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-rw-r--r--Documentation/admin-guide/bootconfig.rst190
-rw-r--r--Documentation/admin-guide/index.rst1
-rw-r--r--Documentation/admin-guide/kernel-parameters.txt6
-rw-r--r--Documentation/trace/boottime-trace.rst184
-rw-r--r--Documentation/trace/events.rst515
-rw-r--r--Documentation/trace/index.rst1
-rw-r--r--Documentation/trace/kprobetrace.rst1
7 files changed, 898 insertions, 0 deletions
diff --git a/Documentation/admin-guide/bootconfig.rst b/Documentation/admin-guide/bootconfig.rst
new file mode 100644
index 000000000000..b342a6796392
--- /dev/null
+++ b/Documentation/admin-guide/bootconfig.rst
@@ -0,0 +1,190 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+.. _bootconfig:
+
+==================
+Boot Configuration
+==================
+
+:Author: Masami Hiramatsu <mhiramat@kernel.org>
+
+Overview
+========
+
+The boot configuration expands the current kernel command line to support
+additional key-value data when booting the kernel in an efficient way.
+This allows administrators to pass a structured-Key config file.
+
+Config File Syntax
+==================
+
+The boot config syntax is a simple structured key-value. Each key consists
+of dot-connected-words, and key and value are connected by ``=``. The value
+has to be terminated by semi-colon (``;``) or newline (``\n``).
+For array value, array entries are separated by comma (``,``). ::
+
+KEY[.WORD[...]] = VALUE[, VALUE2[...]][;]
+
+Unlike the kernel command line syntax, spaces are OK around the comma and ``=``.
+
+Each key word must contain only alphabets, numbers, dash (``-``) or underscore
+(``_``). And each value only contains printable characters or spaces except
+for delimiters such as semi-colon (``;``), new-line (``\n``), comma (``,``),
+hash (``#``) and closing brace (``}``).
+
+If you want to use those delimiters in a value, you can use either double-
+quotes (``"VALUE"``) or single-quotes (``'VALUE'``) to quote it. Note that
+you can not escape these quotes.
+
+There can be a key which doesn't have value or has an empty value. Those keys
+are used for checking if the key exists or not (like a boolean).
+
+Key-Value Syntax
+----------------
+
+The boot config file syntax allows user to merge partially same word keys
+by brace. For example::
+
+ foo.bar.baz = value1
+ foo.bar.qux.quux = value2
+
+These can be written also in::
+
+ foo.bar {
+ baz = value1
+ qux.quux = value2
+ }
+
+Or more shorter, written as following::
+
+ foo.bar { baz = value1; qux.quux = value2 }
+
+In both styles, same key words are automatically merged when parsing it
+at boot time. So you can append similar trees or key-values.
+
+Comments
+--------
+
+The config syntax accepts shell-script style comments. The comments starting
+with hash ("#") until newline ("\n") will be ignored.
+
+::
+
+ # comment line
+ foo = value # value is set to foo.
+ bar = 1, # 1st element
+ 2, # 2nd element
+ 3 # 3rd element
+
+This is parsed as below::
+
+ foo = value
+ bar = 1, 2, 3
+
+Note that you can not put a comment between value and delimiter(``,`` or
+``;``). This means following config has a syntax error ::
+
+ key = 1 # comment
+ ,2
+
+
+/proc/bootconfig
+================
+
+/proc/bootconfig is a user-space interface of the boot config.
+Unlike /proc/cmdline, this file shows the key-value style list.
+Each key-value pair is shown in each line with following style::
+
+ KEY[.WORDS...] = "[VALUE]"[,"VALUE2"...]
+
+
+Boot Kernel With a Boot Config
+==============================
+
+Since the boot configuration file is loaded with initrd, it will be added
+to the end of the initrd (initramfs) image file. The Linux kernel decodes
+the last part of the initrd image in memory to get the boot configuration
+data.
+Because of this "piggyback" method, there is no need to change or
+update the boot loader and the kernel image itself.
+
+To do this operation, Linux kernel provides "bootconfig" command under
+tools/bootconfig, which allows admin to apply or delete the config file
+to/from initrd image. You can build it by the following command::
+
+ # make -C tools/bootconfig
+
+To add your boot config file to initrd image, run bootconfig as below
+(Old data is removed automatically if exists)::
+
+ # tools/bootconfig/bootconfig -a your-config /boot/initrd.img-X.Y.Z
+
+To remove the config from the image, you can use -d option as below::
+
+ # tools/bootconfig/bootconfig -d /boot/initrd.img-X.Y.Z
+
+Then add "bootconfig" on the normal kernel command line to tell the
+kernel to look for the bootconfig at the end of the initrd file.
