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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * trace_seq.c
4 *
5 * Copyright (C) 2008-2014 Red Hat Inc, Steven Rostedt <srostedt@redhat.com>
6 *
7 * The trace_seq is a handy tool that allows you to pass a descriptor around
8 * to a buffer that other functions can write to. It is similar to the
9 * seq_file functionality but has some differences.
10 *
11 * To use it, the trace_seq must be initialized with trace_seq_init().
12 * This will set up the counters within the descriptor. You can call
13 * trace_seq_init() more than once to reset the trace_seq to start
14 * from scratch.
15 *
16 * The buffer size is currently PAGE_SIZE, although it may become dynamic
17 * in the future.
18 *
19 * A write to the buffer will either succeed or fail. That is, unlike
20 * sprintf() there will not be a partial write (well it may write into
21 * the buffer but it wont update the pointers). This allows users to
22 * try to write something into the trace_seq buffer and if it fails
23 * they can flush it and try again.
24 *
25 */
26#include <linux/uaccess.h>
27#include <linux/seq_file.h>
28#include <linux/trace_seq.h>
29
30/* How much buffer is left on the trace_seq? */
31#define TRACE_SEQ_BUF_LEFT(s) seq_buf_buffer_left(&(s)->seq)
32
33/*
34 * trace_seq should work with being initialized with 0s.
35 */
36static inline void __trace_seq_init(struct trace_seq *s)
37{
38 if (unlikely(!s->seq.size))
39 trace_seq_init(s);
40}
41
42/**
43 * trace_print_seq - move the contents of trace_seq into a seq_file
44 * @m: the seq_file descriptor that is the destination
45 * @s: the trace_seq descriptor that is the source.
46 *
47 * Returns 0 on success and non zero on error. If it succeeds to
48 * write to the seq_file it will reset the trace_seq, otherwise
49 * it does not modify the trace_seq to let the caller try again.
50 */
51int trace_print_seq(struct seq_file *m, struct trace_seq *s)
52{
53 int ret;
54
55 __trace_seq_init(s);
56
57 ret = seq_buf_print_seq(m, &s->seq);
58
59 /*
60 * Only reset this buffer if we successfully wrote to the
61 * seq_file buffer. This lets the caller try again or
62 * do something else with the contents.
63 */
64 if (!ret)
65 trace_seq_init(s);
66
67 return ret;
68}
69
70/**
71 * trace_seq_printf - sequence printing of trace information
72 * @s: trace sequence descriptor
73 * @fmt: printf format string
74 *
75 * The tracer may use either sequence operations or its own
76 * copy to user routines. To simplify formatting of a trace
77 * trace_seq_printf() is used to store strings into a special
78 * buffer (@s). Then the output may be either used by
79 * the sequencer or pulled into another buffer.
80 */
81void trace_seq_printf(struct trace_seq *s, const char *fmt, ...)
82{
83 unsigned int save_len = s->seq.len;
84 va_list ap;
85
86 if (s->full)
87 return;
88
89 __trace_seq_init(s);
90
91 va_start(ap, fmt);
92 seq_buf_vprintf(&s->seq, fmt, ap);
93 va_end(ap);
94
95 /* If we can't write it all, don't bother writing anything */
96 if (unlikely(seq_buf_has_overflowed(&s->seq))) {
97 s->seq.len = save_len;
98 s->full = 1;
99 }
100}
101EXPORT_SYMBOL_GPL(trace_seq_printf);
102
103/**
104 * trace_seq_bitmask - write a bitmask array in its ASCII representation
105 * @s: trace sequence descriptor
106 * @maskp: points to an array of unsigned longs that represent a bitmask
107 * @nmaskbits: The number of bits that are valid in @maskp
108 *
109 * Writes a ASCII representation of a bitmask string into @s.
110 */
111void trace_seq_bitmask(struct trace_seq *s, const unsigned long *maskp,
112 int nmaskbits)
113{
114 unsigned int save_len = s->seq.len;
115
116 if (s->full)
117 return;
118
119 __trace_seq_init(s);
120
121 seq_buf_printf(&s->seq, "%*pb", nmaskbits, maskp);
122
123 if (unlikely(seq_buf_has_overflowed(&s->seq))) {
124 s->seq.len = save_len;
125 s->full = 1;
126 }
127}
128EXPORT_SYMBOL_GPL(trace_seq_bitmask);
129
130/**
131 * trace_seq_vprintf - sequence printing of trace information
132 * @s: trace sequence descriptor
133 * @fmt: printf format string
134 *
135 * The tracer may use either sequence operations or its own
136 * copy to user routines. To simplify formatting of a trace
137 * trace_seq_printf is used to store strings into a special
138 * buffer (@s). Then the output may be either used by
139 * the sequencer or pulled into another buffer.
