Re: [PATCH 2/2] arm: apply more __ro_after_init

[Arnd Bergmann]

On Wednesday, August 10, 2016 10:43:39 AM CEST Russell King - ARM Linux wrote:
> On Fri, Jun 03, 2016 at 11:40:24AM -0700, Kees Cook wrote:
> > @@ -1309,16 +1309,11 @@ void __init arm_mm_memblock_reserve(void)
> >   * Any other function or debugging method which may touch any device _will_
> >   * crash the kernel.
> >   */
> > +static char vectors[PAGE_SIZE * 2] __ro_after_init __aligned(PAGE_SIZE);
> >  static void __init devicemaps_init(const struct machine_desc *mdesc)
> >  {
> >       struct map_desc map;
> >       unsigned long addr;
> > -     void *vectors;
> > -
> > -     /*
> > -      * Allocate the vector page early.
> > -      */
> > -     vectors = early_alloc(PAGE_SIZE * 2);
> 
> This one is not appropriate.  We _do_ write to these pages after init
> for FIQ handler updates.  See set_fiq_handler().

Is that the only thing that modifies the page? If we think this is a
valuable change, we could make it depend on the absence of FIQ
support, as very few platforms (rpc, omap1, s3c24xx and possibly
imx) seem to even use it.

	Arnd