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, 181 insertions, 0 deletions

diff --git a/tools/build/Makefile.build b/tools/build/Makefile.build
new file mode 100644
index 000000000..ad69efdd4
--- /dev/null
+++ b/tools/build/Makefile.build
@@ -0,0 +1,181 @@
+# SPDX-License-Identifier: GPL-2.0
+###
+# Main build makefile.
+#
+#  Lots of this code have been borrowed or heavily inspired from parts
+#  of kbuild code, which is not credited, but mostly developed by:
+#
+#  Copyright (C) Sam Ravnborg <sam@mars.ravnborg.org>, 2015
+#  Copyright (C) Linus Torvalds <torvalds@linux-foundation.org>, 2015
+#
+
+PHONY := __build
+__build:
+
+build-dir := $(srctree)/tools/build
+
+# Define $(fixdep) for dep-cmd function
+ifeq ($(OUTPUT),)
+  fixdep := $(build-dir)/fixdep
+else
+  fixdep := $(OUTPUT)/fixdep
+endif
+
+# Generic definitions
+include $(build-dir)/Build.include
+
+# do not force detected configuration
+-include $(OUTPUT).config-detected
+
+# Init all relevant variables used in build files so
+# 1) they have correct type
+# 2) they do not inherit any value from the environment
+subdir-y     :=
+obj-y        :=
+subdir-y     :=
+subdir-obj-y :=
+
+# Build definitions
+build-file := $(dir)/Build
+-include $(build-file)
+
+quiet_cmd_flex  = FLEX    $@
+quiet_cmd_bison = BISON   $@
+quiet_cmd_test  = TEST    $@
+
+# Create directory unless it exists
+quiet_cmd_mkdir = MKDIR   $(dir $@)
+      cmd_mkdir = mkdir -p $(dir $@)
+     rule_mkdir = $(if $(wildcard $(dir $@)),,@$(call echo-cmd,mkdir) $(cmd_mkdir))
+
+# Compile command
+quiet_cmd_cc_o_c = CC      $@
+      cmd_cc_o_c = $(CC) $(c_flags) -c -o $@ $<
+
+quiet_cmd_host_cc_o_c = HOSTCC  $@
+      cmd_host_cc_o_c = $(HOSTCC) $(host_c_flags) -c -o $@ $<
+
+quiet_cmd_cxx_o_c = CXX     $@
+      cmd_cxx_o_c = $(CXX) $(cxx_flags) -c -o $@ $<
+
+quiet_cmd_cpp_i_c = CPP     $@
+      cmd_cpp_i_c = $(CC) $(c_flags) -E -o $@ $<
+
+quiet_cmd_cc_s_c = AS      $@
+      cmd_cc_s_c = $(CC) $(c_flags) -S -o $@ $<
+
+quiet_cmd_gen = GEN     $@
+
+# Link agregate command
+# If there's nothing to link, create empty $@ object.
