From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 98EE223F28E; Fri, 7 Feb 2025 14:43:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738939420; cv=none; b=ogKMWDFdEVxyEtrRLnqgIE1vUx5vpkRmJ6F1txYCw2OW24aTdrwqv9sZVcbx56cVM8yIIXN1R8EsoTK7UnThdcdVpgtU1jg8UgaSKBwvchzFgrM43HDxA14YBp8I+R4Zt5b90IoUnw3GeHkt6TdztUSxm6Tj5ZiIy7G4BZYvhws= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738939420; c=relaxed/simple; bh=k3wpUbLNpdlWKM9UcjYKW3ziZOJZGGVZbH5SP5iFKC0=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=ACBHlqcN2idL/LuzbBf4qLnTDMw7fGyT4ntmt+oZx/oihoGwJqAxobP7t1b1lAllPL8EEGxYuU9Nix6pTaRBxvNC379CyuIuL6OsB3uiS+nUWzgrnyd6HJTcxKbLCDE6eFAyVlM8o2+7QEBO3y466oj0yRNroE3NaxIVq9BVOC0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=UamO57gm; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="UamO57gm" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8EC8CC4CEE2; Fri, 7 Feb 2025 14:43:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1738939420; bh=k3wpUbLNpdlWKM9UcjYKW3ziZOJZGGVZbH5SP5iFKC0=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=UamO57gmZKt5lpEEbCRh2YMqWXUEZDp3mIcF/0zUGNCevtZn6hfzhOe7cm6Phjt1z v8g+YZZ29jpdjkPjE+XKwLUZ4Etire9F7IK7B4YHNFBr2a6/JTozQPbuWYor2AOL/e rO/eCY+beX9mphExEKh2X0K5s571D+Rv2RggXFStiEx5Y0coH1GGIAb/rMi/xxqC+M BEo4PVL+vZ0jzxZrzB64G/H2/AAUvAv/jPPKbPziCGCSHiy6evOVKA5xTA8mCZnxVU xlWKT66MK6elH9tbA0rqJwttdU0JRDEsDdaHt9hjP5jOyndgSinbWujKDWZ8Z/801s eDd5DVxl5HYSQ== From: Andreas Hindborg Date: Fri, 07 Feb 2025 15:41:21 +0100 Subject: [PATCH v2 2/3] rust: configfs: introduce rust support for configfs Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20250207-configfs-v2-2-f7a60b24d38e@kernel.org> References: <20250207-configfs-v2-0-f7a60b24d38e@kernel.org> In-Reply-To: <20250207-configfs-v2-0-f7a60b24d38e@kernel.org> To: Danilo Krummrich , Miguel Ojeda , Alex Gaynor , Boqun Feng , Gary Guo , =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= , Benno Lossin , Alice Ryhl , Trevor Gross , Joel Becker , Christoph Hellwig , Peter Zijlstra , Ingo Molnar , Will Deacon , Waiman Long , Fiona Behrens , Charalampos Mitrodimas Cc: rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, Andreas Hindborg X-Mailer: b4 0.15-dev X-Developer-Signature: v=1; a=openpgp-sha256; l=41101; i=a.hindborg@kernel.org; h=from:subject:message-id; bh=k3wpUbLNpdlWKM9UcjYKW3ziZOJZGGVZbH5SP5iFKC0=; b=owEBbQKS/ZANAwAIAeG4Gj55KGN3AcsmYgBnphvFQsk0gm58R75s6RcMLe+f/cdgYaJasL1bk 95zA9sRgECJAjMEAAEIAB0WIQQSwflHVr98KhXWwBLhuBo+eShjdwUCZ6YbxQAKCRDhuBo+eShj d9VOD/98Uy3oRO3Htwf3dECy2UZliYD/kyz+h2OkLU28LMk7NTVT9Hi07MfYNbBlzpU7xmpkKD9 /JWsbMpYXTNpWm1J1Gm/BzjpWMVAcbktGvSepP2hGyLD4dF0TCDvPP/FOkHL7MfkiRvS8qqgbNs qWbQ4gucJrotAFyI+M1O6PZ27RsAI7PZWhUqba3qmRri6IG+BbhGH4pMDX/6PCSbU+dUFBOTxVJ tkKH2rBqrW6wG6iMczoAL2MRD4uwdzN/1oleZ9ch2mW8zBBSi+coUxMd85uviVqZFSNh0nhxDTd aWReP7EXhQs7cuuaS1SMAiSDGVtt635VmpghS+j1CMHBCr4jXZwf2Fu2oIVFZJo05sPfbpXgKpY AjdlNfZfRyjcRLgtSWGJriIMWIysTRAlioTy+lEe9p4ZhwWmv98Em3Ta0Z4DpmcO2oEp0SaOmlL K6JcUAMqzaZr7VqA/iHoy50YasQHq7qxtIaJcIiFF3+8FKGxA7aNhF/HEoEGuAuKSGkiXPXfte7 4Y6rzMbhmilINoCFwOzKXFCgqHYZCKD/LvyNzQdHLapBgozF2Sy2CTJWUK2xLFCg1MaigedXvxZ 2cFukgdFm5sxgocbWULEOgnZloSXswPF4ETqKtETYefJpbluA65WOzbG9Qr1Q/Hx0KjIUDXenow XGI8BgpsKUNXWUw== X-Developer-Key: i=a.hindborg@kernel.org; a=openpgp; fpr=3108C10F46872E248D1FB221376EB100563EF7A7 This patch adds a rust API for configfs, thus allowing rust modules to use configfs for configuration. The implementation is a shim on top of the C configfs implementation allowing safe use of the C infrastructure from rust. The patch enables the `const_mut_refs` feature on compilers before rustc 1.83. The feature was stabilized in rustc 1.83 and is not required to be explicitly enabled on later versions. Signed-off-by: Andreas Hindborg --- This patch is a direct dependency for `rnull`, the rust null block driver. --- rust/bindings/bindings_helper.h | 1 + rust/helpers/mutex.c | 5 + rust/kernel/configfs.rs | 860 ++++++++++++++++++++++++++++++++++++++++ rust/kernel/lib.rs | 2 + samples/rust/Kconfig | 11 + samples/rust/Makefile | 1 + samples/rust/rust_configfs.rs | 186 +++++++++ 7 files changed, 1066 insertions(+) diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h index 55354e4dec14e..d115a770306f6 100644 --- a/rust/bindings/bindings_helper.h +++ b/rust/bindings/bindings_helper.h @@ -10,6 +10,7 @@ #include #include #include +#include #include #include #include diff --git a/rust/helpers/mutex.c b/rust/helpers/mutex.c