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1/* SPDX-License-Identifier: GPL-2.0 */
2/*
3 * If TRACE_SYSTEM is defined, that will be the directory created
4 * in the ftrace directory under /sys/kernel/tracing/events/<system>
5 *
6 * The define_trace.h below will also look for a file name of
7 * TRACE_SYSTEM.h where TRACE_SYSTEM is what is defined here.
8 * In this case, it would look for sample-trace.h
9 *
10 * If the header name will be different than the system name
11 * (as in this case), then you can override the header name that
12 * define_trace.h will look up by defining TRACE_INCLUDE_FILE
13 *
14 * This file is called trace-events-sample.h but we want the system
15 * to be called "sample-trace". Therefore we must define the name of this
16 * file:
17 *
18 * #define TRACE_INCLUDE_FILE trace-events-sample
19 *
20 * As we do an the bottom of this file.
21 *
22 * Notice that TRACE_SYSTEM should be defined outside of #if
23 * protection, just like TRACE_INCLUDE_FILE.
24 */
25#undef TRACE_SYSTEM
26#define TRACE_SYSTEM sample-trace
27
28/*
29 * TRACE_SYSTEM is expected to be a C valid variable (alpha-numeric
30 * and underscore), although it may start with numbers. If for some
31 * reason it is not, you need to add the following lines:
32 */
33#undef TRACE_SYSTEM_VAR
34#define TRACE_SYSTEM_VAR sample_trace
35/*
36 * But the above is only needed if TRACE_SYSTEM is not alpha-numeric
37 * and underscored. By default, TRACE_SYSTEM_VAR will be equal to
38 * TRACE_SYSTEM. As TRACE_SYSTEM_VAR must be alpha-numeric, if
39 * TRACE_SYSTEM is not, then TRACE_SYSTEM_VAR must be defined with
40 * only alpha-numeric and underscores.
41 *
42 * The TRACE_SYSTEM_VAR is only used internally and not visible to
43 * user space.
44 */
45
46/*
47 * Notice that this file is not protected like a normal header.
48 * We also must allow for rereading of this file. The
49 *
50 * || defined(TRACE_HEADER_MULTI_READ)
51 *
52 * serves this purpose.
53 */
54#if !defined(_TRACE_EVENT_SAMPLE_H) || defined(TRACE_HEADER_MULTI_READ)
55#define _TRACE_EVENT_SAMPLE_H
56
57/*
58 * All trace headers should include tracepoint.h, until we finally
59 * make it into a standard header.
60 */
61#include <linux/tracepoint.h>
62
63/*
64 * The TRACE_EVENT macro is broken up into 5 parts.
65 *
66 * name: name of the trace point. This is also how to enable the tracepoint.
67 * A function called trace_foo_bar() will be created.
68 *
69 * proto: the prototype of the function trace_foo_bar()
70 * Here it is trace_foo_bar(char *foo, int bar).
71 *
72 * args: must match the arguments in the prototype.
73 * Here it is simply "foo, bar".
74 *
75 * struct: This defines the way the data will be stored in the ring buffer.
76 * The items declared here become part of a special structure
77 * called "__entry", which can be used in the fast_assign part of the
78 * TRACE_EVENT macro.
79 *
80 * Here are the currently defined types you can use:
81 *
82 * __field : Is broken up into type and name. Where type can be any
83 * primitive type (integer, long or pointer).
84 *
85 * __field(int, foo)
86 *
87 * __entry->foo = 5;
88 *
89 * __field_struct : This can be any static complex data type (struct, union
90 * but not an array). Be careful using complex types, as each
91 * event is limited in size, and copying large amounts of data
92 * into the ring buffer can slow things down.
93 *
94 * __field_struct(struct bar, foo)
95 *
96 * __entry->bar.x = y;
97
98 * __array: There are three fields (type, name, size). The type is the
99 * type of elements in the array, the name is the name of the array.
100 * size is the number of items in the array (not the total size).
101 *
102 * __array( char, foo, 10) is the same as saying: char foo[10];
103 *
104 * Assigning arrays can be done like any array:
105 *
106 * __entry->foo[0] = 'a';
107 *
108 * memcpy(__entry->foo, bar, 10);
109 *
110 * __dynamic_array: This is similar to array, but can vary its size from
111 * instance to instance of the tracepoint being called.
