Re: [RFC PATCH v9 02/50] tools build: Add feature check for eBPF API

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Em Mon, Jun 29, 2015 at 04:21:51PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Fri, Jun 26, 2015 at 02:15:07PM +0000, Wang Nan escreveu:
> > In this patch, eBPF API is checked by compiling a c source file which
> > uses fields in bpf_attr which will be used by libbpf.
> > 
> > Signed-off-by: Wang Nan <wangnan0@huawei.com>
> > Acked-by: Alexei Starovoitov <ast@plumgrid.com>
> 
> So, I just applied this and after trying:
> 
> [acme@felicio linux]$ rm -rf /tmp/build/perf ; mkdir -p /tmp/build/perf
> ; make O=/tmp/build/perf -C tools/perf  install-bin
> make: Entering directory `/home/acme/git/linux/tools/perf'
>   BUILD:   Doing 'make -j4' parallel build
> 
> Auto-detecting system features:
> ...                         dwarf: [ on  ]
> ...                         glibc: [ on  ]
> ...                          gtk2: [ on  ]
> ...                      libaudit: [ on  ]
> ...                        libbfd: [ on  ]
> ...                        libelf: [ on  ]
> ...                       libnuma: [ on  ]
> ...                       libperl: [ on  ]
> ...                     libpython: [ on  ]
> ...                      libslang: [ on  ]
> ...                     libunwind: [ on  ]
> ...            libdw-dwarf-unwind: [ on  ]
> ...                          zlib: [ on  ]
> ...                          lzma: [ on  ]
> ...                           bpf: [ OFF ]
> 
>   MKDIR    /tmp/build/perf/util/
>   CC       /tmp/build/perf/util/abspath.o
> 
> --------------------------------------------------------
> 
> So, what should I do now? I want to have that OFF line turned to "on",
> so that I can test this stuff.
> 
> But the changelog says nothing about it, lemme check the cover letter,
> but having to do that is annoying, one expects to have instructions
> related to some specific changeset in its comments...

So, when such build tests fail, we can see why by looking for a file
with a special name in the O= output dir:

[acme@felicio linux]$ cat /tmp/build/perf/feature/test-bpf.make.output
test-bpf.c:1:23: fatal error: linux/bpf.h: No such file or directory
 #include <linux/bpf.h>
                       ^
compilation terminated.
[acme@felicio linux]$

Right, one of the few things that could explain the failure, but:

[acme@felicio linux]$ find . -name bpf.h
./include/linux/bpf.h
./include/uapi/linux/bpf.h
[acme@felicio linux]$ 

So lemme try doing it in place:

[acme@felicio linux]$ make -C tools/perf/
make: Entering directory `/home/acme/git/linux/tools/perf'
  BUILD:   Doing 'make -j4' parallel build

Auto-detecting system features:
...                         dwarf: [ on  ]
...                         glibc: [ on  ]
...                          gtk2: [ on  ]
...                      libaudit: [ on  ]
...                        libbfd: [ on  ]
...                        libelf: [ on  ]
...                       libnuma: [ on  ]
...                       libperl: [ on  ]
...                     libpython: [ on  ]
...                      libslang: [ on  ]
...                     libunwind: [ on  ]
...            libdw-dwarf-unwind: [ on  ]
...                          zlib: [ on  ]
...                          lzma: [ on  ]
...                           bpf: [ OFF ]


Doesn't work as well :-\

Looking at the following patches...

- Arnaldo