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=-12.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 2444AC388F9 for ; Mon, 26 Oct 2020 20:32:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C17E920709 for ; Mon, 26 Oct 2020 20:32:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=kernel-dk.20150623.gappssmtp.com header.i=@kernel-dk.20150623.gappssmtp.com header.b="ZrMaxfsj" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732107AbgJZUci (ORCPT ); Mon, 26 Oct 2020 16:32:38 -0400 Received: from mail-io1-f67.google.com ([209.85.166.67]:34425 "EHLO mail-io1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732010AbgJZUch (ORCPT ); Mon, 26 Oct 2020 16:32:37 -0400 Received: by mail-io1-f67.google.com with SMTP id z5so11879530iob.1 for ; Mon, 26 Oct 2020 13:32:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20150623.gappssmtp.com; s=20150623; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=4AnPuyy7/gG6oYUyQdb//jqNqAKJYACguXA57jzvo6k=; b=ZrMaxfsj4jXNi0My0rzGOwASqziLAJjL5ICTZqYmfUtVHbqU22nxSHQuIAc3vzZub1 oJ17AVXFdDutpyqb7jPptxQiGbj6/T9g9E9zkZkCcHe9w8pszAl9wo6dER9HTpnt9uby 2PTanA+zAYSzX0M0JtVUGErHeOq8cdd8kQUvX/kqtNF9hJkRCeG3PS3NSo0dCFfc7Ao0 tQMFPzpECzTReVyt319jpixVUcBq0oOpTqxCTGxFVpPepjzn/tr3UmKv6w30IbsevRKs 6HOtztkd0zcrJzos/HX3+o+NsIIIFVt9SAwNcHWF8AD20/HNcjVqyoNQDfAA2VJRMijY MseA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=4AnPuyy7/gG6oYUyQdb//jqNqAKJYACguXA57jzvo6k=; b=Rh+VRC0j7rn/T6HAiF9tQuyLxNdFZuR7jnzxi4CBsguMATY23KqUAFtAGwmMdwikc+ tRo4UnGVcqNjlizheEzBMBUU5nY9fLC+Rqtxjtn5xfEv+7kGSjCmRuvtxwql+vmjWw5+ ML6p1U5XHMxSfldQV7xFQs38YRDNg8EOQKh0QG8mUrmQEzmNpDL5TehZGcRSIYj47oBk FIfXxAQsBAC9415QfdrKXP6qyUyjDk5JqjSaatt6HybxTf4sw3ca0ROvKZgaRJHjBh8H JTCFadX1DIzc3kAl6bsPpz5NftWmMoP6P5wth5HMNW0vDdMl1KVIkshqcOdwbLoqkvNW dmeA== X-Gm-Message-State: AOAM532fdn/JB7ULzKFm/mg+vjHaBqdojMmUc+inaINVaWyUVrUZSXJz mnANzcsAQBd5xSVt0VUM7oMdOQ== X-Google-Smtp-Source: ABdhPJwDLhFZaUYCOla3VLJx8AvpXlwnt/ECI5tpjVTlfcJcU7BtXAhblTOL48Lg4PXyOlY5Aecltg== X-Received: by 2002:a05:6638:613:: with SMTP id g19mr12945855jar.44.1603744355695; Mon, 26 Oct 2020 13:32:35 -0700 (PDT) Received: from p1.localdomain ([65.144.74.34]) by smtp.gmail.com with ESMTPSA id e12sm6770373ilq.65.2020.10.26.13.32.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 26 Oct 2020 13:32:35 -0700 (PDT) From: Jens Axboe To: linux-kernel@vger.kernel.org, io-uring@vger.kernel.org Cc: peterz@infradead.org, oleg@redhat.com, tglx@linutronix.de, Jens Axboe Subject: [PATCH 2/4] kernel: add support for TIF_NOTIFY_SIGNAL Date: Mon, 26 Oct 2020 14:32:28 -0600 Message-Id: <20201026203230.386348-3-axboe@kernel.dk> X-Mailer: git-send-email 2.29.0 In-Reply-To: <20201026203230.386348-1-axboe@kernel.dk> References: <20201026203230.386348-1-axboe@kernel.dk> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org This adds TIF_NOTIFY_SIGNAL handling in the generic code, which if set, will return true if signal_pending() is used in a wait loop. That causes an exit of the loop so that notify_signal tracehooks can be run. If the wait loop is currently inside a system call, the system call is restarted once task_work has been processed. In preparation for only having arch_do_signal() handle syscall restarts if _TIF_SIGPENDING isn't set, rename it to arch_do_signal_or_restart(). Pass in a boolean that tells the arch signal handler if it should attempt to get a signal, or just process a potential syscall restart. For !CONFIG_GENERIC_ENTRY archs, we add the TIF_NOTIFY_SIGNAL handling to get_signal(). This is done