linux-kernel - Re: [PATCH v2] perf tools: fix off-by-one error in maps

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Message-ID: <20141007135838.5e3e364c@as>
Date:	Tue, 7 Oct 2014 13:58:38 -0500
From:	Chuck Ebbert <cebbert.lkml@...il.com>
To:	Arnaldo Carvalho de Melo <acme@...hat.com>
Cc:	Namhyung Kim <namhyung@...nel.org>,
	Stephane Eranian <eranian@...gle.com>,
	linux-kernel@...r.kernel.org, jolsa@...hat.com,
	peterz@...radead.org, mingo@...e.hu, dsahern@...il.com
Subject: Re: [PATCH v2] perf tools: fix off-by-one error in maps

On Tue, 7 Oct 2014 11:00:50 -0300
Arnaldo Carvalho de Melo <acme@...hat.com> wrote:

> 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.
> 
> Etc.
> 

But the convention used in the memory management code is that "end" is
the next byte after the memory region. This gives you:

  size = end - start
  end = start + size

Using a different convention here will just confuse people used to the
way it's done everywhere else.
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