Re: [PATCH] Fix eisa_mmap evaluation, add memory existence check

[Robert Millan <rmh@aybabtu.com>]

On Sun, Nov 18, 2007 at 12:27:37PM +0100, Robert Millan wrote:
> On Tue, Oct 23, 2007 at 09:06:16PM +0200, Christian Franke wrote:
> > +/* Check memory address */
> > +static int
> > +addr_is_valid (grub_addr_t addr)
> > +{
> > +  volatile unsigned char * p = (volatile unsigned char *)addr;
> > +  unsigned char x, y;
> > +  x = *p;
> > +  *p = x ^ 0xcf;
> > +  y = *p;
> > +  *p = x;
> > +  return y == (x ^ 0xcf);
> > +}
> 
> 0xff would be better IMO.

Uhm actually, I just remembered that we have the ~ operator precisely for
that :-)

-- 
Robert Millan

<GPLv2> I know my rights; I want my phone call!
<DRM> What use is a phone call, if you are unable to speak?
(as seen on /.)