linux/rust/kernel/debugfs.rs

595 lines
20 KiB
Rust

// SPDX-License-Identifier: GPL-2.0
// Copyright (C) 2025 Google LLC.
//! DebugFS Abstraction
//!
//! C header: [`include/linux/debugfs.h`](srctree/include/linux/debugfs.h)
// When DebugFS is disabled, many parameters are dead. Linting for this isn't helpful.
#![cfg_attr(not(CONFIG_DEBUG_FS), allow(unused_variables))]
use crate::prelude::*;
use crate::str::CStr;
#[cfg(CONFIG_DEBUG_FS)]
use crate::sync::Arc;
use crate::uaccess::UserSliceReader;
use core::fmt;
use core::marker::PhantomData;
use core::marker::PhantomPinned;
#[cfg(CONFIG_DEBUG_FS)]
use core::mem::ManuallyDrop;
use core::ops::Deref;
mod traits;
pub use traits::{Reader, Writer};
mod callback_adapters;
use callback_adapters::{FormatAdapter, NoWriter, WritableAdapter};
mod file_ops;
use file_ops::{FileOps, ReadFile, ReadWriteFile, WriteFile};
#[cfg(CONFIG_DEBUG_FS)]
mod entry;
#[cfg(CONFIG_DEBUG_FS)]
use entry::Entry;
/// Owning handle to a DebugFS directory.
///
/// The directory in the filesystem represented by [`Dir`] will be removed when handle has been
/// dropped *and* all children have been removed.
// If we have a parent, we hold a reference to it in the `Entry`. This prevents the `dentry`
// we point to from being cleaned up if our parent `Dir`/`Entry` is dropped before us.
//
// The `None` option indicates that the `Arc` could not be allocated, so our children would not be
// able to refer to us. In this case, we need to silently fail. All future child directories/files
// will silently fail as well.
#[derive(Clone)]
pub struct Dir(#[cfg(CONFIG_DEBUG_FS)] Option<Arc<Entry<'static>>>);
impl Dir {
/// Create a new directory in DebugFS. If `parent` is [`None`], it will be created at the root.
fn create(name: &CStr, parent: Option<&Dir>) -> Self {
#[cfg(CONFIG_DEBUG_FS)]
{
let parent_entry = match parent {
// If the parent couldn't be allocated, just early-return
Some(Dir(None)) => return Self(None),
Some(Dir(Some(entry))) => Some(entry.clone()),
None => None,
};
Self(
// If Arc creation fails, the `Entry` will be dropped, so the directory will be
// cleaned up.
Arc::new(Entry::dynamic_dir(name, parent_entry), GFP_KERNEL).ok(),
)
}
#[cfg(not(CONFIG_DEBUG_FS))]
Self()
}
/// Creates a DebugFS file which will own the data produced by the initializer provided in
/// `data`.
fn create_file<'a, T, E: 'a>(
&'a self,
name: &'a CStr,
data: impl PinInit<T, E> + 'a,
file_ops: &'static FileOps<T>,
) -> impl PinInit<File<T>, E> + 'a
where
T: Sync + 'static,
{
let scope = Scope::<T>::new(data, move |data| {
#[cfg(CONFIG_DEBUG_FS)]
if let Some(parent) = &self.0 {
// SAFETY: Because data derives from a scope, and our entry will be dropped before
// the data is dropped, it is guaranteed to outlive the entry we return.
unsafe { Entry::dynamic_file(name, parent.clone(), data, file_ops) }
} else {
Entry::empty()
}
});
try_pin_init! {
File {
scope <- scope
} ? E
}
}
/// Create a new directory in DebugFS at the root.
///
/// # Examples
///
/// ```
/// # use kernel::c_str;
/// # use kernel::debugfs::Dir;
/// let debugfs = Dir::new(c_str!("parent"));
/// ```
pub fn new(name: &CStr) -> Self {
Dir::create(name, None)
}
/// Creates a subdirectory within this directory.
///
/// # Examples
///
/// ```
/// # use kernel::c_str;
/// # use kernel::debugfs::Dir;
/// let parent = Dir::new(c_str!("parent"));
/// let child = parent.subdir(c_str!("child"));
/// ```
pub fn subdir(&self, name: &CStr) -> Self {
Dir::create(name, Some(self))
}
/// Creates a read-only file in this directory.
