Merge tag 'trace-v6.0' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

Pull tracing updates from Steven Rostedt:

 - Runtime verification infrastructure

   This is the biggest change here. It introduces the runtime
   verification that is necessary for running Linux on safety critical
   systems.

   It allows for deterministic automata models to be inserted into the
   kernel that will attach to tracepoints, where the information on
   these tracepoints will move the model from state to state.

   If a state is encountered that does not belong to the model, it will
   then activate a given reactor, that could just inform the user or
   even panic the kernel (for which safety critical systems will detect
   and can recover from).

 - Two monitor models are also added: Wakeup In Preemptive (WIP - not to
   be confused with "work in progress"), and Wakeup While Not Running
   (WWNR).

 - Added __vstring() helper to the TRACE_EVENT() macro to replace
   several vsnprintf() usages that were all doing it wrong.

 - eprobes now can have their event autogenerated when the event name is
   left off.

 - The rest is various cleanups and fixes.

* tag 'trace-v6.0' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: (50 commits)
  rv: Unlock on error path in rv_unregister_reactor()
  tracing: Use alignof__(struct {type b;}) instead of offsetof()
  tracing/eprobe: Show syntax error logs in error_log file
  scripts/tracing: Fix typo 'the the' in comment
  tracepoints: It is CONFIG_TRACEPOINTS not CONFIG_TRACEPOINT
  tracing: Use free_trace_buffer() in allocate_trace_buffers()
  tracing: Use a struct alignof to determine trace event field alignment
  rv/reactor: Add the panic reactor
  rv/reactor: Add the printk reactor
  rv/monitor: Add the wwnr monitor
  rv/monitor: Add the wip monitor
  rv/monitor: Add the wip monitor skeleton created by dot2k
  Documentation/rv: Add deterministic automata instrumentation documentation
  Documentation/rv: Add deterministic automata monitor synthesis documentation
  tools/rv: Add dot2k
  Documentation/rv: Add deterministic automaton documentation
  tools/rv: Add dot2c
  Documentation/rv: Add a basic documentation
  rv/include: Add instrumentation helper functions
  rv/include: Add deterministic automata monitor definition via C macros
  ...

10 files changed, 856 insertions, 8 deletions

diff --git a/Documentation/trace/index.rst b/Documentation/trace/index.rst
index f9b7bcb5a6302..2d73e8697523e 100644
--- a/Documentation/trace/index.rst
+++ b/Documentation/trace/index.rst
@@ -32,3 +32,4 @@ Linux Tracing Technologies
    sys-t
    coresight/index
    user_events
+   rv/index
diff --git a/Documentation/trace/kprobetrace.rst b/Documentation/trace/kprobetrace.rst
index b175d88f31ebb..4274cc6a2f94f 100644
--- a/Documentation/trace/kprobetrace.rst
+++ b/Documentation/trace/kprobetrace.rst
@@ -28,10 +28,10 @@ Synopsis of kprobe_events
 -------------------------
 ::
 
-  p[:[GRP/]EVENT] [MOD:]SYM[+offs]|MEMADDR [FETCHARGS]	: Set a probe
-  r[MAXACTIVE][:[GRP/]EVENT] [MOD:]SYM[+0] [FETCHARGS]	: Set a return probe
-  p:[GRP/]EVENT] [MOD:]SYM[+0]%return [FETCHARGS]	: Set a return probe
-  -:[GRP/]EVENT						: Clear a probe
+  p[:[GRP/][EVENT]] [MOD:]SYM[+offs]|MEMADDR [FETCHARGS]	: Set a probe
+  r[MAXACTIVE][:[GRP/][EVENT]] [MOD:]SYM[+0] [FETCHARGS]	: Set a return probe
+  p[:[GRP/][EVENT]] [MOD:]SYM[+0]%return [FETCHARGS]	: Set a return probe
+  -:[GRP/][EVENT]						: Clear a probe
 
