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1/* SPDX-License-Identifier: GPL-2.0 */2/*3 * If TRACE_SYSTEM is defined, that will be the directory created4 * in the ftrace directory under /sys/kernel/tracing/events/<system>5 *6 * The define_trace.h below will also look for a file name of7 * TRACE_SYSTEM.h where TRACE_SYSTEM is what is defined here.8 * In this case, it would look for sample-trace.h9 *10 * If the header name will be different than the system name11 * (as in this case), then you can override the header name that12 * define_trace.h will look up by defining TRACE_INCLUDE_FILE13 *14 * This file is called trace-events-sample.h but we want the system15 * to be called "sample-trace". Therefore we must define the name of this16 * file:17 *18 * #define TRACE_INCLUDE_FILE trace-events-sample19 *20 * As we do an the bottom of this file.21 *22 * Notice that TRACE_SYSTEM should be defined outside of #if23 * protection, just like TRACE_INCLUDE_FILE.24 */25#undef TRACE_SYSTEM26#define TRACE_SYSTEM sample-trace27 28/*29 * TRACE_SYSTEM is expected to be a C valid variable (alpha-numeric30 * and underscore), although it may start with numbers. If for some31 * reason it is not, you need to add the following lines:32 */33#undef TRACE_SYSTEM_VAR34#define TRACE_SYSTEM_VAR sample_trace35/*36 * But the above is only needed if TRACE_SYSTEM is not alpha-numeric37 * and underscored. By default, TRACE_SYSTEM_VAR will be equal to38 * TRACE_SYSTEM. As TRACE_SYSTEM_VAR must be alpha-numeric, if39 * TRACE_SYSTEM is not, then TRACE_SYSTEM_VAR must be defined with40 * only alpha-numeric and underscores.41 *42 * The TRACE_SYSTEM_VAR is only used internally and not visible to43 * 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. The49 *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_H56 57/*58 * All trace headers should include tracepoint.h, until we finally59 * 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 structure77 * called "__entry", which can be used in the fast_assign part of the78 * 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 any83 * 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, union90 * but not an array). Be careful using complex types, as each91 * event is limited in size, and copying large amounts of data92 * 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 the99 * 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 from111 * 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 the116 * specific instance of tracepoint. Again, size is the number of117 * 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() macro122 * 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 to129 * have a null terminated character array passed to it (it allows130 * for NULL too, which would be converted into "(null)"). __string131 * takes two parameter (name, src), where name is the name of132 * the string saved, and src is the string to copy into the133 * 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);140 *141 * The __string() macro saves off the string that is passed into142 * the second parameter, and the __assign_str() will store than143 * saved string into the "foo" field.144 *145 * __vstring: This is similar to __string() but instead of taking a146 * dynamic length, it takes a variable list va_list 'va' variable.147 * Some event callers already have a message from parameters saved148 * in a va_list. Passing in the format and the va_list variable149 * will save just enough on the ring buffer for that string.150 * Note, the va variable used is a pointer to a va_list, not151 * to the va_list directly.152 *153 * (va_list *va)154 *155 * __vstring(foo, fmt, va) is similar to: vsnprintf(foo, fmt, va)156 *157 * To assign the string, use the helper macro __assign_vstr().158 *159 * __assign_vstr(foo, fmt, va);160 *161 * In most cases, the __assign_vstr() macro will take the same162 * parameters as the __vstring() macro