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>

1 files changed, 75 insertions, 0 deletions

diff --git a/scripts/package/install-extmod-build b/scripts/package/install-extmod-build
new file mode 100755
index 000000000..f12e1ffe4
--- /dev/null
+++ b/scripts/package/install-extmod-build
@@ -0,0 +1,75 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0-only
+
+set -eu
+
+destdir=${1}
+
+is_enabled() {
+	grep -q "^$1=y" include/config/auto.conf
+}
+
+find_in_scripts() {
+	find scripts \
+		\( -name atomic -o -name dtc -o -name kconfig -o -name package \) -prune -o \
+		! -name unifdef -a ! -name mk_elfconfig -a \( -type f -o -type l \) -print
+}
+
+mkdir -p "${destdir}"
+
+(
+	cd "${srctree}"
+	echo Makefile
+	find "arch/${SRCARCH}" -maxdepth 1 -name 'Makefile*'
+	find "arch/${SRCARCH}" -name generated -prune -o -name include -type d -print
+	find "arch/${SRCARCH}" -name Kbuild.platforms -o -name Platform
+	find include \( -name config -o -name generated \) -prune -o \( -type f -o -type l \) -print
+	find_in_scripts
+) | tar -c -f - -C "${srctree}" -T - | tar -xf - -C "${destdir}"
+
+{
+	if is_enabled CONFIG_OBJTOOL; then
+		echo tools/objtool/objtool
+	fi
+
+	if is_enabled CONFIG_DEBUG_INFO_BTF_MODULES; then
+		echo tools/bpf/resolve_btfids/resolve_btfids
+	fi
+
+	echo Module.symvers
+	echo "arch/${SRCARCH}/include/generated"
+	echo include/config/auto.conf
+	echo include/config/kernel.release
+	echo include/generated
+	find_in_scripts
+
+	if is_enabled CONFIG_GCC_PLUGINS; then
+		find scripts/gcc-plugins -name '*.so'
+	fi
+} | tar -c -f - -T - | tar -xf - -C "${destdir}"
+
+# When ${CC} and ${HOSTCC} differ, rebuild host programs using ${CC}.
+#
+# This caters to host programs that participate in Kbuild. objtool and
+# resolve_btfids are out of scope.
+if [ "${CC}" != "${HOSTCC}" ]; then
+	cat "${destdir}/scripts/Makefile" - <<-'EOF' > "${destdir}/scripts/Kbuild"
+	subdir-y += basic
+	hostprogs-always-y += mod/modpost
+	mod/modpost-objs := $(addprefix mod/, modpost.o file2alias.o sumversion.o symsearch.o)
+	EOF
+
+	# HOSTCXX is not overridden. The C++ compiler is used to build:
+	# - scripts/kconfig/qconf, which is unneeded for external module builds
+	# - GCC plugins, which will not work on the installed system even after
+	#   being rebuilt.
+	#
+	# Clear VPATH and srcroot because the source files reside in the output
+	# directory.
+	# shellcheck disable=SC2016 # $(MAKE) and $(build) will be expanded by Make
+	"${MAKE}" run-command KBUILD_RUN_COMMAND='+$(MAKE) HOSTCC="'"${CC}"'" VPATH= srcroot=. $(build)='"$(realpath --relative-to=. "${destdir}")"/scripts
+
+	rm -f "${destdir}/scripts/Kbuild"
+fi
+
+find "${destdir}" \( -name '.*.cmd' -o -name '*.o' \) -delete