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  *   __bitmask: This is another kind of __dynamic_array, but it expects
145  *         an array of longs, and the number of bits to parse. It takes
146  *         two parameters (name, nr_bits), where name is the name of the
147  *         bitmask to save, and the nr_bits is the number of bits to record.
148  *
149  *         __bitmask(target_cpu, nr_cpumask_bits)
150  *
151  *         To assign a bitmask, use the __assign_bitmask() helper macro.
152  *
153  *         __assign_bitmask(target_cpus, cpumask_bits(bar), nr_cpumask_bits);
154  *
155  *
156  * fast_assign: This is a C like function that is used to store the items
157  *    into the ring buffer. A special variable called "__entry" will be the
158  *    structure that points into the ring buffer and has the same fields as
159  *    described by the struct part of TRACE_EVENT above.
160  *
161  * printk: This is a way to print out the data in pretty print. This is
162  *    useful if the system crashes and you are logging via a serial line,
163  *    the data can be printed to the console using this "printk" method.
164  *    This is also used to print out the data from the trace files.
165  *    Again, the __entry macro is used to access the data from the ring buffer.
166  *
167  *    Note, __dynamic_array, __string, and __bitmask require special helpers
168  *       to access the data.
169  *
170  *      For __dynamic_array(int, foo, bar) use __get_dynamic_array(foo)
171  *            Use __get_dynamic_array_len(foo) to get the length of the array
172  *            saved. Note, __get_dynamic_array_len() returns the total allocated
173  *            length of the dynamic array; __print_array() expects the second
174  *            parameter to be the number of elements. To get that, the array length
175  *            needs to be divided by the element size.
176  *
177  *      For __string(foo, bar) use __get_str(foo)
178  *
179  *      For __bitmask(target_cpus, nr_cpumask_bits) use __get_bitmask(target_cpus)
180  *
181  *
182  * Note, that for both the assign and the printk, __entry is the handler
183  * to the data structure in the ring buffer, and is defined by the
184  * TP_STRUCT__entry.
185  */
186 
187 /*
188  * It is OK to have helper functions in the file, but they need to be protected
189  * from being defined more than once. Remember, this file gets included more
190  * than once.
191  */
192 #ifndef __TRACE_EVENT_SAMPLE_HELPER_FUNCTIONS
193 #define __TRACE_EVENT_SAMPLE_HELPER_FUNCTIONS
__length_of(const int * list)194 static inline int __length_of(const int *list)
195 {
196 	int i;
197 
198 	if (!list)
199 		return 0;
200 
201 	for (i = 0; list[i]; i++)
202 		;
203 	return i;
204 }
205 
206 enum {
207 	TRACE_SAMPLE_FOO = 2,
208 	TRACE_SAMPLE_BAR = 4,
209 	TRACE_SAMPLE_ZOO = 8,
210 };
211 #endif
212 
213 /*
214  * If enums are used in the TP_printk(), their names will be shown in
215  * format files and not their values. This can cause problems with user
216  * space programs that parse the format files to know how to translate
217  * the raw binary trace output into human readable text.
218  *
219  * To help out user space programs, any enum that is used in the TP_printk()
220  * should be defined by TRACE_DEFINE_ENUM() macro. All that is needed to
221  * be done is to add this macro with the enum within it in the trace
222  * header file, and it will be converted in the output.
223  */
224 
225 TRACE_DEFINE_ENUM(TRACE_SAMPLE_FOO);
226 TRACE_DEFINE_ENUM(TRACE_SAMPLE_BAR);
227 TRACE_DEFINE_ENUM(TRACE_SAMPLE_ZOO);
228 
229 TRACE_EVENT(foo_bar,
230 
231 	TP_PROTO(const char *foo, int bar, const int *lst,
232 		 const char *string, const struct cpumask *mask),
233 
234 	TP_ARGS(foo, bar, lst, string, mask),
235 
236 	TP_STRUCT__entry(
237 		__array(	char,	foo,    10		)
238 		__field(	int,	bar			)
239 		__dynamic_array(int,	list,   __length_of(lst))
240 		__string(	str,	string			)
241 		__bitmask(	cpus,	num_possible_cpus()	)
242 	),
243 
244 	TP_fast_assign(
245 		strlcpy(__entry->foo, foo, 10);
246 		__entry->bar	= bar;
247 		memcpy(__get_dynamic_array(list), lst,
248 		       __length_of(lst) * sizeof(int));
249 		__assign_str(str, string);
250 		__assign_bitmask(cpus, cpumask_bits(mask), num_possible_cpus());
251 	),
252 
253 	TP_printk("foo %s %d %s %s %s %s (%s)", __entry->foo, __entry->bar,
254 
255 /*
256  * Notice here the use of some helper functions. This includes:
257  *
258  *  __print_symbolic( variable, { value, "string" }, ... ),
259  *
260  *    The variable is tested against each value of the { } pair. If
261  *    the variable matches one of the values, then it will print the
262  *    string in that pair. If non are matched, it returns a string
263  *    version of the number (if __entry->bar == 7 then "7" is returned).
