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

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Message-ID: <d3d027a903524729454efa235155e5db75216e66.camel@intel.com>
Date:   Tue, 11 Jun 2019 12:22:48 -0700
From:   Yu-cheng Yu <yu-cheng.yu@...el.com>
To:     Dave Hansen <dave.hansen@...el.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-mm@...ck.org,
        linux-arch@...r.kernel.org, linux-api@...r.kernel.org,
        Arnd Bergmann <arnd@...db.de>,
        Andy Lutomirski <luto@...capital.net>,
        Balbir Singh <bsingharora@...il.com>,
        Borislav Petkov <bp@...en8.de>,
        Cyrill Gorcunov <gorcunov@...il.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Eugene Syromiatnikov <esyr@...hat.com>,
        Florian Weimer <fweimer@...hat.com>,
        "H.J. Lu" <hjl.tools@...il.com>, Jann Horn <jannh@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        Kees Cook <keescook@...omium.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Oleg Nesterov <oleg@...hat.com>, Pavel Machek <pavel@....cz>,
        Peter Zijlstra <peterz@...radead.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Vedvyas Shanbhogue <vedvyas.shanbhogue@...el.com>,
        Dave Martin <Dave.Martin@....com>
Subject: Re: [PATCH v7 25/27] mm/mmap: Add Shadow stack pages to memory
 accounting

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