117 lines
3.3 KiB
Plaintext
117 lines
3.3 KiB
Plaintext
libtracefs(3)
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=============
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NAME
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----
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tracefs_print_init, tracefs_print_close, tracefs_printf, tracefs_vprintf -
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Open, close and write formated strings in the trace buffer.
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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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int *tracefs_print_init*(struct tracefs_instance pass:[*]_instance_);
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int *tracefs_printf*(struct tracefs_instance pass:[*]_instance_, const char pass:[*]_fmt_, _..._);
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int *tracefs_vprintf*(struct tracefs_instance pass:[*]_instance_, const char pass:[*]_fmt_, va_list _ap_);
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void *tracefs_print_close*(struct tracefs_instance pass:[*]_instance_);
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--
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DESCRIPTION
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-----------
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Set of functions to write formated strings in the trace buffer.
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See Documentation/trace/ftrace.rst from the Linux kernel tree for more information about writing
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data from user space in the trace buffer. All these APIs have _instance_ as a first argument. If
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NULL is passed as _instance_, the top trace instance is used.
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The *tracefs_print_init()* function initializes the library for writing into the trace buffer of
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the selected _instance_. It is not mandatory to call this API before writing strings, any of
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the printf APIs will call it automatically, if the library is not yet initialized. But calling
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*tracefs_print_init()* in advance will speed up the writing.
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The *tracefs_printf()* function writes a formatted string in the trace buffer of the selected
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_instance_. The _fmt_ argument is a string in printf format, followed by variable arguments _..._.
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The *tracefs_vprintf()* function writes a formatted string in the trace buffer of the selected
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_instance_. The _fmt_ argument is a string in printf format, followed by list _ap_ of arguments.
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The *tracefs_print_close()* function closes the resources, used by the library for writing in
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the trace buffer of the selected instance.
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RETURN VALUE
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------------
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The *tracefs_print_init()*, *tracefs_printf()*, and *tracefs_vprintf()* functions return 0 if
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the operation is successful, or -1 in case of an error.
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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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if (tracefs_print_init(NULL) < 0) {
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/* Failed to initialize the library for writing in the trace buffer of the top trace instance */
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}
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void foo_print(char *format, ...)
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{
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va_list ap;
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va_start(ap, format);
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if (tracefs_vprintf(NULL, format, ap) < 0) {
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/* Failed to print in the trace buffer */
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}
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va_end(ap);
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}
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void foo_print_string(char *message)
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{
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if (tracefs_printf(NULL, "Message from user space: %s", message) < 0) {
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/* Failed to print in the trace buffer */
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}
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}
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tracefs_print_close();
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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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Documentation/trace/ftrace.rst from the Linux kernel tree
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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) 2021 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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