112 * Like __array, this too has three elements (type, name, size);
113 * type is the type of the element, name is the name of the array.
114 * The size is different than __array. It is not a static number,
115 * but the algorithm to figure out the length of the array for the
116 * specific instance of tracepoint. Again, size is the number of
117 * items in the array, not the total length in bytes.
118 *
119 * __dynamic_array( int, foo, bar) is similar to: int foo[bar];
120 *
121 * Note, unlike arrays, you must use the __get_dynamic_array() macro
122 * to access the array.
123 *
124 * memcpy(__get_dynamic_array(foo), bar, 10);
125 *
126 * Notice, that "__entry" is not needed here.
127 *
128 * __string: This is a special kind of __dynamic_array. It expects to
129 * have a null terminated character array passed to it (it allows
130 * for NULL too, which would be converted into "(null)"). __string
131 * takes two parameter (name, src), where name is the name of
132 * the string saved, and src is the string to copy into the
133 * ring buffer.
134 *
135 * __string(foo, bar) is similar to: strcpy(foo, bar)
136 *
137 * To assign a string, use the helper macro __assign_str().
138 *
139 * __assign_str(foo, bar);
140 *
141 * In most cases, the __assign_str() macro will take the same
142 * parameters as the __string() macro had to declare the string.
143 *
144 * __vstring: This is similar to __string() but instead of taking a
145 * dynamic length, it takes a variable list va_list 'va' variable.
146 * Some event callers already have a message from parameters saved
147 * in a va_list. Passing in the format and the va_list variable
148 * will save just enough on the ring buffer for that string.
149 * Note, the va variable used is a pointer to a va_list, not
150 * to the va_list directly.
151 *
152 * (va_list *va)
153 *
154 * __vstring(foo, fmt, va) is similar to: vsnprintf(foo, fmt, va)
155 *
156 * To assign the string, use the helper macro __assign_vstr().
157 *
158 * __assign_vstr(foo, fmt, va);
159 *
160 * In most cases, the __assign_vstr() macro will take the same
161 * parameters as the __vstring() macro had to declare the string.
162 * Use __get_str() to retrieve the __vstring() just like it would for
163 * __string().
164 *
165 * __string_len: This is a helper to a __dynamic_array, but it understands
166 * that the array has characters in it, and with the combined
167 * use of __assign_str_len(), it will allocate 'len' + 1 bytes
168 * in the ring buffer and add a '\0' to the string. This is
169 * useful if the string being saved has no terminating '\0' byte.
170 * It requires that the length of the string is known as it acts
171 * like a memcpy().
172 *
173 * Declared with:
174 *
175 * __string_len(foo, bar, len)
176 *
177 * To assign this string, use the helper macro __assign_str_len().
178 *
179 * __assign_str_len(foo, bar, len);
180 *
181 * Then len + 1 is allocated to the ring buffer, and a nul terminating
182 * byte is added. This is similar to:
183 *
184 * memcpy(__get_str(foo), bar, len);
185 * __get_str(foo)[len] = 0;
186 *
187 * The advantage of using this over __dynamic_array, is that it
188 * takes care of allocating the extra byte on the ring buffer
189 * for the '\0' terminating byte, and __get_str(foo) can be used
190 * in the TP_printk().
191 *
192 * __bitmask: This is another kind of __dynamic_array, but it expects
193 * an array of longs, and the number of bits to parse. It takes
194 * two parameters (name, nr_bits), where name is the name of the
195 * bitmask to save, and the nr_bits is the number of bits to record.
196 *
197 * __bitmask(target_cpu, nr_cpumask_bits)
198 *
199 * To assign a bitmask, use the __assign_bitmask() helper macro.
200 *
201 * __assign_bitmask(target_cpus, cpumask_bits(bar), nr_cpumask_bits);
202 *
203 * __cpumask: This is pretty much the same as __bitmask but is specific for
204 * CPU masks. The type displayed to the user via the format files will
205 * be "cpumaks_t" such that user space may deal with them differently
206 * if they choose to do so, and the bits is always set to nr_cpumask_bits.
