From patchwork Sat Jul 13 06:51:26 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Xing, Cedric" X-Patchwork-Id: 11042907 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id C0308912 for ; Sat, 13 Jul 2019 06:51:33 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id AC937284F5 for ; Sat, 13 Jul 2019 06:51:33 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 9F32028541; Sat, 13 Jul 2019 06:51:33 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 91286284F5 for ; Sat, 13 Jul 2019 06:51:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727617AbfGMGva (ORCPT ); Sat, 13 Jul 2019 02:51:30 -0400 Received: from mga11.intel.com ([192.55.52.93]:55267 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726274AbfGMGv3 (ORCPT ); Sat, 13 Jul 2019 02:51:29 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga004.jf.intel.com ([10.7.209.38]) by fmsmga102.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 12 Jul 2019 23:51:28 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.63,485,1557212400"; d="scan'208";a="318200504" Received: from bxing-ubuntu.jf.intel.com ([10.23.30.27]) by orsmga004.jf.intel.com with ESMTP; 12 Jul 2019 23:51:27 -0700 From: Cedric Xing To: linux-kernel@vger.kernel.org, linux-sgx@vger.kernel.org, jarkko.sakkinen@linux.intel.com Cc: cedric.xing@intel.com, akpm@linux-foundation.org, dave.hansen@intel.com, sean.j.christopherson@intel.com, serge.ayoun@intel.com, shay.katz-zamir@intel.com, haitao.huang@intel.com, kai.svahn@intel.com, kai.huang@intel.com Subject: [RFC PATCH v4 2/3] x86/vdso: Modify __vdso_sgx_enter_enclave() to allow parameter passing on untrusted stack Date: Fri, 12 Jul 2019 23:51:26 -0700 Message-Id: X-Mailer: git-send-email 2.17.1 In-Reply-To: References: In-Reply-To: References: Sender: linux-sgx-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-sgx@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP The previous __vdso_sgx_enter_enclave() requires enclaves to preserve %rsp, which prohibits enclaves from allocating and passing parameters for untrusted function calls (aka. o-calls) on the untrusted stack. This patch addresses the problem above by introducing a new ABI that preserves %rbp instead of %rsp. Then __vdso_sgx_enter_enclave() can anchor its frame using %rbp so that enclaves are allowed to allocate space on the untrusted stack by decrementing %rsp. Please note that the stack space allocated in such way will be part of __vdso_sgx_enter_enclave()'s frame so will be freed after __vdso_sgx_enter_enclave() returns. Therefore, __vdso_sgx_enter_enclave() has been revised to take a callback function as an optional parameter, which if supplied, will be invoked upon enclave exits (both AEX (Asynchronous Enclave eXit) and normal exits), with the value of %rsp left off by the enclave as a parameter to the callback. Here's the summary of API/ABI changes in this patch. More details could be found in arch/x86/entry/vdso/vsgx_enter_enclave.S. * 'struct sgx_enclave_exception' is renamed to 'struct sgx_enclave_exinfo' because it is filled upon both AEX (i.e. exceptions) and normal enclave exits. * __vdso_sgx_enter_enclave() anchors its frame using %rbp (instead of %rsp in the previous implementation). * __vdso_sgx_enter_enclave() takes one more parameter - a callback function to be invoked upon enclave exits. This callback is optional, and if not supplied, will cause __vdso_sgx_enter_enclave() to return upon enclave exits (same behavior as previous implementation). * The callback function is given as a parameter the value of %rsp at enclave exit to address data "pushed" by the enclave. A positive value returned by the callback will be treated as an ENCLU leaf for re-entering the enclave, while a zero or negative value will be passed through as the return value of __vdso_sgx_enter_enclave() to its caller. It's also safe to leave callback by longjmp() or by throwing a C++ exception. Signed-off-by: Cedric Xing --- arch/x86/entry/vdso/vsgx_enter_enclave.S | 310 +++++++++++++++++------ arch/x86/include/uapi/asm/sgx.h | 14 +- 2 files changed, 242 insertions(+), 82 deletions(-) diff --git a/arch/x86/entry/vdso/vsgx_enter_enclave.S b/arch/x86/entry/vdso/vsgx_enter_enclave.S index fe0bf6671d6d..a96542ba6945 100644 --- a/arch/x86/entry/vdso/vsgx_enter_enclave.S +++ b/arch/x86/entry/vdso/vsgx_enter_enclave.S @@ -6,96 +6,256 @@ #include "extable.h" -#define EX_LEAF 0*8 -#define EX_TRAPNR 0*8+4 -#define EX_ERROR_CODE 0*8+6 -#define EX_ADDRESS 1*8 +#define EX_LEAF 0*8 +#define EX_TRAPNR 0*8+4 +#define EX_ERROR_CODE 0*8+6 +#define EX_ADDRESS 1*8 .code64 .section .text, "ax" #ifdef SGX_KERNEL_DOC /** - * __vdso_sgx_enter_enclave() - Enter an SGX enclave + * typedef sgx_ex_callback - Callback function for __vdso_sgx_enter_enclave() * - * @leaf: **IN \%eax** - ENCLU leaf, must be EENTER or ERESUME - * @tcs: **IN \%rbx** - TCS, must be non-NULL - * @ex_info: **IN \%rcx** - Optional 'struct sgx_enclave_exception' pointer + * @rdi: value of %%rdi register at enclave exit + * @rsi: value of %%rsi register at enclave exit + * @rdx: value of %%rdx register at enclave exit + * @exinfo: pointer to a sgx_enclave_exinfo structure, which was passed to + * __vdso_sgx_enter_enclave() as input + * @r8: value of %%r8 register at enclave exit + * @r9: value of %%r9 register at enclave exit + * @tcs: TCS used by __vdso_sgx_enter_enclave() to enter the enclave, + * could be used to re-enter the + * enclave + * @ursp: value of %%rsp register at enclave exit + * + * This is the callback function to be invoked upon enclave exits, including + * normal exits (as result of EEXIT), and asynchronous exits (AEX) due to + * exceptions occurred at EENTER or within the enclave. + * + * This callback is expected to follow x86_64 ABI. * * Return: - * **OUT \%eax** - - * %0 on a clean entry/exit to/from the enclave, %-EINVAL if ENCLU leaf is - * not allowed or if TCS is NULL, %-EFAULT if ENCLU or the enclave faults - * - * **Important!** __vdso_sgx_enter_enclave() is **NOT** compliant with the - * x86-64 ABI, i.e. cannot be called from standard C code. As noted above, - * input parameters must be passed via ``%eax``, ``%rbx`` and ``%rcx``, with - * the return value passed via ``%eax``. All registers except ``%rsp`` must - * be treated as volatile from the caller's perspective, including but not - * limited to GPRs, EFLAGS.DF, MXCSR, FCW, etc... Conversely, the enclave - * being run **must** preserve the untrusted ``%rsp`` and stack. + * + * EENTER(2) - causes __vdso_sgx_enter_enclave() to issue ENCLU[EENTER] on the + * same TCS. All GPRs left off by this callback function will be passed through + * back to the enclave, except %%rax, %%rbx and %%rcx, which are clobbered by + * ENCLU[EENTER] instruction. + * + * ERESUME(3) - causes __vdso_sgx_enter_enclave() to issue ENCLU[ERESUME] on + * the same TCS. + * + * 0 (zero) or negative returned values will be returned back to + * __vdso_sgx_enter_enclave()'s caller as is. + * + * All other values will cause -EINVAL to be returned to + * __vdso_sgx_enter_enclave()'s caller. + * + * Note: All general purpose registers (GPRs) left off by the enclave are + * passed through to this function, except %%rax, %%rbx and %%rcx, which are + * used internally by __vdso_sgx_enter_enclave(). Some of those registers are + * accessible as function parameters (i.e. @rdi, @rsi, @rdx, @r8, @r9 and + * @ursp), while others can be accessed only from assembly code. */ -__vdso_sgx_enter_enclave(u32 leaf, void *tcs, - struct sgx_enclave_exception *ex_info) -{ - if (leaf != SGX_EENTER && leaf != SGX_ERESUME) - return -EINVAL; +typedef int sgx_ex_callback(long rdi, long rsi, long rdx, + struct sgx_enclave_exinfo *exinfo, + long r8, long r9, void *tcs, long ursp); - if (!tcs) - return -EINVAL; +/** + * __vdso_sgx_enter_enclave() - Enter an SGX enclave and capture exceptions + * + * @leaf: + * passed in %%eax, must be either EENTER(2) or ERESUME(3) + * @tcs: + * passed on stack at 8(%%rsp), is the linear address of TCS + * @exinfo: + * passed on