summaryrefslogtreecommitdiff
path: root/kernel/trace/trace_probe.c
blob: 8f8411e7835fdc0e138924c8ab5c35683894774e (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
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
// SPDX-License-Identifier: GPL-2.0
/*
 * Common code for probe-based Dynamic events.
 *
 * This code was copied from kernel/trace/trace_kprobe.c written by
 * Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
 *
 * Updates to make this generic:
 * Copyright (C) IBM Corporation, 2010-2011
 * Author:     Srikar Dronamraju
 */
#define pr_fmt(fmt)	"trace_probe: " fmt

#include "trace_probe.h"

static const char *reserved_field_names[] = {
	"common_type",
	"common_flags",
	"common_preempt_count",
	"common_pid",
	"common_tgid",
	FIELD_STRING_IP,
	FIELD_STRING_RETIP,
	FIELD_STRING_FUNC,
};

/* Printing  in basic type function template */
#define DEFINE_BASIC_PRINT_TYPE_FUNC(tname, type, fmt)			\
int PRINT_TYPE_FUNC_NAME(tname)(struct trace_seq *s, void *data, void *ent)\
{									\
	trace_seq_printf(s, fmt, *(type *)data);			\
	return !trace_seq_has_overflowed(s);				\
}									\
const char PRINT_TYPE_FMT_NAME(tname)[] = fmt;

DEFINE_BASIC_PRINT_TYPE_FUNC(u8,  u8,  "%u")
DEFINE_BASIC_PRINT_TYPE_FUNC(u16, u16, "%u")
DEFINE_BASIC_PRINT_TYPE_FUNC(u32, u32, "%u")
DEFINE_BASIC_PRINT_TYPE_FUNC(u64, u64, "%Lu")
DEFINE_BASIC_PRINT_TYPE_FUNC(s8,  s8,  "%d")
DEFINE_BASIC_PRINT_TYPE_FUNC(s16, s16, "%d")
DEFINE_BASIC_PRINT_TYPE_FUNC(s32, s32, "%d")
DEFINE_BASIC_PRINT_TYPE_FUNC(s64, s64, "%Ld")
DEFINE_BASIC_PRINT_TYPE_FUNC(x8,  u8,  "0x%x")
DEFINE_BASIC_PRINT_TYPE_FUNC(x16, u16, "0x%x")
DEFINE_BASIC_PRINT_TYPE_FUNC(x32, u32, "0x%x")
DEFINE_BASIC_PRINT_TYPE_FUNC(x64, u64, "0x%Lx")

int PRINT_TYPE_FUNC_NAME(symbol)(struct trace_seq *s, void *data, void *ent)
{
	trace_seq_printf(s, "%pS", (void *)*(unsigned long *)data);
	return !trace_seq_has_overflowed(s);
}
const char PRINT_TYPE_FMT_NAME(symbol)[] = "%pS";

/* Print type function for string type */
int PRINT_TYPE_FUNC_NAME(string)(struct trace_seq *s, void *data, void *ent)
{
	int len = *(u32 *)data >> 16;

	if (!len)
		trace_seq_puts(s, "(fault)");
	else
		trace_seq_printf(s, "\"%s\"",
				 (const char *)get_loc_data(data, ent));
	return !trace_seq_has_overflowed(s);
}

const char PRINT_TYPE_FMT_NAME(string)[] = "\\\"%s\\\"";

/* Fetch type information table */
static const struct fetch_type probe_fetch_types[] = {
	/* Special types */
	__ASSIGN_FETCH_TYPE("string", string, string, sizeof(u32), 1,
			    "__data_loc char[]"),
	/* Basic types */
	ASSIGN_FETCH_TYPE(u8,  u8,  0),
	ASSIGN_FETCH_TYPE(u16, u16, 0),
	ASSIGN_FETCH_TYPE(u32, u32, 0),
	ASSIGN_FETCH_TYPE(u64, u64, 0),
	ASSIGN_FETCH_TYPE(s8,  u8,  1),
	ASSIGN_FETCH_TYPE(s16, u16, 1),
	ASSIGN_FETCH_TYPE(s32, u32, 1),
	ASSIGN_FETCH_TYPE(s64, u64, 1),
	ASSIGN_FETCH_TYPE_ALIAS(x8,  u8,  u8,  0),
	ASSIGN_FETCH_TYPE_ALIAS(x16, u16, u16, 0),
	ASSIGN_FETCH_TYPE_ALIAS(x32, u32, u32, 0),
	ASSIGN_FETCH_TYPE_ALIAS(x64, u64, u64, 0),
	ASSIGN_FETCH_TYPE_ALIAS(symbol, ADDR_FETCH_TYPE, ADDR_FETCH_TYPE, 0),