+
+Config File Limitation
+======================
+
+Currently the maximum config size size is 32KB and the total key-words (not
+key-value entries) must be under 1024 nodes.
+Note: this is not the number of entries but nodes, an entry must consume
+more than 2 nodes (a key-word and a value). So theoretically, it will be
+up to 512 key-value pairs. If keys contains 3 words in average, it can
+contain 256 key-value pairs. In most cases, the number of config items
+will be under 100 entries and smaller than 8KB, so it would be enough.
+If the node number exceeds 1024, parser returns an error even if the file
+size is smaller than 32KB.
+Anyway, since bootconfig command verifies it when appending a boot config
+to initrd image, user can notice it before boot.
+
+
+Bootconfig APIs
+===============
+
+User can query or loop on key-value pairs, also it is possible to find
+a root (prefix) key node and find key-values under that node.
+
+If you have a key string, you can query the value directly with the key
+using xbc_find_value(). If you want to know what keys exist in the boot
+config, you can use xbc_for_each_key_value() to iterate key-value pairs.
+Note that you need to use xbc_array_for_each_value() for accessing
+each array's value, e.g.::
+
+ vnode = NULL;
+ xbc_find_value("key.word", &vnode);
+ if (vnode && xbc_node_is_array(vnode))
+ xbc_array_for_each_value(vnode, value) {
+ printk("%s ", value);
+ }
+
+If you want to focus on keys which have a prefix string, you can use
+xbc_find_node() to find a node by the prefix string, and iterate
+keys under the prefix node with xbc_node_for_each_key_value().
+
+But the most typical usage is to get the named value under prefix
+or get the named array under prefix as below::
+
+ root = xbc_find_node("key.prefix");
+ value = xbc_node_find_value(root, "option", &vnode);
+ ...
+ xbc_node_for_each_array_value(root, "array-option", value, anode) {
+ ...
+ }
+
+This accesses a value of "key.prefix.option" and an array of
+"key.prefix.array-option".
+
+Locking is not needed, since after initialization, the config becomes
+read-only. All data and keys must be copied if you need to modify it.
+
+
+Functions and structures
+========================
+
+.. kernel-doc:: include/linux/bootconfig.h
+.. kernel-doc:: lib/bootconfig.c
+
diff --git a/Documentation/admin-guide/index.rst b/Documentation/admin-guide/index.rst
index 4433f3929481..f1d0ccffbe72 100644
--- a/Documentation/admin-guide/index.rst
+++ b/Documentation/admin-guide/index.rst
@@ -64,6 +64,7 @@ configure specific aspects of kernel behavior to your liking.
binderfs
binfmt-misc
blockdev/index
+ bootconfig
braille-console
btmrvl
cgroup-v1/index
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index ddc5ccdd4cd1..dbc22d684627 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -437,6 +437,12 @@
no delay (0).
Format: integer
+ bootconfig [KNL]
+ Extended command line options can be added to an initrd
+ and this will cause the kernel to look for it.
+
+ See Documentation/admin-guide/bootconfig.rst
+
bert_disable [ACPI]
Disable BERT OS support on buggy BIOSes.
diff --git a/Documentation/trace/boottime-trace.rst b/Documentation/trace/boottime-trace.rst
new file mode 100644
index 000000000000..dcb390075ca1
--- /dev/null
+++ b/Documentation/trace/boottime-trace.rst
@@ -0,0 +1,184 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=================
+Boot-time tracing
+=================
+
+:Author: Masami Hiramatsu <mhiramat@kernel.org>
+
+Overview
+========
+
+Boot-time tracing allows users to trace boot-time process including
+device initialization with full features of ftrace including per-event
+filter and actions, histograms, kprobe-events and synthetic-events,
+and trace instances.
+Since kernel command line is not enough to control these complex features,
+this uses bootconfig file to describe tracing feature programming.
+
+Options in the Boot Config
+==========================
+
+Here is the list of available options list for boot time tracing in
+boot config file [1]_. All options are under "ftrace." or "kernel."
+prefix. See kernel parameters for the options which starts
+with "kernel." prefix [2]_.
+
+.. [1] See :ref:`Documentation/admin-guide/bootconfig.rst <bootconfig>`
+.. [2] See :ref:`Documentation/admin-guide/kernel-parameters.rst <kernelparameters>`
+
+Ftrace Global Options
+---------------------
+
+Ftrace global options have "kernel." prefix in boot config, which means
+these options are passed as a part of kernel legacy command line.
