1/*
2 * Common code for probe-based Dynamic events.
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License version 2 as
6 * published by the Free Software Foundation.
7 *
8 * This program is distributed in the hope that it will be useful,
9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
11 * GNU General Public License for more details.
12 *
13 * You should have received a copy of the GNU General Public License
14 * along with this program; if not, write to the Free Software
15 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
16 *
17 * This code was copied from kernel/trace/trace_kprobe.c written by
18 * Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
19 *
20 * Updates to make this generic:
21 * Copyright (C) IBM Corporation, 2010-2011
22 * Author:     Srikar Dronamraju
23 */
24
25#include "trace_probe.h"
26
27const char *reserved_field_names[] = {
28	"common_type",
29	"common_flags",
30	"common_preempt_count",
31	"common_pid",
32	"common_tgid",
33	FIELD_STRING_IP,
34	FIELD_STRING_RETIP,
35	FIELD_STRING_FUNC,
36};
37
38/* Printing  in basic type function template */
39#define DEFINE_BASIC_PRINT_TYPE_FUNC(type, fmt)				\
40int PRINT_TYPE_FUNC_NAME(type)(struct trace_seq *s, const char *name,	\
41				void *data, void *ent)			\
42{									\
43	trace_seq_printf(s, " %s=" fmt, name, *(type *)data);		\
44	return !trace_seq_has_overflowed(s);				\
45}									\
46const char PRINT_TYPE_FMT_NAME(type)[] = fmt;				\
47NOKPROBE_SYMBOL(PRINT_TYPE_FUNC_NAME(type));
48
49DEFINE_BASIC_PRINT_TYPE_FUNC(u8 , "0x%x")
50DEFINE_BASIC_PRINT_TYPE_FUNC(u16, "0x%x")
51DEFINE_BASIC_PRINT_TYPE_FUNC(u32, "0x%x")
52DEFINE_BASIC_PRINT_TYPE_FUNC(u64, "0x%Lx")
53DEFINE_BASIC_PRINT_TYPE_FUNC(s8,  "%d")
54DEFINE_BASIC_PRINT_TYPE_FUNC(s16, "%d")
55DEFINE_BASIC_PRINT_TYPE_FUNC(s32, "%d")
56DEFINE_BASIC_PRINT_TYPE_FUNC(s64, "%Ld")
57
58/* Print type function for string type */
59int PRINT_TYPE_FUNC_NAME(string)(struct trace_seq *s, const char *name,
60				 void *data, void *ent)
61{
62	int len = *(u32 *)data >> 16;
63
64	if (!len)
65		trace_seq_printf(s, " %s=(fault)", name);
66	else
67		trace_seq_printf(s, " %s=\"%s\"", name,
68				 (const char *)get_loc_data(data, ent));
69	return !trace_seq_has_overflowed(s);
70}
71NOKPROBE_SYMBOL(PRINT_TYPE_FUNC_NAME(string));
72
73const char PRINT_TYPE_FMT_NAME(string)[] = "\\\"%s\\\"";
74
75#define CHECK_FETCH_FUNCS(method, fn)			\
76	(((FETCH_FUNC_NAME(method, u8) == fn) ||	\
77	  (FETCH_FUNC_NAME(method, u16) == fn) ||	\
78	  (FETCH_FUNC_NAME(method, u32) == fn) ||	\
79	  (FETCH_FUNC_NAME(method, u64) == fn) ||	\
80	  (FETCH_FUNC_NAME(method, string) == fn) ||	\
81	  (FETCH_FUNC_NAME(method, string_size) == fn)) \
82	 && (fn != NULL))
83
84/* Data fetch function templates */
85#define DEFINE_FETCH_reg(type)						\
86void FETCH_FUNC_NAME(reg, type)(struct pt_regs *regs, void *offset, void *dest)	\
87{									\
88	*(type *)dest = (type)regs_get_register(regs,			\
89				(unsigned int)((unsigned long)offset));	\
90}									\
91NOKPROBE_SYMBOL(FETCH_FUNC_NAME(reg, type));
92DEFINE_BASIC_FETCH_FUNCS(reg)
93/* No string on the register */
94#define fetch_reg_string	NULL
95#define fetch_reg_string_size	NULL
96
97#define DEFINE_FETCH_retval(type)					\
