Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755487AbaJNTDJ (ORCPT ); Tue, 14 Oct 2014 15:03:09 -0400 Received: from mail-oi0-f49.google.com ([209.85.218.49]:50208 "EHLO mail-oi0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755357AbaJNTDF (ORCPT ); Tue, 14 Oct 2014 15:03:05 -0400 MIME-Version: 1.0 In-Reply-To: <20141014185829.GA3839@redhat.com> References: <20141006083532.GA4850@quad> <8761fwh1nc.fsf@sejong.aot.lge.com> <20141007140050.GB2256@redhat.com> <20141007151035.GC2256@redhat.com> <20141014185829.GA3839@redhat.com> Date: Tue, 14 Oct 2014 21:03:02 +0200 Message-ID: Subject: Re: [PATCH v2] perf tools: fix off-by-one error in maps From: Stephane Eranian To: Arnaldo Carvalho de Melo Cc: Namhyung Kim , LKML , Jiri Olsa , Peter Zijlstra , Ingo Molnar , David Ahern , Arnaldo Carvalho de Melo Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 14, 2014 at 8:58 PM, Arnaldo Carvalho de Melo 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 >> 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). -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/