From patchwork Thu Mar 30 04:39:51 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Wedson Almeida Filho X-Patchwork-Id: 76884 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a59:b0ea:0:b0:3b6:4342:cba0 with SMTP id b10csp873224vqo; Wed, 29 Mar 2023 21:50:40 -0700 (PDT) X-Google-Smtp-Source: AK7set9F2lTCEXOSMOz0aKg/ocr/Bs92aNHbV996Q2XQe1+qxtoOgSw0GTuYw18b1kpfYw0R5A0O X-Received: by 2002:a05:6a20:baa0:b0:d9:ecba:b9fc with SMTP id fb32-20020a056a20baa000b000d9ecbab9fcmr16859145pzb.54.1680151839815; Wed, 29 Mar 2023 21:50:39 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1680151839; cv=none; d=google.com; s=arc-20160816; b=ytgXBa4iozeOsBOprtMCgjl2Ss3qevJ28QKBQ1dWEs0q1Gawm9Pt6CNTBlU3EnKtJr c7EGNoCxuKavV2GNLRp8fFByhXfymBLQA7esDoloDh9rHuCF03vLh3DCCodTROGogMMk lC5gi7rHllEKLlOMozIvJHH8ugvwUt9oI6XV374oi0koDMKrrtBkUvEh5qw6I+z2xPlE xq9fWI87qEGyIpxMy4NSmyt5fl69rzw1pnB0zTgMaDOZN8nHJ8Z4DmxQIqpCj0cuIaK6 OgbqVuk2xs7Zk606gn89QiapzlsEoFPvekYv6Z1zV5fPwCiD7r+UDiIugDSMBt+gUsl3 HmBA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :references:in-reply-to:message-id:date:subject:cc:to:from :dkim-signature; bh=JaygZpxwnfzBcLtVwosxyCaJLz/HPg5F8ZKIQhWNoz4=; b=qJf/j4AB4t4Vxm2Z/0BZPL8lLUfFa5wk1sHWC4qYMuak3pD6Si6KK4sEqQFvtS+skv rR0IFVpREekpaiUlBy/fwtvebYixC9Tw5IlkbMOlvRzygGLDNw0Mtc/nDPsH6SkmI8O4 gp5/o2POJbQfS9ZvKWHjAqF0U6g+HZZsvCik7lC1ZPMxE82dAQUbcT9AiZd3MDsp+L2h gQZBju1FjNtbQo+Pe5gpL7mA0lJTaB1Gaqd39kFbzg9dEH48PgxIURT3UdB/f8bUt/G5 5IAzhdaRGnakafOrKdZOEq2+cLNE0xRZWbTWI+ClFgdI9TH7JseQnbB8lTz3rpFvvEtw zhTw== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@gmail.com header.s=20210112 header.b=FXwYLvrI; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Received: from out1.vger.email (out1.vger.email. [2620:137:e000::1:20]) by mx.google.com with ESMTP id bk13-20020a056a02028d00b0050300b179f3si31536833pgb.444.2023.03.29.21.50.26; Wed, 29 Mar 2023 21:50:39 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20210112 header.b=FXwYLvrI; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230114AbjC3EmU (ORCPT + 99 others); Thu, 30 Mar 2023 00:42:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36738 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230076AbjC3Elv (ORCPT ); Thu, 30 Mar 2023 00:41:51 -0400 Received: from mail-oa1-x2c.google.com (mail-oa1-x2c.google.com [IPv6:2001:4860:4864:20::2c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 408387295; Wed, 29 Mar 2023 21:41:25 -0700 (PDT) Received: by mail-oa1-x2c.google.com with SMTP id 586e51a60fabf-17683b570b8so18516016fac.13; Wed, 29 Mar 2023 21:41:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; t=1680151284; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=JaygZpxwnfzBcLtVwosxyCaJLz/HPg5F8ZKIQhWNoz4=; b=FXwYLvrIzNZooIRqEXJqa42IDRe+8JDe2VQoZkMZuHOEcfRdn08oqkv775h8AUEPhr VZOsHttuI0VIspAYJOPt+At7ZMsiWn6j0wNa43Av9xDCqbJet7GunO0Wa4jrQ4rm0mfP 4U7FZGZYhIBZCmpV8m108tEsQViHPoE+fUU7a5b1/B6/k5MQRcI+6GtnaFurUZA+AjBx JnEmRrtLnioJ51uu2QXp1WJ8ziQF53zY2xaCGEcOAAU5lwY2OXqWlVtpVjbfIfdIcynU