scftorture: Count single_rpc offline failures in statistics outputgrafted

scf_torture_stats_print() aggregates each invoker thread's counters
into a local scf_statistics structure before printing, but the
n_single_rpc_ofl field is missing from the aggregation loop.  As a
result, the "single_rpc_ofl" value printed in the statistics line is
always zero, even when smp_call_function_single() invocations for the
RPC test have failed due to offline CPUs and been counted by the
invoker threads.

Add the missing accumulation so that the printed value reflects the
actual counts.

Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

15 files changed, 1503 insertions, 0 deletions

diff --git a/tools/verification/rv/.gitignore b/tools/verification/rv/.gitignore
new file mode 100644
index 000000000..34a486585
--- /dev/null
+++ b/tools/verification/rv/.gitignore
@@ -0,0 +1,6 @@
+# SPDX-License-Identifier: GPL-2.0-only
+rv
+rv-static
+fixdep
+feature
+FEATURE-DUMP
diff --git a/tools/verification/rv/Build b/tools/verification/rv/Build
new file mode 100644
index 000000000..a44c22349
--- /dev/null
+++ b/tools/verification/rv/Build
@@ -0,0 +1 @@
+rv-y += src/
diff --git a/tools/verification/rv/Makefile b/tools/verification/rv/Makefile
new file mode 100644
index 000000000..5b898360b
--- /dev/null
+++ b/tools/verification/rv/Makefile
@@ -0,0 +1,81 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+ifeq ($(srctree),)
+  srctree	:= $(patsubst %/,%,$(dir $(CURDIR)))
+  srctree	:= $(patsubst %/,%,$(dir $(srctree)))
+  srctree	:= $(patsubst %/,%,$(dir $(srctree)))
+endif
+
+include $(srctree)/tools/scripts/Makefile.include
+
+# O is an alias for OUTPUT
+OUTPUT          := $(O)
+
+ifeq ($(OUTPUT),)
+  OUTPUT       := $(CURDIR)/
+else
+  # subdir is used by the ../Makefile in $(call descend,)
+  ifneq ($(subdir),)
+    OUTPUT        := $(OUTPUT)/$(subdir)
+  endif
+endif
+
+ifneq ($(patsubst %/,,$(lastword $(OUTPUT))),)
+  OUTPUT := $(OUTPUT)/
+endif
+
+RV		:= $(OUTPUT)rv
+RV_IN		:= $(RV)-in.o
+
+VERSION		:= $(shell sh -c "make -sC ../../.. kernelversion | grep -v make")
+DOCSRC		:= ../../../Documentation/tools/rv/
+
+FEATURE_TESTS	:= libtraceevent
+FEATURE_TESTS	+= libtracefs
+FEATURE_DISPLAY	:= libtraceevent
+FEATURE_DISPLAY	+= libtracefs
+
+all: $(RV)
+
+include $(srctree)/tools/build/Makefile.include
+include Makefile.rv
+
+# check for dependencies only on required targets
+NON_CONFIG_TARGETS := clean install doc doc_clean doc_install
+
+config		:= 1
+ifdef MAKECMDGOALS
+  ifeq ($(filter-out $(NON_CONFIG_TARGETS),$(MAKECMDGOALS)),)
+  config	:= 0
+endif
+endif
+
+ifeq ($(config),1)
+  include $(srctree)/tools/build/Makefile.feature
+  include Makefile.config
+endif
+
+CFLAGS		+= $(INCLUDES) $(LIB_INCLUDES)
+
+export CFLAGS OUTPUT srctree
+
+$(RV): $(RV_IN)
+	$(QUIET_LINK)$(CC) $(LDFLAGS) -o $(RV) $(RV_IN) $(EXTLIBS)
+
+static: $(RV_IN)
+	$(eval LDFLAGS += -static)
+	$(QUIET_LINK)$(CC) $(LDFLAGS) -o $(RV)-static $(RV_IN) $(EXTLIBS)
+
+rv.%: fixdep FORCE
+	make -f $(srctree)/tools/build/Makefile.build dir=. $@
+
+$(RV_IN): fixdep FORCE
+	make $(build)=rv
+
+clean: doc_clean fixdep-clean
+	$(call QUIET_CLEAN, rv)
+	$(Q)find . -name '*.o' -delete -o -name '\.*.cmd' -delete -o -name '\.*.d' -delete
+	$(Q)rm -f rv rv-static fixdep FEATURE-DUMP rv-*
+	$(Q)rm -rf feature
+
+.PHONY: FORCE clean
diff --git a/tools/verification/rv/Makefile.config b/tools/verification/rv/Makefile.config
new file mode 100644
index 000000000..066302230
--- /dev/null
+++ b/tools/verification/rv/Makefile.config
@@ -0,0 +1,48 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+STOP_ERROR :=
+
+LIBTRACEEVENT_MIN_VERSION = 1.5
+LIBTRACEFS_MIN_VERSION = 1.3
+
+define lib_setup
+  $(eval LIB_INCLUDES += $(shell sh -c "$(PKG_CONFIG) --cflags lib$(1)"))
+  $(eval LDFLAGS += $(shell sh -c "$(PKG_CONFIG) --libs-only-L lib$(1)"))
+  $(eval EXTLIBS += $(shell sh -c "$(PKG_CONFIG) --libs-only-l lib$(1)"))
+endef
+
+$(call feature_check,libtraceevent)
+ifeq ($(feature-libtraceevent), 1)
+  $(call detected,CONFIG_LIBTRACEEVENT)
+
+  TEST = $(shell sh -c "$(PKG_CONFIG) --atleast-version $(LIBTRACEEVENT_MIN_VERSION) libtraceevent > /dev/null 2>&1 && echo y || echo n")
+  ifeq ($(TEST),n)
+    $(info libtraceevent version is too low, it must be at least $(LIBTRACEEVENT_MIN_VERSION))
+    STOP_ERROR := 1
+  endif
+
+  $(call lib_setup,traceevent)
+else
+  STOP_ERROR := 1
+  $(info libtraceevent is missing. Please install libtraceevent-dev/libtraceevent-devel)
+endif
+
+$(call feature_check,libtracefs)
+ifeq ($(feature-libtracefs), 1)
+  $(call detected,CONFIG_LIBTRACEFS)
+
+  TEST = $(shell sh -c "$(PKG_CONFIG) --atleast-version $(LIBTRACEFS_MIN_VERSION) libtracefs > /dev/null 2>&1 && echo y || echo n")
+  ifeq ($(TEST),n)
+    $(info libtracefs version is too low, it must be at least $(LIBTRACEFS_MIN_VERSION))
+    STOP_ERROR := 1
+  endif
+
+  $(call lib_setup,tracefs)
+else
+  STOP_ERROR := 1
+  $(info libtracefs is missing. Please install libtracefs-dev/libtracefs-devel)
+endif
+
+ifeq ($(STOP_ERROR),1)
+  $(error Please, check the errors above.)
