Re: [XEN PATCH v8 12/47] build: build everything from the root dir, use obj=$subdir

[Jan Beulich <jbeulich@xxxxxxxx>]

On 25.11.2021 14:39, Anthony PERARD wrote:
> A subdirectory is now built by setting "$(obj)" instead of changing
> directory. "$(obj)" should always be set when using "Rules.mk" and
> thus a shortcut "$(build)" is introduced and should be used.
> 
> A new variable "$(need-builtin)" is introduce. It is to be used
> whenever a "built_in.o" is wanted from a subdirectory. "built_in.o"
> isn't the main target anymore, and thus only needs to depends on the
> objects that should be part of "built_in.o".
> 
> Introduce $(srctree) and $(objtree) to replace $(BASEDIR) in cases a
> relative path is better, and $(abs_srctree) and $(abs_objtree) which
> have an absolute path.
> 
> DEPS is updated as the existing macro to deal with it doesn't know
> about $(obj).
> 
> There's some changes in "Rules.mk" which in addition to deal with
> "$(obj)" also make it's looks more like "Makefile.build" from Linux
> v5.12.
> 
> test/Makefile doesn't need special handling in order to build
> everything under test/, Rules.mk will visit test/livepatch via
> $(subdir-y), thus "tests" "all" and "build" target are removed.
> "subtree-force-update" target isn't useful so it is removed as well.
> 
> test/livepatch/Makefile doesn't need default target anymore, Rules.mk
> will build everything in $(extra-y) and thus all *.livepatch.
> 
> Adjust cloc recipe: dependency files generated by CC will now have the
> full path to the source file, so we don't need to prepend the
> subdirectory. This fix some issue with source not been parsed by cloc
> before. Also source from tools/kconfig would be listed with changes in
> this patch so adjust the find command to stop listing the "tools"
> directory and thus kconfig. With a default build of Xen on X86, they
> are a few new files parsed by cloc:
>     arch/x86/x86_64/compat/mm.c
>     arch/x86/x86_64/mm.c
>     common/compat/domain.c
>     common/compat/memory.c
>     common/compat/xlat.c
> 
> Signed-off-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
> Acked-by: Bob Eshleman <bobbyeshleman@xxxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
with one nit and a remark:

> --- a/xen/Makefile
> +++ b/xen/Makefile
> @@ -22,6 +22,15 @@ export CHECKPOLICY ?= checkpolicy
>  export BASEDIR := $(CURDIR)
>  export XEN_ROOT := $(BASEDIR)/..
>  
> +abs_objtree := $(CURDIR)
> +abs_srctree := $(CURDIR)

Nit: In line with e.g. obj-y I think these would better be abs-srctree and
abs-objtree.

> --- a/xen/arch/x86/Makefile
> +++ b/xen/arch/x86/Makefile
> @@ -80,6 +80,9 @@ endif
>  extra-y += asm-macros.i
>  extra-y += xen.lds
>  
> +# Allows usercopy.c to include itself
> +$(obj)/usercopy.o: CFLAGS-y += -iquote .
> +
>  ifneq ($(CONFIG_HVM),y)
>  $(obj)/x86_emulate.o: CFLAGS-y += -Wno-unused-label
>  endif
> @@ -129,13 +132,13 @@ $(TARGET)-syms: $(BASEDIR)/prelink.o $(obj)/xen.lds
>       $(NM) -pa --format=sysv $(@D)/.$(@F).0 \
>               | $(BASEDIR)/tools/symbols $(all_symbols) --sysv --sort \
>               >$(@D)/.$(@F).0.S
> -     $(MAKE) -f $(BASEDIR)/Rules.mk efi-y= $(@D)/.$(@F).0.o
> +     $(MAKE) $(build)=$(@D) efi-y= $(@D)/.$(@F).0.o

Hmm, hasn't the efi-y= become unnecessary already by patch 6?

Jan