	ASSIGN_FETCH_TYPE_END
};

static const struct fetch_type *find_fetch_type(const char *type)
{
	int i;

	if (!type)
		type = DEFAULT_FETCH_TYPE_STR;

	/* Special case: bitfield */
	if (*type == 'b') {
		unsigned long bs;

		type = strchr(type, '/');
		if (!type)
			goto fail;

		type++;
		if (kstrtoul(type, 0, &bs))
			goto fail;

		switch (bs) {
		case 8:
			return find_fetch_type("u8");
		case 16:
			return find_fetch_type("u16");
		case 32:
			return find_fetch_type("u32");
		case 64:
			return find_fetch_type("u64");
		default:
			goto fail;
		}
	}

	for (i = 0; probe_fetch_types[i].name; i++) {
		if (strcmp(type, probe_fetch_types[i].name) == 0)
			return &probe_fetch_types[i];
	}

fail:
	return NULL;
}

/* Split symbol and offset. */
int traceprobe_split_symbol_offset(char *symbol, long *offset)
{
	char *tmp;
	int ret;

	if (!offset)
		return -EINVAL;

	tmp = strpbrk(symbol, "+-");
	if (tmp) {
		ret = kstrtol(tmp, 0, offset);
		if (ret)
			return ret;
		*tmp = '\0';
	} else
		*offset = 0;

	return 0;
}

/* @buf must has MAX_EVENT_NAME_LEN size */
int traceprobe_parse_event_name(const char **pevent, const char **pgroup,
				char *buf)
{
	const char *slash, *event = *pevent;
	int len;

	slash = strchr(event, '/');
	if (slash) {
		if (slash == event) {
			pr_info("Group name is not specified\n");
			return -EINVAL;
		}
		if (slash - event + 1 > MAX_EVENT_NAME_LEN) {
			pr_info("Group name is too long\n");
			return -E2BIG;
		}
		strlcpy(buf, event, slash - event + 1);
		if (!is_good_name(buf)) {
			pr_info("Group name must follow the same rules as C identifiers\n");
			return -EINVAL;
		}
		*pgroup = buf;
		*pevent = slash + 1;
		event = *pevent;
	}
	len = strlen(event);
	if (len == 0) {
		pr_info("Event name is not specified\n");
		return -EINVAL;
	} else if (len > MAX_EVENT_NAME_LEN) {
		pr_info("Event name is too long\n");
		return -E2BIG;
	}
	if (!is_good_name(event)) {
		pr_info("Event name must follow the same rules as C identifiers\n");
		return -EINVAL;
	}
	return 0;
}

#define PARAM_MAX_STACK (THREAD_SIZE / sizeof(unsigned long))

static int parse_probe_vars(char *arg, const struct fetch_type *t,
			    struct fetch_insn *code, unsigned int flags)
{
	unsigned long param;
	int ret = 0;
	int len;

