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 * A write to the buffer will either succeed or fail. That is, unlike
17 * sprintf() there will not be a partial write (well it may write into
18 * the buffer but it wont update the pointers). This allows users to
19 * try to write something into the trace_seq buffer and if it fails
20 * they can flush it and try again.
21 *
22 */
23 #include <linux/uaccess.h>
24 #include <linux/seq_file.h>
25 #include <linux/trace_seq.h>
26
27 /* How much buffer is left on the trace_seq? */
28 #define TRACE_SEQ_BUF_LEFT(s) seq_buf_buffer_left(&(s)->seq)
29
30 /*
31 * trace_seq should work with being initialized with 0s.
32 */
33 static inline void __trace_seq_init(struct trace_seq *s)
34 {
35 if (unlikely(!s->seq.size))
36 trace_seq_init(s);
37 }
38
39 /**
40 * trace_print_seq - move the contents of trace_seq into a seq_file
41 * @m: the seq_file descriptor that is the destination
42 * @s: the trace_seq descriptor that is the source.
43 *
44 * Returns 0 on success and non zero on error. If it succeeds to
45 * write to the seq_file it will reset the trace_seq, otherwise
46 * it does not modify the trace_seq to let the caller try again.
47 */
48 int trace_print_seq(struct seq_file *m, struct trace_seq *s)
49 {
50 int ret;
51
52 __trace_seq_init(s);
53
54 ret = seq_buf_print_seq(m, &s->seq);
55
56 /*
57 * Only reset this buffer if we successfully wrote to the
58 * seq_file buffer. This lets the caller try again or
59 * do something else with the contents.
60 */
61 if (!ret)
62 trace_seq_init(s);
63
64 return ret;
65 }
66
67 /**
68 * trace_seq_printf - sequence printing of trace information
69 * @s: trace sequence descriptor
70 * @fmt: printf format string
71 *
72 * The tracer may use either sequence operations or its own
73 * copy to user routines. To simplify formatting of a trace
74 * trace_seq_printf() is used to store strings into a special
75 * buffer (@s). Then the output may be either used by
76 * the sequencer or pulled into another buffer.
77 */
78 void trace_seq_printf(struct trace_seq *s, const char *fmt, ...)
79 {
80 unsigned int save_len = s->seq.len;
81 va_list ap;
82
83 if (s->full)
84 return;
85
86 __trace_seq_init(s);
87
88 va_start(ap, fmt);
89 seq_buf_vprintf(&s->seq, fmt, ap);
90 va_end(ap);
91
92 /* If we can't write it all, don't bother writing anything */
93 if (unlikely(seq_buf_has_overflowed(&s->seq))) {
94 s->seq.len = save_len;
95 s->full = 1;
96 }
97 }
98 EXPORT_SYMBOL_GPL(trace_seq_printf);
99
100 /**
101 * trace_seq_bitmask - write a bitmask array in its ASCII representation
102 * @s: trace sequence descriptor
103 * @maskp: points to an array of unsigned longs that represent a bitmask
104 * @nmaskbits: The number of bits that are valid in @maskp
105 *
106 * Writes a ASCII representation of a bitmask string into @s.
107 */
108 void trace_seq_bitmask(struct trace_seq *s, const unsigned long *maskp,
109 int nmaskbits)
110 {
111 unsigned int save_len = s->seq.len;
112
113 if (s->full)
114 return;
115
116 __trace_seq_init(s);
117
118 seq_buf_printf(&s->seq, "%*pb", nmaskbits, maskp);
119
120 if (unlikely(seq_buf_has_overflowed(&s->seq))) {
121 s->seq.len = save_len;
122 s->full = 1;
123 }
124 }
125 EXPORT_SYMBOL_GPL(trace_seq_bitmask);
126
127 /**
128 * trace_seq_vprintf - sequence printing of trace information
129 * @s: trace sequence descriptor
130 * @fmt: printf format string
131 * @args: Arguments for the format string
132 *
133 * The tracer may use either sequence operations or its own
134 * copy to user routines. To simplify formatting of a trace
135 * trace_seq_printf is used to store strings into a special
136 * buffer (@s). Then the output may be either used by
137 * the sequencer or pulled into another buffer.
138 */
139 void trace_seq_vprintf(struct trace_seq *s, const char *fmt, va_list args)
140 {
141 unsigned int save_len = s->seq.len;
142
143 if (s->full)
144 return;
145
146 __trace_seq_init(s);
147
148 seq_buf_vprintf(&s->seq, fmt, args);
149
150 /* If we can't write it all, don't bother writing anything */
151 if (unlikely(seq_buf_has_overflowed(&s->seq))) {
152 s->seq.len = save_len;
153 s->full = 1;
154 }
155 }
156 EXPORT_SYMBOL_GPL(trace_seq_vprintf);
157
158 /**
159 * trace_seq_bprintf - Write the printf string from binary arguments
160 * @s: trace sequence descriptor
161 * @fmt: The format string for the @binary arguments
162 * @binary: The binary arguments for @fmt.
