Re: On PATH_MAX

[Bas Wijnen]

On Tue, Nov 08, 2005 at 11:58:48AM -0500, Jonathan S. Shapiro wrote:
> > There is no transfer of data, there is only transfer of the container
> > capability.  This capability gives access to a set of pages, which can be
> > mapped in or out of the address space when the process likes.
> 
> Operationally this is correct, but the mechanism described is
> unfortunate if your description is intended literally.
> 
> If I hold a capability to a memory object, what I have is the authority
> to map a *window* on each page within that object, subject to the
> permission restrictions of the memory object.
> 
> The difference between mapping such a window and mapping the page
> directly is that the window becomes invalid if the memory object is
> destroyed.
> 
> The distinction is subtle, but important.

That is exactly what I meant.  If this is a (logical or real) copy of the
memory, then the server will have to pay for it.  Since the server is working
on behalf of the client, this is not good.  It is also not needed, as the
client only hurts itself when it destroys the object: all that happens is that
the request is not answered (and likely any state for the client is
discarded), because of contract violation.

Thanks,
Bas

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