linux-kernel - Re: [PATCH 4/5] perf tools: Use machine->root

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Message-ID: <aS9ZfAd3CDh5wboJ@google.com>
Date: Tue, 2 Dec 2025 13:26:20 -0800
From: Namhyung Kim <namhyung@...nel.org>
To: Ian Rogers <irogers@...gle.com>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>,
	James Clark <james.clark@...aro.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
Subject: Re: [PATCH 4/5] perf tools: Use machine->root_dir to find
 /proc/kallsyms

On Tue, Dec 02, 2025 at 12:53:48PM -0800, Ian Rogers wrote:
> On Tue, Dec 2, 2025 at 12:16 AM Namhyung Kim <namhyung@...nel.org> wrote:
> >
> > This is for test functions to find the kallsyms correctly.  It can find
> > the machine from the kernel maps and use its root_dir.  This is helpful
> > to setup fake /proc directory for testing.
> >
> > Signed-off-by: Namhyung Kim <namhyung@...nel.org>
> > ---
> >  tools/perf/util/symbol.c | 8 +++++++-
> >  1 file changed, 7 insertions(+), 1 deletion(-)
> >
> > diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
> > index b533fbf17a8b19a3..e90ecfd286043aa4 100644
> > --- a/tools/perf/util/symbol.c
> > +++ b/tools/perf/util/symbol.c
> > @@ -2002,6 +2002,7 @@ static char *dso__find_kallsyms(struct dso *dso, struct map *map)
> >         char sbuild_id[SBUILD_ID_SIZE];
> >         bool is_host = false;
> >         char path[PATH_MAX];
> > +       struct kmap *kmap = map__kmap(map);
> 
> Reviewed-by: Ian Rogers <irogers@...gle.com>
> 
> nit: perhaps just use map__kmaps here to avoid testing two values below.

Right, will update.  Thanks for your review!
Namhyung
 
> >
> >         if (!dso__has_build_id(dso)) {
> >                 /*
> > @@ -2038,8 +2039,13 @@ static char *dso__find_kallsyms(struct dso *dso, struct map *map)
> >                 return strdup(path);
> >
> >         /* Use current /proc/kallsyms if possible */
> > -       if (is_host) {
> >  proc_kallsyms:
> > +       if (kmap && kmap->kmaps) {
> > +               struct machine *machine = maps__machine(kmap->kmaps);
> > +
> > +               scnprintf(path, sizeof(path), "%s/proc/kallsyms", machine->root_dir);
> > +               return strdup(path);
> > +       } else if (is_host) {
> >                 return strdup("/proc/kallsyms");
> >         }
> >
> > --
> > 2.52.0.158.g65b55ccf14-goog
> >