163 *
164 * When recording in a fast path, a printf may be recorded with just
165 * saving the format and the arguments as they were passed to the
166 * function, instead of wasting cycles converting the arguments into
167 * ASCII characters. Instead, the arguments are saved in a 32 bit
168 * word array that is defined by the format string constraints.
169 *
170 * This function will take the format and the binary array and finish
171 * the conversion into the ASCII string within the buffer.
172 */
173 void trace_seq_bprintf(struct trace_seq *s, const char *fmt, const u32 *binary)
174 {
175 unsigned int save_len = s->seq.len;
176
177 if (s->full)
178 return;
179
180 __trace_seq_init(s);
181
182 seq_buf_bprintf(&s->seq, fmt, binary);
183
184 /* If we can't write it all, don't bother writing anything */
185 if (unlikely(seq_buf_has_overflowed(&s->seq))) {
186 s->seq.len = save_len;
187 s->full = 1;
188 return;
189 }
190 }
191 EXPORT_SYMBOL_GPL(trace_seq_bprintf);
192
193 /**
194 * trace_seq_puts - trace sequence printing of simple string
195 * @s: trace sequence descriptor
196 * @str: simple string to record
197 *
198 * The tracer may use either the sequence operations or its own
199 * copy to user routines. This function records a simple string
200 * into a special buffer (@s) for later retrieval by a sequencer
201 * or other mechanism.
202 */
203 void trace_seq_puts(struct trace_seq *s, const char *str)
204 {
205 unsigned int len = strlen(str);
206
207 if (s->full)
208 return;
209
210 __trace_seq_init(s);
211
212 if (len > TRACE_SEQ_BUF_LEFT(s)) {
213 s->full = 1;
214 return;
215 }
216
217 seq_buf_putmem(&s->seq, str, len);
218 }
219 EXPORT_SYMBOL_GPL(trace_seq_puts);
220
221 /**
222 * trace_seq_putc - trace sequence printing of simple character
223 * @s: trace sequence descriptor
224 * @c: simple character to record
225 *
226 * The tracer may use either the sequence operations or its own
227 * copy to user routines. This function records a simple character
228 * into a special buffer (@s) for later retrieval by a sequencer
229 * or other mechanism.
230 */
231 void trace_seq_putc(struct trace_seq *s, unsigned char c)
232 {
233 if (s->full)
234 return;
235
236 __trace_seq_init(s);
237
238 if (TRACE_SEQ_BUF_LEFT(s) < 1) {
239 s->full = 1;
240 return;
241 }
242
243 seq_buf_putc(&s->seq, c);
244 }
245 EXPORT_SYMBOL_GPL(trace_seq_putc);
246
247 /**
248 * trace_seq_putmem - write raw data into the trace_seq buffer
249 * @s: trace sequence descriptor
250 * @mem: The raw memory to copy into the buffer
251 * @len: The length of the raw memory to copy (in bytes)
252 *
253 * There may be cases where raw memory needs to be written into the
254 * buffer and a strcpy() would not work. Using this function allows
255 * for such cases.
256 */
257 void trace_seq_putmem(struct trace_seq *s, const void *mem, unsigned int len)
258 {
259 if (s->full)
260 return;
261
262 __trace_seq_init(s);
263
264 if (len > TRACE_SEQ_BUF_LEFT(s)) {
265 s->full = 1;
266 return;
267 }
268
269 seq_buf_putmem(&s->seq, mem, len);
270 }
271 EXPORT_SYMBOL_GPL(trace_seq_putmem);
272
273 /**
274 * trace_seq_putmem_hex - write raw memory into the buffer in ASCII hex
275 * @s: trace sequence descriptor
276 * @mem: The raw memory to write its hex ASCII representation of
277 * @len: The length of the raw memory to copy (in bytes)
278 *
279 * This is similar to trace_seq_putmem() except instead of just copying the
280 * raw memory into the buffer it writes its ASCII representation of it
281 * in hex characters.