+quiet_cmd_ld_multi = LD      $@
+      cmd_ld_multi = $(if $(strip $(obj-y)),\
+                     printf "$(objprefix)%s " $(patsubst $(objprefix)%,%,$(filter $(obj-y),$^)) | \
+                     xargs $(LD) -r -o $@,rm -f $@; $(AR) rcs $@)
+
+quiet_cmd_host_ld_multi = HOSTLD  $@
+      cmd_host_ld_multi = $(if $(strip $(obj-y)),\
+                          printf "$(objprefix)%s " $(patsubst $(objprefix)%,%,$(filter $(obj-y),$^)) | \
+                          xargs $(HOSTLD) -r -o $@,rm -f $@; $(HOSTAR) rcs $@)
+
+rust_common_cmd = \
+	$(RUSTC) $(rust_flags) \
+	--crate-type staticlib -L $(objtree)/rust/ \
+	--emit=dep-info=$(depfile),link
+
+quiet_cmd_rustc_a_rs = $(RUSTC) $(quiet_modtag) $@
+      cmd_rustc_a_rs = $(rust_common_cmd) -o $@ -g $< $(cmd_objtool)
+
+ifneq ($(filter $(obj),$(hostprogs)),)
+  host = host_
+endif
+
+# Build rules
+$(OUTPUT)%.o: %.c FORCE
+	$(call rule_mkdir)
+	$(call if_changed_dep,$(host)cc_o_c)
+
+$(OUTPUT)%.o: %.cpp FORCE
+	$(call rule_mkdir)
+	$(call if_changed_dep,cxx_o_c)
+
+$(OUTPUT)%.o: %.S FORCE
+	$(call rule_mkdir)
+	$(call if_changed_dep,$(host)cc_o_c)
+
+$(OUTPUT)%.i: %.c FORCE
+	$(call rule_mkdir)
+	$(call if_changed_dep,cpp_i_c)
+
+$(OUTPUT)%.s: %.S FORCE
+	$(call rule_mkdir)
+	$(call if_changed_dep,cpp_i_c)
+
+$(OUTPUT)%.s: %.c FORCE
+	$(call rule_mkdir)
+	$(call if_changed_dep,cc_s_c)
+
+# it's recommended to build a static rust library, when a foreight (to rust)
+# linker is used.
+$(OUTPUT)%.a: %.rs FORCE
+	$(call rule_mkdir)
+	$(call if_changed_dep,rustc_a_rs)
+
+# bison and flex files are generated in the OUTPUT directory
+# so it needs a separate rule to depend on them properly
+$(OUTPUT)%-bison.o: $(OUTPUT)%-bison.c FORCE
+	$(call rule_mkdir)
+	$(call if_changed_dep,$(host)cc_o_c)
+
+$(OUTPUT)%-flex.o: $(OUTPUT)%-flex.c FORCE
+	$(call rule_mkdir)
+	$(call if_changed_dep,$(host)cc_o_c)
+
+# Gather build data:
+#   obj-y        - list of build objects
+#   subdir-y     - list of directories to nest
+#   subdir-obj-y - list of directories objects 'dir/$(obj)-in.o'
+obj-y        := $($(obj)-y)
+subdir-y     := $(patsubst %/,%,$(filter %/, $(obj-y)))
+obj-y        := $(patsubst %/, %/$(obj)-in.o, $(obj-y))
+subdir-obj-y := $(filter %/$(obj)-in.o, $(obj-y))
+
+# '$(OUTPUT)/dir' prefix to all objects
+objprefix    := $(subst ./,,$(OUTPUT)$(dir)/)
+obj-y        := $(addprefix $(objprefix),$(obj-y))
+subdir-obj-y := $(addprefix $(objprefix),$(subdir-obj-y))
+
+# Separate out test log files from real build objects.
+test-y       := $(filter %_log, $(obj-y))
+obj-y        := $(filter-out %_log, $(obj-y))
+
+# Final '$(obj)-in.o' object
+in-target := $(objprefix)$(obj)-in.o
+
+PHONY += $(subdir-y)
+
+$(subdir-y):
+	$(Q)$(MAKE) -f $(build-dir)/Makefile.build dir=$(dir)/$@ obj=$(obj)
+
+$(sort $(subdir-obj-y)): $(subdir-y) ;
+
+$(in-target): $(obj-y) $(test-y) FORCE
+	$(call rule_mkdir)
+	$(call if_changed,$(host)ld_multi)
+
+__build: $(in-target)
+	@:
+
+PHONY += FORCE
+FORCE:
+
+# Include all cmd files to get all the dependency rules
+# for all objects included
+targets   := $(wildcard $(sort $(obj-y) $(in-target) $(MAKECMDGOALS)))
+cmd_files := $(wildcard $(foreach f,$(targets),$(dir $(f)).$(notdir $(f)).cmd))
+
+ifneq ($(cmd_files),)
+  include $(cmd_files)
+endif
+
+.PHONY: $(PHONY)