CrT1EgHq9/TV1c8no5FMUS9cLfZLNDV10Wq2g2VJ0M9tK6NoQdzqmfoR1fyEf6/8x7hp BvWA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1680151284; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=JaygZpxwnfzBcLtVwosxyCaJLz/HPg5F8ZKIQhWNoz4=; b=llVRs/xwipp41Ff97GxmACqOzcnvkUqvj/RzRdw38IAR74HXyJ2qBzfsRSnFCH+fel sLDgKCxkmd14fcbuhyvvzboZ9hnxLPlZHY/Ypewbj2ztAAykteusvh2etXvrlNC1VR1W kW7EXLuKA+w8Cr8D/NhF19uy+PVSB0uT7BugLX6iwz7twbRcpuEVWbo7VEXLFykmmdP4 pg9Ku/4zKF87i6Ph4rJWqotdRTYcb21oqm58zwCORV+1SGtudkEERMFdf5uoVFEpuMNP wGXLfPE63lWJQ7CnzQkgQOZWB0vaSt2GP0Wlc6LrsySQGDOgijtVkKGjSHVBhJSETHVd f0Kw== X-Gm-Message-State: AO0yUKUFC65PnvCx0qN4lmiSagHswUuVBRFm89F3IQ364PG9RzZM8tqW hTkrCLt7gge4BWVegUiDAma+SknuEYcyJw== X-Received: by 2002:a05:6870:459f:b0:177:9b62:6b7e with SMTP id y31-20020a056870459f00b001779b626b7emr14014751oao.24.1680151284471; Wed, 29 Mar 2023 21:41:24 -0700 (PDT) Received: from wedsonaf-dev.home.lan ([189.124.190.154]) by smtp.googlemail.com with ESMTPSA id ea43-20020a056870072b00b0017e0c13b29asm7518599oab.36.2023.03.29.21.41.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 29 Mar 2023 21:41:24 -0700 (PDT) From: Wedson Almeida Filho To: rust-for-linux@vger.kernel.org Cc: Miguel Ojeda , Alex Gaynor , Boqun Feng , Gary Guo , =?utf-8?q?B?= =?utf-8?q?j=C3=B6rn_Roy_Baron?= , linux-kernel@vger.kernel.org, Wedson Almeida Filho , Ingo Molnar , Peter Zijlstra Subject: [PATCH 10/13] rust: introduce `Task::current` Date: Thu, 30 Mar 2023 01:39:51 -0300 Message-Id: <20230330043954.562237-10-wedsonaf@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230330043954.562237-1-wedsonaf@gmail.com> References: <20230330043954.562237-1-wedsonaf@gmail.com> MIME-Version: 1.0 X-Spam-Status: No, score=-0.2 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM,RCVD_IN_DNSWL_NONE, SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1761766895922170847?= X-GMAIL-MSGID: =?utf-8?q?1761766895922170847?= From: Wedson Almeida Filho This allows Rust code to get a reference to the current task without having to increment the refcount, but still guaranteeing memory safety. Cc: Ingo Molnar Cc: Peter Zijlstra Signed-off-by: Wedson Almeida Filho --- rust/helpers.c | 6 ++++ rust/kernel/task.rs | 83 ++++++++++++++++++++++++++++++++++++++++++++- 2 files changed, 88 insertions(+), 1 deletion(-) diff --git a/rust/helpers.c b/rust/helpers.c index 58a194042c86..96441744030e 100644 --- a/rust/helpers.c +++ b/rust/helpers.c @@ -100,6 +100,12 @@ bool rust_helper_refcount_dec_and_test(refcount_t *r) } EXPORT_SYMBOL_GPL(rust_helper_refcount_dec_and_test); +struct task_struct *rust_helper_get_current(void) +{ + return current; +} +EXPORT_SYMBOL_GPL(rust_helper_get_current); + void rust_helper_get_task_struct(struct task_struct *t) { get_task_struct(t); diff --git a/rust/kernel/task.rs b/rust/kernel/task.rs index 8d7a8222990f..8b2b56ba9c6d 100644 --- a/rust/kernel/task.rs +++ b/rust/kernel/task.rs @@ -5,7 +5,7 @@ //! C header: [`include/linux/sched.h`](../../../../include/linux/sched.h). use crate::bindings; -use core::{cell::UnsafeCell, ptr}; +use core::{cell::UnsafeCell, marker::PhantomData, ops::Deref, ptr}; /// Wraps the kernel's `struct task_struct`. /// @@ -13,6 +13,46 @@ use core::{cell::UnsafeCell, ptr}; /// /// Instances of this type are always ref-counted, that is, a call to `get_task_struct` ensures /// that the allocation remains valid at least until the matching call to `put_task_struct`. +/// +/// # Examples +/// +/// The following is an example of getting the PID of the current thread with zero additional cost +/// when compared to the C version: +/// +/// ``` +/// use kernel::task::Task; +/// +/// let pid = Task::current().pid(); +/// ``` +/// +/// Getting the PID of the current process, also zero additional cost: +/// +/// ``` +/// use kernel::task::Task; +/// +/// let pid = Task::current().group_leader().pid(); +/// ``` +/// +/// Getting the current task and storing it in some struct. The reference count is automatically +/// incremented when creating `State` and decremented when it is dropped: +/// +/// ``` +/// use kernel::{task::Task, ARef}; +/// +/// struct State { +/// creator: ARef, +/// index: u32, +/// } +/// +/// impl State { +/// fn new() -> Self { +/// Self { +/// creator: Task::current().into(), +/// index: 0, +/// } +/// } +/// } +/// ``` #[repr(transparent)] pub struct Task(pub(crate) UnsafeCell); @@ -25,6 +65,20 @@ unsafe impl Sync for Task {} type Pid = bindings::pid_t; impl Task { + /// Returns a task reference for the currently executing task/thread. + pub fn current<'a>() -> TaskRef<'a> { + // SAFETY: Just an FFI call with no additional safety requirements. + let ptr = unsafe { bindings::get_current() }; + + TaskRef { + // SAFETY: If the current thread is still running, the current task is valid. Given + // that `TaskRef` is not `Send`, we know it cannot be transferred to another thread + // (where it could potentially outlive the caller). + task: unsafe { &*ptr.cast() }, + _not_send: PhantomData, + } + } + /// Returns the group leader of the given task. pub fn group_leader(&self) -> &Task { // SAFETY: By the type invariant, we know that `self.0` is valid. @@ -69,3 +123,30 @@ unsafe impl crate::types::AlwaysRefCounted for Task { unsafe { bindings::put_task_struct(obj.cast().as_ptr()) } } } + +/// A wrapper for a shared reference to [`Task`] that isn't [`Send`]. +/// +/// We make this explicitly not [`Send`] so that we can use it to represent the current thread +/// without having to increment/decrement the task's reference count. +/// +/// # Invariants +/// +/// The wrapped [`Task`] remains valid for the lifetime of the object. +pub struct TaskRef<'a> { + task: &'a Task, + _not_send: PhantomData<*mut ()>, +} + +impl Deref for TaskRef<'_> { + type Target = Task; + + fn deref(&self) -> &Self::Target { + self.task + } +} + +impl From> for crate::types::ARef { + fn from(t: TaskRef<'_>) -> Self { + t.deref().into() + } +}