aboutsummaryrefslogtreecommitdiff
path: root/kernel/trace/trace_ksym.c
blob: ddfa0fd43bc0ebab1fa4953918a41323f409e08a (plain)
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
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
/*
 * trace_ksym.c - Kernel Symbol Tracer
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 * Copyright (C) IBM Corporation, 2009
 */

#include <linux/kallsyms.h>
#include <linux/uaccess.h>
#include <linux/debugfs.h>
#include <linux/ftrace.h>
#include <linux/module.h>
#include <linux/fs.h>

#include "trace_output.h"
#include "trace_stat.h"
#include "trace.h"

#include <linux/hw_breakpoint.h>
#include <asm/hw_breakpoint.h>

/*
 * For now, let us restrict the no. of symbols traced simultaneously to number
 * of available hardware breakpoint registers.
 */
#define KSYM_TRACER_MAX HBP_NUM

#define KSYM_TRACER_OP_LEN 3 /* rw- */

struct trace_ksym {
	struct perf_event	**ksym_hbp;
	struct perf_event_attr	attr;
#ifdef CONFIG_PROFILE_KSYM_TRACER
	unsigned long		counter;
#endif
	struct hlist_node	ksym_hlist;
};

static struct trace_array *ksym_trace_array;

static unsigned int ksym_filter_entry_count;
static unsigned int ksym_tracing_enabled;

static HLIST_HEAD(ksym_filter_head);

static DEFINE_MUTEX(ksym_tracer_mutex);

#ifdef CONFIG_PROFILE_KSYM_TRACER

#define MAX_UL_INT 0xffffffff

void ksym_collect_stats(unsigned long hbp_hit_addr)
{
	struct hlist_node *node;
	struct trace_ksym *entry;

	rcu_read_lock();
	hlist_for_each_entry_rcu(entry, node, &ksym_filter_head, ksym_hlist) {
		if ((entry->attr.bp_addr == hbp_hit_addr) &&
		    (entry->counter <= MAX_UL_INT)) {
			entry->counter++;
			break;
		}
	}
	rcu_read_unlock();
}
#endif /* CONFIG_PROFILE_KSYM_TRACER */

void ksym_hbp_handler(struct perf_event *hbp, void *data)
{
	struct ring_buffer_event *event;
	struct ksym_trace_entry *entry;
	struct pt_regs *regs = data;
	struct ring_buffer *buffer;
	int pc;

	if (!ksym_tracing_enabled)
		return;

	buffer = ksym_trace_array->buffer;

	pc = preempt_count();

	event = trace_buffer_lock_reserve(buffer, TRACE_KSYM,
							sizeof(*entry), 0, pc);
	if (!event)
		return;

	entry		= ring_buffer_event_data(event);
	entry->ip	= instruction_pointer(regs);
	entry->type	= hw_breakpoint_type(hbp);
	entry->addr	= hw_breakpoint_addr(hbp);
	strlcpy(entry->cmd, current->comm, TASK_COMM_LEN);

#ifdef CONFIG_PROFILE_KSYM_TRACER
	ksym_collect_stats(hw_breakpoint_addr(hbp));
#endif /* CONFIG_PROFILE_KSYM_TRACER */

	trace_buffer_unlock_commit(buffer, event, 0, pc);
}

/* Valid access types are represented as
 *
 * rw- : Set Read/Write Access Breakpoint
 * -w- : Set Write Access Breakpoint
 * --- : Clear Breakpoints
 * --x : Set Execution Break points (Not available yet)
 *
 */
static int ksym_trace_get_access_type(char *str)
{
	int access = 0;

	if (str[0] == 'r')
		access |= HW_BREAKPOINT_R;

	if (str[1] == 'w')
		access |= HW_BREAKPOINT_W;

	if (str[2] == 'x')
		access |= HW_BREAKPOINT_X;

	switch (access) {
	case HW_BREAKPOINT_R:
	case HW_BREAKPOINT_W:
	case HW_BREAKPOINT_W | HW_BREAKPOINT_R:
		return access;
	default:
		return -EINVAL;
	}
}