140 */
141void trace_seq_vprintf(struct trace_seq *s, const char *fmt, va_list args)
142{
143 unsigned int save_len = s->seq.len;
144
145 if (s->full)
146 return;
147
148 __trace_seq_init(s);
149
150 seq_buf_vprintf(&s->seq, fmt, args);
151
152 /* If we can't write it all, don't bother writing anything */
153 if (unlikely(seq_buf_has_overflowed(&s->seq))) {
154 s->seq.len = save_len;
155 s->full = 1;
156 }
157}
158EXPORT_SYMBOL_GPL(trace_seq_vprintf);
159
160/**
161 * trace_seq_bprintf - Write the printf string from binary arguments
162 * @s: trace sequence descriptor
163 * @fmt: The format string for the @binary arguments
164 * @binary: The binary arguments for @fmt.
165 *
166 * When recording in a fast path, a printf may be recorded with just
167 * saving the format and the arguments as they were passed to the
168 * function, instead of wasting cycles converting the arguments into
169 * ASCII characters. Instead, the arguments are saved in a 32 bit
170 * word array that is defined by the format string constraints.
171 *
172 * This function will take the format and the binary array and finish
173 * the conversion into the ASCII string within the buffer.
174 */
175void trace_seq_bprintf(struct trace_seq *s, const char *fmt, const u32 *binary)
176{
177 unsigned int save_len = s->seq.len;
178
179 if (s->full)
180 return;
181
182 __trace_seq_init(s);
183
184 seq_buf_bprintf(&s->seq, fmt, binary);
185
186 /* If we can't write it all, don't bother writing anything */
187 if (unlikely(seq_buf_has_overflowed(&s->seq))) {
188 s->seq.len = save_len;
189 s->full = 1;
190 return;
191 }
192}
193EXPORT_SYMBOL_GPL(trace_seq_bprintf);
194
195/**
196 * trace_seq_puts - trace sequence printing of simple string
197 * @s: trace sequence descriptor
198 * @str: simple string to record
199 *
200 * The tracer may use either the sequence operations or its own
201 * copy to user routines. This function records a simple string
202 * into a special buffer (@s) for later retrieval by a sequencer
203 * or other mechanism.
204 */
205void trace_seq_puts(struct trace_seq *s, const char *str)
206{
207 unsigned int len = strlen(str);
208
209 if (s->full)
210 return;
211
212 __trace_seq_init(s);
213
214 if (len > TRACE_SEQ_BUF_LEFT(s)) {
215 s->full = 1;
216 return;
217 }
218
219 seq_buf_putmem(&s->seq, str, len);
220}
221EXPORT_SYMBOL_GPL(trace_seq_puts);
222
223/**
224 * trace_seq_putc - trace sequence printing of simple character
225 * @s: trace sequence descriptor
226 * @c: simple character to record
227 *
228 * The tracer may use either the sequence operations or its own
229 * copy to user routines. This function records a simple character
230 * into a special buffer (@s) for later retrieval by a sequencer
231 * or other mechanism.
232 */
233void trace_seq_putc(struct trace_seq *s, unsigned char c)
234{
235 if (s->full)
236 return;
237
238 __trace_seq_init(s);
239
240 if (TRACE_SEQ_BUF_LEFT(s) < 1) {
241 s->full = 1;
242 return;
243 }
244
245 seq_buf_putc(&s->seq, c);
246}
247EXPORT_SYMBOL_GPL(trace_seq_putc);
248
249/**
250 * trace_seq_putmem - write raw data into the trace_seq buffer
251 * @s: trace sequence descriptor
252 * @mem: The raw memory to copy into the buffer
253 * @len: The length of the raw memory to copy (in bytes)
254 *
255 * There may be cases where raw memory needs to be written into the
256 * buffer and a strcpy() would not work. Using this function allows
257 * for such cases.