+endif
diff --git a/tools/verification/rv/Makefile.rv b/tools/verification/rv/Makefile.rv
new file mode 100644
index 000000000..2497fb96c
--- /dev/null
+++ b/tools/verification/rv/Makefile.rv
@@ -0,0 +1,51 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+define allow-override
+  $(if $(or $(findstring environment,$(origin $(1))),\
+            $(findstring command line,$(origin $(1)))),,\
+    $(eval $(1) = $(2)))
+endef
+
+# Allow setting CC and AR, or setting CROSS_COMPILE as a prefix.
+$(call allow-override,CC,$(CROSS_COMPILE)gcc)
+$(call allow-override,AR,$(CROSS_COMPILE)ar)
+$(call allow-override,STRIP,$(CROSS_COMPILE)strip)
+$(call allow-override,PKG_CONFIG,pkg-config)
+$(call allow-override,LD_SO_CONF_PATH,/etc/ld.so.conf.d/)
+$(call allow-override,LDCONFIG,ldconfig)
+export CC AR STRIP PKG_CONFIG LD_SO_CONF_PATH LDCONFIG
+
+FOPTS		:=-flto=auto -ffat-lto-objects -fexceptions -fstack-protector-strong	\
+		-fasynchronous-unwind-tables -fstack-clash-protection
+WOPTS		:=	-O -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2	\
+		-Wp,-D_GLIBCXX_ASSERTIONS -Wno-maybe-uninitialized
+
+ifeq ($(CC),clang)
+  FOPTS		:= $(filter-out -flto=auto -ffat-lto-objects, $(FOPTS))
+  WOPTS		:= $(filter-out -Wno-maybe-uninitialized, $(WOPTS))
+endif
+
+INCLUDE		:= -Iinclude/
+CFLAGS		:= -g -DVERSION=\"$(VERSION)\" $(FOPTS) $(WOPTS) $(EXTRA_CFLAGS) $(INCLUDE)
+LDFLAGS		:= -ggdb $(LDFLAGS) $(EXTRA_LDFLAGS)
+
+INSTALL		:= install
+MKDIR		:= mkdir
+STRIP		:= strip
+BINDIR		:= /usr/bin
+
+.PHONY: install
+install: doc_install
+	$(Q)$(MKDIR) -p $(DESTDIR)$(BINDIR)
+	$(call QUIET_INSTALL,rv)$(INSTALL) $(OUTPUT)rv -m 755 $(DESTDIR)$(BINDIR)
+	$(Q)@$(STRIP) $(DESTDIR)$(BINDIR)/rv
+
+.PHONY: doc doc_clean doc_install
+doc:
+	$(MAKE) -C $(DOCSRC)
+
+doc_clean:
+	$(MAKE) -C $(DOCSRC) clean
+
+doc_install:
+	$(MAKE) -C $(DOCSRC) install
diff --git a/tools/verification/rv/README.txt b/tools/verification/rv/README.txt
new file mode 100644
index 000000000..e96be0dff
--- /dev/null
+++ b/tools/verification/rv/README.txt
@@ -0,0 +1,38 @@
+RV: 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.
+
+The rv tool is the interface for a collection of monitors that aim
+analysing the logical and timing behavior of Linux.
+
+Installing RV
+
+RV depends on the following libraries and tools:
+
+ - libtracefs
+ - libtraceevent
+
+It also depends on python3-docutils to compile man pages.
+
+For development, we suggest the following steps for compiling rtla:
+
+  $ git clone git://git.kernel.org/pub/scm/libs/libtrace/libtraceevent.git
+  $ cd libtraceevent/
+  $ make
+  $ sudo make install
+  $ cd ..
+  $ git clone git://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git
+  $ cd libtracefs/
+  $ make
+  $ sudo make install
+  $ cd ..
+  $ cd $rv_src
+  $ make
+  $ sudo make install
+
+For further information, please see rv manpage and the kernel documentation:
+  Runtime Verification:
+    Documentation/trace/rv/runtime-verification.rst
diff --git a/tools/verification/rv/include/in_kernel.h b/tools/verification/rv/include/in_kernel.h
new file mode 100644
index 000000000..f3bfd3b98
--- /dev/null
+++ b/tools/verification/rv/include/in_kernel.h
@@ -0,0 +1,3 @@
+// SPDX-License-Identifier: GPL-2.0
+int ikm_list_monitors(char *container);
+int ikm_run_monitor(char *monitor, int argc, char **argv);
diff --git a/tools/verification/rv/include/rv.h b/tools/verification/rv/include/rv.h
new file mode 100644
index 000000000..6f668eb26
--- /dev/null
+++ b/tools/verification/rv/include/rv.h
@@ -0,0 +1,13 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#define MAX_DESCRIPTION 1024
+#define MAX_DA_NAME_LEN	32
+
+struct monitor {
+	char name[MAX_DA_NAME_LEN];
+	char desc[MAX_DESCRIPTION];
+	int enabled;
+	int nested;
+};
+
+int should_stop(void);
diff --git a/tools/verification/rv/include/trace.h b/tools/verification/rv/include/trace.h
new file mode 100644
index 000000000..8d89e8c30
--- /dev/null
+++ b/tools/verification/rv/include/trace.h
@@ -0,0 +1,16 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <tracefs.h>
+
+struct trace_instance {
+	struct tracefs_instance		*inst;
+	struct tep_handle		*tep;
+	struct trace_seq		*seq;
+};
+
+int trace_instance_init(struct trace_instance *trace, char *name);
+int trace_instance_start(struct trace_instance *trace);
+void trace_instance_destroy(struct trace_instance *trace);
+
+int collect_registered_events(struct tep_event *event, struct tep_record *record,
+			      int cpu, void *context);
diff --git a/tools/verification/rv/include/utils.h b/tools/verification/rv/include/utils.h
new file mode 100644
index 000000000..f24ae8282
--- /dev/null
+++ b/tools/verification/rv/include/utils.h
@@ -0,0 +1,8 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#define MAX_PATH		1024
+
+void debug_msg(const char *fmt, ...);
+void err_msg(const char *fmt, ...);
+
+extern int config_debug;
diff --git a/tools/verification/rv/src/Build b/tools/verification/rv/src/Build
new file mode 100644
index 000000000..d781983c1
--- /dev/null
+++ b/tools/verification/rv/src/Build
@@ -0,0 +1,4 @@
+rv-y += trace.o
+rv-y += utils.o
+rv-y += in_kernel.o
+rv-y += rv.o
diff --git a/tools/verification/rv/src/in_kernel.c b/tools/verification/rv/src/in_kernel.c
new file mode 100644
index 000000000..e6dea4040
--- /dev/null
+++ b/tools/verification/rv/src/in_kernel.c
@@ -0,0 +1,853 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * in kernel monitor support: allows rv to control in-kernel monitors.
