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