copyin
chris at mimsy.UUCP
chris at mimsy.UUCP
Thu Mar 12 18:52:13 AEST 1987
In article <157 at twg-ap.UUCP> narayan at 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 at mimsy.umd.edu
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