[dpdk-dev] BUG: eBPF missing BPF_ABS

Jerin Jacob jerinjacobk at gmail.com
Thu Feb 6 05:22:01 CET 2020


On Thu, Feb 6, 2020 at 2:46 AM Ananyev, Konstantin
<konstantin.ananyev at intel.com> wrote:
>
> >

>
> Second question is implementation.
> I can see two main options here:
> a) if we plan to have our own cBPF->eBPF converter and support only it,
> we can add these extra instructions generation into converter itself.
> I.E. cBPF->eBPF conversion for LD_ABS/LD_IND will generate series
> of generic eBPF instructions.
> b) support eBPF LD_ABS/LD_IND in eBPF interpreter/jit
>
> (a) probably a simpler way (eBPF interpreter/jit/verifier would remain unchanged),
> but seems way too limited. So I think (b) is a better choice, even more work implied
> (interpreter seems more or less straightforward, jit would probably need some effort).

Looks like cBPF is an important use case. If we are leveraging code
cBPF->eBPF code
from somewhere and there is limited option to change then it is better
to add our JIT.
I can work on adding arm64 JIT support once base code in place.


>
> Any thoughts/opinions?
> Konstantin
>
> >
> > PCAP filter string: ip dst fosdem.org
> > cBPF program (6 insns):
> >  L0:  28 00 00 00 0c 00 00 00 ldh [12]
> >  L1:  15 00 00 03 00 08 00 00 jeq #0x800, L2, L5
> >  L2:  20 00 00 00 1e 00 00 00 ld [30]
> >  L3:  15 00 00 01 8c 16 16 1f jeq #0x1f16168c, L4, L5
> >  L4:  06 00 00 00 ff ff ff ff ret #0xffffffff
> >  L5:  06 00 00 00 00 00 00 00 ret #0x0
> > eBPF program (11 insns):
> >  L0:  af 00 00 00 00 00 00 00 xor r0, r0
> >  L1:  af 77 00 00 00 00 00 00 xor r7, r7
> >  L2:  bf 16 00 00 00 00 00 00 mov r6, r1
> >  L3:  28 70 00 00 0c 00 00 00 ldh r0, [12]
> >  L4:  55 00 04 00 00 08 00 00 jne r0, #0x800, L9
> >  L5:  20 70 00 00 1e 00 00 00 ldw r0, [30]
> >  L6:  55 00 02 00 8c 16 16 1f jne r0, #0x1f16168c, L9
> >  L7:  b4 00 00 00 01 00 00 00 mov32 r0, #0x1
> >  L8:  95 00 00 00 00 00 00 00 exit
> >  L9:  b4 00 00 00 02 00 00 00 mov32 r0, #0x2
> >  L10: 95 00 00 00 00 00 00 00 exit
> > validate: invalid opcode at pc: 3
> > validate: invalid opcode at pc: 5
> > rte_bpf_load failed: Invalid argument


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