linux-kernel - Re: [PATCH v38 21/24] x86/vdso: Implement a vDSO for Intel SGX enclave call

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Date:   Mon, 28 Sep 2020 04:32:26 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     x86@...nel.org, linux-sgx@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Andy Lutomirski <luto@...capital.net>,
        Jethro Beekman <jethro@...tanix.com>,
        Cedric Xing <cedric.xing@...el.com>, akpm@...ux-foundation.org,
        andriy.shevchenko@...ux.intel.com, asapek@...gle.com, bp@...en8.de,
        chenalexchen@...gle.com, conradparker@...gle.com,
        cyhanish@...gle.com, dave.hansen@...el.com, haitao.huang@...el.com,
        josh@...htriplett.org, kai.huang@...el.com, kai.svahn@...el.com,
        kmoy@...gle.com, ludloff@...gle.com, luto@...nel.org,
        nhorman@...hat.com, npmccallum@...hat.com, puiterwijk@...hat.com,
        rientjes@...gle.com, tglx@...utronix.de, yaozhangx@...gle.com
Subject: Re: [PATCH v38 21/24] x86/vdso: Implement a vDSO for Intel SGX
 enclave call

On Tue, Sep 15, 2020 at 02:05:19PM +0300, Jarkko Sakkinen wrote:
> +struct sgx_enclave_run {
> +	__u64 tcs;
> +	__u32 flags;
> +	__u32 exit_reason;
> +
> +	union {
> +		sgx_enclave_exit_handler_t user_handler;
> +		__u64 __user_handler;
> +	};

I will replace this with just:

	__u64 user_handler;

> +	__u64 user_data;
> +
> +	union {
> +		struct sgx_enclave_exception exception;
> +
> +		/* Pad the entire struct to 256 bytes. */
> +		__u8 pad[256 - 32];
> +	};
> +};

Resulting:


struct sgx_enclave_run {
	__u64 tcs;
	__u32 flags;
	__u32 exit_reason;
	__u64 user_handler;
	__u64 user_data;

	union {
		struct sgx_enclave_exception exception;

		/* Pad the entire struct to 256 bytes. */
		__u8 pad[256 - 32];
	};
};

BTW, why there is that padding?

/Jarkko