linux-kernel - Re: [PATCH 4/6] BC: user interface (syscalls)

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Date:	Thu, 24 Aug 2006 12:04:16 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Andrew Morton <akpm@...l.org>
Cc:	Kirill Korotaev <dev@...ru>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Christoph Hellwig <hch@...radead.org>,
	Pavel Emelianov <xemul@...nvz.org>,
	Andrey Savochkin <saw@...ru>, devel@...nvz.org,
	Rik van Riel <riel@...hat.com>, Andi Kleen <ak@...e.de>,
	Greg KH <greg@...ah.com>, Oleg Nesterov <oleg@...sign.ru>,
	Matt Helsley <matthltc@...ibm.com>,
	Rohit Seth <rohitseth@...gle.com>,
	Chandra Seetharaman <sekharan@...ibm.com>
Subject: Re: [PATCH 4/6] BC: user interface (syscalls)

Ar Mer, 2006-08-23 am 21:35 -0700, ysgrifennodd Andrew Morton:
> > Its a uid_t because of setluid() and twenty odd years of existing unix
> > practice. 
> > 
> 
> I don't understand.  This number is an identifier for an accounting
> container, which was somehow dreamed up by userspace.

Which happens to be a uid_t. It could easily be anyother_t of itself and
you can create a container_id_t or whatever. It is just a number. 

The ancient Unix implementations of this kind of resource management and
security are built around setluid() which sets a uid value that cannot
be changed again and is normally used for security purposes. That
happened to be a uid_t and in simple setups at login uid = luid = euid
would be the norm.

Thus the Linux one happens to be a uid_t. It could be something else but
for the "container per user" model whatever a container is must be able
to hold all possible uid_t values. So we can certainly do something like

typedef uid_t	container_id_t;

Alan

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