/*
 * There can be several possible malformed requests and we attempt to capture
 * all of them. We enumerate some of the rules
 * 1. We will not allow kernel symbols with ':' since it is used as a delimiter.
 *    i.e. multiple ':' symbols disallowed. Possible uses are of the form
 *    <module>:<ksym_name>:<op>.
 * 2. No delimiter symbol ':' in the input string
 * 3. Spurious operator symbols or symbols not in their respective positions
 * 4. <ksym_name>:--- i.e. clear breakpoint request when ksym_name not in file
 * 5. Kernel symbol not a part of /proc/kallsyms
 * 6. Duplicate requests
 */
static int parse_ksym_trace_str(char *input_string, char **ksymname,
							unsigned long *addr)
{
	int ret;

	*ksymname = strsep(&input_string, ":");
	*addr = kallsyms_lookup_name(*ksymname);

	/* Check for malformed request: (2), (1) and (5) */
	if ((!input_string) ||
	    (strlen(input_string) != KSYM_TRACER_OP_LEN) ||
	    (*addr == 0))
		return -EINVAL;;

	ret = ksym_trace_get_access_type(input_string);

	return ret;
}

int process_new_ksym_entry(char *ksymname, int op, unsigned long addr)
{
	struct trace_ksym *entry;
	int ret = -ENOMEM;

	if (ksym_filter_entry_count >= KSYM_TRACER_MAX) {
		printk(KERN_ERR "ksym_tracer: Maximum limit:(%d) reached. No"
		" new requests for tracing can be accepted now.\n",
			KSYM_TRACER_MAX);
		return -ENOSPC;
	}

	entry = kzalloc(sizeof(struct trace_ksym), GFP_KERNEL);
	if (!entry)
		return -ENOMEM;

	hw_breakpoint_init(&entry->attr);

	entry->attr.bp_type = op;
	entry->attr.bp_addr = addr;
	entry->attr.bp_len = HW_BREAKPOINT_LEN_4;

	ret = -EAGAIN;
	entry->ksym_hbp = register_wide_hw_breakpoint(&entry->attr,
					ksym_hbp_handler);

	if (IS_ERR(entry->ksym_hbp)) {
		ret = PTR_ERR(entry->ksym_hbp);
		printk(KERN_INFO "ksym_tracer request failed. Try again"
					" later!!\n");
		goto err;
	}

	hlist_add_head_rcu(&(entry->ksym_hlist), &ksym_filter_head);
	ksym_filter_entry_count++;

	return 0;

err:
	kfree(entry);

	return ret;
}

static ssize_t ksym_trace_filter_read(struct file *filp, char __user *ubuf,
						size_t count, loff_t *ppos)
{
	struct trace_ksym *entry;
	struct hlist_node *node;
	struct trace_seq *s;
	ssize_t cnt = 0;
	int ret;

	s = kmalloc(sizeof(*s), GFP_KERNEL);
	if (!s)
		return -ENOMEM;
	trace_seq_init(s);

	mutex_lock(&ksym_tracer_mutex);

	hlist_for_each_entry(entry, node, &ksym_filter_head, ksym_hlist) {
		ret = trace_seq_printf(s, "%pS:", (void *)entry->attr.bp_addr);
		if (entry->attr.bp_type == HW_BREAKPOINT_R)
			ret = trace_seq_puts(s, "r--\n");
		else if (entry->attr.bp_type == HW_BREAKPOINT_W)
			ret = trace_seq_puts(s, "-w-\n");
		else if (entry->attr.bp_type == (HW_BREAKPOINT_W | HW_BREAKPOINT_R))
			ret = trace_seq_puts(s, "rw-\n");
		WARN_ON_ONCE(!ret);
	}

	cnt = simple_read_from_buffer(ubuf, count, ppos, s->buffer, s->len);

	mutex_unlock(&ksym_tracer_mutex);

	kfree(s);

	return cnt;
}

static void __ksym_trace_reset(void)
{
	struct trace_ksym *entry;
	struct hlist_node *node, *node1;

	mutex_lock(&ksym_tracer_mutex);
	hlist_for_each_entry_safe(entry, node, node1, &ksym_filter_head,
								ksym_hlist) {
		unregister_wide_hw_breakpoint(entry->ksym_hbp);
		ksym_filter_entry_count--;
		hlist_del_rcu(&(entry->ksym_hlist));
		synchronize_rcu();
		kfree(entry);
	}
	mutex_unlock(&ksym_tracer_mutex);
}

