[PATCH V6 2/2] arm: mm: Modify pte_write and pmd_write logic for LPAE

[Russell King - ARM Linux]

On Thu, Jul 03, 2014 at 01:06:13PM +0100, Steve Capper wrote:
> diff --git a/arch/arm/mm/dump.c b/arch/arm/mm/dump.c
> index c508f41..00a1cf9 100644
> --- a/arch/arm/mm/dump.c
> +++ b/arch/arm/mm/dump.c
> @@ -126,8 +126,8 @@ static const struct prot_bits section_bits[] = {
>  		.val	= PMD_SECT_USER,
>  		.set	= "USR",
>  	}, {
> -		.mask	= PMD_SECT_RDONLY,
> -		.val	= PMD_SECT_RDONLY,
> +		.mask	= PMD_SECT_AP2,
> +		.val	= PMD_SECT_AP2,

I think we're almost there, except for this hunk, which I think can
just be deleted.

We want to report what the PTEs/PMDs are requested to be, not what they
physically are at the point where we dump them out.  In other words, we
don't want to know that they're physically read-only because the dirty
bit isn't set - what we want to know is that they have permission to be
written to if the dirty bit were to be set.

The reasoning is that we want the dump to reflect what is possible -
for example, we want to know whether a page can be executed _and_ written
to.

Consider the case where the dirty bit is implemented in hardware.

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