Re: Build failures: unresolved symbol vfs_getattr

[Jiri Olsa <jolsa@redhat.com>]

On Mon, Sep 14, 2020 at 03:26:33PM -0700, Andrii Nakryiko wrote:
> On Mon, Sep 14, 2020 at 11:25 AM Jiri Olsa <jolsa@redhat.com> wrote:
> >
> > On Mon, Sep 14, 2020 at 10:48:36AM -0400, Veronika Kabatova wrote:
> > >
> > > Hello,
> > >
> > > we tested the bpf-next tree with CKI and ran across build failures. The
> > > important part of the build log is:
> > >
> > > 00:18:05   GEN     .version
> > > 00:18:05   CHK     include/generated/compile.h
> > > 00:18:05   LD      vmlinux.o
> > > 00:18:27   MODPOST vmlinux.symvers
> > > 00:18:27   MODINFO modules.builtin.modinfo
> > > 00:18:27   GEN     modules.builtin
> > > 00:18:27   LD      .tmp_vmlinux.btf
> > > 00:18:42   BTF     .btf.vmlinux.bin.o
> > > 00:19:13   LD      .tmp_vmlinux.kallsyms1
> > > 00:19:19   KSYM    .tmp_vmlinux.kallsyms1.o
> > > 00:19:22   LD      .tmp_vmlinux.kallsyms2
> > > 00:19:25   KSYM    .tmp_vmlinux.kallsyms2.o
> > > 00:19:28   LD      vmlinux
> > > 00:19:40   BTFIDS  vmlinux
> > > 00:19:40 FAILED unresolved symbol vfs_getattr
> > > 00:19:40 make[2]: *** [Makefile:1167: vmlinux] Error 255
> > > 00:19:40 make[1]: *** [scripts/Makefile.package:109: targz-pkg] Error 2
> > > 00:19:40 make: *** [Makefile:1528: targz-pkg] Error 2
> >
> > hi,
> > it looks like broken BTF data to me, I checked that build
> > and found we have multiple records for functions, like
> > for filp_close:
> >
> >         [23381] FUNC_PROTO '(anon)' ret_type_id=19 vlen=2
> >                 '(anon)' type_id=464
> >                 'id' type_id=960
> >         [23382] FUNC 'filp_close' type_id=23381 linkage=static
> >
> >
> >         [33073] FUNC_PROTO '(anon)' ret_type_id=19 vlen=2
> >                 'filp' type_id=464
> >                 'id' type_id=960
> >         [33074] FUNC 'filp_close' type_id=33073 linkage=static
> >
> >
> > or vfs_getattr:
> >
> >         [33513] FUNC_PROTO '(anon)' ret_type_id=19 vlen=4
> >                 'path' type_id=741
> >                 'stat' type_id=1095
> >                 'request_mask' type_id=29
> >                 'query_flags' type_id=8
> >
> >         [33514] FUNC 'vfs_getattr' type_id=33513 linkage=static
> >
> >         [1094] FUNC_PROTO '(anon)' ret_type_id=19 vlen=4
> >                 '(anon)' type_id=741
> >                 '(anon)' type_id=1095
> >                 '(anon)' type_id=29
> >                 '(anon)' type_id=8
> >
> >         [35099] FUNC 'vfs_getattr' type_id=1094 linkage=static
> >
> >
> > and because we go through all BTF data until we resolve all we have,
> > the doubled funcs will screw our internal counter and we skip a function
> >
> > the change below will workaround that, but I think we should fail in
> > this case.. if I'm not missing something 2 FUNC records for one function
> > in BTF data
> >
> > $ pahole --version
> > v1.17
> >
> > HEAD is 2bab48c5b Merge branch 'improve-bpf-tcp-cc-init'
> >
> > thoughts? thanks
> 
> Can't repro this locally. It must be some bad compiler +  DWARF +
> pahole interaction. Can you try building pahole from latest sources
> and try again? Also, what compiler did you use? What Kconfig?

sorry I cut the original message, there's following container that
reproduces the issue:

	The failure is easily reproduced with our container image that already
	has all the needed dependencies installed:
	registry.gitlab.com/cki-project/containers/builder-rawhide:latest

	Steps to reproduce after starting the image:

	git clone https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git --depth 1
	curl https://gitlab.com/-/snippets/2014934/raw -o bpf-next/.config
	cd bpf-next/
	make -j 10 INSTALL_MOD_STRIP=1 targz-pkg


[root@30a9be783e4e /]# gcc --version
gcc (GCC) 10.2.1 20200826 (Red Hat 10.2.1-3)

I built the latest pahole in that container and still see the issue,
I also tried with v1.16 version and it's still there

I don't see the issue when I build kernel with another .config
so I'll try to check on that now

jirka