On Fri, Jun 23, 2017 at 10:55:47AM -0300, Arnaldo Carvalho de Melo wrote:
> Em Fri, Jun 23, 2017 at 02:48:24PM +0900, Namhyung Kim escreveu:
> > Even every module has loaded onto same addresses, some modules can be
> > changed and reloaded.
>
> Can you rephrase the above statement?
>
> You mean even if a module is reloaded at the same address it can have a
> different symtab and thus misresolve symbols if we get a sample for one
> module version and try to resolve symbols using a symtab for another
> module version?
Right, as I said in other thread, the module can be unloaded, modified
and reloaded between "perf record" and "perf report".
>
> > In that case it needs to access to the old module
> > in the build-id cache.
>
> Right, we need to make sure that during a 'perf record' session a módule
> isn't reloaded, because at 'perf record' exit we will record that module
> build-id in a perf.data header and grab a copy (or a hardlink, if
> possible) into the ~/.debug build-id cache, then, at 'perf report' time
> we will read that build-id perf.data table and lookup in the build-id
> cache to get the matching symtab (and full elf .ko file to do things
> like annotation).
That's the desired behavior. But "perf report" didn't use modules in
the build-id cache when it used kcore (and kallsyms).
Thanks,
Namhyung
>
> > Cc: Adrian Hunter <adrian.hun...@intel.com>
> > Cc: Wang Nan <wangn...@huawei.com>
> > Signed-off-by: Namhyung Kim <namhy...@kernel.org>
> > ---
> > tools/perf/util/symbol.c | 45 +++++++++++++++++++++++----------------------
> > 1 file changed, 23 insertions(+), 22 deletions(-)
> >
> > diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
> > index ce79a51f25bf..fe46eb782297 100644
> > --- a/tools/perf/util/symbol.c
> > +++ b/tools/perf/util/symbol.c
> > @@ -1155,6 +1155,7 @@ static int dso__load_kcore(struct dso *dso, struct
> > map *map,
> > int err, fd;
> > char kcore_filename[PATH_MAX];
> > struct symbol *sym;
> > + struct map_groups old_mg;
> >
> > if (!kmaps)
> > return -EINVAL;
> > @@ -1196,15 +1197,8 @@ static int dso__load_kcore(struct dso *dso, struct
> > map *map,
> > goto out_err;
> > }
> >
> > - /* Remove old maps */
> > - old_map = map_groups__first(kmaps, map->type);
> > - while (old_map) {
> > - struct map *next = map_groups__next(old_map);
> > -
> > - if (old_map != map)
> > - map_groups__remove(kmaps, old_map);
> > - old_map = next;
> > - }
> > + old_mg = *kmaps;
> > + kmaps->maps[map->type].entries = RB_ROOT;
> >
> > /* Find the kernel map using the first symbol */
> > sym = dso__first_symbol(dso, map->type);
> > @@ -1223,24 +1217,31 @@ static int dso__load_kcore(struct dso *dso, struct
> > map *map,
> > while (!list_empty(&md.maps)) {
> > new_map = list_entry(md.maps.next, struct map, node);
> > list_del_init(&new_map->node);
> > - if (new_map == replacement_map) {
> > - map->start = new_map->start;
> > - map->end = new_map->end;
> > - map->pgoff = new_map->pgoff;
> > - map->map_ip = new_map->map_ip;
> > - map->unmap_ip = new_map->unmap_ip;
> > - /* Ensure maps are correctly ordered */
> > - map__get(map);
> > - map_groups__remove(kmaps, map);
> > - map_groups__insert(kmaps, map);
> > - map__put(map);
> > - } else {
> > - map_groups__insert(kmaps, new_map);
> > +
> > + map_groups__insert(kmaps, new_map);
> > +
> > + if (new_map != replacement_map) {
> > + old_map = map_groups__find(&old_mg, new_map->type,
> > new_map->start);
> > + if (old_map && dso__loaded(old_map->dso,
> > old_map->type)) {
> > + new_map->pgoff = old_map->pgoff;
> > +
> > + dso__put(new_map->dso);
> > + new_map->dso = dso__get(old_map->dso);
> > + }
> > }
> >
> > map__put(new_map);
> > }
> >
> > + /* Remove old maps */
> > + old_map = map_groups__first(&old_mg, map->type);
> > + while (old_map) {
> > + struct map *next = map_groups__next(old_map);
> > +
> > + map_groups__remove(&old_mg, old_map);
> > + old_map = next;
> > + }
> > +
> > /*
> > * Set the data type and long name so that kcore can be read via
> > * dso__data_read_addr().
> > --
> > 2.13.1