258 */
259void trace_seq_putmem(struct trace_seq *s, const void *mem, unsigned int len)
260{
261 if (s->full)
262 return;
263
264 __trace_seq_init(s);
265
266 if (len > TRACE_SEQ_BUF_LEFT(s)) {
267 s->full = 1;
268 return;
269 }
270
271 seq_buf_putmem(&s->seq, mem, len);
272}
273EXPORT_SYMBOL_GPL(trace_seq_putmem);
274
275/**
276 * trace_seq_putmem_hex - write raw memory into the buffer in ASCII hex
277 * @s: trace sequence descriptor
278 * @mem: The raw memory to write its hex ASCII representation of
279 * @len: The length of the raw memory to copy (in bytes)
280 *
281 * This is similar to trace_seq_putmem() except instead of just copying the
282 * raw memory into the buffer it writes its ASCII representation of it
283 * in hex characters.
284 */
285void trace_seq_putmem_hex(struct trace_seq *s, const void *mem,
286 unsigned int len)
287{
288 unsigned int save_len = s->seq.len;
289
290 if (s->full)
291 return;
292
293 __trace_seq_init(s);
294
295 /* Each byte is represented by two chars */
296 if (len * 2 > TRACE_SEQ_BUF_LEFT(s)) {
297 s->full = 1;
298 return;
299 }
300
301 /* The added spaces can still cause an overflow */
302 seq_buf_putmem_hex(&s->seq, mem, len);
303
304 if (unlikely(seq_buf_has_overflowed(&s->seq))) {
305 s->seq.len = save_len;
306 s->full = 1;
307 return;
308 }
309}
310EXPORT_SYMBOL_GPL(trace_seq_putmem_hex);
311
312/**
313 * trace_seq_path - copy a path into the sequence buffer
314 * @s: trace sequence descriptor
315 * @path: path to write into the sequence buffer.
316 *
317 * Write a path name into the sequence buffer.
318 *
319 * Returns 1 if we successfully written all the contents to
320 * the buffer.
321 * Returns 0 if we the length to write is bigger than the
322 * reserved buffer space. In this case, nothing gets written.
323 */
324int trace_seq_path(struct trace_seq *s, const struct path *path)
325{
326 unsigned int save_len = s->seq.len;
327
328 if (s->full)
329 return 0;
330
331 __trace_seq_init(s);
332
333 if (TRACE_SEQ_BUF_LEFT(s) < 1) {
334 s->full = 1;
335 return 0;
336 }
337
338 seq_buf_path(&s->seq, path, "\n");
339
340 if (unlikely(seq_buf_has_overflowed(&s->seq))) {
341 s->seq.len = save_len;
342 s->full = 1;
343 return 0;
344 }
345
346 return 1;
347}
348EXPORT_SYMBOL_GPL(trace_seq_path);
349
350/**
351 * trace_seq_to_user - copy the sequence buffer to user space
352 * @s: trace sequence descriptor
353 * @ubuf: The userspace memory location to copy to
354 * @cnt: The amount to copy
355 *
356 * Copies the sequence buffer into the userspace memory pointed to
357 * by @ubuf. It starts from the last read position (@s->readpos)
358 * and writes up to @cnt characters or till it reaches the end of
359 * the content in the buffer (@s->len), which ever comes first.
360 *
361 * On success, it returns a positive number of the number of bytes
362 * it copied.
363 *
364 * On failure it returns -EBUSY if all of the content in the
365 * sequence has been already read, which includes nothing in the
366 * sequence (@s->len == @s->readpos).
367 *
368 * Returns -EFAULT if the copy to userspace fails.
369 */
370int trace_seq_to_user(struct trace_seq *s, char __user *ubuf, int cnt)
371{
372 __trace_seq_init(s);
373 return seq_buf_to_user(&s->seq, ubuf, cnt);
374}
375EXPORT_SYMBOL_GPL(trace_seq_to_user);
376
377int trace_seq_hex_dump(struct trace_seq *s, const char *prefix_str,
378 int prefix_type, int rowsize, int groupsize,
379 const void *buf, size_t len, bool ascii)
380{
381 unsigned int save_len = s->seq.len;
382
383 if (s->full)
384 return 0;
385
386 __trace_seq_init(s);
387
388 if (TRACE_SEQ_BUF_LEFT(s) < 1) {
389 s->full = 1;
390 return 0;
391 }
392
393 seq_buf_hex_dump(&(s->seq), prefix_str,
394 prefix_type, rowsize, groupsize,
395 buf, len, ascii);
396
397 if (unlikely(seq_buf_has_overflowed(&s->seq))) {
398 s->seq.len = save_len;
399 s->full = 1;
400 return 0;
401 }
402
403 return 1;
404}
405EXPORT_SYMBOL(trace_seq_hex_dump);
1/*
2 * trace_seq.c
3 *
4 * Copyright (C) 2008-2014 Red Hat Inc, Steven Rostedt <srostedt@redhat.com>
5 *
6 * The trace_seq is a handy tool that allows you to pass a descriptor around
7 * to a buffer that other functions can write to. It is similar to the
8 * seq_file functionality but has some differences.
