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Date:   Mon, 28 Sep 2020 18:02:53 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To:     Borislav Petkov <bp@alien8.de>
Cc:     x86@kernel.org, linux-sgx@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Andy Lutomirski <luto@amacapital.net>,
        Jethro Beekman <jethro@fortanix.com>,
        Cedric Xing <cedric.xing@intel.com>, akpm@linux-foundation.org,
        andriy.shevchenko@linux.intel.com, asapek@google.com,
        chenalexchen@google.com, conradparker@google.com,
        cyhanish@google.com, dave.hansen@intel.com, haitao.huang@intel.com,
        josh@joshtriplett.org, kai.huang@intel.com, kai.svahn@intel.com,
        kmoy@google.com, ludloff@google.com, luto@kernel.org,
        nhorman@redhat.com, npmccallum@redhat.com, puiterwijk@redhat.com,
        rientjes@google.com, tglx@linutronix.de, yaozhangx@google.com
Subject: Re: [PATCH v38 21/24] x86/vdso: Implement a vDSO for Intel SGX
 enclave call
Message-ID: <20200928150253.GD70098@linux.intel.com>
References: <20200915112842.897265-1-jarkko.sakkinen@linux.intel.com>
 <20200915112842.897265-22-jarkko.sakkinen@linux.intel.com>
 <20200924180407.GO5030@zn.tnic>
 <20200925010031.GH119995@linux.intel.com>
 <20200925082807.GG16872@zn.tnic>
 <20200927233700.GA4450@linux.intel.com>
 <20200928083032.GB1685@zn.tnic>
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Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo
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On Mon, Sep 28, 2020 at 10:30:32AM +0200, Borislav Petkov wrote:
> On Mon, Sep 28, 2020 at 02:37:00AM +0300, Jarkko Sakkinen wrote:
> > I did not get Sean's reply, and neither can find it from lore:
> > 
> > https://lore.kernel.org/linux-sgx/20200915112842.897265-1-jarkko.sakkinen@linux.intel.com/T/#t
> 
> Yah, your mail server upgrade broke a lot of stuff. And lore even says
> it is not there:
> 
> 2020-09-25 11:43           ` Jethro Beekman
>      [not found]     ` <20200925003808.GB20333@linux.intel.com>		<---
> 2020-09-25  1:04       ` Jarkko Sakkinen
> 
> Lemme bounce it to you.

Thank you. I think I have it correctly in my tree. And I actually
noticed that I had the original email stored in wrong archive folder on
my machine (sorry about that), so did I receive it after all, but it
does not exist in lore.

> > I'd make that a description and take away individual parameter
> > descriptions. Is that fine?
> 
> Sure.

/**
 * typedef sgx_enclave_exit_handler_t - Exit handler function accepted by
 *					__vdso_sgx_enter_enclave()
 * @run:	Pointer to the caller provided struct sgx_enclave_run
 *
 * The register parameters contain the snapshot of their values at enclave
 * exit
 *
 * Return:
 *  0 or negative to exit vDSO
 *  positive to re-enter enclave (must be EENTER or ERESUME leaf)
 */
typedef int (*sgx_enclave_exit_handler_t)(long rdi, long rsi, long rdx,
					  long rsp, long r8, long r9,
					  struct sgx_enclave_run *run);

I think this looks reasonable now.

Another minor clean up I made is:

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

I.e. got rid of the "user_handler union. Makes the struc less confusing
looking and is consistent with the other structs.

I've been thinking about this tail:

	union {
		struct sgx_enclave_exception exception;

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

I'd just replace this with

	__u64 exception;
};

And do something like (just writing it to the email to show the idea,
have not even compiled this):

-       mov     %eax, (SGX_ENCLAVE_RUN_EXCEPTION + SGX_EX_LEAF)(%rbx)
-       mov     %di,  (SGX_ENCLAVE_RUN_EXCEPTION + SGX_EX_TRAPNR)(%rbx)
-       mov     %si,  (SGX_ENCLAVE_RUN_EXCEPTION + SGX_EX_ERROR_CODE)(%rbx)
-       mov     %rdx, (SGX_ENCLAVE_RUN_EXCEPTION + SGX_EX_ADDRESS)(%rbx)
+       mov     SGX_ENCLAVE_RUN_EXCEPTION(%rbx), %rbx
+
+       mov     %eax, (SGX_EX_LEAF)(%rbx)
+       mov     %di,  (SGX_EX_TRAPNR)(%rbx)
+       mov     %si,  (SGX_EX_ERROR_CODE)(%rbx)
+       mov     %rdx, (SGX_EX_ADDRESS)(%rbx)

> -- 
> Regards/Gruss,
>     Boris.
> 
> https://people.kernel.org/tglx/notes-about-netiquette

/Jarkko