Re: [PATCH 00/10] bpf samples: Uses libbpf in tools/lib to do BPF operations

["Wangnan (F)" <wangnan0@huawei.com>]

On 2015/12/18 16:49, Daniel Wagner wrote:
> On 12/18/2015 04:04 AM, Wangnan (F) wrote:
>> On 2015/12/17 21:46, Daniel Wagner wrote:
>>> On 12/17/2015 11:09 AM, Wangnan (F) wrote:
>>>> On 2015/12/17 16:29, Daniel Wagner wrote:
>>>>> On 12/17/2015 08:03 AM, Daniel Wagner wrote:
>>>>> Patch number 2 didn't apply cleanly.
>>>> When you see this, could you please have a look at:
>>>>
>>>> /home/wagi/src/linux/samples/bpf/libbpf/feature/test-*.make.output
>>>>
>>>> ?
>>> test-libpython.c:1:20: fatal error: Python.h: No such file or directory
>> So it is the content in test-all.make.output ? Then it is
>> not a problem. It is only a fastpath which tries to check
>> all features by one test. On most platform it would fail.
> I see.
>
>> BPF related feature check is not in test-all. It is a potential
>> bug, but I don't think it causes your problem.
>>
>> Another problem is you didn't see this in the first failure:
>>
>> Auto-detecting system features:
>> ...                        libelf: [ on  ]
>> ...                           bpf: [ on  ]
>>
>> This only happen when you already have a FEATURE-DUMP.libbpf in that
>> directory and it is same as the feature check result.
>>
>> Could you please remove samples/bpf in your building tree and
>> try again? After you see the failure, what's the content of
>>
>> /home/wagi/src/linux/samples/bpf/libbpf/FEATURE-* ?
> I cleanup up my tree (rm samples/bpf/ and git checkout samples/bpf) and then
>
> $ make samples/bpf/
>    CHK     include/config/kernel.release
>    CHK     include/generated/uapi/linux/version.h
>    CHK     include/generated/utsrelease.h
>    CHK     include/generated/bounds.h
>    CHK     include/generated/timeconst.h
>    CHK     include/generated/asm-offsets.h
>    CALL    scripts/checksyscalls.sh
>    LD      samples/bpf/built-in.o
> make -C /home/wagi/src/linux/tools/lib/bpf O=/home/wagi/src/linux/samples/bpf/libbpf CFLAGS= LDFLAGS= V=1 /home/wagi/src/linux/samples/bpf/libbpf/libbpf.a
>
> Auto-detecting system features:
> ...                        libelf: [ OFF ]
> ...                           bpf: [ OFF ]

That's good. This is not a magic. I guess something in your top makefile
causes this feature check failure. I sent a patch on feature checker to you.
It will appear as [1] soon. Could you please apply it and try again?

This time you will see test-*.make.output and test-*.make.makeoutput.
test-*.make.output lists your PATH, PWD and the gcc command you use for
feature check. test-*.make.makeoutput is the output of 'make' itself. I 
think
from these information we can find the root cause easier.

Thank you.

[1] 
http://lkml.kernel.org/g/1450436211-170447-1-git-send-email-wangnan0@huawei.com