linux-kernel - Re: [PATCH v25 06/28] riscv/mm : ensure PROT_WRITE leads to VM_READ

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Message-ID: <CAKC1njTfn-5ZeAV7x5819kXUqitVgO0HkKQi1S6UvZyiuroxvg@mail.gmail.com>
Date: Thu, 11 Dec 2025 09:13:01 -0800
From: Deepak Gupta <debug@...osinc.com>
To: Paul Walmsley <pjw@...nel.org>
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, 
	"H. Peter Anvin" <hpa@...or.com>, Andrew Morton <akpm@...ux-foundation.org>, 
	"Liam R. Howlett" <Liam.Howlett@...cle.com>, Vlastimil Babka <vbabka@...e.cz>, 
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, Paul Walmsley <paul.walmsley@...ive.com>, 
	Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, 
	Conor Dooley <conor@...nel.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Arnd Bergmann <arnd@...db.de>, 
	Christian Brauner <brauner@...nel.org>, Peter Zijlstra <peterz@...radead.org>, 
	Oleg Nesterov <oleg@...hat.com>, Eric Biederman <ebiederm@...ssion.com>, Kees Cook <kees@...nel.org>, 
	Jonathan Corbet <corbet@....net>, Shuah Khan <shuah@...nel.org>, Jann Horn <jannh@...gle.com>, 
	Conor Dooley <conor+dt@...nel.org>, Miguel Ojeda <ojeda@...nel.org>, 
	Alex Gaynor <alex.gaynor@...il.com>, Boqun Feng <boqun.feng@...il.com>, 
	Gary Guo <gary@...yguo.net>, Björn Roy Baron <bjorn3_gh@...tonmail.com>, 
	Andreas Hindborg <a.hindborg@...nel.org>, Alice Ryhl <aliceryhl@...gle.com>, 
	Trevor Gross <tmgross@...ch.edu>, Benno Lossin <lossin@...nel.org>, linux-kernel@...r.kernel.org, 
	linux-fsdevel@...r.kernel.org, linux-mm@...ck.org, 
	linux-riscv@...ts.infradead.org, devicetree@...r.kernel.org, 
	linux-arch@...r.kernel.org, linux-doc@...r.kernel.org, 
	linux-kselftest@...r.kernel.org, alistair.francis@....com, 
	richard.henderson@...aro.org, jim.shu@...ive.com, andybnac@...il.com, 
	kito.cheng@...ive.com, charlie@...osinc.com, atishp@...osinc.com, 
	evan@...osinc.com, cleger@...osinc.com, alexghiti@...osinc.com, 
	samitolvanen@...gle.com, broonie@...nel.org, rick.p.edgecombe@...el.com, 
	rust-for-linux@...r.kernel.org, Zong Li <zong.li@...ive.com>, 
	Andreas Korb <andreas.korb@...ec.fraunhofer.de>, 
	Valentin Haudiquet <valentin.haudiquet@...onical.com>
Subject: Re: [PATCH v25 06/28] riscv/mm : ensure PROT_WRITE leads to VM_READ | VM_WRITE

On Thu, Dec 11, 2025 at 12:47 AM Paul Walmsley <pjw@...nel.org> wrote:
>
> On Fri, 5 Dec 2025, Deepak Gupta via B4 Relay wrote:
>
> > From: Deepak Gupta <debug@...osinc.com>
> >
> > `arch_calc_vm_prot_bits` is implemented on risc-v to return VM_READ |
> > VM_WRITE if PROT_WRITE is specified. Similarly `riscv_sys_mmap` is
> > updated to convert all incoming PROT_WRITE to (PROT_WRITE | PROT_READ).
> > This is to make sure that any existing apps using PROT_WRITE still work.
> >
> > Earlier `protection_map[VM_WRITE]` used to pick read-write PTE encodings.
> > Now `protection_map[VM_WRITE]` will always pick PAGE_SHADOWSTACK PTE
> > encodings for shadow stack. Above changes ensure that existing apps
> > continue to work because underneath kernel will be picking
> > `protection_map[VM_WRITE|VM_READ]` PTE encodings.
> >
> > Reviewed-by: Zong Li <zong.li@...ive.com>
> > Reviewed-by: Alexandre Ghiti <alexghiti@...osinc.com>
> > Signed-off-by: Arnd Bergmann <arnd@...db.de>
>
> This Signed-off-by: doesn't look right.  It doesn't look like Arnd
> developed this patch, and it doesn't appear that he replied with a
> Signed-off-by: to the list regarding a patch that you wrote.  Did I miss
> it?  Did you mean Co-developed-by: or some other tag?
>

Seems like b4 messed it up. I'll fix it up.