[llvm-dev] BPF: How can I enable BPF support in my LLVM toolchain?

[Tom Stellard via llvm-dev]

On 1/11/21 9:27 AM, Sedat Dilek wrote:
> On Mon, Jan 11, 2021 at 6:14 PM Tom Stellard <tstellar at redhat.com> wrote:
>>
>> On 1/11/21 9:11 AM, Sedat Dilek wrote:
>>> On Mon, Jan 11, 2021 at 4:35 PM Tom Stellard <tstellar at redhat.com> wrote:
>>>>
>>>> On 1/11/21 5:35 AM, Sedat Dilek via llvm-dev wrote:
>>>>> Hi,
>>>>>
>>>>> when building a Linux-kernel with CONFIG_DEBUG_INFO_BTF=y my build breaks.
>>>>>
>>>>
>>>> I commented on the GitHub issue about the root cause of this.
>>>>
>>>>> This is because my selfmade LLVM toolchain v11.0.1 has no BPF support:
>>>>>
>>>>> $ llc --version
>>>>> LLVM (http://llvm.org/):
>>>>>     LLVM version 11.0.1
>>>>>     Optimized build.
>>>>>     Default target: x86_64-unknown-linux-gnu
>>>>>     Host CPU: sandybridge
>>>>>
>>>>>     Registered Targets:
>>>>>       x86    - 32-bit X86: Pentium-Pro and above
>>>>>       x86-64 - 64-bit X86: EM64T and AMD64
>>>>>
>>>>> What system or binary requirements do I need and which CMAKE option(s)
>>>>> need(s) to be set?
>>>>
>>>> The LLVM_TARGETS_TO_BUILD CMake option controls which targets to build.
>>>>
>>>
>>> tc-build folks fixed that up.
>>> See commit "build-llvm.py: Enable BPF backend by default".
>>>
>>> Is there a BPF test-suite - like for clang and lld?
>>>
>>
>> There's one in the kernel.
>>
> 
> Can I run it before compiling a single-line of a Linux-kernel?
> Does it test for BTF stuff?

I don't know the answers to these questions.

> How do I run it?
> 

You can run it with:
make -C tools/testing/selftests/bpf

-Tom


> - Sedat -
> 
>> -Tom
>>
>>> I have build pahole from Git - now building a new Linux kernel.
>>>
>>> $ cd /path/to/pahole/git
>>> $ git describe
>>> v1.19-7-gb688e3597060
>>>
>>> Will report later.
>>>
>>> Regards,
>>> - Sedat -
>>>
>>> [1] https://github.com/ClangBuiltLinux/tc-build/commit/e796c046428a971404eec008c841f9dd7c1621e8
>>>
>>>> -Tom
>>>>
>>>>> I hope this is not hardware-dependent (here: Intel SandyBridge).
>>>>>
>>>>> Thanks in advance.
>>>>>
>>>>> Regards,
>>>>> - Sedat -
>>>>>
>>>>> [1] https://github.com/ClangBuiltLinux/tc-build/issues/129
>>>>> _______________________________________________
>>>>> LLVM Developers mailing list
>>>>> llvm-dev at lists.llvm.org
>>>>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>>>
>>>>
>>>
>>
>