4 * Copyright (C) 2008-2014 Red Hat Inc, Steven Rostedt <srostedt@redhat.com>
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.
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
15 * The buffer size is currently PAGE_SIZE, although it may become dynamic
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.
25 #include <linux/uaccess.h>
26 #include <linux/seq_file.h>
27 #include <linux/trace_seq.h>
29 /* How much buffer is left on the trace_seq? */
30 #define TRACE_SEQ_BUF_LEFT(s) ((PAGE_SIZE - 1) - (s)->len)
32 /* How much buffer is written? */
33 #define TRACE_SEQ_BUF_USED(s) min((s)->len, (unsigned int)(PAGE_SIZE - 1))
36 * trace_print_seq - move the contents of trace_seq into a seq_file
37 * @m: the seq_file descriptor that is the destination
38 * @s: the trace_seq descriptor that is the source.
40 * Returns 0 on success and non zero on error. If it succeeds to
41 * write to the seq_file it will reset the trace_seq, otherwise
42 * it does not modify the trace_seq to let the caller try again.
44 int trace_print_seq(struct seq_file *m, struct trace_seq *s)
46 unsigned int len = TRACE_SEQ_BUF_USED(s);
49 ret = seq_write(m, s->buffer, len);
52 * Only reset this buffer if we successfully wrote to the
53 * seq_file buffer. This lets the caller try again or
54 * do something else with the contents.
63 * trace_seq_printf - sequence printing of trace information
64 * @s: trace sequence descriptor
65 * @fmt: printf format string
67 * The tracer may use either sequence operations or its own
68 * copy to user routines. To simplify formating of a trace
69 * trace_seq_printf() is used to store strings into a special
70 * buffer (@s). Then the output may be either used by
71 * the sequencer or pulled into another buffer.
73 void trace_seq_printf(struct trace_seq *s, const char *fmt, ...)
75 unsigned int len = TRACE_SEQ_BUF_LEFT(s);
83 ret = vsnprintf(s->buffer + s->len, len, fmt, ap);
86 /* If we can't write it all, don't bother writing anything */
94 EXPORT_SYMBOL_GPL(trace_seq_printf);
97 * trace_seq_bitmask - write a bitmask array in its ASCII representation
98 * @s: trace sequence descriptor
99 * @maskp: points to an array of unsigned longs that represent a bitmask
100 * @nmaskbits: The number of bits that are valid in @maskp
102 * Writes a ASCII representation of a bitmask string into @s.
104 void trace_seq_bitmask(struct trace_seq *s, const unsigned long *maskp,
107 unsigned int len = TRACE_SEQ_BUF_LEFT(s);
113 ret = bitmap_scnprintf(s->buffer + s->len, len, maskp, nmaskbits);
116 EXPORT_SYMBOL_GPL(trace_seq_bitmask);
119 * trace_seq_vprintf - sequence printing of trace information
120 * @s: trace sequence descriptor
121 * @fmt: printf format string
123 * The tracer may use either sequence operations or its own
124 * copy to user routines. To simplify formating of a trace
125 * trace_seq_printf is used to store strings into a special
126 * buffer (@s). Then the output may be either used by
127 * the sequencer or pulled into another buffer.
129 void trace_seq_vprintf(struct trace_seq *s, const char *fmt, va_list args)
131 unsigned int len = TRACE_SEQ_BUF_LEFT(s);
137 ret = vsnprintf(s->buffer + s->len, len, fmt, args);
139 /* If we can't write it all, don't bother writing anything */
147 EXPORT_SYMBOL_GPL(trace_seq_vprintf);
150 * trace_seq_bprintf - Write the printf string from binary arguments
151 * @s: trace sequence descriptor
152 * @fmt: The format string for the @binary arguments
153 * @binary: The binary arguments for @fmt.
155 * When recording in a fast path, a printf may be recorded with just
156 * saving the format and the arguments as they were passed to the
157 * function, instead of wasting cycles converting the arguments into
158 * ASCII characters. Instead, the arguments are saved in a 32 bit
159 * word array that is defined by the format string constraints.
161 * This function will take the format and the binary array and finish
162 * the conversion into the ASCII string within the buffer.
164 void trace_seq_bprintf(struct trace_seq *s, const char *fmt, const u32 *binary)
166 unsigned int len = TRACE_SEQ_BUF_LEFT(s);
172 ret = bstr_printf(s->buffer + s->len, len, fmt, binary);
174 /* If we can't write it all, don't bother writing anything */
182 EXPORT_SYMBOL_GPL(trace_seq_bprintf);
185 * trace_seq_puts - trace sequence printing of simple string
186 * @s: trace sequence descriptor
187 * @str: simple string to record
189 * The tracer may use either the sequence operations or its own
190 * copy to user routines. This function records a simple string
191 * into a special buffer (@s) for later retrieval by a sequencer
192 * or other mechanism.
