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

Arnaldo Carvalho de Melo
2019-05-22T16:07:04Z

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?

- 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