stack at 0x10(%%rsp), optional, and if non-NULL, shall point + * to an sgx_enclave_exinfo structure to receive information about the + * enclave exit + * @callback: + * passed on stack at 0x18(%%rsp), optional, and if non-NULL, points to a + * callback function to be invoked at enclave exits + * + * __vdso_sgx_enter_enclave() issues either ENCLU[EENTER] or ENCLU[ERESUME] on + * @tcs depending on @leaf. + * + * IMPORTANT! This API is not compliant with x86-64 ABI but adopts a + * proprietary calling convention. Please see NOTES section below for details. + * + * On an enclave exit, @exinfo->leaf will be set to the ENCLU leaf at exit, if + * @exinfo is not NULL. That is, @exinfo->leaf may be one of the following: + * + * * EEXIT: Normal exit due to ENCLU[EEXIT] within the enclave. All other + * members will remain intact. + * + * * ERESUME: Asynchronous exit due to exceptions within the enclave. + * @exinfo->trapnr, @exinfo->error_code and @exinfo->address are + * set to the trap number, error code and fault address, + * respectively. + * + * * EENTER: Exception occurred when trying to enter the enclave. + * @exinfo->trapnr, @exinfo->error_code and @exinfo->address are + * set to the trap number, error code and fault address, + * accordingly. + * + * If @callback is NULL, 0 (zero) is returned if the enclave has been entered + * and exited normally, or -EFAULT if any exception has occurred, or -EINVAL if + * @leaf on input is neither EENTER or ERESUME. + * + * If @callback is not NULL, it is invoked at enclave exit, and then actions + * will be taken depending on its return value - i.e. positive value will be + * treated as ENCLU leaf to re-enter the enclave, while 0 (zero) or negative + * values will be returned back to the caller as is. Unrecognized leaf values + * will cause -EINVAL to be returned. + * + * Return: + * + * 0 (zero) is returned on a successful entry and normal exit from the enclave. + * + * -EINVAL is returned if @leaf is neither EENTER nor ERESUME, or if @callback + * is not NULL and returns a positive value that is neither EENTER nor ERESUME + * after the enclave exits. + * + * -EFAULT is returned if an exception has occurred at EENTER or during + * execution of the enclave and @callback is NULL, or if @callback is not NULL + * and it returns -EFAULT after the enclave exits. + * + * Other values may be returned as the return value from @callback if it is not + * NULL. + * + * Note: __vdso_sgx_enter_enclave() adopts a proprietary calling convention, + * described below: + * + * * As noted above, input parameters are passed via %%eax and the stack. + * + * * %%rbx and %%rcx must be treated as volatile as they are modified as part + * of enclaves transitions and are used as scratch regs. + * + * * %%rdx, %%rdi, %%rsi and %%r8-%%r15 are passed as is and may be freely + * modified by the enclave. Values left in those registers will not be + * altered either, so will be visiable to the callback or the caller (if no + * callback is specified). + * + * * %%rsp could be decremented by the enclave to allocate temporary space on + * the untrusted stack. Temporary space allocated this way is retained in + * the context of @callback, and will be freed (i.e. %%rsp will be + * restored) before __vdso_sgx_enter_enclave() returns. + */ +int __vdso_sgx_enter_enclave(int leaf, void *tcs, + struct sgx_enclave_exinfo *exinfo, + sgx_ex_callback *callback); +{ + while (leaf == EENTER || leaf == ERESUME) { + int rc; + try { + ENCLU[leaf]; + rc = 0; + if (exinfo) + exinfo->leaf = EEXIT; + } catch (exception) { + rc = -EFAULT; + if (exinfo) + *exinfo = exception; + } - try { - ENCLU[leaf]; - } catch (exception) { - if (e) - *e = exception; - return -EFAULT; - } + leaf = !callback ? rc: (*callback)(rdi, rsi, rdx, exinfo, + r8, r9, tcs, ursp); + } - return 0; + return leaf > 0 ? -EINVAL : leaf; } #endif + ENTRY(__vdso_sgx_enter_enclave) - /* EENTER <= leaf <= ERESUME */ - cmp $0x2, %eax - jb bad_input - - cmp $0x3, %eax - ja bad_input - - /* TCS