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s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=3uEQdY8Xux5V87lgCfUcEHRWUvlbpZ6oypO5tdmy43k=; b=VuxKiWAXWsK8oElx8YoxAEg+ysKyX8Ouh2zzN6WEVjYh+BfTRn8O00MUV1Cl/78cCt qIPmauLjfaHOidleNdkGmIDFa6XJUgVrP95SVaBJHtEOG9qOvkcBvBdDdgVBGUTbZTjb v1eiSQ3DVvzwdJVdHSr3ISa/lo7+6SxbKABowgLKM770gUiU0sVd3A2xPbFapEPSgAq1 euKyTXk68+rOujCwOjQxmEUH0KeWqQq5X6I3p0YGhcLxlijcPbCdV0LKSqLDheX25Rr5 a6Dqq2MkBGcon5pHWYBefRkqSPFmUMqZKI7LMl8Yrxb7ldpBs0hNqzLupSdpAeMhwfTo QhIA== X-Gm-Message-State: AOAM531QnT8NP2i8/cKJ1cMx6xE/w7ueXUyqdgit2xbE2f0MIlWtnLu+ gNRHu9Sq3L/VID2JiQ233SD8bMTN/N6Yt6kNGGM= X-Google-Smtp-Source: ABdhPJwIAwcSlwPNJP0+WnCyVuiDLI2Te3hmCJByUSBBMfeCZS12pipxCQOgHnf3ycbJyHd+M1F7Ky/ov4gytKpL9AI= X-Received: by 2002:a5b:3c4:: with SMTP id t4mr6710463ybp.510.1612384879745; Wed, 03 Feb 2021 12:41:19 -0800 (PST) MIME-Version: 1.0 References: <8a6894e9-71ef-09e3-64fa-bf6794fc6660@infradead.org> <87eehxa06v.fsf@toke.dk> <44e6edc6-736e-dadb-c523-eabff8de89c0@infradead.org> <93a6f6b6-167a-a2c6-f0dc-621d5a7bfc20@infradead.org> <01ffaa2e-c0fd-95a1-a60a-eb90cbf868ad@infradead.org> In-Reply-To: <01ffaa2e-c0fd-95a1-a60a-eb90cbf868ad@infradead.org> From: Andrii Nakryiko Date: Wed, 3 Feb 2021 12:41:08 -0800 Message-ID: Subject: Re: finding libelf To: Randy Dunlap Cc: =?UTF-8?B?VG9rZSBIw7hpbGFuZC1Kw7hyZ2Vuc2Vu?= , bpf Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Wed, Feb 3, 2021 at 12:36 PM Randy Dunlap wrote: > > On 2/3/21 12:33 PM, Andrii Nakryiko wrote: > > On Wed, Feb 3, 2021 at 12:15 PM Randy Dunlap wr= ote: > >> > >> On 2/3/21 12:12 PM, Andrii Nakryiko wrote: > >>> On Wed, Feb 3, 2021 at 12:09 PM Randy Dunlap = wrote: > >>>> > >>>> On 2/3/21 11:39 AM, Andrii Nakryiko wrote: > >>>>> On Wed, Feb 3, 2021 at 9:22 AM Randy Dunlap = wrote: > >>>>>> > >>>>>> On 2/3/21 2:57 AM, Toke H=C3=B8iland-J=C3=B8rgensen wrote: > >>>>>>> Randy Dunlap writes: > >>>>>>> > >>>>>>>> Hi, > >>>>>>>> > >>>>>>>> I see this sometimes when building a kernel: (on x86_64, > >>>>>>>> with today's linux-next 20210202): > >>>>>>>> > >>>>>>>> > >>>>>>>> CONFIG_CGROUP_BPF=3Dy > >>>>>>>> CONFIG_BPF=3Dy > >>>>>>>> CONFIG_BPF_SYSCALL=3Dy > >>>>>>>> CONFIG_ARCH_WANT_DEFAULT_BPF_JIT=3Dy > >>>>>>>> CONFIG_BPF_PRELOAD=3Dy > >>>>>>>> CONFIG_BPF_PRELOAD_UMD=3Dm > >>>>>>>> CONFIG_HAVE_EBPF_JIT=3Dy > >>>>>>>> > >>>>>>>> > >>>>>>>> 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' dire= ctory > >>>>>>> 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/p= reload: > >>>>>>> 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 t= hat > >>>>> 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 simila= r > >>>>> 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 shou= ld > >>>>> 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. > >>>>> 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 libr= aries? > >> > >> 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=3Dx86_64 O=3Dsubdir -j4 all > > so subdir is a relative path, not an absolute path. so can you confirm this by specifying the absolute path to subdir? > > -- > ~Randy >