linux-kernel - Re: [PATCH v2 5/7] arm64: ptrace: nofpsimd: Fail FP/SIMD regset operations

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Date:   Fri, 10 Jan 2020 15:12:32 +0000
From:   Catalin Marinas <catalin.marinas@....com>
To:     Suzuki K Poulose <suzuki.poulose@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        will@...nel.org, maz@...nel.org, mark.rutland@....com,
        dave.martin@....com, ard.biesheuvel@...aro.org,
        christoffer.dall@....com, Will Deacon <will.deacon@....com>
Subject: Re: [PATCH v2 5/7] arm64: ptrace: nofpsimd: Fail FP/SIMD regset
 operations

On Tue, Dec 17, 2019 at 06:34:00PM +0000, Suzuki K Poulose wrote:
> diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
> index 6771c399d40c..0135b944b8db 100644
> --- a/arch/arm64/kernel/ptrace.c
> +++ b/arch/arm64/kernel/ptrace.c
> @@ -637,6 +637,9 @@ static int fpr_get(struct task_struct *target, const struct user_regset *regset,
>  		   unsigned int pos, unsigned int count,
>  		   void *kbuf, void __user *ubuf)
>  {
> +	if (!system_supports_fpsimd())
> +		return -EINVAL;
> +
>  	if (target == current)
>  		fpsimd_preserve_current_state();

I checked the coredump code (fill_thread_core_info) and works correctly
if we return -EINVAL here. But for completeness, we could add an
fpr_active() callback to aarch{32,64}_regsets (x86 does the same).

-- 
Catalin