Editing User-mode Linux (section)

== Integration into the Linux kernel ==
The UML guest application (a [[Linux kernel|Linux]] binary [[Executable and Linkable Format|ELF]]) was originally available as a [[patch (computing)|patch]] for some Kernel versions above 2.2.x, and the host with any kernel version above 2.2.x supported it easily in the thread mode (i.e., non-SKAS3).

As of [[Linux kernel|Linux]] 2.6.0, it is integrated into the main [[kernel (operating system)|kernel]] source tree. A method of running a separate kernel address space (SKAS) that does not require host kernel patching has been implemented. This improves performance and security over the old Traced Thread approach, in which processes running in the UML share the same address space from the host's point of view, which leads the memory inside the UML to not be protected by the [[memory management unit]]. Unlike the current UML using SKAS, buggy or malicious software inside a UML running on a non-SKAS host could be able to read the memory space of other UML processes or even the UML kernel memory.<ref>{{Cite book |title=User Mode Linux |last=Dike |first=Jeff |date=2006-04-12 |publisher=[[Prentice Hall]] |isbn=9780131865051 |pages=197}}</ref>