On 2/3/21 12:33 PM, Andrii Nakryiko wrote:
> On Wed, Feb 3, 2021 at 12:15 PM Randy Dunlap <rdunlap@xxxxxxxxxxxxx> wrote:
>>
>> 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 ]
>>
>>
>
> Sounds exactly like my case. I removed
> $(O)/tools/bpf/resolve_btfids/{feature/,FEATURE-DUMP.libbpf} and it
> started working.
I already tried that with no success.
I suppose that it could be related to how I do builds:
make ARCH=x86_64 O=subdir -j4 all
so subdir is a relative path, not an absolute path.
--
~Randy