had to declare the string.163 * Use __get_str() to retrieve the __vstring() just like it would for164 * __string().165 *166 * __string_len: This is a helper to a __dynamic_array, but it understands167 * that the array has characters in it, it will allocate 'len' + 1 bytes168 * in the ring buffer and add a '\0' to the string. This is169 * useful if the string being saved has no terminating '\0' byte.170 * It requires that the length of the string is known as it acts171 * 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().178 * The length is saved via the __string_len() and is retrieved in179 * __assign_str().180 *181 * __assign_str(foo);182 *183 * Then len + 1 is allocated to the ring buffer, and a nul terminating184 * byte is added. This is similar to:185 *186 * memcpy(__get_str(foo), bar, len);187 * __get_str(foo)[len] = 0;188 *189 * The advantage of using this over __dynamic_array, is that it190 * takes care of allocating the extra byte on the ring buffer191 * for the '\0' terminating byte, and __get_str(foo) can be used192 * in the TP_printk().193 *194 * __bitmask: This is another kind of __dynamic_array, but it expects195 * an array of longs, and the number of bits to parse. It takes196 * two parameters (name, nr_bits), where name is the name of the197 * bitmask to save, and the nr_bits is the number of bits to record.198 *199 * __bitmask(target_cpu, nr_cpumask_bits)200 *201 * To assign a bitmask, use the __assign_bitmask() helper macro.202 *203 * __assign_bitmask(target_cpus, cpumask_bits(bar), nr_cpumask_bits);204 *205 * __cpumask: This is pretty much the same as __bitmask but is specific for206 * CPU masks. The type displayed to the user via the format files will207 * be "cpumaks_t" such that user space may deal with them differently208 * if they choose to do so, and the bits is always set to nr_cpumask_bits.209 *210 * __cpumask(target_cpu)211 *212 * To assign a cpumask, use the __assign_cpumask() helper macro.213 *214 * __assign_cpumask(target_cpus, cpumask_bits(bar));215 *216 * fast_assign: This is a C like function that is used to store the items217 * into the ring buffer. A special variable called "__entry" will be the218 * structure that points into the ring buffer and has the same fields as219 * described by the struct part of TRACE_EVENT above.220 *221 * printk: This is a way to print out the data in pretty print. This is222 * useful if the system crashes and you are logging via a serial line,223 * the data can be printed to the console using this "printk" method.224 * This is also used to print out the data from the trace files.225 * Again, the __entry macro is used to access the data from the ring buffer.226 *227 * Note, __dynamic_array, __string, __bitmask and __cpumask require special228 * helpers to access the data.229 *230 * For __dynamic_array(int, foo, bar) use __get_dynamic_array(foo)231 * Use __get_dynamic_array_len(foo) to get the length of the array232 * saved. Note, __get_dynamic_array_len() returns the total allocated233 * length of the dynamic array; __print_array() expects the second234 * parameter to be the number of elements. To get that, the array length235 * needs to be divided by the element size.236 *237 * For __string(foo, bar) use __get_str(foo)238 *239 * For __bitmask(target_cpus, nr_cpumask_bits) use __get_bitmask(target_cpus)240 *241 * For __cpumask(target_cpus) use __get_cpumask(target_cpus)242 *243 *244 * Note, that for both the assign and the printk, __entry is the handler245 * to the data structure in the ring buffer, and is defined by the246 * TP_STRUCT__entry.247 */248 249/*250 * It is OK to have helper functions in the file, but they need to be protected251 * from being defined more than once. Remember, this file gets included more252 * than once.253 */254#ifndef __TRACE_EVENT_SAMPLE_HELPER_FUNCTIONS255#define __TRACE_EVENT_SAMPLE_HELPER_FUNCTIONS256static inline int __length_of(const int *list)257{258 