Re: [PATCH 1/4] [tip:x86/mm] Correcting improper large page preservation

[Siarhei Liakh]

On Sat, Apr 3, 2010 at 2:43 AM, Suresh Siddha <suresh.b.siddha@xxxxxxxxx> wrote:
> On Wed, 2010-03-31 at 18:59 -0700, Siarhei Liakh wrote:
>> +     /*
>> +      * .data and .bss should always be writable.
>> +      */
>> +     if ((within(pfn, __pa((unsigned long)_sdata) >> PAGE_SHIFT,
>> +                __pa((unsigned long)_edata) >> PAGE_SHIFT)) ||
>> +         (within(pfn, __pa((unsigned long)__bss_start) >> PAGE_SHIFT,
>> +                __pa((unsigned long)__bss_stop) >> PAGE_SHIFT))) {
>> +             pgprot_val(required) |= _PAGE_RW;
>> +     }
>
> I have reviewed this patch and the only comment I have is:
>
> On 64bit kernels, kernel text/data mapping and kernel identity mappings
> are different virtual addresses mapping to same pfn ranges. For the
> data/bss pages, does it help (in identifying certain data corruptions
> more easily) in making the kernel identity mapping to be set to
> read-only and enforce the need of RW only for the kernel data mappings.
>
> Or is there some obscure code that uses something like
> __va(__pa(data_symbol)) and writes to it?
>
> If not, we can remove the __pa() constructs above and use the addr for
> comparisons.

Done.
Patch V2 have been posted.
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