98void FETCH_FUNC_NAME(retval, type)(struct pt_regs *regs,		\
99				   void *dummy, void *dest)		\
100{									\
101	*(type *)dest = (type)regs_return_value(regs);			\
102}									\
103NOKPROBE_SYMBOL(FETCH_FUNC_NAME(retval, type));
104DEFINE_BASIC_FETCH_FUNCS(retval)
105/* No string on the retval */
106#define fetch_retval_string		NULL
107#define fetch_retval_string_size	NULL
108
109/* Dereference memory access function */
110struct deref_fetch_param {
111	struct fetch_param	orig;
112	long			offset;
113	fetch_func_t		fetch;
114	fetch_func_t		fetch_size;
115};
116
117#define DEFINE_FETCH_deref(type)					\
118void FETCH_FUNC_NAME(deref, type)(struct pt_regs *regs,			\
119				  void *data, void *dest)		\
120{									\
121	struct deref_fetch_param *dprm = data;				\
122	unsigned long addr;						\
123	call_fetch(&dprm->orig, regs, &addr);				\
124	if (addr) {							\
125		addr += dprm->offset;					\
126		dprm->fetch(regs, (void *)addr, dest);			\
127	} else								\
128		*(type *)dest = 0;					\
129}									\
130NOKPROBE_SYMBOL(FETCH_FUNC_NAME(deref, type));
131DEFINE_BASIC_FETCH_FUNCS(deref)
132DEFINE_FETCH_deref(string)
133
134void FETCH_FUNC_NAME(deref, string_size)(struct pt_regs *regs,
135					 void *data, void *dest)
136{
137	struct deref_fetch_param *dprm = data;
138	unsigned long addr;
139
140	call_fetch(&dprm->orig, regs, &addr);
141	if (addr && dprm->fetch_size) {
142		addr += dprm->offset;
143		dprm->fetch_size(regs, (void *)addr, dest);
144	} else
145		*(string_size *)dest = 0;
146}
147NOKPROBE_SYMBOL(FETCH_FUNC_NAME(deref, string_size));
148
149static void update_deref_fetch_param(struct deref_fetch_param *data)
150{
151	if (CHECK_FETCH_FUNCS(deref, data->orig.fn))
152		update_deref_fetch_param(data->orig.data);
153	else if (CHECK_FETCH_FUNCS(symbol, data->orig.fn))
154		update_symbol_cache(data->orig.data);
155}
156NOKPROBE_SYMBOL(update_deref_fetch_param);
157
158static void free_deref_fetch_param(struct deref_fetch_param *data)
159{
160	if (CHECK_FETCH_FUNCS(deref, data->orig.fn))
161		free_deref_fetch_param(data->orig.data);
162	else if (CHECK_FETCH_FUNCS(symbol, data->orig.fn))
163		free_symbol_cache(data->orig.data);
164	kfree(data);
165}
166NOKPROBE_SYMBOL(free_deref_fetch_param);
167
168/* Bitfield fetch function */
169struct bitfield_fetch_param {
170	struct fetch_param	orig;
171	unsigned char		hi_shift;
172	unsigned char		low_shift;
173};
174
175#define DEFINE_FETCH_bitfield(type)					\
176void FETCH_FUNC_NAME(bitfield, type)(struct pt_regs *regs,		\
177				     void *data, void *dest)		\
178{									\
179	struct bitfield_fetch_param *bprm = data;			\
180	type buf = 0;							\
181	call_fetch(&bprm->orig, regs, &buf);				\
182	if (buf) {							\
183		buf <<= bprm->hi_shift;					\
184		buf >>= bprm->low_shift;				\
185	}								\
186	*(type *)dest = buf;						\
187}									\
188NOKPROBE_SYMBOL(FETCH_FUNC_NAME(bitfield, type));
189DEFINE_BASIC_FETCH_FUNCS(bitfield)
190#define fetch_bitfield_string		NULL
191#define fetch_bitfield_string_size	NULL
192
193static void
194update_bitfield_fetch_param(struct bitfield_fetch_param *data)
195{
196	/*
197	 * Don't check the bitfield itself, because this must be the
198	 * last fetch function.