9 *
10 * To use it, the trace_seq must be initialized with trace_seq_init().
11 * This will set up the counters within the descriptor. You can call
12 * trace_seq_init() more than once to reset the trace_seq to start
13 * from scratch.
14 *
15 * The buffer size is currently PAGE_SIZE, although it may become dynamic
16 * in the future.
17 *
18 * A write to the buffer will either succed or fail. That is, unlike
19 * sprintf() there will not be a partial write (well it may write into
20 * the buffer but it wont update the pointers). This allows users to
21 * try to write something into the trace_seq buffer and if it fails
22 * they can flush it and try again.
23 *
24 */
25#include <linux/uaccess.h>
26#include <linux/seq_file.h>
27#include <linux/trace_seq.h>
28
29/* How much buffer is left on the trace_seq? */
30#define TRACE_SEQ_BUF_LEFT(s) seq_buf_buffer_left(&(s)->seq)
31
32/* How much buffer is written? */
33#define TRACE_SEQ_BUF_USED(s) seq_buf_used(&(s)->seq)
34
35/*
36 * trace_seq should work with being initialized with 0s.
37 */
38static inline void __trace_seq_init(struct trace_seq *s)
39{
40 if (unlikely(!s->seq.size))
41 trace_seq_init(s);
42}
43
44/**
45 * trace_print_seq - move the contents of trace_seq into a seq_file
46 * @m: the seq_file descriptor that is the destination
47 * @s: the trace_seq descriptor that is the source.
48 *
49 * Returns 0 on success and non zero on error. If it succeeds to
50 * write to the seq_file it will reset the trace_seq, otherwise
51 * it does not modify the trace_seq to let the caller try again.
52 */
53int trace_print_seq(struct seq_file *m, struct trace_seq *s)
54{
55 int ret;
56
57 __trace_seq_init(s);
58
59 ret = seq_buf_print_seq(m, &s->seq);
60
61 /*
62 * Only reset this buffer if we successfully wrote to the
63 * seq_file buffer. This lets the caller try again or
64 * do something else with the contents.
65 */
66 if (!ret)
67 trace_seq_init(s);
68
69 return ret;
70}
71
72/**
73 * trace_seq_printf - sequence printing of trace information
74 * @s: trace sequence descriptor
75 * @fmt: printf format string
76 *
77 * The tracer may use either sequence operations or its own
78 * copy to user routines. To simplify formating of a trace
79 * trace_seq_printf() is used to store strings into a special
80 * buffer (@s). Then the output may be either used by
81 * the sequencer or pulled into another buffer.
82 */
83void trace_seq_printf(struct trace_seq *s, const char *fmt, ...)
84{
85 unsigned int save_len = s->seq.len;
86 va_list ap;
87
88 if (s->full)
89 return;
90
91 __trace_seq_init(s);
92
93 va_start(ap, fmt);
94 seq_buf_vprintf(&s->seq, fmt, ap);
95 va_end(ap);
96
97 /* If we can't write it all, don't bother writing anything */
98 if (unlikely(seq_buf_has_overflowed(&s->seq))) {
99 s->seq.len = save_len;
100 s->full = 1;
101 }
102}
103EXPORT_SYMBOL_GPL(trace_seq_printf);
104
105/**
106 * trace_seq_bitmask - write a bitmask array in its ASCII representation
107 * @s: trace sequence descriptor
108 * @maskp: points to an array of unsigned longs that represent a bitmask
109 * @nmaskbits: The number of bits that are valid in @maskp
110 *
111 * Writes a ASCII representation of a bitmask string into @s.