index 06575553eda5c..3e9b910a88e9b 100644 --- a/rust/helpers/mutex.c +++ b/rust/helpers/mutex.c @@ -17,3 +17,8 @@ void rust_helper_mutex_assert_is_held(struct mutex *mutex) { lockdep_assert_held(mutex); } + +void rust_helper_mutex_destroy(struct mutex *lock) +{ + mutex_destroy(lock); +} diff --git a/rust/kernel/configfs.rs b/rust/kernel/configfs.rs new file mode 100644 index 0000000000000..9d4b381b9df89 --- /dev/null +++ b/rust/kernel/configfs.rs @@ -0,0 +1,860 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! `configfs` interface. +//! +//! `configfs` is an in-memory pseudo file system for configuration of kernel +//! modules. Please see the [C documentation] for details and intended use of +//! `configfs`. +//! +//! This module does not support the following `configfs` features: +//! +//! - Items. All group children are groups. +//! - Symlink support. +//! - `disconnect_notify` hook. +//! - Default groups. +//! +//! See the [rust_configfs.rs] sample for a full example use of this module. +//! +//! C header: [`include/linux/configfs.h`](srctree/include/linux/configfs.h) +//! +//! [C documentation]: srctree/Documentation/filesystems/configfs.rst +//! [rust_configfs.rs]: srctree/samples/rust/rust_configfs.rs + +use crate::alloc::flags; +use crate::container_of; +use crate::page::PAGE_SIZE; +use crate::prelude::*; +use crate::str::CString; +use crate::sync::Arc; +use crate::types::ForeignOwnable; +use crate::types::Opaque; +use core::cell::UnsafeCell; +use core::marker::PhantomData; +use core::ptr::addr_of; +use core::ptr::addr_of_mut; + +/// A `configfs` subsystem. +/// +/// This is the top level entrypoint for a `configfs` hierarchy. To register +/// with configfs, embed a field of this type into your kernel module struct. +#[pin_data(PinnedDrop)] +pub struct Subsystem { + #[pin] + subsystem: Opaque, + #[pin] + data: Data, +} + +// SAFETY: We do not provide any operations on `Subsystem`. +unsafe impl Sync for Subsystem {} + +// SAFETY: Ownership of `Subsystem` can safely be transferred to other threads. +unsafe impl Send for Subsystem {} + +impl Subsystem { + /// Create an initializer for a [`Subsystem`]. + /// + /// The subsystem will appear in configfs as a directory name given by + /// `name`. The attributes available in directory are specified by + /// `item_type`. + pub fn new( + name: &'static CStr, + item_type: &'static ItemType, Data>, + data: impl PinInit, + ) -> impl PinInit { + try_pin_init!(Self { + subsystem <- kernel::init::zeroed().chain( + |place: &mut Opaque| { + // SAFETY: All of `place` is valid for write. + unsafe { + addr_of_mut!((*place.get()).su_group.cg_item.ci_name ) + .write(name.as_ptr().cast_mut().cast()) + }; + // SAFETY: All of `place` is valid for write. + unsafe { + addr_of_mut!((*place.get()).su_group.cg_item.ci_type) + .write(item_type.as_ptr()) + }; + // SAFETY: We initialized the required fields of `place.group` above. + unsafe { bindings::config_group_init(&mut (*place.get()).su_group) }; + // SAFETY: `place.su_mutex` is valid for use as a mutex. + unsafe { bindings::__mutex_init( + &mut (*place.get()).su_mutex, + kernel::optional_name!().as_char_ptr(), + kernel::static_lock_class!().as_ptr()) + } + Ok(()) + }), + data <- data, + }) + .pin_chain(|this| { + crate::error::to_result( + // SAFETY: We initialized `this.subsystem` according to C API contract above. + unsafe { bindings::configfs_register_subsystem(this.subsystem.get()) }, + ) + }) + } +} + +#[pinned_drop] +impl PinnedDrop for Subsystem { + fn drop(self: Pin<&mut Self>) { + // SAFETY: We registered `self.subsystem` in the initializer returned by `Self::new`. + unsafe { bindings::configfs_unregister_subsystem(self.subsystem.get()) }; + // SAFETY: We initialized the mutex in `Subsystem::new`. + unsafe { bindings::mutex_destroy(addr_of_mut!