linux-kernel - Re: [PATCH v3] ARM: early fixmap support for earlycon

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Date:	Fri, 10 Jul 2015 12:25:22 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Stefan Agner <stefan@...er.ch>
Cc:	Rob Herring <robh@...nel.org>,
	Laura Abbott <lauraa@...eaurora.org>,
	Kees Cook <keescook@...omium.org>,
	Arnd Bergmann <arnd@...db.de>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	linux-kernel@...r.kernel.org, Mark Salter <msalter@...hat.com>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3] ARM: early fixmap support for earlycon

On Sat, Jun 06, 2015 at 01:48:00PM +0100, Russell King - ARM Linux wrote:
> On Sat, Jun 06, 2015 at 02:31:28PM +0200, Stefan Agner wrote:
> > @@ -1231,7 +1272,7 @@ static void __init devicemaps_init(const struct machine_desc *mdesc)
> >  
> >  	early_trap_init(vectors);
> >  
> > -	for (addr = VMALLOC_START; addr; addr += PMD_SIZE)
> > +	for (addr = VMALLOC_START; addr < FIXADDR_START; addr += PMD_SIZE)
> >  		pmd_clear(pmd_off_k(addr));
> 
> You introduce a bug here - we no logner clear the very top entry of the
> page tables, which means it could contain anything - and means that the
> subsequent creation of the L2 table in early_pte_alloc() can fail.

You trimmed my reply hard, and seemingly ignored this; the v4 patch
contains exactly the same code here, and therefore continues to leave
the top of the page table uninitialised.

Not applying the v4 patch, sorry.

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