  GRP		: Group name. If omitted, use "kprobes" for it.
  EVENT		: Event name. If omitted, the event name is generated
diff --git a/Documentation/trace/rv/da_monitor_instrumentation.rst b/Documentation/trace/rv/da_monitor_instrumentation.rst
new file mode 100644
index 0000000000000..6c67c7b578111
--- /dev/null
+++ b/Documentation/trace/rv/da_monitor_instrumentation.rst
@@ -0,0 +1,171 @@
+Deterministic Automata Instrumentation
+======================================
+
+The RV monitor file created by dot2k, with the name "$MODEL_NAME.c"
+includes a section dedicated to instrumentation.
+
+In the example of the wip.dot monitor created on [1], it will look like::
+
+  /*
+   * This is the instrumentation part of the monitor.
+   *
+   * This is the section where manual work is required. Here the kernel events
+   * are translated into model's event.
+   *
+   */
+  static void handle_preempt_disable(void *data, /* XXX: fill header */)
+  {
+	da_handle_event_wip(preempt_disable_wip);
+  }
+
+  static void handle_preempt_enable(void *data, /* XXX: fill header */)
+  {
+	da_handle_event_wip(preempt_enable_wip);
+  }
+
+  static void handle_sched_waking(void *data, /* XXX: fill header */)
+  {
+	da_handle_event_wip(sched_waking_wip);
+  }
+
+  static int enable_wip(void)
+  {
+	int retval;
+
+	retval = da_monitor_init_wip();
+	if (retval)
+		return retval;
+
+	rv_attach_trace_probe("wip", /* XXX: tracepoint */, handle_preempt_disable);
+	rv_attach_trace_probe("wip", /* XXX: tracepoint */, handle_preempt_enable);
+	rv_attach_trace_probe("wip", /* XXX: tracepoint */, handle_sched_waking);
+
+	return 0;
+  }
+
+The comment at the top of the section explains the general idea: the
+instrumentation section translates *kernel events* into the *model's
+event*.
+
+Tracing callback functions
+--------------------------
+
+The first three functions are the starting point of the callback *handler
+functions* for each of the three events from the wip model. The developer
+does not necessarily need to use them: they are just starting points.
+
+Using the example of::
+
+ void handle_preempt_disable(void *data, /* XXX: fill header */)
+ {
+        da_handle_event_wip(preempt_disable_wip);
+ }
+
+The preempt_disable event from the model connects directly to the
+preemptirq:preempt_disable. The preemptirq:preempt_disable event
+has the following signature, from include/trace/events/preemptirq.h::
+
+  TP_PROTO(unsigned long ip, unsigned long parent_ip)
+
+Hence, the handle_preempt_disable() function will look like::
+
+  void handle_preempt_disable(void *data, unsigned long ip, unsigned long parent_ip)
+
+In this case, the kernel event translates one to one with the automata
+event, and indeed, no other change is required for this function.
+
+The next handler function, handle_preempt_enable() has the same argument
+list from the handle_preempt_disable(). The difference is that the
+preempt_enable event will be used to synchronize the system to the model.
+
+Initially, the *model* is placed in the initial state. However, the *system*
+might or might not be in the initial state. The monitor cannot start
+processing events until it knows that the system has reached the initial state.
+Otherwise, the monitor and the system could be out-of-sync.
+
+Looking at the automata definition, it is possible to see that the system
+and the model are expected to return to the initial state after the
+preempt_enable execution. Hence, it can be used to synchronize the
+system and the model at the initialization of the monitoring section.
+
+The start is informed via a special handle function, the
+"da_handle_start_event_$(MONITOR_NAME)(event)", in this case::
+
+  da_handle_start_event_wip(preempt_enable_wip);
+
+So, the callback function will look like::
+
+  void handle_preempt_enable(void *data, unsigned long ip, unsigned long parent_ip)
+  {
+        da_handle_start_event_wip(preempt_enable_wip);
+  }
+
+Finally, the "handle_sched_waking()" will look like::
+
+  void handle_sched_waking(void *data, struct task_struct *task)
+  {
+        da_handle_event_wip(sched_waking_wip);
+  }
+
+And the explanation is left for the reader as an exercise.
+
+enable and disable functions
+----------------------------
+
+dot2k automatically creates two special functions::
+
+  enable_$(MONITOR_NAME)()
+  disable_$(MONITOR_NAME)()
+
+These functions are called when the monitor is enabled and disabled,
+respectively.
+
+They should be used to *attach* and *detach* the instrumentation to the running
+system. The developer must add to the relative function all that is needed to
+*attach* and *detach* its monitor to the system.
+
+For the wip case, these functions were named::
+
+ enable_wip()
+ disable_wip()
+
