Date:   Wed, 28 Sep 2022 21:30:12 +0200
From:   Nicolas Schier <nicolas@...sle.eu>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <nathan@...nel.org>
Subject: Re: [PATCH v3 2/7] kbuild: list sub-directories in ./Kbuild

On Sun, 25 Sep 2022 03:19:10 +0900 Masahiro Yamada wrote:
> Use the ordinary obj-y syntax to list subdirectories.
> 
> Note1:
> Previously, the link order of lib-y depended on CONFIG_MODULES; lib-y
> was linked before drivers-y when CONFIG_MODULES=y, otherwise after
> drivers-y. This was a bug of commit 7273ad2b08f8 ("kbuild: link lib-y
> objects to vmlinux forcibly when CONFIG_MODULES=y"), but it was not a
> big deal after all. Now, all objects listed in lib-y are linked last,
> irrespective of CONFIG_MODULES.
> 
> Note2:
> Finally, the single target build in arch/*/lib/ works correctly. There was
> a bug report about this. [1]
> 
>   $ make ARCH=arm arch/arm/lib/findbit.o
>     CALL    scripts/checksyscalls.sh
>     AS      arch/arm/lib/findbit.o
> 
> [1]: https://lore.kernel.org/linux-kbuild/YvUQOwL6lD4%2F5%2FU6@shell.armlinux.org.uk/
> 
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> ---

Reviewed-by: Nicolas Schier <nicolas@...sle.eu>

> 
> Changes in v3:
>   - Also move libs-y to fix the bug reported by:
>      https://lore.kernel.org/linux-kbuild/20220921043946.GA1355561@roeck-us.net/
> 
>  Kbuild               | 24 ++++++++++++++++
>  Makefile             | 65 ++++++++++++++------------------------------
>  scripts/Makefile.lib |  2 ++
>  3 files changed, 46 insertions(+), 45 deletions(-)
> 
> diff --git a/Kbuild b/Kbuild
> index 0b9e8a16a621..8a37584d1fd6 100644
> --- a/Kbuild
> +++ b/Kbuild
> @@ -72,3 +72,27 @@ $(atomic-checks): $(obj)/.checked-%: include/linux/atomic/%  FORCE
>  PHONY += prepare
>  prepare: $(offsets-file) missing-syscalls $(atomic-checks)
>  	@:
> +
> +# Ordinary directory descending
> +# ---------------------------------------------------------------------------
> +
> +obj-y			+= init/
> +obj-y			+= usr/
> +obj-y			+= arch/$(SRCARCH)/
> +obj-y			+= $(ARCH_CORE)
> +obj-y			+= kernel/
> +obj-y			+= certs/
> +obj-y			+= mm/
> +obj-y			+= fs/
> +obj-y			+= ipc/
> +obj-y			+= security/
> +obj-y			+= crypto/
> +obj-$(CONFIG_BLOCK)	+= block/
> +obj-$(CONFIG_IO_URING)	+= io_uring/
> +obj-y			+= $(ARCH_LIB)
> +obj-y			+= drivers/
> +obj-y			+= sound/
> +obj-$(CONFIG_SAMPLES)	+= samples/
> +obj-$(CONFIG_NET)	+= net/
> +obj-y			+= virt/
> +obj-y			+= $(ARCH_DRIVERS)
> diff --git a/Makefile b/Makefile
> index eb4bbbc898d0..f793c3b1eaec 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -676,11 +676,8 @@ endif
>  
>  ifeq ($(KBUILD_EXTMOD),)
>  # Objects we will link into vmlinux / subdirs we need to visit
> -core-y		:= init/ usr/ arch/$(SRCARCH)/
> -drivers-y	:= drivers/ sound/
> -drivers-$(CONFIG_SAMPLES) += samples/
> -drivers-$(CONFIG_NET) += net/
> -drivers-y	+= virt/
> +core-y		:=
> +drivers-y	:=
>  libs-y		:= lib/
>  endif # KBUILD_EXTMOD
>  
> @@ -1099,33 +1096,24 @@ export MODORDER := $(extmod_prefix)modules.order
>  export MODULES_NSDEPS := $(extmod_prefix)modules.nsdeps
>  
>  ifeq ($(KBUILD_EXTMOD),)
> -core-y			+= kernel/ certs/ mm/ fs/ ipc/ security/ crypto/
> -core-$(CONFIG_BLOCK)	+= block/
> -core-$(CONFIG_IO_URING)	+= io_uring/
>  
> -vmlinux-dirs	:= $(patsubst %/,%,$(filter %/, \
> -		     $(core-y) $(core-m) $(drivers-y) $(drivers-m) \
> -		     $(libs-y) $(libs-m)))
> -
> -vmlinux-alldirs	:= $(sort $(vmlinux-dirs) Documentation . \
> +build-dir	:= .