((*self.subsystem.get()).su_mutex)) }; + } +} + +/// Trait that allows offset calculations for structs that embed a +/// `bindings::config_group`. +/// +/// Users of the `configfs` API should not need to implement this trait. +/// +/// # Safety +/// +/// - Implementers of this trait must embed a `bindings::config_group`. +/// - Methods must be implemented according to method documentation. +pub unsafe trait HasGroup { + /// Return the address of the `bindings::config_group` embedded in `Self`. + /// + /// # Safety + /// + /// - `this` must be a valid allocation of at least the size of `Self`. + unsafe fn group(this: *const Self) -> *const bindings::config_group; + + /// Return the address of the `Self` that `group` is embedded in. + /// + /// # Safety + /// + /// - `group` must point to the `bindings::config_group` that is embedded in + /// `Self`. + unsafe fn container_of(group: *const bindings::config_group) -> *const Self; +} + +// SAFETY: `Subsystem` embeds a field of type `bindings::config_group` +// within the `subsystem` field. +unsafe impl HasGroup for Subsystem { + unsafe fn group(this: *const Self) -> *const bindings::config_group { + // SAFETY: By impl and function safety requirement this projection is in bounds. + unsafe { addr_of!((*(*this).subsystem.get()).su_group) } + } + + unsafe fn container_of(group: *const bindings::config_group) -> *const Self { + // SAFETY: By impl and function safety requirement this projection is in bounds. + let c_subsys_ptr = unsafe { container_of!(group, bindings::configfs_subsystem, su_group) }; + let opaque_ptr = c_subsys_ptr.cast::>(); + // SAFETY: By impl and function safety requirement, `opaque_ptr` and the + // pointer it returns, are within the same allocation. + unsafe { container_of!(opaque_ptr, Subsystem, subsystem) } + } +} + +/// A `configfs` group. +/// +/// To add a subgroup to `configfs`, pass this type as `ctype` to +/// [`crate::configfs_attrs`] when creating a group in [`GroupOperations::make_group`]. +#[pin_data] +pub struct Group { + #[pin] + group: Opaque, + #[pin] + data: Data, +} + +impl Group { + /// Create an initializer for a new group. + /// + /// When instantiated, the group will appear as a directory with the name + /// given by `name` and it will contain attributes specified by `item_type`. + pub fn new( + name: CString, + item_type: &'static ItemType, Data>, + data: impl PinInit, + ) -> impl PinInit { + try_pin_init!(Self { + group <- kernel::init::zeroed().chain(|v: &mut Opaque| { + let place = v.get(); + let name = name.as_bytes_with_nul().as_ptr(); + // SAFETY: It is safe to initialize a group once it has been zeroed. + unsafe { + bindings::config_group_init_type_name(place, name as _, item_type.as_ptr()) + }; + Ok(()) + }), + data <- data, + }) + } +} + +// SAFETY: `Group` embeds a field of type `bindings::config_group` +// within the `group` field. +unsafe impl HasGroup for Group { + unsafe fn group(this: *const Self) -> *const bindings::config_group { + Opaque::raw_get( + // SAFETY: By impl and function safety requirements this field + // projection is within bounds of the allocation. + unsafe { addr_of!((*this).group) }, + ) + } + + unsafe fn container_of(group: *const bindings::config_group) -> *const Self { + let opaque_ptr = group.cast::>(); + // SAFETY: By impl and function safety requirement, `opaque_ptr` and + // pointer it returns will be in the same allocation. + unsafe { container_of!(opaque_ptr, Self, group) } + } +} + +/// # Safety +/// +/// `this` must be a valid pointer. +/// +/// If `this` does not represent the root group of a `configfs` subsystem, +/// `this` must be a pointer to a `bindings::config_group` embedded in a +/// `Group`. +/// +/// Otherwise, `this` must be a pointer to a `bindings::config_group` that +/// is embedded in a `bindings::configfs_subsystem` that is embedded in a +/// `Subsystem`. +unsafe fn get_group_data<'a, Parent>(this: *mut bindings::config_group) -> &'a Parent { + // TODO + // SAFETY: `this` is a valid pointer. + let is_root = unsafe { (*this).cg_subsys.is_null() }; + + if !is_root { + // SAFETY: By C API contact, `this` is a pointer to a + // `bindings::config_group` that we passed as a return value in from + // `make_group`. Such a pointer is embedded within a `Group`. + unsafe { &(*Group::::container_of(this)).data } + } else { + // SAFETY: By C API contract, `this` is a pointer to the + // `bindings::config_group` field within a `Subsystem`. + unsafe { &(*Subsystem::container_of(this)).data } + } +} + +struct GroupOperationsVTable(PhantomData<(Parent, Child)>) +where + Parent: GroupOperations; + +impl GroupOperationsVTable +where + Parent: GroupOperations, + Child: 'static, +{ + /// # Safety + /// + /// `this` must be a valid pointer. + /// + /// If `this` does not represent the root group of a `configfs` subsystem, + /// `this` must be a pointer to a `bindings::config_group` embedded in a + /// `Group`. + /// + /// Otherwise, `this` must be a pointer to a `bindings::config_group` that + /// is embedded in a `bindings::configfs_subsystem` that