	if (strcmp(arg, "retval") == 0) {
		if (flags & TPARG_FL_RETURN)
			code->op = FETCH_OP_RETVAL;
		else
			ret = -EINVAL;
	} else if ((len = str_has_prefix(arg, "stack"))) {
		if (arg[len] == '\0') {
			code->op = FETCH_OP_STACKP;
		} else if (isdigit(arg[len])) {
			ret = kstrtoul(arg + len, 10, &param);
			if (ret || ((flags & TPARG_FL_KERNEL) &&
				    param > PARAM_MAX_STACK))
				ret = -EINVAL;
			else {
				code->op = FETCH_OP_STACK;
				code->param = (unsigned int)param;
			}
		} else
			ret = -EINVAL;
	} else if (strcmp(arg, "comm") == 0) {
		code->op = FETCH_OP_COMM;
#ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API
	} else if (((flags & TPARG_FL_MASK) ==
		    (TPARG_FL_KERNEL | TPARG_FL_FENTRY)) &&
		   (len = str_has_prefix(arg, "arg"))) {
		if (!isdigit(arg[len]))
			return -EINVAL;
		ret = kstrtoul(arg + len, 10, &param);
		if (ret || !param || param > PARAM_MAX_STACK)
			return -EINVAL;
		code->op = FETCH_OP_ARG;
		code->param = (unsigned int)param - 1;
#endif
	} else
		ret = -EINVAL;

	return ret;
}

/* Recursive argument parser */
static int
parse_probe_arg(char *arg, const struct fetch_type *type,
		struct fetch_insn **pcode, struct fetch_insn *end,
		unsigned int flags)
{
	struct fetch_insn *code = *pcode;
	unsigned long param;
	long offset = 0;
	char *tmp;
	int ret = 0;

	switch (arg[0]) {
	case '$':
		ret = parse_probe_vars(arg + 1, type, code, flags);
		break;

	case '%':	/* named register */
		ret = regs_query_register_offset(arg + 1);
		if (ret >= 0) {
			code->op = FETCH_OP_REG;
			code->param = (unsigned int)ret;
			ret = 0;
		}
		break;

	case '@':	/* memory, file-offset or symbol */
		if (isdigit(arg[1])) {
			ret = kstrtoul(arg + 1, 0, &param);
			if (ret)
				break;
			/* load address */
			code->op = FETCH_OP_IMM;
			code->immediate = param;
		} else if (arg[1] == '+') {
			/* kprobes don't support file offsets */
			if (flags & TPARG_FL_KERNEL)
				return -EINVAL;

			ret = kstrtol(arg + 2, 0, &offset);
			if (ret)
				break;

			code->op = FETCH_OP_FOFFS;
			code->immediate = (unsigned long)offset;  // imm64?
		} else {
			/* uprobes don't support symbols */
			if (!(flags & TPARG_FL_KERNEL))
				return -EINVAL;

			/* Preserve symbol for updating */
			code->op = FETCH_NOP_SYMBOL;
			code->data = kstrdup(arg + 1, GFP_KERNEL);
			if (!code->data)
				return -ENOMEM;
			if (++code == end)
				return -E2BIG;

			code->op = FETCH_OP_IMM;
			code->immediate = 0;
		}
		/* These are fetching from memory */
		if (++code == end)
			return -E2BIG;
		*pcode = code;
		code->op = FETCH_OP_DEREF;
		code->offset = offset;
		break;

	case '+':	/* deref memory */
		arg++;	/* Skip '+', because kstrtol() rejects it. */
		/* fall through */
	case '-':
		tmp = strchr(arg, '(');
		if (!tmp)
			return -EINVAL;

		*tmp = '\0';
		ret = kstrtol(arg, 0, &offset);
		if (ret)
			break;

		arg = tmp + 1;
		tmp = strrchr(arg, ')');

		if (tmp) {
			const struct fetch_type *t2 = find_fetch_type(NULL);

			*tmp = '\0';
			ret = parse_probe_arg(arg, t2, &code, end, flags);
			if (ret)
				break;
			if (code->op == FETCH_OP_COMM)
				return -EINVAL;
			if (++code == end)
				return -E2BIG;
			*pcode = code;

			code->op = FETCH_OP_DEREF;
			code->offset = offset;
		}
		break;
	}
	if (!ret && code->op == FETCH_OP_NOP) {
		/* Parsed, but do not find fetch method */
		ret = -EINVAL;
	}
	return ret;
}

#define BYTES_TO_BITS(nb)	((BITS_PER_LONG * (nb)) / sizeof(long))