199	 */
200	if (CHECK_FETCH_FUNCS(deref, data->orig.fn))
201		update_deref_fetch_param(data->orig.data);
202	else if (CHECK_FETCH_FUNCS(symbol, data->orig.fn))
203		update_symbol_cache(data->orig.data);
204}
205
206static void
207free_bitfield_fetch_param(struct bitfield_fetch_param *data)
208{
209	/*
210	 * Don't check the bitfield itself, because this must be the
211	 * last fetch function.
212	 */
213	if (CHECK_FETCH_FUNCS(deref, data->orig.fn))
214		free_deref_fetch_param(data->orig.data);
215	else if (CHECK_FETCH_FUNCS(symbol, data->orig.fn))
216		free_symbol_cache(data->orig.data);
217
218	kfree(data);
219}
220
221static const struct fetch_type *find_fetch_type(const char *type,
222						const struct fetch_type *ftbl)
223{
224	int i;
225
226	if (!type)
227		type = DEFAULT_FETCH_TYPE_STR;
228
229	/* Special case: bitfield */
230	if (*type == 'b') {
231		unsigned long bs;
232
233		type = strchr(type, '/');
234		if (!type)
235			goto fail;
236
237		type++;
238		if (kstrtoul(type, 0, &bs))
239			goto fail;
240
241		switch (bs) {
242		case 8:
243			return find_fetch_type("u8", ftbl);
244		case 16:
245			return find_fetch_type("u16", ftbl);
246		case 32:
247			return find_fetch_type("u32", ftbl);
248		case 64:
249			return find_fetch_type("u64", ftbl);
250		default:
251			goto fail;
252		}
253	}
254
255	for (i = 0; ftbl[i].name; i++) {
256		if (strcmp(type, ftbl[i].name) == 0)
257			return &ftbl[i];
258	}
259
260fail:
261	return NULL;
262}
263
264/* Special function : only accept unsigned long */
265static void fetch_kernel_stack_address(struct pt_regs *regs, void *dummy, void *dest)
266{
267	*(unsigned long *)dest = kernel_stack_pointer(regs);
268}
269NOKPROBE_SYMBOL(fetch_kernel_stack_address);
270
271static void fetch_user_stack_address(struct pt_regs *regs, void *dummy, void *dest)
272{
273	*(unsigned long *)dest = user_stack_pointer(regs);
274}
275NOKPROBE_SYMBOL(fetch_user_stack_address);
276
277static fetch_func_t get_fetch_size_function(const struct fetch_type *type,
278					    fetch_func_t orig_fn,
279					    const struct fetch_type *ftbl)
280{
281	int i;
282
283	if (type != &ftbl[FETCH_TYPE_STRING])
284		return NULL;	/* Only string type needs size function */
285
286	for (i = 0; i < FETCH_MTD_END; i++)
287		if (type->fetch[i] == orig_fn)
288			return ftbl[FETCH_TYPE_STRSIZE].fetch[i];
289
290	WARN_ON(1);	/* This should not happen */
291
292	return NULL;
293}
294
295/* Split symbol and offset. */
296int traceprobe_split_symbol_offset(char *symbol, unsigned long *offset)
297{
298	char *tmp;
299	int ret;
300
301	if (!offset)
302		return -EINVAL;
303
304	tmp = strchr(symbol, '+');
305	if (tmp) {
306		/* skip sign because kstrtoul doesn't accept '+' */
307		ret = kstrtoul(tmp + 1, 0, offset);
308		if (ret)
309			return ret;
310
311		*tmp = '\0';
312	} else
313		*offset = 0;
314
315	return 0;
316}
317
318#define PARAM_MAX_STACK (THREAD_SIZE / sizeof(unsigned long))
319
320static int parse_probe_vars(char *arg, const struct fetch_type *t,
321			    struct fetch_param *f, bool is_return,
322			    bool is_kprobe)
323{
324	int ret = 0;
325	unsigned long param;
326
327	if (strcmp(arg, "retval") == 0) {
328		if (is_return)
329			f->fn = t->fetch[FETCH_MTD_retval];
330		else
331			ret = -EINVAL;
332	} else if (strncmp(arg, "stack", 5) == 0) {
