diff options
Diffstat (limited to 'samples/trace_events')
| -rw-r--r-- | samples/trace_events/Makefile | 17 | ||||
| -rw-r--r-- | samples/trace_events/trace-events-sample.c | 153 | ||||
| -rw-r--r-- | samples/trace_events/trace-events-sample.h | 608 | ||||
| -rw-r--r-- | samples/trace_events/trace_custom_sched.c | 60 | ||||
| -rw-r--r-- | samples/trace_events/trace_custom_sched.h | 96 |
5 files changed, 934 insertions, 0 deletions
diff --git a/samples/trace_events/Makefile b/samples/trace_events/Makefile new file mode 100644 index 000000000..b3808bb4c --- /dev/null +++ b/samples/trace_events/Makefile @@ -0,0 +1,17 @@ +# SPDX-License-Identifier: GPL-2.0-only +# builds the trace events example kernel modules; +# then to use one (as root): insmod <module_name.ko> + +# If you include a trace header outside of include/trace/events +# then the file that does the #define CREATE_TRACE_POINTS must +# have that tracer file in its main search path. This is because +# define_trace.h will include it, and must be able to find it from +# the include/trace directory. +# +# Here trace-events-sample.c does the CREATE_TRACE_POINTS. +# +CFLAGS_trace-events-sample.o := -I$(src) +CFLAGS_trace_custom_sched.o := -I$(src) + +obj-$(CONFIG_SAMPLE_TRACE_EVENTS) += trace-events-sample.o +obj-$(CONFIG_SAMPLE_TRACE_CUSTOM_EVENTS) += trace_custom_sched.o diff --git a/samples/trace_events/trace-events-sample.c b/samples/trace_events/trace-events-sample.c new file mode 100644 index 000000000..608c4ae3b --- /dev/null +++ b/samples/trace_events/trace-events-sample.c @@ -0,0 +1,153 @@ +// SPDX-License-Identifier: GPL-2.0-only +#include <linux/module.h> +#include <linux/kthread.h> + +/* + * Any file that uses trace points, must include the header. + * But only one file, must include the header by defining + * CREATE_TRACE_POINTS first. This will make the C code that + * creates the handles for the trace points. + */ +#define CREATE_TRACE_POINTS +#include "trace-events-sample.h" + +static const char *random_strings[] = { + "Mother Goose", + "Snoopy", + "Gandalf", + "Frodo", + "One ring to rule them all" +}; + +static void do_simple_thread_func(int cnt, const char *fmt, ...) +{ + unsigned long bitmask[1] = {0xdeadbeefUL}; + va_list va; + int array[6]; + int len = cnt % 5; + int i; + + set_current_state(TASK_INTERRUPTIBLE); + schedule_timeout(HZ); + + for (i = 0; i < len; i++) + array[i] = i + 1; + array[i] = 0; + + va_start(va, fmt); + + /* Silly tracepoints */ + trace_foo_bar("hello", cnt, array, random_strings[len], + current->cpus_ptr, fmt, &va); + + va_end(va); + + trace_foo_with_template_simple("HELLO", cnt); + + trace_foo_bar_with_cond("Some times print", cnt); + + trace_foo_with_template_cond("prints other times", cnt); + + trace_foo_with_template_print("I have to be different", cnt); + + trace_foo_rel_loc("Hello __rel_loc", cnt, bitmask); +} + +static void simple_thread_func(int cnt) +{ + do_simple_thread_func(cnt, "iter=%d", cnt); +} + +static int simple_thread(void *arg) +{ + int cnt = 0; + + while (!kthread_should_stop()) + simple_thread_func(cnt++); + + return 0; +} + +static struct task_struct *simple_tsk; +static struct task_struct *simple_tsk_fn; + +static void simple_thread_func_fn(int cnt) +{ + set_current_state(TASK_INTERRUPTIBLE); + schedule_timeout(HZ); + + /* More silly tracepoints */ + trace_foo_bar_with_fn("Look at me", cnt); + trace_foo_with_template_fn("Look at me too", cnt); +} + +static int simple_thread_fn(void *arg) +{ + int cnt = 0; + + while (!kthread_should_stop()) + simple_thread_func_fn(cnt++); + + return 0; +} + +static DEFINE_MUTEX(thread_mutex); +static int simple_thread_cnt; + +int foo_bar_reg(void) +{ + mutex_lock(&thread_mutex); + if (simple_thread_cnt++) + goto