Received-SPF: pass (google.com: domain of linux-kernel+bounces-215421-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:40f1:3f00::1 as permitted sender) client-ip=2604:1380:40f1:3f00::1;
Precedence: bulk
MIME-Version: 1.0
References: <20240614182327.752156-1-jeffxu@google.com> <20240614182327.752156-2-jeffxu@google.com>
In-Reply-To: <20240614182327.752156-2-jeffxu@google.com>
From: Jann Horn <jannh@google.com>
Date: Fri, 14 Jun 2024 20:42:28 +0200
Message-ID: <CAG48ez0c3PyXhaW78tCXW0_e45YJtfOGj=shKZrLu5RZJ66vGg@mail.gmail.com>
Subject: Re: [PATCH v1 1/1] /proc/pid/smaps: add mseal info for vma
To: jeffxu@chromium.org
Cc: akpm@linux-foundation.org, sroettger@google.com, rdunlap@infradead.org, 
	david@redhat.com, adhemerval.zanella@linaro.org, linux-kernel@vger.kernel.org, 
	linux-mm@kvack.org, jorgelo@chromium.org, keescook@chromium.org
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

Hi!

On Fri, Jun 14, 2024 at 8:24=E2=80=AFPM <jeffxu@chromium.org> wrote:
> Add sp in /proc/pid/smaps to indicate vma is sealed
>
> Signed-off-by: Jeff Xu <jeffxu@chromium.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/filesyste=
ms/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 vm=
a */
>  #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 arch=
itectures */
>  #define VM_HIGH_ARCH_BIT_1     33      /* bit only usable on 64-bit arch=
itectures */

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?