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

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Message-ID: <CAP-5=fWx9Uub9uRgQJq_ekQScm4fJXMdr9_cr19vcckCPjPt9w@mail.gmail.com>
Date: Tue, 6 Feb 2024 15:33:45 -0800
From: Ian Rogers <irogers@...gle.com>
To: Namhyung Kim <namhyung@...nel.org>
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()

On Tue, Feb 6, 2024 at 3:04 PM Namhyung Kim <namhyung@...nel.org> wrote:
>
> 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.

Perhaps we need to use names like map_rip for mapping relative and
dso_rip to clean this up, or to add a different mapping_type to the
enum. For non-kernel maps addresses for map are either the whole
virtual address space (identity) or relative to a dso:
https://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/util/map.h?h=perf-tools-next#n115
https://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/util/map.h?h=perf-tools-next#n20
The dso addresses should work for objdump so perhaps the kernel
addresses need map__pgoff fixing?

Thanks,
Ian

> >
> > > 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
> > >