Re: [PATCH bpf-next] selftests/bpf: fix building bpf selftests statically

From: Andrii Nakryiko <andrii.nakryiko@gmail.com>
To: Yosry Ahmed <yosryahmed@google.com>
Cc: Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andrii@kernel.org>,
	Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
	Yonghong Song <yhs@fb.com>,
	John Fastabend <john.fastabend@gmail.com>,
	KP Singh <kpsingh@kernel.org>, Hao Luo <haoluo@google.com>,
	Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
	open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH bpf-next] selftests/bpf: fix building bpf selftests statically
Date: Fri, 13 May 2022 16:11:37 -0700	[thread overview]
Message-ID: <CAEf4BzZcCfTW7NnoH5CY8GVZv44SVwue+nQaEgyO1HO0YmGrWQ@mail.gmail.com> (raw)
In-Reply-To: <CAJD7tkaxHKUrb44-J5Zxm6x1KH-XnPVXDgZyu4+Rc094D7MEhA@mail.gmail.com>

On Fri, May 13, 2022 at 4:05 PM Yosry Ahmed <yosryahmed@google.com> wrote:
>
> On Fri, May 13, 2022 at 3:57 PM Andrii Nakryiko
> <andrii.nakryiko@gmail.com> wrote:
> >
> > On Thu, May 12, 2022 at 5:41 PM Yosry Ahmed <yosryahmed@google.com> wrote:
> > >
> > > bpf selftests can no longer be built with CFLAGS=-static with
> > > liburandom_read.so and its dependent target.
> > >
> > > Filter out -static for liburandom_read.so and its dependent target.
> > >
> > > Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
> > > ---
> > >  tools/testing/selftests/bpf/Makefile | 9 ++++++---
> > >  1 file changed, 6 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
> > > index 6bbc03161544..4eaefc187d5b 100644
> > > --- a/tools/testing/selftests/bpf/Makefile
> > > +++ b/tools/testing/selftests/bpf/Makefile
> > > @@ -168,14 +168,17 @@ $(OUTPUT)/%:%.c
> > >         $(call msg,BINARY,,$@)
> > >         $(Q)$(LINK.c) $^ $(LDLIBS) -o $@
> > >
> > > +# If the tests are being built statically, exclude dynamic libraries defined
> > > +# in this Makefile and their dependencies.
> > > +DYNAMIC_CFLAGS := $(filter-out -static,$(CFLAGS))
> >
> > I don't particularly like yet another CFLAGS global variable, but also
> > you are not filtering out -static from LDFLAGS, which would be
> > problematic if you try to do
> >
> > make SAN_FLAGS=-static
> >
> > which otherwise would work (and is probably better than overriding all of CFLAGS
> >
> > How about something like this
>
> Yeah this looks good, thanks for pointing out the problem with LDFLAGS.

ok, cool, please incorporate into v2 then

>
> >
> > diff --git a/tools/testing/selftests/bpf/Makefile
> > b/tools/testing/selftests/bpf/Makefile
> > index 6bbc03161544..2e8eddf240af 100644
> > --- a/tools/testing/selftests/bpf/Makefile
> > +++ b/tools/testing/selftests/bpf/Makefile
> > @@ -170,11 +170,11 @@ $(OUTPUT)/%:%.c
> >
> >  $(OUTPUT)/liburandom_read.so: urandom_read_lib1.c urandom_read_lib2.c
> >         $(call msg,LIB,,$@)
> > -       $(Q)$(CC) $(CFLAGS) -fPIC $(LDFLAGS) $^ $(LDLIBS) --shared -o $@
> > +       $(Q)$(CC) $(filter-out -static,$(CFLAGS) $(LDFLAGS)) $^
> > $(LDLIBS) -fPIC -shared -o $@
> >
> >  $(OUTPUT)/urandom_read: urandom_read.c urandom_read_aux.c
> > $(OUTPUT)/liburandom_read.so
> >         $(call msg,BINARY,,$@)
> > -       $(Q)$(CC) $(CFLAGS) $(LDFLAGS) $(filter %.c,$^)                        \
> > +       $(Q)$(CC) $(filter-out -static,$(CFLAGS) $(LDFLAGS)) $(filter %.c,$^)  \
> >                   liburandom_read.so $(LDLIBS)                                 \
> >                   -Wl,-rpath=. -Wl,--build-id=sha1 -o $@
> >
> > ?
> >
> >
> > But I also have a question, this leaves urandom_read relying on
> > system-wide shared libraries, isn't that still a problem for you? Or
> > you intend to just ignore urandom_read-related tests?
> >
>
> I wasn't running those tests, and I thought having most tests compile
> statically is better than nothing. Maybe this can be fixed by defining
> a static target for liburandom_read? I am honestly not sure, I have
> little experience with Makefiles/compilation.

usdt selftest explicitly tests working with shared libraries, so we
have to keep liburandom_read.so as a shared library. But yes, at least
you can skip the test at runtime.

>
> >
> > $ ldd urandom_read
> >         linux-vdso.so.1 (0x00007ffd0d5e5000)
> >         liburandom_read.so (0x00007fc7f7d76000)
> >         libelf.so.1 => /lib64/libelf.so.1 (0x00007fc7f7937000)
> >         libz.so.1 => /lib64/libz.so.1 (0x00007fc7f7720000)
> >         librt.so.1 => /lib64/librt.so.1 (0x00007fc7f7518000)
> >         libpthread.so.0 => /lib64/libpthread.so.0 (0x00007fc7f72f8000)
> >         libc.so.6 => /lib64/libc.so.6 (0x00007fc7f6f33000)
> >         /lib64/ld-linux-x86-64.so.2 (0x00007fc7f7b50000)
> >
> >
> >
> >
> > >  $(OUTPUT)/liburandom_read.so: urandom_read_lib1.c urandom_read_lib2.c
> > >         $(call msg,LIB,,$@)
> > > -       $(Q)$(CC) $(CFLAGS) -fPIC $(LDFLAGS) $^ $(LDLIBS) --shared -o $@
> > > +       $(Q)$(CC) $(DYNAMIC_CFLAGS) -fPIC $(LDFLAGS) $^ $(LDLIBS) --shared -o $@
> > >
> > >  $(OUTPUT)/urandom_read: urandom_read.c urandom_read_aux.c $(OUTPUT)/liburandom_read.so
> > >         $(call msg,BINARY,,$@)
> > > -       $(Q)$(CC) $(CFLAGS) $(LDFLAGS) $(filter %.c,$^)                        \
> > > -                 liburandom_read.so $(LDLIBS)                                 \
> > > +       $(Q)$(CC) $(DYNAMIC_CFLAGS) $(LDFLAGS) $(filter %.c,$^)                 \
> > > +                 liburandom_read.so $(LDLIBS)                                  \
> > >                   -Wl,-rpath=. -Wl,--build-id=sha1 -o $@
> > >
> > >  $(OUTPUT)/bpf_testmod.ko: $(VMLINUX_BTF) $(wildcard bpf_testmod/Makefile bpf_testmod/*.[ch])
> > > --
> > > 2.36.0.550.gb090851708-goog
> > >