From patchwork Mon Jun 1 01:16:41 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jarkko Sakkinen X-Patchwork-Id: 11581073 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 30865139A for ; Mon, 1 Jun 2020 01:20:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 226DE206C3 for ; Mon, 1 Jun 2020 01:20:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727875AbgFABU3 (ORCPT ); Sun, 31 May 2020 21:20:29 -0400 Received: from mga05.intel.com ([192.55.52.43]:47602 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726555AbgFABU3 (ORCPT ); Sun, 31 May 2020 21:20:29 -0400 IronPort-SDR: eoZR1DiFtby6rOzhU4PjQzvWJJnOW7li3oviDxXeJcMIzk+teu1e5jhX6i43G3cekADVLOCi9E 3Bz17FaI+8Eg== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga003.jf.intel.com ([10.7.209.27]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 31 May 2020 18:20:28 -0700 IronPort-SDR: W9DBeI5Lu7qXxGoBjQwhuJz9m5fUkqs924TL5c8EBogajiV8RX2iWQrBQoZT9lG2gx190mMMQK zWCO/NnsY0pA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,459,1583222400"; d="scan'208";a="268157344" Received: from hbetts-mobl.ger.corp.intel.com (HELO localhost) ([10.252.59.178]) by orsmga003.jf.intel.com with ESMTP; 31 May 2020 18:20:19 -0700 From: Jarkko Sakkinen To: linux-kernel@vger.kernel.org, x86@kernel.org, linux-sgx@vger.kernel.org Cc: Sean Christopherson , Andy Lutomirski , Jethro Beekman , Jarkko Sakkinen , akpm@linux-foundation.org, andriy.shevchenko@linux.intel.com, asapek@google.com, bp@alien8.de, cedric.xing@intel.com, chenalexchen@google.com, conradparker@google.com, cyhanish@google.com, dave.hansen@intel.com, haitao.huang@intel.com, josh@joshtriplett.org, kai.huang@intel.com, kai.svahn@intel.com, kmoy@google.com, ludloff@google.com, luto@kernel.org, nhorman@redhat.com, npmccallum@redhat.com, puiterwijk@redhat.com, rientjes@google.com, tglx@linutronix.de, yaozhangx@google.com Subject: [PATCH v31 17/21] x86/traps: Attempt to fixup exceptions in vDSO before signaling Date: Mon, 1 Jun 2020 04:16:41 +0300 Message-Id: <20200601011645.794040-18-jarkko.sakkinen@linux.intel.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200601011645.794040-1-jarkko.sakkinen@linux.intel.com> References: <20200601011645.794040-1-jarkko.sakkinen@linux.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 From: Sean Christopherson vDSO functions can now leverage an exception fixup mechanism similar to kernel exception fixup. For vDSO exception fixup, the initial user is Intel's Software Guard Extensions (SGX), which will wrap the low-level transitions to/from the enclave, i.e. EENTER and ERESUME instructions, in a vDSO function and leverage fixup to intercept exceptions that would otherwise generate a signal. This allows the vDSO wrapper to return the fault information directly to its caller, obviating the need for SGX applications and libraries to juggle signal handlers. Attempt to fixup vDSO exceptions immediately prior to populating and sending signal information. Except for the delivery mechanism, an exception in a vDSO function should be treated like any other exception in userspace, e.g. any fault that is successfully handled by the kernel should not be directly visible to userspace. Although it's debatable whether or not all exceptions are of interest to enclaves, defer to the vDSO fixup to decide whether to do fixup or generate a signal. Future users of vDSO fixup, if there ever are any, will undoubtedly have different requirements than SGX enclaves, e.g. the fixup vs. signal logic can be made function specific if/when necessary. Suggested-by: Andy Lutomirski Acked-by: Jethro Beekman Signed-off-by: Sean Christopherson Signed-off-by: Jarkko Sakkinen --- arch/x86/kernel/traps.c | 14 ++++++++++++++ arch/x86/mm/fault.c | 8 ++++++++ 2 files changed, 22 insertions(+) diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index d54cffdc7cac..cce8fb2c560d 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -57,6 +57,7 @@ #include #include #include +#include #ifdef CONFIG_X86_64 #include @@ -206,6 +207,9 @@ do_trap_no_signal(struct task_struct *tsk, int trapnr, const char *str, tsk->thread.error_code = error_code; tsk->thread.trap_nr = trapnr; die(str, regs, error_code); + } else { + if (fixup_vdso_exception(regs, trapnr, error_code, 0)) + return 0; } /* @@ -538,6 +542,9 @@ dotraplinkage void do_general_protection(struct pt_regs *regs, long error_code) tsk->thread.error_code = error_code; tsk->thread.trap_nr = X86_TRAP_GP; + if (fixup_vdso_exception(regs, X86_TRAP_GP, error_code, 0)) + return; + show_signal(tsk, SIGSEGV, "", desc, regs, error_code); force_sig(SIGSEGV); @@ -791,6 +798,10 @@ dotraplinkage void do_debug(struct pt_regs *regs, long error_code) SIGTRAP) == NOTIFY_STOP) goto exit; + if (user_mode(regs) && + fixup_vdso_exception(regs, X86_TRAP_DB, error_code, 0)) + goto exit; + /* * Let others (NMI) know that the debug stack is in use * as we may switch to the interrupt stack. @@ -871,6 +882,9 @@ static void math_error(struct pt_regs *regs, int error_code, int trapnr) if (!si_code) return; + if (fixup_vdso_exception(regs, trapnr, error_code, 0)) + return; + force_sig_fault(SIGFPE, si_code, (void __user *)uprobe_get_trap_addr(regs)); } diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 23666e34abbc..e9ed3c7299ac 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -30,6 +30,7 @@ #include /* store_idt(), ... */ #include /* exception stack */ #include /* VMALLOC_START, ... */ +#include /* fixup_vdso_exception() */ #define CREATE_TRACE_POINTS #include @@ -924,6 +925,10 @@ __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code, sanitize_error_code(address, &error_code); + if (fixup_vdso_exception(regs, X86_TRAP_PF, error_code, + address)) + return; + if (likely(show_unhandled_signals)) show_signal_msg(regs, error_code, address, tsk); @@ -1041,6 +1046,9 @@ do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address, sanitize_error_code(address, &error_code); + if (fixup_vdso_exception(regs, X86_TRAP_PF, error_code, address)) + return; + set_signal_archinfo(address, error_code); #ifdef CONFIG_MEMORY_FAILURE