/* Bitfield type needs to be parsed into a fetch function */
static int __parse_bitfield_probe_arg(const char *bf,
				      const struct fetch_type *t,
				      struct fetch_insn **pcode)
{
	struct fetch_insn *code = *pcode;
	unsigned long bw, bo;
	char *tail;

	if (*bf != 'b')
		return 0;

	bw = simple_strtoul(bf + 1, &tail, 0);	/* Use simple one */

	if (bw == 0 || *tail != '@')
		return -EINVAL;

	bf = tail + 1;
	bo = simple_strtoul(bf, &tail, 0);

	if (tail == bf || *tail != '/')
		return -EINVAL;
	code++;
	if (code->op != FETCH_OP_NOP)
		return -E2BIG;
	*pcode = code;

	code->op = FETCH_OP_MOD_BF;
	code->lshift = BYTES_TO_BITS(t->size) - (bw + bo);
	code->rshift = BYTES_TO_BITS(t->size) - bw;
	code->basesize = t->size;

	return (BYTES_TO_BITS(t->size) < (bw + bo)) ? -EINVAL : 0;
}

/* String length checking wrapper */
static int traceprobe_parse_probe_arg_body(char *arg, ssize_t *size,
		struct probe_arg *parg, unsigned int flags)
{
	struct fetch_insn *code, *scode, *tmp = NULL;
	char *t, *t2;
	int ret, len;

	if (strlen(arg) > MAX_ARGSTR_LEN) {
		pr_info("Argument is too long.: %s\n",  arg);
		return -ENOSPC;
	}
	parg->comm = kstrdup(arg, GFP_KERNEL);
	if (!parg->comm) {
		pr_info("Failed to allocate memory for command '%s'.\n", arg);
		return -ENOMEM;
	}
	t = strchr(arg, ':');
	if (t) {
		*t = '\0';
		t2 = strchr(++t, '[');
		if (t2) {
			*t2 = '\0';
			parg->count = simple_strtoul(t2 + 1, &t2, 0);
			if (strcmp(t2, "]") || parg->count == 0)
				return -EINVAL;
			if (parg->count > MAX_ARRAY_LEN)
				return -E2BIG;
		}
	}
	/*
	 * The default type of $comm should be "string", and it can't be
	 * dereferenced.
	 */
	if (!t && strcmp(arg, "$comm") == 0)
		parg->type = find_fetch_type("string");
	else
		parg->type = find_fetch_type(t);
	if (!parg->type) {
		pr_info("Unsupported type: %s\n", t);
		return -EINVAL;
	}
	parg->offset = *size;
	*size += parg->type->size * (parg->count ?: 1);

	if (parg->count) {
		len = strlen(parg->type->fmttype) + 6;
		parg->fmt = kmalloc(len, GFP_KERNEL);
		if (!parg->fmt)
			return -ENOMEM;
		snprintf(parg->fmt, len, "%s[%d]", parg->type->fmttype,
			 parg->count);
	}

	code = tmp = kzalloc(sizeof(*code) * FETCH_INSN_MAX, GFP_KERNEL);
	if (!code)
		return -ENOMEM;
	code[FETCH_INSN_MAX - 1].op = FETCH_OP_END;

	ret = parse_probe_arg(arg, parg->type, &code, &code[FETCH_INSN_MAX - 1],
			      flags);
	if (ret)
		goto fail;

