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, 165 insertions, 0 deletions

diff --git a/scripts/Makefile.host b/scripts/Makefile.host
new file mode 100644
index 000000000..c1dedf646
--- /dev/null
+++ b/scripts/Makefile.host
@@ -0,0 +1,165 @@
+# SPDX-License-Identifier: GPL-2.0
+
+# LEX
+# ---------------------------------------------------------------------------
+quiet_cmd_flex = LEX     $@
+      cmd_flex = $(LEX) -o$@ -L $<
+
+$(obj)/%.lex.c: $(src)/%.l FORCE
+	$(call if_changed,flex)
+
+# YACC
+# ---------------------------------------------------------------------------
+quiet_cmd_bison = YACC    $(basename $@).[ch]
+      cmd_bison = $(YACC) -o $(basename $@).c --defines=$(basename $@).h -t -l $<
+
+$(obj)/%.tab.c $(obj)/%.tab.h: $(src)/%.y FORCE
+	$(call if_changed,bison)
+
+# ==========================================================================
+# Building binaries on the host system
+# Binaries are used during the compilation of the kernel, for example
+# to preprocess a data file.
+#
+# Both C and C++ are supported, but preferred language is C for such utilities.
+# Rust is also supported, but it may only be used in scenarios where a Rust
+# toolchain is required to be available (e.g. when  `CONFIG_RUST` is enabled).
+#
+# Sample syntax (see Documentation/kbuild/makefiles.rst for reference)
+# hostprogs := bin2hex
+# Will compile bin2hex.c and create an executable named bin2hex
+#
+# hostprogs     := lxdialog
+# lxdialog-objs := checklist.o lxdialog.o
+# Will compile lxdialog.c and checklist.c, and then link the executable
+# lxdialog, based on checklist.o and lxdialog.o
+#
+# hostprogs       := qconf
+# qconf-cxxobjs   := qconf.o
+# qconf-objs      := menu.o
+# Will compile qconf as a C++ program, and menu as a C program.
+# They are linked as C++ code to the executable qconf
+#
+# hostprogs   := target
+# target-rust := y
+# Will compile `target` as a Rust program, using `target.rs` as the crate root.
+# The crate may consist of several source files.
+
+# C code
+# Executables compiled from a single .c file
+host-csingle	:= $(foreach m,$(hostprogs), \
+			$(if $($(m)-objs)$($(m)-cxxobjs)$($(m)-rust),,$(m)))
+
+# C executables linked based on several .o files
+host-cmulti	:= $(foreach m,$(hostprogs),\
+		   $(if $($(m)-cxxobjs)$($(m)-rust),,$(if $($(m)-objs),$(m))))
+
+# Object (.o) files compiled from .c files
+host-cobjs	:= $(sort $(foreach m,$(hostprogs),$($(m)-objs)))
+
+# C++ code
+# C++ executables compiled from at least one .cc file
+# and zero or more .c files
+host-cxxmulti	:= $(foreach m,$(hostprogs),$(if $($(m)-cxxobjs),$(m)))
+
+# C++ Object (.o) files compiled from .cc files
+host-cxxobjs	:= $(sort $(foreach m,$(host-cxxmulti),$($(m)-cxxobjs)))
+
+# Rust code
+# Executables compiled from a single Rust crate (which may consist of
+# one or more .rs files)
+host-rust	:= $(foreach m,$(hostprogs),$(if $($(m)-rust),$(m)))
+
+host-csingle	:= $(addprefix $(obj)/,$(host-csingle))
+host-cmulti	:= $(addprefix $(obj)/,$(host-cmulti))
+host-cobjs	:= $(addprefix $(obj)/,$(host-cobjs))
+host-cxxmulti	:= $(addprefix $(obj)/,$(host-cxxmulti))
+host-cxxobjs	:= $(addprefix $(obj)/,$(host-cxxobjs))
+host-rust	:= $(addprefix $(obj)/,$(host-rust))
+
+#####
+# Handle options to gcc. Support building with separate output directory
+
+hostc_flags    = -Wp,-MMD,$(depfile) \
+                 $(KBUILD_HOSTCFLAGS) $(HOST_EXTRACFLAGS) \
+                 $(HOSTCFLAGS_$(target-stem).o)
+hostcxx_flags  = -Wp,-MMD,$(depfile) \
+                 $(KBUILD_HOSTCXXFLAGS) $(HOST_EXTRACXXFLAGS) \
+                 $(HOSTCXXFLAGS_$(target-stem).o)
+
+# `--out-dir` is required to avoid temporaries being created by `rustc` in the
+# current working directory, which may be not accessible in the out-of-tree
+# modules case.