207 *
208 * __cpumask(target_cpu)
209 *
210 * To assign a cpumask, use the __assign_cpumask() helper macro.
211 *
212 * __assign_cpumask(target_cpus, cpumask_bits(bar));
213 *
214 * fast_assign: This is a C like function that is used to store the items
215 * into the ring buffer. A special variable called "__entry" will be the
216 * structure that points into the ring buffer and has the same fields as
217 * described by the struct part of TRACE_EVENT above.
218 *
219 * printk: This is a way to print out the data in pretty print. This is
220 * useful if the system crashes and you are logging via a serial line,
221 * the data can be printed to the console using this "printk" method.
222 * This is also used to print out the data from the trace files.
223 * Again, the __entry macro is used to access the data from the ring buffer.
224 *
225 * Note, __dynamic_array, __string, __bitmask and __cpumask require special
226 * helpers to access the data.
227 *
228 * For __dynamic_array(int, foo, bar) use __get_dynamic_array(foo)
229 * Use __get_dynamic_array_len(foo) to get the length of the array
230 * saved. Note, __get_dynamic_array_len() returns the total allocated
231 * length of the dynamic array; __print_array() expects the second
232 * parameter to be the number of elements. To get that, the array length
233 * needs to be divided by the element size.
234 *
235 * For __string(foo, bar) use __get_str(foo)
236 *
237 * For __bitmask(target_cpus, nr_cpumask_bits) use __get_bitmask(target_cpus)
238 *
239 * For __cpumask(target_cpus) use __get_cpumask(target_cpus)
240 *
241 *
242 * Note, that for both the assign and the printk, __entry is the handler
243 * to the data structure in the ring buffer, and is defined by the
244 * TP_STRUCT__entry.
245 */
246
247/*
248 * It is OK to have helper functions in the file, but they need to be protected
249 * from being defined more than once. Remember, this file gets included more
250 * than once.
251 */
252#ifndef __TRACE_EVENT_SAMPLE_HELPER_FUNCTIONS
253#define __TRACE_EVENT_SAMPLE_HELPER_FUNCTIONS
254static inline int __length_of(const int *list)
255{
256 int i;
257
258 if (!list)
259 return 0;
260
261 for (i = 0; list[i]; i++)
262 ;
263 return i;
264}
265
266enum {
267 TRACE_SAMPLE_FOO = 2,
268 TRACE_SAMPLE_BAR = 4,
269 TRACE_SAMPLE_ZOO = 8,
270};
271#endif
272
273/*
274 * If enums are used in the TP_printk(), their names will be shown in
275 * format files and not their values. This can cause problems with user
276 * space programs that parse the format files to know how to translate
277 * the raw binary trace output into human readable text.
278 *
279 * To help out user space programs, any enum that is used in the TP_printk()
280 * should be defined by TRACE_DEFINE_ENUM() macro. All that is needed to
281 * be done is to add this macro with the enum within it in the trace
282 * header file, and it will be converted in the output.
283 */
284
285TRACE_DEFINE_ENUM(TRACE_SAMPLE_FOO);
286TRACE_DEFINE_ENUM(TRACE_SAMPLE_BAR);
287TRACE_DEFINE_ENUM(TRACE_SAMPLE_ZOO);
288
289TRACE_EVENT(foo_bar,
290
291 TP_PROTO(const char *foo, int bar, const int *lst,
292 const char *string, const struct cpumask *mask,
293 const char *fmt, va_list *va),
294
295 TP_ARGS(foo, bar, lst, string, mask, fmt, va),
296
297 TP_STRUCT__entry(
298 __array( char, foo, 10 )
299 __field( int, bar )
300 __dynamic_array(int, list, __length_of(lst))
301 __string( str, string )
302 __bitmask( cpus, num_possible_cpus() )
303 __cpumask( cpum )
304 __vstring( vstr, fmt, va )
305 ),
306
307 TP_fast_assign(
308 strlcpy(__entry->foo, foo, 10);
309 __entry->bar = bar;
310 memcpy(__get_dynamic_array(list), lst,
311 __length_of(lst) * sizeof(int));
312 __assign_str(str, string);
313 __assign_vstr(vstr, fmt, va);
314 __assign_bitmask(cpus, cpumask_bits(mask), num_possible_cpus());
315 __assign_cpumask(cpum, cpumask_bits(mask));
316 ),
317
318 TP_printk("foo %s %d %s %s %s %s (%s) (%s) %s", __entry->foo, __entry->bar,
319
320/*
321 * Notice here the use of some helper functions. This includes:
322 *
323 * __print_symbolic( variable, { value, "string" }, ... ),
324 *
325 * The variable is tested against each value of the { } pair. If
326 * the variable matches one of the values, then it will print the
327 * string in that pair. If non are matched, it returns a string
328 * version of the number (if __entry->bar == 7 then "7" is returned).
