From patchwork Thu Feb 8 15:47:51 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alice Ryhl X-Patchwork-Id: 198449 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a05:7300:50ea:b0:106:860b:bbdd with SMTP id r10csp259930dyd; Thu, 8 Feb 2024 07:49:29 -0800 (PST) X-Google-Smtp-Source: AGHT+IFw4HgeI0HY3wE1Fkp3I7Wee+qpm8AzSBpi6h4gIaWj1Dw2F9x/KyKW/IkSeTiY5kxRDFOk X-Received: by 2002:a81:9986:0:b0:5ff:7eaa:92ad with SMTP id q128-20020a819986000000b005ff7eaa92admr7473884ywg.37.1707407369368; Thu, 08 Feb 2024 07:49:29 -0800 (PST) ARC-Seal: i=2; a=rsa-sha256; t=1707407369; cv=pass; d=google.com; s=arc-20160816; b=n0x7Ztp5BCjPwn7MMKt14P/eVE3UxcaYZgRUdP/Q8Kxv7eJJKv2scOytzzN1fo+3xS gsCWNS+5FPHUmeN4Y+8CiLuQJRP89yXfr+pDESzAoa5q3pyYpYnZHoxFzNjNVauqYh/7 U7dXzziTgS1PBo9WRYgAraDydzVJSDcZRNcimWU7R9WncrRHye5H2YFdyAHo2NGhmejq PQ2PqdYR2fNHcTC2jDYzerawDUsw43yc5qHD5ad6DhJ/A9zBMnUrlyZS1DyB2B57cjvM IJNRVWHgVTZeITMM2gZz/Bsj1YQMG2u3HyClB+lkA7qHl0t1r80cH9gLCkfebUBAPuK7 xdeQ== ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=cc:to:from:subject:message-id:references:mime-version :list-unsubscribe:list-subscribe:list-id:precedence:in-reply-to:date :dkim-signature; bh=MZxfREqmJLVb5yZOS5o3jZQJUZjkOkdbEVLWBie4ZLY=; fh=Tag0EexVKlSLjFYE32mf+NKL9/Aq9e2xq7lvOtc/F+A=; b=DO1x29Z4ffrPxmkoby5vQJt1kPJu4GGll5x3OFYsOcsQhFE05tJrJKpmzDD9L/eDMS CcJetViuHqbFPBvc2JaChNu6S8HMzr4gNM7f0LdJl/C9X6u0pBwExEtfRkFLpl7ek81V wV695vGdf43GuCJVC0W7WjORsPXlbV/yaWIAJ2+y+0w7XD6vtHsT9ZHFvgUn2TjWDi/G Y7vjaX8da0hNFWqTXgAVEm91XVECgwqaSWfKL7DdKb6X3xMc9PbET+udIXRAYobyKHKV ovPwioTB3/UwMfRIUr5Fr8bVkDMH5gmJfcLNv+UnJntv1PrnLTQ/NUs0kfeEA6z0jUSK pyNg==; dara=google.com ARC-Authentication-Results: i=2; mx.google.com; dkim=pass header.i=@google.com header.s=20230601 header.b=bV+HvPX6; arc=pass (i=1 spf=pass spfdomain=flex--aliceryhl.bounces.google.com dkim=pass dkdomain=google.com dmarc=pass fromdomain=google.com); spf=pass (google.com: domain of linux-kernel+bounces-58301-ouuuleilei=gmail.com@vger.kernel.org designates 2604:1380:45d1:ec00::1 as permitted sender) smtp.mailfrom="linux-kernel+bounces-58301-ouuuleilei=gmail.com@vger.kernel.org"; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com X-Forwarded-Encrypted: i=2; AJvYcCUN+unn1Y31tFY84l42jjw9asiPid507jW+5XnZYf6UaxzAzmykCzY2m+ds2nxlotvH/pJavCkdPWGcd/zQCixhdQRrWA== Received: from ny.mirrors.kernel.org (ny.mirrors.kernel.org. [2604:1380:45d1:ec00::1]) by mx.google.com with ESMTPS id e2-20020ac85982000000b0042c00d88ac2si267501qte.5.2024.02.08.07.49.29 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 Feb 2024 07:49:29 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel+bounces-58301-ouuuleilei=gmail.com@vger.kernel.org designates 2604:1380:45d1:ec00::1 as permitted sender) client-ip=2604:1380:45d1:ec00::1; Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20230601 header.b=bV+HvPX6; arc=pass (i=1 spf=pass spfdomain=flex--aliceryhl.bounces.google.com dkim=pass dkdomain=google.com dmarc=pass fromdomain=google.com); spf=pass (google.com: domain of linux-kernel+bounces-58301-ouuuleilei=gmail.com@vger.kernel.org designates 2604:1380:45d1:ec00::1 as permitted sender) smtp.mailfrom="linux-kernel+bounces-58301-ouuuleilei=gmail.com@vger.kernel.org"; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com Received: from smtp.subspace.kernel.org (wormhole.subspace.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ny.mirrors.kernel.org (Postfix) with ESMTPS id 130861C2281F for ; Thu, 8 Feb 2024 15:49:29 +0000 (UTC) Received: from localhost.localdomain (localhost.localdomain [127.0.0.1]) by smtp.subspace.kernel.org (Postfix) with ESMTP id DF7807EEEA; Thu, 8 Feb 2024 15:48:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="bV+HvPX6" Received: from mail-lj1-f202.google.com (mail-lj1-f202.google.com [209.85.208.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CE9B67CF3A for ; Thu, 8 Feb 2024 15:48:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.208.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707407327; cv=none; b=J2XO6xGcXeVrpK7mCZRYwHTbm5qmKTqMyAPsa5HVB+hm3SCJkAOO16ZGL1vzBs5RNeJ37L261rCp0528B+FGMhSj8gIYjKvnbglgdE2MQo4yIfRO6fdqOqymZP3Hdl03VRkNBtJWdWtx5VCI63eskl+AE78Kst+t7dghW1Mw2BU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707407327; c=relaxed/simple; bh=lCrEJt6bdZ+xsdxDuwJzlgiCY22jzIDidvo8o/5TupA=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=Ipi5NwYYO6LaChWz+3sRJ78I7bCrAQoUAYhWfic89xlxRIWmx1iNgd5G8NAE4KqAw5Qnmd9kWvipEh8jUnlIJUMJHMTw+tJHGzN6gBD4wfoimlHBcyOGwN1E9+8yZ8gpezY2tkMAABiLhH/59RiUHW5YLWyi3OgrAW8ILeqCLvw= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--aliceryhl.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=bV+HvPX6; arc=none smtp.client-ip=209.85.208.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--aliceryhl.bounces.google.com Received: by mail-lj1-f202.google.com with SMTP id 38308e7fff4ca-2d0a7ab562eso184001fa.0 for ; Thu, 08 Feb 2024 07:48:44 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1707407323; x=1708012123; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=MZxfREqmJLVb5yZOS5o3jZQJUZjkOkdbEVLWBie4ZLY=; b=bV+HvPX602v+XWX0jHAUl1yV5lAbHP5vSMOVt6ru4GeWnZp7uYomMsPu2byR0ivNLZ 64XKbUSIPlZTXiSD/wo3clgQHJCzcLn/CVNoPZPUUB4eXVnl5k98qUWVMqrHWP1iCyk9 I4KLytDtT/NkjIhHZXQovz77DvMSopT3IpV91hLYrxVr9hC47f9pnns4WqmKOOeA4BBa FHukAofC5J/1g4zdOfyHy7YE/KG8BR+TfIQEnjznSsomi5C/wYu6g3CvuWQmrS2TDYsb njyFE9jJMvaEHl8q62GQH5n7qF8PnuKPyCa74uBp5/AJrxIKVrQ69BO27sQ/Uk+72IYx XJMA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1707407323; x=1708012123; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=MZxfREqmJLVb5yZOS5o3jZQJUZjkOkdbEVLWBie4ZLY=; b=bCW6s5cgAKQrVUvtmfaAo8xms8RG/yahBOczezOopRI7KUnTTbhZIuT9NSSWmAhS5r OTilS5H8a3A+tDiUy7DMMxkSluSa1+zIltLooWuKx+W2ZtpcPqGofgfuneKH6JpSzEpI Eu5u82IMKZtcW4BB9H8ahm6aEP/lxo2BDbolAYnwFxmb2e58Tuv7rddRWvPr7eIDJYro m1po3Xhb0ONdBgTn9WjrQIRU+zgOEobuUToI6aW0XF7bKUqNtycSWZEnQHsnt08/kti/ 5if26X0TYIruj5Cp4mUmkLYuv2eAEV3AE4W3zI5jLYs42ry0bQPIJBvvh6xf2UYcfqrk smgA== X-Gm-Message-State: AOJu0Yy1hOEXhAboKQdxpdIOLzeLmJXLKVLso91Qs4h+dEEecbw+CWRW s8yKGkwreD1buTf25u1mHwL84wA9IW4hnIOspUzVIoB8vvufhsHlDi8HOuU7Ef9AY834KijOBT1 xluFE+kO+6b2aZA== X-Received: from aliceryhl2.c.googlers.com ([fda3:e722:ac3:cc00:68:949d:c0a8:572]) (user=aliceryhl job=sendgmr) by 2002:a05:651c:542:b0:2d0:9072:e938 with SMTP id q2-20020a05651c054200b002d09072e938mr5249ljp.0.1707407322927; Thu, 08 Feb 2024 07:48:42 -0800 (PST) Date: Thu, 08 Feb 2024 15:47:51 +0000 In-Reply-To: <20240208-alice-mm-v2-0-d821250204a6@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240208-alice-mm-v2-0-d821250204a6@google.com> X-Developer-Key: i=aliceryhl@google.com; a=openpgp; fpr=49F6C1FAA74960F43A5B86A1EE7A392FDE96209F X-Developer-Signature: v=1; a=openpgp-sha256; l=15018; i=aliceryhl@google.com; h=from:subject:message-id; bh=9c+X+VCQkxS1WdW6d5i+iI8c8KAsrHFSOj7xqDOlk7Q=; b=owEBbQKS/ZANAwAKAQRYvu5YxjlGAcsmYgBlxPfSev0FxgN6ijmdsQvYOv+UnwaPgSq7w41oD 9TKOdwIkJOJAjMEAAEKAB0WIQSDkqKUTWQHCvFIvbIEWL7uWMY5RgUCZcT30gAKCRAEWL7uWMY5 RkD0D/9h4bQNWcQlVOexF5lW5P/AI5hzsNTtH8Hr3J45XHedWS8SEIyplKt5EgQsvWIyGObonCL qcFbtebNXaiTSayagTAtB7xc+ny4V7zKFPTI48Sac9Lls3gXzwbgc0udsb8tifotCF+1azMqb9P du2OXQ5UqzgBaLexCpjuPn0jTcgRw/zJwKwGR40+KnLON4ZYNtkt7Xo7K3Y60tbD4RU2k1btkNW qIV7VOwxmKg/80a/t2JHXkukZriX8j4Bo7vT2RWhRT18yybsn1nxLE8EPyj7gfyygf3tvxwHDkp ovt+SWNhO6KT8wo+IaYg8hDYpf9WNPlQf40A3ruWsn2Vfw9QwZCoJW/upYvvGqtTxJ65AWpTiUX GGNfpJcm0qLrCHa5DvMY20zQNw+yukGhF0+Bl6BJPXaAtMz5wq0guQDXNAxtYLBukKPOa47Skad jxTWuO45co3cDY0EqSA4r3Ve4il9NCetzpkDWUVISRU2s6OB56VC6fWbK1getbVrkDuMnSfY7xC S6mrQ7kj5a5MZkKFqcxeAnESQWcid/GqtfrERlzo22tFebTmst8e61T7uwEgBxeAfBwmwyE4p/1 qwitm1RdHnmKppq30Fq/bNdqNdTQHKt7SKqV3VnGtVol/zujHw4RUpNi4bfeCBLD7JzWVtdGCGG xoAGwzviOliOB0g== X-Mailer: b4 0.13-dev-26615 Message-ID: <20240208-alice-mm-v2-1-d821250204a6@google.com> Subject: [PATCH v2 1/4] rust: uaccess: add userspace pointers From: Alice Ryhl To: Miguel Ojeda , Alex Gaynor , Wedson Almeida Filho , Boqun Feng , Gary Guo , " =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= " , Benno Lossin , Andreas Hindborg , Kees Cook , Al Viro , Andrew Morton Cc: Greg Kroah-Hartman , " =?utf-8?q?Arve_Hj?= =?utf-8?q?=C3=B8nnev=C3=A5g?