linux-kernel - Re: [PATCH v4 12/13] selftests/sgx: Remove redundant enclave base address save/restore

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Message-ID: <54cc090bad89351862fa67c97d681e411336e2be.camel@intel.com>
Date:   Tue, 29 Aug 2023 11:00:35 +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 v4 12/13] selftests/sgx: Remove redundant enclave base
 address save/restore

On Fri, 2023-08-25 at 15:32 +0200, Jo Van Bulck wrote:
> Remove redundant push/pop pair that stores and restores the enclave base
> address in the test enclave, as it is never used after the pop and can
> anyway be easily retrieved via the __encl_base symbol.
> 
> Signed-off-by: Jo Van Bulck <jo.vanbulck@...kuleuven.be>

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

Nit below...

> ---
>  tools/testing/selftests/sgx/test_encl_bootstrap.S | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/tools/testing/selftests/sgx/test_encl_bootstrap.S b/tools/testing/selftests/sgx/test_encl_bootstrap.S
> index 4e55d91566c4..28fe5d2ac0af 100644
> --- a/tools/testing/selftests/sgx/test_encl_bootstrap.S
> +++ b/tools/testing/selftests/sgx/test_encl_bootstrap.S
> @@ -58,12 +58,9 @@ encl_entry_core:
>  	push	%rax
>  
>  	push	%rcx # push the address after EENTER
> -	push	%rbx # push the enclave base address
>  
>  	call	encl_body
>  
> -	pop	%rbx # pop the enclave base address
> -
>  	/* Clear volatile GPRs, except RAX (EEXIT function). */
>  	xor     %rcx, %rcx
>  	xor     %rdx, %rdx

... please move this patch before patch 2?

Otherwise, strictly speaking patch 2 isn't complete, because after you apply
patch 2 you still have this code which is obviously wrong -- %rbx is no longer
enclave base address (although it never was even in the current upstream code).