forked from Minki/linux
71e1c8ac42
When creating trace events for ftrace, the header file with the TRACE_EVENT macros must also have a macro called TRACE_SYSTEM. This macro describes the name of the system the TRACE_EVENTS are defined for. It also doubles as a way for the define_trace.h file to include the file that included it. For example: in irq.h #define TRACE_SYSTEM irq [...] #include <trace/define_trace.h> The define_trace will use TRACE_SYSTEM to include irq.h. But if the name of the trace system does not match the name of the trace header file, one can override it with: Which will change define_trace.h to inclued foo_trace.h instead of foo.h The sample comments this, but people that use the sample code will more likely use the code and not read the comments. This patch changes the sample code to use the TRACE_INCLUDE_FILE to better show developers how to use it. [ Impact: make sample less confusing to developers ] Reported-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
130 lines
3.8 KiB
C
130 lines
3.8 KiB
C
/*
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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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* If TRACE_SYSTEM is defined, that will be the directory created
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* in the ftrace directory under /debugfs/tracing/events/<system>
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*
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* The define_trace.h belowe 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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*
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* If you want a different system than file name, you can override
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* the header name by defining TRACE_INCLUDE_FILE
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*
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* If this file was called, goofy.h, then we would define:
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*
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* #define TRACE_INCLUDE_FILE goofy
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*
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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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* 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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* There are currently two types of elements. __field and __array.
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* a __field is broken up into (type, name). Where type can be any
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* type but an array.
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* For an array. there are three fields. (type, name, size). The
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* type of elements in the array, the name of the field and the size
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* of the array.
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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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* fast_assign: This is a C like function that is used to store the items
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* into the ring buffer.
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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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*
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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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TRACE_EVENT(foo_bar,
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TP_PROTO(char *foo, int bar),
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TP_ARGS(foo, bar),
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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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),
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TP_fast_assign(
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strncpy(__entry->foo, foo, 10);
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__entry->bar = bar;
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),
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TP_printk("foo %s %d", __entry->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 I chose to simply make it use the current directory and then in
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* the Makefile I added:
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*
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* CFLAGS_trace-events-sample.o := -I$(PWD)/samples/trace_events/
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*
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* This will make sure the current path is part of the include
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* structure for our file so that we can find it.
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*
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* I could have made only the top level directory the include:
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*
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* CFLAGS_trace-events-sample.o := -I$(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" then we
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* 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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