Re: [PATCH v4 2/7] kbuild: add "make tools_build" to build userspace tools from tools/

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential
issue to consider:
- [Low] kbuild: USERLDFLAGS in LDFLAGS is ignored when building
  tools/dma
--

commit d48c343f29bb15ff9a8fc256221e365cbc49ffb2
Author: Sasha Levin <sashal@kernel.org>

kbuild: add "make tools_build" to build userspace tools from tools/

This commit adds a CONFIG_TOOLS_BUILD menu and a tools_build make target
to build selected userspace programs under tools/ into tools-build/ in
the object tree.

> diff --git a/tools/Makefile.kbuild b/tools/Makefile.kbuild
> new file mode 100644
> index 0000000000000..7a26e7c3d5769
> --- /dev/null
> +++ b/tools/Makefile.kbuild

[ ... ]

> +# The compiler CONFIG_CC_CAN_LINK was tested with. The tools take linker
> +# flags from LDFLAGS.
> +tools-cc := $(CC) $(USERCFLAGS) $(KBUILD_USERABI)
> +ifneq ($(USERLDFLAGS),)
> +override LDFLAGS := $(USERLDFLAGS)
> +export LDFLAGS
> +endif

[ ... ]

> +tools-$(CONFIG_TOOLS_BUILD_DMA)		+= dma

[Severity: Low]
Does building tools/dma drop USERLDFLAGS?

tools/Makefile.kbuild passes USERLDFLAGS only through LDFLAGS, but
tools/dma/Makefile compiles and links dma_map_benchmark in one step
without referencing $(LDFLAGS):

tools/dma/Makefile:
	$(OUTPUT)$(DMA_MAP_BENCHMARK): prepare FORCE
		$(CC) $(CFLAGS) $(DMA_MAP_BENCHMARK).c -o $@

When USERLDFLAGS is needed to link target userspace binaries (such as
--sysroot or -fuse-ld=lld validated by CONFIG_CC_CAN_LINK), building
tools/dma with CONFIG_TOOLS_BUILD_DMA=y will ignore those flags and can
fail to link.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261112195427.3411746-1-sashal@kernel.org?part=2