329 */
330 __print_symbolic(__entry->bar,
331 { 0, "zero" },
332 { TRACE_SAMPLE_FOO, "TWO" },
333 { TRACE_SAMPLE_BAR, "FOUR" },
334 { TRACE_SAMPLE_ZOO, "EIGHT" },
335 { 10, "TEN" }
336 ),
337
338/*
339 * __print_flags( variable, "delim", { value, "flag" }, ... ),
340 *
341 * This is similar to __print_symbolic, except that it tests the bits
342 * of the value. If ((FLAG & variable) == FLAG) then the string is
343 * printed. If more than one flag matches, then each one that does is
344 * also printed with delim in between them.
345 * If not all bits are accounted for, then the not found bits will be
346 * added in hex format: 0x506 will show BIT2|BIT4|0x500
347 */
348 __print_flags(__entry->bar, "|",
349 { 1, "BIT1" },
350 { 2, "BIT2" },
351 { 4, "BIT3" },
352 { 8, "BIT4" }
353 ),
354/*
355 * __print_array( array, len, element_size )
356 *
357 * This prints out the array that is defined by __array in a nice format.
358 */
359 __print_array(__get_dynamic_array(list),
360 __get_dynamic_array_len(list) / sizeof(int),
361 sizeof(int)),
362 __get_str(str), __get_bitmask(cpus), __get_cpumask(cpum),
363 __get_str(vstr))
364);
365
366/*
367 * There may be a case where a tracepoint should only be called if
368 * some condition is set. Otherwise the tracepoint should not be called.
369 * But to do something like:
370 *
371 * if (cond)
372 * trace_foo();
373 *
374 * Would cause a little overhead when tracing is not enabled, and that
375 * overhead, even if small, is not something we want. As tracepoints
376 * use static branch (aka jump_labels), where no branch is taken to
377 * skip the tracepoint when not enabled, and a jmp is placed to jump
378 * to the tracepoint code when it is enabled, having a if statement
379 * nullifies that optimization. It would be nice to place that
380 * condition within the static branch. This is where TRACE_EVENT_CONDITION
381 * comes in.
382 *
383 * TRACE_EVENT_CONDITION() is just like TRACE_EVENT, except it adds another
384 * parameter just after args. Where TRACE_EVENT has:
385 *
386 * TRACE_EVENT(name, proto, args, struct, assign, printk)
387 *
388 * the CONDITION version has:
389 *
390 * TRACE_EVENT_CONDITION(name, proto, args, cond, struct, assign, printk)
391 *
392 * Everything is the same as TRACE_EVENT except for the new cond. Think
393 * of the cond variable as:
394 *
395 * if (cond)
396 * trace_foo_bar_with_cond();
397 *
398 * Except that the logic for the if branch is placed after the static branch.
399 * That is, the if statement that processes the condition will not be
400 * executed unless that traecpoint is enabled. Otherwise it still remains
401 * a nop.
402 */
403TRACE_EVENT_CONDITION(foo_bar_with_cond,
404
405 TP_PROTO(const char *foo, int bar),
406
407 TP_ARGS(foo, bar),
408
409 TP_CONDITION(!(bar % 10)),
410
411 TP_STRUCT__entry(
412 __string( foo, foo )
413 __field( int, bar )
414 ),
415
416 TP_fast_assign(
417 __assign_str(foo, foo);
418 __entry->bar = bar;
419 ),
420
421 TP_printk("foo %s %d", __get_str(foo), __entry->bar)
422);
423
424int foo_bar_reg(void);
425void foo_bar_unreg(void);
426
427/*
428 * Now in the case that some function needs to be called when the
429 * tracepoint is enabled and/or when it is disabled, the
430 * TRACE_EVENT_FN() serves this purpose. This is just like TRACE_EVENT()
431 * but adds two more parameters at the end:
432 *
433 * TRACE_EVENT_FN( name, proto, args, struct, assign, printk, reg, unreg)
434 *
435 * reg and unreg are functions with the prototype of:
436 *
437 * void reg(void)
438 *
439 * The reg function gets called before the tracepoint is enabled, and
440 * the unreg function gets called after the tracepoint is disabled.
