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From: Deepak Gupta <debug@rivosinc.com>
Date: Fri, 29 Dec 2023 18:30:39 -0800
Message-ID: <CAKC1njTPBqtsAOn-CWhB+-8FaZ2KWkkz-vRZr7MZq=0yLUdjcQ@mail.gmail.com>
Subject: Re: [PATCH v1] mm: abstract shadow stack vma behind arch_is_shadow_stack_vma
To: Andrew Morton <akpm@linux-foundation.org>
Cc: rick.p.edgecombe@intel.com, broonie@kernel.org, linux-mm@kvack.org, 
	linux-kernel@vger.kernel.org
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On Wed, Dec 27, 2023 at 2:24=E2=80=AFPM Andrew Morton <akpm@linux-foundatio=
n.org> wrote:
>
> On Wed, 27 Dec 2023 14:20:36 -0800 Deepak Gupta <debug@rivosinc.com> wrot=
e:
>
> > On Wed, Dec 27, 2023 at 1:45=E2=80=AFPM Andrew Morton <akpm@linux-found=
ation.org> wrote:
> > >
> > > On Fri, 22 Dec 2023 15:51:04 -0800 Deepak Gupta <debug@rivosinc.com> =
wrote:
> > >
> > > > x86 has used VM_SHADOW_STACK (alias to VM_HIGH_ARCH_5) to encode sh=
adow
> > > > stack VMA. VM_SHADOW_STACK is thus not possible on 32bit. Some arch=
es may
> > > > need a way to encode shadow stack on 32bit and 64bit both and they =
may
> > > > encode this information differently in VMAs.
> > >
> > > Is such a patch in the pipeline?  Otherwise we're making a change tha=
t
> > > serves no purpose.
> >
> > Yes I do have patches in the pipeline for riscv.
> > On riscv, presence of only `VM_WRITE` (i.e. (flags & (VM_READ |
> > VM_WRITE | VM_EXEC))
> > =3D=3D VM_WRITE) would mean a shadow stack.
> > And yes there would be  relevant patches to ensure that existing consum=
ers using
> > `PROT_WRITE` gets translated to (VM_WRITE | VM_READ)
>
> OK, please plan to carry this patch in whatever tree contains the above.
>
>
ACK. Thanks