///
/// The file's contents are produced by invoking [`Writer::write`] on the value initialized by
/// `data`.
///
/// # Examples
///
/// ```
/// # use kernel::c_str;
/// # use kernel::debugfs::Dir;
/// # use kernel::prelude::*;
/// # let dir = Dir::new(c_str!("my_debugfs_dir"));
/// let file = KBox::pin_init(dir.read_only_file(c_str!("foo"), 200), GFP_KERNEL)?;
/// // "my_debugfs_dir/foo" now contains the number 200.
/// // The file is removed when `file` is dropped.
/// # Ok::<(), Error>(())
/// ```
pub fn read_only_file<'a, T, E: 'a>(
&'a self,
name: &'a CStr,
data: impl PinInit<T, E> + 'a,
) -> impl PinInit<File<T>, E> + 'a
where
T: Writer + Send + Sync + 'static,
{
let file_ops = &<T as ReadFile<_>>::FILE_OPS;
self.create_file(name, data, file_ops)
}
/// Creates a read-only file in this directory, with contents from a callback.
///
/// `f` must be a function item or a non-capturing closure.
/// This is statically asserted and not a safety requirement.
///
/// # Examples
///
/// ```
/// # use core::sync::atomic::{AtomicU32, Ordering};
/// # use kernel::c_str;
/// # use kernel::debugfs::Dir;
/// # use kernel::prelude::*;
/// # let dir = Dir::new(c_str!("foo"));
/// let file = KBox::pin_init(
/// dir.read_callback_file(c_str!("bar"),
/// AtomicU32::new(3),
/// &|val, f| {
/// let out = val.load(Ordering::Relaxed);
/// writeln!(f, "{out:#010x}")
/// }),
/// GFP_KERNEL)?;
/// // Reading "foo/bar" will show "0x00000003".
/// file.store(10, Ordering::Relaxed);
/// // Reading "foo/bar" will now show "0x0000000a".
/// # Ok::<(), Error>(())
/// ```
pub fn read_callback_file<'a, T, E: 'a, F>(
&'a self,
name: &'a CStr,
data: impl PinInit<T, E> + 'a,
_f: &'static F,
) -> impl PinInit<File<T>, E> + 'a
where
T: Send + Sync + 'static,
F: Fn(&T, &mut fmt::Formatter<'_>) -> fmt::Result + Send + Sync,
{
let file_ops = <FormatAdapter<T, F>>::FILE_OPS.adapt();
self.create_file(name, data, file_ops)
}
/// Creates a read-write file in this directory.
///
/// Reading the file uses the [`Writer`] implementation.
/// Writing to the file uses the [`Reader`] implementation.
pub fn read_write_file<'a, T, E: 'a>(
&'a self,
name: &'a CStr,
data: impl PinInit<T, E> + 'a,
) -> impl PinInit<File<T>, E> + 'a
where
T: Writer + Reader + Send + Sync + 'static,
{
let file_ops = &<T as ReadWriteFile<_>>::FILE_OPS;
self.create_file(name, data, file_ops)
}
/// Creates a read-write file in this directory, with logic from callbacks.
///
/// Reading from the file is handled by `f`. Writing to the file is handled by `w`.
///
/// `f` and `w` must be function items or non-capturing closures.
/// This is statically asserted and not a safety requirement.
pub fn read_write_callback_file<'a, T, E: 'a, F, W>(
&'a self,
name: &'a CStr,
data: impl PinInit<T, E> + 'a,
_f: &'static F,
_w: &'static W,
) -> impl PinInit<File<T>, E> + 'a
where
T: Send + Sync + 'static,
F: Fn(&T, &mut fmt::Formatter<'_>) -> fmt::Result + Send + Sync,
W: Fn(&T, &mut UserSliceReader) -> Result + Send + Sync,
{
let file_ops =
<WritableAdapter<FormatAdapter<T, F>, W> as file_ops::ReadWriteFile<_>>::FILE_OPS
.adapt()
.adapt();
self.create_file(name, data, file_ops)
}
/// Creates a write-only file in this directory.
