info->step_ctrl.privilege = info->ctrl.privilege;
673 info->step_ctrl.enabled = 1;
674 info->trigger = addr;
675 arch_install_hw_breakpoint(bp);
676}
677
678static void disable_single_step(struct perf_event *bp)
679{
680 arch_uninstall_hw_breakpoint(bp);
681 counter_arch_bp(bp)->step_ctrl.enabled = 0;
682 arch_install_hw_breakpoint(bp);
683}
684
685static void watchpoint_handler(unsigned long addr, unsigned int fsr,
686 struct pt_regs *regs)
687{
688 int i, access;
689 u32 val, ctrl_reg, alignment_mask;
690 struct perf_event *wp, **slots;
691 struct arch_hw_breakpoint *info;
692 struct arch_hw_breakpoint_ctrl ctrl;
693
694 slots = (struct perf_event **)__get_cpu_var(wp_on_reg);
695
696 for (i = 0; i < core_num_wrps; ++i) {
697 rcu_read_lock();
698
699 wp = slots[i];
700
701 if (wp == NULL)
702 goto unlock;
703
704 info = counter_arch_bp(wp);
705 /*
706 * The DFAR is an unknown value on debug architectures prior
707 * to 7.1. Since we only allow a single watchpoint on these
708 * older CPUs, we can set the trigger to the lowest possible
709 * faulting address.
710 */
711 if (debug_arch < ARM_DEBUG_ARCH_V7_1) {
712 BUG_ON(i > 0);
713 info->trigger = wp->attr.bp_addr;
714 } else {
715 if (info->ctrl.len == ARM_BREAKPOINT_LEN_8)
716 alignment_mask = 0x7;
717 else
718 alignment_mask = 0x3;
719
720 /* Check if the watchpoint value matches. */
721 val = read_wb_reg(ARM_BASE_WVR + i);
722 if (val != (addr & ~alignment_mask))
723 goto unlock;
724
725 /* Possible match, check the byte address select. */
726 ctrl_reg = read_wb_reg(ARM_BASE_WCR + i);
727 decode_ctrl_reg(ctrl_reg, &ctrl);
728 if (!((1 << (addr & alignment_mask)) & ctrl.len))
729 goto unlock;
730
731 /* Check that the access type matches. */
732 if (debug_exception_updates_fsr()) {
733 access = (fsr & ARM_FSR_ACCESS_MASK) ?
734 HW_BREAKPOINT_W : HW_BREAKPOINT_R;
735 if (!(access & hw_breakpoint_type(wp)))
736 goto unlock;
737 }
738
739 /* We have a winner. */
740 info->trigger = addr;
741 }
742
743 pr_debug("watchpoint fired: address = 0x%x\n", info->trigger);
744 perf_bp_event(wp, regs);
745
746 /*
747 * If no overflow handler is present, insert a temporary
748 * mismatch breakpoint so we can single-step over the
749 * watchpoint trigger.
750 */
751 if (!wp->overflow_handler)
752 enable_single_step(wp, instruction_pointer(regs));
753
754unlock:
755 rcu_read_unlock();
756 }
757}
758
759static void watchpoint_single_step_handler(unsigned long pc)
760{
761 int i;
762 struct perf_event *wp, **slots;
763 struct arch_hw_breakpoint *info;
764
765 slots = (struct perf_event **)__get_cpu_var(wp_on_reg);
766
767 for (i = 0; i < core_num_wrps; ++i) {
768 rcu_read_lock();
769
770 wp = slots[i];
771
772 if (wp == NULL)
773 goto unlock;
774
775 info = counter_arch_bp(wp);
776 if (!info->step_ctrl.enabled)
777 goto unlock;
778
779 /*
780 * Restore the original watchpoint if we've completed the
781 * single-step.
