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, 178 insertions, 0 deletions

diff --git a/tools/tracing/rtla/Makefile b/tools/tracing/rtla/Makefile
new file mode 100644
index 000000000..387bc6cc1
--- /dev/null
+++ b/tools/tracing/rtla/Makefile
@@ -0,0 +1,178 @@
+# 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
+
+RTLA		:= $(OUTPUT)rtla
+RTLA_IN		:= $(RTLA)-in.o
+
+LIBSUBCMD_DIR = $(srctree)/tools/lib/subcmd/
+ifneq ($(OUTPUT),)
+  LIBSUBCMD_OUTPUT = $(abspath $(OUTPUT))/libsubcmd
+else
+  LIBSUBCMD_OUTPUT = $(CURDIR)/libsubcmd
+endif
+LIBSUBCMD = $(LIBSUBCMD_OUTPUT)/libsubcmd.a
+LIBSUBCMD_INCLUDES = $(LIBSUBCMD_OUTPUT)/include
+LIBSUBCMD_MAKEFLAGS = O=$(LIBSUBCMD_OUTPUT) DESTDIR=$(LIBSUBCMD_OUTPUT) prefix= subdir=
+
+TOOLS_INCLUDES = -I$(srctree)/tools/include
+
+ifneq ($(OUTPUT),)
+  LIB_OUTPUT = $(abspath $(OUTPUT))/lib
+else
+  LIB_OUTPUT = $(CURDIR)/lib
+endif
+
+LIB_CTYPE = $(LIB_OUTPUT)/ctype.o
+LIB_CTYPE_SRC = $(srctree)/tools/lib/ctype.c
+
+LIB_STRING = $(LIB_OUTPUT)/string.o
+LIB_STRING_SRC = $(srctree)/tools/lib/string.c
+
+LIB_STR_ERROR_R = $(LIB_OUTPUT)/str_error_r.o
+LIB_STR_ERROR_R_SRC = $(srctree)/tools/lib/str_error_r.c
+
+VERSION		:= $(shell sh -c "make -sC ../../.. kernelversion | grep -v make")
+DOCSRC		:= ../../../Documentation/tools/rtla/
+
+FEATURE_TESTS	:= libtraceevent
+FEATURE_TESTS	+= libtracefs
+FEATURE_TESTS	+= libcpupower
+FEATURE_TESTS	+= libcheck
+FEATURE_TESTS	+= libbpf
+FEATURE_TESTS	+= clang-bpf-co-re
+FEATURE_TESTS	+= bpftool-skeletons
+FEATURE_DISPLAY	:= libtraceevent
+FEATURE_DISPLAY	+= libtracefs
+FEATURE_DISPLAY	+= libcpupower
+FEATURE_DISPLAY	+= libcheck
+FEATURE_DISPLAY	+= libbpf
+FEATURE_DISPLAY	+= clang-bpf-co-re
+FEATURE_DISPLAY	+= bpftool-skeletons
+
+all: $(RTLA)
+
+include $(srctree)/tools/build/Makefile.include
+include Makefile.rtla
+include tests/unit/Makefile.unit
+
+# check for dependencies only on required targets
+NON_CONFIG_TARGETS := clean install tarball doc doc_clean doc_install
+
+config		:= 1
+ifdef MAKECMDGOALS
+ifeq ($(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) $(TOOLS_INCLUDES) -I$(LIBSUBCMD_INCLUDES)
+
+export CFLAGS OUTPUT srctree
+
+ifeq ($(BUILD_BPF_SKEL),1)
+src/timerlat.bpf.o: src/timerlat.bpf.c
+	$(QUIET_CLANG)$(CLANG) -g -O2 -target bpf -c $(filter %.c,$^) -o $@
+
+src/timerlat.skel.h: src/timerlat.bpf.o
+	$(QUIET_GENSKEL)$(SYSTEM_BPFTOOL) gen skeleton $< > $@
+
+example/timerlat_bpf_action.o: example/timerlat_bpf_action.c