///
/// The file owns its backing data. Writing to the file uses the [`Reader`]
/// implementation.
///
/// The file is removed when the returned [`File`] is dropped.
pub fn write_only_file<'a, T, E: 'a>(
&'a self,
name: &'a CStr,
data: impl PinInit<T, E> + 'a,
) -> impl PinInit<File<T>, E> + 'a
where
T: Reader + Send + Sync + 'static,
{
self.create_file(name, data, &T::FILE_OPS)
}
/// Creates a write-only file in this directory, with write logic from a callback.
///
/// `w` must be a function item or a non-capturing closure.
/// This is statically asserted and not a safety requirement.
pub fn write_callback_file<'a, T, E: 'a, W>(
&'a self,
name: &'a CStr,
data: impl PinInit<T, E> + 'a,
_w: &'static W,
) -> impl PinInit<File<T>, E> + 'a
where
T: Send + Sync + 'static,
W: Fn(&T, &mut UserSliceReader) -> Result + Send + Sync,
{
let file_ops = <WritableAdapter<NoWriter<T>, W> as WriteFile<_>>::FILE_OPS
.adapt()
.adapt();
self.create_file(name, data, file_ops)
}
// While this function is safe, it is intentionally not public because it's a bit of a
// footgun.
//
// Unless you also extract the `entry` later and schedule it for `Drop` at the appropriate
// time, a `ScopedDir` with a `Dir` parent will never be deleted.
fn scoped_dir<'data>(&self, name: &CStr) -> ScopedDir<'data, 'static> {
#[cfg(CONFIG_DEBUG_FS)]
{
let parent_entry = match &self.0 {
None => return ScopedDir::empty(),
Some(entry) => entry.clone(),
};
ScopedDir {
entry: ManuallyDrop::new(Entry::dynamic_dir(name, Some(parent_entry))),
_phantom: PhantomData,
}
}
#[cfg(not(CONFIG_DEBUG_FS))]
ScopedDir::empty()
}
/// Creates a new scope, which is a directory associated with some data `T`.
///
/// The created directory will be a subdirectory of `self`. The `init` closure is called to
/// populate the directory with files and subdirectories. These files can reference the data
/// stored in the scope.
///
/// The entire directory tree created within the scope will be removed when the returned
/// `Scope` handle is dropped.
pub fn scope<'a, T: 'a, E: 'a, F>(
&'a self,
data: impl PinInit<T, E> + 'a,
name: &'a CStr,
init: F,
) -> impl PinInit<Scope<T>, E> + 'a
where
F: for<'data, 'dir> FnOnce(&'data T, &'dir ScopedDir<'data, 'dir>) + 'a,
{
Scope::new(data, |data| {
let scoped = self.scoped_dir(name);
init(data, &scoped);
scoped.into_entry()
})
}
}
#[pin_data]
/// Handle to a DebugFS scope, which ensures that attached `data` will outlive the DebugFS entry
/// without moving.
///
/// This is internally used to back [`File`], and used in the API to represent the attachment
/// of a directory lifetime to a data structure which may be jointly accessed by a number of
/// different files.
///
/// When dropped, a `Scope` will remove all directories and files in the filesystem backed by the
/// attached data structure prior to releasing the attached data.
pub struct Scope<T> {
// This order is load-bearing for drops - `_entry` must be dropped before `data`.
#[cfg(CONFIG_DEBUG_FS)]
_entry: Entry<'static>,
#[pin]
data: T,
// Even if `T` is `Unpin`, we still can't allow it to be moved.
#[pin]
_pin: PhantomPinned,
}
#[pin_data]
/// Handle to a DebugFS file, owning its backing data.
