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=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT 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 97ACDC4CED1 for ; Fri, 4 Oct 2019 18:17:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7F39E215EA for ; Fri, 4 Oct 2019 18:17:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730533AbfJDSRB (ORCPT ); Fri, 4 Oct 2019 14:17:01 -0400 Received: from mga07.intel.com ([134.134.136.100]:15508 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730477AbfJDSRA (ORCPT ); Fri, 4 Oct 2019 14:17:00 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 04 Oct 2019 11:17:00 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.67,257,1566889200"; d="scan'208";a="204394759" Received: from chang-linux-3.sc.intel.com ([172.25.66.185]) by orsmga002.jf.intel.com with ESMTP; 04 Oct 2019 11:16:59 -0700 From: "Chang S. Bae" To: linux-kernel@vger.kernel.org, tglx@linutronix.de, bp@alien8.de, luto@kernel.org Cc: hpa@zytor.com, dave.hansen@intel.com, tony.luck@intel.com, ak@linux.intel.com, ravi.v.shankar@intel.com, chang.seok.bae@intel.com, Vegard Nossum Subject: [PATCH v9 04/17] x86/entry/64: Clean up paranoid exit Date: Fri, 4 Oct 2019 11:15:56 -0700 Message-Id: <1570212969-21888-5-git-send-email-chang.seok.bae@intel.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1570212969-21888-1-git-send-email-chang.seok.bae@intel.com> References: <1570212969-21888-1-git-send-email-chang.seok.bae@intel.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Andy Lutomirski All that paranoid exit needs to do is to disable IRQs, handle IRQ tracing, then restore CR3, and restore GS base. Simply do those actions in that order. Cleaning up the spaghetti code. Signed-off-by: Andy Lutomirski Signed-off-by: Chang S. Bae Reviewed-by: Tony Luck Cc: Thomas Gleixner Cc: Borislav Petkov Cc: Andy Lutomirski Cc: H. Peter Anvin Cc: Dave Hansen Cc: Tony Luck Cc: Andi Kleen Cc: Vegard Nossum --- Changes from v8: none Changes from v7: * Included as a new patch. Took the cleanup part from the Andy Lutomirski's original patch [*] and edited its changelog a little bit. [*] https://lkml.kernel.org/r/59725ceb08977359489fbed979716949ad45f616.1562035429.git.luto@kernel.org --- arch/x86/entry/entry_64.S | 29 +++++++++++++++++------------ 1 file changed, 17 insertions(+), 12 deletions(-) diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index b7c3ea4..dd0d62a 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -1265,20 +1265,25 @@ END(paranoid_entry) ENTRY(paranoid_exit) UNWIND_HINT_REGS DISABLE_INTERRUPTS(CLBR_ANY) + + /* + * The order of operations is important. IRQ tracing requires + * kernel GS base and CR3. RESTORE_CR3 requires kernel GS base. + * + * NB to anyone to try to optimize this code: this code does + * not execute at all for exceptions from user mode. Those + * exceptions go through error_exit instead. + */ TRACE_IRQS_OFF_DEBUG - testl %ebx, %ebx /* swapgs needed? */ - jnz .Lparanoid_exit_no_swapgs - TRACE_IRQS_IRETQ - /* Always restore stashed CR3 value (see paranoid_entry) */ - RESTORE_CR3 scratch_reg=%rbx save_reg=%r14 + RESTORE_CR3 scratch_reg=%rax save_reg=%r14 + + /* If EBX is 0, SWAPGS is required */ + testl %ebx, %ebx + jnz restore_regs_and_return_to_kernel + + /* We are returning to a context with user GS base */ SWAPGS_UNSAFE_STACK - jmp .Lparanoid_exit_restore -.Lparanoid_exit_no_swapgs: - TRACE_IRQS_IRETQ_DEBUG - /* Always restore stashed CR3 value (see paranoid_entry) */ - RESTORE_CR3 scratch_reg=%rbx save_reg=%r14 -.Lparanoid_exit_restore: - jmp restore_regs_and_return_to_kernel + jmp restore_regs_and_return_to_kernel END(paranoid_exit) /* -- 2.7.4