linux-kernel - Re: [PATCH 5/8] selftests/sgx: Include memory clobber for inline asm in test enclave

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Message-ID: <013cfdeb959079ff7b41bc0509b1bcfc4f1aea8a.camel@intel.com>
Date:   Fri, 18 Aug 2023 11:31:31 +0000
From:   "Huang, Kai" <kai.huang@...el.com>
To:     "linux-sgx@...r.kernel.org" <linux-sgx@...r.kernel.org>,
        "jarkko@...nel.org" <jarkko@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Van Bulck, Jo" <jo.vanbulck@...kuleuven.be>
CC:     "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>
Subject: Re: [PATCH 5/8] selftests/sgx: Include memory clobber for inline asm
 in test enclave

On Tue, 2023-08-08 at 12:31 -0700, Jo Van Bulck wrote:
> Add the "memory" clobber to the EMODPE and EACCEPT asm blocks to tell the
> compiler the assembly code accesses to the secinfo struct. This ensures
> the compiler treats the asm block as a memory barrier and the write to
> secinfo will be visible to ENCLU.
> 
> Signed-off-by: Jo Van Bulck <jo.vanbulck@...kuleuven.be>
> ---
>  tools/testing/selftests/sgx/test_encl.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/testing/selftests/sgx/test_encl.c b/tools/testing/selftests/sgx/test_encl.c
> index c71dfbadd2d9..5b758eaf808c 100644
> --- a/tools/testing/selftests/sgx/test_encl.c
> +++ b/tools/testing/selftests/sgx/test_encl.c
> @@ -24,10 +24,11 @@ static void do_encl_emodpe(void *_op)
>  	secinfo.flags = op->flags;
>  
>  	asm volatile(".byte 0x0f, 0x01, 0xd7"
> -				:
> +				: /* no outputs */
>  				: "a" (EMODPE),
>  				  "b" (&secinfo),
> -				  "c" (op->epc_addr));
> +				  "c" (op->epc_addr)
> +				: "memory" /* read from secinfo pointer */);
>  }
>  
>  static void do_encl_eaccept(void *_op)
> @@ -42,7 +43,8 @@ static void do_encl_eaccept(void *_op)
>  				: "=a" (rax)
>  				: "a" (EACCEPT),
>  				  "b" (&secinfo),
> -				  "c" (op->epc_addr));
> +				  "c" (op->epc_addr)
> +				: "memory" /* read from secinfo pointer */);
>  
>  	op->ret = rax;
>  }

Reviewed-by: Kai Huang <kai.huang@...el.com>