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

[Wangnan (F)]

On 2015/12/17 16:29, Daniel Wagner wrote:
> On 12/17/2015 08:03 AM, Daniel Wagner wrote:
> > On 12/17/2015 07:51 AM, Wangnan (F) wrote:
> > > On 2015/12/17 14:38, Daniel Wagner wrote:
> > > > On 12/17/2015 06:23 AM, Wang Nan wrote:
> > > > > Since we already have libbpf in tools/lib, we don't need to maintain
> > > > > another bpf loader and operations library in samples/bpf.
> > > > >
> > > > > In patchset:
> > > > >
> > > > >    Patch 1/10 - 7/10 improves libbpf, add missing features to support
> > > > >    samples,
> > > > >
> > > > >    Patch 8/10 adds utils.[ch], which creates similar API like old
> > > > >    bpf_load.c and libbpf.c.
> > > > >
> > > > >    Patch 9/10 replace all sampels to use API provides by utils.[ch] and
> > > > >    libbpf.
> > > > >
> > > > >    Patch 10/10 removes unneeded files.
> > > > Which tree did you use for your patches? I tried to apply them against
> > > > mainline and net-next which didn't really work out.
> > > These patches based on Arnaldo's 'perf/core' because of those libbpf
> > > changes.
> > Okay, I'll try with this one.
> I applied those patches on top of
>
> 5c560cfcf1c0 ("tools subcmd: Rename subcmd header include guards")
>
> 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@xxxxxxxxxx

sorry.

> 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

?

This error means it can't find libelf on your platform, but it is not true obviously.


> Executing the above command line by myself in order
> to figure out what's going on ended in this mess:
>
>
> $ 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
> make: Entering directory '/home/wagi/src/linux/tools/lib/bpf'
>
> Auto-detecting system features:
> ...                        libelf: [ on  ]
> ...                           bpf: [ on  ]
>
> [...]
>
> samples/bpf/fds_example.c: In function âbpf_do_mapâ:
> samples/bpf/fds_example.c:78:9: warning: implicit declaration of function âbpf_pin_objectâ [-Wimplicit-function-declaration]
>     ret = bpf_pin_object(fd, file);
>           ^
> samples/bpf/fds_example.c:82:8: warning: implicit declaration of function âbpf_get_pinned_objectâ [-Wimplicit-function-declaration]
>     fd = bpf_get_pinned_object(file);
>          ^
>    gcc -Lsamples/bpf/libbpf -o samples/bpf/fds_example samples/bpf/utils.o samples/bpf/fds_example.o -lelf -lbpf
> samples/bpf/fds_example.o: In function `main':
> fds_example.c:(.text.startup+0x20e): undefined reference to `bpf_pin_object'
> fds_example.c:(.text.startup+0x2b0): undefined reference to `bpf_pin_object'
> fds_example.c:(.text.startup+0x2f3): undefined reference to `bpf_get_pinned_object'
> fds_example.c:(.text.startup+0x344): undefined reference to `bpf_get_pinned_object'
> collect2: error: ld returned 1 exit status
> scripts/Makefile.host:100: recipe for target 'samples/bpf/fds_example' failed
> make[1]: *** [samples/bpf/fds_example] Error 1
> Makefile:1550: recipe for target 'samples/bpf/' failed
> make: *** [samples/bpf/] Error 2
> [wagi@handman linux (bpf-test)]$ 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
>    HOSTLD  samples/bpf/fds_example
> samples/bpf/fds_example.o: In function `main':
> fds_example.c:(.text.startup+0x20e): undefined reference to `bpf_pin_object'
> fds_example.c:(.text.startup+0x2b0): undefined reference to `bpf_pin_object'
> fds_example.c:(.text.startup+0x2f3): undefined reference to `bpf_get_pinned_object'
> fds_example.c:(.text.startup+0x344): undefined reference to `bpf_get_pinned_object'
> collect2: error: ld returned 1 exit status

Could you please check whether this patch:

 bpf tools: Support BPF_OBJ_PIN and BPF_OBJ_GET

is applied properly?

Thank you.

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