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

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Message-ID: <20081008084350.GI7971@one.firstfloor.org>
Date:	Wed, 8 Oct 2008 10:43:50 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
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

On Wed, Oct 08, 2008 at 09:34:24AM +0100, Alan Cox wrote:
> Oh and as a PS you can also (for the hint case) do this:
> 
> 	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.

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

-Andi

-- 
ak@...ux.intel.com
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