+But no change was required because: by default, these functions *attach* and
+*detach* the tracepoints_to_attach, which was enough for this case.
+
+Instrumentation helpers
+-----------------------
+
+To complete the instrumentation, the *handler functions* need to be attached to a
+kernel event, at the monitoring enable phase.
+
+The RV interface also facilitates this step. For example, the macro "rv_attach_trace_probe()"
+is used to connect the wip model events to the relative kernel event. dot2k automatically
+adds "rv_attach_trace_probe()" function call for each model event in the enable phase, as
+a suggestion.
+
+For example, from the wip sample model::
+
+  static int enable_wip(void)
+  {
+        int retval;
+
+        retval = da_monitor_init_wip();
+        if (retval)
+                return retval;
+
+        rv_attach_trace_probe("wip", /* XXX: tracepoint */, handle_preempt_enable);
+        rv_attach_trace_probe("wip", /* XXX: tracepoint */, handle_sched_waking);
+        rv_attach_trace_probe("wip", /* XXX: tracepoint */, handle_preempt_disable);
+
+        return 0;
+  }
+
+The probes then need to be detached at the disable phase.
+
+[1] The wip model is presented in::
+
+  Documentation/trace/rv/deterministic_automata.rst
+
+The wip monitor is presented in::
+
+  Documentation/trace/rv/da_monitor_synthesis.rst
diff --git a/Documentation/trace/rv/da_monitor_synthesis.rst b/Documentation/trace/rv/da_monitor_synthesis.rst
new file mode 100644
index 0000000000000..0dbdcd1e62b90
--- /dev/null
+++ b/Documentation/trace/rv/da_monitor_synthesis.rst
@@ -0,0 +1,147 @@
+Deterministic Automata Monitor Synthesis
+========================================
+
+The starting point for the application of runtime verification (RV) technics
+is the *specification* or *modeling* of the desired (or undesired) behavior
+of the system under scrutiny.
+
+The formal representation needs to be then *synthesized* into a *monitor*
+that can then be used in the analysis of the trace of the system. The
+*monitor* connects to the system via an *instrumentation* that converts
+the events from the *system* to the events of the *specification*.
+
+
+In Linux terms, the runtime verification monitors are encapsulated inside
+the *RV monitor* abstraction. The RV monitor includes a set of instances
+of the monitor (per-cpu monitor, per-task monitor, and so on), the helper
+functions that glue the monitor to the system reference model, and the
+trace output as a reaction to event parsing and exceptions, as depicted
+below::
+
+ Linux  +----- RV Monitor ----------------------------------+ Formal
+  Realm |                                                   |  Realm
+  +-------------------+     +----------------+     +-----------------+
+  |   Linux kernel    |     |     Monitor    |     |     Reference   |
+  |     Tracing       |  -> |   Instance(s)  | <-  |       Model     |
+  | (instrumentation) |     | (verification) |     | (specification) |
+  +-------------------+     +----------------+     +-----------------+
+         |                          |                       |
+         |                          V                       |
+         |                     +----------+                 |
+         |                     | Reaction |                 |
+         |                     +--+--+--+-+                 |
+         |                        |  |  |                   |
+         |                        |  |  +-> trace output ?  |
+         +------------------------|--|----------------------+
+                                  |  +----> panic ?
+                                  +-------> <user-specified>
+
+DA monitor synthesis
+--------------------
+
+The synthesis of automata-based models into the Linux *RV monitor* abstraction
+is automated by the dot2k tool and the rv/da_monitor.h header file that
+contains a set of macros that automatically generate the monitor's code.
+
+dot2k
+-----
+
+The dot2k utility leverages dot2c by converting an automaton model in
+the DOT format into the C representation [1] and creating the skeleton of
+a kernel monitor in C.
+
+For example, it is possible to transform the wip.dot model present in
+[1] into a per-cpu monitor with the following command::
+
+  $ dot2k -d wip.dot -t per_cpu
+
+This will create a directory named wip/ with the following files:
+
+- wip.h: the wip model in C
+- wip.c: the RV monitor
+
+The wip.c file contains the monitor declaration and the starting point for
+the system instrumentation.
+
+Monitor macros
+--------------
+
+The rv/da_monitor.h enables automatic code generation for the *Monitor
+Instance(s)* using C macros.
+
+The benefits of the usage of macro for monitor synthesis are 3-fold as it:
+
+- Reduces the code duplication;