+
+kernel.tp_printk
+ Output trace-event data on printk buffer too.
+
+kernel.dump_on_oops [= MODE]
+ Dump ftrace on Oops. If MODE = 1 or omitted, dump trace buffer
+ on all CPUs. If MODE = 2, dump a buffer on a CPU which kicks Oops.
+
+kernel.traceoff_on_warning
+ Stop tracing if WARN_ON() occurs.
+
+kernel.fgraph_max_depth = MAX_DEPTH
+ Set MAX_DEPTH to maximum depth of fgraph tracer.
+
+kernel.fgraph_filters = FILTER[, FILTER2...]
+ Add fgraph tracing function filters.
+
+kernel.fgraph_notraces = FILTER[, FILTER2...]
+ Add fgraph non-tracing function filters.
+
+
+Ftrace Per-instance Options
+---------------------------
+
+These options can be used for each instance including global ftrace node.
+
+ftrace.[instance.INSTANCE.]options = OPT1[, OPT2[...]]
+ Enable given ftrace options.
+
+ftrace.[instance.INSTANCE.]trace_clock = CLOCK
+ Set given CLOCK to ftrace's trace_clock.
+
+ftrace.[instance.INSTANCE.]buffer_size = SIZE
+ Configure ftrace buffer size to SIZE. You can use "KB" or "MB"
+ for that SIZE.
+
+ftrace.[instance.INSTANCE.]alloc_snapshot
+ Allocate snapshot buffer.
+
+ftrace.[instance.INSTANCE.]cpumask = CPUMASK
+ Set CPUMASK as trace cpu-mask.
+
+ftrace.[instance.INSTANCE.]events = EVENT[, EVENT2[...]]
+ Enable given events on boot. You can use a wild card in EVENT.
+
+ftrace.[instance.INSTANCE.]tracer = TRACER
+ Set TRACER to current tracer on boot. (e.g. function)
+
+ftrace.[instance.INSTANCE.]ftrace.filters
+ This will take an array of tracing function filter rules.
+
+ftrace.[instance.INSTANCE.]ftrace.notraces
+ This will take an array of NON-tracing function filter rules.
+
+
+Ftrace Per-Event Options
+------------------------
+
+These options are setting per-event options.
+
+ftrace.[instance.INSTANCE.]event.GROUP.EVENT.enable
+ Enable GROUP:EVENT tracing.
+
+ftrace.[instance.INSTANCE.]event.GROUP.EVENT.filter = FILTER
+ Set FILTER rule to the GROUP:EVENT.
+
+ftrace.[instance.INSTANCE.]event.GROUP.EVENT.actions = ACTION[, ACTION2[...]]
+ Set ACTIONs to the GROUP:EVENT.
+
+ftrace.[instance.INSTANCE.]event.kprobes.EVENT.probes = PROBE[, PROBE2[...]]
+ Defines new kprobe event based on PROBEs. It is able to define
+ multiple probes on one event, but those must have same type of
+ arguments. This option is available only for the event which
+ group name is "kprobes".
+
+ftrace.[instance.INSTANCE.]event.synthetic.EVENT.fields = FIELD[, FIELD2[...]]
+ Defines new synthetic event with FIELDs. Each field should be
+ "type varname".
+
+Note that kprobe and synthetic event definitions can be written under
+instance node, but those are also visible from other instances. So please
+take care for event name conflict.
+
+
+Examples
+========
+
+For example, to add filter and actions for each event, define kprobe
+events, and synthetic events with histogram, write a boot config like
+below::
+
+ ftrace.event {
+ task.task_newtask {
+ filter = "pid < 128"
+ enable
+ }
+ kprobes.vfs_read {
+ probes = "vfs_read $arg1 $arg2"
+ filter = "common_pid < 200"
+ enable
+ }
+ synthetic.initcall_latency {
+ fields = "unsigned long func", "u64 lat"
+ actions = "hist:keys=func.sym,lat:vals=lat:sort=lat"
+ }
+ initcall.initcall_start {
+ actions = "hist:keys=func:ts0=common_timestamp.usecs"
+ }
+ initcall.initcall_finish {
+ actions = "hist:keys=func:lat=common_timestamp.usecs-$ts0:onmatch(initcall.initcall_start).initcall_latency(func,$lat)"
+ }
+ }
+
+Also, boot-time tracing supports "instance" node, which allows us to run
+several tracers for different purpose at once. For example, one tracer
+is for tracing functions starting with "user\_", and others tracing
+"kernel\_" functions, you can write boot config as below::
+
+ ftrace.instance {
+ foo {
+ tracer = "function"
+ ftrace.filters = "user_*"
+ }
+ bar {
+ tracer = "function"
+ ftrace.filters = "kernel_*"
+ }
+ }
+
+The instance node also accepts event nodes so that each instance
+can customize its event tracing.
