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