From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7DB7FECE599 for ; Wed, 16 Oct 2019 22:24:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5962E2168B for ; Wed, 16 Oct 2019 22:24:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732792AbfJPWYz (ORCPT ); Wed, 16 Oct 2019 18:24:55 -0400 Received: from mga11.intel.com ([192.55.52.93]:29212 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730762AbfJPWYz (ORCPT ); Wed, 16 Oct 2019 18:24:55 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by fmsmga102.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 16 Oct 2019 15:24:54 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.67,305,1566889200"; d="scan'208";a="186294194" Received: from bxing-desk.ccr.corp.intel.com (HELO [134.134.148.187]) ([134.134.148.187]) by orsmga007.jf.intel.com with ESMTP; 16 Oct 2019 15:24:54 -0700 Subject: Re: [PATCH for_v23 4/5] x86/vdso: sgx: Reorder params to callback to improve readability To: Sean Christopherson , Jarkko Sakkinen Cc: linux-sgx@vger.kernel.org References: <20191011004059.28581-1-sean.j.christopherson@intel.com> <20191011004059.28581-5-sean.j.christopherson@intel.com> From: "Xing, Cedric" Message-ID: <34e9c245-34d5-fbd3-6d50-deac4adc29f6@intel.com> Date: Wed, 16 Oct 2019 15:24:54 -0700 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <20191011004059.28581-5-sean.j.christopherson@intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-sgx-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-sgx@vger.kernel.org On 10/10/2019 5:40 PM, Sean Christopherson wrote: > Swap @ret and @ursp in the callback prototype so that the output from > the vDSO itself, @ret and @e, are grouped together. Having the first > N parameters all share a type also makes the prototype easier to parse > by (some) humans. And, passing @ursp via register saves one whole > MOV instruction! > > Signed-off-by: Sean Christopherson > --- > arch/x86/entry/vdso/vsgx_enter_enclave.S | 16 +++++++--------- > arch/x86/include/uapi/asm/sgx.h | 10 +++++----- > 2 files changed, 12 insertions(+), 14 deletions(-) > > diff --git a/arch/x86/entry/vdso/vsgx_enter_enclave.S b/arch/x86/entry/vdso/vsgx_enter_enclave.S > index 3dd22780b7ef..94f613b53b13 100644 > --- a/arch/x86/entry/vdso/vsgx_enter_enclave.S > +++ b/arch/x86/entry/vdso/vsgx_enter_enclave.S > @@ -134,23 +134,21 @@ ENTRY(__vdso_sgx_enter_enclave) > jmp .Lhandle_exit > > .Linvoke_userspace_handler: > + /* Pass the untrusted RSP (at exit) to the callback via %rcx. */ > + mov %rsp, %rcx > + > /* > - * Align stack per x86_64 ABI. Save the original %rsp in %rbx to be > - * restored after the callback returns. Note, %rsp needs to be 16-byte > - * aligned _after_ pushing the three parameters on the stack. > + * Align stack per x86_64 ABI. Note, %rsp needs to be 16-byte aligned > + * _after_ pushing the three parameters on the stack. > */ > - mov %rsp, %rbx Per x86_64 ABI, %rcx is _not_ preserved across function call. How are you going to restore the stack after callback returns? > and $-0x10, %rsp > sub $0x8, %rsp Usually compilers would just use a 1-byte "push" instead of a 4-byte "sub" instruction here. > > - /* Push @e, u_rsp and @tcs as parameters to the callback. */ > + /* Push @e, the "return" value and @tcs as params to the callback. */ > push 0x18(%rbp) > - push %rbx > + push %rax > push 0x10(%rbp) > > - /* Pass the "return" value to the callback via %rcx. */ > - mov %eax, %ecx > - > /* Clear RFLAGS.DF per x86_64 ABI */ > cld > > diff --git a/arch/x86/include/uapi/asm/sgx.h b/arch/x86/include/uapi/asm/sgx.h > index 255392f5054f..95f69f938b58 100644 > --- a/arch/x86/include/uapi/asm/sgx.h > +++ b/arch/x86/include/uapi/asm/sgx.h > @@ -88,16 +88,16 @@ struct sgx_enclave_exception { > * @rdi: RDI at the time of enclave exit > * @rsi: RSI at the time of enclave exit > * @rdx: RDX at the time of enclave exit > - * @ret: 0 on success (EEXIT), -EFAULT on an exception > + * @ursp: RSP at the time of enclave exit (untrusted stack) > * @r8: R8 at the time of enclave exit > * @r9: R9 at the time of enclave exit > * @tcs: Thread Control Structure used to enter enclave > - * @ursp: RSP at the time of enclave exit > + * @ret: 0 on success (EEXIT), -EFAULT on an exception > * @e: Pointer to struct sgx_enclave_exception (as provided by caller) > */ > -typedef int (*sgx_enclave_exit_handler_t)(long rdi, long rsi, long rdx, int ret, > - long r8, long r9, void *tcs, > - long ursp, > +typedef int (*sgx_enclave_exit_handler_t)(long rdi, long rsi, long rdx, > + long ursp, long r8, long r9, > + void *tcs, int ret, > struct sgx_enclave_exception *e); > > #endif /* _UAPI_ASM_X86_SGX_H */ >