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524 lines
17 KiB
524 lines
17 KiB
/* SPDX-License-Identifier: GPL-2.0 */ |
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/* |
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* If TRACE_SYSTEM is defined, that will be the directory created |
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* in the ftrace directory under /sys/kernel/tracing/events/<system> |
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* |
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* The define_trace.h below will also look for a file name of |
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* TRACE_SYSTEM.h where TRACE_SYSTEM is what is defined here. |
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* In this case, it would look for sample-trace.h |
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* |
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* If the header name will be different than the system name |
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* (as in this case), then you can override the header name that |
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* define_trace.h will look up by defining TRACE_INCLUDE_FILE |
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* |
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* This file is called trace-events-sample.h but we want the system |
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* to be called "sample-trace". Therefore we must define the name of this |
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* file: |
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* |
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* #define TRACE_INCLUDE_FILE trace-events-sample |
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* |
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* As we do an the bottom of this file. |
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* |
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* Notice that TRACE_SYSTEM should be defined outside of #if |
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* protection, just like TRACE_INCLUDE_FILE. |
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*/ |
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#undef TRACE_SYSTEM |
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#define TRACE_SYSTEM sample-trace |
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/* |
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* TRACE_SYSTEM is expected to be a C valid variable (alpha-numeric |
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* and underscore), although it may start with numbers. If for some |
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* reason it is not, you need to add the following lines: |
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*/ |
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#undef TRACE_SYSTEM_VAR |
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#define TRACE_SYSTEM_VAR sample_trace |
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/* |
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* But the above is only needed if TRACE_SYSTEM is not alpha-numeric |
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* and underscored. By default, TRACE_SYSTEM_VAR will be equal to |
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* TRACE_SYSTEM. As TRACE_SYSTEM_VAR must be alpha-numeric, if |
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* TRACE_SYSTEM is not, then TRACE_SYSTEM_VAR must be defined with |
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* only alpha-numeric and underscores. |
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* |
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* The TRACE_SYSTEM_VAR is only used internally and not visible to |
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* user space. |
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*/ |
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/* |
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* Notice that this file is not protected like a normal header. |
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* We also must allow for rereading of this file. The |
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* |
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* || defined(TRACE_HEADER_MULTI_READ) |
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* |
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* serves this purpose. |
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*/ |
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#if !defined(_TRACE_EVENT_SAMPLE_H) || defined(TRACE_HEADER_MULTI_READ) |
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#define _TRACE_EVENT_SAMPLE_H |
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/* |
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* All trace headers should include tracepoint.h, until we finally |
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* make it into a standard header. |
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*/ |
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#include <linux/tracepoint.h> |
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|
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/* |
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* The TRACE_EVENT macro is broken up into 5 parts. |
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* |
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* name: name of the trace point. This is also how to enable the tracepoint. |
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* A function called trace_foo_bar() will be created. |
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* |
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* proto: the prototype of the function trace_foo_bar() |
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* Here it is trace_foo_bar(char *foo, int bar). |
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* |
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* args: must match the arguments in the prototype. |
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* Here it is simply "foo, bar". |
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* |
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* struct: This defines the way the data will be stored in the ring buffer. |
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* The items declared here become part of a special structure |
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* called "__entry", which can be used in the fast_assign part of the |
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* TRACE_EVENT macro. |
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* |
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* Here are the currently defined types you can use: |
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* |
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* __field : Is broken up into type and name. Where type can be any |
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* primitive type (integer, long or pointer). |
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* |
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* __field(int, foo) |
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* |
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* __entry->foo = 5; |
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* |
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* __field_struct : This can be any static complex data type (struct, union |
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* but not an array). Be careful using complex types, as each |
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* event is limited in size, and copying large amounts of data |
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* into the ring buffer can slow things down. |
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* |
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* __field_struct(struct bar, foo) |
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* |
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* __entry->bar.x = y; |
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* __array: There are three fields (type, name, size). The type is the |
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* type of elements in the array, the name is the name of the array. |
