Re: [PATCH bpf-next v2] bpftool: Allow explicitly skip llvm, libbfd and libcrypto dependencies

[Quentin Monnet <qmo@kernel.org>]

2026-03-17 10:29 UTC+0000 ~ Quentin Monnet <qmo@kernel.org>
> 2026-03-12 17:03 UTC-0700 ~ Mykyta Yatsenko <mykyta.yatsenko5@gmail.com>
>> From: Mykyta Yatsenko <yatsenko@meta.com>
>>
>> Introduce SKIP_LLVM, SKIP_LIBBFD, and SKIP_CRYPTO build flags that let
>> users build bpftool without these optional dependencies.
>>
>> SKIP_LLVM=1 skips LLVM even when detected. SKIP_LIBBFD=1 prevents the
>> libbfd JIT disassembly fallback when LLVM is absent. Together, they
>> produce a bpftool with no disassembly support.
>>
>> SKIP_CRYPTO=1 excludes sign.c and removes the -lcrypto link dependency.
>> Inline stubs in main.h return errors with a clear message if signing
>> functions are called at runtime.
>>
>> Use BPFTOOL_WITHOUT_CRYPTO (not HAVE_LIBCRYPTO_SUPPORT) as the C
>> define, following the BPFTOOL_WITHOUT_SKELETONS naming convention for
>> bpftool-internal build config, leaving HAVE_LIBCRYPTO_SUPPORT free for
>> proper feature detection in the future.
>>
>> All three flags are propagated through the selftests Makefile to bpftool
>> sub-builds.
>>
>> Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
> 
> 
> Sorry I'm late for this one, I see Andrii applied it - I just wanted to
> say thank you for this!


Mykyta, Andrii,

Apologies again for missing the review on this series. I'm realising
only now that it goes beyond what we initially discussed: It adds a way
to turn off the optional dependencies related to the disassemblers,
which is what we agreed on, but it also makes libcrypto optional.

There were previous discussions where I pushed back against making
program signing optional in bpftool. It's one thing to have the JIT
disassembler unavailable on a machine; but it's going to be a pain if a
policy requires signed programs on a system, but the bpftool version
available does not support signing. Are you really sure you want to make
it optional? My preference would be to keep program signing a mandatory
feature for bpftool going forward.

Best regards,
Quentin