ktr port from FreeBSD

[Matthew Dillon]

:I have ported ktr (kernel trace routines) from FreeBSD (who took it from
:BSD/OS).
:I will commit it in some days if there are no major issues with it.
:
:FreeBSD also have a ktrdump util which I will commit later.
:
:http://eirikn.kerneled.org/dragonfly/ktr-dfly.patch
:
:-- 
:Eirik Nygaard
:eirikn at xxxxxxxxxxxx

    I don't know about this.  It (the FreeBSD code) looks poorly designed
    to me.

    Also, the FreeBSD code probably used mutexes where you are using a token.
    For ktr_tracepoint() to be callable from 'anywhere' you can't use a token
    there but must instead convert the code to use a critical section and
    per-cpu arrays.

    Also, 1024 entries is probably not nearly enough for a tracepoint 
    utility to be useful.  We'd need a lot of entries... a million or more,
    for it to be really useful, which implies dynamically allocating the 
    array at boot time rather then declaring it static.

					-Matt
					Matthew Dillon 
					<dillon at xxxxxxxxxxxxx>