Re: [PATCH 1/2] tools/build: Add a feature test for libopenssl

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

On Wed, Dec 03, 2025 at 04:34:56PM -0800, Ian Rogers wrote:
> On Wed, Dec 3, 2025 at 3:29 PM Namhyung Kim <namhyung@kernel.org> wrote:
> >
> > It's used by bpftool and the kernel build.  Let's add a feature test so
> > that perf can decide what to do based on the availability.
> 
> It seems strange to add a feature test that bpftool is missing and
> then use it only in the perf build. The signing of bpf programs isn't

It is strange indeed, I agree that since we don't use BPF signing at
this point in the perf BPf skels, then we could just bootstrap a bpftool
without such feature and continue building the existing features.

Adding the bpftool maintainer to the CC list, Quentin?

- Arnaldo

> something I think we need for skeleton support in perf. I like the
> feature test, could we add it and use it in bpftool? The only two
> functions using openssl appear to be:
> 
>   __u32 register_session_key(const char *key_der_path)
>   int bpftool_prog_sign(struct bpf_load_and_run_opts *opts)
> 
> so we can do the whole feature test then #ifdef HAVE_FEATURE... stub
> static inline versions of the functions game?
> 
> Perhaps we only need the bootstrap version of bpftool in perf and we
> can just avoid dependencies that way. Looking at bpftool's build I see
> that sign.o/c with those functions in is part of the bootstrap version
> of bpftool :-(
> 
> Thanks,
> Ian
> 
> > Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> > ---
> >  tools/build/Makefile.feature          | 6 ++++--
> >  tools/build/feature/Makefile          | 8 ++++++--
> >  tools/build/feature/test-all.c        | 5 +++++
> >  tools/build/feature/test-libopenssl.c | 7 +++++++
> >  4 files changed, 22 insertions(+), 4 deletions(-)
> >  create mode 100644 tools/build/feature/test-libopenssl.c
> >
> > diff --git a/tools/build/Makefile.feature b/tools/build/Makefile.feature
> > index fc6abe369f7373c5..bc6d85bad379321b 100644
> > --- a/tools/build/Makefile.feature
> > +++ b/tools/build/Makefile.feature
> > @@ -99,7 +99,8 @@ FEATURE_TESTS_BASIC :=                  \
> >          libzstd                                \
> >          disassembler-four-args         \
> >          disassembler-init-styled       \
> > -        file-handle
> > +        file-handle                    \
> > +        libopenssl
> >
> >  # FEATURE_TESTS_BASIC + FEATURE_TESTS_EXTRA is the complete list
> >  # of all feature tests
> > @@ -147,7 +148,8 @@ FEATURE_DISPLAY ?=              \
> >           lzma                   \
> >           bpf                   \
> >           libaio                        \
> > -         libzstd
> > +         libzstd               \
> > +         libopenssl
> >
> >  #
> >  # Declare group members of a feature to display the logical OR of the detection
> > diff --git a/tools/build/feature/Makefile b/tools/build/feature/Makefile
> > index 7c90e0d0157ac9b1..3fd5ad0db2109778 100644
> > --- a/tools/build/feature/Makefile
> > +++ b/tools/build/feature/Makefile
> > @@ -67,12 +67,13 @@ FILES=                                          \
> >           test-libopencsd.bin                   \
> >           test-clang.bin                                \
> >           test-llvm.bin                         \
> > -         test-llvm-perf.bin   \
> > +         test-llvm-perf.bin                    \
> >           test-libaio.bin                       \
> >           test-libzstd.bin                      \
> >           test-clang-bpf-co-re.bin              \
> >           test-file-handle.bin                  \
> > -         test-libpfm4.bin
> > +         test-libpfm4.bin                      \
> > +         test-libopenssl.bin
> >
> >  FILES := $(addprefix $(OUTPUT),$(FILES))
> >
> > @@ -381,6 +382,9 @@ endif
> >  $(OUTPUT)test-libpfm4.bin:
> >         $(BUILD) -lpfm
> >
> > +$(OUTPUT)test-libopenssl.bin:
> > +       $(BUILD) -lssl
> > +
> >  $(OUTPUT)test-bpftool-skeletons.bin:
> >         $(SYSTEM_BPFTOOL) version | grep '^features:.*skeletons' \
> >                 > $(@:.bin=.make.output) 2>&1
> > diff --git a/tools/build/feature/test-all.c b/tools/build/feature/test-all.c
> > index eb346160d0ba0e2f..1488bf6e607836e5 100644
> > --- a/tools/build/feature/test-all.c
> > +++ b/tools/build/feature/test-all.c
> > @@ -142,6 +142,10 @@
> >  # include "test-libtraceevent.c"
> >  #undef main
> >
> > +#define main main_test_libopenssl
> > +# include "test-libopenssl.c"
> > +#undef main
> > +
> >  int main(int argc, char *argv[])
> >  {
> >         main_test_libpython();
> > @@ -173,6 +177,7 @@ int main(int argc, char *argv[])
> >         main_test_reallocarray();
> >         main_test_libzstd();
> >         main_test_libtraceevent();
> > +       main_test_libopenssl();
> >
> >         return 0;
> >  }
> > diff --git a/tools/build/feature/test-libopenssl.c b/tools/build/feature/test-libopenssl.c
> > new file mode 100644
> > index 0000000000000000..168c45894e8be687
> > --- /dev/null
> > +++ b/tools/build/feature/test-libopenssl.c
> > @@ -0,0 +1,7 @@
> > +#include <openssl/ssl.h>
> > +#include <openssl/opensslv.h>
> > +
> > +int main(void)
> > +{
> > +       return SSL_library_init();
> > +}
> > --
> > 2.52.0.177.g9f829587af-goog
> >