+hostrust_flags = --out-dir $(dir $@) --emit=dep-info=$(depfile) \
+		 -Clinker-flavor=gcc -Clinker=$(HOSTCC) \
+		 -Clink-args='$(call escsq,$(KBUILD_HOSTLDFLAGS))' \
+                 $(KBUILD_HOSTRUSTFLAGS) $(HOST_EXTRARUSTFLAGS) \
+                 $(HOSTRUSTFLAGS_$(target-stem))
+
+# $(obj) for including generated headers from checkin source files
+ifdef building_out_of_srctree
+hostc_flags   += -I $(obj)
+hostcxx_flags += -I $(obj)
+endif
+
+#####
+# Compile programs on the host
+
+# Create executable from a single .c file
+# host-csingle -> Executable
+quiet_cmd_host-csingle 	= HOSTCC  $@
+      cmd_host-csingle	= $(HOSTCC) $(hostc_flags) $(KBUILD_HOSTLDFLAGS) -o $@ $< \
+		$(KBUILD_HOSTLDLIBS) $(HOSTLDLIBS_$(target-stem))
+$(host-csingle): $(obj)/%: $(obj)/%.c FORCE
+	$(call if_changed_dep,host-csingle)
+
+# Link an executable based on list of .o files, all plain c
+# host-cmulti -> executable
+quiet_cmd_host-cmulti	= HOSTLD  $@
+      cmd_host-cmulti	= $(HOSTCC) $(KBUILD_HOSTLDFLAGS) -o $@ \
+			  $(addprefix $(obj)/, $($(target-stem)-objs)) \
+			  $(KBUILD_HOSTLDLIBS) $(HOSTLDLIBS_$(target-stem))
+$(host-cmulti): FORCE
+	$(call if_changed,host-cmulti)
+$(call multi_depend, $(host-cmulti), , -objs)
+
+# Create .o file from a single .c file
+# host-cobjs -> .o
+quiet_cmd_host-cobjs	= HOSTCC  $@
+      cmd_host-cobjs	= $(HOSTCC) $(hostc_flags) -c -o $@ $<
+$(host-cobjs): $(obj)/%.o: $(obj)/%.c FORCE
+	$(call if_changed_dep,host-cobjs)
+
+# Link an executable based on list of .o files, a mixture of .c and .cc
+# host-cxxmulti -> executable
+quiet_cmd_host-cxxmulti	= HOSTLD  $@
+      cmd_host-cxxmulti	= $(HOSTCXX) $(KBUILD_HOSTLDFLAGS) -o $@ \
+			  $(foreach o,objs cxxobjs,\
+			  $(addprefix $(obj)/, $($(target-stem)-$(o)))) \
+			  $(KBUILD_HOSTLDLIBS) $(HOSTLDLIBS_$(target-stem))
+$(host-cxxmulti): FORCE
+	$(call if_changed,host-cxxmulti)
+$(call multi_depend, $(host-cxxmulti), , -objs -cxxobjs)
+
+# Create .o file from a single .cc (C++) file
+quiet_cmd_host-cxxobjs	= HOSTCXX $@
+      cmd_host-cxxobjs	= $(HOSTCXX) $(hostcxx_flags) -c -o $@ $<
+$(host-cxxobjs): $(obj)/%.o: $(obj)/%.cc FORCE
+	$(call if_changed_dep,host-cxxobjs)
+
+# Create executable from a single Rust crate (which may consist of
+# one or more `.rs` files)
+# host-rust -> Executable
+quiet_cmd_host-rust	= HOSTRUSTC $@
+      cmd_host-rust	= \
+	$(HOSTRUSTC) $(hostrust_flags) --emit=link=$@ $<
+$(host-rust): $(obj)/%: $(src)/%.rs FORCE
+	+$(call if_changed_dep,host-rust)
+
+targets += $(host-csingle) $(host-cmulti) $(host-cobjs) \
+	   $(host-cxxmulti) $(host-cxxobjs) $(host-rust)
+
+# %.lex.o <- %.lex.c <- %.l
+# %.tab.o <- %.tab.[ch] <- %.y
+targets += $(call intermediate_targets, .lex.o, .lex.c) \
+           $(call intermediate_targets, .tab.o, .tab.c .tab.h)