+ *
+ * Copyright (C) 2022 Red Hat Inc, Daniel Bristot de Oliveira <bristot@kernel.org>
+ */
+#include <getopt.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include <unistd.h>
+#include <dirent.h>
+
+#include <trace.h>
+#include <utils.h>
+#include <rv.h>
+
+static int config_has_id;
+static int config_is_container;
+static int config_my_pid;
+static int config_trace;
+
+static char *config_initial_reactor;
+static char *config_reactor;
+
+/*
+ * __ikm_read_enable - reads monitor's enable status
+ *
+ * __does not log errors.
+ *
+ * Returns the current status, or -1 if the monitor does not exist,
+ * __hence not logging errors.
+ */
+static int __ikm_read_enable(char *monitor_name)
+{
+	char path[MAX_PATH];
+	long long enabled;
+	int retval;
+
+	snprintf(path, MAX_PATH, "rv/monitors/%s/enable", monitor_name);
+
+	retval = tracefs_instance_file_read_number(NULL, path, &enabled);
+	if (retval < 0)
+		return -1;
+
+	return enabled;
+}
+
+/*
+ * __ikm_find_monitor - find the full name of a possibly nested module
+ *
+ * __does not log errors.
+ *
+ * Returns 1 if we found the monitor, -1 on error and 0 if it does not exist.
+ * The string out_name is populated with the full name, which can be
+ * equal to monitor_name or container/monitor_name if nested
+ */
+static int __ikm_find_monitor_name(char *monitor_name, char *out_name)
+{
+	char *available_monitors, *cursor, *line;
+	int len = strlen(monitor_name);
+	int found = 0;
+
+	available_monitors = tracefs_instance_file_read(NULL, "rv/available_monitors", NULL);
+	if (!available_monitors)
+		return -1;
+
+	config_is_container = 0;
+	cursor = available_monitors;
+	while ((line = strsep(&cursor, "\n"))) {
+		char *colon = strchr(line, ':');
+
+		if (strcmp(line, monitor_name) && (!colon || strcmp(colon + 1, monitor_name)))
+			continue;
+
+		strncpy(out_name, line, 2 * MAX_DA_NAME_LEN);
+		out_name[2 * MAX_DA_NAME_LEN - 1] = '\0';
+
+		if (colon) {
+			out_name[colon - line] = '/';
+		} else {
+			/* If there are children, they are on the next line. */
+			line = strsep(&cursor, "\n");
+			if (line && !strncmp(line, monitor_name, len) && line[len] == ':')
+				config_is_container = 1;
+		}
+
+		found = 1;
+		break;
+	}
+
+	free(available_monitors);
+	return found;
+}
+
+/*
+ * ikm_read_enable - reads monitor's enable status
+ *
+ * Returns the current status, or -1 on error.
+ */
+static int ikm_read_enable(char *monitor_name)
+{
+	int enabled;
+
+	enabled = __ikm_read_enable(monitor_name);
+	if (enabled < 0) {
+		err_msg("ikm: fail read enabled: %d\n", enabled);
+		return -1;
+	}
+
+	debug_msg("ikm: read enabled: %d\n", enabled);
+
+	return enabled;
+}
+
+/*
+ * ikm_write_enable - write to the monitor's enable file
+ *
+ * Return the number of bytes written, -1 on error.
+ */
+static int ikm_write_enable(char *monitor_name, char *enable_disable)
+{
+	char path[MAX_PATH];
+	int retval;
+
+	debug_msg("ikm: writing enabled: %s\n", enable_disable);
+
+	snprintf(path, MAX_PATH, "rv/monitors/%s/enable", monitor_name);
+	retval = tracefs_instance_file_write(NULL, path, enable_disable);
+	if (retval < strlen(enable_disable)) {
+		err_msg("ikm: writing enabled: %s\n", enable_disable);
+		return -1;
+	}
+
+	return retval;
+}
+
+/*
+ * ikm_enable - enable a monitor
+ *
+ * Returns -1 on failure. Success otherwise.
+ */
+static int ikm_enable(char *monitor_name)
+{
+	return ikm_write_enable(monitor_name, "1");
+}
+
+/*
+ * ikm_disable - disable a monitor
+ *
+ * Returns -1 on failure. Success otherwise.
+ */
+static int ikm_disable(char *monitor_name)
+{
+	return ikm_write_enable(monitor_name, "0");
+}
+
+/*
+ * ikm_read_desc - read monitors' description
+ *
+ * Return a dynamically allocated string with the monitor's
+ * description, NULL otherwise.
+ */
+static char *ikm_read_desc(char *monitor_name)
+{
+	char path[MAX_PATH];
+	char *desc;
+
+	snprintf(path, MAX_PATH, "rv/monitors/%s/desc", monitor_name);
+	desc = tracefs_instance_file_read(NULL, path, NULL);
+	if (!desc) {
+		err_msg("ikm: error reading monitor %s desc\n", monitor_name);
+		return NULL;
+	}
+
+	*strstr(desc, "\n") = '\0';
+
+	return desc;
+}
+
+/*
+ * ikm_fill_monitor_definition - fill monitor's definition
+ *
+ * Returns -1 on error, 1 if the monitor does not belong in the container, 0 otherwise.