= " , Todd Kjos , Martijn Coenen , Joel Fernandes , Carlos Llamas , Suren Baghdasaryan , Arnd Bergmann , linux-mm@kvack.org, linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, Alice Ryhl , Christian Brauner X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1790346390108127425 X-GMAIL-MSGID: 1790346390108127425 From: Wedson Almeida Filho A pointer to an area in userspace memory, which can be either read-only or read-write. All methods on this struct are safe: invalid pointers return `EFAULT`. Concurrent access, *including data races to/from userspace memory*, is permitted, because fundamentally another userspace thread/process could always be modifying memory at the same time (in the same way that userspace Rust's `std::io` permits data races with the contents of files on disk). In the presence of a race, the exact byte values read/written are unspecified but the operation is well-defined. Kernelspace code should validate its copy of data after completing a read, and not expect that multiple reads of the same address will return the same value. These APIs are designed to make it difficult to accidentally write TOCTOU bugs. Every time you read from a memory location, the pointer is advanced by the length so that you cannot use that reader to read the same memory location twice. Preventing double-fetches avoids TOCTOU bugs. This is accomplished by taking `self` by value to prevent obtaining multiple readers on a given `UserSlicePtr`, and the readers only permitting forward reads. If double-fetching a memory location is necessary for some reason, then that is done by creating multiple readers to the same memory location. Constructing a `UserSlicePtr` performs no checks on the provided address and length, it can safely be constructed inside a kernel thread with no current userspace process. Reads and writes wrap the kernel APIs `copy_from_user` and `copy_to_user`, which check the memory map of the current process and enforce that the address range is within the user range (no additional calls to `access_ok` are needed). This code is based on something that was originally written by Wedson on the old rust branch. It was modified by Alice by removing the `IoBufferReader` and `IoBufferWriter` traits, introducing the `MAX_USER_OP_LEN` constant, and various changes to the comments and documentation. Signed-off-by: Wedson Almeida Filho Co-developed-by: Alice Ryhl Signed-off-by: Alice Ryhl --- rust/helpers.c | 14 +++ rust/kernel/lib.rs | 1 + rust/kernel/uaccess.rs | 314 +++++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 329 insertions(+) diff --git a/rust/helpers.c b/rust/helpers.c index 70e59efd92bc..312b6fcb49d5 100644 --- a/rust/helpers.c +++ b/rust/helpers.c @@ -38,6 +38,20 @@ __noreturn void rust_helper_BUG(void) } EXPORT_SYMBOL_GPL(rust_helper_BUG); +unsigned long rust_helper_copy_from_user(void *to, const void __user *from, + unsigned long n) +{ + return copy_from_user(to, from, n); +} +EXPORT_SYMBOL_GPL(rust_helper_copy_from_user); + +unsigned long rust_helper_copy_to_user(void __user *to, const void *from, + unsigned long n) +{ + return copy_to_user(to, from, n); +} +EXPORT_SYMBOL_GPL(rust_helper_copy_to_user); + void rust_helper_mutex_lock(struct mutex *lock) { mutex_lock(lock); diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs index b89ecf4e97a0..5a03aafcbb69 100644 --- a/rust/kernel/lib.rs +++ b/rust/kernel/lib.rs @@ -50,6 +50,7 @@ pub mod task; pub mod time; pub mod types; +pub mod uaccess; pub mod workqueue; #[doc(hidden)] diff --git a/rust/kernel/uaccess.rs b/rust/kernel/uaccess.rs new file mode 100644 index 000000000000..f07821184bd6 --- /dev/null +++ b/rust/kernel/uaccess.rs @@ -0,0 +1,314 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! User pointers. +//! +//! C header: [`include/linux/uaccess.h`](srctree/include/linux/uaccess.h) + +use crate::{bindings, error::code::*, error::Result}; +use alloc::vec::Vec; +use core::ffi::{c_ulong, c_void}; + +/// A pointer to an area in userspace memory, which can be either read-only or +/// read-write. +/// +/// All methods on this struct are safe: attempting to read or write invalid +/// pointers will return `EFAULT`. Concurrent access, *including data races +/// to/from userspace memory*, is permitted, because fundamentally another +/// userspace thread/process could always be modifying memory at the same time +/// (in the same way that userspace Rust's [`std::io`] permits data races with +/// the contents of files on disk). In the presence of a race, the exact byte +/// values read/written are unspecified but the operation is well-defined. +/// Kernelspace code should validate its copy of data after completing a read, +/// and not expect that multiple reads of the same address will return the same +/// value. +/// +/// These APIs are designed to make it difficult to accidentally write TOCTOU +/// (time-of-check to time-of-use) bugs. Every time a memory location is read, +/// the reader's position is advanced by the read length and the next read will +/// start from there. This helps prevent accidentally reading the same location +/// twice and causing a TOCTOU bug. +/// +/// Creating a [`UserSliceReader`] and/or [`UserSliceWriter`] consumes the +/// `UserSlice`, helping ensure that there aren't multiple readers or writers to +/// the same location. +/// +/// If double-fetching a memory location is necessary for some reason, then that +/// is done by creating multiple readers to the same memory location, e.g. using +/// [`clone_reader`]. +/// +/// # Examples +/// +/// Takes a region of userspace memory from the current process, and modify it +/// by adding one to every byte in the region. +/// +/// ```no_run +/// use alloc::vec::Vec; +/// use core::ffi::c_void; +/// use kernel::error::Result; +/// use kernel::uaccess::UserSlice; +/// +/// pub fn bytes_add_one(uptr: *mut c_void, len: usize) -> Result<()> { +/// let (read, mut write) = UserSlice::new(uptr, len).reader_writer(); +/// +/// let mut buf = Vec::new(); +/// read.read_all(&mut buf)?; +/// +/// for b in &mut buf { +/// *b = b.wrapping_add(1); +/// } +/// +/// write.write_slice(&buf)?; +/// Ok(()) +/// } +/// ``` +/// +/// Example illustrating a TOCTOU (time-of-check to time-of-use) bug. +/// +/// ```no_run +/// use alloc::vec::Vec; +/// use core::ffi::c_void; +/// use kernel::error::{code::EINVAL, Result}; +/// use kernel::uaccess::UserSlice; +/// +/// /// Returns whether the data in this region is valid. +/// fn is_valid(uptr: *mut c_void, len: usize) -> Result { +/// let read = UserSlice::new(uptr, len).reader(); +/// +/// let mut buf = Vec::new(); +/// read.read_all(&mut buf)?; +/// +/// todo!() +/// } +/// +/// /// Returns the bytes behind this user pointer if they are valid. +/// pub fn get_bytes_if_valid(uptr: *mut c_void, len: usize) -> Result> { +/// if !is_valid(uptr, len)? { +/// return Err(EINVAL); +/// } +/// +/// let read = UserSlice::new(uptr, len).reader(); +/// +/// let mut buf = Vec::new(); +/// read.read_all(&mut buf)?; +/// +/// // THIS IS A BUG! The bytes could have changed since we checked them. +/// // +/// // To avoid this kind of bug, don't call `UserSlice::new` multiple +/// // times with the same address. +/// Ok(buf) +/// } +/// ``` +/// +/// [`std::io`]: https://doc.rust-lang.org/std/io/index.html +/// [`clone_reader`]: UserSliceReader::clone_reader +pub struct UserSlice { + ptr: *mut c_void, + length: usize, +} + +impl UserSlice { + /// Constructs a user slice from a raw pointer and a length in bytes. + /// + /// Constructing a [`UserSlice`] performs no checks on the provided address + /// and length, it can safely be constructed inside a kernel thread with no + /// current userspace process. Reads and writes wrap the kernel APIs + /// `copy_from_user` and `copy_to_user`, which check the memory map of the + /// current process and enforce that the address range is within the user + /// range (no additional calls to `access_ok` are needed). + /// + /// Callers must be careful to avoid time-of-check-time-of-use + /// (TOCTOU) issues. The simplest way is to create a single instance of + /// [`UserSlice`] per user memory block as it reads each byte at + /// most once. + pub fn new(ptr: *mut c_void, length: usize) -> Self { + UserSlice { ptr, length } + } + + /// Reads the entirety of the user slice, appending it to the end of the + /// provided buffer. + /// + /// Fails with `EFAULT` if the read encounters a page fault. + pub fn read_all(self, buf: &mut Vec) -> Result<()> { + self.reader().read_all(buf) + } + + /// Constructs a [`UserSliceReader`]. + pub fn reader(self) -> UserSliceReader { + UserSliceReader { + ptr: self.ptr, + length: self.length, + } + } + + /// Constructs a [`UserSliceWriter`]. + pub fn writer(self) -> UserSliceWriter { + UserSliceWriter { + ptr: self.ptr, + length: self.length, + } + } + + /// Constructs both a [`UserSliceReader`] and a [`UserSliceWriter`]. + /// + /// Usually when this is used, you will first read the data, and then + /// overwrite it afterwards. + pub fn reader_writer(self) -> (UserSliceReader, UserSliceWriter) { + ( + UserSliceReader { + ptr: self.ptr, + length: self.length, + }, + UserSliceWriter { + ptr: self.ptr, + length: self.length, + }, + ) + } +} + +/// A reader for [`UserSlice`]. +/// +/// Used to incrementally read from the user slice. +pub struct UserSliceReader { + ptr: *mut c_void, + length: usize, +} + +impl UserSliceReader { + /// Skip the provided number of bytes. + /// + /// Returns an error if skipping more than the length of the buffer. + pub fn skip(&mut self, num_skip: usize) -> Result { + // Update `self.length` first since that's the fallible