out; + + pr_info("Starting thread for foo_bar_fn\n"); + /* + * We shouldn't be able to start a trace when the module is + * unloading (there's other locks to prevent that). But + * for consistency sake, we still take the thread_mutex. + */ + simple_tsk_fn = kthread_run(simple_thread_fn, NULL, "event-sample-fn"); + out: + mutex_unlock(&thread_mutex); + return 0; +} + +void foo_bar_unreg(void) +{ + mutex_lock(&thread_mutex); + if (--simple_thread_cnt) + goto out; + + pr_info("Killing thread for foo_bar_fn\n"); + if (simple_tsk_fn) + kthread_stop(simple_tsk_fn); + simple_tsk_fn = NULL; + out: + mutex_unlock(&thread_mutex); +} + +static int __init trace_event_init(void) +{ + simple_tsk = kthread_run(simple_thread, NULL, "event-sample"); + if (IS_ERR(simple_tsk)) + return -1; + + return 0; +} + +static void __exit trace_event_exit(void) +{ + kthread_stop(simple_tsk); + mutex_lock(&thread_mutex); + if (simple_tsk_fn) + kthread_stop(simple_tsk_fn); + simple_tsk_fn = NULL; + mutex_unlock(&thread_mutex); +} + +module_init(trace_event_init); +module_exit(trace_event_exit); + +MODULE_AUTHOR("Steven Rostedt"); +MODULE_DESCRIPTION("trace-events-sample"); +MODULE_LICENSE("GPL"); diff --git a/samples/trace_events/trace-events-sample.h b/samples/trace_events/trace-events-sample.h new file mode 100644 index 000000000..1a9222620 --- /dev/null +++ b/samples/trace_events/trace-events-sample.h @@ -0,0 +1,608 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * If TRACE_SYSTEM is defined, that will be the directory created + * in the ftrace directory under /sys/kernel/tracing/events/<system> + * + * The define_trace.h below will also look for a file name of + * TRACE_SYSTEM.h where TRACE_SYSTEM is what is defined here. + * In this case, it would look for sample-trace.h + * + * If the header name will be different than the system name + * (as in this case), then you can override the header name that + * define_trace.h will look up by defining TRACE_INCLUDE_FILE + * + * This file is called trace-events-sample.h but we want the system + * to be called "sample-trace". Therefore we must define the name of this + * file: + * + * #define TRACE_INCLUDE_FILE trace-events-sample + * + * As we do an the bottom of this file. + * + * Notice that TRACE_SYSTEM should be defined outside of #if + * protection, just like TRACE_INCLUDE_FILE. + */ +#undef TRACE_SYSTEM +#define TRACE_SYSTEM sample-trace + +/* + * TRACE_SYSTEM is expected to be a C valid variable (alpha-numeric + * and underscore), although it may start with numbers. If for some + * reason it is not, you need to add the following lines: + */ +#undef TRACE_SYSTEM_VAR +#define TRACE_SYSTEM_VAR sample_trace +/* + * But the above is only needed if TRACE_SYSTEM is not alpha-numeric + * and underscored. By default, TRACE_SYSTEM_VAR will be equal to + * TRACE_SYSTEM. As TRACE_SYSTEM_VAR must be alpha-numeric, if + * TRACE_SYSTEM is not, then TRACE_SYSTEM_VAR must be defined with + * only alpha-numeric and underscores. + * + * The TRACE_SYSTEM_VAR is only used internally and not visible to + * user space. + */ + +/* + * Notice that this file is not protected like a normal header. + * We also must allow for rereading of this file. The + * + * || defined(TRACE_HEADER_MULTI_READ) + * + * serves this purpose. + */ +#if !defined(_TRACE_EVENT_SAMPLE_H) || defined(TRACE_HEADER_MULTI_READ) +#define _TRACE_EVENT_SAMPLE_H + +/* + * All trace headers should include tracepoint.h, until we finally + * make it into a standard header. + */ +#include <linux/tracepoint.h> + +/* + * The TRACE_EVENT macro is broken up into 5 parts. + * + * name: name of the trace point. This is also how to enable the tracepoint. + * A function called trace_foo_bar() will be created. + * + * proto: