Re: [RFC PATCH 3/4] x86/vdso: x86/sgx: Introduce dedicated SGX exit reasons for vDSO

[Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>]

On Mon, Aug 17, 2020 at 09:24:04PM -0700, Sean Christopherson wrote:
> Use dedicated exit reasons, e.g. SYNCHRONOUS and EXCEPTION, instead of
> '0' and '-EFAULT' respectively.  Using -EFAULT is less than desirable as
> it usually means "bad address", which may or may not be true for a fault
> in the enclave or on ENCLU.
> 
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> ---
>  arch/x86/entry/vdso/vsgx_enter_enclave.S | 7 +++++--
>  arch/x86/include/uapi/asm/sgx.h          | 3 +++
>  2 files changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/entry/vdso/vsgx_enter_enclave.S b/arch/x86/entry/vdso/vsgx_enter_enclave.S
> index aaae6d6e28ac3..b09e87dbe9334 100644
> --- a/arch/x86/entry/vdso/vsgx_enter_enclave.S
> +++ b/arch/x86/entry/vdso/vsgx_enter_enclave.S
> @@ -19,6 +19,9 @@
>  /* #define USER_DATA_OFFSET	4*8 */
>  #define EXCEPTION_OFFSET	5*8
>  
> +#define SGX_SYNCHRONOUS_EXIT	0
> +#define SGX_EXCEPTION_EXIT	1
> +
>  /* Offsets into sgx_enter_enclave.exception. */
>  #define EX_TRAPNR	0*8
>  #define EX_ERROR_CODE	0*8+2
> @@ -65,7 +68,7 @@ SYM_FUNC_START(__vdso_sgx_enter_enclave)
>  	mov	RUN_OFFSET(%rbp), %rbx
>  
>  	/* Set exit_reason. */
> -	movl	$0, EXIT_REASON_OFFSET(%rbx)
> +	movl	$SGX_SYNCHRONOUS_EXIT, EXIT_REASON_OFFSET(%rbx)
>  
>  	/* Invoke userspace's exit handler if one was provided. */
>  .Lhandle_exit:
> @@ -94,7 +97,7 @@ SYM_FUNC_START(__vdso_sgx_enter_enclave)
>  	mov	RUN_OFFSET(%rbp), %rbx
>  
>  	/* Set the exit_reason and exception info. */
> -	movl	$(-EFAULT), EXIT_REASON_OFFSET(%rbx)
> +	movl	$SGX_EXCEPTION_EXIT, EXIT_REASON_OFFSET(%rbx)
>  
>  	mov	%di,  (EXCEPTION_OFFSET + EX_TRAPNR)(%rbx)
>  	mov	%si,  (EXCEPTION_OFFSET + EX_ERROR_CODE)(%rbx)
> diff --git a/arch/x86/include/uapi/asm/sgx.h b/arch/x86/include/uapi/asm/sgx.h
> index d3b107aac279d..80a8b7a949a23 100644
> --- a/arch/x86/include/uapi/asm/sgx.h
> +++ b/arch/x86/include/uapi/asm/sgx.h
> @@ -74,6 +74,9 @@ struct sgx_enclave_set_attribute {
>  	__u64 attribute_fd;
>  };
>  
> +#define SGX_SYNCHRONOUS_EXIT	0
> +#define SGX_EXCEPTION_EXIT	1

enum would be great here.

> +
>  struct sgx_enclave_run;
>  
>  /**
> -- 
> 2.28.0
> 

/Jarkko