part of this + // operation. + self.length = self.length.checked_sub(num_skip).ok_or(EFAULT)?; + self.ptr = self.ptr.wrapping_byte_add(num_skip); + Ok(()) + } + + /// Create a reader that can access the same range of data. + /// + /// Reading from the clone does not advance the current reader. + /// + /// The caller should take care to not introduce TOCTOU issues, as described + /// in the documentation for [`UserSlice`]. + pub fn clone_reader(&self) -> UserSliceReader { + UserSliceReader { + ptr: self.ptr, + length: self.length, + } + } + + /// Returns the number of bytes left to be read from this reader. + /// + /// Note that even reading less than this number of bytes may fail. + pub fn len(&self) -> usize { + self.length + } + + /// Returns `true` if no data is available in the io buffer. + pub fn is_empty(&self) -> bool { + self.length == 0 + } + + /// Reads raw data from the user slice into a raw kernel buffer. + /// + /// Fails with `EFAULT` if the read encounters a page fault. + /// + /// # Safety + /// + /// The `out` pointer must be valid for writing `len` bytes. + pub unsafe fn read_raw(&mut self, out: *mut u8, len: usize) -> Result { + if len > self.length { + return Err(EFAULT); + } + let Ok(len_ulong) = c_ulong::try_from(len) else { + return Err(EFAULT); + }; + // SAFETY: The caller promises that `out` is valid for writing `len` bytes. + let res = unsafe { bindings::copy_from_user(out.cast::(), self.ptr, len_ulong) }; + if res != 0 { + return Err(EFAULT); + } + // Userspace pointers are not directly dereferencable by the kernel, so + // we cannot use `add`, which has C-style rules for defined behavior. + self.ptr = self.ptr.wrapping_byte_add(len); + self.length -= len; + Ok(()) + } + + /// Reads the entirety of the user slice, appending it to the end of the + /// provided buffer. + /// + /// Fails with `EFAULT` if the read encounters a page fault. + pub fn read_all(mut self, buf: &mut Vec) -> Result<()> { + buf.try_reserve(self.length)?; + + // SAFETY: The call to `try_reserve` was successful, so the spare + // capacity is at least `self.length` bytes long. + unsafe { self.read_raw(buf.spare_capacity_mut().as_mut_ptr().cast(), self.length)? }; + + // SAFETY: Since the call to `read_raw` was successful, so the next + // `len` bytes of the vector have been initialized. + unsafe { buf.set_len(buf.len() + self.length) }; + Ok(()) + } +} + +/// A writer for [`UserSlice`]. +/// +/// Used to incrementally write into the user slice. +pub struct UserSliceWriter { + ptr: *mut c_void, + length: usize, +} + +impl UserSliceWriter { + /// Returns the amount of space remaining in this buffer. + /// + /// Note that even writing less than this number of bytes may fail. + pub fn len(&self) -> usize { + self.length + } + + /// Returns `true` if no more data can be written to this buffer. + pub fn is_empty(&self) -> bool { + self.length == 0 + } + + /// Writes raw data to this user pointer from a raw kernel buffer. + /// + /// Fails with `EFAULT` if the write encounters a page fault. + /// + /// # Safety + /// + /// The `data` pointer must be valid for reading `len` bytes. + pub unsafe fn write_raw(&mut self, data: *const u8, len: usize) -> Result { + if len > self.length { + return Err(EFAULT); + } + let Ok(len_ulong) = c_ulong::try_from(len) else { + return Err(EFAULT); + }; + let res = unsafe { bindings::copy_to_user(self.ptr, data.cast::(), len_ulong) }; + if res != 0 { + return Err(EFAULT); + } + // Userspace pointers are not directly dereferencable by the kernel, so + // we cannot use `add`, which has C-style rules for defined behavior. + self.ptr = self.ptr.wrapping_byte_add(len); + self.length -= len; + Ok(()) + } + + /// Writes the provided slice to this user pointer. + /// + /// Fails with `EFAULT` if the write encounters a page fault. + pub fn write_slice(&mut self, data: &[u8]) -> Result { + let len = data.len(); + let ptr = data.as_ptr(); + // SAFETY: The pointer originates from a reference to a slice of length + // `len`, so the pointer is valid for reading `len` bytes. + unsafe { self.write_raw(ptr, len) } + } +} From patchwork Thu Feb 8 15:47:52 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alice Ryhl X-Patchwork-Id: 198450 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a05:7300:50ea:b0:106:860b:bbdd with SMTP id r10csp259982dyd; Thu, 8 Feb 2024 07:49:33 -0800 (PST) X-Forwarded-Encrypted: i=3; AJvYcCXjFdB0fcftDeyLZH4dI8JL6H72sbgMVPn1+QfHl0RU4FMOFGAhSVOpc6lXljny/YFAoJtyZBsA4MTTFhmNiaVuHz8N6Q== X-Google-Smtp-Source: AGHT+IG4i8WnzCB+28ElmM97vbSgiwZS7s81uOSl21jSH/lNj1HZrXpM037Lb8KMWqLl2UhJRAUO X-Received: by 2002:a05:620a:15a9:b0:785:5b0b:ef75 with SMTP id f9-20020a05620a15a900b007855b0bef75mr3936657qkk.29.1707407373543; Thu, 08 Feb 2024 07:49:33 -0800 (PST) ARC-Seal: i=2; a=rsa-sha256; t=1707407373; cv=pass; d=google.com; s=arc-20160816; b=Fyu89UQcfiiVjgWYIH9ph9gfXh020wtpBsidXP2bdqT0bFm+TY2BZaaIS5Ez5u9JXi Yq43SSCIaNMPmq3iMAzfb/JBNT/MmcaweWgEvDxtFj0m/JRM3iizwrCRLypIgxyeb+vY L7h0jpPlruRLg5wS+XHlt2DTDJdmJxuppnr0CgzuPz+RE5UWiBXYSnOOBzMCGqqgKyR/ 32wN2CE94ZI+6tF7LNrLvv/ESivvH0kS3iPI2rsIk39eyCO/ne+a3khshKAdTyeeGskk XyUsvHsY7WbriAz+xg+vYwffeTcr+7Cm4PUK4la2ieQV3HTDUbXMQctdkLUcecxoG421 SOJw== ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=cc:to:from:subject:message-id:references:mime-version :list-unsubscribe:list-subscribe:list-id:precedence:in-reply-to:date :dkim-signature; bh=1MPoST0g8AYkDBhG2VsbV1sslw+0urv81QcaeUn+juw=; fh=lA9vuezNrZG/fL3+HquQxI8ddN/czGsBwgSlTzg9tRc=; b=0BYx090Uk6ER3+ozSwCCWtAeRsa4kiTYQQsMfJf6UM7AI1/D2rXxs/yP1XOVRUm4Pc vaDicwmQa2mZNDQyeySPUEOh32xIBmdVMBu+x6JTGTAXoZO9eQHmwdAC3jUWebD0x6WL CWH8iDv/NMU5YRNKGfJ4RxyYs7FybejP7tsO2fFlf/azTmAu/JOBCgAt2+YayQkZihsg xCOfXFHpkWYyI/cG9sZ53quEVNAlgYxLju9scarmNJFZOU1/wC6rQS30fIyKyt+tnFbw VvkJYI+0ZMnPt/gOZ4bfV/UL3G82+CyjbxPhS62XuS2fZLSXy/KA34cA0pAPh3RoREXy 6SiQ==; dara=google.com ARC-Authentication-Results: i=2; mx.google.com; dkim=pass header.i=@google.com header.s=20230601 header.b=mhcle2eZ; arc=pass (i=1 spf=pass spfdomain=flex--aliceryhl.bounces.google.com dkim=pass dkdomain=google.com dmarc=pass fromdomain=google.com); spf=pass (google.com: domain of linux-kernel+bounces-58302-ouuuleilei=gmail.com@vger.kernel.org designates 2604:1380:45d1:ec00::1 as permitted sender) smtp.mailfrom="linux-kernel+bounces-58302-ouuuleilei=gmail.com@vger.kernel.org"; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com X-Forwarded-Encrypted: i=2; AJvYcCVQtb/N6lQb+k2qrt+EFWCeO1ImYkuWsMWG8LTWG2wOuTPC1WYbfg+i5uB6p9zYU8TFK2u5eryCco6BgLKbsXOn99cITw== Received: from ny.mirrors.kernel.org (ny.mirrors.kernel.org. [2604:1380:45d1:ec00::1]) by mx.google.com with ESMTPS id e6-20020a05620a208600b007858e9c0716si221374qka.488.2024.02.08.07.49.33 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 Feb 2024 07:49:33 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel+bounces-58302-ouuuleilei=gmail.com@vger.kernel.org designates 2604:1380:45d1:ec00::1 as permitted sender) client-ip=2604:1380:45d1:ec00::1; Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20230601 header.b=mhcle2eZ; arc=pass (i=1 spf=pass spfdomain=flex--aliceryhl.bounces.google.com dkim=pass dkdomain=google.com dmarc=pass fromdomain=google.com); spf=pass (google.com: domain of linux-kernel+bounces-58302-ouuuleilei=gmail.com@vger.kernel.org designates 2604:1380:45d1:ec00::1 as permitted sender) smtp.mailfrom="linux-kernel+bounces-58302-ouuuleilei=gmail.com@vger.kernel.org"; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com Received: from smtp.subspace.kernel.org (wormhole.subspace.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ny.mirrors.kernel.org (Postfix) with ESMTPS id 388281C22848 for ; Thu, 8 Feb 2024 15:49:33 +0000 (UTC) Received: from localhost.localdomain (localhost.localdomain [127.0.0.1]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 93BEC7EEF5; Thu, 8 Feb 2024 15:48:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="mhcle2eZ" Received: from mail-yb1-f201.google.com (mail-yb1-f201.google.com [209.85.219.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BC4F17D3F6 for ; Thu, 8 Feb 2024 15:48:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.219.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707407329; cv=none; b=IKXT+sMeVdMeoGX7hLgpPT4sRXWnItzkFwEN9VfHzxrSpxgL8sRO9+SCg5ch+Q2dtnTSX/DU8yYhrK6CgOp76heSV05XDYGKoGtY+AVaTio1xtmzFNG9u+NMTnYJblLqwdMCKyqtS88igzI+mxeXDqnvWUrWtNeoTpzQzwPIe0w= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707407329; c=relaxed/simple; bh=JiNY7UD5yChmAMASqdU3YDYjcAqL6joPoUB8j2lzZeY=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=NtaWVYqmfCS+cKFoahN8/MINzKLOtIGkMRxWV8Jvej8kizhSFA9s53k7We/gxZjrElJWwoztTiTvL2p00dq2GtbHvbx6xvcmNbjNcIP6ZC7dMy/a4fJX/VOQjdTjGkuseVAPXpemsG4ItdeEbxUAstAbHfaJKAnWsBv+DYDUphw= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--aliceryhl.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=mhcle2eZ; arc=none smtp.client-ip=209.85.219.