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 4051D27A13A; Wed, 2 Jul 2025 13:19:24 +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=1751462364; cv=none; b=sJswNbQSNx8yBZ9GgzN2eC2t59X/H1Hl2pFDtxlY4jQD6bV+E6Op8jHvutjPoUCENw80dBrdGcZTsFmCEEuLgfGTZO3pzXhD8hStXcCPuuDBTNow2r3tgLPfj09OF3rn+iAb5BRVciNehbPibYwfQtLT6AwJSr1mNdM7IAku8xM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751462364; c=relaxed/simple; bh=GINSHYwROTV6WI3RSAoMCRmq0RKzfKvRWX79JeAlh8Y=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=m6WdQXb++fluejyTDoL07WeWReisxQrSDxiRW/D+TGOiN743qnl5KM4Ra2QktQrEyssWX/TuFLG1jPfHvaat1pq2apkXyeYErbfLbhouYRLlOjkhWbOeUWqL0fVQWebjJmB4JZsdyXVDFSAbH0x7tr3d5fzf53hHtTj3ZExcRc4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=bHKJeoJn; 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="bHKJeoJn" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DDD0EC4CEEF; Wed, 2 Jul 2025 13:19:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1751462363; bh=GINSHYwROTV6WI3RSAoMCRmq0RKzfKvRWX79JeAlh8Y=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=bHKJeoJnTEzbknH914OXRflq+RbJpZ+iW7v7bTgSHZf9jqekqYFRQ8SpsUnTyZvxq ev/PyaqvGGT8tWMuX5k7BH28fMN9t/lRZKW3CkP+7A1pGKukkpodGldhGHi9FAibrx bpcWeYd4Nv5yEpjHrkCN6Ox5qwG139W3DF3qV355r43SBNHM2NF7eYoei1uW5gS0Gg no2HJXh86mcvN2Yty6UyYW6ZqsonzAPV3Luk2hOEu5d5p/eXAGMcZzCcZzdPIdwgdz j4kKFBvWm36bTzMLLvV1cdTXtakBZ3kmJAo7nrYaiwliLcrsDh5J1YN7gYY23VvfYs kth86SZ80CO0w== From: Andreas Hindborg Date: Wed, 02 Jul 2025 15:18:35 +0200 Subject: [PATCH v14 3/7] rust: introduce module_param module Precedence: bulk X-Mailing-List: linux-kernel@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: <20250702-module-params-v3-v14-3-5b1cc32311af@kernel.org> References: <20250702-module-params-v3-v14-0-5b1cc32311af@kernel.org> In-Reply-To: <20250702-module-params-v3-v14-0-5b1cc32311af@kernel.org> To: Miguel Ojeda , Alex Gaynor , Boqun Feng , Gary Guo , =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= , Alice Ryhl , Masahiro Yamada , Nathan Chancellor , Luis Chamberlain , Danilo Krummrich , Benno Lossin , Benno Lossin , Nicolas Schier Cc: Trevor Gross , Adam Bratschi-Kaye , rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kbuild@vger.kernel.org, Petr Pavlu , Sami Tolvanen , Daniel Gomez , Simona Vetter , Greg KH , Fiona Behrens , Daniel Almeida , linux-modules@vger.kernel.org, Andreas Hindborg X-Mailer: b4 0.15-dev X-Developer-Signature: v=1; a=openpgp-sha256; l=7330; i=a.hindborg@kernel.org; h=from:subject:message-id; bh=GINSHYwROTV6WI3RSAoMCRmq0RKzfKvRWX79JeAlh8Y=; b=owEBbQKS/ZANAwAIAeG4Gj55KGN3AcsmYgBoZTG0VAFw3SWRtVJIdAn1HRC955GhaE4foFVRg DGl8dp6xYWJAjMEAAEIAB0WIQQSwflHVr98KhXWwBLhuBo+eShjdwUCaGUxtAAKCRDhuBo+eShj d2OfEAC2Ns/toQDjzh0HLTj3WAAEGJcR+4EOHmUNJuw6Wr8ri1cHPmsBccPgKw9vq73OPpdlfbd F9gwfrBVy7XcwB2ernkxz0wBgkab2WkaZNeWwki/XqCNsPYVQJ84C+i/XfHG2fCt0Mg17FihPnV IL8yQSA9FLf61mdERtJ6HwC560GNckvGb0v5QysxfAc+aH7omhUkFFgbIFsM/XNuFGOdyg0bPVQ u86pMsFJMxuTjrrms1MADrnnQV7xKttbtshRR6hNumA4P8SMEEytg6n++EFG/WKLkQ/kvetO7oT K1jBrtLgoqpt4mqIEjBfALiPix6ZaFivCjzf8VQsLdDuBLXgFc4ijV/TTGUOvg7VOvFtqxu6mfB 3Tc7j/reD8phAA04uF9iPESSnnFc4QcXNY8BwA+ziUCL9ul5ERuXJtoQNe0ZFsKtT5AN0N+PTHV 3u6glZ25s1adrSCIHHt8fBFEZuLJEPi//kdhm4ScHzDE2M43mOTEqS1Df84IeThxYdZAXJI6g44 3Rgfb1GcG5MtgRKOrzCU14elE323EEMtaj3Y1H87LlmY5h+gKPFJ87sh7CHi9D62e3hQsY1fmFD kZqo/gMSTKBOqAjH5rLLTZTrfCxCJTuH1zIPskQwxfYL5yhyLlfKyx10x4CVdLYkkIVG0nb3lYv