+ * container can be NULL
+ */
+static int ikm_fill_monitor_definition(char *name, struct monitor *ikm, char *container)
+{
+	int enabled;
+	char *desc, *nested_name;
+
+	nested_name = strstr(name, ":");
+	if (nested_name) {
+		/* it belongs in container if it starts with "container:" */
+		if (container) {
+			int len = strlen(container);
+
+			if (strncmp(name, container, len) || name[len] != ':')
+				return 1;
+		}
+		*nested_name = '/';
+		++nested_name;
+		ikm->nested = 1;
+	} else {
+		if (container)
+			return 1;
+		nested_name = name;
+		ikm->nested = 0;
+	}
+
+	enabled = ikm_read_enable(name);
+	if (enabled < 0) {
+		err_msg("ikm: monitor %s fail to read enable file, bug?\n", name);
+		return -1;
+	}
+
+	desc = ikm_read_desc(name);
+	if (!desc) {
+		err_msg("ikm: monitor %s does not have desc file, bug?\n", name);
+		return -1;
+	}
+
+	strncpy(ikm->name, nested_name, sizeof(ikm->name) - 1);
+	ikm->name[sizeof(ikm->name) - 1] = '\0';
+	ikm->enabled = enabled;
+	strncpy(ikm->desc, desc, sizeof(ikm->desc) - 1);
+	ikm->desc[sizeof(ikm->desc) - 1] = '\0';
+	free(desc);
+
+	return 0;
+}
+
+/*
+ * ikm_write_reactor - switch the reactor to *reactor
+ *
+ * Return the number or characters written, -1 on error.
+ */
+static int ikm_write_reactor(char *monitor_name, char *reactor)
+{
+	char path[MAX_PATH];
+	int retval;
+
+	snprintf(path, MAX_PATH, "rv/monitors/%s/reactors", monitor_name);
+	retval = tracefs_instance_file_write(NULL, path, reactor);
+	debug_msg("ikm: write \"%s\" reactors: %d\n", reactor, retval);
+
+	return retval;
+}
+
+/*
+ * ikm_read_reactor - read the reactors file
+ *
+ * Returns a dynamically allocated string with monitor's
+ * available reactors, or NULL on error.
+ */
+static char *ikm_read_reactor(char *monitor_name)
+{
+	char path[MAX_PATH];
+	char *reactors;
+
+	snprintf(path, MAX_PATH, "rv/monitors/%s/reactors", monitor_name);
+	reactors = tracefs_instance_file_read(NULL, path, NULL);
+	if (!reactors) {
+		err_msg("ikm: fail reading monitor's %s reactors file\n", monitor_name);
+		return NULL;
+	}
+
+	return reactors;
+}
+
+/*
+ * ikm_get_current_reactor - get the current enabled reactor
+ *
+ * Reads the reactors file and find the currently enabled
+ * [reactor].
+ *
+ * Returns a dynamically allocated memory with the current
+ * reactor. NULL otherwise.
+ */
+static char *ikm_get_current_reactor(char *monitor_name)
+{
+	char *reactors = ikm_read_reactor(monitor_name);
+	char *curr_reactor = NULL;
+	char *start;
+	char *end;
+
+	if (!reactors)
+		return NULL;
+
+	start = strstr(reactors, "[");
+	if (!start)
+		goto out_free;
+
+	start++;
+
+	end = strstr(start, "]");
+	if (!end)
+		goto out_free;
+
+	*end = '\0';
+
+	curr_reactor = calloc(strlen(start) + 1, sizeof(char));
+	if (!curr_reactor)
+		goto out_free;
+
+	strncpy(curr_reactor, start, strlen(start));
+	debug_msg("ikm: read current reactor %s\n", curr_reactor);
+
+out_free:
+	free(reactors);
+
+	return curr_reactor;
+}
+
+static int ikm_has_id(char *monitor_name)
+{
+	char path[MAX_PATH];
+	char *format;
+	int has_id;
+
+	snprintf(path, MAX_PATH, "events/rv/event_%s/format", monitor_name);
+	format = tracefs_instance_file_read(NULL, path, NULL);
+	if (!format) {
+		err_msg("ikm: fail reading monitor's %s format event file\n", monitor_name);
+		return -1;
+	}
+
+	/* print fmt: "%d: %s x %s -> %s %s", REC->id, ... */
+	has_id = !!strstr(format, "REC->id");
+
+	debug_msg("ikm: monitor %s has id: %s\n", monitor_name, has_id ? "yes" : "no");
+
+	free(format);
+
+	return has_id;
+}
+
+/**
+ * ikm_list_monitors - list all available monitors
+ *
+ * Returns 0 on success, -1 otherwise.
+ */
+int ikm_list_monitors(char *container)
+{
+	char *available_monitors;
+	struct monitor ikm = {0};
+	char *curr, *next;
+	int retval, list_monitor = 0;
+
+	available_monitors = tracefs_instance_file_read(NULL, "rv/available_monitors", NULL);
+
+	if (!available_monitors) {
+		err_msg("ikm: available monitors is not available, is CONFIG_RV enabled?\n");
+		return -1;
+	}
+
+	curr = available_monitors;
+	do {
+		next = strstr(curr, "\n");
+		*next = '\0';
+
+		retval = ikm_fill_monitor_definition(curr, &ikm, container);
+		if (retval < 0)
+			err_msg("ikm: error reading %d in kernel monitor, skipping\n", curr);
+
+		if (!retval) {
+			int indent = ikm.nested && !container;
+
+			list_monitor = 1;
+			printf("%s%-*s %s %s\n", indent ? " - " : "",
+			       indent ? MAX_DA_NAME_LEN - 3 : MAX_DA_NAME_LEN,
+			       ikm.name, ikm.desc, ikm.enabled ? "[ON]" : "[OFF]");
+		}
+		curr = ++next;
+
+	} while (strlen(curr));
+
+	if (!list_monitor) {
+		if (container)
+			printf("-- No monitor found in container %s --\n", container);
+		else
+			printf("-- No monitor found --\n");
+	}
+
+	free(available_monitors);
+
+	return 0;
+}
+
+static void ikm_print_header(struct trace_seq *s)
+{
+	trace_seq_printf(s, "%16s-%-8s %5s %5s ", "<TASK>", "PID", "[CPU]", "TYPE");
+	if (config_has_id)
+		trace_seq_printf(s, "%8s ", "ID");
+
+	trace_seq_printf(s, "%24s x %-24s -> %-24s %s\n",
+			 "STATE",
+			 "EVENT",
+			 "NEXT_STATE",
+			 "FINAL");
+
+	trace_seq_printf(s, "%16s %-8s %5s %5s ", " | ", " | ", " | ", " | ");
+
+	if (config_has_id)
+		trace_seq_printf(s, "%8s ", " | ");
+
+	trace_seq_printf(s, "%24s   %-24s    %-24s %s\n",
+			 " | ",
+			 " | ",
+			 " | ",
+			 "|");
+
+}
+
+/*
+ * ikm_event_handler - callback to handle event events
+ *
+ * Called any time a rv:"monitor"_event events is generated.