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--aliceryhl.bounces.google.com Received: by mail-yb1-f201.google.com with SMTP id 3f1490d57ef6-dc74ac7d015so302251276.0 for ; Thu, 08 Feb 2024 07:48:46 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1707407326; x=1708012126; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=1MPoST0g8AYkDBhG2VsbV1sslw+0urv81QcaeUn+juw=; b=mhcle2eZCdtlsc9l4HKuZLLrbhdElCfqlSSGlxuTHyUP2BtmZ7p5AU0/XAD3sUDP5p u9bTEkLBQoOOPkSRAdoTWHRxwZpsK+7guY5NPpB3rMJSh3fSnPVAr2hT7Ddrz56yZk4G DNi+4+GaQuUZv8oul/z5l12kkLF7XXIphLgBIGVE4TafxE4izKiHQOcD0A6PDWSKKaj+ jrgpOBsFxB5rg0mSuS9nHwcpARZTnqmBB0QrchKn1U6UpW8tyYvTA9USN7ejt4Ww4PiI l2JdWLDXvXhkVWx+jF1sFcDNNpTrQTrB6SVJCgbAVyepNaLwr6F0+BMx3ukzQugPyx1U elJQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1707407326; x=1708012126; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=1MPoST0g8AYkDBhG2VsbV1sslw+0urv81QcaeUn+juw=; b=vnEdLScBDriw7gvyxiIj8e6BjiMyKP0sHt3VJ96zPbRor71SZCSQ3S+bCRJ2YeQ3BG aYmynycneEw5oFQwJxeCGvS+eBQJY50PrBfJqbhWRpTMGvfZaR9LYBQ49swozdsUVg4P Qh0vQw+mKT0EeJR0aVocnmBNA5LMqyTPpH76813uWZZIILyzMOWMoGYMA88u+etfcLMf dsPDmip8NpDxCOOPoH89U2eTidxpTcHPgKEIIvzGlxIYH02Wl3SKlTpiYA2AG0uV1V8t nQ1OO8Gt7VKKyCZ94kOLfFmZ9t6rkOXOMbEl4EPxgrX7e6oiZNASAFxfcuyiy5L+diSw UMVw== X-Forwarded-Encrypted: i=1; AJvYcCXGv9O/C6J3mkE+DMBi9GnfD1MiecFkbglClZpOq/CszXgTdPD+8l7OE6DLXvc91ccIj7JKBOkZ5diL1t3rZy9XNgiLrOEI0L4q7FbE X-Gm-Message-State: AOJu0YzU4IiJofZhPTPml3hrV2FUOlmGWGWbTJ8eM1U5mb1W8px1xWZy PrNIe2XsEM1MkEo0y1hCtppuuVsAFKLzguDJ4yt5pwNJSl9vVyJhs/fwqAAFhmA1GqjF1VflF5d xT43zYmgj8oA/Zg== X-Received: from aliceryhl2.c.googlers.com ([fda3:e722:ac3:cc00:68:949d:c0a8:572]) (user=aliceryhl job=sendgmr) by 2002:a05:6902:1b88:b0:dc6:ec15:5f6f with SMTP id ei8-20020a0569021b8800b00dc6ec155f6fmr340204ybb.6.1707407325732; Thu, 08 Feb 2024 07:48:45 -0800 (PST) Date: Thu, 08 Feb 2024 15:47:52 +0000 In-Reply-To: <20240208-alice-mm-v2-0-d821250204a6@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240208-alice-mm-v2-0-d821250204a6@google.com> X-Developer-Key: i=aliceryhl@google.com; a=openpgp; fpr=49F6C1FAA74960F43A5B86A1EE7A392FDE96209F X-Developer-Signature: v=1; a=openpgp-sha256; l=4643; i=aliceryhl@google.com; h=from:subject:message-id; bh=5Gt2wgkxBTJYGkfZMpeUeH1SE3k+76BKAUtR156EeQ0=; b=owEBbQKS/ZANAwAKAQRYvu5YxjlGAcsmYgBlxPfTuQDsKBYaMhTNxSmNY7PLIkKVkVnXBgh2h FRUyBw0ZDOJAjMEAAEKAB0WIQSDkqKUTWQHCvFIvbIEWL7uWMY5RgUCZcT30wAKCRAEWL7uWMY5 RrCTEAC0DaTqeHguZBQPjq0PPyT3rF4dgf8yp7QxrvoiztTXntK43kWYjtU6x4CoxRG+Lfp6NCx ahAklS4wQAQLPnwFB7n84XdxDQiFmRKJNiDdfrZtYj9+37q3KZnmt4B0N9TU2/tv2596QUrr7g5 8FHFh2cgpuJV3O8Gb9U2movzF0Y0EBrHeg7p8AhkHNs9taPgH7S885BL8gs2rLzgkPYKf1sNY/C 5hA4aJH/a9yzOjOWaRmFlkB1kZRm4KiftHLzWE3u3ZMHhfwXiLR9fMIvCjoKUcGfYAYHunM3gkc guKnoQhyh9Jo/b2AwXr5KVNQFbWpKIpRAFkieNgtgtxoFyYag+hQzN+8zEukWaMv/Tcw5nn2l7G fTgEJjZLgfS18WZg8tIiwBGCpb7CGApvnSE6czD3O116L7MaFZgsyQ18xEcrnwnisEh8jGkEpRS mcAYoaxEnBgCGDCF7wRrOWQGk60Sl2TD38A8wJYuhuz/XZ5kzXa0TAu7H4id2ZqjQ2Vt4E+07s6 ObN4KfrT1dPCAm9M80Bn1u4Emonb0v4S5nykU0Awlen1fu+wttxiLdNlG+zwcaHELAt39pm2Spf PfDE4plBBAgcYG75I1TyaKWvyIb0JcNlLzTdXEskioQXW+n0ByNOrNohTMoZoXiY2vxVWX0YcK/ CE7RtNd2PYweYRQ== X-Mailer: b4 0.13-dev-26615 Message-ID: <20240208-alice-mm-v2-2-d821250204a6@google.com> Subject: [PATCH v2 2/4] uaccess: always export _copy_[from|to]_user with CONFIG_RUST From: Alice Ryhl To: Miguel Ojeda , Alex Gaynor , Wedson Almeida Filho , Boqun Feng , Gary Guo , " =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= " , Benno Lossin , Andreas Hindborg , Kees Cook , Al Viro , Andrew Morton Cc: Greg Kroah-Hartman , " =?utf-8?q?Arve_Hj?= =?utf-8?q?=C3=B8nnev=C3=A5g?= " , Todd Kjos , Martijn Coenen , Joel Fernandes , Carlos Llamas , Suren Baghdasaryan , Arnd Bergmann , linux-mm@kvack.org, linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, Alice Ryhl , Christian Brauner X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1790346394212986781 X-GMAIL-MSGID: 1790346394212986781 From: Arnd Bergmann Rust code needs to be able to access _copy_from_user and _copy_to_user so that it can skip the check_copy_size check in cases where the length is known at compile-time, mirroring the logic for when C code will skip check_copy_size. To do this, we ensure that exported versions of these methods are available when CONFIG_RUST is enabled. Signed-off-by: Arnd Bergmann Signed-off-by: Alice Ryhl --- include/linux/uaccess.h | 37 +++++++++++++++++++++++-------------- lib/usercopy.c | 30 ++++-------------------------- 2 files changed, 27 insertions(+), 40 deletions(-) diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h index 3064314f4832..835aa175d0ee 100644 --- a/include/linux/uaccess.h +++ b/include/linux/uaccess.h @@ -138,13 +138,18 @@ __copy_to_user(void __user *to, const void *from, unsigned long n) return raw_copy_to_user(to, from, n); } -#ifdef INLINE_COPY_FROM_USER static inline __must_check unsigned long -_copy_from_user(void *to, const void __user *from, unsigned long n) +_inline_copy_from_user(void *to, const void __user *from, unsigned long n) { unsigned long res = n; might_fault(); if (!should_fail_usercopy() && likely(access_ok(from, n))) { + /* + * Ensure that bad access_ok() speculation will not + * lead to nasty side effects *after* the copy is + * finished: + */ + barrier_nospec(); instrument_copy_from_user_before(to, from, n); res = raw_copy_from_user(to, from, n); instrument_copy_from_user_after(to, from, n, res); @@ -153,14 +158,11 @@ _copy_from_user(void *to, const void __user *from, unsigned long n) memset(to + (n - res), 0, res); return res; } -#else extern __must_check unsigned long _copy_from_user(void *, const void __user *, unsigned long); -#endif -#ifdef INLINE_COPY_TO_USER static inline __must_check unsigned long -_copy_to_user(void __user *to, const void *from, unsigned long n) +_inline_copy_to_user(void __user *to, const void *from, unsigned long n) { might_fault(); if (should_fail_usercopy()) @@ -171,25 +173,32 @@ _copy_to_user(void __user *to, const void *from, unsigned long n) } return n; } -#else extern __must_check unsigned long _copy_to_user(void __user *, const void *, unsigned long); -#endif static __always_inline unsigned long __must_check copy_from_user(void *to, const void __user *from, unsigned long n) { - if (check_copy_size(to, n, false)) - n = _copy_from_user(to, from, n); - return n; + if (!check_copy_size(to, n, false)) + return n; +#ifdef INLINE_COPY_FROM_USER + return _inline_copy_from_user(to, from, n); +#else + return _copy_from_user(to, from, n); +#endif } static __always_inline unsigned long __must_check copy_to_user(void __user *to, const void *from, unsigned long n) { - if (check_copy_size(from, n, true)) - n = _copy_to_user(to, from, n); - return n; + if (!check_copy_size(from, n, true)) + return n; + +#ifdef INLINE_COPY_TO_USER + return _inline_copy_to_user(to, from, n); +#else + return _copy_to_user(to, from, n); +#endif } #ifndef copy_mc_to_kernel diff --git a/lib/usercopy.c b/lib/usercopy.c index d29fe29c6849..de7f30618293 100644 --- a/lib/usercopy.c +++ b/lib/usercopy.c @@ -7,40 +7,18 @@ /* out-of-line parts */ -#ifndef INLINE_COPY_FROM_USER +#if !defined(INLINE_COPY_FROM_USER) || defined(CONFIG_RUST) unsigned long _copy_from_user(void *to, const void __user *from, unsigned long n) { - unsigned long res = n; - might_fault(); - if (!should_fail_usercopy() && likely(access_ok(from, n))) { - /* - * Ensure that bad access_ok() speculation will not - * lead to nasty side effects *after* the copy is - * finished: - */ - barrier_nospec(); - instrument_copy_from_user_before(to, from, n); - res = raw_copy_from_user(to, from, n); - instrument_copy_from_user_after(to, from, n, res); - } - if (unlikely(res)) - memset(to + (n - res), 0, res); - return res; + return _inline_copy_from_user(to, from, n); } EXPORT_SYMBOL(_copy_from_user); #endif -#ifndef INLINE_COPY_TO_USER +#if !defined(INLINE_COPY_TO_USER) || defined(CONFIG_RUST) unsigned long _copy_to_user(void __user *to, const void *from, unsigned long n) { - might_fault(); - if (should_fail_usercopy()) - return n; - if (likely(access_ok(to, n))) { - instrument_copy_to_user(to, from, n); - n = raw_copy_to_user(to, from, n); - } - return n; + return _inline_copy_to_user(to, from, n); } EXPORT_SYMBOL(_copy_to_user); #endif From patchwork Thu Feb 8 15:47:53 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alice Ryhl X-Patchwork-Id: 198451 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a05:7300:50ea:b0:106:860b:bbdd with SMTP id r10csp260176dyd; Thu, 8 Feb 2024 07:49:51 -0800 (PST) X-Forwarded-Encrypted: i=3; AJvYcCU82iP3/RFaOQ4q68tbNUVMMq5y+VYIw7KIswGC+PZLlpvltKvN+pjDdNv7rb9/ax+ritafz5N5AKDlJcivT01Ac2hJoA== X-Google-Smtp-Source: AGHT+IGtqB3f7Rqfwls4ZKWVeptm74R6IJnku40XbdQaSN4o1lVTj6ey+q9Tn4mWQu0JcXEzLxg9 X-Received: by 2002:a25:b93:0:b0:dc6:b617:a28c with SMTP id 141-20020a250b93000000b00dc6b617a28cmr8637630ybl.5.1707407391028; Thu, 