> +clean-dirs	:= $(sort . Documentation \
>  		     $(patsubst %/,%,$(filter %/, $(core-) \
>  			$(drivers-) $(libs-))))
>  
> -build-dirs	:= $(vmlinux-dirs)
> -clean-dirs	:= $(vmlinux-alldirs)
> -
> -subdir-modorder := $(addsuffix /modules.order, $(build-dirs))
> -
> +export ARCH_CORE	:= $(core-y)
> +export ARCH_LIB		:= $(filter %/, $(libs-y))
> +export ARCH_DRIVERS	:= $(drivers-y) $(drivers-m)
>  # Externally visible symbols (used by link-vmlinux.sh)
> -KBUILD_VMLINUX_OBJS := $(head-y) $(patsubst %/,%/built-in.a, $(core-y))
> -KBUILD_VMLINUX_OBJS += $(addsuffix built-in.a, $(filter %/, $(libs-y)))
> +
> +KBUILD_VMLINUX_OBJS := $(head-y) ./built-in.a
>  ifdef CONFIG_MODULES
>  KBUILD_VMLINUX_OBJS += $(patsubst %/, %/lib.a, $(filter %/, $(libs-y)))
>  KBUILD_VMLINUX_LIBS := $(filter-out %/, $(libs-y))
>  else
>  KBUILD_VMLINUX_LIBS := $(patsubst %/,%/lib.a, $(libs-y))
>  endif
> -KBUILD_VMLINUX_OBJS += $(patsubst %/,%/built-in.a, $(drivers-y))
>  
>  export KBUILD_VMLINUX_OBJS KBUILD_VMLINUX_LIBS
>  export KBUILD_LDS          := arch/$(SRCARCH)/kernel/vmlinux.lds
> @@ -1140,7 +1128,7 @@ ifdef CONFIG_TRIM_UNUSED_KSYMS
>  # (this can be evaluated only once include/config/auto.conf has been included)
>  KBUILD_MODULES := 1
>  
> -autoksyms_recursive: descend modules.order
> +autoksyms_recursive: $(build-dir) modules.order
>  	$(Q)$(CONFIG_SHELL) $(srctree)/scripts/adjust_autoksyms.sh \
>  	  "$(MAKE) -f $(srctree)/Makefile autoksyms_recursive"
>  endif
> @@ -1168,7 +1156,7 @@ targets := vmlinux
>  
>  # The actual objects are generated when descending,
>  # make sure no implicit rule kicks in
> -$(sort $(vmlinux-deps) $(subdir-modorder)): descend ;
> +$(sort $(vmlinux-deps)): $(build-dir) ;
>  
>  filechk_kernel.release = \
>  	echo "$(KERNELVERSION)$$($(CONFIG_SHELL) $(srctree)/scripts/setlocalversion $(srctree))"
> @@ -1439,13 +1427,6 @@ endif
>  
>  modules: $(if $(KBUILD_BUILTIN),vmlinux) modules_prepare
>  
> -cmd_modules_order = cat $(real-prereqs) > $@
> -
> -modules.order: $(subdir-modorder) FORCE
> -	$(call if_changed,modules_order)
> -
> -targets += modules.order
> -
>  # Target to prepare building external modules
>  modules_prepare: prepare
>  	$(Q)$(MAKE) $(build)=scripts scripts/module.lds
> @@ -1716,9 +1697,7 @@ else # KBUILD_EXTMOD
>  KBUILD_BUILTIN :=
>  KBUILD_MODULES := 1
>  
> -build-dirs := $(KBUILD_EXTMOD)
> -$(MODORDER): descend
> -	@:
> +build-dir := $(KBUILD_EXTMOD)
>  
>  compile_commands.json: $(extmod_prefix)compile_commands.json
>  PHONY += compile_commands.json