+ * It parses and prints event.
+ */
+static int
+ikm_event_handler(struct trace_seq *s, struct tep_record *record,
+		  struct tep_event *trace_event, void *context)
+{
+	/* if needed: struct trace_instance *inst = context; */
+	char *state, *event, *next_state;
+	unsigned long long final_state;
+	unsigned long long pid;
+	unsigned long long id;
+	int val;
+	bool missing_id;
+
+	if (config_has_id)
+		missing_id = tep_get_field_val(s, trace_event, "id", record, &id, 1);
+
+	tep_get_common_field_val(s, trace_event, "common_pid", record, &pid, 1);
+
+	if (config_has_id && (config_my_pid == id))
+		return 0;
+	else if (config_my_pid == pid)
+		return 0;
+
+	tep_print_event(trace_event->tep, s, record, "%16s-%-8d [%.3d] ",
+			TEP_PRINT_COMM, TEP_PRINT_PID, TEP_PRINT_CPU);
+
+	if (config_is_container)
+		tep_print_event(trace_event->tep, s, record, "%s ", TEP_PRINT_NAME);
+	else
+		trace_seq_printf(s, "event ");
+
+	if (config_has_id) {
+		if (missing_id)
+			/* placeholder if we are dealing with a mixed-type container*/
+			trace_seq_printf(s, "        ");
+		else
+			trace_seq_printf(s, "%8llu ", id);
+	}
+
+	state = tep_get_field_raw(s, trace_event, "state", record, &val, 0);
+	event = tep_get_field_raw(s, trace_event, "event", record, &val, 0);
+	next_state = tep_get_field_raw(s, trace_event, "next_state", record, &val, 0);
+	tep_get_field_val(s, trace_event, "final_state", record, &final_state, 1);
+
+	trace_seq_printf(s, "%24s x %-24s -> %-24s %s\n",
+			 state,
+			 event,
+			 next_state,
+			 final_state ? "Y" : "N");
+
+	trace_seq_do_printf(s);
+	trace_seq_reset(s);
+
+	return 0;
+}
+
+/*
+ * ikm_error_handler - callback to handle error events
+ *
+ * Called any time a rv:"monitor"_errors events is generated.
+ * It parses and prints event.
+ */
+static int
+ikm_error_handler(struct trace_seq *s, struct tep_record *record,
+		  struct tep_event *trace_event, void *context)
+{
+	unsigned long long pid, id;
+	int cpu = record->cpu;
+	char *state, *event;
+	int val;
+	bool missing_id;
+
+	if (config_has_id)
+		missing_id = tep_get_field_val(s, trace_event, "id", record, &id, 1);
+
+	tep_get_common_field_val(s, trace_event, "common_pid", record, &pid, 1);
+
+	if (config_has_id && config_my_pid == id)
+		return 0;
+	else if (config_my_pid == pid)
+		return 0;
+
+	trace_seq_printf(s, "%8lld [%03d] ", pid, cpu);
+
+	if (config_is_container)
+		tep_print_event(trace_event->tep, s, record, "%s ", TEP_PRINT_NAME);
+	else
+		trace_seq_printf(s, "error ");
+
+	if (config_has_id) {
+		if (missing_id)
+			/* placeholder if we are dealing with a mixed-type container*/
+			trace_seq_printf(s, "        ");
+		else
+			trace_seq_printf(s, "%8llu ", id);
+	}
+
+	state = tep_get_field_raw(s, trace_event, "state", record, &val, 0);
+	event = tep_get_field_raw(s, trace_event, "event", record, &val, 0);
+
+	trace_seq_printf(s, "%24s x %s\n", state, event);
+
+	trace_seq_do_printf(s);
+	trace_seq_reset(s);
+
+	return 0;
+}
+
+static int ikm_enable_trace_events(char *monitor_name, struct trace_instance *inst)
+{
+	char event[MAX_DA_NAME_LEN + 7]; /* max(error_,event_) + '0' = 7 */
+	int retval;
+
+	snprintf(event, sizeof(event), "event_%s", monitor_name);
+	retval = tracefs_event_enable(inst->inst, "rv",  event);
+	if (retval)
+		return -1;
+
+	tep_register_event_handler(inst->tep, -1, "rv", event,
+				   ikm_event_handler, NULL);
+
+	snprintf(event, sizeof(event), "error_%s", monitor_name);
+	retval = tracefs_event_enable(inst->inst, "rv", event);
+	if (retval)
+		return -1;
+
+	tep_register_event_handler(inst->tep, -1, "rv", event,
+				   ikm_error_handler, NULL);
+
+	/* set if at least 1 monitor has id in case of a container */
+	config_has_id = ikm_has_id(monitor_name);
+	if (config_has_id < 0)
+		return -1;
+
+
+	return 0;
+}
+
+static int ikm_enable_trace_container(char *monitor_name,
+				      struct trace_instance *inst)
+{
+	DIR *dp;
+	char *abs_path, rv_path[MAX_PATH];
+	struct dirent *ep;
+	int retval = 0;
+
+	snprintf(rv_path, MAX_PATH, "rv/monitors/%s", monitor_name);
+	abs_path = tracefs_instance_get_file(NULL, rv_path);
+	if (!abs_path)
+		return -1;
+	dp = opendir(abs_path);
+	if (!dp)
+		goto out_free;
+
+	while (!retval && (ep = readdir(dp))) {
+		if (ep->d_type != DT_DIR || ep->d_name[0] == '.')