+- Facilitates the bug fix/improvement;
+- Avoids the case of developers changing the core of the monitor code
+  to manipulate the model in a (let's say) non-standard way.
+
+This initial implementation presents three different types of monitor instances:
+
+- ``#define DECLARE_DA_MON_GLOBAL(name, type)``
+- ``#define DECLARE_DA_MON_PER_CPU(name, type)``
+- ``#define DECLARE_DA_MON_PER_TASK(name, type)``
+
+The first declares the functions for a global deterministic automata monitor,
+the second for monitors with per-cpu instances, and the third with per-task
+instances.
+
+In all cases, the 'name' argument is a string that identifies the monitor, and
+the 'type' argument is the data type used by dot2k on the representation of
+the model in C.
+
+For example, the wip model with two states and three events can be
+stored in an 'unsigned char' type. Considering that the preemption control
+is a per-cpu behavior, the monitor declaration in the 'wip.c' file is::
+
+  DECLARE_DA_MON_PER_CPU(wip, unsigned char);
+
+The monitor is executed by sending events to be processed via the functions
+presented below::
+
+  da_handle_event_$(MONITOR_NAME)($(event from event enum));
+  da_handle_start_event_$(MONITOR_NAME)($(event from event enum));
+  da_handle_start_run_event_$(MONITOR_NAME)($(event from event enum));
+
+The function ``da_handle_event_$(MONITOR_NAME)()`` is the regular case where
+the event will be processed if the monitor is processing events.
+
+When a monitor is enabled, it is placed in the initial state of the automata.
+However, the monitor does not know if the system is in the *initial state*.
+
+The ``da_handle_start_event_$(MONITOR_NAME)()`` function is used to notify the
+monitor that the system is returning to the initial state, so the monitor can
+start monitoring the next event.
+
+The ``da_handle_start_run_event_$(MONITOR_NAME)()`` function is used to notify
+the monitor that the system is known to be in the initial state, so the
+monitor can start monitoring and monitor the current event.
+
+Using the wip model as example, the events "preempt_disable" and
+"sched_waking" should be sent to monitor, respectively, via [2]::
+
+  da_handle_event_wip(preempt_disable_wip);
+  da_handle_event_wip(sched_waking_wip);
+
+While the event "preempt_enabled" will use::
+
+  da_handle_start_event_wip(preempt_enable_wip);
+
+To notify the monitor that the system will be returning to the initial state,
+so the system and the monitor should be in sync.
+
+Final remarks
+-------------
+
+With the monitor synthesis in place using the rv/da_monitor.h and
+dot2k, the developer's work should be limited to the instrumentation
+of the system, increasing the confidence in the overall approach.
+
+[1] For details about deterministic automata format and the translation
+from one representation to another, see::
+
+  Documentation/trace/rv/deterministic_automata.rst
+
+[2] dot2k appends the monitor's name suffix to the events enums to
+avoid conflicting variables when exporting the global vmlinux.h
+use by BPF programs.
diff --git a/Documentation/trace/rv/deterministic_automata.rst b/Documentation/trace/rv/deterministic_automata.rst
new file mode 100644
index 0000000000000..d0638f95a455e
--- /dev/null
+++ b/Documentation/trace/rv/deterministic_automata.rst
@@ -0,0 +1,184 @@
+Deterministic Automata
+======================
+
+Formally, a deterministic automaton, denoted by G, is defined as a quintuple:
+
+        *G* = { *X*, *E*, *f*, x\ :subscript:`0`, X\ :subscript:`m` }
+
+where:
+
+- *X* is the set of states;
+- *E* is the finite set of events;
+- x\ :subscript:`0` is the initial state;
+- X\ :subscript:`m` (subset of *X*) is the set of marked (or final) states.
+- *f* : *X* x *E* -> *X* $ is the transition function. It defines the state
+  transition in the occurrence of an event from *E* in the state *X*. In the
+  special case of deterministic automata, the occurrence of the event in *E*
+  in a state in *X* has a deterministic next state from *X*.
+
+For example, a given automaton named 'wip' (wakeup in preemptive) can
+be defined as:
+
+- *X* = { ``preemptive``, ``non_preemptive``}
+- *E* = { ``preempt_enable``, ``preempt_disable``, ``sched_waking``}
+- x\ :subscript:`0` = ``preemptive``
+- X\ :subscript:`m` = {``preemptive``}
+- *f* =
+   - *f*\ (``preemptive``, ``preempt_disable``) = ``non_preemptive``
+   - *f*\ (``non_preemptive``, ``sched_waking``) = ``non_preemptive``
+   - *f*\ (``non_preemptive``, ``preempt_enable``) = ``preemptive``
+
+One of the benefits of this formal definition is that it can be presented
+in multiple formats. For example, using a *graphical representation*, using
+vertices (nodes) and edges, which is very intuitive for *operating system*
+practitioners, without any loss.
