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([2a02:810d:4b3f:ee94:abf:b8ff:feee:998b]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4247d208b6bsm26585705e9.32.2024.06.20.06.43.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 20 Jun 2024 06:43:53 -0700 (PDT) Message-ID: Date: Thu, 20 Jun 2024 15:43:52 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 2/2] rust: add firmware abstractions To: Gary Guo Cc: gregkh@linuxfoundation.org, rafael@kernel.org, mcgrof@kernel.org, russ.weight@linux.dev, ojeda@kernel.org, alex.gaynor@gmail.com, wedsonaf@gmail.com, boqun.feng@gmail.com, bjorn3_gh@protonmail.com, benno.lossin@proton.me, a.hindborg@samsung.com, aliceryhl@google.com, airlied@gmail.com, fujita.tomonori@gmail.com, pstanner@redhat.com, ajanulgu@redhat.com, lyude@redhat.com, rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org References: <20240618154841.6716-1-dakr@redhat.com> <20240618154841.6716-3-dakr@redhat.com> <20240620143611.7995e0bb@eugeo> Content-Language: en-US From: Danilo Krummrich Organization: RedHat In-Reply-To: <20240620143611.7995e0bb@eugeo> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 6/20/24 15:36, Gary Guo wrote: > On Tue, 18 Jun 2024 17:48:35 +0200 > Danilo Krummrich wrote: > >> Add an abstraction around the kernels firmware API to request firmware >> images. The abstraction provides functions to access the firmware's size >> and backing buffer. >> >> The firmware is released once the abstraction instance is dropped. >> >> Signed-off-by: Danilo Krummrich >> --- >> drivers/base/firmware_loader/Kconfig | 7 ++ >> rust/bindings/bindings_helper.h | 1 + >> rust/kernel/firmware.rs | 101 +++++++++++++++++++++++++++ >> rust/kernel/lib.rs | 2 + >> 4 files changed, 111 insertions(+) >> create mode 100644 rust/kernel/firmware.rs >> >> diff --git a/drivers/base/firmware_loader/Kconfig b/drivers/base/firmware_loader/Kconfig >> index 5ca00e02fe82..a03701674265 100644 >> --- a/drivers/base/firmware_loader/Kconfig >> +++ b/drivers/base/firmware_loader/Kconfig >> @@ -37,6 +37,13 @@ config FW_LOADER_DEBUG >> SHA256 checksums to the kernel log for each firmware file that is >> loaded. >> >> +config RUST_FW_LOADER_ABSTRACTIONS >> + bool "Rust Firmware Loader abstractions" >> + depends on RUST >> + depends on FW_LOADER=y >> + help >> + This enables the Rust abstractions for the firmware loader API. >> + >> if FW_LOADER >> >> config FW_LOADER_PAGED_BUF >> diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h >> index ddb5644d4fd9..18a3f05115cb 100644 >> --- a/rust/bindings/bindings_helper.h >> +++ b/rust/bindings/bindings_helper.h >> @@ -9,6 +9,7 @@ >> #include >> #include >> #include >> +#include >> #include >> #include >> #include >> diff --git a/rust/kernel/firmware.rs b/rust/kernel/firmware.rs >> new file mode 100644 >> index 000000000000..b55ea1b45368 >> --- /dev/null >> +++ b/rust/kernel/firmware.rs >> @@ -0,0 +1,101 @@ >> +// SPDX-License-Identifier: GPL-2.0 >> + >> +//! Firmware abstraction >> +//! >> +//! C header: [`include/linux/firmware.h`](srctree/include/linux/firmware.h") >> + >> +use crate::{bindings, device::Device, error::Error, error::Result, str::CStr}; >> +use core::ptr::NonNull; >> + >> +// One of the following: `bindings::request_firmware`, `bindings::firmware_request_nowarn`, >> +// `firmware_request_platform`, `bindings::request_firmware_direct` >> +type FwFunc = >> + unsafe extern "C" fn(*mut *const bindings::firmware, *const i8, *mut bindings::device) -> i32; >> + >> +/// Abstraction around a C `struct firmware`. >> +/// >> +/// This is a simple abstraction around the C firmware API. Just like with the C API, firmware can >> +/// be requested. Once requested the abstraction provides direct access to the firmware buffer as >> +/// `&[u8]`. The firmware is released once [`Firmware`] is dropped. >> +/// >> +/// # Invariants >> +/// >> +/// The pointer is valid, and has ownership over the instance of `struct firmware`. >> +/// >> +/// Once requested, the `Firmware` backing buffer is not modified until it is freed when `Firmware` >> +/// is dropped. >> +/// >> +/// # Examples >> +/// >> +/// ``` >> +/// # use kernel::{c_str, device::Device, firmware::Firmware}; >> +/// >> +/// # // SAFETY: *NOT* safe, just for the example to get an `ARef` instance >> +/// # let dev = unsafe { Device::from_raw(core::ptr::null_mut()) }; >> +/// >> +/// let fw = Firmware::request(c_str!