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

[Lubashev, Igor]

On Wed, July 17 at 2019 7:47 PM  Arnaldo Carvalho de Melo wrote:
> 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 <ilubashe@xxxxxxxxxx>
> > > > ---
> > > >  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 have just posted v2 of the series (https://lkml.kernel.org/lkml/cover.1565146171.git.ilubashe@xxxxxxxxxx).

Instead of making libcap is "hard req", I made it as "soft" one. We can still build a useful tool w/o libcap. It will just have to assume that perf is running with no capabilities, since we cannot query them.

Many thanks for the pointers on how to go about build feature checking.

- Igor