Re: [Xen-devel] [PATCH v2 2/2] x86/xpti: don't map stack guard pages

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 02.03.18 at 16:43, <jgross@xxxxxxxx> wrote:
> On 02/03/18 15:35, Jan Beulich wrote:
>> --- a/xen/arch/x86/mm.c
>> +++ b/xen/arch/x86/mm.c
>> @@ -5576,6 +5576,14 @@ void memguard_unguard_stack(void *p)
>>                             STACK_SIZE - PRIMARY_STACK_SIZE - IST_MAX * 
>> PAGE_SIZE);
>>  }
>>  
>> +bool memguard_is_stack_guard_page(unsigned long addr)
>> +{
>> +    addr &= STACK_SIZE - 1;
>> +
>> +    return addr >= IST_MAX * PAGE_SIZE &&
>> +           addr < STACK_SIZE - PRIMARY_STACK_SIZE;
>> +}
>> +
> 
> What about making use of memguard_is_stack_guard_page() in
> memguard_[un]guard_stack() ?

I was considering this as a follow-up step.

> This would at once ensure the other unused
> pages won't be accessed accidentally somewhere.

I don't understand this part, though.

Jan


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