08 Feb 2024 07:49:51 -0800 (PST) ARC-Seal: i=2; a=rsa-sha256; t=1707407390; cv=pass; d=google.com; s=arc-20160816; b=FLdXxEgAIv6riQMIhtl65pdK7K7FqrKa62qDODYQs90QW+38RTTUJEG3QGHL2DjBuM tsEJ1UtbouiecMMUD1iuhPzi89vXLPyG9hGcpNOZluUf7C0WdZ2kH8PNyLgA9gf6l15Z 7liI9ZQfxahgTvsplUeTw/UWg6nnbjqfetmnUZBs1z+aDfypg99ujgXwZ3aPuYBcTIcU 3mWgMkF2Ewf0LGaCE3aAAJXSYgSRCjecAe7N8GTA4c9F6OPP3AP3Y62+ndjBFrbb1NJg fvzjo/GpAdHWicjrhEZ2oG6FpaoU4XXvjhE428jUGoAVZKEpfctlsyJc0/VvUPgwsQ24 RrKA== ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=cc:to:from:subject:message-id:references:mime-version :list-unsubscribe:list-subscribe:list-id:precedence:in-reply-to:date :dkim-signature; bh=flngb/LA8uzIdl5igbJEwBtu/PZHJPBIGQxF8CY4PhE=; fh=nkKhEze422jJW2G9MRkFFWPL2azhCzaCCZvvO5mwx74=; b=hJ2KuZizi6PF2kUy+JTUvU5MJTvONksJ4i4CBJmZiYPJ09t2eQKG9MHYXWWCJRSE+f NxG2NGh9OMlRtsBNwclcZMEdujtEfj3D+erbo9loLWkdr7cJ62Bhfzb194gcorf3+HZT DUmpflH/YXo/STNLPwYnI7PlYCID8DrsQ+yG2J6xfhpI3rnlF/1ZBxWblRP39NHattD4 81KhCtRc5K7ywHOna2StxAA21/EnK6OhEHx4w+7PImZKscU/pxMEgrb9+X1gM0YElYuj UMBCWkr8Wz/NCQvcdIqgTaJYau4279YaGFcJOWK/IXavJHjcJtyaXX9NRuHexnW7f2aC WlgQ==; dara=google.com ARC-Authentication-Results: i=2; mx.google.com; dkim=pass header.i=@google.com header.s=20230601 header.b=d86CKmSX; arc=pass (i=1 spf=pass spfdomain=flex--aliceryhl.bounces.google.com dkim=pass dkdomain=google.com dmarc=pass fromdomain=google.com); spf=pass (google.com: domain of linux-kernel+bounces-58303-ouuuleilei=gmail.com@vger.kernel.org designates 2604:1380:45d1:ec00::1 as permitted sender) smtp.mailfrom="linux-kernel+bounces-58303-ouuuleilei=gmail.com@vger.kernel.org"; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com X-Forwarded-Encrypted: i=2; AJvYcCU0i10qBzghaR77BCSySYOOOGO62zXXYwSkaNX5K6SrXzZi0kldsAwfN6gdXdYuuMMH+plCPbuLf5XGtjwV8goRMnv1+w== Received: from ny.mirrors.kernel.org (ny.mirrors.kernel.org. [2604:1380:45d1:ec00::1]) by mx.google.com with ESMTPS id j27-20020a05620a147b00b007858b5c5ae1si232014qkl.534.2024.02.08.07.49.50 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 Feb 2024 07:49:50 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel+bounces-58303-ouuuleilei=gmail.com@vger.kernel.org designates 2604:1380:45d1:ec00::1 as permitted sender) client-ip=2604:1380:45d1:ec00::1; Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20230601 header.b=d86CKmSX; arc=pass (i=1 spf=pass spfdomain=flex--aliceryhl.bounces.google.com dkim=pass dkdomain=google.com dmarc=pass fromdomain=google.com); spf=pass (google.com: domain of linux-kernel+bounces-58303-ouuuleilei=gmail.com@vger.kernel.org designates 2604:1380:45d1:ec00::1 as permitted sender) smtp.mailfrom="linux-kernel+bounces-58303-ouuuleilei=gmail.com@vger.kernel.org"; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com Received: from smtp.subspace.kernel.org (wormhole.subspace.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ny.mirrors.kernel.org (Postfix) with ESMTPS id B1DCF1C2255C for ; Thu, 8 Feb 2024 15:49:50 +0000 (UTC) Received: from localhost.localdomain (localhost.localdomain [127.0.0.1]) by smtp.subspace.kernel.org (Postfix) with ESMTP id B34BC7CF30; Thu, 8 Feb 2024 15:48:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="d86CKmSX" Received: from mail-yb1-f201.google.com (mail-yb1-f201.google.com [209.85.219.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 75E0A7D41C for ; Thu, 8 Feb 2024 15:48:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.219.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707407332; cv=none; b=SvYdKrvC6T751MQl3tPW0M7RkfYfMQq+DkCynz35+EWfceR/tAbMm7OUAYixCG8AO+Y7POWhBEcvhJxwfFoRn4WMrB9tGpJHg8WARe6MmHiUxykT+K3PensXjG+GCw5g8nH6JTlxNeiorll7zHF2ojlFiywXNyCQIv6JBUgbR3w= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707407332; c=relaxed/simple; bh=0g42SIX3ikqPGex8zhN70IRWhPIkHg4UCYLIFxFrPfU=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=K++eTKJW/gBp/jKvP0jus/mhyipTYDcT+FF+qEntDFcQzhAyl4BT9fYKj40rgN+psAN2pwJa3T5MFswJBUkZO78vGTbWzzM4VTb7Zq1cNozNbeEUMIkfsNg9GG3akSV99e8NTM7OnOppSKjsBIpHuIm5z6Xu/oauugir6bbpdug= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--aliceryhl.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=d86CKmSX; arc=none smtp.client-ip=209.85.219.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--aliceryhl.bounces.google.com Received: by mail-yb1-f201.google.com with SMTP id 3f1490d57ef6-dbe9e13775aso3330566276.1 for ; Thu, 08 Feb 2024 07:48:49 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1707407328; x=1708012128; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=flngb/LA8uzIdl5igbJEwBtu/PZHJPBIGQxF8CY4PhE=; b=d86CKmSXMLMGUgnIQBGcw6GrfKSqp1/AoVlpRNQmakY/I3lwnBiJu09CCTPKS2c2Nn BYTnfFrCPHim7XpzxHH6nwmFwFP7orFH4NoPt3haSXpbRfRZS5+G6yaoNA7yCmwaVq9O 4RC+Q1ieT6fHkp0WqcZBLKEdPbSL3Wuxq6dIf5lnybgGkBQCNnSM3B+VSq2ZSTRVov0n 9JnExyda+TZxgQISJS0E3eD7N258qcPpvjKVCQ+a8FVDZ84Qt0OzexJt84fLEVIYunfI 1mfUoIU+t0/8y5vpS+iA3OtkkHuASBfdqM1Eb86Y7Cvp+GXWwERHJiwxPCX4ufwq76BU TvgQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1707407328; x=1708012128; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=flngb/LA8uzIdl5igbJEwBtu/PZHJPBIGQxF8CY4PhE=; b=p3HgdUU3snERyy06QAuprbSQdxZfTSvmackMWNqdDlqvDho13JKnyRM0hrVuWVKv0I kJhI5phsq5OQ5LG9EcmmjJRh2LAd6RuACdE3XeVqbHuAGMyDzdCF6qRF6b90efnjcNZ/ HU6m+vaYoKeyN9DA6N1VmbF1pmbgJaU+KXMQRL3haS4Yz53/KeEj8GbuwvVsc6/a68pu 8ZPUNLifNUTq9l9mUDNi8G0xCM6KTT/9ARgcYoXrTIwlcTpccIFJ3oRXpCd0bMIs5Ade nukSNVafo3l7vbCQCdtZBr809Ze7VaQYYbnRVBQ2V6mgGAR/QGgsixeMvvQUyINc7OoH dDdA== X-Forwarded-Encrypted: i=1; AJvYcCU8cGIZ3cUgfaKWdYzcDtJdfCOzXZ5v3uqIWbksYrBwI72NNiaIlfAutYNGHYiX8h8tqWUyoMI8kF6Hm1FexL7crfd7v7z9L2ANrKoT X-Gm-Message-State: AOJu0YxhyXz6IQvzKLdBfgIO502fL2HLW8zlCtAjx8w/M7sjpEc9SrFa RrtrB59nc+2AtUbwyFeYPzyJw3PSgb7CEOHuNytVola1kGlZnc2cg3wffMn+jPESvYC40ZeU33S 5adjQJlFDG8BsKA== X-Received: from aliceryhl2.c.googlers.com ([fda3:e722:ac3:cc00:68:949d:c0a8:572]) (user=aliceryhl job=sendgmr) by 2002:a05:6902:2186:b0:dc6:eea0:1578 with SMTP id dl6-20020a056902218600b00dc6eea01578mr2142900ybb.13.1707407328528; Thu, 08 Feb 2024 07:48:48 -0800 (PST) Date: Thu, 08 Feb 2024 15:47:53 +0000 In-Reply-To: <20240208-alice-mm-v2-0-d821250204a6@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240208-alice-mm-v2-0-d821250204a6@google.com> X-Developer-Key: i=aliceryhl@google.com; a=openpgp; fpr=49F6C1FAA74960F43A5B86A1EE7A392FDE96209F X-Developer-Signature: v=1; a=openpgp-sha256; l=8719; i=aliceryhl@google.com; h=from:subject:message-id; bh=0g42SIX3ikqPGex8zhN70IRWhPIkHg4UCYLIFxFrPfU=; b=owEBbQKS/ZANAwAKAQRYvu5YxjlGAcsmYgBlxPfTuOB96U/Lj40fHe9/xmDSElLomqfJO0cdJ oS0DmyNDKGJAjMEAAEKAB0WIQSDkqKUTWQHCvFIvbIEWL7uWMY5RgUCZcT30wAKCRAEWL7uWMY5 RhsAEACE9BLmNvDC79FcWLHl6NT6PpjTFGYzMx6E6caaaLeVuWDJ6hhRZ+WM5x1fY68NMh4jTze sSCcxDNl9i1VJtQx5DN5Dvxw8ZOheHmix6sYH2u6nzHLQB+ka5eT56u/j1JvtGhjDE+JN/FtLLi Ku7kHIhYAmrNWQ71Ccpdl9TmLyg9b+F3CewVZsPpMR8BiA7M8IMyElJgb2Qy8QK+2UyagQNkNck vUAOTl7XVhllYkzh7aNkH++irEYMD7l1Pzq6i0ark1Oh5QLENHbz6p9GrtKtibC8Y31d+5ahqGQ ofpIQmg4DLhYUbcdbSgHuvaSvA2aNvb3I4hI/CHF3ItH5GKHeZ1II37sZzwtQIDhW/jx3tI7cM7 8fyu+b1eAvqo91GJyU9GKh6nyq+s/ft37vk5y7EsOCZVStX5wJkMW/fhvtHOQOQhIYU+yta/+3l gstUIDdyj8IP4sslt6FxHuMV/LEvQYzA/gw6mcz3plT02alcLP8CCjofOcmuw2A0U4BQkqvt4vf gdBiHa/nU9fHplEV10UtrZrwIchhpw29NoAzW9Log+xqOYBfvEJED/LBawfR0KQXivClAID7XvG 9u9w6oeJ6ZDYHCsI/brqznI4Um6gkWFG6YsPqFD1HyYPlG6VCo28FcfELn8as/Nz5rkkkTm8zjW 7WgDIC5F4sLMOdA== X-Mailer: b4 0.13-dev-26615 Message-ID: <20240208-alice-mm-v2-3-d821250204a6@google.com> Subject: [PATCH v2 3/4] rust: uaccess: add typed accessors for userspace pointers From: Alice Ryhl To: Miguel Ojeda , Alex Gaynor , Wedson Almeida Filho , Boqun Feng , Gary Guo , " =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= " , Benno Lossin , Andreas Hindborg , Kees Cook , Al Viro , Andrew Morton Cc: Greg Kroah-Hartman , " =?utf-8?q?Arve_Hj?= =?utf-8?q?=C3=B8nnev=C3=A5g?