Re: [PATCH 5/6] tools/build: selftests: Allow versioning LLVM lld

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] Using `-fuse-ld=ld.lld` breaks compilation of BPF selftests with GCC.
--

commit 18e1876d18fad631b521da817483ba47293a9020
Author: James Clark <james.clark@linaro.org>

tools/build: selftests: Allow versioning LLVM lld

This commit updates Makefile.include to add an LLD variable, matching the
rest of the LLVM toolchain. It modifies the BPF selftests Makefile to use
this new LLD variable instead of hardcoding lld.

> diff --git a/tools/scripts/Makefile.include b/tools/scripts/Makefile.include
> index 380ad84ac51e6..5c2d505cba62b 100644
> --- a/tools/scripts/Makefile.include
> +++ b/tools/scripts/Makefile.include
[ ... ]
> @@ -91,6 +92,7 @@ else
>    # Some tools still require Clang, LLC and/or LLVM utils
>    $(call allow-override,CLANG,clang)
>    $(call allow-override,LLC,llc)
> +  $(call allow-override,LLD,ld.lld)

Could setting LLD to ld.lld when not using LLVM cause issues for BPF
selftests compilation with GCC?

>    $(call allow-override,LLVM_CONFIG,llvm-config)
>    $(call allow-override,LLVM_OBJCOPY,llvm-objcopy)
>    $(call allow-override,LLVM_STRIP,llvm-strip)
> diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
> index 6ef6872adbc3e..44ba829e5d4dd 100644
> --- a/tools/testing/selftests/bpf/Makefile
> +++ b/tools/testing/selftests/bpf/Makefile
> @@ -245,9 +245,9 @@ $(OUTPUT)/%:%.c
>  
>  # LLVM's ld.lld doesn't support all the architectures, so use it only on x86
>  ifeq ($(SRCARCH),$(filter $(SRCARCH),x86 riscv))
> -LLD := lld
> +USE_LD := $(LLD)
>  else
> -LLD := $(shell command -v $(LD))
> +USE_LD := $(shell command -v $(LD))
>  endif
>  
>  # Filter out -static for liburandom_read.so and its dependent targets so that static builds
> @@ -258,7 +258,7 @@ $(OUTPUT)/liburandom_read.so: urandom_read_lib1.c urandom_read_lib2.c liburandom
>  		     $(filter-out -static,$(CFLAGS) $(LDFLAGS)) \
>  		     $(filter %.c,$^) $(filter-out -static,$(LDLIBS)) \
>  		     -Wno-unused-command-line-argument \
> -		     -fuse-ld=$(LLD) -Wl,-znoseparate-code -Wl,--build-id=sha1 \
> +		     -fuse-ld=$(USE_LD) -Wl,-znoseparate-code -Wl,--build-id=sha1 \

When LLVM=1 is not set, CC defaults to gcc. The Makefile uses
$(CC) ... -fuse-ld=$(USE_LD) to link liburandom_read.so.

Because USE_LD evaluates to ld.lld, gcc receives -fuse-ld=ld.lld.

However, GCC's command-line option parser is strictly hardcoded to accept
only specific linker names (lld, bfd, gold, mold). It does not recognize
-fuse-ld=ld.lld or absolute paths, and fails with an error like:

gcc: error: unrecognized command-line option '-fuse-ld=ld.lld'; did you mean '-fuse-ld=lld'?

Does this regression break the default GCC build of BPF selftests on x86
and riscv architectures?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260514-james-perf-llvm-version-v1-0-6cac1a9a4c8d@linaro.org?part=5