+	$(QUIET_CLANG)$(CLANG) -g -O2 -target bpf -c $(filter %.c,$^) -o $@
+
+tests/bpf/bpf_action_map.o: tests/bpf/bpf_action_map.c
+	$(QUIET_CLANG)$(CLANG) -g -O2 -target bpf -c $(filter %.c,$^) -o $@
+else
+src/timerlat.skel.h:
+	$(Q)echo '/* BPF skeleton is disabled */' > src/timerlat.skel.h
+
+example/timerlat_bpf_action.o: example/timerlat_bpf_action.c
+	$(Q)echo "BPF skeleton support is disabled, skipping example/timerlat_bpf_action.o"
+
+tests/bpf/bpf_action_map.o: tests/bpf/bpf_action_map.c
+	$(Q)echo "BPF skeleton support is disabled, skipping tests/bpf/bpf_action_map.o"
+endif
+
+$(RTLA): $(RTLA_IN) $(LIBSUBCMD) $(LIB_CTYPE) $(LIB_STRING) $(LIB_STR_ERROR_R)
+	$(QUIET_LINK)$(CC) $(LDFLAGS) -o $(RTLA) $(RTLA_IN) $(LIBSUBCMD) $(LIB_CTYPE) $(LIB_STRING) $(LIB_STR_ERROR_R) $(EXTLIBS)
+
+static: $(RTLA_IN) $(LIBSUBCMD) $(LIB_CTYPE) $(LIB_STRING) $(LIB_STR_ERROR_R)
+	$(eval LDFLAGS += -static)
+	$(QUIET_LINK)$(CC) -static $(LDFLAGS) -o $(RTLA)-static $(RTLA_IN) $(LIBSUBCMD) $(LIB_CTYPE) $(LIB_STRING) $(LIB_STR_ERROR_R) $(EXTLIBS)
+
+rtla.%: fixdep FORCE
+	make -f $(srctree)/tools/build/Makefile.build dir=. $@
+
+$(RTLA_IN): fixdep FORCE src/timerlat.skel.h $(LIBSUBCMD_INCLUDES)
+	make $(build)=rtla
+
+$(LIBSUBCMD_OUTPUT):
+	$(Q)$(MKDIR) -p $@
+
+$(LIBSUBCMD_INCLUDES): FORCE | $(LIBSUBCMD_OUTPUT)
+	$(Q)$(MAKE) -C $(LIBSUBCMD_DIR) $(LIBSUBCMD_MAKEFLAGS) \
+		install_headers
+
+$(LIBSUBCMD): FORCE | $(LIBSUBCMD_OUTPUT)
+	$(Q)$(MAKE) -C $(LIBSUBCMD_DIR) $(LIBSUBCMD_MAKEFLAGS) \
+		$@
+
+$(LIB_OUTPUT):
+	$(Q)$(MKDIR) -p $@
+
+$(LIB_STR_ERROR_R): $(LIB_STR_ERROR_R_SRC) | $(LIB_OUTPUT)
+	$(QUIET_CC)$(CC) $(CFLAGS) -c -o $@ $<
+
+$(LIB_STRING): $(LIB_STRING_SRC) | $(LIB_OUTPUT)
+	$(QUIET_CC)$(CC) $(CFLAGS) -c -o $@ $<
+
+$(LIB_CTYPE): $(LIB_CTYPE_SRC) | $(LIB_OUTPUT)
+	$(QUIET_CC)$(CC) $(CFLAGS) -c -o $@ $<
+
+libsubcmd-clean:
+	$(call QUIET_CLEAN, libsubcmd)
+	$(Q)$(RM) -r -- $(LIBSUBCMD_OUTPUT)
+
+lib-clean:
+	$(call QUIET_CLEAN, lib)
+	$(Q)$(RM) -r -- $(LIB_OUTPUT)
+
+clean: doc_clean fixdep-clean libsubcmd-clean lib-clean
+	$(call QUIET_CLEAN, rtla)
+	$(Q)find . -name '*.o' -delete -o -name '\.*.cmd' -delete -o -name '\.*.d' -delete
+	$(Q)rm -f rtla rtla-static fixdep FEATURE-DUMP rtla-*
+	$(Q)rm -rf feature
+	$(Q)rm -f src/timerlat.bpf.o src/timerlat.skel.h example/timerlat_bpf_action.o
+	$(Q)rm -f $(UNIT_TESTS)
+
+check: $(RTLA) tests/bpf/bpf_action_map.o
+	RTLA=$(RTLA) BPFTOOL=$(SYSTEM_BPFTOOL) prove -o -f -v tests/
+examples: example/timerlat_bpf_action.o
+.PHONY: FORCE clean check