kbuild: rust: keep Rust objects out of Clang LTO with inline helpersgrafted

Under `CONFIG_LTO_CLANG` + `CONFIG_RUST_INLINE_HELPERS`, one may hit
`objtool` errors such as:

    vmlinux.o: error: objtool: _R..._3Gsp4boot+0xd6a:
    can't find jump dest instruction at .text._R..._3Gsp4boot+0x1dfd

The reason is that in such builds, the Clang invocation that compiles
the combined Rust plus helpers bitcode emits LLVM bitcode (again) --
the final code generation happens in the linker's LTO step, which the
`-mllvm` trap options passed to Clang do not reach.

This, in turn, means that unreachable traps are missing, and the
impossible paths do not merely fallthrough to the next symbol, but past
the end of their own section, since LTO builds place each function in
its own section.

Thus filter `CC_FLAGS_LTO` out of the Clang invocation, so that it always
emits machine code directly, with the traps in place.

Assisted-by: LLM
Cc: Gary Guo <gary@garyguo.net>
Cc: Boqun Feng <boqun@kernel.org>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Matthew Maurer <mmaurer@google.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers into Rust")
Acked-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260816133233.197500-2-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

1 files changed, 103 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/Makefile b/Documentation/devicetree/bindings/Makefile
new file mode 100644
index 000000000..00149e824
--- /dev/null
+++ b/Documentation/devicetree/bindings/Makefile
@@ -0,0 +1,103 @@
+# SPDX-License-Identifier: GPL-2.0
+DT_DOC_CHECKER ?= dt-doc-validate
+DT_EXTRACT_EX ?= dt-extract-example
+DT_MK_SCHEMA ?= dt-mk-schema
+
+DT_SCHEMA_LINT = $(shell which yamllint || \
+  echo "warning: python package 'yamllint' not installed, skipping" >&2)
+
+DT_SCHEMA_MIN_VERSION = 2023.9
+
+PHONY += check_dtschema_version
+check_dtschema_version:
+	@which $(DT_DOC_CHECKER) >/dev/null || \
+		{ echo "Error: '$(DT_DOC_CHECKER)' not found!" >&2; \
+		  echo "Ensure dtschema python package is installed and in your PATH." >&2; \
+		  echo "Current PATH is:" >&2; \
+		  echo "$$PATH" >&2; false; }
+	@{ echo $(DT_SCHEMA_MIN_VERSION); \
+	$(DT_DOC_CHECKER) --version 2>/dev/null || echo 0; } | sort -Vc >/dev/null || \
+	{ echo "ERROR: dtschema minimum version is v$(DT_SCHEMA_MIN_VERSION)" >&2; false; }
+
+quiet_cmd_extract_ex = DTEX    $@
+      cmd_extract_ex = $(DT_EXTRACT_EX) $< > $@
+
+$(obj)/%.example.dts: $(src)/%.yaml check_dtschema_version FORCE
+	$(call if_changed,extract_ex)
+
+find_all_cmd = find $(src) \( -name '*.yaml' ! \
+		-name 'processed-schema*' \)
+
+find_cmd = $(find_all_cmd) | \
+		sed 's|^$(srctree)/||' | \
+		grep -F -e "$(subst :," -e ",$(DT_SCHEMA_FILES))" | \
+		sed 's|^|$(srctree)/|'
+CHK_DT_EXAMPLES := $(patsubst $(srctree)/%.yaml,%.example.dtb, \
+			      $(shell $(find_cmd) | xargs grep -l '^examples:'))
+
+quiet_cmd_yamllint = LINT    $(src)
+      cmd_yamllint = ($(find_cmd) | \
+                     xargs -n200 -P$$(nproc) \
+		     $(DT_SCHEMA_LINT) -f parsable -c $(src)/.yamllint >&2) \
+		     && touch $@ || true
+
+quiet_cmd_chk_bindings = CHKDT   $(src)
+      cmd_chk_bindings = ($(find_cmd) | \
+			  xargs -n200 -P$$(nproc) $(DT_DOC_CHECKER) -u $(src)) \
+			  && touch $@ || true
+
+DT_CHK_STYLE = $(srctree)/scripts/dtc/dt-check-style
+
+# Feed the file list to the checker via @argfile in a single Python
+# process so the ruamel.yaml import is paid once. scripts/jobserver-exec
+# claims slots from the GNU make jobserver and exposes the count via
+# $PARALLELISM, which dt-check-style picks up to size its worker pool.
+quiet_cmd_chk_style = STYLE   $(src)
+      cmd_chk_style = f=$$(mktemp) && $(find_cmd) > $$f && \
+		      $(PYTHON3) $(srctree)/scripts/jobserver-exec \
+		      $(PYTHON3) $(DT_CHK_STYLE) @$$f \
+		      && touch $@ || true; rm -f $$f
+
+quiet_cmd_mk_schema = SCHEMA  $@
+      cmd_mk_schema = f=$$(mktemp) ; \
+                      $(find_all_cmd) > $$f ; \
+                      $(DT_MK_SCHEMA) -j $(DT_MK_SCHEMA_FLAGS) @$$f > $@ ; \
+		      rm -f $$f
+
+DT_DOCS = $(patsubst $(srctree)/%,%,$(shell $(find_all_cmd)))
+
+override DTC_FLAGS := \
+	-Wno-avoid_unnecessary_addr_size \
+	-Wno-unique_unit_address \
+	-Wunique_unit_address_if_enabled
+
+$(obj)/processed-schema.json: $(DT_DOCS) check_dtschema_version FORCE
+	$(call if_changed,mk_schema)
+
+targets += .dt-binding.checked .yamllint.checked .dt-style.checked
+$(obj)/.yamllint.checked: $(DT_DOCS) $(src)/.yamllint FORCE
+	$(if $(DT_SCHEMA_LINT),$(call if_changed,yamllint),)
+
+$(obj)/.dt-binding.checked: $(DT_DOCS) FORCE
+	$(call if_changed,chk_bindings)
+
+$(obj)/.dt-style.checked: $(DT_DOCS) FORCE
+	$(call if_changed,chk_style)
+
+always-y += processed-schema.json
+targets += $(patsubst $(obj)/%,%, $(CHK_DT_EXAMPLES))
+targets += $(patsubst $(obj)/%.dtb,%.dts, $(CHK_DT_EXAMPLES))
+
+# Hack: avoid 'Argument list too long' error for 'make clean'. Remove most of
+# build artifacts here before they are processed by scripts/Makefile.clean
+clean-files = $(shell find $(obj) \( -name '*.example.dts' -o \
+			-name '*.example.dtb' \) -delete 2>/dev/null)
+
+dt_compatible_check: $(obj)/processed-schema.json
+	$(Q)$(srctree)/scripts/dtc/dt-extract-compatibles $(srctree) | xargs dt-check-compatible -v -s $<
+
+PHONY += dt_binding_check_one
+dt_binding_check_one: $(obj)/.dt-binding.checked $(obj)/.yamllint.checked $(obj)/.dt-style.checked
+
+PHONY += dt_binding_check
+dt_binding_check: dt_binding_check_one $(CHK_DT_EXAMPLES)