2 files changed, 376 insertions, 2 deletions

diff --git a/rust/kernel/debugfs/file_ops.rs b/rust/kernel/debugfs/file_ops.rs
index 9ad5e3fa6f69..8a0442d6dd7a 100644
--- a/rust/kernel/debugfs/file_ops.rs
+++ b/rust/kernel/debugfs/file_ops.rs
@@ -1,9 +1,10 @@
 // SPDX-License-Identifier: GPL-2.0
 // Copyright (C) 2025 Google LLC.
 
-use super::{Reader, Writer};
+use super::{BinaryReader, BinaryWriter, Reader, Writer};
 use crate::debugfs::callback_adapters::Adapter;
 use crate::fmt;
+use crate::fs::file;
 use crate::prelude::*;
 use crate::seq_file::SeqFile;
 use crate::seq_print;
@@ -245,3 +246,140 @@ impl<T: Reader + Sync> WriteFile<T> for T {
         unsafe { FileOps::new(operations, 0o200) }
     };
 }
+
+extern "C" fn blob_read<T: BinaryWriter>(
+    file: *mut bindings::file,
+    buf: *mut c_char,
+    count: usize,
+    ppos: *mut bindings::loff_t,
+) -> isize {
+    // SAFETY:
+    // - `file` is a valid pointer to a `struct file`.
+    // - The type invariant of `FileOps` guarantees that `private_data` points to a valid `T`.
+    let this = unsafe { &*((*file).private_data.cast::<T>()) };
+
+    // SAFETY:
+    // - `ppos` is a valid `file::Offset` pointer.
+    // - We have exclusive access to `ppos`.
+    let pos: &mut file::Offset = unsafe { &mut *ppos };
+
+    let mut writer = UserSlice::new(UserPtr::from_ptr(buf.cast()), count).writer();
+
+    let ret = || -> Result<isize> {
+        let written = this.write_to_slice(&mut writer, pos)?;
+
+        Ok(written.try_into()?)
+    }();
+
+    match ret {
+        Ok(n) => n,
+        Err(e) => e.to_errno() as isize,
+    }
+}
+
+/// Representation of [`FileOps`] for read only binary files.
+pub(crate) trait BinaryReadFile<T> {
+    const FILE_OPS: FileOps<T>;
+}
+
+impl<T: BinaryWriter + Sync> BinaryReadFile<T> for T {
+    const FILE_OPS: FileOps<T> = {
+        let operations = bindings::file_operations {
+            read: Some(blob_read::<T>),
+            llseek: Some(bindings::default_llseek),
+            open: Some(bindings::simple_open),
+            // SAFETY: `file_operations` supports zeroes in all fields.
+            ..unsafe { core::mem::zeroed() }
+        };
+
+        // SAFETY:
+        // - The private data of `struct inode` does always contain a pointer to a valid `T`.
+        // - `simple_open()` stores the `struct inode`'s private data in the private data of the
+        //   corresponding `struct file`.
+        // - `blob_read()` re-creates a reference to `T` from the `struct file`'s private data.
+        // - `default_llseek()` does not access the `struct file`'s private data.
+        unsafe { FileOps::new(operations, 0o400) }
+    };
+}
+
+extern "C" fn blob_write<T: BinaryReader>(
+    file: *mut bindings::file,
+    buf: *const c_char,
+    count: usize,
+    ppos: *mut bindings::loff_t,
+) -> isize {
+    // SAFETY:
+    // - `file` is a valid pointer to a `struct file`.
+    // - The type invariant of `FileOps` guarantees that `private_data` points to a valid `T`.
+    let this = unsafe { &*((*file).private_data.cast::<T>()) };
+
+    // SAFETY:
+    // - `ppos` is a valid `file::Offset` pointer.
+    // - We have exclusive access to `ppos`.
+    let pos: &mut file::Offset = unsafe { &mut *ppos };
+
+    let mut reader = UserSlice::new(UserPtr::from_ptr(buf.cast_mut().cast()), count).reader();
+
+    let ret = || -> Result<isize> {
+        let read = this.read_from_slice(&mut reader, pos)?;
+
+        Ok(read.try_into()?)
+    }();
+
+    match ret {
+        Ok(n) => n,
+        Err(e) => e.to_errno() as isize,
+    }
+}
+
+/// Representation of [`FileOps`] for write only binary files.
+pub(crate) trait BinaryWriteFile<T> {
+    const FILE_OPS: FileOps<T>;
+}
+
+impl<T: BinaryReader + Sync> BinaryWriteFile<T> for T {
+    const FILE_OPS: FileOps<T> = {
+        let operations = bindings::file_operations {
+            write: Some(blob_write::<T>),
+            llseek: Some(bindings::default_llseek),
+            open: Some(bindings::simple_open),
+            // SAFETY: `file_operations` supports zeroes in all fields.
+            ..unsafe { core::mem::zeroed() }
+        };
+
+        // SAFETY:
+        // - The private data of `struct inode` does always contain a pointer to a valid `T`.
+        // - `simple_open()` stores the `struct inode`'s private data in the private data of the
+        //   corresponding `struct file`.
+        // - `blob_write()` re-creates a reference to `T` from the `struct file`'s private data.
+        // - `default_llseek()` does not access the `struct file`'s private data.
+        unsafe { FileOps::new(operations, 0o200) }
+    };
+}
+
+/// Representation of [`FileOps`] for read/write binary files.
+pub(crate) trait BinaryReadWriteFile<T> {
+    const FILE_OPS: FileOps<T>;
+}
+
+impl<T: BinaryWriter + BinaryReader + Sync> BinaryReadWriteFile<T> for T {
+    const FILE_OPS: FileOps<T> = {
+        let operations = bindings::file_operations {
+            read: Some(blob_read::<T>),
+            write: Some(blob_write::<T>),
+            llseek: Some(bindings::default_llseek),
+            open: Some(bindings::simple_open),
+            // SAFETY: `file_operations` supports zeroes in all fields.
+            ..unsafe { core::mem::zeroed() }
+        };
+
+        // SAFETY:
+        // - The private data of `struct inode` does always contain a pointer to a valid `T`.
+        // - `simple_open()` stores the `struct inode`'s private data in the private data of the
+        //   corresponding `struct file`.
+        // - `blob_read()` re-creates a reference to `T` from the `struct file`'s private data.
+        // - `blob_write()` re-creates a reference to `T` from the `struct file`'s private data.
+        // - `default_llseek()` does not access the `struct file`'s private data.
+        unsafe { FileOps::new(operations, 0o600) }
+    };
+}
diff --git a/rust/kernel/debugfs/traits.rs b/rust/kernel/debugfs/traits.rs
index e8a8a98f18dc..3eee60463fd5 100644
--- a/rust/kernel/debugfs/traits.rs
+++ b/rust/kernel/debugfs/traits.rs
@@ -3,11 +3,16 @@
 
