linux-kernel - Re: [PATCH v1 1/1] /proc/pid/smaps: add mseal info for vma

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Date: Fri, 14 Jun 2024 12:00:49 -0700
From: Jeff Xu <jeffxu@...omium.org>
To: Jann Horn <jannh@...gle.com>
Cc: akpm@...ux-foundation.org, sroettger@...gle.com, rdunlap@...radead.org, 
	david@...hat.com, adhemerval.zanella@...aro.org, linux-kernel@...r.kernel.org, 
	linux-mm@...ck.org, jorgelo@...omium.org, keescook@...omium.org
Subject: Re: [PATCH v1 1/1] /proc/pid/smaps: add mseal info for vma

On Fri, Jun 14, 2024 at 11:43 AM Jann Horn <jannh@...gle.com> wrote:
>
> Hi!
>
> On Fri, Jun 14, 2024 at 8:24 PM <jeffxu@...omium.org> wrote:
> > Add sp in /proc/pid/smaps to indicate vma is sealed
> >
> > Signed-off-by: Jeff Xu <jeffxu@...omium.org>
> > ---
> >  Documentation/filesystems/proc.rst | 1 +
> >  fs/proc/task_mmu.c                 | 3 +++
> >  include/linux/mm.h                 | 5 +++++
> >  mm/internal.h                      | 5 -----
> >  4 files changed, 9 insertions(+), 5 deletions(-)
> >
> > diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst
> > index 7c3a565ffbef..400217a1589c 100644
> > --- a/Documentation/filesystems/proc.rst
> > +++ b/Documentation/filesystems/proc.rst
> > @@ -571,6 +571,7 @@ encoded manner. The codes are the following:
> >      um    userfaultfd missing tracking
> >      uw    userfaultfd wr-protect tracking
> >      ss    shadow stack page
> > +    sp    sealed page
>
> Nit: Why "page"? The sealing is a property of the VMA, not of the
> pages mapped into it. Maybe "sealed area" and an abbreviation like
> "sl" would make sense?
>
> > diff --git a/include/linux/mm.h b/include/linux/mm.h
> > index 587d34879865..8600564898fa 100644
> > --- a/include/linux/mm.h
> > +++ b/include/linux/mm.h
> > @@ -314,6 +314,11 @@ extern unsigned int kobjsize(const void *objp);
> >  #define VM_NOHUGEPAGE  0x40000000      /* MADV_NOHUGEPAGE marked this vma */
> >  #define VM_MERGEABLE   0x80000000      /* KSM may merge identical pages */
> >
> > +#ifdef CONFIG_64BIT
> > +/* VM is sealed, in vm_flags */
> > +#define VM_SEALED      _BITUL(63)
> > +#endif
> > +
> >  #ifdef CONFIG_ARCH_USES_HIGH_VMA_FLAGS
> >  #define VM_HIGH_ARCH_BIT_0     32      /* bit only usable on 64-bit architectures */
> >  #define VM_HIGH_ARCH_BIT_1     33      /* bit only usable on 64-bit architectures */
>
> Other 64-bit flags are defined further down; maybe it would make sense
> to move this definition below the definition of VM_ALLOW_ANY_UNCACHED,
> so that the definitions are sorted by the number of the bit?

Sure.  I will update.

Thanks!
-Jeff