///
/// When dropped, the DebugFS file will be removed and the attached data will be dropped.
pub struct File<T> {
#[pin]
scope: Scope<T>,
}
#[cfg(not(CONFIG_DEBUG_FS))]
impl<'b, T: 'b> Scope<T> {
fn new<E: 'b, F>(data: impl PinInit<T, E> + 'b, init: F) -> impl PinInit<Self, E> + 'b
where
F: for<'a> FnOnce(&'a T) + 'b,
{
try_pin_init! {
Self {
data <- data,
_pin: PhantomPinned
} ? E
}
.pin_chain(|scope| {
init(&scope.data);
Ok(())
})
}
}
#[cfg(CONFIG_DEBUG_FS)]
impl<'b, T: 'b> Scope<T> {
fn entry_mut(self: Pin<&mut Self>) -> &mut Entry<'static> {
// SAFETY: _entry is not structurally pinned.
unsafe { &mut Pin::into_inner_unchecked(self)._entry }
}
fn new<E: 'b, F>(data: impl PinInit<T, E> + 'b, init: F) -> impl PinInit<Self, E> + 'b
where
F: for<'a> FnOnce(&'a T) -> Entry<'static> + 'b,
{
try_pin_init! {
Self {
_entry: Entry::empty(),
data <- data,
_pin: PhantomPinned
} ? E
}
.pin_chain(|scope| {
*scope.entry_mut() = init(&scope.data);
Ok(())
})
}
}
impl<'a, T: 'a> Scope<T> {
/// Creates a new scope, which is a directory at the root of the debugfs filesystem,
/// associated with some data `T`.
///
/// The `init` closure is called to populate the directory with files and subdirectories. These
/// files can reference the data stored in the scope.
///
/// The entire directory tree created within the scope will be removed when the returned
/// `Scope` handle is dropped.
pub fn dir<E: 'a, F>(
data: impl PinInit<T, E> + 'a,
name: &'a CStr,
init: F,
) -> impl PinInit<Self, E> + 'a
where
F: for<'data, 'dir> FnOnce(&'data T, &'dir ScopedDir<'data, 'dir>) + 'a,
{
Scope::new(data, |data| {
let scoped = ScopedDir::new(name);
init(data, &scoped);
scoped.into_entry()
})
}
}
impl<T> Deref for Scope<T> {
type Target = T;
fn deref(&self) -> &T {
&self.data
}
}
impl<T> Deref for File<T> {
type Target = T;
fn deref(&self) -> &T {
&self.scope
}
}
/// A handle to a directory which will live at most `'dir`, accessing data that will live for at
/// least `'data`.
///
/// Dropping a ScopedDir will not delete or clean it up, this is expected to occur through dropping
/// the `Scope` that created it.
pub struct ScopedDir<'data, 'dir> {
#[cfg(CONFIG_DEBUG_FS)]
entry: ManuallyDrop<Entry<'dir>>,
_phantom: PhantomData<fn(&'data ()) -> &'dir ()>,
}
impl<'data, 'dir> ScopedDir<'data, 'dir> {
/// Creates a subdirectory inside this `ScopedDir`.
///
/// The returned directory handle cannot outlive this one.
pub fn dir<'dir2>(&'dir2 self, name: &CStr) -> ScopedDir<'data, 'dir2> {
#[cfg(not(CONFIG_DEBUG_FS))]
let _ = name;
ScopedDir {
#[cfg(CONFIG_DEBUG_FS)]
entry: ManuallyDrop::new(Entry::dir(name, Some(&*self.entry))),
_phantom: PhantomData,
}
}
fn create_file<T: Sync>(&self, name: &CStr, data: &'data T, vtable: &'static FileOps<T>) {
#[cfg(CONFIG_DEBUG_FS)]
core::mem::forget(Entry::file(name, &self.entry, data, vtable));
}
/// Creates a read-only file in this directory.
///
/// The file's contents are produced by invoking [`Writer::write`].
///
/// This function does not produce an owning handle to the file. The created
/// file is removed when the [`Scope`] that this directory belongs
/// to is dropped.
pub fn read_only_file<T: Writer + Send + Sync + 'static>(&self, name: &CStr, data: &'data T) {
self.create_file(name, data, &T::FILE_OPS)
}
/// Creates a read-only file in this directory, with contents from a callback.
///
/// The file contents are generated by calling `f` with `data`.
///
///
/// `f` must be a function item or a non-capturing closure.
/// This is statically asserted and not a safety requirement.
