linux-kernel - Re: [PATCH v1] mm: abstract shadow stack vma behind arch_is_shadow_stack

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Message-ID: <CAKC1njTPBqtsAOn-CWhB+-8FaZ2KWkkz-vRZr7MZq=0yLUdjcQ@mail.gmail.com>
Date: Fri, 29 Dec 2023 18:30:39 -0800
From: Deepak Gupta <debug@...osinc.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: rick.p.edgecombe@...el.com, broonie@...nel.org, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] mm: abstract shadow stack vma behind arch_is_shadow_stack_vma

On Wed, Dec 27, 2023 at 2:24 PM Andrew Morton <akpm@...ux-foundation.org> wrote:
>
> On Wed, 27 Dec 2023 14:20:36 -0800 Deepak Gupta <debug@...osinc.com> wrote:
>
> > On Wed, Dec 27, 2023 at 1:45 PM Andrew Morton <akpm@...ux-foundation.org> wrote:
> > >
> > > On Fri, 22 Dec 2023 15:51:04 -0800 Deepak Gupta <debug@...osinc.com> wrote:
> > >
> > > > x86 has used VM_SHADOW_STACK (alias to VM_HIGH_ARCH_5) to encode shadow
> > > > stack VMA. VM_SHADOW_STACK is thus not possible on 32bit. Some arches 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 that
> > > 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))
> > == VM_WRITE) would mean a shadow stack.
> > And yes there would be  relevant patches to ensure that existing consumers 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