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

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

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.
>> Because I have another patch in my local tree which also modifis bpf
>> Makefile:
>>
>> http://lkml.kernel.org/g/1450316632-152513-1-git-send-email-wangnan0@huawei.com
>>
>> sorry.
> Ah, that explains it this problem.
>
>>> After fixing this manually
>>> I was able to continue to the build step:
>>>
>>> $ 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
>>> 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
>>> No libelf found
>>> Makefile:203: recipe for target 'elfdep' failed
>>> make[2]: *** [elfdep] Error 255
>>> samples/bpf/Makefile:10: recipe for target
>>> 'samples/bpf/libbpf/libbpf.a' failed
>>> make[1]: *** [samples/bpf/libbpf/libbpf.a] Error 2
>>> Makefile:1550: recipe for target 'samples/bpf/' failed
>>> make: *** [samples/bpf/] Error 2
>> 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.

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-* ?

Thank you.