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Date: Fri, 11 Aug 2023 17:36:05 +0100
From: Catalin Marinas <catalin.marinas@arm.com>
To: Mark Brown <broonie@kernel.org>
Cc: Will Deacon <will@kernel.org>, Jonathan Corbet <corbet@lwn.net>,
	Andrew Morton <akpm@linux-foundation.org>,
	Marc Zyngier <maz@kernel.org>,
	Oliver Upton <oliver.upton@linux.dev>,
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	Eric Biederman <ebiederm@xmission.com>,
	Kees Cook <keescook@chromium.org>, Shuah Khan <shuah@kernel.org>,
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	Deepak Gupta <debug@rivosinc.com>, Ard Biesheuvel <ardb@kernel.org>,
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Subject: Re: [PATCH v4 07/36] arm64/gcs: Provide copy_to_user_gcs()
Message-ID: <ZNZjdXTJw2p5vh7C@arm.com>
References: <20230807-arm64-gcs-v4-0-68cfa37f9069@kernel.org>
 <20230807-arm64-gcs-v4-7-68cfa37f9069@kernel.org>
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In-Reply-To: <20230807-arm64-gcs-v4-7-68cfa37f9069@kernel.org>

On Mon, Aug 07, 2023 at 11:00:12PM +0100, Mark Brown wrote:
> +static inline int copy_to_user_gcs(unsigned long __user *addr,
> +				   unsigned long *val,
> +				   int count)
> +{
> +	int ret = -EFAULT;
> +	int i;
> +
> +	if (access_ok((char __user *)addr, count * sizeof(u64))) {
> +		uaccess_ttbr0_enable();
> +		for (i = 0; i < count; i++) {
> +			ret = gcssttr(addr++, *val++);
> +			if (ret != 0)
> +				break;
> +		}
> +		uaccess_ttbr0_disable();
> +	}
> +
> +	return ret;
> +}

I think it makes more sense to have a put_user_gcs() of a single
element. I've only seen it used with 2 elements in the signal code but
we could as well do two put_user_gcs() calls (as we do for other stuff
that we push to the signal frame).

-- 
Catalin