= " , Todd Kjos , Martijn Coenen , Joel Fernandes , Carlos Llamas , Suren Baghdasaryan , Arnd Bergmann , linux-mm@kvack.org, linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, Alice Ryhl , Christian Brauner X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1790346412362132002 X-GMAIL-MSGID: 1790346412362132002 Add safe methods for reading and writing Rust values to and from userspace pointers. The C methods for copying to/from userspace use a function called `check_object_size` to verify that the kernel pointer is not dangling. However, this check is skipped when the length is a compile-time constant, with the assumption that such cases trivially have a correct kernel pointer. In this patch, we apply the same optimization to the typed accessors. For both methods, the size of the operation is known at compile time to be size_of of the type being read or written. Since the C side doesn't provide a variant that skips only this check, we create custom helpers for this purpose. The majority of reads and writes to userspace pointers in the Rust Binder driver uses these accessor methods. Benchmarking has found that skipping the `check_object_size` check makes a big difference for the cases being skipped here. (And that the check doesn't make a difference for the cases that use the raw read/write methods.) This code is based on something that was originally written by Wedson on the old rust branch. It was modified by Alice to skip the `check_object_size` check, and to update various comments, including the notes about kernel pointers in `WritableToBytes`. Co-developed-by: Wedson Almeida Filho Signed-off-by: Wedson Almeida Filho Signed-off-by: Alice Ryhl --- rust/kernel/types.rs | 67 ++++++++++++++++++++++++++++++++++++++++++++ rust/kernel/uaccess.rs | 75 +++++++++++++++++++++++++++++++++++++++++++++++++- 2 files changed, 141 insertions(+), 1 deletion(-) diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs index fdb778e65d79..33d175a3a6ed 100644 --- a/rust/kernel/types.rs +++ b/rust/kernel/types.rs @@ -387,3 +387,70 @@ pub enum Either { /// Constructs an instance of [`Either`] containing a value of type `R`. Right(R), } + +/// Types for which any bit pattern is valid. +/// +/// Not all types are valid for all values. For example, a `bool` must be either +/// zero or one, so reading arbitrary bytes into something that contains a +/// `bool` is not okay. +/// +/// It's okay for the type to have padding, as initializing those bytes has no +/// effect. +/// +/// # Safety +/// +/// All bit-patterns must be valid for this type. +pub unsafe trait FromBytes {} + +// SAFETY: All bit patterns are acceptable values of the types below. +unsafe impl FromBytes for u8 {} +unsafe impl FromBytes for u16 {} +unsafe impl FromBytes for u32 {} +unsafe impl FromBytes for u64 {} +unsafe impl FromBytes for usize {} +unsafe impl FromBytes for i8 {} +unsafe impl FromBytes for i16 {} +unsafe impl FromBytes for i32 {} +unsafe impl FromBytes for i64 {} +unsafe impl FromBytes for isize {} +// SAFETY: If all bit patterns are acceptable for individual values in an array, +// then all bit patterns are also acceptable for arrays of that type. +unsafe impl FromBytes for [T] {} +unsafe impl FromBytes for [T; N] {} + +/// Types that can be viewed as an immutable slice of initialized bytes. +/// +/// If a struct implements this trait, then it is okay to copy it byte-for-byte +/// to userspace. This means that it should not have any padding, as padding +/// bytes are uninitialized. Reading uninitialized memory is not just undefined +/// behavior, it may even lead to leaking sensitive information on the stack to +/// userspace. +/// +/// The struct should also not hold kernel pointers, as kernel pointer addresses +/// are also considered sensitive. However, leaking kernel pointers is not +/// considered undefined behavior by Rust, so this is a correctness requirement, +/// but not a safety requirement. +/// +/// # Safety +/// +/// Values of this type may not contain any uninitialized bytes. +pub unsafe trait AsBytes {} + +// SAFETY: Instances of the following types have no uninitialized portions. +unsafe impl AsBytes for u8 {} +unsafe impl AsBytes for u16 {} +unsafe impl AsBytes for u32 {} +unsafe impl AsBytes for u64 {} +unsafe impl AsBytes for usize {} +unsafe impl AsBytes for i8 {} +unsafe impl AsBytes for i16 {} +unsafe impl AsBytes for i32 {} +unsafe impl AsBytes for i64 {} +unsafe impl AsBytes for isize {} +unsafe impl AsBytes for bool {} +unsafe impl AsBytes for char {} +unsafe impl AsBytes for str {} +// SAFETY: If individual values in an array have no uninitialized portions, then +// the the array itself does not have any uninitialized portions either. +unsafe impl AsBytes for [T] {} +unsafe impl AsBytes for [T; N] {} diff --git a/rust/kernel/uaccess.rs b/rust/kernel/uaccess.rs index f07821184bd6..71a00177a4b9 100644 --- a/rust/kernel/uaccess.rs +++ b/rust/kernel/uaccess.rs @@ -4,9 +4,15 @@ //! //! C header: [`include/linux/uaccess.h`](srctree/include/linux/uaccess.h) -use crate::{bindings, error::code::*, error::Result}; +use crate::{ + bindings, + error::code::*, + error::Result, + types::{AsBytes, FromBytes}, +}; use alloc::vec::Vec; use core::ffi::{c_ulong, c_void}; +use core::mem::{size_of, MaybeUninit}; /// A pointer to an area in userspace memory, which can be either read-only or /// read-write. @@ -237,6 +243,41 @@ pub unsafe fn read_raw(&mut self, out: *mut u8, len: usize) -> Result { Ok(()) } + /// Reads a value of the specified type. + /// + /// Fails with `EFAULT` if the read encounters a page fault. + pub fn read(&mut self) -> Result { + let len = size_of::(); + if len > self.length { + return Err(EFAULT); + } + let Ok(len_ulong) = c_ulong::try_from(len) else { + return Err(EFAULT); + }; + let mut out: MaybeUninit = MaybeUninit::uninit(); + // SAFETY: The local variable `out` is valid for writing `size_of::()` bytes. + // + // By using the _copy_from_user variant, we skip the check_object_size + // check that verifies the kernel pointer. This mirrors the logic on the + // C side that skips the check when the length is a compile-time + // constant. + let res = unsafe { + bindings::_copy_from_user(out.as_mut_ptr().cast::(), self.ptr, len_ulong) + }; + if res != 0 { + return Err(EFAULT); + } + // Since this is not a pointer to a valid object in our program, + // we cannot use `add`, which has C-style rules for defined + // behavior. + self.ptr = self.ptr.wrapping_byte_add(len); + self.length -= len; + // SAFETY: The read above has initialized all bytes in `out`, and since + // `T` implements `FromBytes`, any bit-pattern is a valid value for this + // type. + Ok(unsafe { out.assume_init() }) + } + /// Reads the entirety of the user slice, appending it to the end of the /// provided buffer. /// @@ -311,4 +352,36 @@ pub fn write_slice(&mut self, data: &[u8]) -> Result { // `len`, so the pointer is valid for reading `len` bytes. unsafe { self.write_raw(ptr, len) } } + + /// Writes the provided Rust value to this userspace pointer. + /// + /// Fails with `EFAULT` if the write encounters a page fault. + pub fn write(&mut self, value: &T) -> Result { + let len = size_of::(); + if len > self.length { + return Err(EFAULT); + } + let Ok(len_ulong) = c_ulong::try_from(len) else { + return Err(EFAULT); + }; + // SAFETY: The reference points to a value of type `T`, so it is valid + // for reading `size_of::()` bytes. + // + // By using the _copy_to_user variant, we skip the check_object_size + // check that verifies the kernel pointer. This mirrors the logic on the + // C side that skips the check when the length is a compile-time + // constant. + let res = unsafe { + bindings::_copy_to_user(self.ptr, (value as *const T).cast::(), len_ulong) + }; + if res != 0 { + return Err(EFAULT); + } + // Since this is not a pointer to a valid object in our program, + // we cannot use `add`, which has C-style rules for defined + // behavior. + self.ptr = self.ptr.wrapping_byte_add(len); + self.length -= len; + Ok(()) + } } From patchwork Thu Feb 8 15:47:54 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alice Ryhl X-Patchwork-Id: 198452 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a05:7300:50ea:b0:106:860b:bbdd with SMTP id r10csp262123dyd; Thu, 8 Feb 2024 07:53:24 -0800 (PST) X-Forwarded-Encrypted: i=3; AJvYcCV7z2lp8pQzEIlom3zTpRSJSg4e88cqLWBqEPRv3vtKbqkoO2JwpIn9G7oDF//ciyeuO/yiE8gUNW7zz7l8yr2065Xq3w== X-Google-Smtp-Source: AGHT+IECDPg9ii72u0au5M5cXx5jOHtMgRyEJmfPUUBwCCAx2QhTPZRVdnt0GbtY2DBaa8CEaUia X-Received: by 2002:a05:6a20:d494:b0:19e:9d92:9bde with SMTP id im20-20020a056a20d49400b0019e9d929bdemr8835839pzb.33.1707407604475; Thu, 08 Feb 2024 07:53:24 -0800 (PST) ARC-Seal: i=2; a=rsa-sha256; t=1707407604; cv=pass; d=google.com; s=arc-20160816; b=yqU2c7zGJKhqzrjPSmae1JraiJl6SMm2yWj53iBv4qgJ2NE1Pr5vlPYUDJ8zeWjypC SkX9TBZGV9g8Dj0nLa9+LXs54jKFCj9prZdIx+XIj7iMDXCntSjJc3l3Ym4BhZYIWSdE qXf8U+l4g7BviOgNuypPDl/FQGFk+pbfmtu2lyr39E9l4SOSIy9PKdP4tbNZODA1J36B BOxYH5mN/GQ5t7d0znZpc5t8rGAUhV8NtvbbNh25jIuw6+37yRSPd76p0dhjdWEUKV/0 uDeaB7uQxOJPwS0CHeO4n3Xi3RtmWrB0NULDq49C+xMR3CYdzEbVkihitvXIkD+LqFiB FMLQ== ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=cc:to:from:subject:message-id:references:mime-version :list-unsubscribe:list-subscribe:list-id:precedence:in-reply-to:date :dkim-signature; bh=GkurjLr2KJ06Z3QEBJTajcXp1Fe9o6FdUY3dEd+eNLc=; fh=3fCo1OjqJQWzIRLWXFGwc4/Vklnx4ie0P86Wf43EDa4=; b=JkJxd4xYGP0ClXs5eQcX6xR1aGyWSEKnNY+hM/VkVsxITMo9FZdxis8hBNQjJLMdic D+hSDGm7w2PJHO7JKb58k8g/WxT/19aYamR6WLDrDvMVvhqJacZ6KRB1RCKglNCnAGB1 gUnRWf63i2T0a0Dmyr0Vl2P6dIsGSYPoZHTXOhwlkVHXI/GFfmNaHPcml4M0CdyUICcU OC5qi0NVyUcJ5xqTMrGUi8+Is5a8+LOgXvm8zjV6brTVE9gAURJJ2Rjxd0jSWUZOZIxv 9l8FC3c+mzh/MDzyeYwGcpGde0Z4cft366XxcSURo57Vc/HGDskc3+lW3W0yXTSsrx3B 2ujg==; dara=google.com ARC-Authentication-Results: i=2; mx.google.com; dkim=pass header.i=@google.com header.s=20230601 header.b=AStFejWL; arc=pass (i=1 spf=pass spfdomain=flex--aliceryhl.bounces.google.com