282 */
283 void trace_seq_putmem_hex(struct trace_seq *s, const void *mem,
284 unsigned int len)
285 {
286 unsigned int save_len = s->seq.len;
287
288 if (s->full)
289 return;
290
291 __trace_seq_init(s);
292
293 /* Each byte is represented by two chars */
294 if (len * 2 > TRACE_SEQ_BUF_LEFT(s)) {
295 s->full = 1;
296 return;
297 }
298
299 /* The added spaces can still cause an overflow */
300 seq_buf_putmem_hex(&s->seq, mem, len);
301
302 if (unlikely(seq_buf_has_overflowed(&s->seq))) {
303 s->seq.len = save_len;
304 s->full = 1;
305 return;
306 }
307 }
308 EXPORT_SYMBOL_GPL(trace_seq_putmem_hex);
309
310 /**
311 * trace_seq_path - copy a path into the sequence buffer
312 * @s: trace sequence descriptor
313 * @path: path to write into the sequence buffer.
314 *
315 * Write a path name into the sequence buffer.
316 *
317 * Returns 1 if we successfully written all the contents to
318 * the buffer.
319 * Returns 0 if we the length to write is bigger than the
320 * reserved buffer space. In this case, nothing gets written.
321 */
322 int trace_seq_path(struct trace_seq *s, const struct path *path)
323 {
324 unsigned int save_len = s->seq.len;
325
326 if (s->full)
327 return 0;
328
329 __trace_seq_init(s);
330
331 if (TRACE_SEQ_BUF_LEFT(s) < 1) {
332 s->full = 1;
333 return 0;
334 }
335
336 seq_buf_path(&s->seq, path, "\n");
337
338 if (unlikely(seq_buf_has_overflowed(&s->seq))) {
339 s->seq.len = save_len;
340 s->full = 1;
341 return 0;
342 }
343
344 return 1;
345 }
346 EXPORT_SYMBOL_GPL(trace_seq_path);
347
348 /**
349 * trace_seq_to_user - copy the sequence buffer to user space
350 * @s: trace sequence descriptor
351 * @ubuf: The userspace memory location to copy to
352 * @cnt: The amount to copy
353 *
354 * Copies the sequence buffer into the userspace memory pointed to
355 * by @ubuf. It starts from the last read position (@s->readpos)
356 * and writes up to @cnt characters or till it reaches the end of
357 * the content in the buffer (@s->len), which ever comes first.
358 *
359 * On success, it returns a positive number of the number of bytes
360 * it copied.
361 *
362 * On failure it returns -EBUSY if all of the content in the
363 * sequence has been already read, which includes nothing in the
364 * sequence (@s->len == @s->readpos).
365 *
366 * Returns -EFAULT if the copy to userspace fails.
367 */
368 int trace_seq_to_user(struct trace_seq *s, char __user *ubuf, int cnt)
369 {
370 int ret;
371 __trace_seq_init(s);
372 ret = seq_buf_to_user(&s->seq, ubuf, s->readpos, cnt);
373 if (ret > 0)
374 s->readpos += ret;
375 return ret;
376 }
377 EXPORT_SYMBOL_GPL(trace_seq_to_user);
378
379 int trace_seq_hex_dump(struct trace_seq *s, const char *prefix_str,
380 int prefix_type, int rowsize, int groupsize,
381 const void *buf, size_t len, bool ascii)
382 {
383 unsigned int save_len = s->seq.len;
384
385 if (s->full)
386 return 0;
387
388 __trace_seq_init(s);
389
390 if (TRACE_SEQ_BUF_LEFT(s) < 1) {
391 s->full = 1;
392 return 0;
393 }
394
395 seq_buf_hex_dump(&(s->seq), prefix_str,
396 prefix_type, rowsize, groupsize,
397 buf, len, ascii);
398
399 if (unlikely(seq_buf_has_overflowed(&s->seq))) {
400 s->seq.len = save_len;
401 s->full = 1;
402 return 0;
403 }
404
405 return 1;
406 }
407 EXPORT_SYMBOL(trace_seq_hex_dump);
408
409 /*
410 * trace_seq_acquire - acquire seq buffer with size len
411 * @s: trace sequence descriptor
412 * @len: size of buffer to be acquired
413 *
414 * acquire buffer with size of @len from trace_seq for output usage,
415 * user can fill string into that buffer.
416 *
417 * Returns start address of acquired buffer.
418 *
419 * it allow multiple usage in one trace output function call.
420 */
421 char *trace_seq_acquire(struct trace_seq *s, unsigned int len)
422 {
423 char *ret = trace_seq_buffer_ptr(s);
424
425 if (!WARN_ON_ONCE(seq_buf_buffer_left(&s->seq) < len))
426 seq_buf_commit(&s->seq, len);
427
428 return ret;
429 }
430 EXPORT_SYMBOL(trace_seq_acquire);
431
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.