K/hg2B8W7tRsuTg== X-Developer-Key: i=a.hindborg@kernel.org; a=openpgp; fpr=3108C10F46872E248D1FB221376EB100563EF7A7 Add types and traits for interfacing the C moduleparam API. Signed-off-by: Andreas Hindborg --- rust/kernel/lib.rs | 1 + rust/kernel/module_param.rs | 191 ++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 192 insertions(+) diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs index 6b4774b2b1c3..2b439ea06185 100644 --- a/rust/kernel/lib.rs +++ b/rust/kernel/lib.rs @@ -87,6 +87,7 @@ pub mod list; pub mod miscdevice; pub mod mm; +pub mod module_param; #[cfg(CONFIG_NET)] pub mod net; pub mod of; diff --git a/rust/kernel/module_param.rs b/rust/kernel/module_param.rs new file mode 100644 index 000000000000..ca4be7e45ff7 --- /dev/null +++ b/rust/kernel/module_param.rs @@ -0,0 +1,191 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! Support for module parameters. +//! +//! C header: [`include/linux/moduleparam.h`](srctree/include/linux/moduleparam.h) + +use crate::prelude::*; +use crate::str::BStr; +use bindings; +use kernel::sync::once_lock::OnceLock; + +/// Newtype to make `bindings::kernel_param` [`Sync`]. +#[repr(transparent)] +#[doc(hidden)] +pub struct RacyKernelParam(bindings::kernel_param); + +impl RacyKernelParam { + #[doc(hidden)] + pub const fn new(val: bindings::kernel_param) -> Self { + Self(val) + } +} + +// SAFETY: C kernel handles serializing access to this type. We never access it +// from Rust module. +unsafe impl Sync for RacyKernelParam {} + +/// Types that can be used for module parameters. +// NOTE: This trait is `Copy` because drop could produce unsoundness during teardown. +pub trait ModuleParam: Sized + Copy { + /// The [`ModuleParam`] will be used by the kernel module through this type. + /// + /// This may differ from `Self` if, for example, `Self` needs to track + /// ownership without exposing it or allocate extra space for other possible + /// parameter values. + // This is required to support string parameters in the future. + type Value: ?Sized; + + /// Parse a parameter argument into the parameter value. + fn try_from_param_arg(arg: &BStr) -> Result; +} + +/// Set the module parameter from a string. +/// +/// Used to set the parameter value at kernel initialization, when loading +/// the module or when set through `sysfs`. +/// +/// See `struct kernel_param_ops.set`. +/// +/// # Safety +/// +/// - If `val` is non-null then it must point to a valid null-terminated string that must be valid +/// for reads for the duration of the call. +/// - `param` must be a pointer to a `bindings::kernel_param` initialized by the rust module macro. +/// The pointee must be valid for reads for the duration of the call. +/// +/// # Note +/// +/// - The safety requirements are satisfied by C API contract when this function is invoked by the +/// module subsystem C code. +/// - Currently, we only support read-only parameters that are not readable from `sysfs`. Thus, this +/// function is only called at kernel initialization time, or at module load time, and we have +/// exclusive access to the parameter for the duration of the function. +/// +/// [`module!`]: macros::module +unsafe extern "C" fn set_param(val: *const c_char, param: *const bindings::kernel_param) -> c_int +where + T: ModuleParam, +{ + // NOTE: If we start supporting arguments without values, val _is_ allowed + // to be null here. + if val.is_null() { + // TODO: Use pr_warn_once available. + crate::pr_warn!