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Wed, 17 Feb 2021 19:38:50 -0800 (PST) From: "Tzvetomir Stoyanov (VMware)" To: rostedt@goodmis.org Cc: linux-trace-devel@vger.kernel.org Subject: [PATCH 2/2] libtracefs: Document APIs for trace options Date: Thu, 18 Feb 2021 05:38:46 +0200 Message-Id: <20210218033846.1891289-3-tz.stoyanov@gmail.com> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20210218033846.1891289-1-tz.stoyanov@gmail.com> References: <20210218033846.1891289-1-tz.stoyanov@gmail.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-trace-devel@vger.kernel.org Added documentation for libtracefs APIs realated to ftrace options: enum tracefs_option - short description of each option tracefs_option_set() tracefs_option_clear() qtracefs_option_is_set() tracefs_options_get_supported() tracefs_option_is_supported() tracefs_options_get_enabled() qtracefs_option_is_enabled() tracefs_option_enable() tracefs_option_diasble() tracefs_option_name() Signed-off-by: Tzvetomir Stoyanov (VMware) --- Documentation/libtracefs-option-bits.txt | 90 +++++++++++++ Documentation/libtracefs-option-get.txt | 123 ++++++++++++++++++ Documentation/libtracefs-option-misc.txt | 100 ++++++++++++++ Documentation/libtracefs-options.txt | 159 +++++++++++++++++++++++ 4 files changed, 472 insertions(+) create mode 100644 Documentation/libtracefs-option-bits.txt create mode 100644 Documentation/libtracefs-option-get.txt create mode 100644 Documentation/libtracefs-option-misc.txt create mode 100644 Documentation/libtracefs-options.txt diff --git a/Documentation/libtracefs-option-bits.txt b/Documentation/libtracefs-option-bits.txt new file mode 100644 index 0000000..d713a5e --- /dev/null +++ b/Documentation/libtracefs-option-bits.txt @@ -0,0 +1,90 @@ +libtracefs(3) +============= + +NAME +---- +tracefs_option_set, tracefs_option_clear, tracefs_option_is_set - +Set, clear, check option in a bitmask. + +SYNOPSIS +-------- +[verse] +-- +*#include * + +void *tracefs_option_set*(struct tracefs_options_mask pass:[*]_options_, enum tracefs_option_id _id_); +void *tracefs_option_clear*(struct tracefs_options_mask pass:[*]_options_, enum tracefs_option_id _id_); +bool *tracefs_option_is_set*(struct tracefs_options_mask _options_, enum tracefs_option_id _id_); +-- + +DESCRIPTION +----------- +This set of APIs can be used to manipulate a bitmask with option IDs. + +The _tracefs_option_set()_ function sets the bit, corresponding to the option with _id_ in the +_options_ bitmask. + +The _tracefs_option_clear()_ function clears the bit, corresponding to the option with _id_ in the +_options_ bitmask. + +The _tracefs_option_is_set()_ function checks if the bit, corresponding to the option with _id_ is +set in the _options_ bitmask. + +RETURN VALUE +------------ +The _tracefs_option_is_set()_ function returns true if the bit is set, false otherwise. + +EXAMPLE +------- +[source,c] +-- +#include +... +struct tracefs_options_mask options; +memset(&options, 0, sizeof(options)); +... +tracefs_option_set(&options, TRACEFS_OPTION_EVENT_FORK | TRACEFS_OPTION_FUNCTION_FORK); +... +if (tracefs_option_is_set(options, TRACEFS_OPTION_EVENT_FORK)) + tracefs_option_clear(&options, TRACEFS_OPTION_EVENT_FORK); +... +-- +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)_ + +AUTHOR +------ +[verse] +-- +*Steven Rostedt* +*Tzvetomir Stoyanov* +-- +REPORTING BUGS +-------------- +Report bugs to + +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) 2020 VMware, Inc. Free use of this software is granted under +the terms of the GNU Public License (GPL). diff --git a/Documentation/libtracefs-option-get.txt b/Documentation/libtracefs-option-get.txt new file mode 100644 index 0000000..9b3cb56 --- /dev/null +++ b/Documentation/libtracefs-option-get.txt @@ -0,0 +1,123 @@ +libtracefs(3) +============= + +NAME +---- +tracefs_options_get_supported, tracefs_option_is_supported, +tracefs_options_get_enabled, tracefs_option_is_enabled - Get and check ftrace options. + +SYNOPSIS +-------- +[verse] +-- +*#include * + +struct tracefs_options_mask pass:[*]*tracefs_options_get_supported*(struct tracefs_instance pass:[*]_instance_); +bool *tracefs_option_is_supported*(struct tracefs_instance pass:[*]_instance_, enum tracefs_option_id _id_); +struct tracefs_options_mask pass:[*]*tracefs_options_get_enabled*(struct tracefs_instance pass:[*]_instance_); +bool *tracefs_option_is_enabled*(struct tracefs_instance pass:[*]_instance_, 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 must be the same in all trace instances. + +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 must be supported in all trace instances also. + +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. + +RETURN VALUE +------------ +The _tracefs_options_get_supported()_ and _tracefs_options_get_enabled()_ functions return pointer +to allocated bitmask with trace options, or NULL in case of an error. The returned bitmask must be +freed with free(); + +The _tracefs_option_is_supported()_ and _tracefs_option_is_enabled()_ functions return true if the +option in supported / enabled, or false otherwise. + +EXAMPLE +------- +[source,c] +-- +#include +... +struct tracefs_options_mask *options; +... +options = tracefs_options_get_supported(NULL); +if (!options) { + /* Failed to get supported options */ +} else { + ... + free(options); +} +... +options = tracefs_options_get_enabled(NULL); +if (!options) { + /* Failed to get options, enabled in the top instance */ +} else { + ... + free(options); +} +... + +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 +----- +[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)_ + +AUTHOR +------ +[verse] +-- +*Steven Rostedt* +*Tzvetomir Stoyanov* +-- +REPORTING BUGS +-------------- +Report bugs to + +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) 2020 VMware, Inc. Free use of this software is granted under +the terms of the GNU Public License (GPL). diff --git a/Documentation/libtracefs-option-misc.txt b/Documentation/libtracefs-option-misc.txt new file mode 100644 index 0000000..1cd7c88 --- /dev/null +++ b/Documentation/libtracefs-option-misc.txt @@ -0,0 +1,100 @@ +libtracefs(3) +============= + +NAME +---- +tracefs_option_enable, tracefs_option_diasble, tracefs_option_name - +Various trace option functions. + +SYNOPSIS +-------- +[verse] +-- +*#include * + +int *tracefs_option_enable*(struct tracefs_instance pass:[*]_instance_, enum tracefs_option_id _id_); +int *tracefs_option_diasble*(struct tracefs_instance pass:[*]_instance_, enum tracefs_option_id _id_); +const char pass:[*]*tracefs_option_name*(enum tracefs_option_id _id_); +-- + +DESCRIPTION +----------- +This set of APIs can be used to enable and disable ftrace options and to get the name of an option. + +The _tracefs_option_enable()_ function enables the option with _id_ in the given _instance_. If +_instance_ is NULL, the option is enabled in the top trace instance. + +The _tracefs_option_diasble()_ function disables the option with _id_ in the given _instance_. If +_instance_ is NULL, the option is disabled in the top trace instance. + +The _tracefs_option_name()_ function returns a string, representing the option with _id_. The string +must *not* be freed. + + +RETURN VALUE +------------ +The _tracefs_option_enable()_ and _tracefs_option_diasble()_ functions return 0 if the state of the +option is set successfully, or -1 in case of an error. + +The _tracefs_option_name()_ function returns string with option name, or "unknown" in case of an +error. The returned string must *not* be freed. + +EXAMPLE +------- +[source,c] +-- +#include +... +if (tracefs_option_enable(NULL, TRACEFS_OPTION_ANNOTATE)) { + /* Failed to enable annotate option in top trace instance */ +} +... +if (tracefs_option_diasble(NULL, TRACEFS_OPTION_CONTEXT_INFO)) { + /* Failed to disable context info option in top trace instance */ +} +... +char *name = tracefs_option_name(TRACEFS_OPTION_FUNC_STACKTRACE); +if (strcmp(name, "unknown")) { + /* Cannot get the name of the option */ +} + +-- +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)_ + +AUTHOR +------ +[verse] +-- +*Steven Rostedt* +*Tzvetomir Stoyanov* +-- +REPORTING BUGS +-------------- +Report bugs to + +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) 2020 VMware, Inc. Free use of this software is granted under +the terms of the GNU Public License (GPL). diff --git a/Documentation/libtracefs-options.txt b/Documentation/libtracefs-options.txt new file mode 100644 index 0000000..b8f0edf --- /dev/null +++ b/Documentation/libtracefs-options.txt @@ -0,0 +1,159 @@ +libtracefs(3) +============= + +NAME +---- +tracefs_options - ftrace options, that can be controlled using tracefs library. + +SYNOPSIS +-------- +[verse] +-- +*#include * + +enum tracefs_option_id { + *TRACEFS_OPTION_INVALID*, + *TRACEFS_OPTION_ANNOTATE*, + *TRACEFS_OPTION_BIN*, + *TRACEFS_OPTION_BLK_CGNAME*, + *TRACEFS_OPTION_BLK_CGROUP*, + *TRACEFS_OPTION_BLK_CLASSIC*, + *TRACEFS_OPTION_BLOCK*, + *TRACEFS_OPTION_CONTEXT_INFO*, + *TRACEFS_OPTION_DISABLE_ON_FREE*, + *TRACEFS_OPTION_DISPLAY_GRAPH*, + *TRACEFS_OPTION_EVENT_FORK*, + *TRACEFS_OPTION_FGRAPH_ABSTIME*, + *TRACEFS_OPTION_FGRAPH_CPU*, + *TRACEFS_OPTION_FGRAPH_DURATION*, + *TRACEFS_OPTION_FGRAPH_IRQS*, + *TRACEFS_OPTION_FGRAPH_OVERHEAD*, + *TRACEFS_OPTION_FGRAPH_OVERRUN*, + *TRACEFS_OPTION_FGRAPH_PROC*, + *TRACEFS_OPTION_FGRAPH_TAIL*, + *TRACEFS_OPTION_FUNC_STACKTRACE*, + *TRACEFS_OPTION_FUNCTION_FORK*, + *TRACEFS_OPTION_FUNCTION_TRACE*, + *TRACEFS_OPTION_GRAPH_TIME*, + *TRACEFS_OPTION_HEX*, + *TRACEFS_OPTION_IRQ_INFO*, + *TRACEFS_OPTION_LATENCY_FORMAT*, + *TRACEFS_OPTION_MARKERS*, + *TRACEFS_OPTION_OVERWRITE*, + *TRACEFS_OPTION_PAUSE_ON_TRACE*, + *TRACEFS_OPTION_PRINTK_MSG_ONLY*, + *TRACEFS_OPTION_PRINT_PARENT*, + *TRACEFS_OPTION_RAW*, + *TRACEFS_OPTION_RECORD_CMD*, + *TRACEFS_OPTION_RECORD_TGID*, + *TRACEFS_OPTION_SLEEP_TIME*, + *TRACEFS_OPTION_STACKTRACE*, + *TRACEFS_OPTION_SYM_ADDR*, + *TRACEFS_OPTION_SYM_OFFSET*, + *TRACEFS_OPTION_SYM_USEROBJ*, + *TRACEFS_OPTION_TRACE_PRINTK*, + *TRACEFS_OPTION_USERSTACKTRACE*, + *TRACEFS_OPTION_VERBOSE*, +}; +-- + +DESCRIPTION +----------- +This enum contains all ftrace options, that can be manipulated using tracefs library. More detailed +information about each option is available in Documentation/trace/ftrace.rst from the Linux +kernel tree, in the trace_options section. Note that some ftrace options cannot be manipulated by +this library, as they are intended for internal, debug purposes. These options control the tracers +or the trace output. All options have two states - on and off, the default state is different for +each of them. +[verse] +-- +Common options for all tracers: + *TRACEFS_OPTION_INVALID* Not a valid ftrace option, used by the API to indicate an error. + *TRACEFS_OPTION_ANNOTATE* Display when a new CPU buffer started. + *TRACEFS_OPTION_BIN* Display the formats in raw binary. + *TRACEFS_OPTION_CONTEXT_INFO* Show only the event data. Hides the comm, PID, timestamp, CPU, and other useful data. + *TRACEFS_OPTION_BLOCK* When set, reading trace_pipe will not block when polled. + *TRACEFS_OPTION_DISABLE_ON_FREE* When the free_buffer is closed, tracing will stop. + *TRACEFS_OPTION_DISPLAY_GRAPH* When set, the latency tracers will use function graph tracing instead of function