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 */
 39static inline void __trace_seq_init(struct trace_seq *s)
 40{
 41	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 */
 54int trace_print_seq(struct seq_file *m, struct trace_seq *s)
 55{
 56	int ret;
 57
 58	__trace_seq_init(s);
 59
 60	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	if (!ret)
 68		trace_seq_init(s);
 69
 70	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 */
 84void trace_seq_printf(struct trace_seq *s, const char *fmt, ...)
 85{
 86	unsigned int save_len = s->seq.len;
 87	va_list ap;
 88
 89	if (s->full)
 90		return;
 91
 92	__trace_seq_init(s);
 93
 94	va_start(ap, fmt);
 95	seq_buf_vprintf(&s->seq, fmt, ap);
 96	va_end(ap);
 97
 98	/* If we can't write it all, don't bother writing anything */
 99	if (unlikely(seq_buf_has_overflowed(&s->seq))) {
100		s->seq.len = save_len;
101		s->full = 1;
102	}
103}
104EXPORT_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 */
114void trace_seq_bitmask(struct trace_seq *s, const unsigned long *maskp,
115		      int nmaskbits)
116{
117	unsigned int save_len = s->seq.len;
118
119	if (s->full)
120		return;
121
122	__trace_seq_init(s);
123
124	seq_buf_printf(&s->seq, "%*pb", nmaskbits, maskp);
125
126	if (unlikely(seq_buf_has_overflowed(&s->seq))) {
127		s->seq.len = save_len;
128		s->full = 1;
129	}
130}
131EXPORT_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 */
144void trace_seq_vprintf(struct trace_seq *s, const char *fmt, va_list args)
145{
146	unsigned int save_len = s->seq.len;
147
148	if (s->full)
149		return;
150
151	__trace_seq_init(s);
152
153	seq_buf_vprintf(&s->seq, fmt, args);
154
155	/* If we can't write it all, don't bother writing anything */
156	if (unlikely(seq_buf_has_overflowed(&s->seq))) {
157		s->seq.len = save_len;
158		s->full = 1;
159	}
160}
161EXPORT_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 */
178void trace_seq_bprintf(struct trace_seq *s, const char *fmt, const u32 *binary)
179{
180	unsigned int save_len = s->seq.len;
181
182	if (s->full)
183		return;
184
185	__trace_seq_init(s);
186
187	seq_buf_bprintf(&s->seq, fmt, binary);
188
189	/* If we can't write it all, don't bother writing anything */
190	if (unlikely(seq_buf_has_overflowed(&s->seq))) {
191		s->seq.len = save_len;
192		s->full = 1;
193		return;
194	}
195}
196EXPORT_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 */
208void trace_seq_puts(struct trace_seq *s, const char *str)
209{
210	unsigned int len = strlen(str);
211
212	if (s->full)
213		return;
214
215	__trace_seq_init(s);
216
217	if (len > TRACE_SEQ_BUF_LEFT(s)) {
218		s->full = 1;
219		return;
220	}
221
222	seq_buf_putmem(&s->seq, str, len);
223}
224EXPORT_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 */
236void trace_seq_putc(struct trace_seq *s, unsigned char c)
237{
238	if (s->full)
239		return;
240
241	__trace_seq_init(s);
242
243	if (TRACE_SEQ_BUF_LEFT(s) < 1) {
244		s->full = 1;
245		return;
246	}
247
248	seq_buf_putc(&s->seq, c);
249}
250EXPORT_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 */
262void trace_seq_putmem(struct trace_seq *s, const void *mem, unsigned int len)
263{
264	if (s->full)
265		return;
266
267	__trace_seq_init(s);
268
269	if (len > TRACE_SEQ_BUF_LEFT(s)) {
270		s->full = 1;
271		return;
272	}
273
274	seq_buf_putmem(&s->seq, mem, len);
275}
276EXPORT_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 */
288void trace_seq_putmem_hex(struct trace_seq *s, const void *mem,
289			 unsigned int len)
290{
291	unsigned int save_len = s->seq.len;
292
293	if (s->full)
294		return;
295
296	__trace_seq_init(s);
297
298	/* Each byte is represented by two chars */
299	if (len * 2 > TRACE_SEQ_BUF_LEFT(s)) {
300		s->full = 1;
301		return;
302	}
303
304	/* The added spaces can still cause an overflow */
305	seq_buf_putmem_hex(&s->seq, mem, len);
306
307	if (unlikely(seq_buf_has_overflowed(&s->seq))) {
308		s->seq.len = save_len;
309		s->full = 1;
310		return;
311	}
312}
313EXPORT_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 */
327int trace_seq_path(struct trace_seq *s, const struct path *path)
328{
329	unsigned int save_len = s->seq.len;
330
331	if (s->full)
332		return 0;
333
334	__trace_seq_init(s);
335
336	if (TRACE_SEQ_BUF_LEFT(s) < 1) {
337		s->full = 1;
338		return 0;
339	}
340
341	seq_buf_path(&s->seq, path, "\n");
342
343	if (unlikely(seq_buf_has_overflowed(&s->seq))) {
344		s->seq.len = save_len;
345		s->full = 1;
346		return 0;
347	}
348
349	return 1;
350}
351EXPORT_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 */
373int trace_seq_to_user(struct trace_seq *s, char __user *ubuf, int cnt)
374{
375	__trace_seq_init(s);
376	return seq_buf_to_user(&s->seq, ubuf, cnt);
377}
378EXPORT_SYMBOL_GPL(trace_seq_to_user);