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 99662C433E1 for ; Fri, 26 Jun 2020 17:21:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 77822207FC for ; Fri, 26 Jun 2020 17:21:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593192105; bh=1KnbXwE+bmAZRBzxpU4AIX//ta8YBFUr+H6enwpmo9A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=ZfHAdfkCsJqhC50MCeE21Zq1tHONkRQ+TW3tsizmmLfOlAKeHnnIWfO42IiObHAhL ZOdr4pwL4tfRjJceeOzEBvW4WAaWxNNaf3NuPXbln3k0BBTpt/FLLhwSSGMH4vA+MK 7vG87NsqW5CMLnNAP/46MUfseqaYR1ZZbQgSlK14= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727104AbgFZRVo (ORCPT ); Fri, 26 Jun 2020 13:21:44 -0400 Received: from mail.kernel.org ([198.145.29.99]:39778 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726910AbgFZRVV (ORCPT ); Fri, 26 Jun 2020 13:21:21 -0400 Received: from localhost (c-67-180-165-146.hsd1.ca.comcast.net [67.180.165.146]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 0862B2065F; Fri, 26 Jun 2020 17:21:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593192081; bh=1KnbXwE+bmAZRBzxpU4AIX//ta8YBFUr+H6enwpmo9A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=zLgIg9+Kc6v2O/9rzSj9PMRNASXVTteANa5UrP1pa3D6xKpUGJrJgsrg3u9RsU/Gi EMFFLPqZSQmIsek8lb+Hef3NdDSwrvAEga/juhjxV7fIC0RPMTVcwkJ/1fL34mO7Bh eKX99ueb+yhOuuCpUSMcKUvTUlekKgK4DSwHizUU= From: Andy Lutomirski To: x86@kernel.org Cc: linux-kernel@vger.kernel.org, Andrew Cooper , Juergen Gross , Andy Lutomirski Subject: [PATCH 2/6] x86/entry: Move SYSENTER's regs->sp and regs->flags fixups into C Date: Fri, 26 Jun 2020 10:21:12 -0700 Message-Id: X-Mailer: git-send-email 2.25.4 In-Reply-To: References: 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 The SYSENTER asm (32-bit and compat) contains fixups for regs->sp and regs->flags. Move the fixups into C and fix some comments while we're at it. IMO this is a valid cleanup all by itself, and it also simplifies the subsequent patch that will fix Xen PV SYSENTER. Signed-off-by: Andy Lutomirski --- arch/x86/entry/common.c | 12 ++++++++++++ arch/x86/entry/entry_32.S | 5 ++--- arch/x86/entry/entry_64_compat.S | 11 +++++------ 3 files changed, 19 insertions(+), 9 deletions(-) diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c index ed8ccc820995..f392a8bcd1c3 100644 --- a/arch/x86/entry/common.c +++ b/arch/x86/entry/common.c @@ -522,6 +522,18 @@ __visible noinstr long do_fast_syscall_32(struct pt_regs *regs) (regs->flags & (X86_EFLAGS_RF | X86_EFLAGS_TF | X86_EFLAGS_VM)) == 0; #endif } + +/* Returns 0 to return using IRET or 1 to return using SYSEXIT/SYSRETL. */ +__visible noinstr long do_SYSENTER_32(struct pt_regs *regs) +{ + /* SYSENTER loses RSP, but the vDSO saved it in RBP. */ + regs->sp = regs->bp; + + /* SYSENTER clobbers EFLAGS.IF. Assume it was set in usermode. */ + regs->flags |= X86_EFLAGS_IF; + + return do_fast_syscall_32(regs); +} #endif SYSCALL_DEFINE0(ni_syscall) diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index 024d7d276cd4..2d0bd5d5f032 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -933,9 +933,8 @@ SYM_FUNC_START(entry_SYSENTER_32) .Lsysenter_past_esp: pushl $__USER_DS /* pt_regs->ss */ - pushl %ebp /* pt_regs->sp (stashed in bp) */ + pushl $0 /* pt_regs->sp (placeholder) */ pushfl /* pt_regs->flags (except IF = 0) */ - orl $X86_EFLAGS_IF, (%esp) /* Fix IF */ pushl $__USER_CS /* pt_regs->cs */ pushl $0 /* pt_regs->ip = 0 (placeholder) */ pushl %eax /* pt_regs->orig_ax */ @@ -965,7 +964,7 @@ SYM_FUNC_START(entry_SYSENTER_32) .Lsysenter_flags_fixed: movl %esp, %eax - call do_fast_syscall_32 + call do_SYSENTER_32 /* XEN PV guests always use IRET path */ ALTERNATIVE "testl %eax, %eax; jz .Lsyscall_32_done", \ "jmp .Lsyscall_32_done", X86_FEATURE_XENPV diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S index 0f974ae01e62..7b9d8150f652 100644 --- a/arch/x86/entry/entry_64_compat.S +++ b/arch/x86/entry/entry_64_compat.S @@ -68,16 +68,15 @@ SYM_CODE_START(entry_SYSENTER_compat) /* Construct struct pt_regs on stack */ pushq $__USER32_DS /* pt_regs->ss */ - pushq %rbp /* pt_regs->sp (stashed in bp) */ + pushq $0 /* pt_regs->sp = 0 (placeholder) */ /* * Push flags. This is nasty. First, interrupts are currently - * off, but we need pt_regs->flags to have IF set. Second, even - * if TF was set when SYSENTER started, it's clear by now. We fix - * that later using TIF_SINGLESTEP. + * off, but we need pt_regs->flags to have IF set. Second, if TS + * was set in usermode, it's still set, and we're singlestepping + * through this code. do_SYSENTER_32() will fix up IF. */ pushfq /* pt_regs->flags (except IF = 0) */ - orl $X86_EFLAGS_IF, (%rsp) /* Fix saved flags */ pushq $__USER32_CS /* pt_regs->cs */ pushq $0 /* pt_regs->ip = 0 (placeholder) */ pushq %rax /* pt_regs->orig_ax */ @@ -135,7 +134,7 @@ SYM_CODE_START(entry_SYSENTER_compat) .Lsysenter_flags_fixed: movq %rsp, %rdi - call do_fast_syscall_32 + call do_SYSENTER_32 /* XEN PV guests always use IRET path */ ALTERNATIVE "testl %eax, %eax; jz swapgs_restore_regs_and_return_to_usermode", \ "jmp swapgs_restore_regs_and_return_to_usermode", X86_FEATURE_XENPV -- 2.25.4