ARM: add support to dump the kernel page tables

[linux@arm.linux.org.uk (Russell King - ARM Linux)]

On Thu, Oct 31, 2013 at 10:28:38AM -0700, Laura Abbott wrote:
> On 10/24/2013 12:16 AM, Russell King - ARM Linux wrote:
> ...
>> +	}, {
>> +		.mask	= L_PTE_MT_MASK,
>> +		.val	= L_PTE_MT_DEV_SHARED,
>> +		.set	= "DEV/SHARED",
>> +	}, {
>> +		.mask	= L_PTE_MT_MASK,
>> +		.val	= L_PTE_MT_DEV_NONSHARED,
>> +		.set	= "DEV/NONSHARED",
>> +	}, {
>
> L_PTE_MT_DEV_SHARED and L_PTE_MT_DEV_NONSHARED are the same on LPAE  
> systems which leads to bad output:
>
> 0xcd400000-0xcd401000           4K     RW NX SHD DEV/SHARED DEV/NONSHARED

So we probably want to make this conditional:

#if L_PTE_MT_DEV_SHARED != L_PTE_MT_DEV_NONSHARED
	... dev/non-shared entry
#endif

or we use a separate table for LPAE.

>> +		.mask	= L_PTE_MT_MASK,
>> +		.val	= L_PTE_MT_DEV_WC,
>> +		.set	= "DEV/WC",
>> +	}, {
>> +		.mask	= L_PTE_MT_MASK,
>> +		.val	= L_PTE_MT_DEV_CACHED,
>> +		.set	= "DEV/CACHED",
>> +	},
>> +};
>> +
>> +static const struct prot_bits section_bits[] = {
>> +	/* These are approximate */
>> +	{
>> +		.mask	= PMD_SECT_AP_READ | PMD_SECT_AP_WRITE,
>> +		.val	= 0,
>> +		.set	= "    ro",
>> +	}, {
>> +		.mask	= PMD_SECT_AP_READ | PMD_SECT_AP_WRITE,
>> +		.val	= PMD_SECT_AP_WRITE,
>> +		.set	= "    RW",
>> +	}, {
>> +		.mask	= PMD_SECT_AP_READ | PMD_SECT_AP_WRITE,
>> +		.val	= PMD_SECT_AP_READ,
>> +		.set	= "USR RO",
>> +	}, {
>> +		.mask	= PMD_SECT_AP_READ | PMD_SECT_AP_WRITE,
>> +		.val	= PMD_SECT_AP_READ | PMD_SECT_AP_WRITE,
>> +		.set	= "USR RW",
>> +	}, {
>
> Same issue here for PMD_SECT_AP_READ and PMD_SEC_AP_WRITE, both of those  
> are 0 on LPAE so the output looks strange:
>
> 0xc0000000-0xcd400000         212M     ro     RW USR RO USR RW x  SHD

I think this needs to be a separate table - it's just too different,
and it looks like the PMD_SECT_USER and PMD_SECT_RDONLY can be
separately decoded.