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Add a KASLR howto. Not much to say, but it needs to be officially said
somewhere. I'll perhaps add a nude or two to enlighten if there is some
confusion.

[[!meta title="Using KASLR"]]

NetBSD supports Kernel ASLR on x86 64bit CPUs (amd64), starting from
NetBSD 9.0.

Installation
------------

Install the prekern:

[[!template id=programlisting text="""
# cp /usr/mdec/prekern /
"""]]

Obtain a GENERIC_KASLR kernel. Such a kernel can be either downloaded from
the NetBSD FTP server, for example on:

[[!template id=programlisting text="""
http://nycdn.netbsd.org/pub/NetBSD-daily/HEAD/201808020450Z/amd64/binary/kernel/netbsd-GENERIC_KASLR.gz
"""]]

Or compiled from scratch, using:

[[!template id=programlisting text="""
# cd /usr/src
# ./build.sh kernel=GENERIC_KASLR
"""]]

Install this KASLR kernel:

[[!template id=programlisting text="""
# cp /path/to/your/kernel /netbsd_kaslr
"""]]

Finally, add the following line in the `/boot.cfg` file:

[[!template id=filecontent name="/boot.cfg" text="""
menu=Boot KASLR:rndseed /var/db/entropy-file;pkboot netbsd_kaslr
"""]]

Now the installation is complete.

Use
---

To use KASLR, just choose the "Boot KASLR" option in the menu at boot
time. That's it!

Technical Resources
-------------------

* NetBSD.org: [Kernel ASLR on amd64](http://blog.netbsd.org/tnf/entry/kernel_aslr_on_amd64)
* NetBSD.org: [The strongest KASLR, ever?](http://blog.netbsd.org/tnf/entry/the_strongest_kaslr_ever)