[uClinux-dev] Re: [PATCH] FLAT: allow arches to declare a larger alignment than the slab

Paul Mundt lethal at linux-sh.org
Wed May 26 03:33:34 EDT 2010


On Wed, May 26, 2010 at 03:23:02AM -0400, Mike Frysinger wrote:
> On Wed, May 26, 2010 at 02:59, Geert Uytterhoeven wrote:
> > from looking at <linux/flat.h>, it looks like the FLAT binary format
> > doesn't contain any
> > alignment information? So if I put __attribute__((aligned(4096))) in a
> > file, there's still
> > no guarantee it will actually be in memory at a 4Ki-aligned address?
> 
> i believe that is correct.  FLAT behavior today provides alignment of
> either sizeof(unsigned long) or ARCH_SLAB_MINALIGN.
> 
> i imagine something like this would work today because everyone
> defines it to a constant:
> -#ifdef ARCH_SLAB_MINALIGN
> +#if defined(ARCH_SLAB_MINALIGN) && ARCH_SLAB_MINALIGN != 0
> but this would break if someone tried using gcc sizeof/alignof/etc...

alignof is used by SLUB/SLOB to set the ARCH_SLAB_MINALIGN value if the
architecture hasn't already specified one, so that wouldn't work.



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