int i;259 260 if (!list)261 return 0;262 263 for (i = 0; list[i]; i++)264 ;265 return i;266}267 268enum {269 TRACE_SAMPLE_FOO = 2,270 TRACE_SAMPLE_BAR = 4,271 TRACE_SAMPLE_ZOO = 8,272};273#endif274 275/*276 * If enums are used in the TP_printk(), their names will be shown in277 * format files and not their values. This can cause problems with user278 * space programs that parse the format files to know how to translate279 * the raw binary trace output into human readable text.280 *281 * To help out user space programs, any enum that is used in the TP_printk()282 * should be defined by TRACE_DEFINE_ENUM() macro. All that is needed to283 * be done is to add this macro with the enum within it in the trace284 * header file, and it will be converted in the output.285 */286 287TRACE_DEFINE_ENUM(TRACE_SAMPLE_FOO);288TRACE_DEFINE_ENUM(TRACE_SAMPLE_BAR);289TRACE_DEFINE_ENUM(TRACE_SAMPLE_ZOO);290 291TRACE_EVENT(foo_bar,292 293 TP_PROTO(const char *foo, int bar, const int *lst,294 const char *string, const struct cpumask *mask,295 const char *fmt, va_list *va),296 297 TP_ARGS(foo, bar, lst, string, mask, fmt, va),298 299 TP_STRUCT__entry(300 __array( char, foo, 10 )301 __field( int, bar )302 __dynamic_array(int, list, __length_of(lst))303 __string( str, string )304 __bitmask( cpus, num_possible_cpus() )305 __cpumask( cpum )306 __vstring( vstr, fmt, va )307 __string_len( lstr, foo, bar / 2 < strlen(foo) ? bar / 2 : strlen(foo) )308 ),309 310 TP_fast_assign(311 strscpy(__entry->foo, foo, 10);312 __entry->bar = bar;313 memcpy(__get_dynamic_array(list), lst,314 __length_of(lst) * sizeof(int));315 __assign_str(str);316 __assign_str(lstr);317 __assign_vstr(vstr, fmt, va);318 __assign_bitmask(cpus, cpumask_bits(mask), num_possible_cpus());319 __assign_cpumask(cpum, cpumask_bits(mask));320 ),321 322 TP_printk("foo %s %d %s %s %s %s %s (%s) (%s) %s", __entry->foo, __entry->bar,323 324/*325 * Notice here the use of some helper functions. This includes:326 *327 * __print_symbolic( variable, { value, "string" }, ... ),328 *329 * The variable is tested against each value of the { } pair. If330 * the variable matches one of the values, then it will print the331 * string in that pair. If non are matched, it returns a string332 * version of the number (if __entry->bar == 7 then "7" is returned).333 */334 __print_symbolic(__entry->bar,335 { 0, "zero" },336 { TRACE_SAMPLE_FOO, "TWO" },337 { TRACE_SAMPLE_BAR, "FOUR" },338 { TRACE_SAMPLE_ZOO, "EIGHT" },339 { 10, "TEN" }340 ),341 342/*343 * __print_flags( variable, "delim", { value, "flag" }, ... ),344 *345 * This is similar to __print_symbolic, except that it tests the bits346 * of the value. If ((FLAG & variable) == FLAG) then the string is347 * printed. If more than one flag matches, then each one that does is348 * also printed with delim in between them.349 * If not all bits are accounted for, then the not found bits will be350 * added in hex format: 0x506 will show BIT2|BIT4|0x500351 */352 __print_flags(__entry->bar, "|",353 { 1, "BIT1" },354 { 2, "BIT2" },355 { 4, "BIT3" },356 { 8, "BIT4" }357 ),358/*359 * __print_array( array, len, element_size )360 *361 * This prints out the array that is defined by __array in a nice format.362 */363 __print_array(__get_dynamic_array(list),364 __get_dynamic_array_len(list) / sizeof(int),365 sizeof(int)),366 __get_str(str), __get_str(lstr),367 __get_bitmask(cpus), __get_cpumask(cpum),368 __get_str(vstr))369);370 371/*372 * There may be a case where a tracepoint should only be called if373 * some condition is set. Otherwise the tracepoint should not be called.374 * But to do something like:375 *376 * if (cond)377 * trace_foo();378 *379 * Would cause a little overhead when tracing is not enabled, and that380 * overhead, even if small, is not something we want. As tracepoints381 * use static branch (aka jump_labels), where no branch is taken to382 * skip the tracepoint when not enabled, and