Re: [PATCH 08/12] perf tools: Preserve eBPF maps when loading kcore

Jiri Olsa
2019-05-22T21:23:05Z

On Wed, May 22, 2019 at 01:06:57PM -0300, Arnaldo Carvalho de Melo wrote:
> Em Wed, May 08, 2019 at 03:20:06PM +0200, Jiri Olsa escreveu:
> > We need to preserve eBPF maps even if they are
> > covered by kcore, because we need to access
> > eBPF dso for source data.
>
> So, I reordered this one with the previous, as to get the output you
> added to 07/12 we need what is in 08/12, and they are otherwise
> completely independent, right?

right

jirka

>
> - Arnaldo
>
> > Adding map_groups__merge_in function to do that.
> > It merges map into map_groups by splitting the
> > new map within the existing map regions.
> >
> > Suggested-by: Adrian Hunter <adrian.hunter@intel.com>
> > Link: http://lkml.kernel.org/n/tip-mlu13e9zl6rbsz4fa00x7mfa@git.kernel.org
> > Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> > ---
> > tools/perf/util/symbol.c | 97 ++++++++++++++++++++++++++++++++++++++--
> > 1 file changed, 93 insertions(+), 4 deletions(-)
> >
> > diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
> > index 5cbad55cd99d..29780fcd049c 100644
> > --- a/tools/perf/util/symbol.c
> > +++ b/tools/perf/util/symbol.c
> > @@ -1166,6 +1166,85 @@ static int kcore_mapfn(u64 start, u64 len, u64 pgoff, void *data)
> > return 0;
> > }
> >
> > +/*
> > + * Merges map into map_groups by splitting the new map
> > + * within the existing map regions.
> > + */
> > +static int map_groups__merge_in(struct map_groups *kmaps, struct map *new_map)
> > +{
> > + struct map *old_map;
> > + LIST_HEAD(merged);
> > +
> > + for (old_map = map_groups__first(kmaps); old_map;
> > + old_map = map_groups__next(old_map)) {
> > +
> > + /* no overload with this one */
> > + if (new_map->end < old_map->start ||
> > + new_map->start >= old_map->end)
> > + continue;
> > +
> > + if (new_map->start < old_map->start) {
> > + /*
> > + * |new......
> > + * |old....
> > + */
> > + if (new_map->end < old_map->end) {
> > + /*
> > + * |new......| -> |new..|
> > + * |old....| -> |old....|
> > + */
> > + new_map->end = old_map->start;
> > + } else {
> > + /*
> > + * |new.............| -> |new..| |new..|
> > + * |old....| -> |old....|
> > + */
> > + struct map *m = map__clone(new_map);
> > +
> > + if (!m)
> > + return -ENOMEM;
> > +
> > + m->end = old_map->start;
> > + list_add_tail(&m->node, &merged);
> > + new_map->start = old_map->end;
> > + }
> > + } else {
> > + /*
> > + * |new......
> > + * |old....
> > + */
> > + if (new_map->end < old_map->end) {
> > + /*
> > + * |new..| -> x
> > + * |old.........| -> |old.........|
> > + */
> > + map__put(new_map);
> > + new_map = NULL;
> > + break;
> > + } else {
> > + /*
> > + * |new......| -> |new...|
> > + * |old....| -> |old....|
> > + */
> > + new_map->start = old_map->end;
> > + }
> > + }
> > + }
> > +
> > + while (!list_empty(&merged)) {
> > + old_map = list_entry(merged.next, struct map, node);
> > + list_del_init(&old_map->node);
> > + map_groups__insert(kmaps, old_map);
> > + map__put(old_map);
> > + }
> > +
> > + if (new_map) {
> > + map_groups__insert(kmaps, new_map);
> > + map__put(new_map);
> > + }
> > + return 0;
> > +}
> > +
> > static int dso__load_kcore(struct dso *dso, struct map *map,
> > const char *kallsyms_filename)
> > {
> > @@ -1222,7 +1301,12 @@ static int dso__load_kcore(struct dso *dso, struct map *map,
> > while (old_map) {
> > struct map *next = map_groups__next(old_map);
> >
> > - if (old_map != map)
> > + /*
> > + * We need to preserve eBPF maps even if they are
> > + * covered by kcore, because we need to access
> > + * eBPF dso for source data.
> > + */
> > + if (old_map != map && !__map__is_bpf_prog(old_map))
> > map_groups__remove(kmaps, old_map);
> > old_map = next;
> > }
> > @@ -1256,11 +1340,16 @@ static int dso__load_kcore(struct dso *dso, struct map *map,
> > map_groups__remove(kmaps, map);
> > map_groups__insert(kmaps, map);
> > map__put(map);
> > + map__put(new_map);
> > } else {
> > - map_groups__insert(kmaps, new_map);
> > + /*
> > + * Merge kcore map into existing maps,
> > + * and ensure that current maps (eBPF)
> > + * stay intact.
> > + */
> > + if (map_groups__merge_in(kmaps, new_map))
> > + goto out_err;
> > }
> > -
> > - map__put(new_map);
> > }
> >
> > if (machine__is(machine, "x86_64")) {
> > --
> > 2.20.1
>
> --
>
> - Arnaldo