+
+This boot-time tracing also supports ftrace kernel parameters via boot
+config.
+For example, following kernel parameters::
+
+ trace_options=sym-addr trace_event=initcall:* tp_printk trace_buf_size=1M ftrace=function ftrace_filter="vfs*"
+
+This can be written in boot config like below::
+
+ kernel {
+ trace_options = sym-addr
+ trace_event = "initcall:*"
+ tp_printk
+ trace_buf_size = 1M
+ ftrace = function
+ ftrace_filter = "vfs*"
+ }
+
+Note that parameters start with "kernel" prefix instead of "ftrace".
diff --git a/Documentation/trace/events.rst b/Documentation/trace/events.rst
index f7e1fcc0953c..ed79b220bd07 100644
--- a/Documentation/trace/events.rst
+++ b/Documentation/trace/events.rst
@@ -525,3 +525,518 @@ The following commands are supported:
event counts (hitcount).
See Documentation/trace/histogram.rst for details and examples.
+
+6.3 In-kernel trace event API
+-----------------------------
+
+In most cases, the command-line interface to trace events is more than
+sufficient. Sometimes, however, applications might find the need for
+more complex relationships than can be expressed through a simple
+series of linked command-line expressions, or putting together sets of
+commands may be simply too cumbersome. An example might be an
+application that needs to 'listen' to the trace stream in order to
+maintain an in-kernel state machine detecting, for instance, when an
+illegal kernel state occurs in the scheduler.
+
+The trace event subsystem provides an in-kernel API allowing modules
+or other kernel code to generate user-defined 'synthetic' events at
+will, which can be used to either augment the existing trace stream
+and/or signal that a particular important state has occurred.
+
+A similar in-kernel API is also available for creating kprobe and
+kretprobe events.
+
+Both the synthetic event and k/ret/probe event APIs are built on top
+of a lower-level "dynevent_cmd" event command API, which is also
+available for more specialized applications, or as the basis of other
+higher-level trace event APIs.
+
+The API provided for these purposes is describe below and allows the
+following:
+
+ - dynamically creating synthetic event definitions
+ - dynamically creating kprobe and kretprobe event definitions
+ - tracing synthetic events from in-kernel code
+ - the low-level "dynevent_cmd" API
+
+6.3.1 Dyamically creating synthetic event definitions
+-----------------------------------------------------
+
+There are a couple ways to create a new synthetic event from a kernel
+module or other kernel code.
+
+The first creates the event in one step, using synth_event_create().
+In this method, the name of the event to create and an array defining
+the fields is supplied to synth_event_create(). If successful, a
+synthetic event with that name and fields will exist following that
+call. For example, to create a new "schedtest" synthetic event:
+
+ ret = synth_event_create("schedtest", sched_fields,
+ ARRAY_SIZE(sched_fields), THIS_MODULE);
+
+The sched_fields param in this example points to an array of struct
+synth_field_desc, each of which describes an event field by type and
+name:
+
+ static struct synth_field_desc sched_fields[] = {
+ { .type = "pid_t", .name = "next_pid_field" },
+ { .type = "char[16]", .name = "next_comm_field" },
+ { .type = "u64", .name = "ts_ns" },
+ { .type = "u64", .name = "ts_ms" },
+ { .type = "unsigned int", .name = "cpu" },
+ { .type = "char[64]", .name = "my_string_field" },
+ { .type = "int", .name = "my_int_field" },
+ };
+
+See synth_field_size() for available types. If field_name contains [n]
+the field is considered to be an array.
+
+If the event is created from within a module, a pointer to the module
+must be passed to synth_event_create(). This will ensure that the
+trace buffer won't contain unreadable events when the module is
+removed.
+
+At this point, the event object is ready to be used for generating new
+events.
+
+In the second method, the event is created in several steps. This
+allows events to be created dynamically and without the need to create
+and populate an array of fields beforehand.