("path/to/firmware.bin"), &dev).unwrap(); >> +/// let blob = fw.data(); >> +/// ``` >> +pub struct Firmware(NonNull); >> + >> +impl Firmware { >> + fn request_internal(name: &CStr, dev: &Device, func: FwFunc) -> Result { >> + let mut fw: *mut bindings::firmware = core::ptr::null_mut(); >> + let pfw: *mut *mut bindings::firmware = &mut fw; >> + >> + // SAFETY: `pfw` is a valid pointer to a NULL initialized `bindings::firmware` pointer. >> + // `name` and `dev` are valid as by their type invariants. >> + let ret = unsafe { func(pfw as _, name.as_char_ptr(), dev.as_raw()) }; > > This is line is unsound if this function is called with an arbitrary > FwFunc, therefore the safety comment should also mention that `func` > cannot be an arbitrary function and it must be one of > `request_firmware`, `firmware_request_nowarn`, > `firmware_request_platform`, `request_firmware_direct`, and this is This is documented in the type definition of `FwFunc`. We can link to this invariant though and explicitly mark it as such. Does that make sense? - Danilo > true because the function is not public and all users in the file > satisfy this safety precondition. > > >> + if ret != 0 { >> + return Err(Error::from_errno(ret)); >> + } >> + >> + // SAFETY: `func` not bailing out with a non-zero error code, guarantees that `fw` is a >> + // valid pointer to `bindings::firmware`. >> + Ok(Firmware(unsafe { NonNull::new_unchecked(fw) })) >> + } >> + >> + /// Send a firmware request and wait for it. See also `bindings::request_firmware`. >> + pub fn request(name: &CStr, dev: &Device) -> Result { >> + Self::request_internal(name, dev, bindings::request_firmware) >> + } >> + >> + /// Send a request for an optional firmware module. See also >> + /// `bindings::firmware_request_nowarn`. >> + pub fn request_nowarn(name: &CStr, dev: &Device) -> Result { >> + Self::request_internal(name, dev, bindings::firmware_request_nowarn) >> + } >> + >> + fn as_raw(&self) -> *mut bindings::firmware { >> + self.0.as_ptr() >> + } >> + >> + /// Returns the size of the requested firmware in bytes. >> + pub fn size(&self) -> usize { >> + // SAFETY: Safe by the type invariant. >> + unsafe { (*self.as_raw()).size } >> + } >> + >> + /// Returns the requested firmware as `&[u8]`. >> + pub fn data(&self) -> &[u8] { >> + // SAFETY: Safe by the type invariant. Additionally, `bindings::firmware` guarantees, if >> + // successfully requested, that `bindings::firmware::data` has a size of >> + // `bindings::firmware::size` bytes. >> + unsafe { core::slice::from_raw_parts((*self.as_raw()).data, self.size()) } >> + } >> +} >> + >> +impl Drop for Firmware { >> + fn drop(&mut self) { >> + // SAFETY: Safe by the type invariant. >> + unsafe { bindings::release_firmware(self.as_raw()) }; >> + } >> +} >> + >> +// SAFETY: `Firmware` only holds a pointer to a C `struct firmware`, which is safe to be used from >> +// any thread. >> +unsafe impl Send for Firmware {} >> + >> +// SAFETY: `Firmware` only holds a pointer to a C `struct firmware`, references to which are safe to >> +// be used from any thread. >> +unsafe impl Sync for Firmware {} >> diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs >> index dd1207f1a873..7707cb013ce9 100644 >> --- a/rust/kernel/lib.rs >> +++ b/rust/kernel/lib.rs >> @@ -30,6 +30,8 @@ >> mod build_assert; >> pub mod device; >> pub mod error; >> +#[cfg(CONFIG_RUST_FW_LOADER_ABSTRACTIONS)] >> +pub mod firmware; >> pub mod init; >> pub mod ioctl; >> #[cfg(CONFIG_KUNIT)] >