dkim=pass dkdomain=google.com dmarc=pass fromdomain=google.com); spf=pass (google.com: domain of linux-kernel+bounces-58304-ouuuleilei=gmail.com@vger.kernel.org designates 2604:1380:45e3:2400::1 as permitted sender) smtp.mailfrom="linux-kernel+bounces-58304-ouuuleilei=gmail.com@vger.kernel.org"; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com X-Forwarded-Encrypted: i=2; AJvYcCVNyVtdpQpERhynhW7pTo7TXjKDObUrB8L4YV7sTexySE9nkw5OS8eDrXNsJoF7MFm253gYr4gg1pm261K/mqHB5FL+0Q== Received: from sv.mirrors.kernel.org (sv.mirrors.kernel.org. [2604:1380:45e3:2400::1]) by mx.google.com with ESMTPS id fn2-20020a056a002fc200b006e0653afba5si4157849pfb.174.2024.02.08.07.53.24 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 Feb 2024 07:53:24 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel+bounces-58304-ouuuleilei=gmail.com@vger.kernel.org designates 2604:1380:45e3:2400::1 as permitted sender) client-ip=2604:1380:45e3:2400::1; Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20230601 header.b=AStFejWL; arc=pass (i=1 spf=pass spfdomain=flex--aliceryhl.bounces.google.com dkim=pass dkdomain=google.com dmarc=pass fromdomain=google.com); spf=pass (google.com: domain of linux-kernel+bounces-58304-ouuuleilei=gmail.com@vger.kernel.org designates 2604:1380:45e3:2400::1 as permitted sender) smtp.mailfrom="linux-kernel+bounces-58304-ouuuleilei=gmail.com@vger.kernel.org"; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com Received: from smtp.subspace.kernel.org (wormhole.subspace.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sv.mirrors.kernel.org (Postfix) with ESMTPS id A572E28C918 for ; Thu, 8 Feb 2024 15:49:58 +0000 (UTC) Received: from localhost.localdomain (localhost.localdomain [127.0.0.1]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 8843E80050; Thu, 8 Feb 2024 15:48:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="AStFejWL" Received: from mail-yw1-f201.google.com (mail-yw1-f201.google.com [209.85.128.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 52D567E785 for ; Thu, 8 Feb 2024 15:48:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707407334; cv=none; b=sS46yY7l/olQTMZwRglVLzStYQZcteKUOPpIwoILqFrk8cMePUjCPOxXw4Ll88uEBQMyRTp2uiyUXSFKELwWrN+YTTFpQP7B5xnl3FSLQkNN6i41XLAmbmFOTgEe/rQLtkFTumtYVBTtHtuKCMMJ7zwiX6SCNmhqm2kt16GD1Jk= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707407334; c=relaxed/simple; bh=5kbsE/b/eSnVbSFqPFnEYkacZIQs8b+yemi8lEykeZw=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=KyBkllgd3PtNJw2yFhIwYCvCqs1B49+l52FriuUOtElbcPd1mUC+hxJV7BU6QlwjkqAYjQojcBEW85pAtQ7ZMs1FvA8ThfGAAfqOjmlYt6uQGKCTp1R7UGaxYWlczsvpqNGd1Dow6weorwUTVSqf7HhKd2m4cmFqaEzeIcbLgC0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--aliceryhl.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=AStFejWL; arc=none smtp.client-ip=209.85.128.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--aliceryhl.bounces.google.com Received: by mail-yw1-f201.google.com with SMTP id 00721157ae682-604186a5775so11297107b3.1 for ; Thu, 08 Feb 2024 07:48:52 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1707407331; x=1708012131; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=GkurjLr2KJ06Z3QEBJTajcXp1Fe9o6FdUY3dEd+eNLc=; b=AStFejWLzvEXTdeiBhDnZtIhwDlzknZVEJJGyGyZGPB6NzhlyJC856QTOZixH2Y1Fg 8HeWd54u5agJzvKUE3cQJfcOv6kGwMxibT/2M0ThGQE0Ykb/E0sih1IKVL4BaGhx+mtM B1fKCjhL0ig7S4R+cfroy1qT/yrAkHctiDXo3rNdPdUvHRaVJrreV7z9ezQBB2fKoorl yPNRCef5cTmOwxY2XEIPYd0eZ8XNTbSuU/cz2ql3hAyxiK8mXkDlR+4RcnM/yaMRK6xi D3FJYapVsvTGDeiStwG226TZHUEMlzkakPxP2aNT5RTw9uzFbnqTHGxrAZzvpVXaDesL EMZg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1707407331; x=1708012131; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=GkurjLr2KJ06Z3QEBJTajcXp1Fe9o6FdUY3dEd+eNLc=; b=euFjBMqAYqLZYOvzEsV0amS6RmQZ9e5AaDMeVjLNw+RZo+WhQDejUnsXShQUw8hcCd maEs7KdI+G4HhF7LV0GfbofHCfGq2vIsqc0po9gkW5fPRVXOxQNplJY0l7CSxkrwl51p 9AMv7yoysel7yYXTqmMkcuji6KxUJtPnOSl6C2WBU7PnXcKbyV+J2C1nMRkX0gNDyS+G NTPoLY3G4cSosqV/ugInqgV6rhNN2DgXjvW6fmV3HHOxGtsCwD78pF1uAse4PNlh0iwS MijYswyp7QXD3LY0I5m6R3xp6PkOw7OYury5g5LbTw8vT+NUl2GezuUu3hAGAf15T+JS Gdpw== X-Forwarded-Encrypted: i=1; AJvYcCXX6EJJqvrOfTWdR+i3dc6GcGL5kEc0NykKYuXYj6UYk5Z03Svf6eLZs6JbIREedvVfOskJz4slsJW+TPp++oCnyo5CH/soKDIqkUU5 X-Gm-Message-State: AOJu0YzUQ4ovaPQrXjZJIQ80NhtmhVV8hvAvX8+zqXrwJ1KlwpSmgrs5 pxAe/GVfGd42vX1jIuJuNsW9phQj06KrWbm/GJuKjI4tQRXjsNOulRBSvpXNCZa/Eq66MChIPSt GtDzjtq34raVCwg== X-Received: from aliceryhl2.c.googlers.com ([fda3:e722:ac3:cc00:68:949d:c0a8:572]) (user=aliceryhl job=sendgmr) by 2002:a05:6902:100b:b0:dc6:e884:2342 with SMTP id w11-20020a056902100b00b00dc6e8842342mr764942ybt.5.1707407331450; Thu, 08 Feb 2024 07:48:51 -0800 (PST) Date: Thu, 08 Feb 2024 15:47:54 +0000 In-Reply-To: <20240208-alice-mm-v2-0-d821250204a6@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240208-alice-mm-v2-0-d821250204a6@google.com> X-Developer-Key: i=aliceryhl@google.com; a=openpgp; fpr=49F6C1FAA74960F43A5B86A1EE7A392FDE96209F X-Developer-Signature: v=1; a=openpgp-sha256; l=12755; i=aliceryhl@google.com; h=from:subject:message-id; bh=5kbsE/b/eSnVbSFqPFnEYkacZIQs8b+yemi8lEykeZw=; b=owEBbQKS/ZANAwAKAQRYvu5YxjlGAcsmYgBlxPfU67tCAf96rUhr77wodzJbxjoBZvA+pKp54 TdgXCe6UwyJAjMEAAEKAB0WIQSDkqKUTWQHCvFIvbIEWL7uWMY5RgUCZcT31AAKCRAEWL7uWMY5 RgZ3EACMa2s3PKNHIdyO26oX3t0dPYuDrEmv0G8WCEpnJsXaaYMUb7IEmcf8cM74d1xUs/tQWRI GDHB+GiwnDcEIkB+itkR2/WdykfPSUwtijCjJ7IVuaeYKTXe5y4S4bzUslEOUwxJGScFo+CpHBM XcLgq9ilImTzGR29npE+iqbTwErklrUA9JOn7yvI2l7Qq8zJ5wZ+8NGwHKYLfegy5lIvsajIqnL J1claGaD8NF+HlnSg+/Vw6rIndTyvNaOnI5eVGgPgOfpzi3tmer0/gopsjWSpLYksDsrwM5DgOd KZFb6ob+vBpSlbr0Wg5NEl9s+TLBj8mJlgAt5wFUg08GbKIy+oFsvAZwNGSuglAHu7FEN22u2uv ZWsSLCee6/Zvh8jHTh6KZHJLsCajnYSnc5BRW/iSkuH7dp5hF8ooBca9PoZVFW4Lnvy9DX++95h IH4z1nWm/dIqVGhZf3semETumlANLlHPnp/Eos2URF0jnhtI6ct4VH3kCZ82FeH9Ia320wfSKd5 kNxx0BMOURevsseZTCpziAeiiSYh19gQFlT/JvkDsVR/mTzIEegLfpMdYvfipw+DuCseg86j3bM cBhoKYkgeqatoOGFECGxHZcXOKZDrefX5jylDTCJd844FstI3U8aCbLGToKO03HpbkiuSCTMROc qU/XnZ0uYKaEJng== X-Mailer: b4 0.13-dev-26615 Message-ID: <20240208-alice-mm-v2-4-d821250204a6@google.com> Subject: [PATCH v2 4/4] rust: add abstraction for `struct page` From: Alice Ryhl To: Miguel Ojeda , Alex Gaynor , Wedson Almeida Filho , Boqun Feng , Gary Guo , " =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= " , Benno Lossin , Andreas Hindborg , Kees Cook , Al Viro , Andrew Morton Cc: Greg Kroah-Hartman , " =?utf-8?q?Arve_Hj?= =?utf-8?q?=C3=B8nnev=C3=A5g?= " , Todd Kjos , Martijn Coenen , Joel Fernandes , Carlos Llamas , Suren Baghdasaryan , Arnd Bergmann , linux-mm@kvack.org, linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, Alice Ryhl , Christian Brauner X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1790346636071127593 X-GMAIL-MSGID: 1790346636071127593 Adds a new struct called `Page` that wraps a pointer to `struct page`. This struct is assumed to hold ownership over the page, so that Rust code can allocate and manage pages directly. The page type has various methods for reading and writing into the page. These methods will temporarily map the page to allow the operation. All of these methods use a helper that takes an offset and length, performs bounds checks, and returns a pointer to the given offset in the page. This patch only adds support for pages of order zero, as that is all Rust Binder needs. However, it is written to make it easy to add support for higher-order pages in the future. To do that, you would add a const generic parameter to `Page` that specifies the order. Most of the methods do not need to be adjusted, as the logic for dealing with mapping multiple pages at once can be isolated to just the `with_pointer_into_page` method. Finally, the struct can be renamed to `Pages`, and the type alias `Page = Pages<0>` can be introduced. Rust Binder needs to manage pages directly as that is how transactions are delivered: Each process has an mmap'd region for incoming transactions. When an incoming transaction arrives, the Binder driver will choose a region in the mmap, allocate and map the relevant pages manually, and copy the incoming transaction directly into the page. This architecture allows the driver to copy transactions directly from the address space of one process to another, without an intermediate copy to a kernel buffer. This code is based on Wedson's page abstractions from the old rust branch, but it has been modified by Alice by removing the incomplete support for higher-order pages, and by introducing the `with_*` helpers to consolidate the bounds checking logic into a single place. Co-developed-by: Wedson Almeida Filho Signed-off-by: Wedson Almeida Filho Signed-off-by: Alice Ryhl --- rust/bindings/bindings_helper.h | 1 + rust/helpers.c | 20 ++++ rust/kernel/lib.rs | 1 + rust/kernel/page.rs | 209 ++++++++++++++++++++++++++++++++++++++++ 4 files changed, 231 insertions(+) diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h