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.
> --
> ~Randy
>
