aboutsummaryrefslogtreecommitdiffstats
path: root/arch/sh/kernel/hw_breakpoint.c
blob: 1f2cf6229862e47f9a311652cb6e5cf4c34585c4 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
/*
 * arch/sh/kernel/hw_breakpoint.c
 *
 * Unified kernel/user-space hardware breakpoint facility for the on-chip UBC.
 *
 * Copyright (C) 2009 - 2010  Paul Mundt
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 */
#include <linux/init.h>
#include <linux/perf_event.h>
#include <linux/hw_breakpoint.h>
#include <linux/percpu.h>
#include <linux/kallsyms.h>
#include <linux/notifier.h>
#include <linux/kprobes.h>
#include <linux/kdebug.h>
#include <linux/io.h>
#include <linux/clk.h>
#include <asm/hw_breakpoint.h>
#include <asm/mmu_context.h>
#include <asm/ptrace.h>

/*
 * Stores the breakpoints currently in use on each breakpoint address
 * register for each cpus
 */
static DEFINE_PER_CPU(struct perf_event *, bp_per_reg[HBP_NUM]);

/*
 * A dummy placeholder for early accesses until the CPUs get a chance to
 * register their UBCs later in the boot process.
 */
static struct sh_ubc ubc_dummy = { .num_events = 0 };

static struct sh_ubc *sh_ubc __read_mostly = &ubc_dummy;

/*
 * Install a perf counter breakpoint.
 *
 * We seek a free UBC channel and use it for this breakpoint.
 *
 * Atomic: we hold the counter->ctx->lock and we only handle variables
 * and registers local to this cpu.
 */
int arch_install_hw_breakpoint(struct perf_event *bp)
{
	struct arch_hw_breakpoint *info = counter_arch_bp(bp);
	int i;

	for (i = 0; i < sh_ubc->num_events; i++) {
		struct perf_event **slot = &__get_cpu_var(bp_per_reg[i]);

		if (!*slot) {
			*slot = bp;
			break;
		}
	}

	if (WARN_ONCE(i == sh_ubc->num_events, "Can't find any breakpoint slot"))
		return -EBUSY;

	clk_enable(sh_ubc->clk);
	sh_ubc->enable(info, i);

	return 0;
}

/*
 * Uninstall the breakpoint contained in the given counter.
 *
 * First we search the debug address register it uses and then we disable
 * it.
 *
 * Atomic: we hold the counter->ctx->lock and we only handle variables
 * and registers local to this cpu.
 */
void arch_uninstall_hw_breakpoint(struct perf_event *bp)
{
	struct arch_hw_breakpoint *info = counter_arch_bp(bp);
	int i;

	for (i = 0; i < sh_ubc->num_events; i++) {
		struct perf_event **slot = &__get_cpu_var(bp_per_reg[i]);

		if (*slot == bp) {
			*slot = NULL;
			break;
		}
	}

	if (WARN_ONCE(i == sh_ubc->num_events, "Can't find any breakpoint slot"))
		return;

	sh_ubc->disable(info, i);
	clk_disable(sh_ubc->clk);
}

static int get_hbp_len(u16 hbp_len)
{
	unsigned int len_in_bytes = 0;

	switch (hbp_len) {
	case SH_BREAKPOINT_LEN_1:
		len_in_bytes = 1;
		break;
	case SH_BREAKPOINT_LEN_2:
		len_in_bytes = 2;
		break;
	case SH_BREAKPOINT_LEN_4:
		len_in_bytes = 4;
		break;
	case SH_BREAKPOINT_LEN_8:
		len_in_bytes = 8;
		break;
	}
	return len_in_bytes;
}