is embedded in a + /// `Subsystem`. + /// + /// `name` must point to a null terminated string. + unsafe extern "C" fn make_group( + this: *mut bindings::config_group, + name: *const kernel::ffi::c_char, + ) -> *mut bindings::config_group { + // SAFETY: By function safety requirements of this function, this call + // is safe. + let parent_data = unsafe { get_group_data(this) }; + + let group_init = match Parent::make_group( + parent_data, + // SAFETY: By function safety requirements, name points to a null + // terminated string. + unsafe { CStr::from_char_ptr(name) }, + ) { + Ok(init) => init, + Err(e) => return e.to_ptr(), + }; + + let child_group = > as InPlaceInit>>::try_pin_init( + group_init, + flags::GFP_KERNEL, + ); + + match child_group { + Ok(child_group) => { + let child_group_ptr = child_group.into_foreign(); + // SAFETY: We allocated the pointee of `child_ptr` above as a + // `Group`. + unsafe { Group::::group(child_group_ptr) }.cast_mut() + } + Err(e) => e.to_ptr(), + } + } + + /// # Safety + /// + /// If `this` does not represent the root group of a `configfs` subsystem, + /// `this` must be a pointer to a `bindings::config_group` embedded in a + /// `Group`. + /// + /// Otherwise, `this` must be a pointer to a `bindings::config_group` that + /// is embedded in a `bindings::configfs_subsystem` that is embedded in a + /// `Subsystem`. + /// + /// `item` must point to a `bindings::config_item` within a + /// `bindings::config_group` within a `Group`. + unsafe extern "C" fn drop_item( + this: *mut bindings::config_group, + item: *mut bindings::config_item, + ) { + // SAFETY: By function safety requirements of this function, this call + // is safe. + let parent_data = unsafe { get_group_data(this) }; + + // SAFETY: By function safety requirements, `item` is embedded in a + // `config_group`. + let c_child_group_ptr = + unsafe { kernel::container_of!(item, bindings::config_group, cg_item) }; + // SAFETY: By function safety requirements, `c_child_group_ptr` is + // embedded within a `Group`. + let r_child_group_ptr = unsafe { Group::::container_of(c_child_group_ptr) }; + + if Parent::HAS_DROP_ITEM { + Parent::drop_item( + parent_data, + // SAFETY: We called `into_foreign` to produce `r_child_group_ptr` in + // `make_group`. There are not other borrows of this pointer in existence. + unsafe { + > as ForeignOwnable>::borrow(r_child_group_ptr.cast_mut()) + }, + ); + } + + // SAFETY: By C API contract, we are required to drop a refcount on + // `item`. + unsafe { bindings::config_item_put(item) }; + } + + const VTABLE: bindings::configfs_group_operations = bindings::configfs_group_operations { + make_item: None, + make_group: Some(Self::make_group), + disconnect_notify: None, + drop_item: Some(Self::drop_item), + is_visible: None, + is_bin_visible: None, + }; +} + +struct ItemOperationsVTable(PhantomData<(Container, Data)>); + +impl ItemOperationsVTable, Data> +where + Data: 'static, +{ + /// # Safety + /// + /// `this` must be a pointer to a `bindings::config_group` embedded in a + /// `Group`. + /// + /// This function will destroy the pointee of `this`. The pointee of `this` + /// must not be accessed after the function returns. + unsafe extern "C" fn release(this: *mut bindings::config_item) { + // SAFETY: By function safety requirements, `this` is embedded in a + // `config_group`. + let c_group_ptr = unsafe { kernel::container_of!(this, bindings::config_group, cg_item) }; + // SAFETY: By function safety requirements, `c_group_ptr` is + // embedded within a `Group`. + let r_group_ptr = unsafe { Group::::container_of(c_group_ptr) }; + + // SAFETY: We called `into_foreign` on `r_group_ptr` in + // `make_group`. + let pin_self = + unsafe { > as ForeignOwnable>::from_foreign(r_group_ptr.cast_mut()) }; + drop(pin_self); + } + + const VTABLE: bindings::configfs_item_operations = bindings::configfs_item_operations { + release: Some(Self::release), + allow_link: None, + drop_link: None, + }; +} + +impl ItemOperationsVTable, Data> { + const VTABLE: bindings::configfs_item_operations = bindings::configfs_item_operations { + release: None, + allow_link: None, + drop_link: None, + }; +} + +/// Operations implemented by `configfs` groups that can create subgroups. +/// +/// Implement this trait on structs that embed a [`Subsystem`] or a [`Group`]. +#[vtable] +pub trait GroupOperations { + /// The parent data object type. + /// + /// The