782 */
783 if (info->trigger != pc)
784 disable_single_step(wp);
785
786unlock:
787 rcu_read_unlock();
788 }
789}
790
791static void breakpoint_handler(unsigned long unknown, struct pt_regs *regs)
792{
793 int i;
794 u32 ctrl_reg, val, addr;
795 struct perf_event *bp, **slots;
796 struct arch_hw_breakpoint *info;
797 struct arch_hw_breakpoint_ctrl ctrl;
798
799 slots = (struct perf_event **)__get_cpu_var(bp_on_reg);
800
801 /* The exception entry code places the amended lr in the PC. */
802 addr = regs->ARM_pc;
803
804 /* Check the currently installed breakpoints first. */
805 for (i = 0; i < core_num_brps; ++i) {
806 rcu_read_lock();
807
808 bp = slots[i];
809
810 if (bp == NULL)
811 goto unlock;
812
813 info = counter_arch_bp(bp);
814
815 /* Check if the breakpoint value matches. */
816 val = read_wb_reg(ARM_BASE_BVR + i);
817 if (val != (addr & ~0x3))
818 goto mismatch;
819
820 /* Possible match, check the byte address select to confirm. */
821 ctrl_reg = read_wb_reg(ARM_BASE_BCR + i);
822 decode_ctrl_reg(ctrl_reg, &ctrl);
823 if ((1 << (addr & 0x3)) & ctrl.len) {
824 info->trigger = addr;
825 pr_debug("breakpoint fired: address = 0x%x\n", addr);
826 perf_bp_event(bp, regs);
827 if (!bp->overflow_handler)
828 enable_single_step(bp, addr);
829 goto unlock;
830 }
831
832mismatch:
833 /* If we're stepping a breakpoint, it can now be restored. */
834 if (info->step_ctrl.enabled)
835 disable_single_step(bp);
836unlock:
837 rcu_read_unlock();
838 }
839
840 /* Handle any pending watchpoint single-step breakpoints. */
841 watchpoint_single_step_handler(addr);
842}
843
844/*
845 * Called from either the Data Abort Handler [watchpoint] or the
846 * Prefetch Abort Handler [breakpoint] with interrupts disabled.
847 */
848static int hw_breakpoint_pending(unsigned long addr, unsigned int fsr,
849 struct pt_regs *regs)
850{
851 int ret = 0;
852 u32 dscr;
853
854 preempt_disable();
855
856 if (interrupts_enabled(regs))
857 local_irq_enable();
858
859 /* We only handle watchpoints and hardware breakpoints. */
860 ARM_DBG_READ(c1, 0, dscr);
861
862 /* Perform perf callbacks. */
863 switch (ARM_DSCR_MOE(dscr)) {
864 case ARM_ENTRY_BREAKPOINT:
865 breakpoint_handler(addr, regs);
866 break;
867 case ARM_ENTRY_ASYNC_WATCHPOINT:
868 WARN(1, "Asynchronous watchpoint exception taken. Debugging results may be unreliable\n");
869 case ARM_ENTRY_SYNC_WATCHPOINT:
870 watchpoint_handler(addr, fsr, regs);
871 break;
872 default:
873 ret = 1; /* Unhandled fault. */
874 }
875
876 preempt_enable();
877
878 return ret;
879}
880
881/*
882 * One-time initialisation.
883 */
884static cpumask_t debug_err_mask;
885
886static int debug_reg_trap(struct pt_regs *regs, unsigned int instr)
887{
888 int cpu = smp_processor_id();
889
890 pr_warning("Debug register access (0x%x) caused undefined instruction on CPU %d\n",
891 instr, cpu);
892
893 /* Set the error flag for this CPU and skip the faulting instruction. */
894 cpumask_set_cpu(cpu, &debug_err_mask);
895 instruction_pointer(regs) += 4;
896 return 0;
897}
898
899static struct undef_hook debug_reg_hook = {
900 .instr_mask = 0x0fe80f10,
901 .instr_val = 0x0e000e10,
902 .fn = debug_reg_trap,
903};
904
905static void reset_ctrl_regs(void *unused)
906{
907 int i, raw_num_brps, err = 0, cpu = smp_processor_id();
908 u32 dbg_power;
909
910 /*
911 * v7 debug contains save and restore registers so that debug state
912 * can be maintained across low-power modes without leaving the debug
913 * logic powered up. It is IMPLEMENTATION DEFINED whether we can access
914 * the debug registers out of reset, so we must unlock the OS Lock
915 * Access Register to avoid taking undefined instruction exceptions
916 * later on.
917 */
918 switch (debug_arch) {
919 case ARM_DEBUG_ARCH_V6:
920 case ARM_DEBUG_ARCH_V6_1:
921 /* ARMv6 cores just need to reset the registers. */
922 goto reset_regs;
923 case ARM_DEBUG_ARCH_V7_ECP14:
924 /*
925 * Ensure sticky power-down is clear (i.e. debug logic is
926 * powered up).
927 */
928 asm volatile("mrc p14, 0, %0, c1, c5, 4" : "=r" (dbg_power));
929 if ((dbg_power & 0x1) == 0)
930 err = -EPERM;
931 break;
932 case ARM_DEBUG_ARCH_V7_1:
933 /*
934 * Ensure the OS double lock is clear.
