Re: [RFC PATCH 1/1] scripts: Build per module Rust crates

From: Masahiro Yamada
Date: Sun Oct 22 2023 - 12:22:41 EST

On Sat, Oct 7, 2023 at 12:57 AM Martin Rodriguez Reboredo
<yakoyoku@xxxxxxxxx> wrote:
>
> Enables compiling Rust crates as dependencies of kernel modules.
>
> When a composite object depends on an `.rlib` file, which by the way is
> a current ar archive, Kbuild will compile it from its base Rust source
> and link it.
>
> This makes possible to have Rust bindings for a subsystem that is
> compiled as a module.
>
> Signed-off-by: Martin Rodriguez Reboredo <yakoyoku@xxxxxxxxx>


I could not understand how this will work because
there is no explanation how to use *.rlib in the later
build steps.

If I understand correctly, does this intend to link *.rlib
as a part of modules?

In C, there was a discussion about
"that would be nice to be able to link static libraries",
but we do not do it any more. [1]

Following that discussion, linking libraries does not
seem what we want to do.


[1]: https://lore.kernel.org/lkml/20200106032324.3147-1-masahiroy@xxxxxxxxxx/




> ---
> Makefile | 4 ++--
> scripts/Makefile.build | 10 +++++++++-
> scripts/Makefile.lib | 19 +++++++++++++------
> 3 files changed, 24 insertions(+), 9 deletions(-)
>
> diff --git a/Makefile b/Makefile
> index 7d6be12e4c3e..7774c97e8aa0 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -283,7 +283,7 @@ no-compiler-targets := $(no-dot-config-targets) install dtbs_install \
> headers_install modules_install modules_sign kernelrelease image_name
> no-sync-config-targets := $(no-dot-config-targets) %install modules_sign kernelrelease \
> image_name
> -single-targets := %.a %.i %.ko %.lds %.ll %.lst %.mod %.o %.rsi %.s %.symtypes %/
> +single-targets := %.a %.i %.ko %.lds %.ll %.lst %.mod %.o %.rlib %.rsi %.s %.symtypes %/
>
> config-build :=
> mixed-build :=
> @@ -1919,7 +1919,7 @@ $(clean-dirs):
> clean: $(clean-dirs)
> $(call cmd,rmfiles)
> @find $(or $(KBUILD_EXTMOD), .) $(RCS_FIND_IGNORE) \
> - \( -name '*.[aios]' -o -name '*.rsi' -o -name '*.ko' -o -name '.*.cmd' \
> + \( -name '*.[aios]' -o -name '*.rlib' -o -name '*.rsi' -o -name '*.ko' -o -name '.*.cmd' \
> -o -name '*.ko.*' \
> -o -name '*.dtb' -o -name '*.dtbo' \
> -o -name '*.dtb.S' -o -name '*.dtbo.S' \
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index da37bfa97211..627010518b27 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -246,7 +246,9 @@ $(obj)/%.o: $(src)/%.c $(recordmcount_source) FORCE
> # To make this rule robust against "Argument list too long" error,
> # ensure to add $(obj)/ prefix by a shell command.
> cmd_mod = printf '%s\n' $(call real-search, $*.o, .o, -objs -y -m) | \
> - $(AWK) '!x[$$0]++ { print("$(obj)/"$$0) }' > $@
> + $(AWK) '!x[$$0]++ { print("$(obj)/"$$0) }' > $@ && \
> + printf '%s\n' $(call real-search, $*.rlib, .rlib, -objs -y -m) | \
> + $(AWK) '!x[$$0]++ { print("--library=$(obj)/"$$0) }' >> $@
>
> $(obj)/%.mod: FORCE
> $(call if_changed,mod)
> @@ -291,6 +293,12 @@ quiet_cmd_rustc_o_rs = $(RUSTC_OR_CLIPPY_QUIET) $(quiet_modtag) $@
> $(obj)/%.o: $(src)/%.rs FORCE
> $(call if_changed_dep,rustc_o_rs)
>
> +quiet_cmd_rustc_rlib_rs = $(RUSTC_OR_CLIPPY_QUIET) $(quiet_modtag) $@
> + cmd_rustc_rlib_rs = $(rust_common_cmd) -Ccodegen-units=1 --emit=link=$@ $<
> +
> +$(obj)/%.rlib: $(src)/%.rs FORCE
> + $(call if_changed_dep,rustc_rlib_rs)
> +
> quiet_cmd_rustc_rsi_rs = $(RUSTC_OR_CLIPPY_QUIET) $(quiet_modtag) $@
> cmd_rustc_rsi_rs = \
> $(rust_common_cmd) -Zunpretty=expanded $< >$@; \
> diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
> index 68d0134bdbf9..6e8cfbad015d 100644
> --- a/scripts/Makefile.lib
> +++ b/scripts/Makefile.lib
> @@ -53,14 +53,18 @@ multi-search = $(sort $(foreach m, $1, $(if $(call suffix-search, $m, $2, $3 -),
> real-search = $(foreach m, $1, $(if $(call suffix-search, $m, $2, $3 -), $(call suffix-search, $m, $2, $3), $m))
>
> # If $(foo-objs), $(foo-y), $(foo-m), or $(foo-) exists, foo.o is a composite object
> -multi-obj-y := $(call multi-search, $(obj-y), .o, -objs -y)
> -multi-obj-m := $(call multi-search, $(obj-m), .o, -objs -y -m)
> +multi-obj-y := $(call multi-search, $(obj-y), .o, -objs -y) \
> + $(call multi-search, $(obj-y), .rlib, -objs -y)
> +multi-obj-m := $(call multi-search, $(obj-m), .o, -objs -y -m) \
> + $(call multi-search, $(obj-m), .rlib, -objs -y -m)
> multi-obj-ym := $(multi-obj-y) $(multi-obj-m)
>
> # Replace multi-part objects by their individual parts,
> # including built-in.a from subdirectories
> -real-obj-y := $(call real-search, $(obj-y), .o, -objs -y)
> -real-obj-m := $(call real-search, $(obj-m), .o, -objs -y -m)
> +real-obj-y := $(call real-search, $(obj-y), .o, -objs -y) \
> + $(call real-search, $(obj-y), .rlib, -objs -y)
> +real-obj-m := $(call real-search, $(obj-m), .o, -objs -y -m) \
> + $(call real-search, $(obj-m), .rlib, -objs -y -m)
>
> always-y += $(always-m)
>
> @@ -107,7 +111,8 @@ 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.
> modname-multi = $(sort $(foreach m,$(multi-obj-ym),\
> - $(if $(filter $*.o, $(call suffix-search, $m, .o, -objs -y -m)),$(m:.o=))))
> + $(if $(filter $*.o, $(call suffix-search, $m, .o, -objs -y -m)),$(m:.o=)) \
> + $(if $(filter $*.rlib, $(call suffix-search, $m, .rlib, -objs -y -m)),$(m:.rlib=))))
>
> __modname = $(or $(modname-multi),$(basetarget))
>
> @@ -210,7 +215,9 @@ _cpp_flags += -I $(srctree)/$(src) -I $(objtree)/$(obj)
> endif
> endif
>
> -part-of-module = $(if $(filter $(basename $@).o, $(real-obj-m)),y)
> +part-of-module = \
> + $(if $(or $(filter $(basename $@).o, $(real-obj-m)), \
> + $(filter $(basename $@).rlib, $(real-obj-m))),y)
> quiet_modtag = $(if $(part-of-module),[M], )
>
> modkern_cflags = \
> --
> 2.42.0
>


--
Best Regards
Masahiro Yamada