+			continue;
+		retval = ikm_enable_trace_events(ep->d_name, inst);
+	}
+
+	closedir(dp);
+out_free:
+	free(abs_path);
+	return retval;
+}
+
+/*
+ * ikm_setup_trace_instance - set up a tracing instance to collect data
+ *
+ * Create a trace instance, enable rv: events and enable the trace.
+ *
+ * Returns the trace_instance * with all set, NULL otherwise.
+ */
+static struct trace_instance *ikm_setup_trace_instance(char *monitor_name)
+{
+	struct trace_instance *inst;
+	int retval;
+
+	if (!config_trace)
+		return NULL;
+
+	/* alloc data */
+	inst = calloc(1, sizeof(*inst));
+	if (!inst) {
+		err_msg("ikm: failed to allocate trace instance");
+		goto out_err;
+	}
+
+	retval = trace_instance_init(inst, monitor_name);
+	if (retval)
+		goto out_free;
+
+	if (config_is_container)
+		retval = ikm_enable_trace_container(monitor_name, inst);
+	else
+		retval = ikm_enable_trace_events(monitor_name, inst);
+	if (retval)
+		goto out_inst;
+
+	/* ready to enable */
+	tracefs_trace_on(inst->inst);
+
+	return inst;
+
+out_inst:
+	trace_instance_destroy(inst);
+out_free:
+	free(inst);
+out_err:
+	return NULL;
+}
+
+/**
+ * ikm_destroy_trace_instance - destroy a previously created instance
+ */
+static void ikm_destroy_trace_instance(struct trace_instance *inst)
+{
+	if (!inst)
+		return;
+
+	trace_instance_destroy(inst);
+	free(inst);
+}
+
+/*
+ * ikm_usage_print_reactors - print all available reactors, one per line.
+ */
+static void ikm_usage_print_reactors(void)
+{
+	char *reactors = tracefs_instance_file_read(NULL, "rv/available_reactors", NULL);
+	char *start, *end;
+
+	if (!reactors)
+		return;
+
+	fprintf(stderr, "  available reactors:");
+
+	start = reactors;
+	end = strstr(start, "\n");
+
+	while (end) {
+		*end = '\0';
+
+		fprintf(stderr, " %s", start);
+
+		start = ++end;
+		end = strstr(start, "\n");
+	}
+
+	fprintf(stderr, "\n");
+}
+/*
+ * ikm_usage - print usage
+ */
+static void ikm_usage(int exit_val, char *monitor_name, const char *fmt, ...)
+{
+
+	char message[1024];
+	va_list ap;
+	int i;
+
+	static const char *const usage[] = {
+		"",
+		"	-h/--help: print this menu and the reactor list",
+		"	-r/--reactor 'reactor': enables the 'reactor'",
+		"	-s/--self: when tracing (-t), also trace rv command",
+		"	-t/--trace: trace monitor's event",
+		"	-v/--verbose: print debug messages",
+		"",
+		NULL,
+	};
+
+	va_start(ap, fmt);
+	vsnprintf(message, sizeof(message), fmt, ap);
+	va_end(ap);
+
+	fprintf(stderr, "  %s\n", message);
+
+	fprintf(stderr, "\n  usage: rv mon %s [-h] [-q] [-r reactor] [-s] [-v]", monitor_name);
+
+	for (i = 0; usage[i]; i++)
+		fprintf(stderr, "%s\n", usage[i]);
+
+	ikm_usage_print_reactors();
+	exit(exit_val);
+}
+
+/*
+ * parse_arguments - parse arguments and set config
+ */
+static int parse_arguments(char *monitor_name, int argc, char **argv)
+{
+	int c, retval;
+
+	config_my_pid = getpid();
+
+	while (1) {
+		static struct option long_options[] = {
+			{"help",		no_argument,		0, 'h'},
+			{"reactor",		required_argument,	0, 'r'},
+			{"self",		no_argument,		0, 's'},
+			{"trace",		no_argument,		0, 't'},
+			{"verbose",		no_argument,		0, 'v'},
+			{0, 0, 0, 0}
+		};
+
+		/* getopt_long stores the option index here. */
+		int option_index = 0;
+
+		c = getopt_long(argc, argv, "hr:stv", long_options, &option_index);
+
+		/* detect the end of the options. */
+		if (c == -1)
+			break;
+
+		switch (c) {
+		case 'h':
+			ikm_usage(0, monitor_name, "help:");
+			break;
+		case 'r':
+			config_reactor = optarg;
+			break;
+		case 's':
+			config_my_pid = -1;
+			break;
+		case 't':
+			config_trace = 1;
+			break;
+		case 'v':
+			config_debug = 1;
+			break;
+		}
+	}
+
+	if (config_reactor) {
+		config_initial_reactor = ikm_get_current_reactor(monitor_name);
+		if (!config_initial_reactor)
+			ikm_usage(1, monitor_name,
+				  "ikm: failed to read current reactor, are reactors enabled?");
+
+		retval = ikm_write_reactor(monitor_name, config_reactor);
+		if (retval <= 0)
+			ikm_usage(1, monitor_name,
+				  "ikm: failed to set %s reactor, is it available?",
+				  config_reactor);
+	}
+
+	debug_msg("ikm: my pid is %d\n", config_my_pid);
+
+	return 0;
+}
+
+/**
+ * ikm_run_monitor - apply configs and run the monitor
+ *
+ * Returns 1 if a monitor was found an executed, 0 if no
+ * monitors were found, or -1 on error.
