Re: [PATCH] perf build: Fix LTO build of libperf-jvmti.so

[Ian Rogers]

On Wed, Jul 8, 2026 at 5:12 PM Namhyung Kim <namhyung@xxxxxxxxxx> wrote:
>
> Hello,
>
> On Wed, Jul 01, 2026 at 12:21:45AM -0400, Trevor Allison wrote:
> > Linking libperf-jvmti.so through jvmti-in.o (ld -r) breaks LTO when
> > -flto is passed via LDFLAGS.  Link the JVMTI object files directly
> > instead, and pass any LTO flags from LDFLAGS to the JVMTI compile step
>
> Can you share the error message and put it in the commit message?
>
> I think my build is fine with LDFLAGS=-flto.

I had to do many manual steps to make LTO work in the past (IIRC,
using clang and lld). We do have an LTO option in the Makefiles:
https://web.git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/Makefile.config?h=perf-tools-next#n266

If LTO is ready, maybe we can add it to the build tests:
https://web.git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/tests/make?h=perf-tools-next

Thanks,
Ian

> Thanks,
> Namhyung
>
> >
> > Signed-off-by: Trevor Allison <tallison@xxxxxxxxxx>
> > ---
> >  tools/perf/Makefile.perf | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
> > index 3f0544d37a7f..bc66d711fa39 100644
> > --- a/tools/perf/Makefile.perf
> > +++ b/tools/perf/Makefile.perf
> > @@ -686,10 +686,12 @@ ifndef NO_JVMTI
> >  LIBJVMTI_IN := $(OUTPUT)jvmti/jvmti-in.o
> >
> >  $(LIBJVMTI_IN): prepare FORCE
> > -     $(Q)$(MAKE) -f $(srctree)/tools/build/Makefile.build dir=jvmti obj=jvmti
> > +     $(Q)$(MAKE) -f $(srctree)/tools/build/Makefile.build dir=jvmti obj=jvmti \
> > +             CFLAGS="$(CFLAGS) $(filter -flto% -ffat-lto-objects,$(LDFLAGS))"
> >
> >  $(OUTPUT)$(LIBJVMTI): $(LIBJVMTI_IN)
> > -     $(QUIET_LINK)$(CC) $(LDFLAGS) -shared -Wl,-soname -Wl,$(LIBJVMTI) -o $@ $<
> > +     $(QUIET_LINK)$(CC) $(LDFLAGS) -shared -Wl,-soname -Wl,$(LIBJVMTI) -o $@ \
> > +             $(addprefix $(OUTPUT)jvmti/,libjvmti.o jvmti_agent.o libstring.o libctype.o)
> >  endif
> >
> >  $(patsubst perf-%,%.o,$(PROGRAMS)): $(wildcard */*.h)
> > --
> > 2.50.1 (Apple Git-155)
> >