+
+The previous 'wip' automaton can also be represented as::
+
+                       preempt_enable
+          +---------------------------------+
+          v                                 |
+        #============#  preempt_disable   +------------------+
+    --> H preemptive H -----------------> |  non_preemptive  |
+        #============#                    +------------------+
+                                            ^              |
+                                            | sched_waking |
+                                            +--------------+
+
+Deterministic Automaton in C
+----------------------------
+
+In the paper "Efficient formal verification for the Linux kernel",
+the authors present a simple way to represent an automaton in C that can
+be used as regular code in the Linux kernel.
+
+For example, the 'wip' automata can be presented as (augmented with comments)::
+
+  /* enum representation of X (set of states) to be used as index */
+  enum states {
+	preemptive = 0,
+	non_preemptive,
+	state_max
+  };
+
+  #define INVALID_STATE state_max
+
+  /* enum representation of E (set of events) to be used as index */
+  enum events {
+	preempt_disable = 0,
+	preempt_enable,
+	sched_waking,
+	event_max
+  };
+
+  struct automaton {
+	char *state_names[state_max];                   // X: the set of states
+	char *event_names[event_max];                   // E: the finite set of events
+	unsigned char function[state_max][event_max];   // f: transition function
+	unsigned char initial_state;                    // x_0: the initial state
+	bool final_states[state_max];                   // X_m: the set of marked states
+  };
+
+  struct automaton aut = {
+	.state_names = {
+		"preemptive",
+		"non_preemptive"
+	},
+	.event_names = {
+		"preempt_disable",
+		"preempt_enable",
+		"sched_waking"
+	},
+	.function = {
+		{ non_preemptive,  INVALID_STATE,  INVALID_STATE },
+		{  INVALID_STATE,     preemptive, non_preemptive },
+	},
+	.initial_state = preemptive,
+	.final_states = { 1, 0 },
+  };
+
+The *transition function* is represented as a matrix of states (lines) and
+events (columns), and so the function *f* : *X* x *E* -> *X* can be solved
+in O(1). For example::
+
+  next_state = automaton_wip.function[curr_state][event];
+
+Graphviz .dot format
+--------------------
+
+The Graphviz open-source tool can produce the graphical representation
+of an automaton using the (textual) DOT language as the source code.
+The DOT format is widely used and can be converted to many other formats.
+
+For example, this is the 'wip' model in DOT::
+
+  digraph state_automaton {
+        {node [shape = circle] "non_preemptive"};
+        {node [shape = plaintext, style=invis, label=""] "__init_preemptive"};
+        {node [shape = doublecircle] "preemptive"};
+        {node [shape = circle] "preemptive"};
+        "__init_preemptive" -> "preemptive";
+        "non_preemptive" [label = "non_preemptive"];
+        "non_preemptive" -> "non_preemptive" [ label = "sched_waking" ];
+        "non_preemptive" -> "preemptive" [ label = "preempt_enable" ];
+        "preemptive" [label = "preemptive"];
+        "preemptive" -> "non_preemptive" [ label = "preempt_disable" ];
+        { rank = min ;
+                "__init_preemptive";
+                "preemptive";
+        }
+  }
+
+This DOT format can be transformed into a bitmap or vectorial image
+using the dot utility, or into an ASCII art using graph-easy. For
+instance::
+
+  $ dot -Tsvg -o wip.svg wip.dot
+  $ graph-easy wip.dot > wip.txt
+
+dot2c
+-----
+
+dot2c is a utility that can parse a .dot file containing an automaton as
+in the example above and automatically convert it to the C representation
+presented in [3].
+
+For example, having the previous 'wip' model into a file named 'wip.dot',
+the following command will transform the .dot file into the C
+representation (previously shown) in the 'wip.h' file::
+
+  $ dot2c wip.dot > wip.h
+
+The 'wip.h' content is the code sample in section 'Deterministic Automaton
+in C'.
+
+Remarks
+-------
+
+The automata formalism allows modeling discrete event systems (DES) in
+multiple formats, suitable for different applications/users.
+
+For example, the formal description using set theory is better suitable
+for automata operations, while the graphical format for human interpretation;
+and computer languages for machine execution.
+
+References
+----------
+
+Many textbooks cover automata formalism. For a brief introduction see::
+
+  O'Regan, Gerard. Concise guide to software engineering. Springer,
+  Cham, 2017.
+
+For a detailed description, including operations, and application on Discrete
+Event Systems (DES), see::
+
+  Cassandras, Christos G., and Stephane Lafortune, eds. Introduction to discrete
