linux-kernel - Query about process address space

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Date:	Wed, 7 Oct 2009 15:10:33 -0400
From:	Hayawardh V <hayawardh@...il.com>
To:	linux-kernel@...r.kernel.org
Cc:	Ashwin Chaugule <ashwin.chaugule@...il.com>
Subject: Query about process address space

Hi,

generally the text segment of the program gets mapped into the virtual
address starting at
0x8048000 ....

but in the case of certain programs like sshd, apache, postgres, when
I examine the proc/pid/maps, I get that the program is mapped higher
in memory (ie) in the mmap space.
eg: cat /proc/sshd/maps

...
b7fd2000-b7fd3000 r--p 0001a000 08:01 5144607    /lib/ld-2.8.90.so
b7fd3000-b7fd4000 rw-p 0001b000 08:01 5144607    /lib/ld-2.8.90.so
b7fd4000-b8038000 r-xp 00000000 08:01 656219     /usr/sbin/sshd
b8039000-b803a000 r--p 00064000 08:01 656219     /usr/sbin/sshd
b803a000-b803b000 rw-p 00065000 08:01 656219     /usr/sbin/sshd
b803b000-b8040000 rw-p 00000000 00:00 0
b8779000-b87be000 rw-p 00000000 00:00 0          [heap]
bfeed000-bff02000 rw-p 00000000 00:00 0          [stack]

(on linux-2.6.30)

This seems to be the mmap space. Why do programs mmap themselves in
higher memory? Or is there some other reason and is this not the mmap space?

Thanks,
Hayawardh
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