264  */
265 		  __print_symbolic(__entry->bar,
266 				   { 0, "zero" },
267 				   { TRACE_SAMPLE_FOO, "TWO" },
268 				   { TRACE_SAMPLE_BAR, "FOUR" },
269 				   { TRACE_SAMPLE_ZOO, "EIGHT" },
270 				   { 10, "TEN" }
271 			  ),
272 
273 /*
274  *  __print_flags( variable, "delim", { value, "flag" }, ... ),
275  *
276  *    This is similar to __print_symbolic, except that it tests the bits
277  *    of the value. If ((FLAG & variable) == FLAG) then the string is
278  *    printed. If more than one flag matches, then each one that does is
279  *    also printed with delim in between them.
280  *    If not all bits are accounted for, then the not found bits will be
281  *    added in hex format: 0x506 will show BIT2|BIT4|0x500
282  */
283 		  __print_flags(__entry->bar, "|",
284 				{ 1, "BIT1" },
285 				{ 2, "BIT2" },
286 				{ 4, "BIT3" },
287 				{ 8, "BIT4" }
288 			  ),
289 /*
290  *  __print_array( array, len, element_size )
291  *
292  *    This prints out the array that is defined by __array in a nice format.
293  */
294 		  __print_array(__get_dynamic_array(list),
295 				__get_dynamic_array_len(list) / sizeof(int),
296 				sizeof(int)),
297 		  __get_str(str), __get_bitmask(cpus))
298 );
299 
300 /*
301  * There may be a case where a tracepoint should only be called if
302  * some condition is set. Otherwise the tracepoint should not be called.
303  * But to do something like:
304  *
305  *  if (cond)
306  *     trace_foo();
307  *
308  * Would cause a little overhead when tracing is not enabled, and that
309  * overhead, even if small, is not something we want. As tracepoints
310  * use static branch (aka jump_labels), where no branch is taken to
311  * skip the tracepoint when not enabled, and a jmp is placed to jump
312  * to the tracepoint code when it is enabled, having a if statement
313  * nullifies that optimization. It would be nice to place that
314  * condition within the static branch. This is where TRACE_EVENT_CONDITION
315  * comes in.
316  *
317  * TRACE_EVENT_CONDITION() is just like TRACE_EVENT, except it adds another
318  * parameter just after args. Where TRACE_EVENT has:
319  *
320  * TRACE_EVENT(name, proto, args, struct, assign, printk)
321  *
322  * the CONDITION version has:
323  *
324  * TRACE_EVENT_CONDITION(name, proto, args, cond, struct, assign, printk)
325  *
326  * Everything is the same as TRACE_EVENT except for the new cond. Think
327  * of the cond variable as:
328  *
329  *   if (cond)
330  *      trace_foo_bar_with_cond();
331  *
332  * Except that the logic for the if branch is placed after the static branch.
333  * That is, the if statement that processes the condition will not be
334  * executed unless that traecpoint is enabled. Otherwise it still remains
335  * a nop.
336  */
337 TRACE_EVENT_CONDITION(foo_bar_with_cond,
338 
339 	TP_PROTO(const char *foo, int bar),
340 
341 	TP_ARGS(foo, bar),
342 
343 	TP_CONDITION(!(bar % 10)),
344 
345 	TP_STRUCT__entry(
346 		__string(	foo,    foo		)
347 		__field(	int,	bar			)
348 	),
349 
350 	TP_fast_assign(
351 		__assign_str(foo, foo);
352 		__entry->bar	= bar;
353 	),
354 
355 	TP_printk("foo %s %d", __get_str(foo), __entry->bar)
356 );
357 
358 int foo_bar_reg(void);
359 void foo_bar_unreg(void);
360 
361 /*
362  * Now in the case that some function needs to be called when the
363  * tracepoint is enabled and/or when it is disabled, the
364  * TRACE_EVENT_FN() serves this purpose. This is just like TRACE_EVENT()
365  * but adds two more parameters at the end:
366  *
367  * TRACE_EVENT_FN( name, proto, args, struct, assign, printk, reg, unreg)
368  *
369  * reg and unreg are functions with the prototype of:
370  *
371  *    void reg(void)
372  *
373  * The reg function gets called before the tracepoint is enabled, and
374  * the unreg function gets called after the tracepoint is disabled.
375  *
376  * Note, reg and unreg are allowed to be NULL. If you only need to
377  * call a function before enabling, or after disabling, just set one
378  * function and pass in NULL for the other parameter.
