linux-kernel - Re: [PATCH 04/14] perf map: Add map__objdump

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Message-ID: <CAM9d7chvEw6r8_7agxOpWxufTo+dLaNForSFFShCFGd9KDBtoA@mail.gmail.com>
Date: Tue, 6 Feb 2024 15:04:37 -0800
From: Namhyung Kim <namhyung@...nel.org>
To: Ian Rogers <irogers@...gle.com>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>, Jiri Olsa <jolsa@...nel.org>, 
	Adrian Hunter <adrian.hunter@...el.com>, Peter Zijlstra <peterz@...radead.org>, 
	Ingo Molnar <mingo@...nel.org>, LKML <linux-kernel@...r.kernel.org>, 
	linux-perf-users@...r.kernel.org, 
	Linus Torvalds <torvalds@...ux-foundation.org>, Stephane Eranian <eranian@...gle.com>, 
	Masami Hiramatsu <mhiramat@...nel.org>, linux-toolchains@...r.kernel.org, 
	linux-trace-devel@...r.kernel.org
Subject: Re: [PATCH 04/14] perf map: Add map__objdump_2rip()

Hi Ian,

On Fri, Feb 2, 2024 at 5:42 PM Ian Rogers <irogers@...gle.com> wrote:
>
> On Fri, Feb 2, 2024 at 2:05 PM Namhyung Kim <namhyung@...nel.org> wrote:
> >
> > Sometimes we want to convert an address in objdump output to
> > map-relative address to match with a sample data.  Let's add
> > map__objdump_2rip() for that.
>
> Hi Namhyung,
>
> I think the naming can be better here. Aren't the objdump addresses
> DSO relative offsets? Is the relative IP relative to the map or the
> DSO?

AFAIK the objdump addresses are DSO-relative and rip is to map.
They are mostly the same but sometimes different due to kASLR
for the kernel.

>
> > Cc: Adrian Hunter <adrian.hunter@...el.com>
> > Signed-off-by: Namhyung Kim <namhyung@...nel.org>
> > ---
> >  tools/perf/util/map.c | 20 ++++++++++++++++++++
> >  tools/perf/util/map.h |  3 +++
> >  2 files changed, 23 insertions(+)
> >
> > diff --git a/tools/perf/util/map.c b/tools/perf/util/map.c
> > index 54c67cb7ecef..66542864b7b5 100644
> > --- a/tools/perf/util/map.c
> > +++ b/tools/perf/util/map.c
> > @@ -594,6 +594,26 @@ u64 map__objdump_2mem(struct map *map, u64 ip)
> >         return ip + map__reloc(map);
> >  }
> >
> > +u64 map__objdump_2rip(struct map *map, u64 ip)
> > +{
> > +       const struct dso *dso = map__dso(map);
> > +
> > +       if (!dso->adjust_symbols)
> > +               return ip;
> > +
> > +       if (dso->rel)
> > +               return ip + map__pgoff(map);
> > +
> > +       /*
> > +        * kernel modules also have DSO_TYPE_USER in dso->kernel,
> > +        * but all kernel modules are ET_REL, so won't get here.
> > +        */

Hmm.. This comment is not true anymore.  Will remove
in other places too.

Thanks,
Namhyung


> > +       if (dso->kernel == DSO_SPACE__USER)
> > +               return ip - dso->text_offset;
> > +
> > +       return map__map_ip(map, ip + map__reloc(map));
> > +}
> > +
> >  bool map__contains_symbol(const struct map *map, const struct symbol *sym)
> >  {
> >         u64 ip = map__unmap_ip(map, sym->start);
> > diff --git a/tools/perf/util/map.h b/tools/perf/util/map.h
> > index 49756716cb13..65e2609fa1b1 100644
> > --- a/tools/perf/util/map.h
> > +++ b/tools/perf/util/map.h
> > @@ -132,6 +132,9 @@ u64 map__rip_2objdump(struct map *map, u64 rip);
> >  /* objdump address -> memory address */
> >  u64 map__objdump_2mem(struct map *map, u64 ip);
> >
> > +/* objdump address -> rip */
> > +u64 map__objdump_2rip(struct map *map, u64 ip);
> > +
> >  struct symbol;
> >  struct thread;
> >
> > --
> > 2.43.0.594.gd9cf4e227d-goog
> >