Where is the JBoss EAP 6 log pattern format documentation? It seems to have some format characters that are different from log4j or logback (such as %K and %s).
A number of searches only turn up results for older jboss versions which don't have the full set of characters.
The FormatStringParser source code is probably the best bet.
Here is a list of the format characters that differ from log4j:
%s the message (like %m) including exception stack traces
%m the message, suppressing exception stack traces
%E exception stack trace
%K adds terminal-based colorization
%k log resource key (for localization)
%z time zone
%P localized log level name
See also RedHat's documentation.