Re: Error loading xdp program that worked with bpf_load

From: Andrii Nakryiko <andrii.nakryiko@gmail.com>
To: Elerion <elerion1000@gmail.com>
Cc: "Jesper Dangaard Brouer" <brouer@redhat.com>,
	"iovisor-dev@lists.iovisor.org" <iovisor-dev@lists.iovisor.org>,
	"Toke Høiland-Jørgensen" <toke@redhat.com>,
	Xdp <xdp-newbies@vger.kernel.org>,
	"Yonghong Song" <ys114321@gmail.com>
Subject: Re: Error loading xdp program that worked with bpf_load
Date: Thu, 11 Jun 2020 13:46:13 -0700	[thread overview]
Message-ID: <CAEf4BzZRd6HU8XWAdTkGggQtcKY+f_Ha2Oe4oeNGCpESGkpq4g@mail.gmail.com> (raw)
In-Reply-To: <CAMDScmk+vXCwOYkWhwUcdg95EsCsJNBnM0Jj=nHQLcGPJxiAgw@mail.gmail.com>

On Thu, Jun 11, 2020 at 1:41 PM Elerion <elerion1000@gmail.com> wrote:
>
> I am using libbpf from here https://github.com/libbpf/libbpf I'm not
> using ebpf. I just linked to the ebpf issue because it seems like the
> only thing related to this problem when I googled it.

Ok, that I can help with, then.

What's the kernel version? Where I can find repro? Steps, etc.
Basically, a bit more context would help, as I wasn't part of initial
discussion.

>
> On Thu, Jun 11, 2020 at 9:34 AM Andrii Nakryiko
> <andrii.nakryiko@gmail.com> wrote:
> >
> > On Thu, Jun 11, 2020 at 4:00 AM Jesper Dangaard Brouer
> > <brouer@redhat.com> wrote:
> > >
> > > (Cross-posting to iovisor-dev)
> > >
> > > Seeking input from BPF-llvm developers. How come Clang/LLVM 10+ is
> > > generating incompatible BTF-info in ELF file, and downgrading to LLVM-9
> > > fixes the issue ?
> > >
> > >
> > > On Wed, 10 Jun 2020 14:50:27 -0700 Elerion <elerion1000@gmail.com> wrote:
> > >
> > > > Never mind, I fixed it by downgrading to Clang 9.
> > > >
> > > > It appears to be an issue with Clang/LLVM 10+
> > > >
> > > > https://github.com/cilium/ebpf/issues/43
> >
> > This is newer Clang recording that function is global, not static.
> > libbpf is sanitizing BTF to remove this flag, if kernel doesn't
> > support this. But given this is re-implementation of libbpf, that's
> > probably not happening, right?
> >
> > > >
> > > > On Wed, Jun 10, 2020 at 2:38 PM Toke Høiland-Jørgensen <toke@redhat.com> wrote:
> > > > >
> > > > > Elerion <elerion1000@gmail.com> writes:
> > > > >
> > > > > > [69] FUNC xdp_program type_id=68 vlen != 0
> > > > >
> > > > > 'vlen != 0' is the error. Not sure why you hit that; what's the output
> > > > > of 'bpftool btf dump file yourprog.o' ?
> > > > >
> > > > > -Toke
> > > > >
> > >
> > >
> > > --
> > > Best regards,
> > >   Jesper Dangaard Brouer
> > >   MSc.CS, Principal Kernel Engineer at Red Hat
> > >   LinkedIn: http://www.linkedin.com/in/brouer
> > >