441 *
442 * Note, reg and unreg are allowed to be NULL. If you only need to
443 * call a function before enabling, or after disabling, just set one
444 * function and pass in NULL for the other parameter.
445 */
446TRACE_EVENT_FN(foo_bar_with_fn,
447
448 TP_PROTO(const char *foo, int bar),
449
450 TP_ARGS(foo, bar),
451
452 TP_STRUCT__entry(
453 __string( foo, foo )
454 __field( int, bar )
455 ),
456
457 TP_fast_assign(
458 __assign_str(foo, foo);
459 __entry->bar = bar;
460 ),
461
462 TP_printk("foo %s %d", __get_str(foo), __entry->bar),
463
464 foo_bar_reg, foo_bar_unreg
465);
466
467/*
468 * Each TRACE_EVENT macro creates several helper functions to produce
469 * the code to add the tracepoint, create the files in the trace
470 * directory, hook it to perf, assign the values and to print out
471 * the raw data from the ring buffer. To prevent too much bloat,
472 * if there are more than one tracepoint that uses the same format
473 * for the proto, args, struct, assign and printk, and only the name
474 * is different, it is highly recommended to use the DECLARE_EVENT_CLASS
475 *
476 * DECLARE_EVENT_CLASS() macro creates most of the functions for the
477 * tracepoint. Then DEFINE_EVENT() is use to hook a tracepoint to those
478 * functions. This DEFINE_EVENT() is an instance of the class and can
479 * be enabled and disabled separately from other events (either TRACE_EVENT
480 * or other DEFINE_EVENT()s).
481 *
482 * Note, TRACE_EVENT() itself is simply defined as:
483 *
484 * #define TRACE_EVENT(name, proto, args, tstruct, assign, printk) \
485 * DECLARE_EVENT_CLASS(name, proto, args, tstruct, assign, printk); \
486 * DEFINE_EVENT(name, name, proto, args)
487 *
488 * The DEFINE_EVENT() also can be declared with conditions and reg functions:
489 *
490 * DEFINE_EVENT_CONDITION(template, name, proto, args, cond);
491 * DEFINE_EVENT_FN(template, name, proto, args, reg, unreg);
492 */
493DECLARE_EVENT_CLASS(foo_template,
494
495 TP_PROTO(const char *foo, int bar),
496
497 TP_ARGS(foo, bar),
498
499 TP_STRUCT__entry(
500 __string( foo, foo )
501 __field( int, bar )
502 ),
503
504 TP_fast_assign(
505 __assign_str(foo, foo);
506 __entry->bar = bar;
507 ),
508
509 TP_printk("foo %s %d", __get_str(foo), __entry->bar)
510);
511
512/*
513 * Here's a better way for the previous samples (except, the first
514 * example had more fields and could not be used here).
515 */
516DEFINE_EVENT(foo_template, foo_with_template_simple,
517 TP_PROTO(const char *foo, int bar),
518 TP_ARGS(foo, bar));
519
520DEFINE_EVENT_CONDITION(foo_template, foo_with_template_cond,
521 TP_PROTO(const char *foo, int bar),
522 TP_ARGS(foo, bar),
523 TP_CONDITION(!(bar % 8)));
524
525
526DEFINE_EVENT_FN(foo_template, foo_with_template_fn,
527 TP_PROTO(const char *foo, int bar),
528 TP_ARGS(foo, bar),
529 foo_bar_reg, foo_bar_unreg);
530
531/*
532 * Anytime two events share basically the same values and have
533 * the same output, use the DECLARE_EVENT_CLASS() and DEFINE_EVENT()
534 * when ever possible.
