Re: [PATCH] Revert "riscv: Reset pmm when PR_TAGGED_ADDR_ENABLE is not set"

[Paul Walmsley]

On Wed, 19 Aug 2026, Samuel Holland wrote:

> This reverts commit 3033b2b1e3949274f33a140e2a97571b5a307298.
> 
> The reverted patch is userspace-visible behavior change, not a bug fix.
> The two variables here (pmm and pmlen) control two independent features:
> pmm is the _hardware_ pointer masking mode that applies while executing
> in userspace. pmlen is the shift amount that the _kernel_ uses when
> untagging addresses; PMLEN_0 means no untagging occurs, so the kernel
> does not accept tagged addresses in syscall arguments.
> 
> It is valid (as documented and tested by the self test) to enable
> pointer masking without enabling the tagged address ABI. This separation
> is necessary to allow userspace to create an execution environment
> similar to what the kernel supports on arm64 by default, where TBI is
> enabled but the tagged address ABI is not. (On arm64, there is no
> equivalent to PR_PMLEN_MASK because TBI is always enabled.)
> 
> Signed-off-by: Samuel Holland <samuel.holland@xxxxxxxxxx>

Thanks, queued for v7.3-rc with a Fixes: tag and cc: stable.


- Paul