xref: /openbmc/linux/kernel/trace/trace_seq.c (revision 6c95d71b)
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  */
__trace_seq_init(struct trace_seq * s)36 static 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  */
trace_print_seq(struct seq_file * m,struct trace_seq * s)51 int 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  */
trace_seq_printf(struct trace_seq * s,const char * fmt,...)81 void 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 }
101 EXPORT_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  */
trace_seq_bitmask(struct trace_seq * s,const unsigned long * maskp,int nmaskbits)111 void 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 }
128 EXPORT_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  * @args: Arguments for the format string
135  *
136  * The tracer may use either sequence operations or its own
137  * copy to user routines. To simplify formatting of a trace
138  * trace_seq_printf is used to store strings into a special
139  * buffer (@s). Then the output may be either used by
140  * the sequencer or pulled into another buffer.
141  */
trace_seq_vprintf(struct trace_seq * s,const char * fmt,va_list args)142 void trace_seq_vprintf(struct trace_seq *s, const char *fmt, va_list args)
143 {
144 	unsigned int save_len = s->seq.len;
145 
146 	if (s->full)
147 		return;
148 
149 	__trace_seq_init(s);
150 
151 	seq_buf_vprintf(&s->seq, fmt, args);
152 
153 	/* If we can't write it all, don't bother writing anything */
154 	if (unlikely(seq_buf_has_overflowed(&s->seq))) {
155 		s->seq.len = save_len;
156 		s->full = 1;
157 	}
158 }
159 EXPORT_SYMBOL_GPL(trace_seq_vprintf);
160 
161 /**
162  * trace_seq_bprintf - Write the printf string from binary arguments
163  * @s: trace sequence descriptor
164  * @fmt: The format string for the @binary arguments
165  * @binary: The binary arguments for @fmt.
166  *
167  * When recording in a fast path, a printf may be recorded with just
168  * saving the format and the arguments as they were passed to the
169  * function, instead of wasting cycles converting the arguments into
170  * ASCII characters. Instead, the arguments are saved in a 32 bit
171  * word array that is defined by the format string constraints.
172  *
173  * This function will take the format and the binary array and finish
174  * the conversion into the ASCII string within the buffer.
175  */
trace_seq_bprintf(struct trace_seq * s,const char * fmt,const u32 * binary)176 void trace_seq_bprintf(struct trace_seq *s, const char *fmt, const u32 *binary)
177 {
178 	unsigned int save_len = s->seq.len;
179 
180 	if (s->full)
181 		return;
182 
183 	__trace_seq_init(s);
184 
185 	seq_buf_bprintf(&s->seq, fmt, binary);
186 
187 	/* If we can't write it all, don't bother writing anything */
188 	if (unlikely(seq_buf_has_overflowed(&s->seq))) {
189 		s->seq.len = save_len;
190 		s->full = 1;
191 		return;
192 	}
193 }
194 EXPORT_SYMBOL_GPL(trace_seq_bprintf);
195 
196 /**
197  * trace_seq_puts - trace sequence printing of simple string
198  * @s: trace sequence descriptor
199  * @str: simple string to record
200  *
201  * The tracer may use either the sequence operations or its own
202  * copy to user routines. This function records a simple string
203  * into a special buffer (@s) for later retrieval by a sequencer
204  * or other mechanism.
205  */
trace_seq_puts(struct trace_seq * s,const char * str)206 void trace_seq_puts(struct trace_seq *s, const char *str)
207 {
208 	unsigned int len = strlen(str);
209 
210 	if (s->full)
211 		return;
212 
213 	__trace_seq_init(s);
214 
215 	if (len > TRACE_SEQ_BUF_LEFT(s)) {
216 		s->full = 1;
217 		return;
218 	}
219 
220 	seq_buf_putmem(&s->seq, str, len);
221 }
222 EXPORT_SYMBOL_GPL(trace_seq_puts);
223 
224 /**
225  * trace_seq_putc - trace sequence printing of simple character
226  * @s: trace sequence descriptor
227  * @c: simple character to record
228  *
229  * The tracer may use either the sequence operations or its own
230  * copy to user routines. This function records a simple character
231  * into a special buffer (@s) for later retrieval by a sequencer
232  * or other mechanism.