> @@ -1756,6 +1735,9 @@ PHONY += modules modules_install modules_prepare
>  
>  ifdef CONFIG_MODULES
>  
> +$(MODORDER): $(build-dir)
> +	@:
> +
>  modules: modules_check
>  	$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modpost
>  
> @@ -1809,7 +1791,7 @@ single-no-ko := $(filter-out $(single-ko), $(MAKECMDGOALS)) \
>  
>  $(single-ko): single_modpost
>  	@:
> -$(single-no-ko): descend
> +$(single-no-ko): $(build-dir)
>  	@:
>  
>  # Remove MODORDER when done because it is not the real one.
> @@ -1819,24 +1801,17 @@ single_modpost: $(single-no-ko) modules_prepare
>  	$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modpost
>  	$(Q)rm -f $(MODORDER)
>  
> -single-goals := $(addprefix $(extmod_prefix), $(single-no-ko))
> -
> -# trim unrelated directories
> -build-dirs := $(foreach d, $(build-dirs), \
> -			$(if $(filter $d/%, $(single-goals)), $d))
> +single-goals := $(addprefix $(build-dir)/, $(single-no-ko))
>  
>  endif
>  
> -# Handle descending into subdirectories listed in $(build-dirs)
>  # Preset locale variables to speed up the build process. Limit locale
>  # tweaks to this spot to avoid wrong language settings when running
>  # make menuconfig etc.
>  # Error messages still appears in the original language
> -PHONY += descend $(build-dirs)
> -descend: $(build-dirs)
> -$(build-dirs): prepare
> -	$(Q)$(MAKE) $(build)=$@ need-builtin=1 need-modorder=1 \
> -	$(filter $@/%, $(single-goals))
> +PHONY += $(build-dir)
> +$(build-dir): prepare
> +	$(Q)$(MAKE) $(build)=$@ need-builtin=1 need-modorder=1 $(single-goals)
>  
>  clean-dirs := $(addprefix _clean_, $(clean-dirs))
>  PHONY += $(clean-dirs) clean
> diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
> index 3fb6a99e78c4..140dcc3c57bd 100644
> --- a/scripts/Makefile.lib
> +++ b/scripts/Makefile.lib
> @@ -89,6 +89,7 @@ always-y			+= $(dtb-y)
>  
>  # Add subdir path
>  
> +ifneq ($(obj),.)
>  extra-y		:= $(addprefix $(obj)/,$(extra-y))
>  always-y	:= $(addprefix $(obj)/,$(always-y))
>  targets		:= $(addprefix $(obj)/,$(targets))
> @@ -100,6 +101,7 @@ multi-obj-m	:= $(addprefix $(obj)/, $(multi-obj-m))
>  multi-dtb-y	:= $(addprefix $(obj)/, $(multi-dtb-y))
>  real-dtb-y	:= $(addprefix $(obj)/, $(real-dtb-y))
>  subdir-ym	:= $(addprefix $(obj)/,$(subdir-ym))
> +endif
>  
>  # Finds the multi-part object the current object will be linked into.
>  # If the object belongs to two or more multi-part objects, list them all.
> -- 
> 2.34.1

-- 
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