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