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Message-ID: <ZvW3iIhvSesG5_SC@google.com>
Date: Thu, 26 Sep 2024 12:35:36 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: Ian Rogers <irogers@...gle.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...nel.org>,
Adrian Hunter <adrian.hunter@...el.com>,
Kan Liang <kan.liang@...ux.intel.com>,
John Garry <john.g.garry@...cle.com>, Will Deacon <will@...nel.org>,
James Clark <james.clark@...aro.org>,
Mike Leach <mike.leach@...aro.org>, Leo Yan <leo.yan@...ux.dev>,
Guo Ren <guoren@...nel.org>,
Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>,
Albert Ou <aou@...s.berkeley.edu>, Nick Terrell <terrelln@...com>,
Guilherme Amadio <amadio@...too.org>,
Changbin Du <changbin.du@...wei.com>,
"Steinar H. Gunderson" <sesse@...gle.com>,
"Masami Hiramatsu (Google)" <mhiramat@...nel.org>,
Aditya Gupta <adityag@...ux.ibm.com>,
Athira Rajeev <atrajeev@...ux.vnet.ibm.com>,
Masahiro Yamada <masahiroy@...nel.org>,
Huacai Chen <chenhuacai@...nel.org>, Bibo Mao <maobibo@...ngson.cn>,
Kajol Jain <kjain@...ux.ibm.com>, Anup Patel <anup@...infault.org>,
Shenlin Liang <liangshenlin@...incomputing.com>,
Atish Patra <atishp@...osinc.com>,
Oliver Upton <oliver.upton@...ux.dev>,
Chen Pei <cp0613@...ux.alibaba.com>,
Dima Kogan <dima@...retsauce.net>,
Alexander Lobakin <aleksander.lobakin@...el.com>,
"David S. Miller" <davem@...emloft.net>,
Przemek Kitszel <przemyslaw.kitszel@...el.com>,
linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
Yang Jihong <yangjihong@...edance.com>
Subject: Re: [PATCH v1 07/11] perf probe: Move elfutils support check to
libdw check
On Thu, Sep 26, 2024 at 08:08:22AM -0700, Ian Rogers wrote:
> On Wed, Sep 25, 2024 at 5:30 PM Namhyung Kim <namhyung@...nel.org> wrote:
> >
> > On Tue, Sep 24, 2024 at 09:04:14AM -0700, Ian Rogers wrote:
> > > The test _ELFUTILS_PREREQ(0, 142) is false for elfutils before
> > > 2009-06-13, but that is 15 years ago and very unlikely. Add a test to
> > > test-libdw.c and assume the libdw version is at least 0.142 to
> > > simplify the build logic.
> > >
> > > Signed-off-by: Ian Rogers <irogers@...gle.com>
> > > ---
> > > tools/build/feature/test-libdw.c | 10 +++++++++-
> > > tools/perf/util/probe-finder.c | 2 --
> > > tools/perf/util/probe-finder.h | 2 --
> > > 3 files changed, 9 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/tools/build/feature/test-libdw.c b/tools/build/feature/test-libdw.c
> > > index 71c6f8e3b0ee..2fb59479ab77 100644
> > > --- a/tools/build/feature/test-libdw.c
> > > +++ b/tools/build/feature/test-libdw.c
> > > @@ -41,8 +41,16 @@ int test_libdw_getcfi(void)
> > > return dwarf_getcfi(dwarf) == NULL;
> > > }
> > >
> > > +int test_elfutils(void)
> > > +{
> > > + Dwarf_CFI *cfi = NULL;
> > > +
> > > + dwarf_cfi_end(cfi);
> > > + return 0;
> > > +}
> >
> > I think it's the same as test_libdw_getcfi() and let's get rid of it.
>
> The point of doing the change this way, and I think what's being
> ignored, is that I am trying to simply replace an #if with a clearly
> equivalent feature test - clearly equivalent as the #if guards use of
> dwarf_cfi_end in the code. Merging test_elfutils with
> test_libdw_getcfi is another cognitive step and I think it is fine as
> follow up cleanup. Combining that step with the change here fails the
> minimal meaningful change and tbh I think this is just bike shedding.
Ok, I think it's ok to have a separate commit to combine equivalent
tests if you really want to. What I want in the end is not to have
unnecessary or duplicate code.
In order to have a clearly equivalent feature test, I think you can add
#if !_ELFUTILS_PREREQ(0, 142)
#error "elfutils version is too old"
#endif
Thanks,
Namhyung
> >
> > > +
> > > int main(void)
> > > {
> > > return test_libdw() + test_libdw_unwind() + test_libdw_getlocations() +
> > > - test_libdw_getcfi();
> > > + test_libdw_getcfi() + test_elfutils();
> > > }
> > > diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
> > > index 78f34fa0c391..7434b38596b9 100644
> > > --- a/tools/perf/util/probe-finder.c
> > > +++ b/tools/perf/util/probe-finder.c
> > > @@ -1379,10 +1379,8 @@ int debuginfo__find_trace_events(struct debuginfo *dbg,
> > > if (ret >= 0 && tf.pf.skip_empty_arg)
> > > ret = fill_empty_trace_arg(pev, tf.tevs, tf.ntevs);
> > >
> > > -#if _ELFUTILS_PREREQ(0, 142)
> > > dwarf_cfi_end(tf.pf.cfi_eh);
> > > dwarf_cfi_end(tf.pf.cfi_dbg);
> > > -#endif
> > >
> > > if (ret < 0 || tf.ntevs == 0) {
> > > for (i = 0; i < tf.ntevs; i++)
> > > diff --git a/tools/perf/util/probe-finder.h b/tools/perf/util/probe-finder.h
> > > index 3add5ff516e1..f0149d72310c 100644
> > > --- a/tools/perf/util/probe-finder.h
> > > +++ b/tools/perf/util/probe-finder.h
> > > @@ -63,12 +63,10 @@ struct probe_finder {
> > > struct intlist *lcache; /* Line cache for lazy match */
> > >
> > > /* For variable searching */
> > > -#if _ELFUTILS_PREREQ(0, 142)
> > > /* Call Frame Information from .eh_frame */
> > > Dwarf_CFI *cfi_eh;
> > > /* Call Frame Information from .debug_frame */
> > > Dwarf_CFI *cfi_dbg;
> > > -#endif
> > > Dwarf_Op *fb_ops; /* Frame base attribute */
> > > unsigned int machine; /* Target machine arch */
> > > struct perf_probe_arg *pvar; /* Current target variable */
> > > --
> > > 2.46.0.792.g87dc391469-goog
> > >
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