Re: finding libelf

[Randy Dunlap <rdunlap@infradead.org>]

On 2/3/21 2:57 AM, Toke Høiland-Jørgensen wrote:
> Randy Dunlap <rdunlap@infradead.org> writes:
> 
>> Hi,
>>
>> I see this sometimes when building a kernel: (on x86_64,
>> with today's linux-next 20210202):
>>
>>
>> CONFIG_CGROUP_BPF=y
>> CONFIG_BPF=y
>> CONFIG_BPF_SYSCALL=y
>> CONFIG_ARCH_WANT_DEFAULT_BPF_JIT=y
>> CONFIG_BPF_PRELOAD=y
>> CONFIG_BPF_PRELOAD_UMD=m
>> CONFIG_HAVE_EBPF_JIT=y
>>
>>
>> Auto-detecting system features:
>> ...                        libelf: [ [31mOFF[m ]
>> ...                          zlib: [ [31mOFF[m ]
>> ...                           bpf: [ [31mOFF[m ]
>>
>> No libelf found
>> make[5]: [Makefile:287: elfdep] Error 1 (ignored)
>> No zlib found
>> make[5]: [Makefile:290: zdep] Error 1 (ignored)
>> BPF API too old
>> make[5]: [Makefile:293: bpfdep] Error 1 (ignored)
>>
>>
>> but pkg-config tells me:
>>
>> $ pkg-config --modversion  libelf
>> 0.168
>> $ pkg-config --libs  libelf
>> -lelf
>>
>>
>> Any ideas?
> 
> This usually happens because there's a stale cache of the feature
> detection tests lying around somewhere. Look for a 'feature' directory
> in whatever subdir you got that error. Just removing the feature
> directory usually fixes this; I've fixed a couple of places where this
> is not picked up by 'make clean' (see, e.g., 9d9aae53b96d ("bpf/preload:
> Make sure Makefile cleans up after itself, and add .gitignore")) but I
> wouldn't be surprised if there are still some that are broken.

Hi,

Thanks for replying.

I removed the feature subdir and still got this build error, so I
removed everything in BUILDDIR/kernel/bpf/preload and rebuilt --
and still got the same libelf build error.


-- 
~Randy