[PATCH v25 06/28] riscv/mm : ensure PROT_WRITE leads to VM_READ | VM_WRITE

[Deepak Gupta]

On Thu, Dec 11, 2025 at 12:47 AM Paul Walmsley <pjw at kernel.org> wrote:
>
> On Fri, 5 Dec 2025, Deepak Gupta via B4 Relay wrote:
>
> > From: Deepak Gupta <debug at rivosinc.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 at sifive.com>
> > Reviewed-by: Alexandre Ghiti <alexghiti at rivosinc.com>
> > Signed-off-by: Arnd Bergmann <arnd at arndb.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.