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linux/scripts/Makefile.dtbs
Masahiro Yamada 7fb1d1e038 kbuild: move non-boot built-in DTBs to .rodata section 
Commit aab94339cd ("of: Add support for linking device tree blobs
into vmlinux") introduced a mechanism to embed DTBs into vmlinux.

Initially, it was used for wrapping boot DTBs in arch/*/boot/dts/, but
it is now reused for more generic purposes, such as testing.

Built-in DTBs are discarded because KERNEL_DTB() is part of INIT_DATA,
as defined in include/asm-generic/vmlinux.lds.h.

This has not been an issue so far because OF unittests are triggered
during boot, as defined by late_initcall(of_unittest).

However, the recent clk KUnit test additions have caused problems
because KUnit can execute test suites after boot.

For example:

  # echo > /sys/kernel/debug/kunit/clk_register_clk_parent_data_device/run

This command triggers a stack trace because built-in DTBs have already
been freed.

While it is possible to move such test suites from kunit_test_suites to
kunit_test_init_section_suites, it would be preferable to avoid usage
limitations.

This commit moves non-boot built-in DTBs to the .rodata section. Since
these generic DTBs are looked up by name, they do not need to be placed
in the special .dtb.init.rodata section.

Boot DTBs should remain in .dtb.init.rodata because the arch boot code
generally does not know the DT name, thus it uses the __dtb_start symbol
to locate it.

This separation also ensures that the __dtb_start symbol references the
boot DTB. Currently, the .dtb.init.rodata is a mixture of both boot and
non-boot DTBs. The __dtb_start symbol must be followed by the boot DTB,
but we currently rely on the link order (i.e., the order in Makefiles),
which is very fragile.

The implementation is kind of cheesy; the section is .dtb.init.rodata
when $(obj) starts with arch/$(SRCARCH)/boot/dts, and .rodata section
otherwise. This will be refactored later.

Fixes: 5c9dd72d83 ("of: Add a KUnit test for overlays and test managed APIs")
Fixes: 5776526beb ("clk: Add KUnit tests for clk fixed rate basic type")
Fixes: 274aff8711 ("clk: Add KUnit tests for clks registered with struct clk_parent_data")
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
2024-09-30 20:42:52 +09:00