535 */
536
537/*
538 * If the event is similar to the DECLARE_EVENT_CLASS, but you need
539 * to have a different output, then use DEFINE_EVENT_PRINT() which
540 * lets you override the TP_printk() of the class.
541 */
542
543DEFINE_EVENT_PRINT(foo_template, foo_with_template_print,
544 TP_PROTO(const char *foo, int bar),
545 TP_ARGS(foo, bar),
546 TP_printk("bar %s %d", __get_str(foo), __entry->bar));
547
548/*
549 * There are yet another __rel_loc dynamic data attribute. If you
550 * use __rel_dynamic_array() and __rel_string() etc. macros, you
551 * can use this attribute. There is no difference from the viewpoint
552 * of functionality with/without 'rel' but the encoding is a bit
553 * different. This is expected to be used with user-space event,
554 * there is no reason that the kernel event use this, but only for
555 * testing.
556 */
557
558TRACE_EVENT(foo_rel_loc,
559
560 TP_PROTO(const char *foo, int bar, unsigned long *mask, const cpumask_t *cpus),
561
562 TP_ARGS(foo, bar, mask, cpus),
563
564 TP_STRUCT__entry(
565 __rel_string( foo, foo )
566 __field( int, bar )
567 __rel_bitmask( bitmask,
568 BITS_PER_BYTE * sizeof(unsigned long) )
569 __rel_cpumask( cpumask )
570 ),
571
572 TP_fast_assign(
573 __assign_rel_str(foo, foo);
574 __entry->bar = bar;
575 __assign_rel_bitmask(bitmask, mask,
576 BITS_PER_BYTE * sizeof(unsigned long));
577 __assign_rel_cpumask(cpumask, cpus);
578 ),
579
580 TP_printk("foo_rel_loc %s, %d, %s, %s", __get_rel_str(foo), __entry->bar,
581 __get_rel_bitmask(bitmask),
582 __get_rel_cpumask(cpumask))
583);
584#endif
585
586/***** NOTICE! The #if protection ends here. *****/
587
588
589/*
590 * There are several ways I could have done this. If I left out the
591 * TRACE_INCLUDE_PATH, then it would default to the kernel source
592 * include/trace/events directory.
593 *
594 * I could specify a path from the define_trace.h file back to this
595 * file.
596 *
597 * #define TRACE_INCLUDE_PATH ../../samples/trace_events
598 *
599 * But the safest and easiest way to simply make it use the directory
600 * that the file is in is to add in the Makefile:
601 *
602 * CFLAGS_trace-events-sample.o := -I$(src)
603 *
604 * This will make sure the current path is part of the include
605 * structure for our file so that define_trace.h can find it.
606 *
607 * I could have made only the top level directory the include:
608 *
609 * CFLAGS_trace-events-sample.o := -I$(PWD)
610 *
611 * And then let the path to this directory be the TRACE_INCLUDE_PATH:
612 *
613 * #define TRACE_INCLUDE_PATH samples/trace_events
614 *
615 * But then if something defines "samples" or "trace_events" as a macro
616 * then we could risk that being converted too, and give us an unexpected
617 * result.
618 */
619#undef TRACE_INCLUDE_PATH
620#undef TRACE_INCLUDE_FILE
621#define TRACE_INCLUDE_PATH .
622/*
623 * TRACE_INCLUDE_FILE is not needed if the filename and TRACE_SYSTEM are equal
624 */
625#define TRACE_INCLUDE_FILE trace-events-sample
626#include <trace/define_trace.h>
1/*
2 * If TRACE_SYSTEM is defined, that will be the directory created
3 * in the ftrace directory under /sys/kernel/debug/tracing/events/<system>
4 *
5 * The define_trace.h below will also look for a file name of
6 * TRACE_SYSTEM.h where TRACE_SYSTEM is what is defined here.
7 * In this case, it would look for sample.h
8 *
9 * If the header name will be different than the system name
10 * (as in this case), then you can override the header name that
11 * define_trace.h will look up by defining TRACE_INCLUDE_FILE
12 *
13 * This file is called trace-events-sample.h but we want the system
14 * to be called "sample". Therefore we must define the name of this
15 * file:
16 *
17 * #define TRACE_INCLUDE_FILE trace-events-sample
18 *
19 * As we do an the bottom of this file.