+ */
+int ikm_run_monitor(char *monitor_name, int argc, char **argv)
+{
+	struct trace_instance *inst = NULL;
+	char *nested_name, full_name[2*MAX_DA_NAME_LEN];
+	int retval;
+
+	nested_name = strstr(monitor_name, ":");
+	if (nested_name)
+		++nested_name;
+	else
+		nested_name = monitor_name;
+
+	retval = __ikm_find_monitor_name(monitor_name, full_name);
+	if (!retval)
+		return 0;
+	if (retval < 0) {
+		err_msg("ikm: error finding monitor %s\n", nested_name);
+		return -1;
+	}
+
+	retval = __ikm_read_enable(full_name);
+	if (retval) {
+		err_msg("ikm: monitor %s (in-kernel) is already enabled\n", nested_name);
+		return -1;
+	}
+
+	/* we should be good to go */
+	retval = parse_arguments(full_name, argc, argv);
+	if (retval)
+		ikm_usage(1, nested_name, "ikm: failed parsing arguments");
+
+	if (config_trace) {
+		inst = ikm_setup_trace_instance(nested_name);
+		if (!inst)
+			goto out_free_instance;
+	}
+
+	retval = ikm_enable(full_name);
+	if (retval < 0)
+		goto out_free_instance;
+
+	if (config_trace)
+		ikm_print_header(inst->seq);
+
+	while (!should_stop()) {
+		if (config_trace) {
+			retval = tracefs_iterate_raw_events(inst->tep,
+							    inst->inst,
+							    NULL,
+							    0,
+							    collect_registered_events,
+							    inst);
+			if (retval) {
+				err_msg("ikm: error reading trace buffer\n");
+				break;
+			}
+		}
+
+		sleep(1);
+	}
+
+	ikm_disable(full_name);
+	ikm_destroy_trace_instance(inst);
+
+	if (config_reactor && config_initial_reactor)
+		ikm_write_reactor(full_name, config_initial_reactor);
+
+	return 1;
+
+out_free_instance:
+	ikm_destroy_trace_instance(inst);
+	if (config_reactor && config_initial_reactor)
+		ikm_write_reactor(full_name, config_initial_reactor);
+	return -1;
+}
diff --git a/tools/verification/rv/src/rv.c b/tools/verification/rv/src/rv.c
new file mode 100644
index 000000000..b8fe24a87
--- /dev/null
+++ b/tools/verification/rv/src/rv.c
@@ -0,0 +1,201 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * rv tool, the interface for the Linux kernel RV subsystem and home of
+ * user-space controlled monitors.
+ *
+ * Copyright (C) 2022 Red Hat Inc, Daniel Bristot de Oliveira <bristot@kernel.org>
+ */
+
+#include <stdlib.h>
+#include <signal.h>
+#include <unistd.h>
+
+#include <trace.h>
+#include <utils.h>
+#include <in_kernel.h>
+
+static int stop_session;
+
+/*
+ * stop_rv - tell monitors to stop
+ */
+static void stop_rv(int sig)
+{
+	stop_session = 1;
+}
+
+/**
+ * should_stop - check if the monitor should stop.
+ *
+ * Returns 1 if the monitor should stop, 0 otherwise.
+ */
+int should_stop(void)
+{
+	return stop_session;
+}
+
+/*
+ * rv_list - list all available monitors
+ */
+static void rv_list(int argc, char **argv)
+{
+	static const char *const usage[] = {
+		"",
+		"  usage: rv list [-h] [container]",
+		"",
+		"	list all available monitors",
+		"",
+		"	-h/--help: print this menu",
+		"",
+		"	[container]: list only monitors in this container",
+		NULL,
+	};
+	int i, print_help = 0, retval = 0;
+	char *container = NULL;
+
+	if (argc == 2) {
+		if (!strcmp(argv[1], "-h") || !strcmp(argv[1], "--help")) {
+			print_help = 1;
+			retval = 0;
+		} else if (argv[1][0] == '-') {
+			/* assume invalid option */
+			print_help = 1;
+			retval = 1;
+		} else
+			container = argv[1];
+	} else if (argc > 2) {
+		/* more than 2 is always usage */
+		print_help = 1;
+		retval = 1;
+	}
+	if (print_help) {
+		fprintf(stderr, "rv version %s\n", VERSION);
+		for (i = 0; usage[i]; i++)
+			fprintf(stderr, "%s\n", usage[i]);
+		exit(retval);
+	}
+
+	ikm_list_monitors(container);
+
+	exit(0);
+}
+
+/*
+ * rv_mon - try to run a monitor passed as argument
+ */
+static void rv_mon(int argc, char **argv)
+{
+	char *monitor_name;
+	int i, run = 0;
+
+	static const char *const usage[] = {
+		"",
+		"  usage: rv mon [-h] monitor [monitor options]",
+		"",
+		"	run a monitor",
+		"",
+		"	-h/--help: print this menu",
+		"",
+		"	monitor [monitor options]: the monitor, passing",
+		"	the arguments to the [monitor options]",
+		NULL,
+	};
+
+	/* requires at least one argument */
+	if (argc == 1) {
+
+		fprintf(stderr, "rv version %s\n", VERSION);
+
+		for (i = 0; usage[i]; i++)
+			fprintf(stderr, "%s\n", usage[i]);
+		exit(1);
+	} else if (!strcmp(argv[1], "-h") || !strcmp(argv[1], "--help")) {
+
+		fprintf(stderr, "rv version %s\n", VERSION);
+
+		for (i = 0; usage[i]; i++)
+			fprintf(stderr, "%s\n", usage[i]);
+		exit(0);
+	}
+
+	monitor_name = argv[1];
+	/*
+	 * Call all possible monitor implementations, looking
+	 * for the [monitor].
+	 */
+	run += ikm_run_monitor(monitor_name, argc-1, &argv[1]);
+
+	if (!run)
+		err_msg("rv: monitor %s does not exist\n", monitor_name);
+	exit(!run);
+}
+
+static void usage(int exit_val, const char *fmt, ...)
+{
+	char message[1024];
+	va_list ap;
+	int i;
+
+	static const char *const usage[] = {
+		"",
+		"  usage: rv command [-h] [command_options]",
+		"",
+		"	-h/--help: print this menu",
+		"",
+		"	command: run one of the following command:",
+		"	  list: list all available monitors",
+		"	  mon:  run a monitor",
+		"",
+		"	[command options]: each command has its own set of options",
+		"		           run rv command -h for further information",
+		NULL,
+	};
+
+	va_start(ap, fmt);
+	vsnprintf(message, sizeof(message), fmt, ap);
+	va_end(ap);
+
+	fprintf(stderr, "rv version %s: %s\n", VERSION, message);
+
+	for (i = 0; usage[i]; i++)
+		fprintf(stderr, "%s\n", usage[i]);
+
+	exit(exit_val);
+}
+
+/*
+ * main - select which main sending the command
+ *
+ * main itself redirects the arguments to the sub-commands
+ * to handle the options.
