linux/samples/trace_events/trace-events-sample.h
<<
>>
Prefs
   1/*
   2 * If TRACE_SYSTEM is defined, that will be the directory created
   3 * in the ftrace directory under /sys/kernel/debug/tracing/events/<system>
   4 *
   5 * The define_trace.h below will also look for a file name of
   6 * TRACE_SYSTEM.h where TRACE_SYSTEM is what is defined here.
   7 * In this case, it would look for sample.h
   8 *
   9 * If the header name will be different than the system name
  10 * (as in this case), then you can override the header name that
  11 * define_trace.h will look up by defining TRACE_INCLUDE_FILE
  12 *
  13 * This file is called trace-events-sample.h but we want the system
  14 * to be called "sample". Therefore we must define the name of this
  15 * file:
  16 *
  17 * #define TRACE_INCLUDE_FILE trace-events-sample
  18 *
  19 * As we do an the bottom of this file.
  20 *
  21 * Notice that TRACE_SYSTEM should be defined outside of #if
  22 * protection, just like TRACE_INCLUDE_FILE.
  23 */
  24#undef TRACE_SYSTEM
  25#define TRACE_SYSTEM sample
  26
  27/*
  28 * Notice that this file is not protected like a normal header.
  29 * We also must allow for rereading of this file. The
  30 *
  31 *  || defined(TRACE_HEADER_MULTI_READ)
  32 *
  33 * serves this purpose.
  34 */
  35#if !defined(_TRACE_EVENT_SAMPLE_H) || defined(TRACE_HEADER_MULTI_READ)
  36#define _TRACE_EVENT_SAMPLE_H
  37
  38/*
  39 * All trace headers should include tracepoint.h, until we finally
  40 * make it into a standard header.
  41 */
  42#include <linux/tracepoint.h>
  43
  44/*
  45 * The TRACE_EVENT macro is broken up into 5 parts.
  46 *
  47 * name: name of the trace point. This is also how to enable the tracepoint.
  48 *   A function called trace_foo_bar() will be created.
  49 *
  50 * proto: the prototype of the function trace_foo_bar()
  51 *   Here it is trace_foo_bar(char *foo, int bar).
  52 *
  53 * args:  must match the arguments in the prototype.
  54 *    Here it is simply "foo, bar".
  55 *
  56 * struct:  This defines the way the data will be stored in the ring buffer.
  57 *    There are currently two types of elements. __field and __array.
  58 *    a __field is broken up into (type, name). Where type can be any
  59 *    type but an array.
  60 *    For an array. there are three fields. (type, name, size). The
  61 *    type of elements in the array, the name of the field and the size
  62 *    of the array.
  63 *
  64 *    __array( char, foo, 10) is the same as saying   char foo[10].
  65 *
  66 * fast_assign: This is a C like function that is used to store the items
  67 *    into the ring buffer.
  68 *
  69 * printk: This is a way to print out the data in pretty print. This is
  70 *    useful if the system crashes and you are logging via a serial line,
  71 *    the data can be printed to the console using this "printk" method.
  72 *
  73 * Note, that for both the assign and the printk, __entry is the handler
  74 * to the data structure in the ring buffer, and is defined by the
  75 * TP_STRUCT__entry.
  76 */
  77TRACE_EVENT(foo_bar,
  78
  79        TP_PROTO(char *foo, int bar),
  80
  81        TP_ARGS(foo, bar),
  82
  83        TP_STRUCT__entry(
  84                __array(        char,   foo,    10              )
  85                __field(        int,    bar                     )
  86        ),
  87
  88        TP_fast_assign(
  89                strncpy(__entry->foo, foo, 10);
  90                __entry->bar    = bar;
  91        ),
  92
  93        TP_printk("foo %s %d", __entry->foo, __entry->bar)
  94);
  95#endif
  96
  97/***** NOTICE! The #if protection ends here. *****/
  98
  99
 100/*
 101 * There are several ways I could have done this. If I left out the
 102 * TRACE_INCLUDE_PATH, then it would default to the kernel source
 103 * include/trace/events directory.
 104 *
 105 * I could specify a path from the define_trace.h file back to this
 106 * file.
 107 *
 108 * #define TRACE_INCLUDE_PATH ../../samples/trace_events
 109 *
 110 * But the safest and easiest way to simply make it use the directory
 111 * that the file is in is to add in the Makefile:
 112 *
 113 * CFLAGS_trace-events-sample.o := -I$(src)
 114 *
 115 * This will make sure the current path is part of the include
 116 * structure for our file so that define_trace.h can find it.
 117 *
 118 * I could have made only the top level directory the include:
 119 *
 120 * CFLAGS_trace-events-sample.o := -I$(PWD)
 121 *
 122 * And then let the path to this directory be the TRACE_INCLUDE_PATH:
 123 *
 124 * #define TRACE_INCLUDE_PATH samples/trace_events
 125 *
 126 * But then if something defines "samples" or "trace_events" as a macro
 127 * then we could risk that being converted too, and give us an unexpected
 128 * result.
 129 */
 130#undef TRACE_INCLUDE_PATH
 131#undef TRACE_INCLUDE_FILE
 132#define TRACE_INCLUDE_PATH .
 133/*
 134 * TRACE_INCLUDE_FILE is not needed if the filename and TRACE_SYSTEM are equal
 135 */
 136#define TRACE_INCLUDE_FILE trace-events-sample
 137#include <trace/define_trace.h>
 138
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.