the prototype of the function trace_foo_bar() + * Here it is trace_foo_bar(char *foo, int bar). + * + * args: must match the arguments in the prototype. + * Here it is simply "foo, bar". + * + * struct: This defines the way the data will be stored in the ring buffer. + * The items declared here become part of a special structure + * called "__entry", which can be used in the fast_assign part of the + * TRACE_EVENT macro. + * + * Here are the currently defined types you can use: + * + * __field : Is broken up into type and name. Where type can be any + * primitive type (integer, long or pointer). + * + * __field(int, foo) + * + * __entry->foo = 5; + * + * __field_struct : This can be any static complex data type (struct, union + * but not an array). Be careful using complex types, as each + * event is limited in size, and copying large amounts of data + * into the ring buffer can slow things down. + * + * __field_struct(struct bar, foo) + * + * __entry->bar.x = y; + + * __array: There are three fields (type, name, size). The type is the + * type of elements in the array, the name is the name of the array. + * size is the number of items in the array (not the total size). + * + * __array( char, foo, 10) is the same as saying: char foo[10]; + * + * Assigning arrays can be done like any array: + * + * __entry->foo[0] = 'a'; + * + * memcpy(__entry->foo, bar, 10); + * + * __dynamic_array: This is similar to array, but can vary its size from + * instance to instance of the tracepoint being called. + * Like __array, this too has three elements (type, name, size); + * type is the type of the element, name is the name of the array. + * The size is different than __array. It is not a static number, + * but the algorithm to figure out the length of the array for the + * specific instance of tracepoint. Again, size is the number of + * items in the array, not the total length in bytes. + * + * __dynamic_array( int, foo, bar) is similar to: int foo[bar]; + * + * Note, unlike arrays, you must use the __get_dynamic_array() macro + * to access the array. + * + * memcpy(__get_dynamic_array(foo), bar, 10); + * + * Notice, that "__entry" is not needed here. + * + * __string: This is a special kind of __dynamic_array. It expects to + * have a null terminated character array passed to it (it allows + * for NULL too, which would be converted into "(null)"). __string + * takes two parameter (name, src), where name is the name of + * the string saved, and src is the string to copy into the + * ring buffer. + * + * __string(foo, bar) is similar to: strcpy(foo, bar) + * + * To assign a string, use the helper macro __assign_str(). + * + * __assign_str(foo, bar); + * + * In most cases, the __assign_str() macro will take the same + * parameters as the __string() macro had to declare the string. + * + * __vstring: This is similar to __string() but instead of taking a + * dynamic length, it takes a variable list va_list 'va' variable. + * Some event callers already have a message from parameters saved + * in a va_list. Passing in the format and the va_list variable + * will save just enough on the ring buffer for that string. + * Note, the va variable used is a pointer to a va_list, not + * to the va_list directly. + * + * (va_list *va) + * + * __vstring(foo, fmt, va) is similar to: vsnprintf(foo, fmt, va) + * + * To assign the string, use the helper macro __assign_vstr(). + * + * __assign_vstr(foo, fmt, va); + * + * In most cases, the __assign_vstr() macro will take the same + * parameters as the __vstring() macro had to declare the string. + * Use __get_str() to retrieve the __vstring() just like it would for + * __string(). + * + * __string_len: This is a helper to a __dynamic_array, but it understands + * that the array has characters in it, and with the combined + * use of __assign_str_len(), it will allocate 'len' + 1 bytes + * in the ring buffer and add a '\0' to the string. This is + * useful if the string being saved has no terminating '\0' byte. + * It requires that the length of the string is known as it acts + * like a memcpy(). + * + * Declared with: + * + * __string_len(foo, bar, len) + * + * To assign this string, use the helper macro __assign_str_len(). + * + * __assign_str_len(foo, bar, len); + * + * Then len + 1 is allocated to the ring buffer, and a nul terminating + * byte is added. This is similar to: + * + * memcpy(__get_str(foo), bar, len); + * __get_str(foo)[len] = 0; + * + * The advantage of using this over __dynamic_array, is that it + * takes care of allocating the extra byte on the ring buffer + * for the '\0' terminating byte, and __get_str(foo) can be used + * in the TP_printk(). + * + * __bitmask: This is another kind of __dynamic_array, but it expects + * an array of longs, and the number of bits to parse. It takes + * two parameters (name, nr_bits), where name is the name of the + * bitmask to save, and the nr_bits is the number of bits to record. + * + * __bitmask(target_cpu, nr_cpumask_bits) + * + * To assign a bitmask, use the __assign_bitmask() helper macro. + * + * __assign_bitmask(target_cpus, cpumask_bits(bar), nr_cpumask_bits); + * + * + * fast_assign: This is a C like function that is used to store the items + * into the ring buffer. A special variable called "__entry" will be the + * structure that points into the ring buffer and has the same fields as + * described by the struct part of TRACE_EVENT above. + * + * printk: This is a way to print out the data in pretty print. This is + * useful if the system crashes and you are logging via a serial line, + * the data can be printed to the console using this "printk" method. + * This is also used to print out the data from the trace files. + * Again, the __entry macro is used to access the data from the ring buffer. + * + * Note, __dynamic_array, __string, and __bitmask require special helpers + * to access the data. + * + * For __dynamic_array(int, foo, bar) use __get_dynamic_array(foo) + * Use __get_dynamic_array_len(foo) to get the length of the array + * saved. Note, __get_dynamic_array_len() returns the total allocated + * length of the dynamic array; __print_array() expects the second + * parameter to be the number of elements. To get that, the array length + * needs to be divided by the element size. + * + * For __string(foo, bar) use __get_str(foo) + * + * For __bitmask(target_cpus, nr_cpumask_bits) use __get_bitmask(target_cpus) + * + * + * Note, that for both the assign and the printk, __entry is the handler + * to the data structure in the ring buffer, and is defined by the + * TP_STRUCT__entry. + */ + +/* + * It is OK to have helper functions in the file, but they need to be protected + * from being defined more than once. Remember, this file gets included more + * than once. + */ +#ifndef __TRACE_EVENT_SAMPLE_HELPER_FUNCTIONS +#define __TRACE_EVENT_SAMPLE_HELPER_FUNCTIONS +static inline int __length_of(const int *list) +{ + int i; + + if (!list) + return 0; + + for (i = 0; list[i]; i++) + ; + return i; +} + +enum { + TRACE_SAMPLE_FOO = 2, + TRACE_SAMPLE_BAR = 4, + TRACE_SAMPLE_ZOO = 8, +}; +#endif + +/* + * If enums are used in the TP_printk(), their names will be shown in + * format files and not their values. This can cause problems with user + * space programs that parse the format files to know how to translate + * the raw binary trace output into human readable text. + * + * To help out user space programs, any enum that is used in the TP_printk() + * should be