+
+To use this method, an empty or partially empty synthetic event should
+first be created using synth_event_gen_cmd_start() or
+synth_event_gen_cmd_array_start(). For synth_event_gen_cmd_start(),
+the name of the event along with one or more pairs of args each pair
+representing a 'type field_name;' field specification should be
+supplied. For synth_event_gen_cmd_array_start(), the name of the
+event along with an array of struct synth_field_desc should be
+supplied. Before calling synth_event_gen_cmd_start() or
+synth_event_gen_cmd_array_start(), the user should create and
+initialize a dynevent_cmd object using synth_event_cmd_init().
+
+For example, to create a new "schedtest" synthetic event with two
+fields:
+
+ struct dynevent_cmd cmd;
+ char *buf;
+
+ /* Create a buffer to hold the generated command */
+ buf = kzalloc(MAX_DYNEVENT_CMD_LEN, GFP_KERNEL);
+
+ /* Before generating the command, initialize the cmd object */
+ synth_event_cmd_init(&cmd, buf, MAX_DYNEVENT_CMD_LEN);
+
+ ret = synth_event_gen_cmd_start(&cmd, "schedtest", THIS_MODULE,
+ "pid_t", "next_pid_field",
+ "u64", "ts_ns");
+
+Alternatively, using an array of struct synth_field_desc fields
+containing the same information:
+
+ ret = synth_event_gen_cmd_array_start(&cmd, "schedtest", THIS_MODULE,
+ fields, n_fields);
+
+Once the synthetic event object has been created, it can then be
+populated with more fields. Fields are added one by one using
+synth_event_add_field(), supplying the dynevent_cmd object, a field
+type, and a field name. For example, to add a new int field named
+"intfield", the following call should be made:
+
+ ret = synth_event_add_field(&cmd, "int", "intfield");
+
+See synth_field_size() for available types. If field_name contains [n]
+the field is considered to be an array.
+
+A group of fields can also be added all at once using an array of
+synth_field_desc with add_synth_fields(). For example, this would add
+just the first four sched_fields:
+
+ ret = synth_event_add_fields(&cmd, sched_fields, 4);
+
+If you already have a string of the form 'type field_name',
+synth_event_add_field_str() can be used to add it as-is; it will
+also automatically append a ';' to the string.
+
+Once all the fields have been added, the event should be finalized and
+registered by calling the synth_event_gen_cmd_end() function:
+
+ ret = synth_event_gen_cmd_end(&cmd);
+
+At this point, the event object is ready to be used for tracing new
+events.
+
+6.3.3 Tracing synthetic events from in-kernel code
+--------------------------------------------------
+
+To trace a synthetic event, there are several options. The first
+option is to trace the event in one call, using synth_event_trace()
+with a variable number of values, or synth_event_trace_array() with an
+array of values to be set. A second option can be used to avoid the
+need for a pre-formed array of values or list of arguments, via
+synth_event_trace_start() and synth_event_trace_end() along with
+synth_event_add_next_val() or synth_event_add_val() to add the values
+piecewise.
+
+6.3.3.1 Tracing a synthetic event all at once
+---------------------------------------------
+
+To trace a synthetic event all at once, the synth_event_trace() or
+synth_event_trace_array() functions can be used.
+
+The synth_event_trace() function is passed the trace_event_file
+representing the synthetic event (which can be retrieved using
+trace_get_event_file() using the synthetic event name, "synthetic" as
+the system name, and the trace instance name (NULL if using the global
+trace array)), along with an variable number of u64 args, one for each
+synthetic event field, and the number of values being passed.
+
+So, to trace an event corresponding to the synthetic event definition
+above, code like the following could be used:
+
+ ret = synth_event_trace(create_synth_test, 7, /* number of values */
+ 444, /* next_pid_field */
+ (u64)"clackers", /* next_comm_field */
+ 1000000, /* ts_ns */
+ 1000, /* ts_ms */
+ smp_processor_id(),/* cpu */
+ (u64)"Thneed", /* my_string_field */
+ 999); /* my_int_field */
+
+All vals should be cast to u64, and string vals are just pointers to
+strings, cast to u64. Strings will be copied into space reserved in
+the event for the string, using these pointers.
+
+Alternatively, the synth_event_trace_array() function can be used to
+accomplish the same thing. It is passed the trace_event_file
+representing the synthetic event (which can be retrieved using
+trace_get_event_file() using the synthetic event name, "synthetic" as
+the system name, and the trace instance name (NULL if using the global
+trace array)), along with an array of u64, one for each synthetic
+event field.