	/* Store operation */
	if (!strcmp(parg->type->name, "string")) {
		if (code->op != FETCH_OP_DEREF && code->op != FETCH_OP_IMM &&
		    code->op != FETCH_OP_COMM) {
			pr_info("string only accepts memory or address.\n");
			ret = -EINVAL;
			goto fail;
		}
		if (code->op != FETCH_OP_DEREF || parg->count) {
			/*
			 * IMM and COMM is pointing actual address, those must
			 * be kept, and if parg->count != 0, this is an array
			 * of string pointers instead of string address itself.
			 */
			code++;
			if (code->op != FETCH_OP_NOP) {
				ret = -E2BIG;
				goto fail;
			}
		}
		code->op = FETCH_OP_ST_STRING;	/* In DEREF case, replace it */
		code->size = parg->type->size;
		parg->dynamic = true;
	} else if (code->op == FETCH_OP_DEREF) {
		code->op = FETCH_OP_ST_MEM;
		code->size = parg->type->size;
	} else {
		code++;
		if (code->op != FETCH_OP_NOP) {
			ret = -E2BIG;
			goto fail;
		}
		code->op = FETCH_OP_ST_RAW;
		code->size = parg->type->size;
	}
	scode = code;
	/* Modify operation */
	if (t != NULL) {
		ret = __parse_bitfield_probe_arg(t, parg->type, &code);
		if (ret)
			goto fail;
	}
	/* Loop(Array) operation */
	if (parg->count) {
		if (scode->op != FETCH_OP_ST_MEM &&
		    scode->op != FETCH_OP_ST_STRING) {
			pr_info("array only accepts memory or address\n");
			ret = -EINVAL;
			goto fail;
		}
		code++;
		if (code->op != FETCH_OP_NOP) {
			ret = -E2BIG;
			goto fail;
		}
		code->op = FETCH_OP_LP_ARRAY;
		code->param = parg->count;
	}
	code++;
	code->op = FETCH_OP_END;

	/* Shrink down the code buffer */
	parg->code = kzalloc(sizeof(*code) * (code - tmp + 1), GFP_KERNEL);
	if (!parg->code)
		ret = -ENOMEM;
	else
		memcpy(parg->code, tmp, sizeof(*code) * (code - tmp + 1));

fail:
	if (ret) {
		for (code = tmp; code < tmp + FETCH_INSN_MAX; code++)
			if (code->op == FETCH_NOP_SYMBOL)
				kfree(code->data);
	}
	kfree(tmp);

	return ret;
}

/* Return 1 if name is reserved or already used by another argument */
static int traceprobe_conflict_field_name(const char *name,
					  struct probe_arg *args, int narg)
{
	int i;

	for (i = 0; i < ARRAY_SIZE(reserved_field_names); i++)
		if (strcmp(reserved_field_names[i], name) == 0)
			return 1;

	for (i = 0; i < narg; i++)
		if (strcmp(args[i].name, name) == 0)
			return 1;

	return 0;
}

int traceprobe_parse_probe_arg(struct trace_probe *tp, int i, char *arg,
				unsigned int flags)
{
	struct probe_arg *parg = &tp->args[i];
	char *body;
	int ret;

	/* Increment count for freeing args in error case */
	tp->nr_args++;

	body = strchr(arg, '=');
	if (body) {
		if (body - arg > MAX_ARG_NAME_LEN || body == arg)
			return -EINVAL;
		parg->name = kmemdup_nul(arg, body - arg, GFP_KERNEL);
		body++;
	} else {
		/* If argument name is omitted, set "argN" */
		parg->name = kasprintf(GFP_KERNEL, "arg%d", i + 1);
		body = arg;
	}
	if (!parg->name)
		return -ENOMEM;

	if (!is_good_name(parg->name)) {
		pr_info("Invalid argument[%d] name: %s\n",
			i, parg->name);
		return -EINVAL;
	}

	if (traceprobe_conflict_field_name(parg->name, tp->args, i)) {
		pr_info("Argument[%d]: '%s' conflicts with another field.\n",
			i, parg->name);
		return -EINVAL;
	}

	/* Parse fetch argument */
	ret = traceprobe_parse_probe_arg_body(body, &tp->size, parg, flags);
	if (ret)
		pr_info("Parse error at argument[%d]. (%d)\n", i, ret);
	return ret;
}

void traceprobe_free_probe_arg(struct probe_arg *arg)
{
	struct fetch_insn *code = arg->code;

	while (code && code->op != FETCH_OP_END) {
		if (code->op == FETCH_NOP_SYMBOL)
			kfree(code->data);
		code++;
	}
	kfree(arg->code);
	kfree(arg->name);
	kfree(arg->comm);
	kfree(arg->fmt);
}

int traceprobe_update_arg(struct probe_arg *arg)
{
	struct fetch_insn *code = arg->code;
	long offset;
	char *tmp;
	char c;
	int ret = 0;

	while (code && code->op != FETCH_OP_END) {
		if (code->op == FETCH_NOP_SYMBOL) {
			if (code[1].op != FETCH_OP_IMM)
				return -EINVAL;

			tmp = strpbrk(code->data, "+-");
			if (tmp)
				c = *tmp;
			ret = traceprobe_split_symbol_offset(code->data,
							     &offset);
			if (ret)
				return ret;

			code[1].immediate =
				(unsigned long)kallsyms_lookup_name(code->data);
			if (tmp)
				*tmp = c;
			if (!code[1].immediate)
				return -ENOENT;
			code[1].immediate += offset;
		}
		code++;
	}
	return 0;
}