112 */
113void trace_seq_bitmask(struct trace_seq *s, const unsigned long *maskp,
114 int nmaskbits)
115{
116 unsigned int save_len = s->seq.len;
117
118 if (s->full)
119 return;
120
121 __trace_seq_init(s);
122
123 seq_buf_printf(&s->seq, "%*pb", nmaskbits, maskp);
124
125 if (unlikely(seq_buf_has_overflowed(&s->seq))) {
126 s->seq.len = save_len;
127 s->full = 1;
128 }
129}
130EXPORT_SYMBOL_GPL(trace_seq_bitmask);
131
132/**
133 * trace_seq_vprintf - sequence printing of trace information
134 * @s: trace sequence descriptor
135 * @fmt: printf format string
136 *
137 * The tracer may use either sequence operations or its own
138 * copy to user routines. To simplify formating of a trace
139 * trace_seq_printf is used to store strings into a special
140 * buffer (@s). Then the output may be either used by
141 * the sequencer or pulled into another buffer.
142 */
143void trace_seq_vprintf(struct trace_seq *s, const char *fmt, va_list args)
144{
145 unsigned int save_len = s->seq.len;
146
147 if (s->full)
148 return;
149
150 __trace_seq_init(s);
151
152 seq_buf_vprintf(&s->seq, fmt, args);
153
154 /* If we can't write it all, don't bother writing anything */
155 if (unlikely(seq_buf_has_overflowed(&s->seq))) {
156 s->seq.len = save_len;
157 s->full = 1;
158 }
159}
160EXPORT_SYMBOL_GPL(trace_seq_vprintf);
161
162/**
163 * trace_seq_bprintf - Write the printf string from binary arguments
164 * @s: trace sequence descriptor
165 * @fmt: The format string for the @binary arguments
166 * @binary: The binary arguments for @fmt.
167 *
168 * When recording in a fast path, a printf may be recorded with just
169 * saving the format and the arguments as they were passed to the
170 * function, instead of wasting cycles converting the arguments into
171 * ASCII characters. Instead, the arguments are saved in a 32 bit
172 * word array that is defined by the format string constraints.
173 *
174 * This function will take the format and the binary array and finish
175 * the conversion into the ASCII string within the buffer.
176 */
177void trace_seq_bprintf(struct trace_seq *s, const char *fmt, const u32 *binary)
178{
179 unsigned int save_len = s->seq.len;
180
181 if (s->full)
182 return;
183
184 __trace_seq_init(s);
185
186 seq_buf_bprintf(&s->seq, fmt, binary);
187
188 /* If we can't write it all, don't bother writing anything */
189 if (unlikely(seq_buf_has_overflowed(&s->seq))) {
190 s->seq.len = save_len;
191 s->full = 1;
192 return;
193 }
194}
195EXPORT_SYMBOL_GPL(trace_seq_bprintf);
196
197/**
198 * trace_seq_puts - trace sequence printing of simple string
199 * @s: trace sequence descriptor
200 * @str: simple string to record
201 *
202 * The tracer may use either the sequence operations or its own
203 * copy to user routines. This function records a simple string
204 * into a special buffer (@s) for later retrieval by a sequencer
205 * or other mechanism.
206 */
207void trace_seq_puts(struct trace_seq *s, const char *str)
208{
209 unsigned int len = strlen(str);
210
211 if (s->full)
212 return;
213
214 __trace_seq_init(s);
215
216 if (len > TRACE_SEQ_BUF_LEFT(s)) {
217 s->full = 1;
218 return;
219 }
220
221 seq_buf_putmem(&s->seq, str, len);
222}
223EXPORT_SYMBOL_GPL(trace_seq_puts);
224
225/**
226 * trace_seq_putc - trace sequence printing of simple character
227 * @s: trace sequence descriptor
228 * @c: simple character to record
229 *
230 * The tracer may use either the sequence operations or its own
231 * copy to user routines. This function records a simple charater
232 * into a special buffer (@s) for later retrieval by a sequencer
233 * or other mechanism.
