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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 9D443C4BA09 for ; Tue, 25 Feb 2020 23:27:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 77BCA24680 for ; Tue, 25 Feb 2020 23:27:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730718AbgBYX11 (ORCPT ); Tue, 25 Feb 2020 18:27:27 -0500 Received: from Galois.linutronix.de ([193.142.43.55]:56046 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730573AbgBYX1H (ORCPT ); Tue, 25 Feb 2020 18:27:07 -0500 Received: from p5de0bf0b.dip0.t-ipconnect.de ([93.224.191.11] helo=nanos.tec.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1j6jb2-00057X-Sp; Wed, 26 Feb 2020 00:26:37 +0100 Received: from nanos.tec.linutronix.de (localhost [IPv6:::1]) by nanos.tec.linutronix.de (Postfix) with ESMTP id 343421040C7; Wed, 26 Feb 2020 00:25:54 +0100 (CET) Message-Id: <20200225231610.312478926@linutronix.de> User-Agent: quilt/0.65 Date: Tue, 25 Feb 2020 23:47:33 +0100 From: Thomas Gleixner To: LKML Cc: x86@kernel.org, Steven Rostedt , Brian Gerst , Juergen Gross , Paolo Bonzini , Arnd Bergmann Subject: [patch 14/15] x86/entry: Provide return_from exception() References: <20200225224719.950376311@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Now that all exceptions, interrupts and system vectors are using the IDTENTRY machinery, the return from exception handling in ASM can be lifted to C. Provide a C function which: - Invokes prepare_exit_to_user_mode() when the exception hit user mode - Checks for preemption when the exception hit kernel mode - Has the interrupt tracing in C Signed-off-by: Thomas Gleixner --- arch/x86/entry/common.c | 43 ++++++++++++++++++++++++++++++++++++++++ arch/x86/include/asm/idtentry.h | 2 + 2 files changed, 45 insertions(+) --- a/arch/x86/entry/common.c +++ b/arch/x86/entry/common.c @@ -480,3 +480,46 @@ static __always_inline long do_fast_sysc NOKPROBE_SYMBOL(do_fast_syscall_32); #endif /* CONFIG_X86_32 || CONFIG_IA32_EMULATION */ + +/** + * return_from_exception - Common code to handle return from exceptions + * @regs - Pointer to pt_regs (exception entry regs) + * + * Depending on the return target (kernel/user) this runs the necessary + * preemption and work checks if possible and reguired and returns to + * the caller with interrupts disabled and no further work pending. + * + * This is the last action before returning to the low level ASM code which + * just needs to return to the appropriate context. + * + * Invoked by all exception/interrupt IDTENTRY handlers which are not + * returning through the paranoid exit path (all except NMI, MCE, DF). + */ +void notrace return_from_exception(struct pt_regs *regs) +{ + /* + * Unconditionally disable interrupts as some handlers like + * the fault handler are not guaranteeing to return with + * interrupts disabled. + */ + local_irq_disable(); + + /* Check whether this returns to user mode */ + if (user_mode(regs)) { + prepare_exit_to_usermode(regs); + } else { + /* Interrupts stay disabled on return? */ + if (!(regs->flags & X86_EFLAGS_IF)) + return; + + /* Check kernel preemption, if enabled */ + if (IS_ENABLED(CONFIG_PREEMPTION)) { + /* Check for preemption */ + if (!preempt_count() && need_resched()) + preempt_schedule_irq(); + } + } + /* Make sure the tracer knows that IRET will enable interrupts */ + trace_hardirqs_on(); +} +NOKPROBE_SYMBOL(return_from_exception); --- a/arch/x86/include/asm/idtentry.h +++ b/arch/x86/include/asm/idtentry.h @@ -19,6 +19,8 @@ static __always_inline void enter_from_u static __always_inline void enter_from_user_context(void) { } #endif +void return_from_exception(struct pt_regs *regs); + /** * idtentry_enter - Handle state tracking on idtentry * @regs: Pointer to pt_regs of interrupted context