+ *
+ * subcommands should exit.
+ */
+int main(int argc, char **argv)
+{
+	if (geteuid())
+		usage(1, "%s needs root permission", argv[0]);
+
+	if (argc <= 1)
+		usage(1, "%s requires a command", argv[0]);
+
+	if (!strcmp(argv[1], "-h") || !strcmp(argv[1], "--help"))
+		usage(0, "help");
+
+	if (!strcmp(argv[1], "list"))
+		rv_list(--argc, &argv[1]);
+
+	if (!strcmp(argv[1], "mon")) {
+		/*
+		 * monitor's main should monitor should_stop() function.
+		 * and exit.
+		 */
+		signal(SIGINT, stop_rv);
+		signal(SIGTERM, stop_rv);
+
+		rv_mon(argc - 1, &argv[1]);
+	}
+
+	/* invalid sub-command */
+	usage(1, "%s does not know the %s command, old version?", argv[0], argv[1]);
+}
diff --git a/tools/verification/rv/src/trace.c b/tools/verification/rv/src/trace.c
new file mode 100644
index 000000000..1b9f9bfa1
--- /dev/null
+++ b/tools/verification/rv/src/trace.c
@@ -0,0 +1,133 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * trace helpers.
+ *
+ * Copyright (C) 2022 Red Hat Inc, Daniel Bristot de Oliveira <bristot@kernel.org>
+ */
+
+#include <sys/sendfile.h>
+#include <tracefs.h>
+#include <signal.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+
+#include <rv.h>
+#include <trace.h>
+#include <utils.h>
+
+/*
+ * create_instance - create a trace instance with *instance_name
+ */
+static struct tracefs_instance *create_instance(char *instance_name)
+{
+	return tracefs_instance_create(instance_name);
+}
+
+/*
+ * destroy_instance - remove a trace instance and free the data
+ */
+static void destroy_instance(struct tracefs_instance *inst)
+{
+	tracefs_instance_destroy(inst);
+	tracefs_instance_free(inst);
+}
+
+/**
+ * collect_registered_events - call the existing callback function for the event
+ *
+ * If an event has a registered callback function, call it.
+ * Otherwise, ignore the event.
+ *
+ * Returns 0 if the event was collected, 1 if the tool should stop collecting trace.
+ */
+int
+collect_registered_events(struct tep_event *event, struct tep_record *record,
+			  int cpu, void *context)
+{
+	struct trace_instance *trace = context;
+	struct trace_seq *s = trace->seq;
+
+	if (should_stop())
+		return 1;
+
+	if (!event->handler)
+		return 0;
+
+	event->handler(s, record, event, context);
+
+	return 0;
+}
+
+/**
+ * trace_instance_destroy - destroy and free a rv trace instance
+ */
+void trace_instance_destroy(struct trace_instance *trace)
+{
+	if (trace->inst) {
+		destroy_instance(trace->inst);
+		trace->inst = NULL;
+	}
+
+	if (trace->seq) {
+		free(trace->seq);
+		trace->seq = NULL;
+	}
+
+	if (trace->tep) {
+		tep_free(trace->tep);
+		trace->tep = NULL;
+	}
+}
+
+/**
+ * trace_instance_init - create a trace instance
+ *
+ * It is more than the tracefs instance, as it contains other
+ * things required for the tracing, such as the local events and
+ * a seq file.
+ *
+ * Note that the trace instance is returned disabled. This allows
+ * the tool to apply some other configs, like setting priority
+ * to the kernel threads, before starting generating trace entries.
+ *
+ * Returns 0 on success, non-zero otherwise.
+ */
+int trace_instance_init(struct trace_instance *trace, char *name)
+{
+	trace->seq = calloc(1, sizeof(*trace->seq));
+	if (!trace->seq)
+		goto out_err;
+
+	trace_seq_init(trace->seq);
+
+	trace->inst = create_instance(name);
+	if (!trace->inst)
+		goto out_err;
+
+	trace->tep = tracefs_local_events(NULL);
+	if (!trace->tep)
+		goto out_err;
+
+	/*
+	 * Let the main enable the record after setting some other
+	 * things such as the priority of the tracer's threads.
+	 */
+	tracefs_trace_off(trace->inst);
+
+	return 0;
+
+out_err:
+	trace_instance_destroy(trace);
+	return 1;
+}
+
+/**
+ * trace_instance_start - start tracing a given rv instance
+ *
+ * Returns 0 on success, -1 otherwise.
+ */
+int trace_instance_start(struct trace_instance *trace)
+{
+	return tracefs_trace_on(trace->inst);
+}
diff --git a/tools/verification/rv/src/utils.c b/tools/verification/rv/src/utils.c
new file mode 100644
index 000000000..5677b439d
--- /dev/null
+++ b/tools/verification/rv/src/utils.c
@@ -0,0 +1,47 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * util functions.
+ *
+ * Copyright (C) 2022 Red Hat Inc, Daniel Bristot de Oliveira <bristot@kernel.org>
+ */
+
+#include <stdarg.h>
+#include <stdio.h>
+#include <utils.h>
+
+int config_debug;
+
+#define MAX_MSG_LENGTH	1024
+
+/**
+ * err_msg - print an error message to the stderr
+ */
+void err_msg(const char *fmt, ...)
+{
+	char message[MAX_MSG_LENGTH];
+	va_list ap;
+
+	va_start(ap, fmt);
+	vsnprintf(message, sizeof(message), fmt, ap);
+	va_end(ap);
+
+	fprintf(stderr, "%s", message);
+}
+
+/**
+ * debug_msg - print a debug message to stderr if debug is set
+ */
+void debug_msg(const char *fmt, ...)
+{
+	char message[MAX_MSG_LENGTH];
+	va_list ap;
+
+	if (!config_debug)
+		return;
+
+	va_start(ap, fmt);
+	vsnprintf(message, sizeof(message), fmt, ap);
+	va_end(ap);
+
+	fprintf(stderr, "%s", message);
+}