mirror of https://gitee.com/openkylin/linux.git
316 lines
10 KiB
C
316 lines
10 KiB
C
/*
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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.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". 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
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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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* 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 teh 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 is 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 numebr 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 nul 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 paramenter (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.
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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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#endif
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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)", __entry->foo, __entry->bar,
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__print_array(__get_dynamic_array(list),
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__get_dynamic_array_len(list),
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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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#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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