234 */
235void trace_seq_putc(struct trace_seq *s, unsigned char c)
236{
237 if (s->full)
238 return;
239
240 __trace_seq_init(s);
241
242 if (TRACE_SEQ_BUF_LEFT(s) < 1) {
243 s->full = 1;
244 return;
245 }
246
247 seq_buf_putc(&s->seq, c);
248}
249EXPORT_SYMBOL_GPL(trace_seq_putc);
250
251/**
252 * trace_seq_putmem - write raw data into the trace_seq buffer
253 * @s: trace sequence descriptor
254 * @mem: The raw memory to copy into the buffer
255 * @len: The length of the raw memory to copy (in bytes)
256 *
257 * There may be cases where raw memory needs to be written into the
258 * buffer and a strcpy() would not work. Using this function allows
259 * for such cases.
260 */
261void trace_seq_putmem(struct trace_seq *s, const void *mem, unsigned int len)
262{
263 if (s->full)
264 return;
265
266 __trace_seq_init(s);
267
268 if (len > TRACE_SEQ_BUF_LEFT(s)) {
269 s->full = 1;
270 return;
271 }
272
273 seq_buf_putmem(&s->seq, mem, len);
274}
275EXPORT_SYMBOL_GPL(trace_seq_putmem);
276
277/**
278 * trace_seq_putmem_hex - write raw memory into the buffer in ASCII hex
279 * @s: trace sequence descriptor
280 * @mem: The raw memory to write its hex ASCII representation of
281 * @len: The length of the raw memory to copy (in bytes)
282 *
283 * This is similar to trace_seq_putmem() except instead of just copying the
284 * raw memory into the buffer it writes its ASCII representation of it
285 * in hex characters.
286 */
287void trace_seq_putmem_hex(struct trace_seq *s, const void *mem,
288 unsigned int len)
289{
290 unsigned int save_len = s->seq.len;
291
292 if (s->full)
293 return;
294
295 __trace_seq_init(s);
296
297 /* Each byte is represented by two chars */
298 if (len * 2 > TRACE_SEQ_BUF_LEFT(s)) {
299 s->full = 1;
300 return;
301 }
302
303 /* The added spaces can still cause an overflow */
304 seq_buf_putmem_hex(&s->seq, mem, len);
305
306 if (unlikely(seq_buf_has_overflowed(&s->seq))) {
307 s->seq.len = save_len;
308 s->full = 1;
309 return;
310 }
311}
312EXPORT_SYMBOL_GPL(trace_seq_putmem_hex);
313
314/**
315 * trace_seq_path - copy a path into the sequence buffer
316 * @s: trace sequence descriptor
317 * @path: path to write into the sequence buffer.
318 *
319 * Write a path name into the sequence buffer.
320 *
321 * Returns 1 if we successfully written all the contents to
322 * the buffer.
323 * Returns 0 if we the length to write is bigger than the
324 * reserved buffer space. In this case, nothing gets written.
325 */
326int trace_seq_path(struct trace_seq *s, const struct path *path)
327{
328 unsigned int save_len = s->seq.len;
329
330 if (s->full)
331 return 0;
332
333 __trace_seq_init(s);
334
335 if (TRACE_SEQ_BUF_LEFT(s) < 1) {
336 s->full = 1;
337 return 0;
338 }
339
340 seq_buf_path(&s->seq, path, "\n");
341
342 if (unlikely(seq_buf_has_overflowed(&s->seq))) {
343 s->seq.len = save_len;
344 s->full = 1;
345 return 0;
346 }
347
348 return 1;
349}
350EXPORT_SYMBOL_GPL(trace_seq_path);
351
352/**
353 * trace_seq_to_user - copy the squence buffer to user space
354 * @s: trace sequence descriptor
355 * @ubuf: The userspace memory location to copy to
356 * @cnt: The amount to copy
357 *
358 * Copies the sequence buffer into the userspace memory pointed to
359 * by @ubuf. It starts from the last read position (@s->readpos)
360 * and writes up to @cnt characters or till it reaches the end of
361 * the content in the buffer (@s->len), which ever comes first.
362 *
363 * On success, it returns a positive number of the number of bytes
364 * it copied.
365 *
366 * On failure it returns -EBUSY if all of the content in the
367 * sequence has been already read, which includes nothing in the
368 * sequenc (@s->len == @s->readpos).
369 *
370 * Returns -EFAULT if the copy to userspace fails.
371 */
372int trace_seq_to_user(struct trace_seq *s, char __user *ubuf, int cnt)
373{
374 __trace_seq_init(s);
375 return seq_buf_to_user(&s->seq, ubuf, cnt);
376}
377EXPORT_SYMBOL_GPL(trace_seq_to_user);