194 void trace_seq_puts(struct trace_seq *s, const char *str)
196 unsigned int len = strlen(str);
201 if (len > TRACE_SEQ_BUF_LEFT(s)) {
206 memcpy(s->buffer + s->len, str, len);
209 EXPORT_SYMBOL_GPL(trace_seq_puts);
212 * trace_seq_putc - trace sequence printing of simple character
213 * @s: trace sequence descriptor
214 * @c: simple character to record
216 * The tracer may use either the sequence operations or its own
217 * copy to user routines. This function records a simple charater
218 * into a special buffer (@s) for later retrieval by a sequencer
219 * or other mechanism.
221 void trace_seq_putc(struct trace_seq *s, unsigned char c)
226 if (TRACE_SEQ_BUF_LEFT(s) < 1) {
231 s->buffer[s->len++] = c;
233 EXPORT_SYMBOL_GPL(trace_seq_putc);
236 * trace_seq_putmem - write raw data into the trace_seq buffer
237 * @s: trace sequence descriptor
238 * @mem: The raw memory to copy into the buffer
239 * @len: The length of the raw memory to copy (in bytes)
241 * There may be cases where raw memory needs to be written into the
242 * buffer and a strcpy() would not work. Using this function allows
245 void trace_seq_putmem(struct trace_seq *s, const void *mem, unsigned int len)
250 if (len > TRACE_SEQ_BUF_LEFT(s)) {
255 memcpy(s->buffer + s->len, mem, len);
258 EXPORT_SYMBOL_GPL(trace_seq_putmem);
260 #define MAX_MEMHEX_BYTES 8U
261 #define HEX_CHARS (MAX_MEMHEX_BYTES*2 + 1)
264 * trace_seq_putmem_hex - write raw memory into the buffer in ASCII hex
265 * @s: trace sequence descriptor
266 * @mem: The raw memory to write its hex ASCII representation of
267 * @len: The length of the raw memory to copy (in bytes)
269 * This is similar to trace_seq_putmem() except instead of just copying the
270 * raw memory into the buffer it writes its ASCII representation of it
273 void trace_seq_putmem_hex(struct trace_seq *s, const void *mem,
276 unsigned char hex[HEX_CHARS];
277 const unsigned char *data = mem;
278 unsigned int start_len;
285 start_len = min(len, HEX_CHARS - 1);
287 for (i = 0, j = 0; i < start_len; i++) {
289 for (i = start_len-1, j = 0; i >= 0; i--) {
291 hex[j++] = hex_asc_hi(data[i]);
292 hex[j++] = hex_asc_lo(data[i]);
294 if (WARN_ON_ONCE(j == 0 || j/2 > len))
297 /* j increments twice per loop */
301 trace_seq_putmem(s, hex, j);
304 EXPORT_SYMBOL_GPL(trace_seq_putmem_hex);
307 * trace_seq_path - copy a path into the sequence buffer
308 * @s: trace sequence descriptor
309 * @path: path to write into the sequence buffer.
311 * Write a path name into the sequence buffer.
313 * Returns 1 if we successfully written all the contents to
315 * Returns 0 if we the length to write is bigger than the
316 * reserved buffer space. In this case, nothing gets written.
318 int trace_seq_path(struct trace_seq *s, const struct path *path)
325 if (TRACE_SEQ_BUF_LEFT(s) < 1) {
330 p = d_path(path, s->buffer + s->len, PAGE_SIZE - s->len);
332 p = mangle_path(s->buffer + s->len, p, "\n");
334 s->len = p - s->buffer;
338 s->buffer[s->len++] = '?';
345 EXPORT_SYMBOL_GPL(trace_seq_path);
348 * trace_seq_to_user - copy the squence buffer to user space
349 * @s: trace sequence descriptor
350 * @ubuf: The userspace memory location to copy to
351 * @cnt: The amount to copy
353 * Copies the sequence buffer into the userspace memory pointed to
354 * by @ubuf. It starts from the last read position (@s->readpos)
355 * and writes up to @cnt characters or till it reaches the end of
356 * the content in the buffer (@s->len), which ever comes first.
358 * On success, it returns a positive number of the number of bytes
361 * On failure it returns -EBUSY if all of the content in the
362 * sequence has been already read, which includes nothing in the
363 * sequenc (@s->len == @s->readpos).
365 * Returns -EFAULT if the copy to userspace fails.
367 int trace_seq_to_user(struct trace_seq *s, char __user *ubuf, int cnt)
375 if (s->len <= s->readpos)
378 len = s->len - s->readpos;
381 ret = copy_to_user(ubuf, s->buffer + s->readpos, cnt);
390 EXPORT_SYMBOL_GPL(trace_seq_to_user);