On Tue, 8 Apr 2008, Peter Kerpedjiev wrote:
> Robert P. J. Day wrote:
> > # pmap -d 1
> > 1: init [5]
> > Address Kbytes Mode Offset Device Mapping
> > ... snip ...
> > 00c55000 12 r-x-- 0000000000000000 0fd:00000 libdl-2.7.so
> > 00c58000 4 r-x-- 0000000000002000 0fd:00000 libdl-2.7.so
> > 00c59000 4 rwx-- 0000000000003000 0fd:00000 libdl-2.7.so
> > ...
> >
> > if you look at the second VMA for that shared lib, its address shows
> > that it's 0x3000 higher up in memory, but the Offset field shows an
> > offset of only 0x2000. what does that mean? thanks.
> >
> >
> AFAICT, the region from offset 2000 to offset 3000 in libdl-2.7.so
> is mapped by both of the first two memory areas.
>
> I'm not sure why two memory regions would map the same part of a
> file with the same permissions.
that's what was confusing me, since i read in love's book, p. 256:
"Intervals in different memory areas in the same address space cannot
overlap."
and that sure looks like overlapping to me, but only if you take the
"offset" field seriously.
rday
--
========================================================================
Robert P. J. Day
Linux Consulting, Training and Annoying Kernel Pedantry:
Have classroom, will lecture.
http://crashcourse.ca Waterloo, Ontario, CANADA
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