tracing. + *TRACEFS_OPTION_EVENT_FORK* When set, tasks with PIDs listed in set_event_pid will have the PIDs of their children added to set_event_pid when those tasks fork. + *TRACEFS_OPTION_FUNCTION_FORK* When set, tasks with PIDs listed in set_ftrace_pid will have the PIDs of their children added to set_ftrace_pid when those tasks fork. + *TRACEFS_OPTION_FUNCTION_TRACE* When enabled, the latency tracers will trace functions. + *TRACEFS_OPTION_HEX* Display numbers in a hexadecimal format. + *TRACEFS_OPTION_IRQ_INFO* Display the interrupt, preempt count, need resched data. + *TRACEFS_OPTION_LATENCY_FORMAT* Display additional information about the latency. + *TRACEFS_OPTION_MARKERS* When set, the trace_marker is enabled - writable (only by root). + *TRACEFS_OPTION_OVERWRITE* Controls what happens when the trace buffer is full. If set, the oldest events are discarded and overwritten. If disabled, then the newest events are discarded. + *TRACEFS_OPTION_PAUSE_ON_TRACE* When set, opening the trace file for read, will pause writing to the ring buffer. When the file is closed, tracing will be enabled again. + *TRACEFS_OPTION_PRINTK_MSG_ONLY* When set, trace_printk()s will only show the format and not their parameters. + *TRACEFS_OPTION_PRINT_PARENT* On function traces, display the calling (parent) function as well as the function being traced. + *TRACEFS_OPTION_RAW* Display raw numbers. + *TRACEFS_OPTION_RECORD_CMD* Save a mapping with a pid and corresponding command. + *TRACEFS_OPTION_RECORD_TGID* Save a mapping with a pid and corresponding Thread Group IDs. + *TRACEFS_OPTION_STACKTRACE* Record a stack trace after any trace event. + *TRACEFS_OPTION_SYM_ADDR* Display the function address as well as the function name. + *TRACEFS_OPTION_SYM_OFFSET* Display not only the function name, but also the offset in the function. + *TRACEFS_OPTION_SYM_USEROBJ* When *TRACEFS_OPTION_USERSTACKTRACE* is set, look up which object the address belongs to, and print the object and a relative address. + *TRACEFS_OPTION_TRACE_PRINTK* Disable trace_printk() from writing into the buffer. + *TRACEFS_OPTION_USERSTACKTRACE* Records a stack trace of the current user space thread after each trace event. + *TRACEFS_OPTION_VERBOSE* When *TRACEFS_OPTION_LATENCY_FORMAT* is enabled, print more detailed information. + +Options, specific to function tracer: + *TRACEFS_OPTION_FUNC_STACKTRACE* Record a stack trace after every function. + +Options, specific to function_graph tracer: + *TRACEFS_OPTION_FGRAPH_ABSTIME* Display the timestamp at each line. + *TRACEFS_OPTION_FGRAPH_CPU* Display the CPU number of the CPU where the trace occurred. + *TRACEFS_OPTION_FGRAPH_DURATION* Display the duration of the amount of time at the end of each function, in microseconds. + *TRACEFS_OPTION_FGRAPH_IRQS* Trace functions that happen inside an interrupt. + *TRACEFS_OPTION_FGRAPH_OVERHEAD* Display a marker if a function takes longer than a certain amount of time. + *TRACEFS_OPTION_FGRAPH_OVERRUN* Display "overrun" of the call graph, in the case of functions missed due to big callstack. + *TRACEFS_OPTION_FGRAPH_PROC* Display the command of each process at every line. + *TRACEFS_OPTION_FGRAPH_TAIL* Display the function name on its return. + *TRACEFS_OPTION_SLEEP_TIME* Account time the task has been scheduled out as part of the function call. + *TRACEFS_OPTION_GRAPH_TIME* Display the time to call nested functions, if function profiler is enabled. + +Options, specific to blk tracer: + *TRACEFS_OPTION_BLK_CGNAME* + *TRACEFS_OPTION_BLK_CGROUP* + *TRACEFS_OPTION_BLK_CLASSIC* Display a more minimalistic output. +-- +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* +*Tzvetomir Stoyanov* +-- +REPORTING BUGS +-------------- +Report bugs to + +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).