linux-kernel - Re: [PATCH, v3] shmat: introduce flag SHM_MAP_NOT

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Date:	Wed, 8 Oct 2008 09:58:51 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Andi Kleen <andi@...stfloor.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Ingo Molnar <mingo@...hat.com>,
	Arjan van de Ven <arjan@...radead.org>,
	Hugh Dickins <hugh@...itas.com>,
	Ulrich Drepper <drepper@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH, v3] shmat: introduce flag SHM_MAP_NOT_FIXED

> > 	shmat giving an address
> > 	if error
> > 		shmat giving no address
> > 
> > from user space.
> 
> No you can't here because shmat() starts searching from the wrong
> start address.

If you are only hinting a desired address then that by the very meaning
of the word "hint" means you will accept a different one.

> The only way would be to search manually in /proc/self/maps
> and handle the races, but I hope you're not advocating that.

Gak, mmap a range to find a space and then shmat over the top of that.

Alan
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