Re: Cannot load eBPF program as XDP

[Jesper Dangaard Brouer <brouer@redhat.com>]

On Tue, 27 Jun 2017 22:32:26 -0400 "MD I. Islam" <tamim@csebuet.org> wrote:

> Hi Song
> 
> On Tue, Jun 27, 2017 at 10:05 PM, Y Song <ys114321@gmail.com> wrote:
> > xdp meta data is different:
> >
> > struct xdp_md {
> >         __u32 data;
> >         __u32 data_end;
> > };
> >
> > All other fields available for skb metadata won't be available in XDP.
> > That is way
> > you get verification failure.
> >  
> 
> 
> Thanks for the quick reply! Now I'm trying xdp1_kern.c which uses
> xdp_md. Now I'm getting the error:
> 
> Note: 8 bytes struct bpf_elf_map fixup performed due to size mismatch!
> RTNETLINK answers: Operation not supported
> 
> Could you please advise me what is wrong here?

The xdp1_kern.c bpf program expect to be loaded with the tool
xdp1_user.c (compiled to executable xdp1) which uses the bpf-elf loader
located in the kernel/samples/bpf/ directory.

You are trying to load this xdp1_kern.c program with the TC utility,
which have it's own bpf-elf loader.  These two loaders are not expected
to be compatible... specifically struct bpf_elf_map are different.


p.s. I'm maintaining some bpf samples here: 
 https://github.com/netoptimizer/prototype-kernel/tree/master/kernel/samples/bpf

--Jesper
 
> > On Tue, Jun 27, 2017 at 7:00 PM, MD I. Islam <tamim@csebuet.org> wrote:  
> >> Hi
> >>
> >> I'm using http://lingrok.org/xref/linux-net-next/samples/bpf/parse_simple.c.
> >>
> >> I can load the program as tc_cls using following commands:
> >>
> >> sudo tc qdisc add dev eno1 clsact
> >> sudo tc filter add dev eno1  ingress bpf da obj parse_simple.o sec simple
> >>
> >> But I get error when I load the same program in XDP:
> >>
> >> sudo ip link set dev eno1 xdp obj parse_simple.o section simple
> >>
> >> Prog section 'simple' rejected: Permission denied (13)!
> >>  - Type:         6
> >>  - Instructions: 23 (0 over limit)
> >>  - License:      GPL
> >>
> >> Verifier analysis:
> >>
> >> 0: (b7) r0 = 0
> >> 1: (61) r2 = *(u32 *)(r1 +80)
> >> invalid bpf_context access off=80 size=4
> >>
> >> Error fetching program/map!
> >>
> >> I made sure that the parse_simple.o have necessary permission. Could
> >> you please advise what is wrong here? I'm using Kernel 4.11+. Does XDP
> >> need any specific kernel configuration enabled? clang and LLVM
> >> versions are as following:
> >>
> >> clang --version
> >> clang version 3.8.0-2ubuntu4 (tags/RELEASE_380/final)
> >> Target: x86_64-pc-linux-gnu
> >>
> >> llc --version
> >> LLVM (http://llvm.org/):
> >>   LLVM version 3.8.0
> >>
> >>   Optimized build.
> >>   Built Jul  9 2016 (11:22:59).
> >>   Default target: x86_64-pc-linux-gnu
> >>   Host CPU: haswell
> >>
> >>   Registered Targets:
> >>     aarch64    - AArch64 (little endian)
> >>     aarch64_be - AArch64 (big endian)
> >>     amdgcn     - AMD GCN GPUs
> >>     arm        - ARM
> >>     arm64      - ARM64 (little endian)
> >>     armeb      - ARM (big endian)
> >>     bpf        - BPF (host endian)
> >>     bpfeb      - BPF (big endian)
> >>     bpfel      - BPF (little endian)
> >>     cpp        - C++ backend
> >>     hexagon    - Hexagon
> >>     mips       - Mips
> >>     mips64     - Mips64 [experimental]
> >>     mips64el   - Mips64el [experimental]
> >>     mipsel     - Mipsel
> >>     msp430     - MSP430 [experimental]
> >>     nvptx      - NVIDIA PTX 32-bit
> >>     nvptx64    - NVIDIA PTX 64-bit
> >>     ppc32      - PowerPC 32
> >>     ppc64      - PowerPC 64
> >>     ppc64le    - PowerPC 64 LE
> >>     r600       - AMD GPUs HD2XXX-HD6XXX
> >>     sparc      - Sparc
> >>     sparcel    - Sparc LE
> >>     sparcv9    - Sparc V9
> >>     systemz    - SystemZ
> >>     thumb      - Thumb
> >>     thumbeb    - Thumb (big endian)
> >>     x86        - 32-bit X86: Pentium-Pro and above
> >>     x86-64     - 64-bit X86: EM64T and AMD64
> >>     xcore      - XCore
> >>
> >> Many thanks
> >> Tamim  
> 
> Thanks
> Tamim



-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer