140 lines
4.4 KiB
Plaintext
140 lines
4.4 KiB
Plaintext
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libtracefs(3)
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=============
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NAME
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----
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tracefs_tracers, tracefs_tracer_available, tracefs_get_clock, tracefs_list_free,
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tracefs_list_add, tracefs_list_size - Helper functions for working with trace file system.
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SYNOPSIS
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--------
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[verse]
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--
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*#include <tracefs.h>*
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char pass:[*]pass:[*]*tracefs_tracers*(const char pass:[*]_tracing_dir_);
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bool *tracefs_tracer_available*(const char pass:[*]_tracing_dir_, const char pass:[*]_tracer_);
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char pass:[*]*tracefs_get_clock*(struct tracefs_instance pass:[*]_instance_);
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void *tracefs_list_free*(char pass:[*]pass:[*]_list_);
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char pass:[**]*tracefs_list_add*(char **_list_, const char *_string_);
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int *tracefs_list_size*(char pass:[**]_list_);
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--
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DESCRIPTION
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-----------
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Various useful functions for working with trace file system.
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The *tracefs_tracers()* function returns array of strings with the
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names of supported tracer plugins, located in the given _tracing_dir_
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directory. This could be NULL or the location of the tracefs mount point
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for the trace systems of the local machine, or it may be a path to a copy
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of the tracefs directory from another machine. The last entry in the array
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as a NULL pointer. The array must be freed with *tracefs_list_free()* API.
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The *tracefs_tracer_available()* returns true if the _tracer_ is available
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in the given _tracing_dir_director_, and false otherwise.
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The *tracefs_get_clock()* function returns name of the current trace clock,
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used in the given _instance_. If _instance_ is NULL, the clock of the main
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trace instance is returned. The returned string must be freed with free().
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The *tracefs_list_free()* function frees an array of strings, returned by
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*tracefs_event_systems()*, *tracefs_system_events()* and *tracefs_tracers()*
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APIs.
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The *tracefs_list_add()* function adds _string_ to the string _list_. If
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_list_ is NULL, then a new list is created with the first element a copy
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of _string_, and the second element will be a NULL pointer. If _list_ is
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not NULL, then it is reallocated to include a new element and a NULL terminator,
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and the new allocated array is returned. The list passed in should be ignored,
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as it wil be freed if a new one was allocated.
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The *tracefs_list_size()* is a fast way to find out the number of elements
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in a string array that is to be freed with *tracefs_list_free()*. Note, this
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depends on meta data that is created for these lists and will not work on
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normal string arrays like argv.
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RETURN VALUE
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------------
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The *tracefs_tracers()* returns array of strings. The last element in that
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array is a NULL pointer. The array must be freed with *tracefs_list_free()* API.
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In case of an error, NULL is returned.
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The *tracefs_tracer_available()* returns true if the _tracer_ is available,
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and false otherwise.
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The *tracefs_get_clock()* returns string, that must be freed with free(), or NULL
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in case of an error.
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The *tracefs_list_add()* returns an allocated string array that must be freed
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with *tracefs_list_free()* on success or NULL on error. If NULL is returned,
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then the passed in _list_ is untouched. Thus, *tracefs_list_add()* should be
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treated similarly to *realloc*(3).
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The *tracefs_list_size()* returns the number of strings in the _list_. The
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passed in list must be one that is to be freed with *tracefs_list_free()*
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as the list has meta data that is used to determine the size and this does
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not work on any normal string array like argv.
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EXAMPLE
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-------
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[source,c]
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--
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#include <tracefs.h>
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char **tracers = tracefs_tracers(NULL);
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if (tracers) {
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/* Got tracer plugins from the top trace instance */
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...
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tracefs_list_free(tracers);
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}
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....
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char *clock = tracefs_get_clock(NULL);
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if (clock) {
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/* Got current trace clock of the top trace instance */
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...
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free(clock);
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}
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--
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FILES
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-----
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[verse]
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--
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*tracefs.h*
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Header file to include in order to have access to the library APIs.
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*-ltracefs*
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Linker switch to add when building a program that uses the library.
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--
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SEE ALSO
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--------
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*libtracefs*(3),
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*libtraceevent*(3),
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*trace-cmd*(1)
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AUTHOR
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------
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[verse]
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--
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*Steven Rostedt* <rostedt@goodmis.org>
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*Tzvetomir Stoyanov* <tz.stoyanov@gmail.com>
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--
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REPORTING BUGS
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--------------
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Report bugs to <linux-trace-devel@vger.kernel.org>
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LICENSE
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-------
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libtracefs is Free Software licensed under the GNU LGPL 2.1
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RESOURCES
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---------
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https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git/
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COPYING
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-------
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Copyright \(C) 2020 VMware, Inc. Free use of this software is granted under
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the terms of the GNU Public License (GPL).
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