static ssize_t ksym_trace_filter_write(struct file *file,
					const char __user *buffer,
						size_t count, loff_t *ppos)
{
	struct trace_ksym *entry;
	struct hlist_node *node;
	char *input_string, *ksymname = NULL;
	unsigned long ksym_addr = 0;
	int ret, op, changed = 0;

	input_string = kzalloc(count + 1, GFP_KERNEL);
	if (!input_string)
		return -ENOMEM;

	if (copy_from_user(input_string, buffer, count)) {
		kfree(input_string);
		return -EFAULT;
	}
	input_string[count] = '\0';

	strstrip(input_string);

	/*
	 * Clear all breakpoints if:
	 * 1: echo > ksym_trace_filter
	 * 2: echo 0 > ksym_trace_filter
	 * 3: echo "*:---" > ksym_trace_filter
	 */
	if (!input_string[0] || !strcmp(input_string, "0") ||
	    !strcmp(input_string, "*:---")) {
		__ksym_trace_reset();
		kfree(input_string);
		return count;
	}

	ret = op = parse_ksym_trace_str(input_string, &ksymname, &ksym_addr);
	if (ret < 0) {
		kfree(input_string);
		return ret;
	}

	mutex_lock(&ksym_tracer_mutex);

	ret = -EINVAL;
	hlist_for_each_entry(entry, node, &ksym_filter_head, ksym_hlist) {
		if (entry->attr.bp_addr == ksym_addr) {
			/* Check for malformed request: (6) */
			if (entry->attr.bp_type != op)
				changed = 1;
			else
				goto out;
			break;
		}
	}
	if (changed) {
		unregister_wide_hw_breakpoint(entry->ksym_hbp);
		entry->attr.bp_type = op;
		ret = 0;
		if (op > 0) {
			entry->ksym_hbp =
				register_wide_hw_breakpoint(&entry->attr,
					ksym_hbp_handler);
			if (IS_ERR(entry->ksym_hbp))
				ret = PTR_ERR(entry->ksym_hbp);
			else
				goto out;
		}
		/* Error or "symbol:---" case: drop it */
		ksym_filter_entry_count--;
		hlist_del_rcu(&(entry->ksym_hlist));
		synchronize_rcu();
		kfree(entry);
		goto out;
	} else {
		/* Check for malformed request: (4) */
		if (op == 0)
			goto out;
		ret = process_new_ksym_entry(ksymname, op, ksym_addr);
	}
out:
	mutex_unlock(&ksym_tracer_mutex);

	kfree(input_string);

	if (!ret)
		ret = count;
	return ret;
}

static const struct file_operations ksym_tracing_fops = {
	.open		= tracing_open_generic,
	.read		= ksym_trace_filter_read,
	.write		= ksym_trace_filter_write,
};

static void ksym_trace_reset(struct trace_array *tr)
{
	ksym_tracing_enabled = 0;
	__ksym_trace_reset();
}

static int ksym_trace_init(struct trace_array *tr)
{
	int cpu, ret = 0;

	for_each_online_cpu(cpu)
		tracing_reset(tr, cpu);
	ksym_tracing_enabled = 1;
	ksym_trace_array = tr;

	return ret;
}

static void ksym_trace_print_header(struct seq_file *m)
{
	seq_puts(m,
		 "#       TASK-PID   CPU#      Symbol                    "
		 "Type    Function\n");
	seq_puts(m,
		 "#          |        |          |                       "
		 " |         |\n");
}

static enum print_line_t ksym_trace_output(struct trace_iterator *iter)
{
	struct trace_entry *entry = iter->ent;
	struct trace_seq *s = &iter->seq;
	struct ksym_trace_entry *field;
	char str[KSYM_SYMBOL_LEN];
	int ret;

	if (entry->type != TRACE_KSYM)
		return TRACE_TYPE_UNHANDLED;

	trace_assign_type(field, entry);

	ret = trace_seq_printf(s, "%11s-%-5d [%03d] %pS", field->cmd,
				entry->pid, iter->cpu, (char *)field->addr);
	if (!ret)
		return TRACE_TYPE_PARTIAL_LINE;

