ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

4 files changed, 116 insertions, 0 deletions

diff --git a/tools/testing/selftests/dt/.gitignore b/tools/testing/selftests/dt/.gitignore
new file mode 100644
index 000000000..f6476c9f2
--- /dev/null
+++ b/tools/testing/selftests/dt/.gitignore
@@ -0,0 +1 @@
+compatible_list
diff --git a/tools/testing/selftests/dt/Makefile b/tools/testing/selftests/dt/Makefile
new file mode 100644
index 000000000..2d33ee9e9
--- /dev/null
+++ b/tools/testing/selftests/dt/Makefile
@@ -0,0 +1,21 @@
+PY3 = $(shell which python3 2>/dev/null)
+
+ifneq ($(PY3),)
+
+TEST_PROGS := test_unprobed_devices.sh
+TEST_GEN_FILES := compatible_list
+TEST_FILES := compatible_ignore_list
+
+include ../lib.mk
+
+$(OUTPUT)/compatible_list:
+	$(top_srcdir)/scripts/dtc/dt-extract-compatibles -d $(top_srcdir) > $@
+
+else
+
+all: no_py3_warning
+
+no_py3_warning:
+	@echo "Missing python3. This test will be skipped."
+
+endif
diff --git a/tools/testing/selftests/dt/compatible_ignore_list b/tools/testing/selftests/dt/compatible_ignore_list
new file mode 100644
index 000000000..1323903fe
--- /dev/null
+++ b/tools/testing/selftests/dt/compatible_ignore_list
@@ -0,0 +1 @@
+simple-mfd
diff --git a/tools/testing/selftests/dt/test_unprobed_devices.sh b/tools/testing/selftests/dt/test_unprobed_devices.sh
new file mode 100755
index 000000000..5e3f42ef2
--- /dev/null
+++ b/tools/testing/selftests/dt/test_unprobed_devices.sh
@@ -0,0 +1,93 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+#
+# Copyright (c) 2023 Collabora Ltd
+#
+# Based on Frank Rowand's dt_stat script.
+#
+# This script tests for devices that were declared on the Devicetree and are
+# expected to bind to a driver, but didn't.
+#
+# To achieve this, two lists are used:
+# * a list of the compatibles that can be matched by a Devicetree node
+# * a list of compatibles that should be ignored
+#
+
+DIR="$(dirname $(readlink -f "$0"))"
+
+source "${DIR}"/../kselftest/ktap_helpers.sh
+
+PDT=/proc/device-tree/
+COMPAT_LIST="${DIR}"/compatible_list
+IGNORE_LIST="${DIR}"/compatible_ignore_list
+
+ktap_print_header
+
+if [[ ! -d "${PDT}" ]]; then
+	ktap_skip_all "${PDT} doesn't exist."
+	exit "${KSFT_SKIP}"
+fi
+
+nodes_compatible=$(
+	for node in $(find ${PDT} -type d); do
+		[ ! -f "${node}"/compatible ] && continue
+		# Check if node is available
+		if [[ -e "${node}"/status ]]; then
+			status=$(tr -d '\000' < "${node}"/status)
+			if [[ "${status}" != "okay" && "${status}" != "ok" ]]; then
+				if [ -n "${disabled_nodes_regex}" ]; then
+					disabled_nodes_regex="${disabled_nodes_regex}|${node}"
+				else
+					disabled_nodes_regex="${node}"
+				fi
+				continue
+			fi
+		fi
+
+		# Ignore this node if one of its ancestors was disabled
+		if [ -n "${disabled_nodes_regex}" ]; then
+			echo "${node}" | grep -q -E "${disabled_nodes_regex}" && continue
+		fi
+
+		echo "${node}" | sed -e 's|\/proc\/device-tree||'
+	done | sort
+	)
+
+nodes_dev_bound=$(
+	IFS=$'\n'
+	for dev_dir in $(find /sys/devices -type d); do
+		[ ! -f "${dev_dir}"/uevent ] && continue
+		[ ! -d "${dev_dir}"/driver ] && continue
+
+		grep '^OF_FULLNAME=' "${dev_dir}"/uevent | sed -e 's|OF_FULLNAME=||'
+	done
+	)
+
+num_tests=$(echo ${nodes_compatible} | wc -w)
+ktap_set_plan "${num_tests}"
+
+retval="${KSFT_PASS}"
+for node in ${nodes_compatible}; do
+	if ! echo "${nodes_dev_bound}" | grep -E -q "(^| )${node}( |\$)"; then
+		compatibles=$(tr '\000' '\n' < "${PDT}"/"${node}"/compatible)
+
+		for compatible in ${compatibles}; do
+			if grep -x -q "${compatible}" "${IGNORE_LIST}"; then
+				continue
+			fi
+
+			if grep -x -q "${compatible}" "${COMPAT_LIST}"; then
+				ktap_test_fail "${node}"
+				retval="${KSFT_FAIL}"
+				continue 2
+			fi
+		done
+		ktap_test_skip "${node}"
+	else
+		ktap_test_pass "${node}"
+	fi
+
+done
+
+ktap_print_totals
+exit "${retval}"