🚀 go-pugleaf

> Excerpts from netnews.comp.os.mach: 18-Mar-91 Re: message passing &
> migra.. Michael I Bushnell@geech (3703)

>    c.  Could somebody clarify when I can/should/must use out-of-line
> data as
>    opposed to in-line data?  Out-of-line data is useful for
> scatter/gather, but
>    does it have to be used for "large" amounts of data, and is
> out-of-line
>    data always sent copy-on-write (intramachine), and therefore must be
>    page-aligned?  What, in practice, do programmers (mostly) do?

> You can use it whenever you want.  If it isn't page aligned, or an
> integral number of pages, then the receiver will be able to read some
> data before/after the data you intended to send, but other than that
> it works correctly. 

According to the interface spec, the receiver should not be able to read
data that you did not intend to send.  If out-of-line data isn't page
aligned or an integral number of pages, then the excess data should show
up zeroed.  Michael is correct in that the correct VM copy-on-write code
does not zero, but this is a bug.

Rich