Subject: Re: [PATCH 1/3] perf: Add capability-related utilities

From: Arnaldo Carvalho de Melo <[email-masked]>
Date: Wed, 17 Jul 2019 20:46:52 -0300

Em Wed, Jul 17, 2019 at 06:05:51PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Tue, Jul 16, 2019 at 10:46:43AM +0200, Jiri Olsa escreveu:
> > On Tue, Jul 02, 2019 at 08:10:03PM -0400, Igor Lubashev wrote:
> > > Add utilities to help checking capabilities of the running process.
> > > Make perf link with libcap.
> > > 
> > > Signed-off-by: Igor Lubashev <[email-masked]>
> > > ---
> > >  tools/perf/Makefile.config         |  2 +-
> > >  tools/perf/util/Build              |  1 +
> > >  tools/perf/util/cap.c              | 24 ++++++++++++++++++++++++
> > >  tools/perf/util/cap.h              | 10 ++++++++++
> > >  tools/perf/util/event.h            |  1 +
> > >  tools/perf/util/python-ext-sources |  1 +
> > >  tools/perf/util/util.c             |  9 +++++++++
> > >  7 files changed, 47 insertions(+), 1 deletion(-)
> > >  create mode 100644 tools/perf/util/cap.c
> > >  create mode 100644 tools/perf/util/cap.h
> > > 
> > > diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
> > > index 85fbcd265351..21470a50ed39 100644
> > > --- a/tools/perf/Makefile.config
> > > +++ b/tools/perf/Makefile.config
> > > @@ -259,7 +259,7 @@ CXXFLAGS += -Wno-strict-aliasing
> > >  # adding assembler files missing the .GNU-stack linker note.
> > >  LDFLAGS += -Wl,-z,noexecstack
> > >  
> > > -EXTLIBS = -lpthread -lrt -lm -ldl
> > > +EXTLIBS = -lpthread -lrt -lm -ldl -lcap
> > 
> > I wonder we should detect libcap or it's everywhere.. Arnaldo's compile test suite might tell
> 
> I'll add this tentatively and try to build it in my test suite.

So, not even in my notebook this worked straight away:

  CC       /tmp/build/perf/util/cap.o
  CC       /tmp/build/perf/util/config.o
In file included from util/cap.c:5:
util/cap.h:6:10: fatal error: sys/capability.h: No such file or directory
    6 | #include <sys/capability.h>
      |          ^~~~~~~~~~~~~~~~~~
compilation terminated.
mv: cannot stat '/tmp/build/perf/util/.cap.o.tmp': No such file or directory

I had to first do:

dnf install libcap-devel

So we need to have a feature test and fail if that is not installed,
i.e. libcap becomes a hard req for building perf, which I think is
reasonable, one more shouldn't hurt, right?

With all the features enabled:

[acme@quaco perf]$ ldd ~/bin/perf
	linux-vdso.so.1 (0x00007ffe7278a000)
	libunwind-x86_64.so.8 => /lib64/libunwind-x86_64.so.8 (0x00007f7be52f1000)
	libunwind.so.8 => /lib64/libunwind.so.8 (0x00007f7be52d7000)
	liblzma.so.5 => /lib64/liblzma.so.5 (0x00007f7be52ae000)
	libpthread.so.0 => /lib64/libpthread.so.0 (0x00007f7be528d000)
	librt.so.1 => /lib64/librt.so.1 (0x00007f7be5283000)
	libm.so.6 => /lib64/libm.so.6 (0x00007f7be513d000)
	libdl.so.2 => /lib64/libdl.so.2 (0x00007f7be5135000)
	libcap.so.2 => /lib64/libcap.so.2 (0x00007f7be512e000)
	libelf.so.1 => /lib64/libelf.so.1 (0x00007f7be5113000)
	libdw.so.1 => /lib64/libdw.so.1 (0x00007f7be50c0000)
	libslang.so.2 => /lib64/libslang.so.2 (0x00007f7be4de8000)
	libperl.so.5.28 => /lib64/libperl.so.5.28 (0x00007f7be4ac2000)
	libc.so.6 => /lib64/libc.so.6 (0x00007f7be48fa000)
	libpython2.7.so.1.0 => /lib64/libpython2.7.so.1.0 (0x00007f7be4690000)
	libz.so.1 => /lib64/libz.so.1 (0x00007f7be4676000)
	libzstd.so.1 => /lib64/libzstd.so.1 (0x00007f7be45d1000)
	libnuma.so.1 => /lib64/libnuma.so.1 (0x00007f7be45c3000)
	libbabeltrace-ctf.so.1 => /lib64/libbabeltrace-ctf.so.1 (0x00007f7be456d000)
	libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00007f7be4551000)
	/lib64/ld-linux-x86-64.so.2 (0x00007f7be5331000)
	libbz2.so.1 => /lib64/libbz2.so.1 (0x00007f7be453d000)
	libcrypt.so.2 => /lib64/libcrypt.so.2 (0x00007f7be4502000)
	libutil.so.1 => /lib64/libutil.so.1 (0x00007f7be44fd000)
	libbabeltrace.so.1 => /lib64/libbabeltrace.so.1 (0x00007f7be44ed000)
	libpopt.so.0 => /lib64/libpopt.so.0 (0x00007f7be44dd000)
	libuuid.so.1 => /lib64/libuuid.so.1 (0x00007f7be44d3000)
	libgmodule-2.0.so.0 => /lib64/libgmodule-2.0.so.0 (0x00007f7be44cd000)
	libglib-2.0.so.0 => /lib64/libglib-2.0.so.0 (0x00007f7be43a9000)
	libpcre.so.1 => /lib64/libpcre.so.1 (0x00007f7be4335000)
[acme@quaco perf]$

;-)

So, please check tools/build/feature/ and check how this is done and add
a test and the warning in tools/perf/Makefile.config so that we get an
error message stating that libcap-dev or libcap-devel should be
installed.

I'll do it if there is any difficulty, just not right now as I'm busy
and want to get a pull req out of the door.

- Arnaldo

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