From patchwork Thu Mar 19 01:11:25 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sean Christopherson X-Patchwork-Id: 11446371 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id BC59B139A for ; Thu, 19 Mar 2020 01:11:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A6BAD20767 for ; Thu, 19 Mar 2020 01:11:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726913AbgCSBLi (ORCPT ); Wed, 18 Mar 2020 21:11:38 -0400 Received: from mga18.intel.com ([134.134.136.126]:30444 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726623AbgCSBLi (ORCPT ); Wed, 18 Mar 2020 21:11:38 -0400 IronPort-SDR: BPZ1aPCSBEKTV6oUVwKCja2P07GhY660SDjzTVQnmKAPrvZunEah/YT0MxymqKl/25aqaRDRJn 8xo8nv1xFQOg== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Mar 2020 18:11:35 -0700 IronPort-SDR: 2OMASfcLXZySzdeklV+BTJ25+hSfvPWnSoV2ImPGxVo+7DGk99DdWg9PNcFcUq6NnJzCyXg+mo 26q5UP8Z/oAw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,569,1574150400"; d="scan'208";a="324358697" Received: from sjchrist-coffee.jf.intel.com ([10.54.74.202]) by orsmga001.jf.intel.com with ESMTP; 18 Mar 2020 18:11:35 -0700 From: Sean Christopherson To: Jarkko Sakkinen Cc: Nathaniel McCallum , Cedric Xing , Jethro Beekman , Andy Lutomirski , linux-sgx@vger.kernel.org Subject: [PATCH for_v29 3/8] x86/sgx: vdso: Make __vdso_sgx_enter_enclave() callable from C code Date: Wed, 18 Mar 2020 18:11:25 -0700 Message-Id: <20200319011130.8556-4-sean.j.christopherson@intel.com> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20200319011130.8556-1-sean.j.christopherson@intel.com> References: <20200319011130.8556-1-sean.j.christopherson@intel.com> MIME-Version: 1.0 Sender: linux-sgx-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-sgx@vger.kernel.org Make __vdso_sgx_enter_enclave() callable from C by preserving %rbx and taking @leaf in %rcx instead of %rax. Being able to invoke the vDSO from C reduces the overhead of runtimes that are tightly coupled with their enclaves, e.g. that can rely on the enclave to save and restore non-volatile registers, as the runtime doesn't need an assembly wrapper to preserve non-volatile registers and/or shuffle stack arguments. Note, both %rcx and %rbx are consumed by EENTER/ERESUME, i.e. consuming them doesn't violate the primary tenet of __vdso_sgx_enter_enclave() that "thou shalt not restrict how information is exchanged between an enclave and its host process". Suggested-by: Nathaniel McCallum Cc: Cedric Xing Cc: Jethro Beekman Cc: Andy Lutomirski Cc: linux-sgx@vger.kernel.org Signed-off-by: Sean Christopherson --- Cedric, please go to town on this, you're much better at the userspace stack and debugging interactions, e.g. I don't think the CFA directives need updating, but my knowledge of that stuff is skeeetchy. Note, if the previous patch to make the %rsp restoration relative is dropped, then %rbx should be restored relative to %rbp instead of %rsp. arch/x86/entry/vdso/vsgx_enter_enclave.S | 33 ++++++++++++++---------- 1 file changed, 19 insertions(+), 14 deletions(-) diff --git a/arch/x86/entry/vdso/vsgx_enter_enclave.S b/arch/x86/entry/vdso/vsgx_enter_enclave.S index 14f07d5e47ae..7a0565476a29 100644 --- a/arch/x86/entry/vdso/vsgx_enter_enclave.S +++ b/arch/x86/entry/vdso/vsgx_enter_enclave.S @@ -16,25 +16,25 @@ /** * __vdso_sgx_enter_enclave() - Enter an SGX enclave + * @rdi: Pass-through value for RDI + * @rsi: Pass-through value for RSI + * @rdx: Pass-through value for RDX * @leaf: ENCLU leaf, must be EENTER or ERESUME + * @r8: Pass-through value for R8 + * @r9: Pass-through value for R9 * @tcs: TCS, must be non-NULL * @e: Optional struct sgx_enclave_exception instance * @handler: Optional enclave exit handler * - * **Important!** __vdso_sgx_enter_enclave() is **NOT** compliant with the - * x86-64 ABI, i.e. cannot be called from standard C code. - * - * Input ABI: - * @leaf %eax - * @tcs 8(%rsp) - * @e 0x10(%rsp) - * @handler 0x18(%rsp) - * - * Output ABI: - * @ret %eax + * **Important!** __vdso_sgx_enter_enclave() does not ensure full compliance + * with the x86-64 ABI, e.g. doesn't explicitly clear EFLAGS.DF after EEXIT. + * Except for non-volatile general purpose registers, preserving/setting state + * in accordance with the x86-64 ABI is the responsibility of the enclave and + * its runtime, i.e. __vdso_sgx_enter_enclave() cannot be called from C code + * without careful consideration by both the enclave and its runtime. * * All general purpose registers except RAX, RBX and RCX are passed as-is to - * the enclave. RAX, RBX and RCX are consumed by EENTER and ERESUME and are + * the enclave. RAX, RBX and RCX are consumed by EENTER and ERESUME and are * loaded with @leaf, asynchronous exit pointer, and @tcs respectively. * * RBP and the stack are used to anchor __vdso_sgx_enter_enclave() to the @@ -70,9 +70,11 @@ */ #ifdef SGX_KERNEL_DOC /* C-style function prototype to coerce kernel-doc into parsing the comment. */ -int __vdso_sgx_enter_enclave(int leaf, void *tcs, +int __vdso_sgx_enter_enclave(unsigned long rdi, unsigned long rsi, + unsigned long rdx, unsigned int leaf, + unsigned long r8, unsigned long r9, void *tcs, struct sgx_enclave_exception *e, - sgx_enclave_exit_handler_t handler); + sgx_enclave_exit_handler_t handler) #endif SYM_FUNC_START(__vdso_sgx_enter_enclave) /* Prolog */ @@ -82,7 +84,9 @@ SYM_FUNC_START(__vdso_sgx_enter_enclave) .cfi_rel_offset %rbp, 0 mov %rsp, %rbp .cfi_def_cfa_register %rbp + push %rbx + mov %ecx, %eax .Lenter_enclave: /* EENTER <= leaf <= ERESUME */ cmp $0x2, %eax @@ -108,6 +112,7 @@ SYM_FUNC_START(__vdso_sgx_enter_enclave) jne .Linvoke_userspace_handler .Lout: + pop %rbx leave .cfi_def_cfa %rsp, 8 ret