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

[James Clark <james.clark@linaro.org>]

On 15/05/2026 11:58 pm, Ihor Solodrai wrote:
> On 5/14/26 2:32 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 accepts either a full path or "ld.lld-15" style inputs to
>> -fuse-ld= so this will work with LLD defined the same way as the other
>> LLVM tools. However, for full paths, we need to use ".../ld.lld" instead
>> of the generic driver "lld", but I don't think the original use of "lld"
>> was significant as this is always a linux build.
>>
>> Signed-off-by: James Clark <james.clark@linaro.org>
>> ---
>>   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..44ba829e5d4d 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 \
> 
> Hi James,
> 
> This patch breaks the selftests/bpf build:
> 
> $ clang --version
> clang version 22.1.3 (CentOS 22.1.3-1.el9)
> Target: x86_64-redhat-linux-gnu
> Thread model: posix
> InstalledDir: /usr/bin
> Configuration file: /etc/clang/x86_64-redhat-linux-gnu-clang.cfg
> 
> $ make LLVM=1 -j$(nproc)
>    [...] # ok
> 
> $ make LLVM=1 -C tools/testing/selftests/bpf -j$(nproc)
> 
> [...] # somewhere in the middle
> 
>    LIB      liburandom_read.so
> clang: error: invalid linker name in argument '-fuse-ld=ld.lld'
> make: *** [Makefile:256: /home/isolodrai/workspace/review/linux/tools/testing/selftests/bpf/liburandom_read.so] Error 1
> make: Leaving directory '/home/isolodrai/workspace/review/linux/tools/testing/selftests/bpf'
> 
> [...]
> 
> Or a simpler reproducer:
> 
> $ make LLVM=1 OUTPUT=/tmp/out /tmp/out/liburandom_read.so
>    LIB      liburandom_read.so
> clang: error: invalid linker name in argument '-fuse-ld=ld.lld'
> make: *** [Makefile:256: /tmp/out/liburandom_read.so] Error 1
> 
> $ make LLVM=-22 OUTPUT=/tmp/out /tmp/out/liburandom_read.so
>    LIB      liburandom_read.so
> clang-22: error: invalid linker name in argument '-fuse-ld=ld.lld-22'
> make: *** [Makefile:256: /tmp/out/liburandom_read.so] Error 1
> 
> I tried your patches, and only then noticed BPF CI caught this too:
> https://github.com/kernel-patches/bpf/actions/runs/25943477658/job/76267174885?pr=12082
> 

Thanks for testing. Yeah looks like I made a mistake here testing the 
various different formats of LLD. Converting it to a full path works 
with both prefixed and postfixed versions, and that's what's already 
done for non x86/riscv so I'll do that.

>>   		     -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
>>
>