+  event systems. Boston, MA: Springer US, 2008.
+
+For the C representation in kernel, see::
+
+  De Oliveira, Daniel Bristot; Cucinotta, Tommaso; De Oliveira, Romulo
+  Silva. Efficient formal verification for the Linux kernel. In:
+  International Conference on Software Engineering and Formal Methods.
+  Springer, Cham, 2019. p. 315-332.
diff --git a/Documentation/trace/rv/index.rst b/Documentation/trace/rv/index.rst
new file mode 100644
index 0000000000000..15fa966102c01
--- /dev/null
+++ b/Documentation/trace/rv/index.rst
@@ -0,0 +1,14 @@
+====================
+Runtime Verification
+====================
+
+.. toctree::
+   :maxdepth: 2
+   :glob:
+
+   runtime-verification.rst
+   deterministic_automata.rst
+   da_monitor_synthesis.rst
+   da_monitor_instrumentation.rst
+   monitor_wip.rst
+   monitor_wwnr.rst
diff --git a/Documentation/trace/rv/monitor_wip.rst b/Documentation/trace/rv/monitor_wip.rst
new file mode 100644
index 0000000000000..a95763438c482
--- /dev/null
+++ b/Documentation/trace/rv/monitor_wip.rst
@@ -0,0 +1,55 @@
+Monitor wip
+===========
+
+- Name: wip - wakeup in preemptive
+- Type: per-cpu deterministic automaton
+- Author: Daniel Bristot de Oliveira <bristot@kernel.org>
+
+Description
+-----------
+
+The wakeup in preemptive (wip) monitor is a sample per-cpu monitor
+that verifies if the wakeup events always take place with
+preemption disabled::
+
+                     |
+                     |
+                     v
+                   #==================#
+                   H    preemptive    H <+
+                   #==================#  |
+                     |                   |
+                     | preempt_disable   | preempt_enable
+                     v                   |
+    sched_waking   +------------------+  |
+  +--------------- |                  |  |
+  |                |  non_preemptive  |  |
+  +--------------> |                  | -+
+                   +------------------+
+
+The wakeup event always takes place with preemption disabled because
+of the scheduler synchronization. However, because the preempt_count
+and its trace event are not atomic with regard to interrupts, some
+inconsistencies might happen. For example::
+
+  preempt_disable() {
+	__preempt_count_add(1)
+	------->	smp_apic_timer_interrupt() {
+				preempt_disable()
+					do not trace (preempt count >= 1)
+
+				wake up a thread
+
+				preempt_enable()
+					 do not trace (preempt count >= 1)
+			}
+	<------
+	trace_preempt_disable();
+  }
+
+This problem was reported and discussed here:
+  https://lore.kernel.org/r/cover.1559051152.git.bristot@redhat.com/
+
+Specification
+-------------
+Grapviz Dot file in tools/verification/models/wip.dot
diff --git a/Documentation/trace/rv/monitor_wwnr.rst b/Documentation/trace/rv/monitor_wwnr.rst
new file mode 100644
index 0000000000000..80f1777b85aac
--- /dev/null
+++ b/Documentation/trace/rv/monitor_wwnr.rst
@@ -0,0 +1,45 @@
+Monitor wwnr
+============
+
+- Name: wwrn - wakeup while not running
+- Type: per-task deterministic automaton
+- Author: Daniel Bristot de Oliveira <bristot@kernel.org>
+
+Description
+-----------
+
+This is a per-task sample monitor, with the following
+definition::
+
+               |
+               |
+               v
+    wakeup   +-------------+
+  +--------- |             |
+  |          | not_running |
+  +--------> |             | <+
+             +-------------+  |
+               |              |
+               | switch_in    | switch_out
+               v              |
+             +-------------+  |
+             |   running   | -+
+             +-------------+
+
+This model is borken, the reason is that a task can be running
+in the processor without being set as RUNNABLE. Think about a
+task about to sleep::
+
+  1:      set_current_state(TASK_UNINTERRUPTIBLE);
+  2:      schedule();
+
+And then imagine an IRQ happening in between the lines one and two,
+waking the task up. BOOM, the wakeup will happen while the task is
+running.
+
+- Why do we need this model, so?
+- To test the reactors.
+
+Specification
+-------------
+Grapviz Dot file in tools/verification/models/wwnr.dot
diff --git a/Documentation/trace/rv/runtime-verification.rst b/Documentation/trace/rv/runtime-verification.rst
new file mode 100644
index 0000000000000..c46b6149470ef
--- /dev/null
+++ b/Documentation/trace/rv/runtime-verification.rst
@@ -0,0 +1,231 @@
+====================
+Runtime Verification
+====================
+
+Runtime Verification (RV) is a lightweight (yet rigorous) method that
+complements classical exhaustive verification techniques (such as *model
+checking* and *theorem proving*) with a more practical approach for complex
+systems.
+
