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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 AD2AFC28CBC for ; Sat, 9 May 2020 17:38:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8E8822192A for ; Sat, 9 May 2020 17:38:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589045883; bh=PHIzsR/nq6FXDEA4DvjmmqDeRmjCdzHAA3mINfh7ypo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Rf2QgVy19bBuCbawlYlwKKyRbhWlzzZn6zM+uWoO0H+djUNhB1vOP8P7He+lVnGen OvwXzB256gim5/WZBh41DA+ajRjm2t8nrE8MW+mf4IN0ab247YOZHUoKA55eHz3Hdw iW8xq1dCFtEslyCKzhmqRvZlvJfBObtUzokxy0oI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728795AbgEIRiC (ORCPT ); Sat, 9 May 2020 13:38:02 -0400 Received: from mail.kernel.org ([198.145.29.99]:54314 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728340AbgEIRhF (ORCPT ); Sat, 9 May 2020 13:37:05 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 3913224960; Sat, 9 May 2020 17:37:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589045825; bh=PHIzsR/nq6FXDEA4DvjmmqDeRmjCdzHAA3mINfh7ypo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=EcNJuDUZWyZRm66TO4qNPm2nAUB/juu9mIjSaO3PkL/J1PjmrH4smIsMExiBt7EF+ Qnm3WjlwUYk43BR2BRDqr+v8Nqoe+uCGctEs7pCd3fJmQKA/cL6mPoyy/35Hq7thrY /Rk3z6hwMI91EOGy75n95D++Kv2PusGYIlfhAe7w= From: Sasha Levin 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, Sasha Levin , Vegard Nossum Subject: [PATCH v11 04/18] x86/entry/64: Clean up paranoid exit Date: Sat, 9 May 2020 13:36:41 -0400 Message-Id: <20200509173655.13977-5-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200509173655.13977-1-sashal@kernel.org> References: <20200509173655.13977-1-sashal@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 Signed-off-by: Sasha Levin 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 --- arch/x86/entry/entry_64.S | 26 ++++++++++++++++---------- 1 file changed, 16 insertions(+), 10 deletions(-) diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index 0e9504fabe526..3adb3c8e2409b 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -1266,19 +1266,25 @@ SYM_CODE_END(paranoid_entry) SYM_CODE_START_LOCAL(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 restore_regs_and_return_to_kernel -.Lparanoid_exit_no_swapgs: - TRACE_IRQS_IRETQ_DEBUG - /* Always restore stashed CR3 value (see paranoid_entry) */ - RESTORE_CR3 scratch_reg=%rbx save_reg=%r14 - jmp restore_regs_and_return_to_kernel SYM_CODE_END(paranoid_exit) /* -- 2.20.1