Re: [PATCH 1/3] make page-aligned data and bss less fragile

[Paul Mundt <lethal@linux-sh.org>]

On Wed, May 28, 2008 at 05:04:34PM +0100, Jeremy Fitzhardinge wrote:
> Making a variable page-aligned by using
> __attribute__((section(".data.page_aligned"))) is fragile because if
> sizeof(variable) is not also a multiple of page size, it leaves
> variables in the remainder of the section unaligned.
> 
> This patch introduces two new qualifiers, __page_aligned_data and
> __page_aligned_bss to set the section *and* the alignment of
> variables.  This makes page-aligned variables more robust because the
> linker will make sure they're aligned properly.  Unfortunately it
> requires *all* page-aligned data to use these macros...
> 
> It also updates arch/x86's use of page-aligned variables, since its
> the heaviest user of them in the kernel.  The change to
> arch/x86/xen/mmu.c fixes an actual bug, but the rest are cleanups
> and to set a precident.
> 
> [ I don't know if this would be easier to manage by splitting the
>  x86 part out from the common part. Two following patches apply to
>  powerpc and sh; they're purely decorative. ]
> 
> Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
> Cc: Paul Mundt <lethal@linux-sh.org>
> Cc: Paul Mackerras <paulus@samba.org>

Acked-by: Paul Mundt <lethal@linux-sh.org>