Re: [PATCH v7 25/27] mm/mmap: Add Shadow stack pages to memory accounting

[Yu-cheng Yu <yu-cheng.yu@intel.com>]

On Tue, 2019-06-11 at 10:55 -0700, Dave Hansen wrote:
> On 6/6/19 1:06 PM, Yu-cheng Yu wrote:
> > --- a/mm/mmap.c
> > +++ b/mm/mmap.c
> > @@ -1703,6 +1703,9 @@ static inline int accountable_mapping(struct file
> > *file, vm_flags_t vm_flags)
> >  	if (file && is_file_hugepages(file))
> >  		return 0;
> >  
> > +	if (arch_copy_pte_mapping(vm_flags))
> > +		return 1;
> > +
> >  	return (vm_flags & (VM_NORESERVE | VM_SHARED | VM_WRITE)) ==
> > VM_WRITE;
> >  }
> >  
> > @@ -3319,6 +3322,8 @@ void vm_stat_account(struct mm_struct *mm, vm_flags_t
> > flags, long npages)
> >  		mm->stack_vm += npages;
> >  	else if (is_data_mapping(flags))
> >  		mm->data_vm += npages;
> > +	else if (arch_copy_pte_mapping(flags))
> > +		mm->data_vm += npages;
> >  }
> 
> This classifies shadow stack as data instead of stack.  That seems a wee
> bit counterintuitive.  Why did you make this choice?

I don't recall the reason; I will change it to stack and test it out.

Yu-cheng