+Instead of relying on a fine-grained model of a system (e.g., a
+re-implementation a instruction level), RV works by analyzing the trace of the
+system's actual execution, comparing it against a formal specification of
+the system behavior.
+
+The main advantage is that RV can give precise information on the runtime
+behavior of the monitored system, without the pitfalls of developing models
+that require a re-implementation of the entire system in a modeling language.
+Moreover, given an efficient monitoring method, it is possible execute an
+*online* verification of a system, enabling the *reaction* for unexpected
+events, avoiding, for example, the propagation of a failure on safety-critical
+systems.
+
+Runtime Monitors and Reactors
+=============================
+
+A monitor is the central part of the runtime verification of a system. The
+monitor stands in between the formal specification of the desired (or
+undesired) behavior, and the trace of the actual system.
+
+In Linux terms, the runtime verification monitors are encapsulated inside the
+*RV monitor* abstraction. A *RV monitor* includes a reference model of the
+system, a set of instances of the monitor (per-cpu monitor, per-task monitor,
+and so on), and the helper functions that glue the monitor to the system via
+trace, as depicted bellow::
+
+ Linux   +---- RV Monitor ----------------------------------+ Formal
+  Realm  |                                                  |  Realm
+  +-------------------+     +----------------+     +-----------------+
+  |   Linux kernel    |     |     Monitor    |     |     Reference   |
+  |     Tracing       |  -> |   Instance(s)  | <-  |       Model     |
+  | (instrumentation) |     | (verification) |     | (specification) |
+  +-------------------+     +----------------+     +-----------------+
+         |                          |                       |
+         |                          V                       |
+         |                     +----------+                 |
+         |                     | Reaction |                 |
+         |                     +--+--+--+-+                 |
+         |                        |  |  |                   |
+         |                        |  |  +-> trace output ?  |
+         +------------------------|--|----------------------+
+                                  |  +----> panic ?
+                                  +-------> <user-specified>
+
+In addition to the verification and monitoring of the system, a monitor can
+react to an unexpected event. The forms of reaction can vary from logging the
+event occurrence to the enforcement of the correct behavior to the extreme
+action of taking a system down to avoid the propagation of a failure.
+
+In Linux terms, a *reactor* is an reaction method available for *RV monitors*.
+By default, all monitors should provide a trace output of their actions,
+which is already a reaction. In addition, other reactions will be available
+so the user can enable them as needed.
+
+For further information about the principles of runtime verification and
+RV applied to Linux:
+
+  Bartocci, Ezio, et al. *Introduction to runtime verification.* In: Lectures on
+  Runtime Verification. Springer, Cham, 2018. p. 1-33.
+
+  Falcone, Ylies, et al. *A taxonomy for classifying runtime verification tools.*
+  In: International Conference on Runtime Verification. Springer, Cham, 2018. p.
+  241-262.
+
+  De Oliveira, Daniel Bristot. *Automata-based formal analysis and
+  verification of the real-time Linux kernel.* Ph.D. Thesis, 2020.
+
+Online RV monitors
+==================
+
+Monitors can be classified as *offline* and *online* monitors. *Offline*
+monitor process the traces generated by a system after the events, generally by
+reading the trace execution from a permanent storage system. *Online* monitors
+process the trace during the execution of the system. Online monitors are said
+to be *synchronous* if the processing of an event is attached to the system
+execution, blocking the system during the event monitoring. On the other hand,
+an *asynchronous* monitor has its execution detached from the system. Each type
+of monitor has a set of advantages. For example, *offline* monitors can be
+executed on different machines but require operations to save the log to a
+file. In contrast, *synchronous online* method can react at the exact moment
+a violation occurs.
+
+Another important aspect regarding monitors is the overhead associated with the
+event analysis. If the system generates events at a frequency higher than the
+monitor's ability to process them in the same system, only the *offline*
+methods are viable. On the other hand, if the tracing of the events incurs
