/*
* 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 teh 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 numebr 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 nul terminated character array passed to it (it allows
* for NULL too, which would be converted into "(null)"). __string
* takes two paramenter (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.
*
* __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),
TP_ARGS(foo, bar, lst, string, mask),
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() )
),
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_bitmask(cpus, cpumask_bits(mask), num_possible_cpus());
),
TP_printk("foo %s %d %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))
);
/*
* 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)
);
void 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) \
* DEFINE_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
* exmaple 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));
#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>
