From patchwork Tue Jul 7 03:02:00 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jarkko Sakkinen X-Patchwork-Id: 11647459 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 7172913B4 for ; Tue, 7 Jul 2020 03:06:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5BEA92070C for ; Tue, 7 Jul 2020 03:06:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728125AbgGGDGh (ORCPT ); Mon, 6 Jul 2020 23:06:37 -0400 Received: from mga02.intel.com ([134.134.136.20]:10488 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726434AbgGGDGg (ORCPT ); Mon, 6 Jul 2020 23:06:36 -0400 IronPort-SDR: cbfAGiZutHZS84Bct3rvTF7fdkqHDQSpidpbvD3JT2A5qRcLJ/qVWAZAC/2FaLAATkGook7MZr rSWYCWOyy7Hg== X-IronPort-AV: E=McAfee;i="6000,8403,9674"; a="135777230" X-IronPort-AV: E=Sophos;i="5.75,321,1589266800"; d="scan'208";a="135777230" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 06 Jul 2020 20:06:36 -0700 IronPort-SDR: Ak3sKcQ4szF5qLdSaKlt3pTTBeepKUbxr1uwrkpaayEhPwLhFz4oWat+i8Bir0nnH6ebbDgPJp xisbsDz/e7qw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.75,321,1589266800"; d="scan'208";a="388368952" Received: from apiccion-mobl1.ger.corp.intel.com (HELO localhost) ([10.249.45.178]) by fmsmga001.fm.intel.com with ESMTP; 06 Jul 2020 20:06:25 -0700 From: Jarkko Sakkinen To: x86@kernel.org, linux-sgx@vger.kernel.org Cc: linux-kernel@vger.kernel.org, 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 v34 20/24] x86/traps: Attempt to fixup exceptions in vDSO before signaling Date: Tue, 7 Jul 2020 06:02:00 +0300 Message-Id: <20200707030204.126021-21-jarkko.sakkinen@linux.intel.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200707030204.126021-1-jarkko.sakkinen@linux.intel.com> References: <20200707030204.126021-1-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 | 19 ++++++++++++++++--- arch/x86/mm/fault.c | 8 ++++++++ 2 files changed, 24 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index b038695f36c5..c2c306f81045 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -59,6 +59,7 @@ #include #include #include +#include #ifdef CONFIG_X86_64 #include @@ -117,6 +118,9 @@ 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; } /* @@ -548,6 +552,9 @@ DEFINE_IDTENTRY_ERRORCODE(exc_general_protection) 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); goto exit; @@ -829,9 +836,12 @@ static void handle_debug(struct pt_regs *regs, unsigned long dr6, bool user) #endif if (notify_die(DIE_DEBUG, "debug", regs, (long)&dr6, 0, - SIGTRAP) == NOTIFY_STOP) { - return; - } + SIGTRAP) == NOTIFY_STOP) + goto out; + + if (user_mode(regs) && + fixup_vdso_exception(regs, X86_TRAP_DB, 0, 0)) + goto out; /* It's safe to allow irq's after DR6 has been saved */ cond_local_irq_enable(regs); @@ -985,6 +995,9 @@ static void math_error(struct pt_regs *regs, int trapnr) if (!si_code) goto exit; + if (fixup_vdso_exception(regs, trapnr, 0, 0)) + return; + force_sig_fault(SIGFPE, si_code, (void __user *)uprobe_get_trap_addr(regs)); exit: diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 8ba78384ea73..9f44ff217418 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -31,6 +31,7 @@ #include /* exception stack */ #include /* VMALLOC_START, ... */ #include /* kvm_handle_async_pf */ +#include /* fixup_vdso_exception() */ #define CREATE_TRACE_POINTS #include @@ -776,6 +777,10 @@ __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); @@ -895,6 +900,9 @@ 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