379  */
380 TRACE_EVENT_FN(foo_bar_with_fn,
381 
382 	TP_PROTO(const char *foo, int bar),
383 
384 	TP_ARGS(foo, bar),
385 
386 	TP_STRUCT__entry(
387 		__string(	foo,    foo		)
388 		__field(	int,	bar		)
389 	),
390 
391 	TP_fast_assign(
392 		__assign_str(foo, foo);
393 		__entry->bar	= bar;
394 	),
395 
396 	TP_printk("foo %s %d", __get_str(foo), __entry->bar),
397 
398 	foo_bar_reg, foo_bar_unreg
399 );
400 
401 /*
402  * Each TRACE_EVENT macro creates several helper functions to produce
403  * the code to add the tracepoint, create the files in the trace
404  * directory, hook it to perf, assign the values and to print out
405  * the raw data from the ring buffer. To prevent too much bloat,
406  * if there are more than one tracepoint that uses the same format
407  * for the proto, args, struct, assign and printk, and only the name
408  * is different, it is highly recommended to use the DECLARE_EVENT_CLASS
409  *
410  * DECLARE_EVENT_CLASS() macro creates most of the functions for the
411  * tracepoint. Then DEFINE_EVENT() is use to hook a tracepoint to those
412  * functions. This DEFINE_EVENT() is an instance of the class and can
413  * be enabled and disabled separately from other events (either TRACE_EVENT
414  * or other DEFINE_EVENT()s).
415  *
416  * Note, TRACE_EVENT() itself is simply defined as:
417  *
418  * #define TRACE_EVENT(name, proto, args, tstruct, assign, printk)  \
419  *  DECLARE_EVENT_CLASS(name, proto, args, tstruct, assign, printk); \
420  *  DEFINE_EVENT(name, name, proto, args)
421  *
422  * The DEFINE_EVENT() also can be declared with conditions and reg functions:
423  *
424  * DEFINE_EVENT_CONDITION(template, name, proto, args, cond);
425  * DEFINE_EVENT_FN(template, name, proto, args, reg, unreg);
426  */
427 DECLARE_EVENT_CLASS(foo_template,
428 
429 	TP_PROTO(const char *foo, int bar),
430 
431 	TP_ARGS(foo, bar),
432 
433 	TP_STRUCT__entry(
434 		__string(	foo,    foo		)
435 		__field(	int,	bar		)
436 	),
437 
438 	TP_fast_assign(
439 		__assign_str(foo, foo);
440 		__entry->bar	= bar;
441 	),
442 
443 	TP_printk("foo %s %d", __get_str(foo), __entry->bar)
444 );
445 
446 /*
447  * Here's a better way for the previous samples (except, the first
448  * example had more fields and could not be used here).
449  */
450 DEFINE_EVENT(foo_template, foo_with_template_simple,
451 	TP_PROTO(const char *foo, int bar),
452 	TP_ARGS(foo, bar));
453 
454 DEFINE_EVENT_CONDITION(foo_template, foo_with_template_cond,
455 	TP_PROTO(const char *foo, int bar),
456 	TP_ARGS(foo, bar),
457 	TP_CONDITION(!(bar % 8)));
458 
459 
460 DEFINE_EVENT_FN(foo_template, foo_with_template_fn,
461 	TP_PROTO(const char *foo, int bar),
462 	TP_ARGS(foo, bar),
463 	foo_bar_reg, foo_bar_unreg);
464 
465 /*
466  * Anytime two events share basically the same values and have
467  * the same output, use the DECLARE_EVENT_CLASS() and DEFINE_EVENT()
468  * when ever possible.
469  */
470 
471 /*
472  * If the event is similar to the DECLARE_EVENT_CLASS, but you need
473  * to have a different output, then use DEFINE_EVENT_PRINT() which
474  * lets you override the TP_printk() of the class.
475  */
476 
477 DEFINE_EVENT_PRINT(foo_template, foo_with_template_print,
478 	TP_PROTO(const char *foo, int bar),
479 	TP_ARGS(foo, bar),
480 	TP_printk("bar %s %d", __get_str(foo), __entry->bar));
481 
482 #endif
483 
484 /***** NOTICE! The #if protection ends here. *****/
485 
486 
487 /*
488  * There are several ways I could have done this. If I left out the
489  * TRACE_INCLUDE_PATH, then it would default to the kernel source
490  * include/trace/events directory.
491  *
492  * I could specify a path from the define_trace.h file back to this
493  * file.
494  *
495  * #define TRACE_INCLUDE_PATH ../../samples/trace_events
496  *
497  * But the safest and easiest way to simply make it use the directory
498  * that the file is in is to add in the Makefile:
499  *
500  * CFLAGS_trace-events-sample.o := -I$(src)
501  *
502  * This will make sure the current path is part of the include
503  * structure for our file so that define_trace.h can find it.
504  *
505  * I could have made only the top level directory the include:
506  *
507  * CFLAGS_trace-events-sample.o := -I$(PWD)
508  *
509  * And then let the path to this directory be the TRACE_INCLUDE_PATH:
510  *
511  * #define TRACE_INCLUDE_PATH samples/trace_events
512  *
513  * But then if something defines "samples" or "trace_events" as a macro
514  * then we could risk that being converted too, and give us an unexpected
515  * result.
516  */
517 #undef TRACE_INCLUDE_PATH
518 #undef TRACE_INCLUDE_FILE
519 #define TRACE_INCLUDE_PATH .
520 /*
521  * TRACE_INCLUDE_FILE is not needed if the filename and TRACE_SYSTEM are equal
522  */
523 #define TRACE_INCLUDE_FILE trace-events-sample
524 #include <trace/define_trace.h>
525