defined by TRACE_DEFINE_ENUM() macro. All that is needed to + * be done is to add this macro with the enum within it in the trace + * header file, and it will be converted in the output. + */ + +TRACE_DEFINE_ENUM(TRACE_SAMPLE_FOO); +TRACE_DEFINE_ENUM(TRACE_SAMPLE_BAR); +TRACE_DEFINE_ENUM(TRACE_SAMPLE_ZOO); + +TRACE_EVENT(foo_bar, + + TP_PROTO(const char *foo, int bar, const int *lst, + const char *string, const struct cpumask *mask, + const char *fmt, va_list *va), + + TP_ARGS(foo, bar, lst, string, mask, fmt, va), + + TP_STRUCT__entry( + __array( char, foo, 10 ) + __field( int, bar ) + __dynamic_array(int, list, __length_of(lst)) + __string( str, string ) + __bitmask( cpus, num_possible_cpus() ) + __vstring( vstr, fmt, va ) + ), + + TP_fast_assign( + strlcpy(__entry->foo, foo, 10); + __entry->bar = bar; + memcpy(__get_dynamic_array(list), lst, + __length_of(lst) * sizeof(int)); + __assign_str(str, string); + __assign_vstr(vstr, fmt, va); + __assign_bitmask(cpus, cpumask_bits(mask), num_possible_cpus()); + ), + + TP_printk("foo %s %d %s %s %s %s (%s) %s", __entry->foo, __entry->bar, + +/* + * Notice here the use of some helper functions. This includes: + * + * __print_symbolic( variable, { value, "string" }, ... ), + * + * The variable is tested against each value of the { } pair. If + * the variable matches one of the values, then it will print the + * string in that pair. If non are matched, it returns a string + * version of the number (if __entry->bar == 7 then "7" is returned). + */ + __print_symbolic(__entry->bar, + { 0, "zero" }, + { TRACE_SAMPLE_FOO, "TWO" }, + { TRACE_SAMPLE_BAR, "FOUR" }, + { TRACE_SAMPLE_ZOO, "EIGHT" }, + { 10, "TEN" } + ), + +/* + * __print_flags( variable, "delim", { value, "flag" }, ... ), + * + * This is similar to __print_symbolic, except that it tests the bits + * of the value. If ((FLAG & variable) == FLAG) then the string is + * printed. If more than one flag matches, then each one that does is + * also printed with delim in between them. + * If not all bits are accounted for, then the not found bits will be + * added in hex format: 0x506 will show BIT2|BIT4|0x500 + */ + __print_flags(__entry->bar, "|", + { 1, "BIT1" }, + { 2, "BIT2" }, + { 4, "BIT3" }, + { 8, "BIT4" } + ), +/* + * __print_array( array, len, element_size ) + * + * This prints out the array that is defined by __array in a nice format. + */ + __print_array(__get_dynamic_array(list), + __get_dynamic_array_len(list) / sizeof(int), + sizeof(int)), + __get_str(str), __get_bitmask(cpus), __get_str(vstr)) +); + +/* + * There may be a case where a tracepoint should only be called if + * some condition is set. Otherwise the tracepoint should not be called. + * But to do something like: + * + * if (cond) + * trace_foo(); + * + * Would cause a little overhead when tracing is not enabled, and that + * overhead, even if small, is not something we want. As tracepoints + * use static branch (aka jump_labels), where no branch is taken to + * skip the tracepoint when not enabled, and a jmp is placed to jump + * to the tracepoint code when it is enabled, having a if statement + * nullifies that optimization. It would be nice to place that + * condition within the static branch. This is where TRACE_EVENT_CONDITION + * comes in. + * + * TRACE_EVENT_CONDITION() is just like TRACE_EVENT, except it adds another + * parameter just after args. Where TRACE_EVENT has: + * + * TRACE_EVENT(name, proto, args, struct, assign, printk) + * + * the CONDITION version has: + * + * TRACE_EVENT_CONDITION(name, proto, args, cond, struct, assign, printk) + * + * Everything is the same as TRACE_EVENT except for the new cond. Think + * of the cond variable as: + * + * if (cond) + * trace_foo_bar_with_cond(); + * + * Except that the logic for the if branch is placed after the static branch. + * That is, the if statement that processes the condition will not be + * executed unless that traecpoint is enabled. Otherwise it still remains + * a nop. + */ +TRACE_EVENT_CONDITION(foo_bar_with_cond, + + TP_PROTO(const char *foo, int bar), + + TP_ARGS(foo, bar), + + TP_CONDITION(!