must be non-NULL */ - test %rbx, %rbx - je bad_input - - /* Save @exception_info */ - push %rcx - - /* Load AEP for ENCLU */ - lea 1f(%rip), %rcx -1: enclu - - add $0x8, %rsp - xor %eax, %eax - ret - -bad_input: - mov $(-EINVAL), %rax - ret - -.pushsection .fixup, "ax" - /* Re-load @exception_info and fill it (if it's non-NULL) */ -2: pop %rcx - test %rcx, %rcx - je 3f - - mov %eax, EX_LEAF(%rcx) - mov %di, EX_TRAPNR(%rcx) - mov %si, EX_ERROR_CODE(%rcx) - mov %rdx, EX_ADDRESS(%rcx) -3: mov $(-EFAULT), %rax - ret -.popsection - -_ASM_VDSO_EXTABLE_HANDLE(1b, 2b) + /* Prolog */ + .cfi_startproc + push %rbp + .cfi_adjust_cfa_offset 8 + .cfi_rel_offset %rbp, 0 + mov %rsp, %rbp + .cfi_def_cfa_register %rbp + +1: /* EENTER <= leaf <= ERESUME */ + cmp $0x2, %eax + jb 6f + cmp $0x3, %eax + ja 6f + + /* Load TCS and AEP */ + mov 0x10(%rbp), %rbx + lea 2f(%rip), %rcx + + /* Single ENCLU serving as both EENTER and AEP (ERESUME) */ +2: enclu + + /* EEXIT path */ + xor %ebx, %ebx +3: mov 0x18(%rbp), %rcx + jrcxz 4f + mov %eax, EX_LEAF(%rcx) + jnc 4f + mov %di, EX_TRAPNR(%rcx) + mov %si, EX_ERROR_CODE(%rcx) + mov %rdx, EX_ADDRESS(%rcx) + +4: /* Call *callback if supplied */ + mov 0x20(%rbp), %rax + test %rax, %rax + /* + * At this point, %ebx holds the effective return value, which shall be + * returned if no callback is specified + */ + cmovz %rbx, %rax + jz 7f + /* + * Align stack per x86_64 ABI. The original %rsp is saved in %rbx to be + * restored after *callback returns. + */ + mov %rsp, %rbx + and $-0x10, %rsp + /* Clear RFLAGS.DF per x86_64 ABI */ + cld + /* Parameters for *callback */ + push %rbx + push 0x10(%rbp) + /* Call *%rax via retpoline */ + call 40f + /* + * Restore %rsp to its original value left off by the enclave from last + * exit + */ + mov %rbx, %rsp + /* + * Positive return value from *callback will be interpreted as an ENCLU + * leaf, while a non-positive value will be interpreted as the return + * value to be passed back to the caller. + */ + jmp 1b +40: /* retpoline */ + call 42f +41: pause + lfence + jmp 41b +42: mov %rax, (%rsp) + ret + +5: /* Exception path */ + mov $-EFAULT, %ebx + stc + jmp 3b + +6: /* Unsupported ENCLU leaf */ + cmp $0, %eax + jle 7f + mov $-EINVAL, %eax + +7: /* Epilog */ + leave + .cfi_def_cfa %rsp, 8 + ret + .cfi_endproc + +_ASM_VDSO_EXTABLE_HANDLE(2b, 5b) ENDPROC(__vdso_sgx_enter_enclave) diff --git a/arch/x86/include/uapi/asm/sgx.h b/arch/x86/include/uapi/asm/sgx.h index 9ed690a38c70..50d2b5143e5e 100644 --- a/arch/x86/include/uapi/asm/sgx.h +++ b/arch/x86/include/uapi/asm/sgx.h @@ -24,7 +24,7 @@ /** * struct sgx_enclave_create - parameter structure for the - * %SGX_IOC_ENCLAVE_CREATE ioctl + * %SGX_IOC_ENCLAVE_CREATE ioctl * @src: address for the SECS page data */ struct sgx_enclave_create { @@ -33,7 +33,7 @@ struct sgx_enclave_create { /** * struct sgx_enclave_add_page - parameter structure for the - * %SGX_IOC_ENCLAVE_ADD_PAGE ioctl + * %SGX_IOC_ENCLAVE_ADD_PAGE ioctl * @addr: address within the ELRANGE * @src: address for the page data * @secinfo: address for the SECINFO data @@ -49,7 +49,7 @@ struct sgx_enclave_add_page { /** * struct sgx_enclave_init - parameter structure for the - * %SGX_IOC_ENCLAVE_INIT ioctl + * %SGX_IOC_ENCLAVE_INIT ioctl * @sigstruct: address for the SIGSTRUCT data */ struct sgx_enclave_init { @@ -66,16 +66,16 @@ struct sgx_enclave_set_attribute { }; /** - * struct sgx_enclave_exception - structure to report exceptions encountered in - * __vdso_sgx_enter_enclave() + * struct sgx_enclave_exinfo - structure to report exceptions encountered in + * __vdso_sgx_enter_enclave() * - * @leaf: ENCLU leaf from \%eax at time of exception + * @leaf: ENCLU leaf from \%eax at time of exception/exit * @trapnr: exception trap number, a.k.a. fault vector * @error_code: exception error code * @address: exception address, e.g. CR2 on a #PF * @reserved: reserved for future use */ -struct sgx_enclave_exception { +struct sgx_enclave_exinfo { __u32 leaf; __u16 trapnr; __u16 error_code;