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Path: utzoo!utgpu!water!watnot!watmath!clyde!rutgers!seismo!mimsy!chris
From: chris@mimsy.UUCP
Newsgroups: comp.unix.wizards
Subject: Re: copyin
Message-ID: <5769@mimsy.UUCP>
Date: Thu, 12-Mar-87 03:52:13 EST
Article-I.D.: mimsy.5769
Posted: Thu Mar 12 03:52:13 1987
Date-Received: Fri, 13-Mar-87 04:41:43 EST
References: <4838@brl-adm.ARPA> <157@twg-ap.UUCP>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 22
Summary: uchar is old (and gone from 4.3BSD)

In article <157@twg-ap.UUCP> narayan@twg-ap.UUCP (Narayan Mohanram) writes:
>... if you go to some other machine where it is not possible to
>distinguish between kernel space and user space, ... you may crash
>and burn.

Right.

>You really need to to do a uchar(I think) not a copy in to load the
>string in (after setting u.u_xxx).

No: namei used to call uchar to read from user I or D space, one
byte at a time.  One would set u.u_segflg according to the source
space (user instruction, user data, or system), and namei and a
few other routines would call uchar or schar.  I am not old enough
to be familiar with just which routines were done which way in
which kernels, but in 4.3, the routine to copy strings in is
`copyinstr'.  Incidentally, the 4.3 copy routines have been adapted
to 2.10BSD, speeding it considerably.  A function call per character
for every name lookup is just a bit too much overhead.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7690)
UUCP:	seismo!mimsy!chris	ARPA/CSNet:	chris@mimsy.umd.edu