implementer of this trait is this kind of data object. Should be set + /// to `Self`. + type Parent; + + /// The child data object type. + /// + /// This group will create subgroups (subdirectories) backed by this kind of + /// object. + type Child: 'static; + + /// The kernel will call this method in response to `mkdir(2)` in the + /// directory representing `this`. + /// + /// To accept the request to create a group, implementations should + /// instantiate a `CHLD` and return a `CPTR` to it. To prevent creation, + /// return a suitable error. + fn make_group( + this: &Self::Parent, + name: &CStr, + ) -> Result, Error>>; + + /// The kernel will call this method before the directory representing + /// `_child` is removed from `configfs`. + /// + /// Implementations can use this method to do house keeping before + /// `configfs` drops its reference to `Child`. + fn drop_item( + _this: &Self::Parent, + _child: > as ForeignOwnable>::Borrowed<'_>, + ) { + kernel::build_error!(kernel::error::VTABLE_DEFAULT_ERROR) + } +} + +/// A `configfs` attribute. +/// +/// An attribute appear as a file in configfs, inside a folder that represent +/// the group that the attribute belongs to. +#[repr(transparent)] +pub struct Attribute { + attribute: Opaque, + _p: PhantomData<(O, Data)>, +} + +// SAFETY: We do not provide any operations on `Attribute`. +unsafe impl Sync for Attribute {} + +// SAFETY: Ownership of `Attribute` can safely be transferred to other threads. +unsafe impl Send for Attribute {} + +impl Attribute +where + O: AttributeOperations, +{ + /// # Safety + /// + /// `item` must be embedded in a `bindings::config_group`. + /// + /// If `item` does not represent the root group of a `configfs` subsystem, + /// the group must be embedded in a `Group`. + /// + /// Otherwise, the group must be a embedded in a + /// `bindings::configfs_subsystem` that is embedded in a `Subsystem`. + /// + /// `page` must point to a writable buffer of size at least [`PAGE_SIZE`]. + unsafe extern "C" fn show( + item: *mut bindings::config_item, + page: *mut kernel::ffi::c_char, + ) -> isize { + let c_group: *mut bindings::config_group = + // SAFETY: By function safety requirements, `item` is embedded in a + // `config_group`. + unsafe { container_of!(item, bindings::config_group, cg_item) }.cast_mut(); + + // SAFETY: The function safety requirements for this function satisfy + // the conditions for this call. + let data: &Data = unsafe { get_group_data(c_group) }; + + // SAFETY: By function safety requirements, `page` is writable for `PAGE_SIZE`. + let ret = O::show(data, unsafe { &mut *(page as *mut [u8; PAGE_SIZE]) }); + + match ret { + Ok(size) => size as isize, + Err(err) => err.to_errno() as isize, + } + } + + /// # Safety + /// + /// `item` must be embedded in a `bindings::config_group`. + /// + /// If `item` does not represent the root group of a `configfs` subsystem, + /// the group must be embedded in a `Group`. + /// + /// Otherwise, the group must be a embedded in a + /// `bindings::configfs_subsystem` that is embedded in a `Subsystem`. + /// + /// `page` must point to a readable buffer of size at least `size`. + unsafe extern "C" fn store( + item: *mut bindings::config_item, + page: *const kernel::ffi::c_char, + size: usize, + ) -> isize { + let c_group: *mut bindings::config_group = + // SAFETY: By function safety requirements, `item` is embedded in a + // `config_group`. + unsafe { container_of!(item, bindings::config_group, cg_item) }.cast_mut(); + + // SAFETY: The function safety requirements for this function satisfy + // the conditions for this call. + let data: &Data = unsafe { get_group_data(c_group) }; + + let ret = O::store( + data, + // SAFETY: By function safety requirements, `page` is readable + // for at least `size`. + unsafe { core::slice::from_raw_parts(page.cast(), size) }, + ); + + match ret { + Ok(()) => size as isize, + Err(err) => err.to_errno() as isize, + } + } + + /// Create a new attribute. + /// + /// The attribute will appear as a file with name given by `name`. + pub const fn new(name: &'static CStr) -> Self { + Self { + attribute: Opaque::new(bindings::configfs_attribute { + ca_name: name as *const _ as _, + ca_owner: core::ptr::null_mut(), + ca_mode: 0o660, + show: Some(Self::show), + store: if O::HAS_STORE { + Some(Self::store) + } else { + None + }, + }), + _p: PhantomData, + } + } +} + +/// Operations supported by an attribute. +/// +/// Implement