linux-kernel - Re: [BUG] SLOB breaks Crypto

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Message-Id: <20100519.125630.121263182.davem@davemloft.net>
Date:	Wed, 19 May 2010 12:56:30 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	cl@...ux.com
Cc:	lethal@...ux-sh.org, penberg@...helsinki.fi, mpm@...enic.com,
	herbert@...dor.hengli.com.au, ken@...elabs.ch,
	geert@...ux-m68k.org, michael-dev@...i-braun.de,
	linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
	anemo@....ocn.ne.jp, dwmw2@...radead.org
Subject: Re: [BUG] SLOB breaks Crypto

From: Christoph Lameter <cl@...ux.com>
Date: Wed, 19 May 2010 10:19:33 -0500 (CDT)

> The assumptions are not arbitrary. It is reasonable to assume that
> structures managed by the slab allocators may contain long long variables
> and that therefore a unsigned long long alignment is required by the
> allocator. It is the *compiler* who tells us that long long needs to be
> aligned at double word boundaries. If an arch does not require long long
> alignment on double word boundaries then the *compiler* should tell us
> that and then the allocators will align on word boundaries.

That is a good point.

So really, __alignof__(unsigned long long) is technically always right.
Because it should evaluate to "4" on x86-32, for example.
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