/*
 * Check for virtual address in kernel space.
 */
int arch_check_bp_in_kernelspace(struct perf_event *bp)
{
	unsigned int len;
	unsigned long va;
	struct arch_hw_breakpoint *info = counter_arch_bp(bp);

	va = info->address;
	len = get_hbp_len(info->len);

	return (va >= TASK_SIZE) && ((va + len - 1) >= TASK_SIZE);
}

int arch_bp_generic_fields(int sh_len, int sh_type,
			   int *gen_len, int *gen_type)
{
	/* Len */
	switch (sh_len) {
	case SH_BREAKPOINT_LEN_1:
		*gen_len = HW_BREAKPOINT_LEN_1;
		break;
	case SH_BREAKPOINT_LEN_2:
		*gen_len = HW_BREAKPOINT_LEN_2;
		break;
	case SH_BREAKPOINT_LEN_4:
		*gen_len = HW_BREAKPOINT_LEN_4;
		break;
	case SH_BREAKPOINT_LEN_8:
		*gen_len = HW_BREAKPOINT_LEN_8;
		break;
	default:
		return -EINVAL;
	}

	/* Type */
	switch (sh_type) {
	case SH_BREAKPOINT_READ:
		*gen_type = HW_BREAKPOINT_R;
	case SH_BREAKPOINT_WRITE:
		*gen_type = HW_BREAKPOINT_W;
		break;
	case SH_BREAKPOINT_RW:
		*gen_type = HW_BREAKPOINT_W | HW_BREAKPOINT_R;
		break;
	default:
		return -EINVAL;
	}

	return 0;
}

static int arch_build_bp_info(struct perf_event *bp)
{
	struct arch_hw_breakpoint *info = counter_arch_bp(bp);

	info->address = bp->attr.bp_addr;

	/* Len */
	switch (bp->attr.bp_len) {
	case HW_BREAKPOINT_LEN_1:
		info->len = SH_BREAKPOINT_LEN_1;
		break;
	case HW_BREAKPOINT_LEN_2:
		info->len = SH_BREAKPOINT_LEN_2;
		break;
	case HW_BREAKPOINT_LEN_4:
		info->len = SH_BREAKPOINT_LEN_4;
		break;
	case HW_BREAKPOINT_LEN_8:
		info->len = SH_BREAKPOINT_LEN_8;
		break;
	default:
		return -EINVAL;
	}

	/* Type */
	switch (bp->attr.bp_type) {
	case HW_BREAKPOINT_R:
		info->type = SH_BREAKPOINT_READ;
		break;
	case HW_BREAKPOINT_W:
		info->type = SH_BREAKPOINT_WRITE;
		break;
	case HW_BREAKPOINT_W | HW_BREAKPOINT_R:
		info->type = SH_BREAKPOINT_RW;
		break;
	default:
		return -EINVAL;
	}

	return 0;
}

/*
 * Validate the arch-specific HW Breakpoint register settings
 */
int arch_validate_hwbkpt_settings(struct perf_event *bp)
{
	struct arch_hw_breakpoint *info = counter_arch_bp(bp);
	unsigned int align;
	int ret;

	ret = arch_build_bp_info(bp);
	if (ret)
		return ret;

	ret = -EINVAL;

	switch (info->len) {
	case SH_BREAKPOINT_LEN_1:
		align = 0;
		break;
	case SH_BREAKPOINT_LEN_2:
		align = 1;
		break;
	case SH_BREAKPOINT_LEN_4:
		align = 3;
		break;
	case SH_BREAKPOINT_LEN_8:
		align = 7;
		break;
	default:
		return ret;
	}

	/*
	 * For kernel-addresses, either the address or symbol name can be
	 * specified.
	 */
	if (info->name)
		info->address = (unsigned long)kallsyms_lookup_name(info->name);

	/*
	 * Check that the low-order bits of the address are appropriate
	 * for the alignment implied by len.
	 */
	if (info->address & align)
		return -EINVAL;

	return 0;
}

/*
 * Release the user breakpoints used by ptrace
 */
void flush_ptrace_hw_breakpoint(struct task_struct *tsk)
{
	int i;
	struct thread_struct *t = &tsk->thread;

	for (i = 0; i < sh_ubc->num_events; i++) {
		unregister_hw_breakpoint(t->ptrace_bps[i]);
		t->ptrace_bps[i] = NULL;
	}
}

static int __kprobes hw_breakpoint_handler(struct die_args *args)
{
	int cpu, i, rc = NOTIFY_STOP;
	struct perf_event *bp;
	unsigned int cmf, resume_mask;

