retrieves the context used for creating a new kernel keyring.
This returned context should be freed with freecon if non-NULL.
getkeycreatecon sets *con to NULL if no keycreate context has been explicitly
set by the program (i.e. using the default policy behavior).
sets the context used for creating a new kernel keyring.
NULL can be passed to
setkeycreatecon to reset to the default policy behavior.
The keycreate context is automatically reset after the next execve, so a
program doesn't need to explicitly sanitize it upon startup.
setkeycreatecon can be applied prior to library
functions that internally perform an file creation,
in order to set an file context on the objects.
Note: Signal handlers that perform an setkeycreate must take care to
save, reset, and restore the keycreate context to avoid unexpected behavior.
On error -1 is returned.
On success 0 is returned.