this trait on type and pass that type as generic parameter when +/// creating an [`Attribute`]. The type carrying the implementation serve no +/// purpose other than specifying the attribute operations. +#[vtable] +pub trait AttributeOperations { + /// The type of the object that contains the field that is backing the + /// attribute for this operation. + type Data; + + /// This function is called by the kernel to read the value of an attribute. + /// + /// Implementations should write the rendering of the attribute to `page` + /// and return the number of bytes written. + fn show(data: &Self::Data, page: &mut [u8; PAGE_SIZE]) -> Result; + + /// This function is called by the kernel to update the value of an attribute. + /// + /// Implementations should parse the value from `page` and update internal + /// state to reflect the parsed value. Partial writes are not supported and + /// implementations should expect the full page to arrive in one write + /// operation. + fn store(_data: &Self::Data, _page: &[u8]) -> Result { + kernel::build_error!(kernel::error::VTABLE_DEFAULT_ERROR) + } +} + +/// A list of attributes. +/// +/// This type is used to construct a new [`ItemType`]. It represents a list of +/// [`Attribute`] that will appear in the directory representing a [`Group`]. +/// Users should not directly instantiate this type, rather they should use the +/// [`kernel::configfs_attrs`] macro to declare a static set of attributes for a +/// group. +#[repr(transparent)] +pub struct AttributeList( + UnsafeCell<[*mut kernel::ffi::c_void; N]>, + PhantomData, +); + +// SAFETY: Ownership of `AttributeList` can safely be transferred to other threads. +unsafe impl Send for AttributeList {} + +// SAFETY: We do not provide any operations on `AttributeList` that need synchronization. +unsafe impl Sync for AttributeList {} + +impl AttributeList { + #[doc(hidden)] + /// # Safety + /// + /// This function can only be called by expanding the `configfs_attrs` + /// macro. + pub const unsafe fn new() -> Self { + Self(UnsafeCell::new([core::ptr::null_mut(); N]), PhantomData) + } + + #[doc(hidden)] + /// # Safety + /// + /// This function can only be called by expanding the `configfs_attrs` + /// macro. + pub const unsafe fn add< + const I: usize, + const ID: u64, + O: AttributeOperations, + >( + &'static self, + attribute: &'static Attribute, + ) { + if I >= N - 1 { + kernel::build_error!("Invalid attribute index"); + } + + // SAFETY: This function is only called through `configfs_attrs`. This + // ensures that we are evaluating the function in const context when + // initializing a static. As such, the reference created below will be + // exclusive. + unsafe { + (&mut *self.0.get())[I] = (attribute as *const Attribute) + .cast_mut() + .cast() + }; + } +} + +/// A representation of the attributes that will appear in a [`Group`] or +/// [`Subsystem`]. +/// +/// Users should not directly instantiate objects of this type. Rather, they +/// should use the [`kernel::configfs_attrs`] macro to statically declare the +/// shape of a [`Group`] or [`Subsystem`]. +#[pin_data] +pub struct ItemType { + #[pin] + item_type: Opaque, + _p: PhantomData<(Container, Data)>, +} + +// SAFETY: We do not provide any operations on `ItemType` that need synchronization. +unsafe impl Sync for ItemType {} + +// SAFETY: Ownership of `ItemType` can safely be transferred to other threads. +unsafe impl Send for ItemType {} + +macro_rules! impl_item_type { + ($tpe:ty) => { + impl ItemType<$tpe, Data> { + #[doc(hidden)] + pub const fn new_with_child_ctor( + owner: &'static ThisModule, + attributes: &'static AttributeList, + ) -> Self + where + Data: GroupOperations, + Child: 'static, + { + Self { + item_type: Opaque::new(bindings::config_item_type { + ct_owner: owner.as_ptr(), + ct_group_ops: (&GroupOperationsVTable::::VTABLE as *const _) + as *mut _, + ct_item_ops: (&ItemOperationsVTable::<$tpe, Data>::VTABLE as *const _) + as *mut _, + ct_attrs: attributes as *const _ as _, + ct_bin_attrs: core::ptr::null_mut(), + }), + _p: PhantomData, + } + } + + #[doc(hidden)] + pub const fn new( + owner: &'static ThisModule, + attributes: &'static AttributeList, + ) -> Self { + Self { + item_type: Opaque::new(bindings::config_item_type { + ct_owner: owner.as_ptr(), + ct_group_ops: core::ptr::null_mut(), + ct_item_ops: (&ItemOperationsVTable::<$tpe, Data>::VTABLE as *const _) + as *mut _, + ct_attrs: attributes as *const _ as _, + ct_bin_attrs: core::ptr::null_mut(), + }), + _p: PhantomData, + } + } + } + }; +} + +impl_item_type!