333		if (arg[5] == '\0') {
334			if (strcmp(t->name, DEFAULT_FETCH_TYPE_STR))
335				return -EINVAL;
336
337			if (is_kprobe)
338				f->fn = fetch_kernel_stack_address;
339			else
340				f->fn = fetch_user_stack_address;
341		} else if (isdigit(arg[5])) {
342			ret = kstrtoul(arg + 5, 10, &param);
343			if (ret || (is_kprobe && param > PARAM_MAX_STACK))
344				ret = -EINVAL;
345			else {
346				f->fn = t->fetch[FETCH_MTD_stack];
347				f->data = (void *)param;
348			}
349		} else
350			ret = -EINVAL;
351	} else
352		ret = -EINVAL;
353
354	return ret;
355}
356
357/* Recursive argument parser */
358static int parse_probe_arg(char *arg, const struct fetch_type *t,
359		     struct fetch_param *f, bool is_return, bool is_kprobe,
360		     const struct fetch_type *ftbl)
361{
362	unsigned long param;
363	long offset;
364	char *tmp;
365	int ret = 0;
366
367	switch (arg[0]) {
368	case '$':
369		ret = parse_probe_vars(arg + 1, t, f, is_return, is_kprobe);
370		break;
371
372	case '%':	/* named register */
373		ret = regs_query_register_offset(arg + 1);
374		if (ret >= 0) {
375			f->fn = t->fetch[FETCH_MTD_reg];
376			f->data = (void *)(unsigned long)ret;
377			ret = 0;
378		}
379		break;
380
381	case '@':	/* memory, file-offset or symbol */
382		if (isdigit(arg[1])) {
383			ret = kstrtoul(arg + 1, 0, &param);
384			if (ret)
385				break;
386
387			f->fn = t->fetch[FETCH_MTD_memory];
388			f->data = (void *)param;
389		} else if (arg[1] == '+') {
390			/* kprobes don't support file offsets */
391			if (is_kprobe)
392				return -EINVAL;
393
394			ret = kstrtol(arg + 2, 0, &offset);
395			if (ret)
396				break;
397
398			f->fn = t->fetch[FETCH_MTD_file_offset];
399			f->data = (void *)offset;
400		} else {
401			/* uprobes don't support symbols */
402			if (!is_kprobe)
403				return -EINVAL;
404
405			ret = traceprobe_split_symbol_offset(arg + 1, &offset);
406			if (ret)
407				break;
408
409			f->data = alloc_symbol_cache(arg + 1, offset);
410			if (f->data)
411				f->fn = t->fetch[FETCH_MTD_symbol];
412		}
413		break;
414
415	case '+':	/* deref memory */
416		arg++;	/* Skip '+', because kstrtol() rejects it. */
417	case '-':
418		tmp = strchr(arg, '(');
419		if (!tmp)
420			break;
421
422		*tmp = '\0';
423		ret = kstrtol(arg, 0, &offset);
424
425		if (ret)
426			break;
427
428		arg = tmp + 1;
429		tmp = strrchr(arg, ')');
430
431		if (tmp) {
432			struct deref_fetch_param	*dprm;
433			const struct fetch_type		*t2;
434
435			t2 = find_fetch_type(NULL, ftbl);
436			*tmp = '\0';
437			dprm = kzalloc(sizeof(struct deref_fetch_param), GFP_KERNEL);
438
439			if (!dprm)
440				return -ENOMEM;
441
442			dprm->offset = offset;
443			dprm->fetch = t->fetch[FETCH_MTD_memory];
444			dprm->fetch_size = get_fetch_size_function(t,
445							dprm->fetch, ftbl);
446			ret = parse_probe_arg(arg, t2, &dprm->orig, is_return,
447							is_kprobe, ftbl);
448			if (ret)
449				kfree(dprm);
450			else {
451				f->fn = t->fetch[FETCH_MTD_deref];
452				f->data = (void *)dprm;
453			}
454		}
455		break;
456	}
457	if (!ret && !f->fn) {	/* Parsed, but do not find fetch method */
458		pr_info("%s type has no corresponding fetch method.\n", t->name);
459		ret = -EINVAL;
460	}
461
462	return ret;
463}
464
465#define BYTES_TO_BITS(nb)	((BITS_PER_LONG * (nb)) / sizeof(long))