(bar % 10)), + + TP_STRUCT__entry( + __string( foo, foo ) + __field( int, bar ) + ), + + TP_fast_assign( + __assign_str(foo, foo); + __entry->bar = bar; + ), + + TP_printk("foo %s %d", __get_str(foo), __entry->bar) +); + +int foo_bar_reg(void); +void foo_bar_unreg(void); + +/* + * Now in the case that some function needs to be called when the + * tracepoint is enabled and/or when it is disabled, the + * TRACE_EVENT_FN() serves this purpose. This is just like TRACE_EVENT() + * but adds two more parameters at the end: + * + * TRACE_EVENT_FN( name, proto, args, struct, assign, printk, reg, unreg) + * + * reg and unreg are functions with the prototype of: + * + * void reg(void) + * + * The reg function gets called before the tracepoint is enabled, and + * the unreg function gets called after the tracepoint is disabled. + * + * Note, reg and unreg are allowed to be NULL. If you only need to + * call a function before enabling, or after disabling, just set one + * function and pass in NULL for the other parameter. + */ +TRACE_EVENT_FN(foo_bar_with_fn, + + TP_PROTO(const char *foo, int bar), + + TP_ARGS(foo, bar), + + TP_STRUCT__entry( + __string( foo, foo ) + __field( int, bar ) + ), + + TP_fast_assign( + __assign_str(foo, foo); + __entry->bar = bar; + ), + + TP_printk("foo %s %d", __get_str(foo), __entry->bar), + + foo_bar_reg, foo_bar_unreg +); + +/* + * Each TRACE_EVENT macro creates several helper functions to produce + * the code to add the tracepoint, create the files in the trace + * directory, hook it to perf, assign the values and to print out + * the raw data from the ring buffer. To prevent too much bloat, + * if there are more than one tracepoint that uses the same format + * for the proto, args, struct, assign and printk, and only the name + * is different, it is highly recommended to use the DECLARE_EVENT_CLASS + * + * DECLARE_EVENT_CLASS() macro creates most of the functions for the + * tracepoint. Then DEFINE_EVENT() is use to hook a tracepoint to those + * functions. This DEFINE_EVENT() is an instance of the class and can + * be enabled and disabled separately from other events (either TRACE_EVENT + * or other DEFINE_EVENT()s). + * + * Note, TRACE_EVENT() itself is simply defined as: + * + * #define TRACE_EVENT(name, proto, args, tstruct, assign, printk) \ + * DECLARE_EVENT_CLASS(name, proto, args, tstruct, assign, printk); \ + * DEFINE_EVENT(name, name, proto, args) + * + * The DEFINE_EVENT() also can be declared with conditions and reg functions: + * + * DEFINE_EVENT_CONDITION(template, name, proto, args, cond); + * DEFINE_EVENT_FN(template, name, proto, args, reg, unreg); + */ +DECLARE_EVENT_CLASS(foo_template, + + TP_PROTO(const char *foo, int bar), + + TP_ARGS(foo, bar), + + TP_STRUCT__entry( + __string( foo, foo ) + __field( int, bar ) + ), + + TP_fast_assign( + __assign_str(foo, foo); + __entry->bar = bar; + ), + + TP_printk("foo %s %d", __get_str(foo), __entry->bar) +); + +/* + * Here's a better way for the previous samples (except, the first + * example had more fields and could not be used here). + */ +DEFINE_EVENT(foo_template, foo_with_template_simple, + TP_PROTO(const char *foo, int bar), + TP_ARGS(foo, bar)); + +DEFINE_EVENT_CONDITION(foo_template, foo_with_template_cond, + TP_PROTO(const char *foo, int bar), + TP_ARGS(foo, bar), + TP_CONDITION(!