a jmp is placed to jump383 * to the tracepoint code when it is enabled, having a if statement384 * nullifies that optimization. It would be nice to place that385 * condition within the static branch. This is where TRACE_EVENT_CONDITION386 * comes in.387 *388 * TRACE_EVENT_CONDITION() is just like TRACE_EVENT, except it adds another389 * parameter just after args. Where TRACE_EVENT has:390 *391 * TRACE_EVENT(name, proto, args, struct, assign, printk)392 *393 * the CONDITION version has:394 *395 * TRACE_EVENT_CONDITION(name, proto, args, cond, struct, assign, printk)396 *397 * Everything is the same as TRACE_EVENT except for the new cond. Think398 * of the cond variable as:399 *400 * if (cond)401 * trace_foo_bar_with_cond();402 *403 * Except that the logic for the if branch is placed after the static branch.404 * That is, the if statement that processes the condition will not be405 * executed unless that traecpoint is enabled. Otherwise it still remains406 * a nop.407 */408TRACE_EVENT_CONDITION(foo_bar_with_cond,409 410 TP_PROTO(const char *foo, int bar),411 412 TP_ARGS(foo, bar),413 414 TP_CONDITION(!(bar % 10)),415 416 TP_STRUCT__entry(417 __string( foo, foo )418 __field( int, bar )419 ),420 421 TP_fast_assign(422 __assign_str(foo);423 __entry->bar = bar;424 ),425 426 TP_printk("foo %s %d", __get_str(foo), __entry->bar)427);428 429int foo_bar_reg(void);430void foo_bar_unreg(void);431 432/*433 * Now in the case that some function needs to be called when the434 * tracepoint is enabled and/or when it is disabled, the435 * TRACE_EVENT_FN() serves this purpose. This is just like TRACE_EVENT()436 * but adds two more parameters at the end:437 *438 * TRACE_EVENT_FN( name, proto, args, struct, assign, printk, reg, unreg)439 *440 * reg and unreg are functions with the prototype of:441 *442 * void reg(void)443 *444 * The reg function gets called before the tracepoint is enabled, and445 * the unreg function gets called after the tracepoint is disabled.446 *447 * Note, reg and unreg are allowed to be NULL. If you only need to448 * call a function before enabling, or after disabling, just set one449 * function and pass in NULL for the other parameter.450 */451TRACE_EVENT_FN(foo_bar_with_fn,452 453 TP_PROTO(const char *foo, int bar),454 455 TP_ARGS(foo, bar),456 457 TP_STRUCT__entry(458 __string( foo, foo )459 __field( int, bar )460 ),461 462 TP_fast_assign(463 __assign_str(foo);464 __entry->bar = bar;465 ),466 467 TP_printk("foo %s %d", __get_str(foo), __entry->bar),468 469 foo_bar_reg, foo_bar_unreg470);471 472/*473 * Each TRACE_EVENT macro creates several helper functions to produce474 * the code to add the tracepoint, create the files in the trace475 * directory, hook it to perf, assign the values and to print out476 * the raw data from the ring buffer. To prevent too much bloat,477 * if there are more than one tracepoint that uses the same format478 * for the proto, args, struct, assign and printk, and only the name479 * is different, it is highly recommended to use the DECLARE_EVENT_CLASS480 *481 * DECLARE_EVENT_CLASS() macro creates most of the functions for the482 * tracepoint. Then DEFINE_EVENT() is use to hook a tracepoint to those483 * functions. This DEFINE_EVENT() is an instance of the class and can484 * be enabled and disabled separately from other events (either TRACE_EVENT485 * or other DEFINE_EVENT()s).486 *487 * Note, TRACE_EVENT() itself is simply defined as:488 *489 * #define TRACE_EVENT(name, proto, args, tstruct, assign, printk) \490 * DECLARE_EVENT_CLASS(name, proto, args, tstruct, assign, printk); \491 * DEFINE_EVENT(name, name, proto, args)492 *493 * The DEFINE_EVENT() also can be declared with conditions and reg functions:494 *495 * DEFINE_EVENT_CONDITION(template, name, proto, args, cond);496 * DEFINE_EVENT_FN(template, name, proto, args, reg, unreg);497 */498DECLARE_EVENT_CLASS(foo_template,499 500 TP_PROTO(const char *foo, int