On 5/18/26 2:03 AM, James Clark wrote:
> Building with LLVM=... could result in a different version of lld being
> used than the main toolchain for liburandom_read.so because it's
> hardcoded to "lld" in this makefile.
>
> Make it consistent with the rest of the LLVM toolchain by adding an LLD
> variable to Makefile.include. Keep the fallback for other architectures
> in tools/testing/selftests/bpf/Makefile as it seems like it's something
> specific to this make rule and shouldn't be global.
>
> Clang only accepts either a full path to "/x/x/ld.lld" or "lld-15" style
> inputs to "-fuse-ld=", so the only way to make it work with both
> prefixed and postfixed paths is to always take the full path. Also I
> don't think the original use of "lld" over "ld.lld" was significant as
> this is always a linux build, so that can be changed to make it work in
> both cases.
>
> Signed-off-by: James Clark <[email protected]>
> ---
> tools/scripts/Makefile.include | 2 ++
> tools/testing/selftests/bpf/Makefile | 8 ++++----
> 2 files changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/tools/scripts/Makefile.include b/tools/scripts/Makefile.include
> index 380ad84ac51e..5c2d505cba62 100644
> --- a/tools/scripts/Makefile.include
> +++ b/tools/scripts/Makefile.include
> @@ -67,6 +67,7 @@ ifneq ($(LLVM),)
> $(call allow-override,HOSTAR,$(LLVM_PREFIX)llvm-ar$(LLVM_SUFFIX))
> $(call allow-override,LD,$(LLVM_PREFIX)ld.lld$(LLVM_SUFFIX))
> $(call allow-override,HOSTLD,$(LLVM_PREFIX)ld.lld$(LLVM_SUFFIX))
> + $(call allow-override,LLD,$(LLVM_PREFIX)ld.lld$(LLVM_SUFFIX))
> $(call allow-override,CXX,$(LLVM_PREFIX)clang++$(LLVM_SUFFIX))
> $(call allow-override,STRIP,$(LLVM_PREFIX)llvm-strip$(LLVM_SUFFIX))
> $(call allow-override,LLVM_STRIP,$(LLVM_PREFIX)llvm-strip$(LLVM_SUFFIX))
> @@ -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)
> $(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 6ef6872adbc3..836e783f0170 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 := $(shell command -v $(LLD))
> else
> -LLD := $(shell command -v $(LD))
> +USE_LD := $(shell command -v $(LD))
Can confirm v2 fixes the v1 breakage I reported.
One nit on the empty USE_LD case the bot raised. It isn't actually a
build failure: if command -v finds nothing, USE_LD is empty and clang
gets a bare "-fuse-ld=".
Since it's unintentional, how about we just add a check to ensure the
linker was found?
Something like:
$(Q)test -n "$(USE_LD)" || { \
echo "$@: linker '$(LINKER)' not found - add it to PATH, or pass \
LLVM=/path/ or LLD=/abs/ld.lld" >&2; exit 1; }
> 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 \
> -Wl,--version-script=liburandom_read.map \
> -fPIC -shared -o $@
>
> @@ -268,7 +268,7 @@ $(OUTPUT)/urandom_read: urandom_read.c urandom_read_aux.c
> $(OUTPUT)/liburandom_r
> $(filter-out -static,$(CFLAGS) $(LDFLAGS)) $(filter
> %.c,$^) \
> -Wno-unused-command-line-argument \
> -lurandom_read $(filter-out -static,$(LDLIBS)) -L$(OUTPUT)
> \
> - -fuse-ld=$(LLD) -Wl,-znoseparate-code -Wl,--build-id=sha1 \
> + -fuse-ld=$(USE_LD) -Wl,-znoseparate-code
> -Wl,--build-id=sha1 \
> -Wl,-rpath=. -o $@
>
> $(OUTPUT)/sign-file: ../../../../scripts/sign-file.c
>
