SYNOPSIS

#include <tracefs.h>

const struct tracefs_options_mask *tracefs_options_get_supported(struct tracefs_instance *instance);
bool tracefs_option_is_supported(struct tracefs_instance *instance, enum tracefs_option_id id);
const struct tracefs_options_mask *tracefs_options_get_enabled(struct tracefs_instance *instance);
bool tracefs_option_is_enabled(struct tracefs_instance *instance, enum tracefs_option_id id);
bool tracefs_option_mask_is_set(const struct tracefs_options_mask *options, enum tracefs_option_id id);

DESCRIPTION

This set of APIs can be used to get and check current ftrace options. Supported ftrace options may depend on the kernel version and the kernel configuration.

The tracefs_options_get_supported() function gets all ftrace options supported by the system in the given instance. If instance is NULL, supported options of the top trace instance are returned. The set of supported options is the same in all created trace instances, but may be different than the top trace instance.

The tracefs_option_is_supported() function checks if the option with given id is supported by the system in the given instance. If instance is NULL, the top trace instance is used. If an option is supported at the top trace instance, it it may not be supported in a created trace instance.

The tracefs_options_get_enabled() function gets all ftrace options, currently enabled in the given instance. If instance is NULL, enabled options of the top trace instance are returned.

The tracefs_option_is_enabled() function checks if the option with given id is enabled in the given instance. If instance is NULL, the top trace instance is used.

The tracefs_option_mask_is_set() function checks if the bit, corresponding to the option with id is set in the options bitmask returned from tracefs_option_get_enabled() and tracefs_option_is_supported().

RETURN VALUE

The tracefs_options_get_supported() and tracefs_options_get_enabled() functions, on success, return a pointer to the bitmask within the instance, or a global bitmask for the top level, or NULL in case of an error. As the returned bitmask is part of the instance structure (or a global variable) and must not be freed or modified.

The tracefs_option_is_supported() and tracefs_option_is_enabled() functions return true if the option in supported / enabled, or false otherwise.

The tracefs_option_mask_is_set() returns true if the corresponding option is set in the mask or false otherwise.

EXAMPLE

#include <tracefs.h>
...
const struct tracefs_options_mask *options;
...
options = tracefs_options_get_supported(NULL);
if (!options) {
        /* Failed to get supported options */
} else {
        ...
}
...
options = tracefs_options_get_enabled(NULL);
if (!options) {
        /* Failed to get options, enabled in the top instance */
} else {
        ...
}
if (tracefs_options_mask_is_set(options, TRACEFS_OPTION_LATENCY_FORMAT)) {
        ...
}
...

if (tracefs_option_is_supported(NULL, TRACEFS_OPTION_LATENCY_FORMAT)) {
        /* Latency format option is supprted */
}

...

if (tracefs_option_is_enabled(NULL, TRACEFS_OPTION_STACKTRACE)) {
        /* Stacktrace option is enabled in the top instance */
}

FILES

tracefs.h
        Header file to include in order to have access to the library APIs.
-ltracefs
        Linker switch to add when building a program that uses the library.

SEE ALSO

libtracefs(3), libtraceevent(3), trace-cmd(1)

AUTHOR

Steven Rostedt <rostedt@goodmis.org>
Tzvetomir Stoyanov <tz.stoyanov@gmail.com>

REPORTING BUGS

LICENSE

libtracefs is Free Software licensed under the GNU LGPL 2.1

RESOURCES

COPYING

Copyright (C) 2020 VMware, Inc. Free use of this software is granted under the terms of the GNU Public License (GPL).