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* size is the number of items in the array (not the total size). |
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* |
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* __array( char, foo, 10) is the same as saying: char foo[10]; |
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* |
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* Assigning arrays can be done like any array: |
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* |
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* __entry->foo[0] = 'a'; |
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* |
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* memcpy(__entry->foo, bar, 10); |
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* |
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* __dynamic_array: This is similar to array, but can vary its size from |
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* instance to instance of the tracepoint being called. |
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* Like __array, this too has three elements (type, name, size); |
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* type is the type of the element, name is the name of the array. |
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* The size is different than __array. It is not a static number, |
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* but the algorithm to figure out the length of the array for the |
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* specific instance of tracepoint. Again, size is the number of |
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* items in the array, not the total length in bytes. |
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* |
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* __dynamic_array( int, foo, bar) is similar to: int foo[bar]; |
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* |
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* Note, unlike arrays, you must use the __get_dynamic_array() macro |
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* to access the array. |
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* |
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* memcpy(__get_dynamic_array(foo), bar, 10); |
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* |
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* Notice, that "__entry" is not needed here. |
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* |
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* __string: This is a special kind of __dynamic_array. It expects to |
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* have a null terminated character array passed to it (it allows |
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* for NULL too, which would be converted into "(null)"). __string |
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* takes two parameter (name, src), where name is the name of |
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* the string saved, and src is the string to copy into the |
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* ring buffer. |
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* |
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* __string(foo, bar) is similar to: strcpy(foo, bar) |
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* |
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* To assign a string, use the helper macro __assign_str(). |
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* |
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* __assign_str(foo, bar); |
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* |
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* In most cases, the __assign_str() macro will take the same |
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* parameters as the __string() macro had to declare the string. |
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* |
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* __bitmask: This is another kind of __dynamic_array, but it expects |
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* an array of longs, and the number of bits to parse. It takes |
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* two parameters (name, nr_bits), where name is the name of the |
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* bitmask to save, and the nr_bits is the number of bits to record. |
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* |
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* __bitmask(target_cpu, nr_cpumask_bits) |
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* |
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* To assign a bitmask, use the __assign_bitmask() helper macro. |
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* |
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* __assign_bitmask(target_cpus, cpumask_bits(bar), nr_cpumask_bits); |
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* |
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* |
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* fast_assign: This is a C like function that is used to store the items |
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* into the ring buffer. A special variable called "__entry" will be the |
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* structure that points into the ring buffer and has the same fields as |
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* described by the struct part of TRACE_EVENT above. |
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* |
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* printk: This is a way to print out the data in pretty print. This is |
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* useful if the system crashes and you are logging via a serial line, |
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* the data can be printed to the console using this "printk" method. |
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* This is also used to print out the data from the trace files. |
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* Again, the __entry macro is used to access the data from the ring buffer. |
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* |
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* Note, __dynamic_array, __string, and __bitmask require special helpers |
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* to access the data. |
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* |
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* For __dynamic_array(int, foo, bar) use __get_dynamic_array(foo) |
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* Use __get_dynamic_array_len(foo) to get the length of the array |
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* saved. Note, __get_dynamic_array_len() returns the total allocated |
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* length of the dynamic array; __print_array() expects the second |
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* parameter to be the number of elements. To get that, the array length |
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* needs to be divided by the element size. |
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* |
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* For __string(foo, bar) use __get_str(foo) |
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* |
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* For __bitmask(target_cpus, nr_cpumask_bits) use __get_bitmask(target_cpus) |
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* |
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* |
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* Note, that for both the assign and the printk, __entry is the handler |
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* to the data structure in the ring buffer, and is defined by the |
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* TP_STRUCT__entry. |
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*/ |
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/* |
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* It is OK to have helper functions in the file, but they need to be protected |
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* from being defined more than once. Remember, this file gets included more |
