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

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Date: Wed, 7 Feb 2024 11:56:13 -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 Wed, Feb 7, 2024 at 11:04 AM Namhyung Kim <namhyung@...nel.org> wrote:
>
> On Tue, Feb 6, 2024 at 3:34 PM Ian Rogers <irogers@...gle.com> wrote:
> >
> > 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?
>
> I'm not sure about the vDSO case.
>
> By the way, I need to take a look if we can make this objdump-rip
> thing simpler as you mentioned.  My feeling is that it can be done
> but I'd like to do it in a separate work and to move this forward.

Makes sense. Could we add a comment to the header file definition to
capture some of this? Perhaps a "to be removed" to avoid later patches
adding dependencies to the function.

Thanks,
Ian

> Thanks,
> Namhyung