2.6 Series Mem Mgmt

Chris Bookholt
2005-01-17T19:37:58Z

I'm hoping someone can help explain part of the layout of a process'
virtual address space in the 2.6 series kernel.

Below is the output of "cat /proc/self/maps" on Fedora Core 3
(2.6.9-1.6_FC2) with exec-shield[-randomize] disabled and
legacy_vm_layout enabled.

What is being mapped in at last line (ffffe000-fffff000 ---p)? This is
always there, no matter what process I run. To my knowledge, this
wasn't the case on 2.4.

>$ cat /proc/self/maps
08048000-0804c000 r-xp 00000000 03:03 2490451 /bin/cat
0804c000-0804d000 rw-p 00003000 03:03 2490451 /bin/cat
0804d000-0806e000 rw-p 0804d000 00:00 0
42344000-42359000 r-xp 00000000 03:03 950351 /lib/ld-2.3.3.so
42359000-4235a000 r--p 00014000 03:03 950351 /lib/ld-2.3.3.so
4235a000-4235b000 rw-p 00015000 03:03 950351 /lib/ld-2.3.3.so
4235d000-42473000 r-xp 00000000 03:03 950450 /lib/tls/libc-2.3.3.so
42473000-42474000 r--p 00116000 03:03 950450 /lib/tls/libc-2.3.3.so
42474000-42477000 rw-p 00117000 03:03 950450 /lib/tls/libc-2.3.3.so
42477000-42479000 rw-p 42477000 00:00 0
55017000-55018000 rw-p 55017000 00:00 0
55018000-55218000 r--p 00000000 03:03 114690
/usr/lib/locale/locale-archive
feffe000-ff000000 rw-p feffe000 00:00 0
ffffe000-fffff000 ---p 00000000 00:00 0

I have not had much success in my search for information via Google &
IRC and the books I have are specific to the 2.4 series. Any help would
be greatly appreciated.

-Chris