On 2/3/21 12:12 PM, Andrii Nakryiko wrote:
> On Wed, Feb 3, 2021 at 12:09 PM Randy Dunlap <rdunlap@xxxxxxxxxxxxx> wrote:
>>
>> On 2/3/21 11:39 AM, Andrii Nakryiko wrote:
>>> On Wed, Feb 3, 2021 at 9:22 AM Randy Dunlap <rdunlap@xxxxxxxxxxxxx> wrote:
>>>>
>>>> On 2/3/21 2:57 AM, Toke Høiland-Jørgensen wrote:
>>>>> Randy Dunlap <rdunlap@xxxxxxxxxxxxx> writes:
>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> I see this sometimes when building a kernel: (on x86_64,
>>>>>> with today's linux-next 20210202):
>>>>>>
>>>>>>
>>>>>> CONFIG_CGROUP_BPF=y
>>>>>> CONFIG_BPF=y
>>>>>> CONFIG_BPF_SYSCALL=y
>>>>>> CONFIG_ARCH_WANT_DEFAULT_BPF_JIT=y
>>>>>> CONFIG_BPF_PRELOAD=y
>>>>>> CONFIG_BPF_PRELOAD_UMD=m
>>>>>> CONFIG_HAVE_EBPF_JIT=y
>>>>>>
>>>>>>
>>>>>> Auto-detecting system features:
>>>>>> ... libelf: [ [31mOFF[m ]
>>>>>> ... zlib: [ [31mOFF[m ]
>>>>>> ... bpf: [ [31mOFF[m ]
>>>>>>
>>>>>> No libelf found
>>>>>> make[5]: [Makefile:287: elfdep] Error 1 (ignored)
>>>>>> No zlib found
>>>>>> make[5]: [Makefile:290: zdep] Error 1 (ignored)
>>>>>> BPF API too old
>>>>>> make[5]: [Makefile:293: bpfdep] Error 1 (ignored)
>>>>>>
>>>>>>
>>>>>> but pkg-config tells me:
>>>>>>
>>>>>> $ pkg-config --modversion libelf
>>>>>> 0.168
>>>>>> $ pkg-config --libs libelf
>>>>>> -lelf
>>>>>>
>>>>>>
>>>>>> Any ideas?
>>>>>
>>>>> This usually happens because there's a stale cache of the feature
>>>>> detection tests lying around somewhere. Look for a 'feature' directory
>>>>> in whatever subdir you got that error. Just removing the feature
>>>>> directory usually fixes this; I've fixed a couple of places where this
>>>>> is not picked up by 'make clean' (see, e.g., 9d9aae53b96d ("bpf/preload:
>>>>> Make sure Makefile cleans up after itself, and add .gitignore")) but I
>>>>> wouldn't be surprised if there are still some that are broken.
>>>>
>>>> Hi,
>>>>
>>>> Thanks for replying.
>>>>
>>>> I removed the feature subdir and still got this build error, so I
>>>> removed everything in BUILDDIR/kernel/bpf/preload and rebuilt --
>>>> and still got the same libelf build error.
>>>
>>> I hate the complexity of feature detection framework to the point that
>>> I'm willing to rip it out from libbpf's Makefile completely. I just
>>> spent an hour trying to understand what's going on in a very similar
>>> situation. Extremely frustrating.
>>>
>>> In your case, it might be feature detection triggered from
>>> resolve_btfids, so try removing
>>> $(OUTPUT)/tools/bpf/resolve_btfids/{feature/,FEATURE-DUMP.libbpf}.
>>>
>>> It seems like we don't do proper cleanup in resolve_btfids (it should
>>> probably call libbpf's clean as well). And it's beyond me why `make -C
>>> tools/build/feature clean` doesn't clean up FEATURE-DUMP.<use-case>
>>> file as well.
>>
>>
>> I don't think it's related to improper cleanup or old files/dirs
>> laying around. I say that because I did a full build in a new output dir.
>> and it still failed in the same way.
>
> If you cd tools/lib/bpf and run make there, does it detect those libraries?
Yes:
Auto-detecting system features:
... libelf: [ on ]
... zlib: [ on ]
... bpf: [ on ]
--
~Randy