index 936651110c39..b5b7fa7bd456 100644 --- a/rust/bindings/bindings_helper.h +++ b/rust/bindings/bindings_helper.h @@ -22,3 +22,4 @@ const size_t RUST_CONST_HELPER_ARCH_SLAB_MINALIGN = ARCH_SLAB_MINALIGN; const gfp_t RUST_CONST_HELPER_GFP_KERNEL = GFP_KERNEL; const gfp_t RUST_CONST_HELPER___GFP_ZERO = __GFP_ZERO; +const gfp_t RUST_CONST_HELPER___GFP_HIGHMEM = ___GFP_HIGHMEM; diff --git a/rust/helpers.c b/rust/helpers.c index 312b6fcb49d5..298d2ee16e61 100644 --- a/rust/helpers.c +++ b/rust/helpers.c @@ -25,6 +25,8 @@ #include #include #include +#include +#include #include #include #include @@ -93,6 +95,24 @@ int rust_helper_signal_pending(struct task_struct *t) } EXPORT_SYMBOL_GPL(rust_helper_signal_pending); +struct page *rust_helper_alloc_pages(gfp_t gfp_mask, unsigned int order) +{ + return alloc_pages(gfp_mask, order); +} +EXPORT_SYMBOL_GPL(rust_helper_alloc_pages); + +void *rust_helper_kmap_local_page(struct page *page) +{ + return kmap_local_page(page); +} +EXPORT_SYMBOL_GPL(rust_helper_kmap_local_page); + +void rust_helper_kunmap_local(const void *addr) +{ + kunmap_local(addr); +} +EXPORT_SYMBOL_GPL(rust_helper_kunmap_local); + refcount_t rust_helper_REFCOUNT_INIT(int n) { return (refcount_t)REFCOUNT_INIT(n); diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs index 5a03aafcbb69..59ee6dd6f7c6 100644 --- a/rust/kernel/lib.rs +++ b/rust/kernel/lib.rs @@ -40,6 +40,7 @@ pub mod kunit; #[cfg(CONFIG_NET)] pub mod net; +pub mod page; pub mod prelude; pub mod print; mod static_assert; diff --git a/rust/kernel/page.rs b/rust/kernel/page.rs new file mode 100644 index 000000000000..ac253744f94b --- /dev/null +++ b/rust/kernel/page.rs @@ -0,0 +1,209 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! Kernel page allocation and management. + +use crate::{bindings, error::code::*, error::Result, uaccess::UserSliceReader}; +use core::{ + alloc::AllocError, + ptr::{self, NonNull}, +}; + +/// A bitwise shift for the page size. +pub const PAGE_SHIFT: usize = bindings::PAGE_SHIFT as usize; +/// The number of bytes in a page. +pub const PAGE_SIZE: usize = 1 << PAGE_SHIFT; + +/// A pointer to a page that owns the page allocation. +/// +/// # Invariants +/// +/// The pointer points at a page, and has ownership over the page. +pub struct Page { + page: NonNull, +} + +// SAFETY: It is safe to transfer page allocations between threads. +unsafe impl Send for Page {} + +// SAFETY: As long as the safety requirements for `&self` methods on this type +// are followed, there is no problem with calling them in parallel. +unsafe impl Sync for Page {} + +impl Page { + /// Allocates a new page. + pub fn new() -> Result { + // SAFETY: These are the correct arguments to allocate a single page. + let page = unsafe { + bindings::alloc_pages( + bindings::GFP_KERNEL | bindings::__GFP_ZERO | bindings::__GFP_HIGHMEM, + 0, + ) + }; + + let page = NonNull::new(page).ok_or(AllocError)?; + // INVARIANT: We checked that the allocation succeeded. + Ok(Self { page }) + } + + /// Returns a raw pointer to the page. + pub fn as_ptr(&self) -> *mut bindings::page { + self.page.as_ptr() + } + + /// Runs a piece of code with this page mapped to an address. + /// + /// The page is unmapped when this call returns. + /// + /// It is up to the caller to use the provided raw pointer correctly. + pub fn with_page_mapped(&self, f: impl FnOnce(*mut u8) -> T) -> T { + // SAFETY: `page` is valid due to the type invariants on `Page`. + let mapped_addr = unsafe { bindings::kmap_local_page(self.as_ptr()) }; + + let res = f(mapped_addr.cast()); + + // SAFETY: This unmaps the page mapped above. + // + // Since this API takes the user code as a closure, it can only be used + // in a manner where the pages are unmapped in reverse order. This is as + // required by `kunmap_local`. + // + // In other words, if this call to `kunmap_local` happens when a + // different page should be unmapped first, then there must necessarily + // be a call to `kmap_local_page` other than the call just above in + // `with_page_mapped` that made that possible. In this case, it is the + // unsafe block that wraps that other call that is incorrect. + unsafe { bindings::kunmap_local(mapped_addr) }; + + res + } + + /// Runs a piece of code with a raw pointer to a slice of this page, with + /// bounds checking. + /// + /// If `f` is called, then it will be called with a pointer that points at + /// `off` bytes into the page, and the pointer will be valid for at least + /// `len` bytes. The pointer is only valid on this task, as this method uses + /// a local mapping. + /// + /// If `off` and `len` refers to a region outside of this page, then this + /// method returns `EINVAL` and does not call `f`. + /// + /// It is up to the caller to use the provided raw pointer correctly. + pub fn with_pointer_into_page( + &self, + off: usize, + len: usize, + f: impl FnOnce(*mut u8) -> Result, + ) -> Result { + let bounds_ok = off <= PAGE_SIZE && len <= PAGE_SIZE && (off + len) <= PAGE_SIZE; + + if bounds_ok { + self.with_page_mapped(move |page_addr| { + // SAFETY: The `off` integer is at most `PAGE_SIZE`, so this pointer offset will + // result in a pointer that is in bounds or one off the end of the page. + f(unsafe { page_addr.add(off) }) + }) + } else { + Err(EINVAL) + } + } + + /// Maps the page and reads from it into the given buffer. + /// + /// This method will perform bounds checks on the page offset. If `offset .. + /// offset+len` goes outside ot the page, then this call returns `EINVAL`. + /// + /// # Safety + /// + /// * Callers must ensure that `dst` is valid for writing `len` bytes. + /// * Callers must ensure that this call does not race with a write to the + /// same page that overlaps with this read. + pub unsafe fn read_raw(&self, dst: *mut u8, offset: usize, len: usize) -> Result { + self.with_pointer_into_page(offset, len, move |src| { + // SAFETY: If `with_pointer_into_page` calls into this closure, then + // it has performed a bounds check and guarantees that `src` is + // valid for `len` bytes. + // + // There caller guarantees that there is no data race. + unsafe { ptr::copy(src, dst, len) }; + Ok(()) + }) + } + + /// Maps the page and writes into it from the given buffer. + /// + /// This method will perform bounds checks on the page offset. If `offset .. + /// offset+len` goes outside ot the page, then this call returns `EINVAL`. + /// + /// # Safety + /// + /// * Callers must ensure that `src` is valid for reading `len` bytes. + /// * Callers must ensure that this call does not race with a read or write + /// to the same page that overlaps with this write. + pub unsafe fn write_raw(&self, src: *const u8, offset: usize, len: usize) -> Result { + self.with_pointer_into_page(offset, len, move |dst| { + // SAFETY: If `with_pointer_into_page` calls into this closure, then + // it has performed a bounds check and guarantees that `dst` is + // valid for `len` bytes. + // + // There caller guarantees that there is no data race. + unsafe { ptr::copy(src, dst, len) }; + Ok(()) + }) + } + + /// Maps the page and zeroes the given slice. + /// + /// This method will perform bounds checks on the page offset. If `offset .. + /// offset+len` goes outside ot the page, then this call returns `EINVAL`. + /// + /// # Safety + /// + /// Callers must ensure that this call does not race with a read or write to + /// the same page that overlaps with this write. + pub unsafe fn fill_zero(&self, offset: usize, len: usize) -> Result { + self.with_pointer_into_page(offset, len, move |dst| { + // SAFETY: If `with_pointer_into_page` calls into this closure, then + // it has performed a bounds check and guarantees that `dst` is + // valid for `len` bytes. + // + // There caller guarantees that there is no data race. + unsafe { ptr::write_bytes(dst, 0u8, len) }; + Ok(()) + }) + } + + /// Copies data from userspace into this page. + /// + /// This method will perform bounds checks on the page offset. If `offset .. + /// offset+len` goes outside ot the page, then this call returns `EINVAL`. + /// + /// # Safety + /// + /// Callers must ensure that this call does not race with a read or write to + /// the same page that overlaps with this write. + pub unsafe fn copy_from_user_slice( + &self, + reader: &mut UserSliceReader, + offset: usize, + len: usize, + ) -> Result { + self.with_pointer_into_page(offset, len, move |dst| { + // SAFETY: If `with_pointer_into_page` calls into this closure, then + // it has performed a bounds check and guarantees that `dst` is + // valid for `len` bytes. + // + // There caller guarantees that there is no data race when writing + // to `dst`. + unsafe { reader.read_raw(dst, len) } + }) + } +} + +impl Drop for Page { + fn drop(&mut self) { + // SAFETY: By the type invariants, we have ownership of the page and can + // free it. + unsafe { bindings::__free_pages(self.page.as_ptr(), 0) }; + } +}