2018-12-15 00:56 UTC+0100 ~ Daniel Borkmann <dan...@iogearbox.net>
> On 12/13/2018 01:19 PM, Quentin Monnet wrote:
>> Add probes to dump a number of options set (or not set) for compiling
>> the kernel image. These parameters provide information about what BPF
>> components should be available on the system. A number of them are not
>> directly related to eBPF, but are in fact used in the kernel as
>> conditions on which to compile, or not to compile, some of the eBPF
>> helper functions.
>>
>> Sample output:
>>
>> # bpftool feature probe kernel
>> Scanning system configuration...
>> ...
>> CONFIG_BPF is set to y
>> CONFIG_BPF_SYSCALL is set to y
>> CONFIG_HAVE_EBPF_JIT is set to y
>> ...
>>
>> # bpftool --pretty --json feature probe kernel
>> {
>> "system_config": {
>> ...
>> "CONFIG_BPF": "y",
>> "CONFIG_BPF_SYSCALL": "y",
>> "CONFIG_HAVE_EBPF_JIT": "y",
>> ...
>> }
>> }
>>
>> # bpftool feature probe kernel macros prefix BPFTOOL_
>> /*** System configuration ***/
>> ...
>> #define BPFTOOL_CONFIG_BPF y
>> #define BPFTOOL_CONFIG_BPF_SYSCALL y
>> #define BPFTOOL_CONFIG_HAVE_EBPF_JIT y
>> ...
>
> Looks reasonable. I think as a user next question that would
> follow-up from it would be whether this set of config means
> that e.g. requirements for XDP, cgroups bpf, tracing or xyz is
> fulfilled. Perhaps it makes sense to split the options[] into
> base_options[], bpf_trace_options[], bpf_tc_options[] etc such
> that it might become obvious that base_options[] + bpf_tc_options[]
> are supported and thus cls_bpf could be used. I'd see this part
> here in general more as giving a hint to the user in that some
> basic assumptions could be made and providing some info on the
> misc ones on what might potentially be missing. Though more
> concrete info would come from the actual helper / map / prog
> type probing.
Good idea. I admit that the list of options dumped with no explanations
whatsoever is hard to interpret. I'll try to divide the list into
meaningful subsections.
