Re: [PATCH v2 0/3] arm64/sme: Support disabling streaming mode via ptrace on SME only systems

Catalin Marinas
2025-11-17T21:02:29Z

From: Catalin Marinas <catalin.marinas@arm.com>

On Wed, 15 Oct 2025 18:56:35 +0100, Mark Brown wrote:
> Currently it is not possible to disable streaming mode via ptrace on SME
> only systems, the interface for doing this is to write via NT_ARM_SVE but
> such writes will be rejected on a system without SVE support. Enable this
> functionality by allowing userspace to write SVE_PT_REGS_FPSIMD format data
> via NT_ARM_SVE with the vector length set to 0 on SME only systems. Such
> writes currently error since we require that a vector length is specified
> which should minimise the risk that existing software is relying on current
> behaviour.
>
> [...]

I don't think we'll get gdb feedback soon. Thanks David for the LLDB
ack.

Applied to arm64 (for-next/sme-ptrace-disable), thanks!

[1/3] arm64/sme: Support disabling streaming mode via ptrace on SME only systems
https://git.kernel.org/arm64/c/472800cd5e38
[2/3] kselftst/arm64: Test NT_ARM_SVE FPSIMD format writes on non-SVE systems
https://git.kernel.org/arm64/c/eb9df6d69a96
[3/3] kselftest/arm64: Cover disabling streaming mode without SVE in fp-ptrace
https://git.kernel.org/arm64/c/a0245b42f881

--
Catalin