("Null pointer passed to `module_param::set_param`"); + return EINVAL.to_errno(); + } + + // SAFETY: By function safety requirement, val is non-null, null-terminated + // and valid for reads for the duration of this function. + let arg = unsafe { CStr::from_char_ptr(val) }; + + crate::error::from_result(|| { + let new_value = T::try_from_param_arg(arg)?; + + // SAFETY: By function safety requirements, this access is safe. + let container = unsafe { &*((*param).__bindgen_anon_1.arg as *mut OnceLock) }; + + container + .populate(new_value) + .then_some(0) + .ok_or(kernel::error::code::EEXIST) + }) +} + +macro_rules! impl_int_module_param { + ($ty:ident) => { + impl ModuleParam for $ty { + type Value = $ty; + + fn try_from_param_arg(arg: &BStr) -> Result { + <$ty as crate::str::parse_int::ParseInt>::from_str(arg) + } + } + }; +} + +impl_int_module_param!(i8); +impl_int_module_param!(u8); +impl_int_module_param!(i16); +impl_int_module_param!(u16); +impl_int_module_param!(i32); +impl_int_module_param!(u32); +impl_int_module_param!(i64); +impl_int_module_param!(u64); +impl_int_module_param!(isize); +impl_int_module_param!(usize); + +/// A wrapper for kernel parameters. +/// +/// This type is instantiated by the [`module!`] macro when module parameters are +/// defined. You should never need to instantiate this type directly. +/// +/// Note: This type is `pub` because it is used by module crates to access +/// parameter values. +pub struct ModuleParamAccess { + value: OnceLock, + default: T, +} + +// SAFETY: We only create shared references to the contents of this container, +// so if `T` is `Sync`, so is `ModuleParamAccess`. +unsafe impl Sync for ModuleParamAccess {} + +impl ModuleParamAccess { + #[doc(hidden)] + pub const fn new(default: T) -> Self { + Self { + value: OnceLock::new(), + default, + } + } + + /// Get a shared reference to the parameter value. + // Note: When sysfs access to parameters are enabled, we have to pass in a + // held lock guard here. + pub fn get(&self) -> &T { + self.value.as_ref().unwrap_or(&self.default) + } + + /// Get a mutable pointer to `self`. + /// + /// NOTE: In most cases it is not safe deref the returned pointer. + pub const fn as_void_ptr(&self) -> *mut c_void { + (self as *const Self).cast_mut().cast() + } +} + +#[doc(hidden)] +/// Generate a static [`kernel_param_ops`](srctree/include/linux/moduleparam.h) struct. +/// +/// # Examples +/// +/// ```ignore +/// make_param_ops!( +/// /// Documentation for new param ops. +/// PARAM_OPS_MYTYPE, // Name for the static. +/// MyType // A type which implements [`ModuleParam`]. +/// ); +/// ``` +macro_rules! make_param_ops { + ($ops:ident, $ty:ty) => { + #[doc(hidden)] + pub static $ops: $crate::bindings::kernel_param_ops = $crate::bindings::kernel_param_ops { + flags: 0, + set: Some(set_param::<$ty>), + get: None, + free: None, + }; + }; +} + +make_param_ops!(PARAM_OPS_I8, i8); +make_param_ops!(PARAM_OPS_U8, u8); +make_param_ops!(PARAM_OPS_I16, i16); +make_param_ops!(PARAM_OPS_U16, u16); +make_param_ops!(PARAM_OPS_I32, i32); +make_param_ops!(PARAM_OPS_U32, u32); +make_param_ops!(PARAM_OPS_I64, i64); +make_param_ops!(PARAM_OPS_U64, u64); +make_param_ops!(PARAM_OPS_ISIZE, isize); +make_param_ops!(PARAM_OPS_USIZE, usize); -- 2.47.2