+on higher overhead than the simple handling of an event by a monitor, then a
+*synchronous online* monitors will incur on lower overhead.
+
+Indeed, the research presented in:
+
+  De Oliveira, Daniel Bristot; Cucinotta, Tommaso; De Oliveira, Romulo Silva.
+  *Efficient formal verification for the Linux kernel.* In: International
+  Conference on Software Engineering and Formal Methods. Springer, Cham, 2019.
+  p. 315-332.
+
+Shows that for Deterministic Automata models, the synchronous processing of
+events in-kernel causes lower overhead than saving the same events to the trace
+buffer, not even considering collecting the trace for user-space analysis.
+This motivated the development of an in-kernel interface for online monitors.
+
+For further information about modeling of Linux kernel behavior using automata,
+see:
+
+  De Oliveira, Daniel B.; De Oliveira, Romulo S.; Cucinotta, Tommaso. *A thread
+  synchronization model for the PREEMPT_RT Linux kernel.* Journal of Systems
+  Architecture, 2020, 107: 101729.
+
+The user interface
+==================
+
+The user interface resembles the tracing interface (on purpose). It is
+currently at "/sys/kernel/tracing/rv/".
+
+The following files/folders are currently available:
+
+**available_monitors**
+
+- Reading list the available monitors, one per line
+
+For example::
+
+   # cat available_monitors
+   wip
+   wwnr
+
+**available_reactors**
+
+- Reading shows the available reactors, one per line.
+
+For example::
+
+   # cat available_reactors
+   nop
+   panic
+   printk
+
+**enabled_monitors**:
+
+- Reading lists the enabled monitors, one per line
+- Writing to it enables a given monitor
+- Writing a monitor name with a '!' prefix disables it
+- Truncating the file disables all enabled monitors
+
+For example::
+
+   # cat enabled_monitors
+   # echo wip > enabled_monitors
+   # echo wwnr >> enabled_monitors
+   # cat enabled_monitors
+   wip
+   wwnr
+   # echo '!wip' >> enabled_monitors
+   # cat enabled_monitors
+   wwnr
+   # echo > enabled_monitors
+   # cat enabled_monitors
+   #
+
+Note that it is possible to enable more than one monitor concurrently.
+
+**monitoring_on**
+
+This is an on/off general switcher for monitoring. It resembles the
+"tracing_on" switcher in the trace interface.
+
+- Writing "0" stops the monitoring
+- Writing "1" continues the monitoring
+- Reading returns the current status of the monitoring
+
+Note that it does not disable enabled monitors but stop the per-entity
+monitors monitoring the events received from the system.
+
+**reacting_on**
+
+- Writing "0" prevents reactions for happening
+- Writing "1" enable reactions
+- Reading returns the current status of the reaction
+
+**monitors/**
+
+Each monitor will have its own directory inside "monitors/". There the
+monitor-specific files will be presented. The "monitors/" directory resembles
+the "events" directory on tracefs.
+
+For example::
+
+   # cd monitors/wip/
+   # ls
+   desc  enable
+   # cat desc
+   wakeup in preemptive per-cpu testing monitor.
+   # cat enable
+   0
+
+**monitors/MONITOR/desc**
+
+- Reading shows a description of the monitor *MONITOR*
+
+**monitors/MONITOR/enable**
+
+- Writing "0" disables the *MONITOR*
+- Writing "1" enables the *MONITOR*
+- Reading return the current status of the *MONITOR*
+
+**monitors/MONITOR/reactors**
+
+- List available reactors, with the select reaction for the given *MONITOR*
+  inside "[]". The default one is the nop (no operation) reactor.
+- Writing the name of a reactor enables it to the given MONITOR.
+
+For example::
+
+   # cat monitors/wip/reactors
+   [nop]
+   panic
+   printk
+   # echo panic > monitors/wip/reactors
+   # cat monitors/wip/reactors
+   nop
+   [panic]
+   printk
diff --git a/Documentation/trace/uprobetracer.rst b/Documentation/trace/uprobetracer.rst
index a8e5938f609e2..3a1797d707f4c 100644
--- a/Documentation/trace/uprobetracer.rst
+++ b/Documentation/trace/uprobetracer.rst
@@ -26,10 +26,10 @@ Synopsis of uprobe_tracer
 -------------------------
 ::
 
-  p[:[GRP/]EVENT] PATH:OFFSET [FETCHARGS] : Set a uprobe
-  r[:[GRP/]EVENT] PATH:OFFSET [FETCHARGS] : Set a return uprobe (uretprobe)
-  p[:[GRP/]EVENT] PATH:OFFSET%return [FETCHARGS] : Set a return uprobe (uretprobe)
-  -:[GRP/]EVENT                           : Clear uprobe or uretprobe event
+  p[:[GRP/][EVENT]] PATH:OFFSET [FETCHARGS] : Set a uprobe
+  r[:[GRP/][EVENT]] PATH:OFFSET [FETCHARGS] : Set a return uprobe (uretprobe)
+  p[:[GRP/][EVENT]] PATH:OFFSET%return [FETCHARGS] : Set a return uprobe (uretprobe)
+  -:[GRP/][EVENT]                           : Clear uprobe or uretprobe event
 
   GRP           : Group name. If omitted, "uprobes" is the default value.
   EVENT         : Event name. If omitted, the event name is generated based