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);
378