Re: [PATCH v8 4/4] arm64: vdso32: Implement __vdso_futex_robust_try_unlock()
From: André Almeida
Date: Thu Sep 17 2026 - 11:19:16 EST
Em 17/09/2026 07:50, Mark Rutland escreveu:
On Wed, Sep 16, 2026 at 10:11:01PM -0300, André Almeida wrote:Gotcha, makes perfect sense.
Em 16/09/2026 11:28, Mark Rutland escreveu:
On Fri, Aug 21, 2026 at 06:50:45PM -0300, André Almeida wrote:
Based on aarch64 implementation, provide a 32 bit entry point for
this vDSO.
In order to keep compatibility with arm64_futex_robust_unlock_get_pop(),
make sure to store the pop address at r2 and the compare result value
at r3.
Before we add this to the compat vdso, we'll need to implement this on
arch/arm/.
Otherwise, my comments on the patch for the native vdso functions apply
here too.
Right, and the compat entry point at arch/arm64/ would point to the
__vdso_futex_robust_list32_try_unlock implementation at arch/arm/?
So far we've had arm64 provide its own copy (which e.g. might use
sequences relying on ARMv8+ instructions), so I think we'd do the same
here.
The key thing is that 32-bit tasks on arm64 should see the same ABI as
native tasks on 32-bit arm. As there's a risk that 32-bit arm might have
some ABI quirks (e.g. due to older processors), we don't want to enable
features for compat tasks on arm64 before that's been implemented on
32-bit arm.
Thanks!
André