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Message-ID: <alpine.DEB.2.20.1801161205590.1771@nuc-kabylake>
Date: Tue, 16 Jan 2018 12:07:49 -0600 (CST)
From: Christopher Lameter <cl@...ux.com>
To: Matthew Wilcox <willy@...radead.org>
cc: Kees Cook <keescook@...omium.org>, linux-kernel@...r.kernel.org,
David Windsor <dave@...lcore.net>, Pekka Enberg <penberg@...nel.org>,
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Subject: Re: kmem_cache_attr (was Re: [PATCH 04/36] usercopy: Prepare for
usercopy whitelisting)
On Tue, 16 Jan 2018, Matthew Wilcox wrote:
> > Sure this data is never changed. It can be const.
>
> It's changed at initialisation. Look:
>
> kmem_cache_create(const char *name, size_t size, size_t align,
> slab_flags_t flags, void (*ctor)(void *))
> s = create_cache(cache_name, size, size,
> calculate_alignment(flags, align, size),
> flags, ctor, NULL, NULL);
>
> The 'align' that ends up in s->align, is not the user-specified align.
> It's also dependent on runtime information (cache_line_size()), so it
> can't be calculated at compile time.
Then we would need another align field in struct kmem_cache that takes the
changes value?
> 'flags' also gets mangled:
> flags &= CACHE_CREATE_MASK;
Well ok then that also belongs into kmem_cache and the original value
stays in kmem_cache_attr.
> unsigned int would be my preference.
Great.
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