+
+To trace an event corresponding to the synthetic event definition
+above, code like the following could be used:
+
+ u64 vals[7];
+
+ vals[0] = 777; /* next_pid_field */
+ vals[1] = (u64)"tiddlywinks"; /* next_comm_field */
+ vals[2] = 1000000; /* ts_ns */
+ vals[3] = 1000; /* ts_ms */
+ vals[4] = smp_processor_id(); /* cpu */
+ vals[5] = (u64)"thneed"; /* my_string_field */
+ vals[6] = 398; /* my_int_field */
+
+The 'vals' array is just an array of u64, the number of which must
+match the number of field in the synthetic event, and which must be in
+the same order as the synthetic event fields.
+
+All vals should be cast to u64, and string vals are just pointers to
+strings, cast to u64. Strings will be copied into space reserved in
+the event for the string, using these pointers.
+
+In order to trace a synthetic event, a pointer to the trace event file
+is needed. The trace_get_event_file() function can be used to get
+it - it will find the file in the given trace instance (in this case
+NULL since the top trace array is being used) while at the same time
+preventing the instance containing it from going away:
+
+ schedtest_event_file = trace_get_event_file(NULL, "synthetic",
+ "schedtest");
+
+Before tracing the event, it should be enabled in some way, otherwise
+the synthetic event won't actually show up in the trace buffer.
+
+To enable a synthetic event from the kernel, trace_array_set_clr_event()
+can be used (which is not specific to synthetic events, so does need
+the "synthetic" system name to be specified explicitly).
+
+To enable the event, pass 'true' to it:
+
+ trace_array_set_clr_event(schedtest_event_file->tr,
+ "synthetic", "schedtest", true);
+
+To disable it pass false:
+
+ trace_array_set_clr_event(schedtest_event_file->tr,
+ "synthetic", "schedtest", false);
+
+Finally, synth_event_trace_array() can be used to actually trace the
+event, which should be visible in the trace buffer afterwards:
+
+ ret = synth_event_trace_array(schedtest_event_file, vals,
+ ARRAY_SIZE(vals));
+
+To remove the synthetic event, the event should be disabled, and the
+trace instance should be 'put' back using trace_put_event_file():
+
+ trace_array_set_clr_event(schedtest_event_file->tr,
+ "synthetic", "schedtest", false);
+ trace_put_event_file(schedtest_event_file);
+
+If those have been successful, synth_event_delete() can be called to
+remove the event:
+
+ ret = synth_event_delete("schedtest");
+
+6.3.3.1 Tracing a synthetic event piecewise
+-------------------------------------------
+
+To trace a synthetic using the piecewise method described above, the
+synth_event_trace_start() function is used to 'open' the synthetic
+event trace:
+
+ struct synth_trace_state trace_state;
+
+ ret = synth_event_trace_start(schedtest_event_file, &trace_state);
+
+It's passed the trace_event_file representing the synthetic event
+using the same methods as described above, along with a pointer to a
+struct synth_trace_state object, which will be zeroed before use and
+used to maintain state between this and following calls.
+
+Once the event has been opened, which means space for it has been
+reserved in the trace buffer, the individual fields can be set. There
+are two ways to do that, either one after another for each field in
+the event, which requires no lookups, or by name, which does. The
+tradeoff is flexibility in doing the assignments vs the cost of a
+lookup per field.
+
+To assign the values one after the other without lookups,
+synth_event_add_next_val() should be used. Each call is passed the
+same synth_trace_state object used in the synth_event_trace_start(),
+along with the value to set the next field in the event. After each
+field is set, the 'cursor' points to the next field, which will be set
+by the subsequent call, continuing until all the fields have been set
+in order. The same sequence of calls as in the above examples using
+this method would be (without error-handling code):
+
+ /* next_pid_field */
+ ret = synth_event_add_next_val(777, &trace_state);
+
+ /* next_comm_field */
+ ret = synth_event_add_next_val((u64)"slinky", &trace_state);
+
+ /* ts_ns */
+ ret = synth_event_add_next_val(1000000, &trace_state);
+
+ /* ts_ms */
+ ret = synth_event_add_next_val(1000, &trace_state);
+
+ /* cpu */
+ ret = synth_event_add_next_val(smp_processor_id(), &trace_state);
+
+ /* my_string_field */
+ ret = synth_event_add_next_val((u64)"thneed_2.01", &trace_state);
+
+ /* my_int_field */
+ ret = synth_event_add_next_val(395, &trace_state);
+
+To assign the values in any order, synth_event_add_val() should be
+used. Each call is passed the same synth_trace_state object used in
+the synth_event_trace_start(), along with the field name of the field
+to set and the value to set it to. The same sequence of calls as in
+the above examples using this method would be (without error-handling
+code):
+
+ ret = synth_event_add_val("next_pid_field", 777, &trace_state);
+ ret = synth_event_add_val("next_comm_field", (u64)"silly putty",
+ &trace_state);
+ ret = synth_event_add_val("ts_ns", 1000000, &trace_state);
+ ret = synth_event_add_val("ts_ms", 1000, &trace_state);
+ ret = synth_event_add_val("cpu", smp_processor_id(), &trace_state);
+ ret = synth_event_add_val("my_string_field", (u64)"thneed_9",
+ &trace_state);
+ ret = synth_event_add_val("my_int_field", 3999, &trace_state);
+
+Note that synth_event_add_next_val() and synth_event_add_val() are
+incompatible if used within the same trace of an event - either one
+can be used but not both at the same time.