	switch (field->type) {
	case HW_BREAKPOINT_R:
		ret = trace_seq_printf(s, " R  ");
		break;
	case HW_BREAKPOINT_W:
		ret = trace_seq_printf(s, " W  ");
		break;
	case HW_BREAKPOINT_R | HW_BREAKPOINT_W:
		ret = trace_seq_printf(s, " RW ");
		break;
	default:
		return TRACE_TYPE_PARTIAL_LINE;
	}

	if (!ret)
		return TRACE_TYPE_PARTIAL_LINE;

	sprint_symbol(str, field->ip);
	ret = trace_seq_printf(s, "%s\n", str);
	if (!ret)
		return TRACE_TYPE_PARTIAL_LINE;

	return TRACE_TYPE_HANDLED;
}

struct tracer ksym_tracer __read_mostly =
{
	.name		= "ksym_tracer",
	.init		= ksym_trace_init,
	.reset		= ksym_trace_reset,
#ifdef CONFIG_FTRACE_SELFTEST
	.selftest	= trace_selftest_startup_ksym,
#endif
	.print_header   = ksym_trace_print_header,
	.print_line	= ksym_trace_output
};

__init static int init_ksym_trace(void)
{
	struct dentry *d_tracer;
	struct dentry *entry;

	d_tracer = tracing_init_dentry();
	ksym_filter_entry_count = 0;

	entry = debugfs_create_file("ksym_trace_filter", 0644, d_tracer,
				    NULL, &ksym_tracing_fops);
	if (!entry)
		pr_warning("Could not create debugfs "
			   "'ksym_trace_filter' file\n");

	return register_tracer(&ksym_tracer);
}
device_initcall(init_ksym_trace);


#ifdef CONFIG_PROFILE_KSYM_TRACER
static int ksym_tracer_stat_headers(struct seq_file *m)
{
	seq_puts(m, "  Access Type ");
	seq_puts(m, "  Symbol                                       Counter\n");
	seq_puts(m, "  ----------- ");
	seq_puts(m, "  ------                                       -------\n");
	return 0;
}

static int ksym_tracer_stat_show(struct seq_file *m, void *v)
{
	struct hlist_node *stat = v;
	struct trace_ksym *entry;
	int access_type = 0;
	char fn_name[KSYM_NAME_LEN];

	entry = hlist_entry(stat, struct trace_ksym, ksym_hlist);

	access_type = entry->attr.bp_type;

	switch (access_type) {
	case HW_BREAKPOINT_R:
		seq_puts(m, "  R           ");
		break;
	case HW_BREAKPOINT_W:
		seq_puts(m, "  W           ");
		break;
	case HW_BREAKPOINT_R | HW_BREAKPOINT_W:
		seq_puts(m, "  RW          ");
		break;
	default:
		seq_puts(m, "  NA          ");
	}

	if (lookup_symbol_name(entry->attr.bp_addr, fn_name) >= 0)
		seq_printf(m, "  %-36s", fn_name);
	else
		seq_printf(m, "  %-36s", "<NA>");
	seq_printf(m, " %15lu\n", entry->counter);

	return 0;
}

static void *ksym_tracer_stat_start(struct tracer_stat *trace)
{
	return ksym_filter_head.first;
}

static void *
ksym_tracer_stat_next(void *v, int idx)
{
	struct hlist_node *stat = v;

	return stat->next;
}

static struct tracer_stat ksym_tracer_stats = {
	.name = "ksym_tracer",
	.stat_start = ksym_tracer_stat_start,
	.stat_next = ksym_tracer_stat_next,
	.stat_headers = ksym_tracer_stat_headers,
	.stat_show = ksym_tracer_stat_show
};

__init static int ksym_tracer_stat_init(void)
{
	int ret;

	ret = register_stat_tracer(&ksym_tracer_stats);
	if (ret) {
		printk(KERN_WARNING "Warning: could not register "
				    "ksym tracer stats\n");
		return 1;
	}

	return 0;
}
fs_initcall(ksym_tracer_stat_init);
#endif /* CONFIG_PROFILE_KSYM_TRACER */