to minimize the needed arch changes to support this feature. Reviewed-by: Oleg Nesterov Signed-off-by: Jens Axboe --- arch/x86/kernel/signal.c | 4 ++-- include/linux/entry-common.h | 11 ++++++++--- include/linux/entry-kvm.h | 4 ++-- include/linux/sched/signal.h | 11 ++++++++++- include/linux/tracehook.h | 27 +++++++++++++++++++++++++++ kernel/entry/common.c | 14 +++++++++++--- kernel/entry/kvm.c | 3 +++ kernel/signal.c | 14 ++++++++++++++ 8 files changed, 77 insertions(+), 11 deletions(-) diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c index be0d7d4152ec..ea794a083c44 100644 --- a/arch/x86/kernel/signal.c +++ b/arch/x86/kernel/signal.c @@ -804,11 +804,11 @@ static inline unsigned long get_nr_restart_syscall(const struct pt_regs *regs) * want to handle. Thus you cannot kill init even with a SIGKILL even by * mistake. */ -void arch_do_signal(struct pt_regs *regs) +void arch_do_signal_or_restart(struct pt_regs *regs, bool has_signal) { struct ksignal ksig; - if (get_signal(&ksig)) { + if (has_signal && get_signal(&ksig)) { /* Whee! Actually deliver the signal. */ handle_signal(&ksig, regs); return; diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h index 474f29638d2c..b9711e813ec2 100644 --- a/include/linux/entry-common.h +++ b/include/linux/entry-common.h @@ -37,6 +37,10 @@ # define _TIF_UPROBE (0) #endif +#ifndef _TIF_NOTIFY_SIGNAL +# define _TIF_NOTIFY_SIGNAL (0) +#endif + /* * TIF flags handled in syscall_enter_from_user_mode() */ @@ -69,7 +73,7 @@ #define EXIT_TO_USER_MODE_WORK \ (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_UPROBE | \ - _TIF_NEED_RESCHED | _TIF_PATCH_PENDING | \ + _TIF_NEED_RESCHED | _TIF_PATCH_PENDING | _TIF_NOTIFY_SIGNAL | \ ARCH_EXIT_TO_USER_MODE_WORK) /** @@ -259,12 +263,13 @@ static __always_inline void arch_exit_to_user_mode(void) { } #endif /** - * arch_do_signal - Architecture specific signal delivery function + * arch_do_signal_or_restart - Architecture specific signal delivery function * @regs: Pointer to currents pt_regs + * @has_signal: actual signal to handle * * Invoked from exit_to_user_mode_loop(). */ -void arch_do_signal(struct pt_regs *regs); +void arch_do_signal_or_restart(struct pt_regs *regs, bool has_signal); /** * arch_syscall_exit_tracehook - Wrapper around tracehook_report_syscall_exit() diff --git a/include/linux/entry-kvm.h b/include/linux/entry-kvm.h index 0cef17afb41a..9b93f8584ff7 100644 --- a/include/linux/entry-kvm.h +++ b/include/linux/entry-kvm.h @@ -11,8 +11,8 @@ # define ARCH_XFER_TO_GUEST_MODE_WORK (0) #endif -#define XFER_TO_GUEST_MODE_WORK \ - (_TIF_NEED_RESCHED | _TIF_SIGPENDING | \ +#define XFER_TO_GUEST_MODE_WORK \ + (_TIF_NEED_RESCHED | _TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL | \ _TIF_NOTIFY_RESUME | ARCH_XFER_TO_GUEST_MODE_WORK) struct kvm_vcpu; diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h index 404145dc536e..bd5afa076189 100644 --- a/include/linux/sched/signal.h +++ b/include/linux/sched/signal.h @@ -360,6 +360,15 @@ static inline int task_sigpending(struct task_struct *p) static inline int signal_pending(struct task_struct *p) { +#if defined(TIF_NOTIFY_SIGNAL) + /* + * TIF_NOTIFY_SIGNAL isn't really a signal, but it requires the same + * behavior in terms of ensuring that we break out of wait loops + * so that notify signal callbacks can be processed. + */ + if (unlikely(test_tsk_thread_flag(p, TIF_NOTIFY_SIGNAL))) + return 1; +#endif return task_sigpending(p); } @@ -507,7 +516,7 @@ extern int set_user_sigmask(const sigset_t __user *umask, size_t sigsetsize); static inline void restore_saved_sigmask_unless(bool interrupted) { if (interrupted) - WARN_ON(!test_thread_flag(TIF_SIGPENDING)); + WARN_ON(!signal_pending(current)); else restore_saved_sigmask(); } diff --git a/include/linux/tracehook.h b/include/linux/tracehook.h index b480e1a07ed8..f7d82e4fafd6 100644 --- a/include/linux/tracehook.h +++ b/include/linux/tracehook.h @@ -198,4 +198,31 @@ static inline void tracehook_notify_resume(struct pt_regs *regs) blkcg_maybe_throttle_current(); } +/* + * called by exit_to_user_mode_loop() if ti_work & _TIF_NOTIFY_SIGNAL. This + * is currently used by TWA_SIGNAL based task_work, which requires breaking + * wait loops to ensure that task_work is noticed and run. + */ +static inline void tracehook_notify_signal(void) +{ +#if defined(TIF_NOTIFY_SIGNAL) + clear_thread_flag(TIF_NOTIFY_SIGNAL); + smp_mb__after_atomic(); + if (current->task_works) + task_work_run(); +#endif +} + +/* + * Called when we have work to process from exit_to_user_mode_loop() + */ +static inline void set_notify_signal(struct task_struct *task) +{ +#if defined(TIF_NOTIFY_SIGNAL) + if (!test_and_set_tsk_thread_flag(task, TIF_NOTIFY_SIGNAL) && + !wake_up_state(task, TASK_INTERRUPTIBLE)) + kick_process(task); +#endif +} + #endif /* */ diff --git a/kernel/entry/common.c b/kernel/entry/common.c index 2b8366693d5c..54c07d386aeb 100644 --- a/kernel/entry/common.c +++ b/kernel/entry/common.c @@ -135,7 +135,15 @@ static __always_inline void exit_to_user_mode(void) } /* Workaround to allow gradual conversion of architecture code */ -void __weak arch_do_signal(struct pt_regs *regs) { } +void __weak arch_do_signal_or_restart(struct pt_regs *regs, bool has_signal) { } + +static void handle_signal_work(struct pt_regs *regs, unsigned long ti_work) +{ + if (ti_work & _TIF_NOTIFY_SIGNAL) + tracehook_notify_signal(); + + arch_do_signal_or_restart(regs, ti_work & _TIF_SIGPENDING); +} static unsigned long exit_to_user_mode_loop(struct pt_regs *regs, unsigned long ti_work) @@ -157,8 +165,8 @@ static unsigned long exit_to_user_mode_loop(struct pt_regs *regs, if (ti_work & _TIF_PATCH_PENDING) klp_update_patch_state(current); - if (ti_work & _TIF_SIGPENDING) - arch_do_signal(regs); + if (ti_work & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL)) + handle_signal_work(regs, ti_work); if (ti_work & _TIF_NOTIFY_RESUME) { tracehook_notify_resume(regs); diff --git a/kernel/entry/kvm.c b/kernel/entry/kvm.c index b6678a5e3cf6..49972ee99aff 100644 --- a/kernel/entry/kvm.c +++ b/kernel/entry/kvm.c @@ -8,6 +8,9 @@ static int xfer_to_guest_mode_work(struct kvm_vcpu *vcpu, unsigned long ti_work) do { int ret; + if (ti_work & _TIF_NOTIFY_SIGNAL) + tracehook_notify_signal(); + if (ti_work & _TIF_SIGPENDING) { kvm_handle_signal_exit(vcpu); return -EINTR; diff --git a/kernel/signal.c b/kernel/signal.c index 9f86246a8637..f67ea9a08ac0 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -2529,6 +2529,20 @@ bool get_signal(struct ksignal *ksig) struct signal_struct *signal = current->signal; int signr; + /* + * For non-generic architectures, check for TIF_NOTIFY_SIGNAL so + * that the arch handlers don't all have to do it. If we get here + * without TIF_SIGPENDING, just exit after running signal work. + */ +#ifdef TIF_NOTIFY_SIGNAL + if (!IS_ENABLED(CONFIG_GENERIC_ENTRY)) { + if (test_thread_flag(TIF_NOTIFY_SIGNAL)) + tracehook_notify_signal(); + if (!task_sigpending(current)) + return false; + } +#endif + if (unlikely(uprobe_deny_signal())) return false; -- 2.29.0