	/*
	 * Do an early return if none of the channels triggered.
	 */
	cmf = sh_ubc->triggered_mask();
	if (unlikely(!cmf))
		return NOTIFY_DONE;

	/*
	 * By default, resume all of the active channels.
	 */
	resume_mask = sh_ubc->active_mask();

	/*
	 * Disable breakpoints during exception handling.
	 */
	sh_ubc->disable_all();

	cpu = get_cpu();
	for (i = 0; i < sh_ubc->num_events; i++) {
		unsigned long event_mask = (1 << i);

		if (likely(!(cmf & event_mask)))
			continue;

		/*
		 * The counter may be concurrently released but that can only
		 * occur from a call_rcu() path. We can then safely fetch
		 * the breakpoint, use its callback, touch its counter
		 * while we are in an rcu_read_lock() path.
		 */
		rcu_read_lock();

		bp = per_cpu(bp_per_reg[i], cpu);
		if (bp)
			rc = NOTIFY_DONE;

		/*
		 * Reset the condition match flag to denote completion of
		 * exception handling.
		 */
		sh_ubc->clear_triggered_mask(event_mask);

		/*
		 * bp can be NULL due to concurrent perf counter
		 * removing.
		 */
		if (!bp) {
			rcu_read_unlock();
			break;
		}

		/*
		 * Don't restore the channel if the breakpoint is from
		 * ptrace, as it always operates in one-shot mode.
		 */
		if (bp->overflow_handler == ptrace_triggered)
			resume_mask &= ~(1 << i);

		perf_bp_event(bp, args->regs);

		/* Deliver the signal to userspace */
		if (!arch_check_bp_in_kernelspace(bp)) {
			siginfo_t info;

			info.si_signo = args->signr;
			info.si_errno = notifier_to_errno(rc);
			info.si_code = TRAP_HWBKPT;

			force_sig_info(args->signr, &info, current);
		}

		rcu_read_unlock();
	}

	if (cmf == 0)
		rc = NOTIFY_DONE;

	sh_ubc->enable_all(resume_mask);

	put_cpu();

	return rc;
}

BUILD_TRAP_HANDLER(breakpoint)
{
	unsigned long ex = lookup_exception_vector();
	TRAP_HANDLER_DECL;

	notify_die(DIE_BREAKPOINT, "breakpoint", regs, 0, ex, SIGTRAP);
}

/*
 * Handle debug exception notifications.
 */
int __kprobes hw_breakpoint_exceptions_notify(struct notifier_block *unused,
				    unsigned long val, void *data)
{
	struct die_args *args = data;

	if (val != DIE_BREAKPOINT)
		return NOTIFY_DONE;

	/*
	 * If the breakpoint hasn't been triggered by the UBC, it's
	 * probably from a debugger, so don't do anything more here.
	 *
	 * This also permits the UBC interface clock to remain off for
	 * non-UBC breakpoints, as we don't need to check the triggered
	 * or active channel masks.
	 */
	if (args->trapnr != sh_ubc->trap_nr)
		return NOTIFY_DONE;

	return hw_breakpoint_handler(data);
}

void hw_breakpoint_pmu_read(struct perf_event *bp)
{
	/* TODO */
}

void hw_breakpoint_pmu_unthrottle(struct perf_event *bp)
{
	/* TODO */
}

int register_sh_ubc(struct sh_ubc *ubc)
{
	/* Bail if it's already assigned */
	if (sh_ubc != &ubc_dummy)
		return -EBUSY;
	sh_ubc = ubc;

	pr_info("HW Breakpoints: %s UBC support registered\n", ubc->name);

	WARN_ON(ubc->num_events > HBP_NUM);

	return 0;
}