Messages in this thread | | | Date | Tue, 14 Oct 2014 21:03:02 +0200 | Subject | Re: [PATCH v2] perf tools: fix off-by-one error in maps | From | Stephane Eranian <> |
| |
On Tue, Oct 14, 2014 at 8:58 PM, Arnaldo Carvalho de Melo <acme@redhat.com> wrote: > Em Tue, Oct 07, 2014 at 05:17:12PM +0200, Stephane Eranian escreveu: >> On Tue, Oct 7, 2014 at 5:10 PM, Arnaldo Carvalho de Melo >> <acme@redhat.com> wrote: >> > Em Tue, Oct 07, 2014 at 04:17:41PM +0200, Stephane Eranian escreveu: >> >> On Tue, Oct 7, 2014 at 4:00 PM, Arnaldo Carvalho de Melo >> >> >> +++ b/tools/perf/util/map.c >> >> >> @@ -752,7 +752,7 @@ struct map *maps__find(struct rb_root *maps, u64 ip) >> >> >> m = rb_entry(parent, struct map, rb_node); >> >> >> if (ip < m->start) >> >> >> p = &(*p)->rb_left; >> >> >> - else if (ip > m->end) >> >> >> + else if (ip >= m->end) >> >> >> p = &(*p)->rb_right; >> >> >> else >> >> >> return m; > >> >> > I keep thinking that this change is making things unclear. > >> >> > I.e. the _start_ of a map (map->start) is _in_ the map, and the _end_ >> >> > of a map (map->end) is _in_ the map as well. > >> >> > if (addr > m->end) > >> >> > is shorter than: > >> >> > if (addr >= m->end) > >> >> > "start" and "end" should have the same rule applied, i.e. if one is in, >> >> > the other is in as well. > >> >> It is okay but then we need to be consistent all across. This is not >> >> the case today. >> >> I mentioned the cases I ran into. > >> > Ok, and provided a patch doing the way I thought was confusing, now its >> > my turn to use that info and come up with a patch, ok, will do that. > >> You got it! ;-> > > struct vm_area_struct { > /* The first cache line has the info for VMA tree walking. */ > > unsigned long vm_start; /* Our start address within vm_mm. */ > unsigned long vm_end; /* The first byte after our end address > within vm_mm. */ > > So these guys have been doing this far longer than me, I guess I'll bow > to this convention. > > But by renaming map->end to map->end_ and looking at all the usage of > it, there are some inconsistencies... > > Like symbol->{start,end} is of the [start,end] case, and to be > consistent with above needs to also move to [start,end[, will cook a > patch and send for review. > Yes, there were some inconsistencies (or confusions) that I noticed when I started fixing the maps. I can believe that this off-by-one error exist with other data types. That could cause wrong symbol correlations in borderline cases (which are really rare).
| |