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