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* than once. |
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*/ |
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#ifndef __TRACE_EVENT_SAMPLE_HELPER_FUNCTIONS |
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#define __TRACE_EVENT_SAMPLE_HELPER_FUNCTIONS |
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static inline int __length_of(const int *list) |
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{ |
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int i; |
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if (!list) |
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return 0; |
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for (i = 0; list[i]; i++) |
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; |
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return i; |
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} |
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enum { |
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TRACE_SAMPLE_FOO = 2, |
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TRACE_SAMPLE_BAR = 4, |
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TRACE_SAMPLE_ZOO = 8, |
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}; |
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#endif |
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/* |
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* If enums are used in the TP_printk(), their names will be shown in |
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* format files and not their values. This can cause problems with user |
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* space programs that parse the format files to know how to translate |
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* the raw binary trace output into human readable text. |
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* |
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* To help out user space programs, any enum that is used in the TP_printk() |
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* should be defined by TRACE_DEFINE_ENUM() macro. All that is needed to |
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* be done is to add this macro with the enum within it in the trace |
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* header file, and it will be converted in the output. |
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*/ |
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TRACE_DEFINE_ENUM(TRACE_SAMPLE_FOO); |
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TRACE_DEFINE_ENUM(TRACE_SAMPLE_BAR); |
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TRACE_DEFINE_ENUM(TRACE_SAMPLE_ZOO); |
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TRACE_EVENT(foo_bar, |
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TP_PROTO(const char *foo, int bar, const int *lst, |
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const char *string, const struct cpumask *mask), |
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TP_ARGS(foo, bar, lst, string, mask), |
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TP_STRUCT__entry( |
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__array( char, foo, 10 ) |
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__field( int, bar ) |
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__dynamic_array(int, list, __length_of(lst)) |
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__string( str, string ) |
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__bitmask( cpus, num_possible_cpus() ) |
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), |
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TP_fast_assign( |
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strlcpy(__entry->foo, foo, 10); |
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__entry->bar = bar; |
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memcpy(__get_dynamic_array(list), lst, |
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__length_of(lst) * sizeof(int)); |
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__assign_str(str, string); |
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__assign_bitmask(cpus, cpumask_bits(mask), num_possible_cpus()); |
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), |
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TP_printk("foo %s %d %s %s %s %s (%s)", __entry->foo, __entry->bar, |
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/* |
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* Notice here the use of some helper functions. This includes: |
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* |
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* __print_symbolic( variable, { value, "string" }, ... ), |
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* |
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* The variable is tested against each value of the { } pair. If |
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* the variable matches one of the values, then it will print the |
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* string in that pair. If non are matched, it returns a string |
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* version of the number (if __entry->bar == 7 then "7" is returned). |
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*/ |
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__print_symbolic(__entry->bar, |
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{ 0, "zero" }, |
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{ TRACE_SAMPLE_FOO, "TWO" }, |
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{ TRACE_SAMPLE_BAR, "FOUR" }, |
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{ TRACE_SAMPLE_ZOO, "EIGHT" }, |
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{ 10, "TEN" } |
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), |
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/* |
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* __print_flags( variable, "delim", { value, "flag" }, ... ), |
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* |
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* This is similar to __print_symbolic, except that it tests the bits |
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* of the value. If ((FLAG & variable) == FLAG) then the string is |
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* printed. If more than one flag matches, then each one that does is |
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* also printed with delim in between them. |
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* If not all bits are accounted for, then the not found bits will be |
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* added in hex format: 0x506 will show BIT2|BIT4|0x500 |
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*/ |
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__print_flags(__entry->bar, "|", |
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{ 1, "BIT1" }, |
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{ 2, "BIT2" }, |
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{ 4, "BIT3" }, |
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{ 8, "BIT4" } |
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), |
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/* |
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* __print_array( array, len, element_size ) |
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* |
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* This prints out the array that is defined by __array in a nice format. |
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*/ |
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__print_array(__get_dynamic_array(list), |
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__get_dynamic_array_len(list) / sizeof(int), |
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sizeof(int)), |
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__get_str(str), __get_bitmask(cpus)) |
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); |
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/* |
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* There may be a case where a tracepoint should only be called if |
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* some condition is set. Otherwise the tracepoint should not be called. |