(Subsystem); +impl_item_type!(Group); + +impl ItemType { + fn as_ptr(&self) -> *const bindings::config_item_type { + self.item_type.get() + } +} + +/// Define a list of configfs attributes statically. +#[macro_export] +macro_rules! configfs_attrs { + ( + container: $container:ty, + data: $data:ty, + attributes: [ + $($name:ident: $attr:literal,)* + ], + ) => { + $crate::configfs_attrs!( + count: + @container($container), + @data($data), + @child(), + @no_child(x), + @attrs($($name $attr)*), + @eat($($name $attr,)*), + @assign(), + @cnt(0usize), + ) + }; + ( + container: $container:ty, + data: $data:ty, + child: $child:ty, + attributes: [ + $($name:ident: $attr:literal,)* + ], + ) => { + $crate::configfs_attrs!( + count: + @container($container), + @data($data), + @child($child), + @no_child(), + @attrs($($name $attr)*), + @eat($($name $attr,)*), + @assign(), + @cnt(0usize), + ) + }; + (count: + @container($container:ty), + @data($data:ty), + @child($($child:ty)?), + @no_child($($no_child:ident)?), + @attrs($($aname:ident $aattr:literal)*), + @eat($name:ident $attr:literal, $($rname:ident $rattr:literal,)*), + @assign($($assign:block)*), + @cnt($cnt:expr), + ) => { + $crate::configfs_attrs!( + count: + @container($container), + @data($data), + @child($($child)?), + @no_child($($no_child)?), + @attrs($($aname $aattr)*), + @eat($($rname $rattr,)*), + @assign($($assign)* { + const N: usize = $cnt; + // SAFETY: We are expanding `configfs_attrs`. + unsafe { + $crate::macros::paste!( [< $data:upper _ATTRS >]) + .add::( + & $crate::macros::paste!( [< $data:upper _ $name:upper _ATTR >]) + ) + }; + }), + @cnt(1usize + $cnt), + ) + }; + (count: + @container($container:ty), + @data($data:ty), + @child($($child:ty)?), + @no_child($($no_child:ident)?), + @attrs($($aname:ident $aattr:literal)*), + @eat(), + @assign($($assign:block)*), + @cnt($cnt:expr), + ) => + { + $crate::configfs_attrs!( + final: + @container($container), + @data($data), + @child($($child)?), + @no_child($($no_child)?), + @attrs($($aname $aattr)*), + @assign($($assign)*), + @cnt($cnt), + ) + }; + (final: + @container($container:ty), + @data($data:ty), + @child($($child:ty)?), + @no_child($($no_child:ident)?), + @attrs($($name:ident $attr:literal)*), + @assign($($assign:block)*), + @cnt($cnt:expr), + ) => + { + { + $( + $crate::macros::paste!{ + // SAFETY: We are expanding `configfs_attrs`. + static [< $data:upper _ $name:upper _ATTR >]: + $crate::configfs::Attribute<$attr, $data, $data> = + unsafe { + $crate::configfs::Attribute::new(c_str!(::core::stringify!($name))) + }; + } + )* + + + const N: usize = $cnt + 1usize; + $crate::macros::paste!{ + // SAFETY: We are expanding `configfs_attrs`. + static [< $data:upper _ATTRS >]: + $crate::configfs::AttributeList = + unsafe { $crate::configfs::AttributeList::new() }; + } + + $($assign)* + + $( + $crate::macros::paste!{ + const [<$no_child:upper>]: bool = true; + }; + + $crate::macros::paste!{ + static [< $data:upper _TPE >] : $crate::configfs::ItemType<$container, $data> = + $crate::configfs::ItemType::<$container, $data>::new::( + &THIS_MODULE, &[<$ data:upper _ATTRS >] + ); + } + )? + + $( + $crate::macros::paste!{ + static [< $data:upper _TPE >]: + $crate::configfs::ItemType<$container, $data> = + $crate::configfs::ItemType::<$container, $data>::new_with_child_ctor:: + ( + &THIS_MODULE, &[<$ data:upper _ATTRS >] + ); + } + )? + + &$crate::macros::paste!( [< $data:upper _TPE >] ) + } + }; + +} diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs index 496ed32b0911a..ec84653ab8c7a 100644 --- a/rust/kernel/lib.rs +++ b/rust/kernel/lib.rs @@ -40,6 +40,8 @@ pub mod block; #[doc(hidden)] pub mod build_assert; +#[cfg(CONFIG_CONFIGFS_FS)] +pub mod configfs; pub mod cred; pub mod device; pub mod device_id; diff --git a/samples/rust/Kconfig b/samples/rust/Kconfig index 918dbead2c0b4..2f97bf9a7b4cc 100644 --- a/samples/rust/Kconfig +++ b/samples/rust/Kconfig @@ -10,6 +10,17 @@ menuconfig SAMPLES_RUST if SAMPLES_RUST +config SAMPLE_RUST_CONFIGFS + tristate "Configfs sample" + depends on CONFIGFS_FS + help + This option builds the Rust configfs sample. + + To compile this as a module, choose M here: + the module will be called rust_configfs. + + If unsure, say N. + config SAMPLE_RUST_MINIMAL tristate "Minimal" help diff --git