20 *
21 * Notice that TRACE_SYSTEM should be defined outside of #if
22 * protection, just like TRACE_INCLUDE_FILE.
23 */
24#undef TRACE_SYSTEM
25#define TRACE_SYSTEM sample
26
27/*
28 * Notice that this file is not protected like a normal header.
29 * We also must allow for rereading of this file. The
30 *
31 * || defined(TRACE_HEADER_MULTI_READ)
32 *
33 * serves this purpose.
34 */
35#if !defined(_TRACE_EVENT_SAMPLE_H) || defined(TRACE_HEADER_MULTI_READ)
36#define _TRACE_EVENT_SAMPLE_H
37
38/*
39 * All trace headers should include tracepoint.h, until we finally
40 * make it into a standard header.
41 */
42#include <linux/tracepoint.h>
43
44/*
45 * The TRACE_EVENT macro is broken up into 5 parts.
46 *
47 * name: name of the trace point. This is also how to enable the tracepoint.
48 * A function called trace_foo_bar() will be created.
49 *
50 * proto: the prototype of the function trace_foo_bar()
51 * Here it is trace_foo_bar(char *foo, int bar).
52 *
53 * args: must match the arguments in the prototype.
54 * Here it is simply "foo, bar".
55 *
56 * struct: This defines the way the data will be stored in the ring buffer.
57 * There are currently two types of elements. __field and __array.
58 * a __field is broken up into (type, name). Where type can be any
59 * type but an array.
60 * For an array. there are three fields. (type, name, size). The
61 * type of elements in the array, the name of the field and the size
62 * of the array.
63 *
64 * __array( char, foo, 10) is the same as saying char foo[10].
65 *
66 * fast_assign: This is a C like function that is used to store the items
67 * into the ring buffer.
68 *
69 * printk: This is a way to print out the data in pretty print. This is
70 * useful if the system crashes and you are logging via a serial line,
71 * the data can be printed to the console using this "printk" method.
72 *
73 * Note, that for both the assign and the printk, __entry is the handler
74 * to the data structure in the ring buffer, and is defined by the
75 * TP_STRUCT__entry.
76 */
77TRACE_EVENT(foo_bar,
78
79 TP_PROTO(char *foo, int bar),
80
81 TP_ARGS(foo, bar),
82
83 TP_STRUCT__entry(
84 __array( char, foo, 10 )
85 __field( int, bar )
86 ),
87
88 TP_fast_assign(
89 strncpy(__entry->foo, foo, 10);
90 __entry->bar = bar;
91 ),
92
93 TP_printk("foo %s %d", __entry->foo, __entry->bar)
94);
95#endif
96
97/***** NOTICE! The #if protection ends here. *****/
98
99
100/*
101 * There are several ways I could have done this. If I left out the
102 * TRACE_INCLUDE_PATH, then it would default to the kernel source
103 * include/trace/events directory.
104 *
105 * I could specify a path from the define_trace.h file back to this
106 * file.
107 *
108 * #define TRACE_INCLUDE_PATH ../../samples/trace_events
109 *
110 * But the safest and easiest way to simply make it use the directory
111 * that the file is in is to add in the Makefile:
112 *
113 * CFLAGS_trace-events-sample.o := -I$(src)
114 *
115 * This will make sure the current path is part of the include
116 * structure for our file so that define_trace.h can find it.
117 *
118 * I could have made only the top level directory the include:
119 *
120 * CFLAGS_trace-events-sample.o := -I$(PWD)
121 *
122 * And then let the path to this directory be the TRACE_INCLUDE_PATH:
123 *
124 * #define TRACE_INCLUDE_PATH samples/trace_events
125 *
126 * But then if something defines "samples" or "trace_events" as a macro
127 * then we could risk that being converted too, and give us an unexpected
128 * result.
129 */
130#undef TRACE_INCLUDE_PATH
131#undef TRACE_INCLUDE_FILE
132#define TRACE_INCLUDE_PATH .
133/*
134 * TRACE_INCLUDE_FILE is not needed if the filename and TRACE_SYSTEM are equal
135 */
136#define TRACE_INCLUDE_FILE trace-events-sample
137#include <trace/define_trace.h>