233  */
trace_seq_putc(struct trace_seq * s,unsigned char c)234 void trace_seq_putc(struct trace_seq *s, unsigned char c)
235 {
236 	if (s->full)
237 		return;
238 
239 	__trace_seq_init(s);
240 
241 	if (TRACE_SEQ_BUF_LEFT(s) < 1) {
242 		s->full = 1;
243 		return;
244 	}
245 
246 	seq_buf_putc(&s->seq, c);
247 }
248 EXPORT_SYMBOL_GPL(trace_seq_putc);
249 
250 /**
251  * trace_seq_putmem - write raw data into the trace_seq buffer
252  * @s: trace sequence descriptor
253  * @mem: The raw memory to copy into the buffer
254  * @len: The length of the raw memory to copy (in bytes)
255  *
256  * There may be cases where raw memory needs to be written into the
257  * buffer and a strcpy() would not work. Using this function allows
258  * for such cases.
259  */
trace_seq_putmem(struct trace_seq * s,const void * mem,unsigned int len)260 void trace_seq_putmem(struct trace_seq *s, const void *mem, unsigned int len)
261 {
262 	if (s->full)
263 		return;
264 
265 	__trace_seq_init(s);
266 
267 	if (len > TRACE_SEQ_BUF_LEFT(s)) {
268 		s->full = 1;
269 		return;
270 	}
271 
272 	seq_buf_putmem(&s->seq, mem, len);
273 }
274 EXPORT_SYMBOL_GPL(trace_seq_putmem);
275 
276 /**
277  * trace_seq_putmem_hex - write raw memory into the buffer in ASCII hex
278  * @s: trace sequence descriptor
279  * @mem: The raw memory to write its hex ASCII representation of
280  * @len: The length of the raw memory to copy (in bytes)
281  *
282  * This is similar to trace_seq_putmem() except instead of just copying the
283  * raw memory into the buffer it writes its ASCII representation of it
284  * in hex characters.
285  */
trace_seq_putmem_hex(struct trace_seq * s,const void * mem,unsigned int len)286 void trace_seq_putmem_hex(struct trace_seq *s, const void *mem,
287 			 unsigned int len)
288 {
289 	unsigned int save_len = s->seq.len;
290 
291 	if (s->full)
292 		return;
293 
294 	__trace_seq_init(s);
295 
296 	/* Each byte is represented by two chars */
297 	if (len * 2 > TRACE_SEQ_BUF_LEFT(s)) {
298 		s->full = 1;
299 		return;
300 	}
301 
302 	/* The added spaces can still cause an overflow */
303 	seq_buf_putmem_hex(&s->seq, mem, len);
304 
305 	if (unlikely(seq_buf_has_overflowed(&s->seq))) {
306 		s->seq.len = save_len;
307 		s->full = 1;
308 		return;
309 	}
310 }
311 EXPORT_SYMBOL_GPL(trace_seq_putmem_hex);
312 
313 /**
314  * trace_seq_path - copy a path into the sequence buffer
315  * @s: trace sequence descriptor
316  * @path: path to write into the sequence buffer.
317  *
318  * Write a path name into the sequence buffer.
319  *
320  * Returns 1 if we successfully written all the contents to
321  *   the buffer.
322  * Returns 0 if we the length to write is bigger than the
323  *   reserved buffer space. In this case, nothing gets written.