+
+Finally, the event won't be actually traced until it's 'closed',
+which is done using synth_event_trace_end(), which takes only the
+struct synth_trace_state object used in the previous calls:
+
+ ret = synth_event_trace_end(&trace_state);
+
+Note that synth_event_trace_end() must be called at the end regardless
+of whether any of the add calls failed (say due to a bad field name
+being passed in).
+
+6.3.4 Dyamically creating kprobe and kretprobe event definitions
+----------------------------------------------------------------
+
+To create a kprobe or kretprobe trace event from kernel code, the
+kprobe_event_gen_cmd_start() or kretprobe_event_gen_cmd_start()
+functions can be used.
+
+To create a kprobe event, an empty or partially empty kprobe event
+should first be created using kprobe_event_gen_cmd_start(). The name
+of the event and the probe location should be specfied along with one
+or args each representing a probe field should be supplied to this
+function. Before calling kprobe_event_gen_cmd_start(), the user
+should create and initialize a dynevent_cmd object using
+kprobe_event_cmd_init().
+
+For example, to create a new "schedtest" kprobe event with two fields:
+
+ struct dynevent_cmd cmd;
+ char *buf;
+
+ /* Create a buffer to hold the generated command */
+ buf = kzalloc(MAX_DYNEVENT_CMD_LEN, GFP_KERNEL);
+
+ /* Before generating the command, initialize the cmd object */
+ kprobe_event_cmd_init(&cmd, buf, MAX_DYNEVENT_CMD_LEN);
+
+ /*
+ * Define the gen_kprobe_test event with the first 2 kprobe
+ * fields.
+ */
+ ret = kprobe_event_gen_cmd_start(&cmd, "gen_kprobe_test", "do_sys_open",
+ "dfd=%ax", "filename=%dx");
+
+Once the kprobe event object has been created, it can then be
+populated with more fields. Fields can be added using
+kprobe_event_add_fields(), supplying the dynevent_cmd object along
+with a variable arg list of probe fields. For example, to add a
+couple additional fields, the following call could be made:
+
+ ret = kprobe_event_add_fields(&cmd, "flags=%cx", "mode=+4($stack)");
+
+Once all the fields have been added, the event should be finalized and
+registered by calling the kprobe_event_gen_cmd_end() or
+kretprobe_event_gen_cmd_end() functions, depending on whether a kprobe
+or kretprobe command was started:
+
+ ret = kprobe_event_gen_cmd_end(&cmd);
+
+or
+
+ ret = kretprobe_event_gen_cmd_end(&cmd);
+
+At this point, the event object is ready to be used for tracing new
+events.
+
+Similarly, a kretprobe event can be created using
+kretprobe_event_gen_cmd_start() with a probe name and location and
+additional params such as $retval:
+
+ ret = kretprobe_event_gen_cmd_start(&cmd, "gen_kretprobe_test",
+ "do_sys_open", "$retval");
+
+Similar to the synthetic event case, code like the following can be
+used to enable the newly created kprobe event:
+
+ gen_kprobe_test = trace_get_event_file(NULL, "kprobes", "gen_kprobe_test");
+
+ ret = trace_array_set_clr_event(gen_kprobe_test->tr,
+ "kprobes", "gen_kprobe_test", true);
+
+Finally, also similar to synthetic events, the following code can be
+used to give the kprobe event file back and delete the event:
+
+ trace_put_event_file(gen_kprobe_test);
+
+ ret = kprobe_event_delete("gen_kprobe_test");
+
+6.3.4 The "dynevent_cmd" low-level API
+--------------------------------------
+
+Both the in-kernel synthetic event and kprobe interfaces are built on
+top of a lower-level "dynevent_cmd" interface. This interface is
+meant to provide the basis for higher-level interfaces such as the
+synthetic and kprobe interfaces, which can be used as examples.