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Makefile
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# SPDX-License-Identifier: GPL-2.0-only
# If CONFIG_OF_ALL_DTBS is enabled, all DT blobs are built
dtb-$(CONFIG_OF_ALL_DTBS) += $(dtb-)
# Composite DTB (i.e. DTB constructed by overlay)
multi-dtb-y := $(call multi-search, $(dtb-y), .dtb, -dtbs)
# Primitive DTB compiled from *.dts
real-dtb-y := $(call real-search, $(dtb-y), .dtb, -dtbs)
# Base DTB that overlay is applied onto
base-dtb-y := $(filter %.dtb, $(call real-search, $(multi-dtb-y), .dtb, -dtbs))
dtb-y := $(addprefix $(obj)/, $(dtb-y))
multi-dtb-y := $(addprefix $(obj)/, $(multi-dtb-y))
real-dtb-y := $(addprefix $(obj)/, $(real-dtb-y))
always-y += $(dtb-y)
targets += $(real-dtb-y)
# dtbs-list
# ---------------------------------------------------------------------------
ifdef need-dtbslist
subdir-dtbslist := $(addsuffix /dtbs-list, $(subdir-ym))
dtb-y += $(subdir-dtbslist)
always-y += $(obj)/dtbs-list
endif
$(subdir-dtbslist): $(obj)/%/dtbs-list: $(obj)/% ;
$(obj)/dtbs-list: $(dtb-y) FORCE
$(call if_changed,gen_order)
# Assembly file to wrap dtb(o)
# ---------------------------------------------------------------------------
builtin-dtb-section = $(if $(filter arch/$(SRCARCH)/boot/dts%, $(obj)),.dtb.init.rodata,.rodata)
# Generate an assembly file to wrap the output of the device tree compiler
quiet_cmd_wrap_S_dtb = WRAP $@
cmd_wrap_S_dtb = { \
symbase=__$(patsubst .%,%,$(suffix $<))_$(subst -,_,$(notdir $*)); \
echo '\#include <asm-generic/vmlinux.lds.h>'; \
echo '.section $(builtin-dtb-section),"a"'; \
echo '.balign STRUCT_ALIGNMENT'; \
echo ".global $${symbase}_begin"; \
echo "$${symbase}_begin:"; \
echo '.incbin "$<" '; \
echo ".global $${symbase}_end"; \
echo "$${symbase}_end:"; \
echo '.balign STRUCT_ALIGNMENT'; \
} > $@
$(obj)/%.dtb.S: $(obj)/%.dtb FORCE
$(call if_changed,wrap_S_dtb)
$(obj)/%.dtbo.S: $(obj)/%.dtbo FORCE
$(call if_changed,wrap_S_dtb)
# Schema check
# ---------------------------------------------------------------------------
ifneq ($(CHECK_DTBS),)
DT_CHECKER ?= dt-validate
DT_CHECKER_FLAGS ?= $(if $(DT_SCHEMA_FILES),-l $(DT_SCHEMA_FILES),-m)
DT_BINDING_DIR := Documentation/devicetree/bindings
DT_TMP_SCHEMA := $(objtree)/$(DT_BINDING_DIR)/processed-schema.json
dtb-check-enabled = $(if $(filter %.dtb, $@),y)
endif
quiet_dtb_check_tag = $(if $(dtb-check-enabled),[C], )
cmd_dtb_check = $(if $(dtb-check-enabled),; $(DT_CHECKER) $(DT_CHECKER_FLAGS) -u $(srctree)/$(DT_BINDING_DIR) -p $(DT_TMP_SCHEMA) $@ || true)
# Overlay
# ---------------------------------------------------------------------------
# NOTE:
# Do not replace $(filter %.dtb %.dtbo, $^) with $(real-prereqs). When a single
# DTB is turned into a multi-blob DTB, $^ will contain header file dependencies
# recorded in the .*.cmd file.
quiet_cmd_fdtoverlay = OVL $(quiet_dtb_check_tag) $@
cmd_fdtoverlay = $(objtree)/scripts/dtc/fdtoverlay -o $@ -i $(filter %.dtb %.dtbo, $^) $(cmd_dtb_check)
$(multi-dtb-y): $(DT_TMP_SCHEMA) FORCE
$(call if_changed,fdtoverlay)
$(call multi_depend, $(multi-dtb-y), .dtb, -dtbs)
# DTC
# ---------------------------------------------------------------------------
DTC ?= $(objtree)/scripts/dtc/dtc
DTC_FLAGS += -Wno-unique_unit_address
# Disable noisy checks by default
ifeq ($(findstring 1,$(KBUILD_EXTRA_WARN)),)
DTC_FLAGS += -Wno-unit_address_vs_reg \
-Wno-avoid_unnecessary_addr_size \
-Wno-alias_paths \
-Wno-graph_child_address \
-Wno-simple_bus_reg
else
DTC_FLAGS += -Wunique_unit_address_if_enabled
endif
ifneq ($(findstring 2,$(KBUILD_EXTRA_WARN)),)
DTC_FLAGS += -Wnode_name_chars_strict \
-Wproperty_name_chars_strict \
-Wunique_unit_address
endif
DTC_FLAGS += $(DTC_FLAGS_$(target-stem))
# Set -@ if the target is a base DTB that overlay is applied onto
DTC_FLAGS += $(if $(filter $(patsubst $(obj)/%,%,$@), $(base-dtb-y)), -@)
DTC_INCLUDE := $(srctree)/scripts/dtc/include-prefixes
dtc_cpp_flags = -Wp,-MMD,$(depfile).pre.tmp -nostdinc -I $(DTC_INCLUDE) -undef -D__DTS__
dtc-tmp = $(subst $(comma),_,$(dot-target).dts.tmp)
quiet_cmd_dtc = DTC $(quiet_dtb_check_tag) $@
cmd_dtc = \
$(HOSTCC) -E $(dtc_cpp_flags) -x assembler-with-cpp -o $(dtc-tmp) $< ; \
$(DTC) -o $@ -b 0 $(addprefix -i,$(dir $<) $(DTC_INCLUDE)) \
$(DTC_FLAGS) -d $(depfile).dtc.tmp $(dtc-tmp) ; \
cat $(depfile).pre.tmp $(depfile).dtc.tmp > $(depfile) \
$(cmd_dtb_check)
$(obj)/%.dtb: $(obj)/%.dts $(DTC) $(DT_TMP_SCHEMA) FORCE
$(call if_changed_dep,dtc)
$(obj)/%.dtbo: $(src)/%.dtso $(DTC) FORCE
$(call if_changed_dep,dtc)
# targets
# ---------------------------------------------------------------------------
targets += $(always-y)
# %.dtb.o <- %.dtb.S <- %.dtb <- %.dts
# %.dtbo.o <- %.dtbo.S <- %.dtbo <- %.dtso
targets += $(call intermediate_targets, .dtb.o, .dtb.S .dtb) \
$(call intermediate_targets, .dtbo.o, .dtbo.S .dtbo)
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