linux-kernel - Re: [patch 29/29] initrd: Fix virtual/physical mix-up in overwrite test

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Date:	Thu, 24 Jul 2008 20:49:27 +0200 (CEST)
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Atsushi Nemoto <anemo@....ocn.ne.jp>
cc:	Ralf Baechle <ralf@...ux-mips.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-m68k@...r.kernel.org,
	Linux Kernel Development <linux-kernel@...r.kernel.org>,
	Linux/MIPS Development <linux-mips@...ux-mips.org>,
	linux-arch@...r.kernel.org
Subject: Re: [patch 29/29] initrd: Fix virtual/physical mix-up in overwrite
 test

	Hi Nemoto-san,

On Fri, 25 Jul 2008, Atsushi Nemoto wrote:
> On Thu, 17 Jul 2008 21:16:36 +0200, Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> >  	if (initrd_start && !initrd_below_start_ok &&
> > -			initrd_start < min_low_pfn << PAGE_SHIFT) {
> > +	    page_to_pfn(virt_to_page(initrd_start)) < min_low_pfn) {
> >  		printk(KERN_CRIT "initrd overwritten (0x%08lx < 0x%08lx) - "
> > -		    "disabling it.\n",initrd_start,min_low_pfn << PAGE_SHIFT);
> > +		    "disabling it.\n",
> > +		    page_to_pfn(virt_to_page(initrd_start)), min_low_pfn);
> >  		initrd_start = 0;
> >  	}
> 
> This patch causes warnings on mips:
> 
> linux/init/main.c: In function 'start_kernel':
> linux/init/main.c:633: warning: passing argument 1 of 'virt_to_phys' makes pointer from integer without a cast
> linux/init/main.c:636: warning: passing argument 1 of 'virt_to_phys' makes pointer from integer without a cast
> 
> Because an argument of mips virt_to_phys() is an pointer and
> initrd_start is unsigned long.  It seems most (all?) arch's
> virt_to_phys() casts its argument to unsigned long internally.  Should
> mips follow?

Alternatively, as initrd_start is really a virtual kernel address,
perhaps it should be changed from unsigned long to void * instead?

It's cast to `void *' in several place. arch/xtensa/kernel/setup.c even
has `extern void *initrd_start' to fool around this?

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds
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