/* When len=0, we just calculate the needed length */
#define LEN_OR_ZERO (len ? len - pos : 0)
static int __set_print_fmt(struct trace_probe *tp, char *buf, int len,
			   bool is_return)
{
	struct probe_arg *parg;
	int i, j;
	int pos = 0;
	const char *fmt, *arg;

	if (!is_return) {
		fmt = "(%lx)";
		arg = "REC->" FIELD_STRING_IP;
	} else {
		fmt = "(%lx <- %lx)";
		arg = "REC->" FIELD_STRING_FUNC ", REC->" FIELD_STRING_RETIP;
	}

	pos += snprintf(buf + pos, LEN_OR_ZERO, "\"%s", fmt);

	for (i = 0; i < tp->nr_args; i++) {
		parg = tp->args + i;
		pos += snprintf(buf + pos, LEN_OR_ZERO, " %s=", parg->name);
		if (parg->count) {
			pos += snprintf(buf + pos, LEN_OR_ZERO, "{%s",
					parg->type->fmt);
			for (j = 1; j < parg->count; j++)
				pos += snprintf(buf + pos, LEN_OR_ZERO, ",%s",
						parg->type->fmt);
			pos += snprintf(buf + pos, LEN_OR_ZERO, "}");
		} else
			pos += snprintf(buf + pos, LEN_OR_ZERO, "%s",
					parg->type->fmt);
	}

	pos += snprintf(buf + pos, LEN_OR_ZERO, "\", %s", arg);

	for (i = 0; i < tp->nr_args; i++) {
		parg = tp->args + i;
		if (parg->count) {
			if (strcmp(parg->type->name, "string") == 0)
				fmt = ", __get_str(%s[%d])";
			else
				fmt = ", REC->%s[%d]";
			for (j = 0; j < parg->count; j++)
				pos += snprintf(buf + pos, LEN_OR_ZERO,
						fmt, parg->name, j);
		} else {
			if (strcmp(parg->type->name, "string") == 0)
				fmt = ", __get_str(%s)";
			else
				fmt = ", REC->%s";
			pos += snprintf(buf + pos, LEN_OR_ZERO,
					fmt, parg->name);
		}
	}

	/* return the length of print_fmt */
	return pos;
}
#undef LEN_OR_ZERO

int traceprobe_set_print_fmt(struct trace_probe *tp, bool is_return)
{
	int len;
	char *print_fmt;

	/* First: called with 0 length to calculate the needed length */
	len = __set_print_fmt(tp, NULL, 0, is_return);
	print_fmt = kmalloc(len + 1, GFP_KERNEL);
	if (!print_fmt)
		return -ENOMEM;

	/* Second: actually write the @print_fmt */
	__set_print_fmt(tp, print_fmt, len + 1, is_return);
	tp->call.print_fmt = print_fmt;

	return 0;
}

int traceprobe_define_arg_fields(struct trace_event_call *event_call,
				 size_t offset, struct trace_probe *tp)
{
	int ret, i;

	/* Set argument names as fields */
	for (i = 0; i < tp->nr_args; i++) {
		struct probe_arg *parg = &tp->args[i];
		const char *fmt = parg->type->fmttype;
		int size = parg->type->size;

		if (parg->fmt)
			fmt = parg->fmt;
		if (parg->count)
			size *= parg->count;
		ret = trace_define_field(event_call, fmt, parg->name,
					 offset + parg->offset, size,
					 parg->type->is_signed,
					 FILTER_OTHER);
		if (ret)
			return ret;
	}
	return 0;
}