+
+The basic idea is simple and amounts to providing a general-purpose
+layer that can be used to generate trace event commands. The
+generated command strings can then be passed to the command-parsing
+and event creation code that already exists in the trace event
+subystem for creating the corresponding trace events.
+
+In a nutshell, the way it works is that the higher-level interface
+code creates a struct dynevent_cmd object, then uses a couple
+functions, dynevent_arg_add() and dynevent_arg_pair_add() to build up
+a command string, which finally causes the command to be executed
+using the dynevent_create() function. The details of the interface
+are described below.
+
+The first step in building a new command string is to create and
+initialize an instance of a dynevent_cmd. Here, for instance, we
+create a dynevent_cmd on the stack and initialize it:
+
+ struct dynevent_cmd cmd;
+ char *buf;
+ int ret;
+
+ buf = kzalloc(MAX_DYNEVENT_CMD_LEN, GFP_KERNEL);
+
+ dynevent_cmd_init(cmd, buf, maxlen, DYNEVENT_TYPE_FOO,
+ foo_event_run_command);
+
+The dynevent_cmd initialization needs to be given a user-specified
+buffer and the length of the buffer (MAX_DYNEVENT_CMD_LEN can be used
+for this purpose - at 2k it's generally too big to be comfortably put
+on the stack, so is dynamically allocated), a dynevent type id, which
+is meant to be used to check that further API calls are for the
+correct command type, and a pointer to an event-specific run_command()
+callback that will be called to actually execute the event-specific
+command function.
+
+Once that's done, the command string can by built up by successive
+calls to argument-adding functions.
+
+To add a single argument, define and initialize a struct dynevent_arg
+or struct dynevent_arg_pair object. Here's an example of the simplest
+possible arg addition, which is simply to append the given string as
+a whitespace-separated argument to the command:
+
+ struct dynevent_arg arg;
+
+ dynevent_arg_init(&arg, NULL, 0);
+
+ arg.str = name;
+
+ ret = dynevent_arg_add(cmd, &arg);
+
+The arg object is first initialized using dynevent_arg_init() and in
+this case the parameters are NULL or 0, which means there's no
+optional sanity-checking function or separator appended to the end of
+the arg.
+
+Here's another more complicated example using an 'arg pair', which is
+used to create an argument that consists of a couple components added
+together as a unit, for example, a 'type field_name;' arg or a simple
+expression arg e.g. 'flags=%cx':
+
+ struct dynevent_arg_pair arg_pair;
+
+ dynevent_arg_pair_init(&arg_pair, dynevent_foo_check_arg_fn, 0, ';');
+
+ arg_pair.lhs = type;
+ arg_pair.rhs = name;
+
+ ret = dynevent_arg_pair_add(cmd, &arg_pair);
+
+Again, the arg_pair is first initialized, in this case with a callback
+function used to check the sanity of the args (for example, that
+neither part of the pair is NULL), along with a character to be used
+to add an operator between the pair (here none) and a separator to be
+appended onto the end of the arg pair (here ';').
+
+There's also a dynevent_str_add() function that can be used to simply
+add a string as-is, with no spaces, delimeters, or arg check.
+
+Any number of dynevent_*_add() calls can be made to build up the string
+(until its length surpasses cmd->maxlen). When all the arguments have
+been added and the command string is complete, the only thing left to
+do is run the command, which happens by simply calling
+dynevent_create():
+
+ ret = dynevent_create(&cmd);
+
+At that point, if the return value is 0, the dynamic event has been
+created and is ready to use.
+
+See the dynevent_cmd function definitions themselves for the details
+of the API.
diff --git a/Documentation/trace/index.rst b/Documentation/trace/index.rst
index 04acd277c5f6..fa9e1c730f6a 100644
--- a/Documentation/trace/index.rst
+++ b/Documentation/trace/index.rst
@@ -19,6 +19,7 @@ Linux Tracing Technologies
events-msr
mmiotrace
histogram
+ boottime-trace
hwlat_detector
intel_th
stm
diff --git a/Documentation/trace/kprobetrace.rst b/Documentation/trace/kprobetrace.rst
index 55993055902c..705d73087099 100644
--- a/Documentation/trace/kprobetrace.rst
+++ b/Documentation/trace/kprobetrace.rst
@@ -97,6 +97,7 @@ which shows given pointer in "symbol+offset" style.
For $comm, the default type is "string"; any other type is invalid.
.. _user_mem_access:
+
User Memory Access
------------------
Kprobe events supports user-space memory access. For that purpose, you can use