bar),501 502 TP_ARGS(foo, bar),503 504 TP_STRUCT__entry(505 __string( foo, foo )506 __field( int, bar )507 ),508 509 TP_fast_assign(510 __assign_str(foo);511 __entry->bar = bar;512 ),513 514 TP_printk("foo %s %d", __get_str(foo), __entry->bar)515);516 517/*518 * Here's a better way for the previous samples (except, the first519 * example had more fields and could not be used here).520 */521DEFINE_EVENT(foo_template, foo_with_template_simple,522 TP_PROTO(const char *foo, int bar),523 TP_ARGS(foo, bar));524 525DEFINE_EVENT_CONDITION(foo_template, foo_with_template_cond,526 TP_PROTO(const char *foo, int bar),527 TP_ARGS(foo, bar),528 TP_CONDITION(!(bar % 8)));529 530 531DEFINE_EVENT_FN(foo_template, foo_with_template_fn,532 TP_PROTO(const char *foo, int bar),533 TP_ARGS(foo, bar),534 foo_bar_reg, foo_bar_unreg);535 536/*537 * Anytime two events share basically the same values and have538 * the same output, use the DECLARE_EVENT_CLASS() and DEFINE_EVENT()539 * when ever possible.540 */541 542/*543 * If the event is similar to the DECLARE_EVENT_CLASS, but you need544 * to have a different output, then use DEFINE_EVENT_PRINT() which545 * lets you override the TP_printk() of the class.546 */547 548DEFINE_EVENT_PRINT(foo_template, foo_with_template_print,549 TP_PROTO(const char *foo, int bar),550 TP_ARGS(foo, bar),551 TP_printk("bar %s %d", __get_str(foo), __entry->bar));552 553/*554 * There are yet another __rel_loc dynamic data attribute. If you555 * use __rel_dynamic_array() and __rel_string() etc. macros, you556 * can use this attribute. There is no difference from the viewpoint557 * of functionality with/without 'rel' but the encoding is a bit558 * different. This is expected to be used with user-space event,559 * there is no reason that the kernel event use this, but only for560 * testing.561 */562 563TRACE_EVENT(foo_rel_loc,564 565 TP_PROTO(const char *foo, int bar, unsigned long *mask, const cpumask_t *cpus),566 567 TP_ARGS(foo, bar, mask, cpus),568 569 TP_STRUCT__entry(570 __rel_string( foo, foo )571 __field( int, bar )572 __rel_bitmask( bitmask,573 BITS_PER_BYTE * sizeof(unsigned long) )574 __rel_cpumask( cpumask )575 ),576 577 TP_fast_assign(578 __assign_rel_str(foo);579 __entry->bar = bar;580 __assign_rel_bitmask(bitmask, mask,581 BITS_PER_BYTE * sizeof(unsigned long));582 __assign_rel_cpumask(cpumask, cpus);583 ),584 585 TP_printk("foo_rel_loc %s, %d, %s, %s", __get_rel_str(foo), __entry->bar,586 __get_rel_bitmask(bitmask),587 __get_rel_cpumask(cpumask))588);589#endif590 591/***** NOTICE! The #if protection ends here. *****/592 593 594/*595 * There are several ways I could have done this. If I left out the596 * TRACE_INCLUDE_PATH, then it would default to the kernel source597 * include/trace/events directory.598 *599 * I could specify a path from the define_trace.h file back to this600 * file.601 *602 * #define TRACE_INCLUDE_PATH ../../samples/trace_events603 *604 * But the safest and easiest way to simply make it use the directory605 * that the file is in is to add in the Makefile:606 *607 * CFLAGS_trace-events-sample.o := -I$(src)608 *609 * This will make sure the current path is part of the include610 * structure for our file so that define_trace.h can find it.611 *612 * I could have made only the top level directory the include:613 *614 * CFLAGS_trace-events-sample.o := -I$(PWD)615 *616 * And then let the path to this directory be the TRACE_INCLUDE_PATH:617 *618 * #define TRACE_INCLUDE_PATH samples/trace_events619 *620 * But then if something defines "samples" or "trace_events" as a macro621 * then we could risk that being converted too, and give us an unexpected622 * result.623 */624#undef TRACE_INCLUDE_PATH625#undef TRACE_INCLUDE_FILE626#define TRACE_INCLUDE_PATH .627/*628 * TRACE_INCLUDE_FILE is not needed if the filename and TRACE_SYSTEM are equal629 */630#define TRACE_INCLUDE_FILE trace-events-sample631#include <trace/define_trace.h>632