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* But to do something like: |
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* |
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* if (cond) |
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* trace_foo(); |
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* |
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* Would cause a little overhead when tracing is not enabled, and that |
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* overhead, even if small, is not something we want. As tracepoints |
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* use static branch (aka jump_labels), where no branch is taken to |
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* skip the tracepoint when not enabled, and a jmp is placed to jump |
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* to the tracepoint code when it is enabled, having a if statement |
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* nullifies that optimization. It would be nice to place that |
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* condition within the static branch. This is where TRACE_EVENT_CONDITION |
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* comes in. |
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* |
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* TRACE_EVENT_CONDITION() is just like TRACE_EVENT, except it adds another |
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* parameter just after args. Where TRACE_EVENT has: |
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* |
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* TRACE_EVENT(name, proto, args, struct, assign, printk) |
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* |
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* the CONDITION version has: |
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* |
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* TRACE_EVENT_CONDITION(name, proto, args, cond, struct, assign, printk) |
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* |
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* Everything is the same as TRACE_EVENT except for the new cond. Think |
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* of the cond variable as: |
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* |
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* if (cond) |
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* trace_foo_bar_with_cond(); |
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* |
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* Except that the logic for the if branch is placed after the static branch. |
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* That is, the if statement that processes the condition will not be |
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* executed unless that traecpoint is enabled. Otherwise it still remains |
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* a nop. |
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*/ |
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TRACE_EVENT_CONDITION(foo_bar_with_cond, |
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TP_PROTO(const char *foo, int bar), |
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TP_ARGS(foo, bar), |
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TP_CONDITION(!(bar % 10)), |
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TP_STRUCT__entry( |
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__string( foo, foo ) |
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__field( int, bar ) |
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), |
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TP_fast_assign( |
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__assign_str(foo, foo); |
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__entry->bar = bar; |
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), |
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TP_printk("foo %s %d", __get_str(foo), __entry->bar) |
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); |
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int foo_bar_reg(void); |
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void foo_bar_unreg(void); |
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/* |
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* Now in the case that some function needs to be called when the |
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* tracepoint is enabled and/or when it is disabled, the |
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* TRACE_EVENT_FN() serves this purpose. This is just like TRACE_EVENT() |
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* but adds two more parameters at the end: |
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* |
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* TRACE_EVENT_FN( name, proto, args, struct, assign, printk, reg, unreg) |
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* |
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* reg and unreg are functions with the prototype of: |
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* |
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* void reg(void) |
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* |
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* The reg function gets called before the tracepoint is enabled, and |
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* the unreg function gets called after the tracepoint is disabled. |
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* |
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* Note, reg and unreg are allowed to be NULL. If you only need to |
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* call a function before enabling, or after disabling, just set one |
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* function and pass in NULL for the other parameter. |
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*/ |
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TRACE_EVENT_FN(foo_bar_with_fn, |
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TP_PROTO(const char *foo, int bar), |
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TP_ARGS(foo, bar), |
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TP_STRUCT__entry( |
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__string( foo, foo ) |
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__field( int, bar ) |
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), |
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TP_fast_assign( |
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__assign_str(foo, foo); |
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__entry->bar = bar; |
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), |
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TP_printk("foo %s %d", __get_str(foo), __entry->bar), |
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foo_bar_reg, foo_bar_unreg |
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); |
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/* |
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* Each TRACE_EVENT macro creates several helper functions to produce |
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* the code to add the tracepoint, create the files in the trace |
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* directory, hook it to perf, assign the values and to print out |
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* the raw data from the ring buffer. To prevent too much bloat, |
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* if there are more than one tracepoint that uses the same format |
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* for the proto, args, struct, assign and printk, and only the name |
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* is different, it is highly recommended to use the DECLARE_EVENT_CLASS |
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* |
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* DECLARE_EVENT_CLASS() macro creates most of the functions for the |
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* tracepoint. Then DEFINE_EVENT() is use to hook a tracepoint to those |
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* functions. This DEFINE_EVENT() is an instance of the class and can |