a/samples/rust/Makefile b/samples/rust/Makefile index 5a8ab0df0567c..72122f010cafc 100644 --- a/samples/rust/Makefile +++ b/samples/rust/Makefile @@ -6,6 +6,7 @@ obj-$(CONFIG_SAMPLE_RUST_MISC_DEVICE) += rust_misc_device.o obj-$(CONFIG_SAMPLE_RUST_PRINT) += rust_print.o obj-$(CONFIG_SAMPLE_RUST_DRIVER_PCI) += rust_driver_pci.o obj-$(CONFIG_SAMPLE_RUST_DRIVER_PLATFORM) += rust_driver_platform.o +obj-$(CONFIG_SAMPLE_RUST_CONFIGFS) += rust_configfs.o rust_print-y := rust_print_main.o rust_print_events.o diff --git a/samples/rust/rust_configfs.rs b/samples/rust/rust_configfs.rs new file mode 100644 index 0000000000000..fe896e66efb41 --- /dev/null +++ b/samples/rust/rust_configfs.rs @@ -0,0 +1,186 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! Rust configfs sample. + +use kernel::alloc::flags; +use kernel::c_str; +use kernel::configfs; +use kernel::configfs_attrs; +use kernel::new_mutex; +use kernel::prelude::*; +use kernel::sync::Mutex; + +module! { + type: RustConfigfs, + name: "rust_configfs", + author: "Rust for Linux Contributors", + description: "Rust configfs sample", + license: "GPL", +} + +#[pin_data] +struct RustConfigfs { + #[pin] + config: configfs::Subsystem, +} + +#[pin_data] +struct Configuration { + message: &'static CStr, + #[pin] + bar: Mutex<(KBox<[u8; 4096]>, usize)>, +} + +impl Configuration { + fn new() -> impl PinInit { + try_pin_init!(Self { + message: c_str!("Hello World\n"), + bar <- new_mutex!((KBox::new([0;4096], flags::GFP_KERNEL)?,0)), + }) + } +} + +impl kernel::InPlaceModule for RustConfigfs { + fn init(_module: &'static ThisModule) -> impl PinInit { + pr_info!("Rust configfs sample (init)\n"); + + let item_type = configfs_attrs! { + container: configfs::Subsystem, + data: Configuration, + child: Child, + attributes: [ + message: 0, + bar: 1, + ], + }; + + try_pin_init!(Self { + config <- configfs::Subsystem::new( + kernel::c_str!("rust_configfs"), item_type, Configuration::new() + ), + }) + } +} + +#[vtable] +impl configfs::GroupOperations for Configuration { + type Parent = Self; + type Child = Child; + + fn make_group( + _this: &Self, + name: &CStr, + ) -> Result, Error>> { + let tpe = configfs_attrs! { + container: configfs::Group, + data: Child, + child: GrandChild, + attributes: [ + baz: 0, + ], + }; + + Ok(configfs::Group::new(name.try_into()?, tpe, Child::new())) + } +} + +#[vtable] +impl configfs::AttributeOperations<0> for Configuration { + type Data = Configuration; + + fn show(container: &Configuration, page: &mut [u8; 4096]) -> Result { + pr_info!("Show message\n"); + let data = container.message; + page[0..data.len()].copy_from_slice(data); + Ok(data.len()) + } +} + +#[vtable] +impl configfs::AttributeOperations<1> for Configuration { + type Data = Configuration; + + fn show(container: &Configuration, page: &mut [u8; 4096]) -> Result { + pr_info!("Show bar\n"); + let guard = container.bar.lock(); + let data = guard.0.as_slice(); + let len = guard.1; + page[0..len].copy_from_slice(&data[0..len]); + Ok(len) + } + + fn store(container: &Configuration, page: &[u8]) -> Result { + pr_info!("Store bar\n"); + let mut guard = container.bar.lock(); + guard.0[0..page.len()].copy_from_slice(page); + guard.1 = page.len(); + Ok(()) + } +} + +#[pin_data] +struct Child {} + +impl Child { + fn new() -> impl PinInit { + try_pin_init!(Self {}) + } +} + +#[vtable] +impl configfs::GroupOperations for Child { + type Parent = Self; + type Child = GrandChild; + + fn make_group( + _this: &Self, + name: &CStr, + ) -> Result, Error>> { + let tpe = configfs_attrs! { + container: configfs::Group, + data: GrandChild, + attributes: [ + gc: 0, + ], + }; + + Ok(configfs::Group::new( + name.try_into()?, + tpe, + GrandChild::new(), + )) + } +} + +#[vtable] +impl configfs::AttributeOperations<0> for Child { + type Data = Child; + + fn show(_container: &Child, page: &mut [u8; 4096]) -> Result { + pr_info!("Show baz\n"); + let data = c"Hello Baz\n".to_bytes(); + page[0..data.len()].copy_from_slice(data); + Ok(data.len()) + } +} + +#[pin_data] +struct GrandChild {} + +impl GrandChild { + fn new() -> impl PinInit { + try_pin_init!(Self {}) + } +} + +#[vtable] +impl configfs::AttributeOperations<0> for GrandChild { + type Data = GrandChild; + + fn show(_container: &GrandChild, page: &mut [u8; 4096]) -> Result { + pr_info!("Show baz\n"); + let data = c"Hello GC\n".to_bytes(); + page[0..data.len()].copy_from_slice(data); + Ok(data.len()) + } +} -- 2.47.0