NAME

tracefs_binary_init, tracefs_binary_close, tracefs_binary_write - Open, close and write binary data in the trace buffer.

SYNOPSIS

#include <tracefs.h>
int tracefs_binary_init(struct tracefs_instance *instance);
int tracefs_binary_write(struct tracefs_instance *instance, void *data, int len);
void tracefs_binary_close(struct tracefs_instance *instance);

DESCRIPTION

Set of functions to write binary data in the trace buffer. See Documentation/trace/ftrace.rst from the Linux kernel tree for more information about writing data from user space in the trace buffer. All these APIs have instance as a first argument. If NULL is passed as instance, the top trace instance is used.

The tracefs_binary_init() function initializes the library for writing into the trace buffer of the selected instance. It is not mandatory to call this API before writing data, the tracefs_binary_write() will call it automatically, if the library is not yet initialized. But calling tracefs_binary_init() in advance will speed up the writing.

The tracefs_binary_write() function writes a binary data in the trace buffer of the selected instance. The data points to the data with length len, that is going to be written in the trace buffer.

The tracefs_binary_close() function closes the resources, used by the library for writing in the trace buffer of the selected instance.

RETURN VALUE

The tracefs_binary_init(), and tracefs_binary_write() functions return 0 if the operation is successful, or -1 in case of an error.

EXAMPLE

#include <tracefs.h>
if (tracefs_binary_init(NULL) < 0) {


 /* Failed to initialize the library for writing in the trace buffer of the top trace instance */
}
unsigned int data = 0xdeadbeef;


        if (tracefs_binary_write(NULL, &data, sizeof(data)) < 0) {


                /* Failed to write in the trace buffer */


        }
tracefs_binary_close();

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), Documentation/trace/ftrace.rst from the Linux kernel tree

AUTHOR

Steven Rostedt <rostedt@goodmis.org[1]>
Tzvetomir Stoyanov <tz.stoyanov@gmail.com[2]>

REPORTING BUGS

Report bugs to <linux-trace-devel@vger.kernel.org[3]>

LICENSE

libtracefs is Free Software licensed under the GNU LGPL 2.1

RESOURCES

https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git/

COPYING

Copyright (C) 2021 VMware, Inc. Free use of this software is granted under the terms of the GNU Public License (GPL).

NOTES

1.

rostedt@goodmis.org

2.

tz.stoyanov@gmail.com

3.

linux-trace-devel@vger.kernel.org