466
467/* Bitfield type needs to be parsed into a fetch function */
468static int __parse_bitfield_probe_arg(const char *bf,
469				      const struct fetch_type *t,
470				      struct fetch_param *f)
471{
472	struct bitfield_fetch_param *bprm;
473	unsigned long bw, bo;
474	char *tail;
475
476	if (*bf != 'b')
477		return 0;
478
479	bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
480	if (!bprm)
481		return -ENOMEM;
482
483	bprm->orig = *f;
484	f->fn = t->fetch[FETCH_MTD_bitfield];
485	f->data = (void *)bprm;
486	bw = simple_strtoul(bf + 1, &tail, 0);	/* Use simple one */
487
488	if (bw == 0 || *tail != '@')
489		return -EINVAL;
490
491	bf = tail + 1;
492	bo = simple_strtoul(bf, &tail, 0);
493
494	if (tail == bf || *tail != '/')
495		return -EINVAL;
496
497	bprm->hi_shift = BYTES_TO_BITS(t->size) - (bw + bo);
498	bprm->low_shift = bprm->hi_shift + bo;
499
500	return (BYTES_TO_BITS(t->size) < (bw + bo)) ? -EINVAL : 0;
501}
502
503/* String length checking wrapper */
504int traceprobe_parse_probe_arg(char *arg, ssize_t *size,
505		struct probe_arg *parg, bool is_return, bool is_kprobe,
506		const struct fetch_type *ftbl)
507{
508	const char *t;
509	int ret;
510
511	if (strlen(arg) > MAX_ARGSTR_LEN) {
512		pr_info("Argument is too long.: %s\n",  arg);
513		return -ENOSPC;
514	}
515	parg->comm = kstrdup(arg, GFP_KERNEL);
516	if (!parg->comm) {
517		pr_info("Failed to allocate memory for command '%s'.\n", arg);
518		return -ENOMEM;
519	}
520	t = strchr(parg->comm, ':');
521	if (t) {
522		arg[t - parg->comm] = '\0';
523		t++;
524	}
525	parg->type = find_fetch_type(t, ftbl);
526	if (!parg->type) {
527		pr_info("Unsupported type: %s\n", t);
528		return -EINVAL;
529	}
530	parg->offset = *size;
531	*size += parg->type->size;
532	ret = parse_probe_arg(arg, parg->type, &parg->fetch, is_return,
533			      is_kprobe, ftbl);
534
535	if (ret >= 0 && t != NULL)
536		ret = __parse_bitfield_probe_arg(t, parg->type, &parg->fetch);
537
538	if (ret >= 0) {
539		parg->fetch_size.fn = get_fetch_size_function(parg->type,
540							      parg->fetch.fn,
541							      ftbl);
542		parg->fetch_size.data = parg->fetch.data;
543	}
544
545	return ret;
546}
547
548/* Return 1 if name is reserved or already used by another argument */
549int traceprobe_conflict_field_name(const char *name,
550			       struct probe_arg *args, int narg)
551{
552	int i;
553
554	for (i = 0; i < ARRAY_SIZE(reserved_field_names); i++)
555		if (strcmp(reserved_field_names[i], name) == 0)
556			return 1;
557
558	for (i = 0; i < narg; i++)
559		if (strcmp(args[i].name, name) == 0)
560			return 1;
561
562	return 0;
563}
564
565void traceprobe_update_arg(struct probe_arg *arg)
566{
567	if (CHECK_FETCH_FUNCS(bitfield, arg->fetch.fn))
568		update_bitfield_fetch_param(arg->fetch.data);
569	else if (CHECK_FETCH_FUNCS(deref, arg->fetch.fn))
570		update_deref_fetch_param(arg->fetch.data);
571	else if (CHECK_FETCH_FUNCS(symbol, arg->fetch.fn))
572		update_symbol_cache(arg->fetch.data);
573}
574
575void traceprobe_free_probe_arg(struct probe_arg *arg)
576{
577	if (CHECK_FETCH_FUNCS(bitfield, arg->fetch.fn))
578		free_bitfield_fetch_param(arg->fetch.data);
579	else if (CHECK_FETCH_FUNCS(deref, arg->fetch.fn))
580		free_deref_fetch_param(arg->fetch.data);
