Re: Cannot load eBPF program as XDP

[Daniel Borkmann <daniel@iogearbox.net>]

On 06/28/2017 04:32 AM, MD I. Islam wrote:
> 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!

This one is harmless, just telling you that the native bpf_elf_map
from iproute2 is different than the one you're loading, so it fixes
up the remaining 8 bytes automatically.

> RTNETLINK answers: Operation not supported

This one seems likely that the driver you're trying to attach this to
does not have XDP support. What's the driver you're using?

> Could you please advise me what is wrong here?
>
>> 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
>