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* be enabled and disabled separately from other events (either TRACE_EVENT |
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* or other DEFINE_EVENT()s). |
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* |
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* Note, TRACE_EVENT() itself is simply defined as: |
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* |
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* #define TRACE_EVENT(name, proto, args, tstruct, assign, printk) \ |
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* DECLARE_EVENT_CLASS(name, proto, args, tstruct, assign, printk); \ |
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* DEFINE_EVENT(name, name, proto, args) |
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* |
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* The DEFINE_EVENT() also can be declared with conditions and reg functions: |
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* |
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* DEFINE_EVENT_CONDITION(template, name, proto, args, cond); |
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* DEFINE_EVENT_FN(template, name, proto, args, reg, unreg); |
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*/ |
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DECLARE_EVENT_CLASS(foo_template, |
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TP_PROTO(const char *foo, int bar), |
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TP_ARGS(foo, bar), |
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TP_STRUCT__entry( |
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__string( foo, foo ) |
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__field( int, bar ) |
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), |
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TP_fast_assign( |
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__assign_str(foo, foo); |
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__entry->bar = bar; |
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), |
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TP_printk("foo %s %d", __get_str(foo), __entry->bar) |
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); |
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/* |
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* Here's a better way for the previous samples (except, the first |
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* example had more fields and could not be used here). |
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*/ |
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DEFINE_EVENT(foo_template, foo_with_template_simple, |
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TP_PROTO(const char *foo, int bar), |
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TP_ARGS(foo, bar)); |
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DEFINE_EVENT_CONDITION(foo_template, foo_with_template_cond, |
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TP_PROTO(const char *foo, int bar), |
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TP_ARGS(foo, bar), |
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TP_CONDITION(!(bar % 8))); |
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DEFINE_EVENT_FN(foo_template, foo_with_template_fn, |
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TP_PROTO(const char *foo, int bar), |
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TP_ARGS(foo, bar), |
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foo_bar_reg, foo_bar_unreg); |
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/* |
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* Anytime two events share basically the same values and have |
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* the same output, use the DECLARE_EVENT_CLASS() and DEFINE_EVENT() |
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* when ever possible. |
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*/ |
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/* |
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* If the event is similar to the DECLARE_EVENT_CLASS, but you need |
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* to have a different output, then use DEFINE_EVENT_PRINT() which |
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* lets you override the TP_printk() of the class. |
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*/ |
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DEFINE_EVENT_PRINT(foo_template, foo_with_template_print, |
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TP_PROTO(const char *foo, int bar), |
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TP_ARGS(foo, bar), |
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TP_printk("bar %s %d", __get_str(foo), __entry->bar)); |
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#endif |
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/***** NOTICE! The #if protection ends here. *****/ |
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/* |
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* There are several ways I could have done this. If I left out the |
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* TRACE_INCLUDE_PATH, then it would default to the kernel source |
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* include/trace/events directory. |
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* |
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* I could specify a path from the define_trace.h file back to this |
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* file. |
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* |
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* #define TRACE_INCLUDE_PATH ../../samples/trace_events |
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* |
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* But the safest and easiest way to simply make it use the directory |
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* that the file is in is to add in the Makefile: |
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* |
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* CFLAGS_trace-events-sample.o := -I$(src) |
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* |
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* This will make sure the current path is part of the include |
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* structure for our file so that define_trace.h can find it. |
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* |
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* I could have made only the top level directory the include: |
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* |
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* CFLAGS_trace-events-sample.o := -I$(PWD) |
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* |
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* And then let the path to this directory be the TRACE_INCLUDE_PATH: |
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* |
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* #define TRACE_INCLUDE_PATH samples/trace_events |
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* |
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* But then if something defines "samples" or "trace_events" as a macro |
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* then we could risk that being converted too, and give us an unexpected |
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* result. |
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*/ |
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#undef TRACE_INCLUDE_PATH |
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#undef TRACE_INCLUDE_FILE |
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#define TRACE_INCLUDE_PATH . |
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/* |
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* TRACE_INCLUDE_FILE is not needed if the filename and TRACE_SYSTEM are equal |
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*/ |
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#define TRACE_INCLUDE_FILE trace-events-sample |
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#include <trace/define_trace.h>
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