linux-kernel - Re: [PATCH] powerpc: Fail remap_4k_pfn() if PFN doesn't fit inside PTE

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Date:	Thu, 10 Jul 2014 08:49:11 +1000
From:	Stephen Rothwell <sfr@...b.auug.org.au>
To:	Madhusudanan Kandasamy <kmadhu@...ux.vnet.ibm.com>
Cc:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>, linuxppc-dev@...abs.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] powerpc: Fail remap_4k_pfn() if PFN doesn't fit inside
 PTE

Hi Madhusudanan,

On Wed, 09 Jul 2014 21:38:31 +0530 Madhusudanan Kandasamy <kmadhu@...ux.vnet.ibm.com> wrote:
>
> diff --git a/arch/powerpc/include/asm/pte-hash64-64k.h b/arch/powerpc/include/asm/pte-hash64-64k.h
> index d836d94..10af7f1 100644
> --- a/arch/powerpc/include/asm/pte-hash64-64k.h
> +++ b/arch/powerpc/include/asm/pte-hash64-64k.h
> @@ -74,8 +74,15 @@
>  #define pte_pagesize_index(mm, addr, pte)	\
>  	(((pte) & _PAGE_COMBO)? MMU_PAGE_4K: MMU_PAGE_64K)
> 
> +static inline int bad_4k_pfn(void)
> +{
> +	WARN_ON(1);
> +	return -EINVAL;
> +}
> +
>  #define remap_4k_pfn(vma, addr, pfn, prot)				\
> -	remap_pfn_range((vma), (addr), (pfn), PAGE_SIZE,		\
> -			__pgprot(pgprot_val((prot)) | _PAGE_4K_PFN))
> +	((pfn >= (1UL << (64 - PTE_RPN_SHIFT))) ? bad_4k_pfn() :	\
> +		remap_pfn_range((vma), (addr), (pfn), PAGE_SIZE,	\
> +			__pgprot(pgprot_val((prot)) | _PAGE_4K_PFN)))
> 
>  #endif	/* __ASSEMBLY__ */

WARN_ON() returns the value it is passed, so no helper is needed:

 #define remap_4k_pfn(vma, addr, pfn, prot)				\
-	remap_pfn_range((vma), (addr), (pfn), PAGE_SIZE,		\
-			__pgprot(pgprot_val((prot)) | _PAGE_4K_PFN))
+	WARN_ON(((pfn >= (1UL << (64 - PTE_RPN_SHIFT)))) ? -EINVAL :	\
+		remap_pfn_range((vma), (addr), (pfn), PAGE_SIZE,	\
+			__pgprot(pgprot_val((prot)) | _PAGE_4K_PFN)))

-- 
Cheers,
Stephen Rothwell                    sfr@...b.auug.org.au

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