rv: Add runtime reactors interface

A runtime monitor can cause a reaction to the detection of an
exception on the model's execution. By default, the monitors have
tracing reactions, printing the monitor output via tracepoints.
But other reactions can be added (on-demand) via this interface.

The user interface resembles the kernel tracing interface and
presents these files:

"available_reactors"
  - Reading shows the available reactors, one per line.

   For example:
     # cat available_reactors
     nop
     panic
     printk

 "reacting_on"
   - It is an on/off general switch for reactors, disabling
   all reactions.

 "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

Link: https://lkml.kernel.org/r/1794eb994637457bdeaa6bad0b8263d2f7eece0c.1659052063.git.bristot@kernel.org

Cc: Wim Van Sebroeck <wim@linux-watchdog.org>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Marco Elver <elver@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Cc: Gabriele Paoloni <gpaoloni@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Clark Williams <williams@redhat.com>
Cc: Tao Zhou <tao.zhou@linux.dev>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-trace-devel@vger.kernel.org
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/kernel/trace/rv/rv.c b/kernel/trace/rv/rv.c
index 731cc961cc70..45cf64eb2600 100644
--- a/kernel/trace/rv/rv.c
+++ b/kernel/trace/rv/rv.c
@@ -353,6 +353,10 @@ static int create_monitor_dir(struct rv_monitor_def *mdef)
 		goto out_remove_root;
 	}
 
+	retval = reactor_populate_monitor(mdef);
+	if (retval)
+		goto out_remove_root;
+
 	return 0;
 
 out_remove_root:
@@ -669,6 +673,7 @@ static const struct file_operations monitoring_on_fops = {
 
 static void destroy_monitor_dir(struct rv_monitor_def *mdef)
 {
+	reactor_cleanup_monitor(mdef);
 	rv_remove(mdef->root_d);
 }
 
@@ -747,6 +752,7 @@ int rv_unregister_monitor(struct rv_monitor *monitor)
 int __init rv_init_interface(void)
 {
 	struct dentry *tmp;
+	int retval;
 
 	rv_root.root_dir = rv_create_dir("rv", NULL);
 	if (!rv_root.root_dir)
@@ -770,6 +776,9 @@ int __init rv_init_interface(void)
 			     &monitoring_on_fops);
 	if (!tmp)
 		goto out_err;
+	retval = init_rv_reactors(rv_root.root_dir);
+	if (retval)
+		goto out_err;
 
 	turn_monitoring_on();