324  */
trace_seq_path(struct trace_seq * s,const struct path * path)325 int trace_seq_path(struct trace_seq *s, const struct path *path)
326 {
327 	unsigned int save_len = s->seq.len;
328 
329 	if (s->full)
330 		return 0;
331 
332 	__trace_seq_init(s);
333 
334 	if (TRACE_SEQ_BUF_LEFT(s) < 1) {
335 		s->full = 1;
336 		return 0;
337 	}
338 
339 	seq_buf_path(&s->seq, path, "\n");
340 
341 	if (unlikely(seq_buf_has_overflowed(&s->seq))) {
342 		s->seq.len = save_len;
343 		s->full = 1;
344 		return 0;
345 	}
346 
347 	return 1;
348 }
349 EXPORT_SYMBOL_GPL(trace_seq_path);
350 
351 /**
352  * trace_seq_to_user - copy the sequence buffer to user space
353  * @s: trace sequence descriptor
354  * @ubuf: The userspace memory location to copy to
355  * @cnt: The amount to copy
356  *
357  * Copies the sequence buffer into the userspace memory pointed to
358  * by @ubuf. It starts from the last read position (@s->readpos)
359  * and writes up to @cnt characters or till it reaches the end of
360  * the content in the buffer (@s->len), which ever comes first.
361  *
362  * On success, it returns a positive number of the number of bytes
363  * it copied.
364  *
365  * On failure it returns -EBUSY if all of the content in the
366  * sequence has been already read, which includes nothing in the
367  * sequence (@s->len == @s->readpos).
368  *
369  * Returns -EFAULT if the copy to userspace fails.
370  */
trace_seq_to_user(struct trace_seq * s,char __user * ubuf,int cnt)371 int trace_seq_to_user(struct trace_seq *s, char __user *ubuf, int cnt)
372 {
373 	__trace_seq_init(s);
374 	return seq_buf_to_user(&s->seq, ubuf, cnt);
375 }
376 EXPORT_SYMBOL_GPL(trace_seq_to_user);
377 
trace_seq_hex_dump(struct trace_seq * s,const char * prefix_str,int prefix_type,int rowsize,int groupsize,const void * buf,size_t len,bool ascii)378 int trace_seq_hex_dump(struct trace_seq *s, const char *prefix_str,
379 		       int prefix_type, int rowsize, int groupsize,
380 		       const void *buf, size_t len, bool ascii)
381 {
382 	unsigned int save_len = s->seq.len;
383 
384 	if (s->full)
385 		return 0;
386 
387 	__trace_seq_init(s);
388 
389 	if (TRACE_SEQ_BUF_LEFT(s) < 1) {
390 		s->full = 1;
391 		return 0;
392 	}
393 
394 	seq_buf_hex_dump(&(s->seq), prefix_str,
395 		   prefix_type, rowsize, groupsize,
396 		   buf, len, ascii);
397 
398 	if (unlikely(seq_buf_has_overflowed(&s->seq))) {
399 		s->seq.len = save_len;
400 		s->full = 1;
401 		return 0;
402 	}
403 
404 	return 1;
405 }
406 EXPORT_SYMBOL(trace_seq_hex_dump);
407 
408 /*
409  * trace_seq_acquire - acquire seq buffer with size len
410  * @s: trace sequence descriptor
411  * @len: size of buffer to be acquired
412  *
413  * acquire buffer with size of @len from trace_seq for output usage,
414  * user can fill string into that buffer.
415  *
416  * Returns start address of acquired buffer.
417  *
418  * it allow multiple usage in one trace output function call.
419  */
trace_seq_acquire(struct trace_seq * s,unsigned int len)420 char *trace_seq_acquire(struct trace_seq *s, unsigned int len)
421 {
422 	char *ret = trace_seq_buffer_ptr(s);
423 
424 	if (!WARN_ON_ONCE(seq_buf_buffer_left(&s->seq) < len))
425 		seq_buf_commit(&s->seq, len);
426 
427 	return ret;
428 }
429 EXPORT_SYMBOL(trace_seq_acquire);
430