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diff --git a/Documentation/libtracefs-marker.txt b/Documentation/libtracefs-marker.txt new file mode 100644 index 0000000..adc5419 --- /dev/null +++ b/Documentation/libtracefs-marker.txt @@ -0,0 +1,116 @@ +libtracefs(3) +============= + +NAME +---- +tracefs_print_init, tracefs_print_close, tracefs_printf, tracefs_vprintf - +Open, close and write formated strings in the trace buffer. + +SYNOPSIS +-------- +[verse] +-- +*#include <tracefs.h>* + +int *tracefs_print_init*(struct tracefs_instance pass:[*]_instance_); +int *tracefs_printf*(struct tracefs_instance pass:[*]_instance_, const char pass:[*]_fmt_, _..._); +int *tracefs_vprintf*(struct tracefs_instance pass:[*]_instance_, const char pass:[*]_fmt_, va_list _ap_); +void *tracefs_print_close*(struct tracefs_instance pass:[*]_instance_); + +-- + +DESCRIPTION +----------- +Set of functions to write formated strings 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_print_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 strings, any of +the printf APIs will call it automatically, if the library is not yet initialized. But calling +*tracefs_print_init()* in advance will speed up the writing. + +The *tracefs_printf()* function writes a formatted string in the trace buffer of the selected +_instance_. The _fmt_ argument is a string in printf format, followed by variable arguments _..._. + +The *tracefs_vprintf()* function writes a formatted string in the trace buffer of the selected +_instance_. The _fmt_ argument is a string in printf format, followed by list _ap_ of arguments. + +The *tracefs_print_close()* function closes the resources, used by the library for writing in +the trace buffer of the selected instance. + +RETURN VALUE +------------ +The *tracefs_print_init()*, *tracefs_printf()*, and *tracefs_vprintf()* functions return 0 if +the operation is successful, or -1 in case of an error. + +EXAMPLE +------- +[source,c] +-- +#include <tracefs.h> + +if (tracefs_print_init(NULL) < 0) { + /* Failed to initialize the library for writing in the trace buffer of the top trace instance */ +} + +void foo_print(char *format, ...) +{ + va_list ap; + va_start(ap, format); + if (tracefs_vprintf(NULL, format, ap) < 0) { + /* Failed to print in the trace buffer */ + } + va_end(ap); +} + +void foo_print_string(char *message) +{ + if (tracefs_printf(NULL, "Message from user space: %s", message) < 0) { + /* Failed to print in the trace buffer */ + } +} + +tracefs_print_close(); +-- +FILES +----- +[verse] +-- +*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 +------ +[verse] +-- +*Steven Rostedt* <rostedt@goodmis.org> +*Tzvetomir Stoyanov* <tz.stoyanov@gmail.com> +-- +REPORTING BUGS +-------------- +Report bugs to <linux-trace-devel@vger.kernel.org> + +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). |