(bar % 8))); + + +DEFINE_EVENT_FN(foo_template, foo_with_template_fn, + TP_PROTO(const char *foo, int bar), + TP_ARGS(foo, bar), + foo_bar_reg, foo_bar_unreg); + +/* + * Anytime two events share basically the same values and have + * the same output, use the DECLARE_EVENT_CLASS() and DEFINE_EVENT() + * when ever possible. + */ + +/* + * If the event is similar to the DECLARE_EVENT_CLASS, but you need + * to have a different output, then use DEFINE_EVENT_PRINT() which + * lets you override the TP_printk() of the class. + */ + +DEFINE_EVENT_PRINT(foo_template, foo_with_template_print, + TP_PROTO(const char *foo, int bar), + TP_ARGS(foo, bar), + TP_printk("bar %s %d", __get_str(foo), __entry->bar)); + +/* + * There are yet another __rel_loc dynamic data attribute. If you + * use __rel_dynamic_array() and __rel_string() etc. macros, you + * can use this attribute. There is no difference from the viewpoint + * of functionality with/without 'rel' but the encoding is a bit + * different. This is expected to be used with user-space event, + * there is no reason that the kernel event use this, but only for + * testing. + */ + +TRACE_EVENT(foo_rel_loc, + + TP_PROTO(const char *foo, int bar, unsigned long *mask), + + TP_ARGS(foo, bar, mask), + + TP_STRUCT__entry( + __rel_string( foo, foo ) + __field( int, bar ) + __rel_bitmask( bitmask, + BITS_PER_BYTE * sizeof(unsigned long) ) + ), + + TP_fast_assign( + __assign_rel_str(foo, foo); + __entry->bar = bar; + __assign_rel_bitmask(bitmask, mask, + BITS_PER_BYTE * sizeof(unsigned long)); + ), + + TP_printk("foo_rel_loc %s, %d, %s", __get_rel_str(foo), __entry->bar, + __get_rel_bitmask(bitmask)) +); +#endif + +/***** NOTICE! The #if protection ends here. *****/ + + +/* + * There are several ways I could have done this. If I left out the + * TRACE_INCLUDE_PATH, then it would default to the kernel source + * include/trace/events directory. + * + * I could specify a path from the define_trace.h file back to this + * file. + * + * #define TRACE_INCLUDE_PATH ../../samples/trace_events + * + * But the safest and easiest way to simply make it use the directory + * that the file is in is to add in the Makefile: + * + * CFLAGS_trace-events-sample.o := -I$(src) + * + * This will make sure the current path is part of the include + * structure for our file so that define_trace.h can find it. + * + * I could have made only the top level directory the include: + * + * CFLAGS_trace-events-sample.o := -I$(PWD) + * + * And then let the path to this directory be the TRACE_INCLUDE_PATH: + * + * #define TRACE_INCLUDE_PATH samples/trace_events + * + * But then if something defines "samples" or "trace_events" as a macro + * then we could risk that being converted too, and give us an unexpected + * result. + */ +#undef TRACE_INCLUDE_PATH +#undef TRACE_INCLUDE_FILE +#define TRACE_INCLUDE_PATH . +/* + * TRACE_INCLUDE_FILE is not needed if the filename and TRACE_SYSTEM are equal + */ +#define TRACE_INCLUDE_FILE trace-events-sample +#include <trace/define_trace.h> diff --git a/samples/trace_events/trace_custom_sched.c b/samples/trace_events/trace_custom_sched.c new file mode 100644 index 000000000..b99d9ab7d --- /dev/null +++ b/samples/trace_events/trace_custom_sched.c @@ -0,0 +1,60 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * event tracer + * + * Copyright (C) 2022 Google Inc, Steven Rostedt <rostedt@goodmis.org> + */ + +#define pr_fmt(fmt) fmt + +#include <linux/trace_events.h> +#include <linux/version.h> +#include <linux/module.h> +#include <linux/sched.h> + +/* + * Must include the event header that the custom event will attach to, + * from the C file, and not in the custom header file. + */ +#include <trace/events/sched.h> + +/* Declare CREATE_CUSTOM_TRACE_EVENTS before including custom header */ +#define CREATE_CUSTOM_TRACE_EVENTS + +#include "trace_custom_sched.h" + +/* + * As the trace events are not exported to modules, the use of + * for_each_kernel_tracepoint() is needed to find the trace event + * to attach to. The fct() function below, is a callback that + * will be called for every event. + * + * Helper functions are created by the TRACE_CUSTOM_EVENT() macro + * update the event. Those are of the form: + * + * trace_custom_event_<event>_update() + * + * Where <event> is the event to attach. + */ +static void fct(struct tracepoint *tp, void *priv) +{ + trace_custom_event_sched_switch_update(tp); + trace_custom_event_sched_waking_update(tp); +} + +static int __init trace_sched_init(void) +{ + for_each_kernel_tracepoint(fct, NULL); + return 0; +} + +static void __exit trace_sched_exit(void) +{ +} + +module_init(trace_sched_init); +module_exit(trace_sched_exit); + +MODULE_AUTHOR("Steven Rostedt"); +MODULE_DESCRIPTION("Custom scheduling events"); +MODULE_LICENSE("GPL"); diff --git a/samples/trace_events/trace_custom_sched.h b/samples/trace_events/trace_custom_sched.h new file mode 100644 index 000000000..951388334 --- /dev/null +++ b/samples/trace_events/trace_custom_sched.h @@ -0,0 +1,96 @@ +/* SPDX-License-Identifier: GPL-2.0 */ + +/* + * Like the headers that use TRACE_EVENT(), the TRACE_CUSTOM_EVENT() + * needs a header that allows for multiple inclusions. + * + * Test for a unique name (here we have _TRACE_CUSTOM_SCHED_H), + * also allowing to continue if TRACE_CUSTOM_MULTI_READ is defined. + */ +#if !defined(_TRACE_CUSTOM_SCHED_H) || defined(TRACE_CUSTOM_MULTI_READ) +#define _TRACE_CUSTOM_SCHED_H + +/* Include linux/trace_events.h for initial defines of TRACE_CUSTOM_EVENT() */ +#include <linux/trace_events.h> + +/* + * TRACE_CUSTOM_EVENT() is just like TRACE_EVENT(). The first parameter + * is the event name of an existing event where the TRACE_EVENT has been included + * in the C file before including this file. + */ +TRACE_CUSTOM_EVENT(sched_switch, + + /* + * The TP_PROTO() and TP_ARGS must match the trace event + * that the custom event is using. + */ + TP_PROTO(bool preempt, + struct task_struct *prev, + struct task_struct *next, + unsigned int prev_state), + + TP_ARGS(preempt, prev, next, prev_state), + + /* + * The next fields are where the customization happens. + * The TP_STRUCT__entry() defines what will be recorded + * in the ring buffer when the custom event triggers. + * + * The rest is just like the TRACE_EVENT() macro except that + * it uses the custom entry. + */ + TP_STRUCT__entry( + __field( unsigned short, prev_prio ) + __field( unsigned short, next_prio ) + __field( pid_t, next_pid ) + ), + + TP_fast_assign( + __entry->prev_prio = prev->prio; + __entry->next_pid = next->pid; + __entry->next_prio = next->prio; + ), + + TP_printk("prev_prio=%d next_pid=%d next_prio=%d", + __entry->prev_prio, __entry->next_pid, __entry->next_prio) +) + + +TRACE_CUSTOM_EVENT(sched_waking, + + TP_PROTO(struct task_struct *p), + + TP_ARGS(p), + + TP_STRUCT__entry( + __field( pid_t, pid ) + __field( unsigned short, prio ) + ), + + TP_fast_assign( + __entry->pid = p->pid; + __entry->prio = p->prio; + ), + + TP_printk("pid=%d prio=%d", __entry->pid, __entry->prio) +) +#endif +/* + * Just like the headers that create TRACE_EVENTs, the below must + * be outside the protection of the above #if block. + */ + +/* + * It is required that the Makefile includes: + * CFLAGS_<c_file>.o := -I$(src) + */ +#undef TRACE_INCLUDE_PATH +#undef TRACE_INCLUDE_FILE +#define TRACE_INCLUDE_PATH . + +/* + * It is requred that the TRACE_INCLUDE_FILE be the same + * as this file without the ".h". + */ +#define TRACE_INCLUDE_FILE trace_custom_sched +#include <trace/define_custom_trace.h> |