581	else if (CHECK_FETCH_FUNCS(symbol, arg->fetch.fn))
582		free_symbol_cache(arg->fetch.data);
583
584	kfree(arg->name);
585	kfree(arg->comm);
586}
587
588int traceprobe_command(const char *buf, int (*createfn)(int, char **))
589{
590	char **argv;
591	int argc, ret;
592
593	argc = 0;
594	ret = 0;
595	argv = argv_split(GFP_KERNEL, buf, &argc);
596	if (!argv)
597		return -ENOMEM;
598
599	if (argc)
600		ret = createfn(argc, argv);
601
602	argv_free(argv);
603
604	return ret;
605}
606
607#define WRITE_BUFSIZE  4096
608
609ssize_t traceprobe_probes_write(struct file *file, const char __user *buffer,
610				size_t count, loff_t *ppos,
611				int (*createfn)(int, char **))
612{
613	char *kbuf, *tmp;
614	int ret = 0;
615	size_t done = 0;
616	size_t size;
617
618	kbuf = kmalloc(WRITE_BUFSIZE, GFP_KERNEL);
619	if (!kbuf)
620		return -ENOMEM;
621
622	while (done < count) {
623		size = count - done;
624
625		if (size >= WRITE_BUFSIZE)
626			size = WRITE_BUFSIZE - 1;
627
628		if (copy_from_user(kbuf, buffer + done, size)) {
629			ret = -EFAULT;
630			goto out;
631		}
632		kbuf[size] = '\0';
633		tmp = strchr(kbuf, '\n');
634
635		if (tmp) {
636			*tmp = '\0';
637			size = tmp - kbuf + 1;
638		} else if (done + size < count) {
639			pr_warning("Line length is too long: "
640				   "Should be less than %d.", WRITE_BUFSIZE);
641			ret = -EINVAL;
642			goto out;
643		}
644		done += size;
645		/* Remove comments */
646		tmp = strchr(kbuf, '#');
647
648		if (tmp)
649			*tmp = '\0';
650
651		ret = traceprobe_command(kbuf, createfn);
652		if (ret)
653			goto out;
654	}
655	ret = done;
656
657out:
658	kfree(kbuf);
659
660	return ret;
661}
662
663static int __set_print_fmt(struct trace_probe *tp, char *buf, int len,
664			   bool is_return)
665{
666	int i;
667	int pos = 0;
668
669	const char *fmt, *arg;
670
671	if (!is_return) {
672		fmt = "(%lx)";
673		arg = "REC->" FIELD_STRING_IP;
674	} else {
675		fmt = "(%lx <- %lx)";
676		arg = "REC->" FIELD_STRING_FUNC ", REC->" FIELD_STRING_RETIP;
677	}
678
679	/* When len=0, we just calculate the needed length */
680#define LEN_OR_ZERO (len ? len - pos : 0)
681
682	pos += snprintf(buf + pos, LEN_OR_ZERO, "\"%s", fmt);
683
684	for (i = 0; i < tp->nr_args; i++) {
685		pos += snprintf(buf + pos, LEN_OR_ZERO, " %s=%s",
686				tp->args[i].name, tp->args[i].type->fmt);
687	}
688
689	pos += snprintf(buf + pos, LEN_OR_ZERO, "\", %s", arg);
690
691	for (i = 0; i < tp->nr_args; i++) {
692		if (strcmp(tp->args[i].type->name, "string") == 0)
693			pos += snprintf(buf + pos, LEN_OR_ZERO,
694					", __get_str(%s)",
695					tp->args[i].name);
696		else
697			pos += snprintf(buf + pos, LEN_OR_ZERO, ", REC->%s",
698					tp->args[i].name);
699	}
700
701#undef LEN_OR_ZERO
702
703	/* return the length of print_fmt */
704	return pos;
705}
706
707int set_print_fmt(struct trace_probe *tp, bool is_return)
708{
709	int len;
710	char *print_fmt;
711
712	/* First: called with 0 length to calculate the needed length */
713	len = __set_print_fmt(tp, NULL, 0, is_return);
714	print_fmt = kmalloc(len + 1, GFP_KERNEL);
715	if (!print_fmt)
716		return -ENOMEM;
717
718	/* Second: actually write the @print_fmt */
719	__set_print_fmt(tp, print_fmt, len + 1, is_return);
720	tp->call.print_fmt = print_fmt;
721
722	return 0;
723}
724