rv/reactor: Add the printk reactor

A reactor that printks the reaction message.

Link: https://lkml.kernel.org/r/b65f18a7fd6dc6659a3008fd7b7392de3465d47b.1659052063.git.bristot@kernel.org

Cc: Wim Van Sebroeck <[email protected]>
Cc: Guenter Roeck <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Marco Elver <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Cc: "Paul E. McKenney" <[email protected]>
Cc: Shuah Khan <[email protected]>
Cc: Gabriele Paoloni <[email protected]>
Cc: Juri Lelli <[email protected]>
Cc: Clark Williams <[email protected]>
Cc: Tao Zhou <[email protected]>
Cc: Randy Dunlap <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Daniel Bristot de Oliveira <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

Author: Daniel Bristot de Oliveira

kernel/trace/rv/Kconfig

@@ -60,3 +60,11 @@ config RV_REACTORS
 	  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.
+
+config RV_REACT_PRINTK
+	bool "Printk reactor"
+	depends on RV_REACTORS
+	default y
+	help
+	  Enables the printk reactor. The printk reactor emits a printk()
+	  message if an exception is found.

kernel/trace/rv/Makefile

@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 
 obj-$(CONFIG_RV) += rv.o
-obj-$(CONFIG_RV_REACTORS) += rv_reactors.o
 obj-$(CONFIG_RV_MON_WIP) += monitors/wip/wip.o
 obj-$(CONFIG_RV_MON_WWNR) += monitors/wwnr/wwnr.o
+obj-$(CONFIG_RV_REACTORS) += rv_reactors.o
+obj-$(CONFIG_RV_REACT_PRINTK) += reactor_printk.o

kernel/trace/rv/reactor_printk.c

@@ -0,0 +1,42 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2019-2022 Red Hat, Inc. Daniel Bristot de Oliveira <[email protected]>
+ *
+ * Printk RV reactor:
+ *   Prints the exception msg to the kernel message log.
+ */
+#include <linux/ftrace.h>
+#include <linux/tracepoint.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/rv.h>
+
+static void rv_printk_reaction(char *msg)
+{
+	printk_deferred(msg);
+}
+
+static struct rv_reactor rv_printk = {
+	.name = "printk",
+	.description = "prints the exception msg to the kernel message log.",
+	.react = rv_printk_reaction
+};
+
+static int register_react_printk(void)
+{
+	rv_register_reactor(&rv_printk);
+	return 0;
+}
+
+static void unregister_react_printk(void)
+{
+	rv_unregister_reactor(&rv_printk);
+}
+
+module_init(register_react_printk);
+module_exit(unregister_react_printk);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Daniel Bristot de Oliveira");
+MODULE_DESCRIPTION("printk rv reactor: printk if an exception is hit.");