///
/// This function does not produce an owning handle to the file. The created
/// file is removed when the [`Scope`] that this directory belongs
/// to is dropped.
pub fn read_callback_file<T, F>(&self, name: &CStr, data: &'data T, _f: &'static F)
where
T: Send + Sync + 'static,
F: Fn(&T, &mut fmt::Formatter<'_>) -> fmt::Result + Send + Sync,
{
let vtable = <FormatAdapter<T, F> as ReadFile<_>>::FILE_OPS.adapt();
self.create_file(name, data, vtable)
}
/// Creates a read-write file in this directory.
///
/// Reading the file uses the [`Writer`] implementation on `data`. Writing to the file uses
/// the [`Reader`] implementation on `data`.
///
/// This function does not produce an owning handle to the file. The created
/// file is removed when the [`Scope`] that this directory belongs
/// to is dropped.
pub fn read_write_file<T: Writer + Reader + Send + Sync + 'static>(
&self,
name: &CStr,
data: &'data T,
) {
let vtable = &<T as ReadWriteFile<_>>::FILE_OPS;
self.create_file(name, data, vtable)
}
/// Creates a read-write file in this directory, with logic from callbacks.
///
/// Reading from the file is handled by `f`. Writing to the file is handled by `w`.
///
/// `f` and `w` must be function items or non-capturing closures.
/// This is statically asserted and not a safety requirement.
///
/// This function does not produce an owning handle to the file. The created
/// file is removed when the [`Scope`] that this directory belongs
/// to is dropped.
pub fn read_write_callback_file<T, F, W>(
&self,
name: &CStr,
data: &'data T,
_f: &'static F,
_w: &'static W,
) where
T: Send + Sync + 'static,
F: Fn(&T, &mut fmt::Formatter<'_>) -> fmt::Result + Send + Sync,
W: Fn(&T, &mut UserSliceReader) -> Result + Send + Sync,
{
let vtable = <WritableAdapter<FormatAdapter<T, F>, W> as ReadWriteFile<_>>::FILE_OPS
.adapt()
.adapt();
self.create_file(name, data, vtable)
}
/// Creates a write-only file in this directory.
///
/// Writing to the file uses the [`Reader`] implementation on `data`.
///
/// This function does not produce an owning handle to the file. The created
/// file is removed when the [`Scope`] that this directory belongs
/// to is dropped.
pub fn write_only_file<T: Reader + Send + Sync + 'static>(&self, name: &CStr, data: &'data T) {
let vtable = &<T as WriteFile<_>>::FILE_OPS;
self.create_file(name, data, vtable)
}
/// Creates a write-only file in this directory, with write logic from a callback.
///
/// Writing to the file is handled by `w`.
///
/// `w` must be a function item or a non-capturing closure.
/// This is statically asserted and not a safety requirement.
///
/// This function does not produce an owning handle to the file. The created
/// file is removed when the [`Scope`] that this directory belongs
/// to is dropped.
pub fn write_only_callback_file<T, W>(&self, name: &CStr, data: &'data T, _w: &'static W)
where
T: Send + Sync + 'static,
W: Fn(&T, &mut UserSliceReader) -> Result + Send + Sync,
{
let vtable = &<WritableAdapter<NoWriter<T>, W> as WriteFile<_>>::FILE_OPS
.adapt()
.adapt();
self.create_file(name, data, vtable)
}
fn empty() -> Self {
ScopedDir {
#[cfg(CONFIG_DEBUG_FS)]
entry: ManuallyDrop::new(Entry::empty()),
_phantom: PhantomData,
}
}
#[cfg(CONFIG_DEBUG_FS)]
fn into_entry(self) -> Entry<'dir> {
ManuallyDrop::into_inner(self.entry)
}
#[cfg(not(CONFIG_DEBUG_FS))]
fn into_entry(self) {}
}
impl<'data> ScopedDir<'data, 'static> {
// This is safe, but intentionally not exported due to footgun status. A ScopedDir with no
// parent will never be released by default, and needs to have its entry extracted and used
// somewhere.
fn new(name: &CStr) -> ScopedDir<'data, 'static> {
ScopedDir {
#[cfg(CONFIG_DEBUG_FS)]
entry: ManuallyDrop::new(Entry::dir(name, None)),
_phantom: PhantomData,
}
}
}