935 */
936 asm volatile("mrc p14, 0, %0, c1, c3, 4" : "=r" (dbg_power));
937 if ((dbg_power & 0x1) == 1)
938 err = -EPERM;
939 break;
940 }
941
942 if (err) {
943 pr_warning("CPU %d debug is powered down!\n", cpu);
944 cpumask_or(&debug_err_mask, &debug_err_mask, cpumask_of(cpu));
945 return;
946 }
947
948 /*
949 * Unconditionally clear the lock by writing a value
950 * other than 0xC5ACCE55 to the access register.
951 */
952 asm volatile("mcr p14, 0, %0, c1, c0, 4" : : "r" (0));
953 isb();
954
955 /*
956 * Clear any configured vector-catch events before
957 * enabling monitor mode.
958 */
959 asm volatile("mcr p14, 0, %0, c0, c7, 0" : : "r" (0));
960 isb();
961
962reset_regs:
963 if (enable_monitor_mode())
964 return;
965
966 /* We must also reset any reserved registers. */
967 raw_num_brps = get_num_brp_resources();
968 for (i = 0; i < raw_num_brps; ++i) {
969 write_wb_reg(ARM_BASE_BCR + i, 0UL);
970 write_wb_reg(ARM_BASE_BVR + i, 0UL);
971 }
972
973 for (i = 0; i < core_num_wrps; ++i) {
974 write_wb_reg(ARM_BASE_WCR + i, 0UL);
975 write_wb_reg(ARM_BASE_WVR + i, 0UL);
976 }
977}
978
979static int __cpuinit dbg_reset_notify(struct notifier_block *self,
980 unsigned long action, void *cpu)
981{
982 if (action == CPU_ONLINE)
983 smp_call_function_single((int)cpu, reset_ctrl_regs, NULL, 1);
984
985 return NOTIFY_OK;
986}
987
988static struct notifier_block __cpuinitdata dbg_reset_nb = {
989 .notifier_call = dbg_reset_notify,
990};
991
992static int __init arch_hw_breakpoint_init(void)
993{
994 u32 dscr;
995
996 debug_arch = get_debug_arch();
997
998 if (!debug_arch_supported()) {
999 pr_info("debug architecture 0x%x unsupported.\n", debug_arch);
1000 return 0;
1001 }
1002
1003 /* Determine how many BRPs/WRPs are available. */
1004 core_num_brps = get_num_brps();
1005 core_num_wrps = get_num_wrps();
1006
1007 /*
1008 * We need to tread carefully here because DBGSWENABLE may be
1009 * driven low on this core and there isn't an architected way to
1010 * determine that.
1011 */
1012 register_undef_hook(&debug_reg_hook);
1013
1014 /*
1015 * Reset the breakpoint resources. We assume that a halting
1016 * debugger will leave the world in a nice state for us.
1017 */
1018 on_each_cpu(reset_ctrl_regs, NULL, 1);
1019 unregister_undef_hook(&debug_reg_hook);
1020 if (!cpumask_empty(&debug_err_mask)) {
1021 core_num_brps = 0;
1022 core_num_wrps = 0;
1023 return 0;
1024 }
1025
1026 pr_info("found %d " "%s" "breakpoint and %d watchpoint registers.\n",
1027 core_num_brps, core_has_mismatch_brps() ? "(+1 reserved) " :
1028 "", core_num_wrps);
1029
1030 ARM_DBG_READ(c1, 0, dscr);
1031 if (dscr & ARM_DSCR_HDBGEN) {
1032 max_watchpoint_len = 4;
1033 pr_warning("halting debug mode enabled. Assuming maximum watchpoint size of %u bytes.\n",
1034 max_watchpoint_len);
1035 } else {
1036 /* Work out the maximum supported watchpoint length. */
1037 max_watchpoint_len = get_max_wp_len();
1038 pr_info("maximum watchpoint size is %u bytes.\n",
1039 max_watchpoint_len);
1040 }
1041
1042 /* Register debug fault handler. */
1043 hook_fault_code(FAULT_CODE_DEBUG, hw_breakpoint_pending, SIGTRAP,
1044 TRAP_HWBKPT, "watchpoint debug exception");
1045 hook_ifault_code(FAULT_CODE_DEBUG, hw_breakpoint_pending, SIGTRAP,
1046 TRAP_HWBKPT, "breakpoint debug exception");
1047
1048 /* Register hotplug notifier. */
1049 register_cpu_notifier(&dbg_reset_nb);
1050 return 0;
1051}
1052arch_initcall(arch_hw_breakpoint_init);
1053
1054void hw_breakpoint_pmu_read(struct perf_event *bp)
1055{
1056}
1057
1058/*
1059 * Dummy function to register with die_notifier.
1060 */
1061int hw_breakpoint_exceptions_notify(struct notifier_block *unused,
1062 unsigned long val, void *data)
1063{
1064 return NOTIFY_DONE;
1065}