Re: [PATCH 4/4] mm: variable length argument support

[Andrew Morton <akpm@linux-foundation.org>]

On Wed, 06 Jun 2007 10:54:21 +0200 Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:

> > > It is a bit peculiar in that we have one task with two mm's, one of which is
> > > inactive.
> > > 
> > > ...
> > >
> > > +				flush_cache_page(bprm->vma, kpos,
> > > +						 page_to_pfn(kmapped_page));
> 
> Bah, and my frv cross build bums out on an unrelated change,..
> I'll see if I can get a noMMU arch building, in the mean time, would you
> try this:
> 
> ---
> 
> Since no-MMU doesn't do the fancy inactive mm access there is no need to
> flush cache.
> 
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
> ---
> 
> Index: linux-2.6-2/fs/exec.c
> ===================================================================
> --- linux-2.6-2.orig/fs/exec.c	2007-06-05 16:48:52.000000000 +0200
> +++ linux-2.6-2/fs/exec.c	2007-06-06 10:49:19.000000000 +0200
> @@ -428,8 +428,10 @@ static int copy_strings(int argc, char _
>  				kmapped_page = page;
>  				kaddr = kmap(kmapped_page);
>  				kpos = pos & PAGE_MASK;
> +#ifdef CONFIG_MMU
>  				flush_cache_page(bprm->vma, kpos,
>  						 page_to_pfn(kmapped_page));
> +#endif
>  			}
>  			if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
>  				ret = -EFAULT;
> 

I think the same problem will happen on NOMMU && STACK_GROWS_UP.  There are
several new references to bprm->vma in there, not all inside CONFIG_MMU.