 //! Traits for rendering or updating values exported to DebugFS.
 
+use crate::alloc::Allocator;
 use crate::fmt;
+use crate::fs::file;
 use crate::prelude::*;
 use crate::sync::atomic::{Atomic, AtomicBasicOps, AtomicType, Relaxed};
+use crate::sync::Arc;
 use crate::sync::Mutex;
-use crate::uaccess::UserSliceReader;
+use crate::transmute::{AsBytes, FromBytes};
+use crate::uaccess::{UserSliceReader, UserSliceWriter};
+use core::ops::{Deref, DerefMut};
 use core::str::FromStr;
 
 /// A trait for types that can be written into a string.
@@ -36,6 +41,110 @@ impl<T: fmt::Debug> Writer for T {
     }
 }
 
+/// Trait for types that can be written out as binary.
+pub trait BinaryWriter {
+    /// Writes the binary form of `self` into `writer`.
+    ///
+    /// `offset` is the requested offset into the binary representation of `self`.
+    ///
+    /// On success, returns the number of bytes written in to `writer`.
+    fn write_to_slice(
+        &self,
+        writer: &mut UserSliceWriter,
+        offset: &mut file::Offset,
+    ) -> Result<usize>;
+}
+
+// Base implementation for any `T: AsBytes`.
+impl<T: AsBytes> BinaryWriter for T {
+    fn write_to_slice(
+        &self,
+        writer: &mut UserSliceWriter,
+        offset: &mut file::Offset,
+    ) -> Result<usize> {
+        writer.write_slice_file(self.as_bytes(), offset)
+    }
+}
+
+// Delegate for `Mutex<T>`: Support a `T` with an outer mutex.
+impl<T: BinaryWriter> BinaryWriter for Mutex<T> {
+    fn write_to_slice(
+        &self,
+        writer: &mut UserSliceWriter,
+        offset: &mut file::Offset,
+    ) -> Result<usize> {
+        let guard = self.lock();
+
+        guard.write_to_slice(writer, offset)
+    }
+}
+
+// Delegate for `Box<T, A>`: Support a `Box<T, A>` with no lock or an inner lock.
+impl<T, A> BinaryWriter for Box<T, A>
+where
+    T: BinaryWriter,
+    A: Allocator,
+{
+    fn write_to_slice(
+        &self,
+        writer: &mut UserSliceWriter,
+        offset: &mut file::Offset,
+    ) -> Result<usize> {
+        self.deref().write_to_slice(writer, offset)
+    }
+}
+
+// Delegate for `Pin<Box<T, A>>`: Support a `Pin<Box<T, A>>` with no lock or an inner lock.
+impl<T, A> BinaryWriter for Pin<Box<T, A>>
+where
+    T: BinaryWriter,
+    A: Allocator,
+{
+    fn write_to_slice(
+        &self,
+        writer: &mut UserSliceWriter,
+        offset: &mut file::Offset,
+    ) -> Result<usize> {
+        self.deref().write_to_slice(writer, offset)
+    }
+}
+
+// Delegate for `Arc<T>`: Support a `Arc<T>` with no lock or an inner lock.
+impl<T> BinaryWriter for Arc<T>
+where
+    T: BinaryWriter,
+{
+    fn write_to_slice(
+        &self,
+        writer: &mut UserSliceWriter,
+        offset: &mut file::Offset,
+    ) -> Result<usize> {
+        self.deref().write_to_slice(writer, offset)
+    }
+}
+
+// Delegate for `Vec<T, A>`.
+impl<T, A> BinaryWriter for Vec<T, A>
+where
+    T: AsBytes,
+    A: Allocator,
+{
+    fn write_to_slice(
+        &self,
+        writer: &mut UserSliceWriter,
+        offset: &mut file::Offset,
+    ) -> Result<usize> {
+        let slice = self.as_slice();
+
+        // SAFETY: `T: AsBytes` allows us to treat `&[T]` as `&[u8]`.
+        let buffer = unsafe {
+            core::slice::from_raw_parts(slice.as_ptr().cast(), core::mem::size_of_val(slice))
+        };
+
+        writer.write_slice_file(buffer, offset)
+    }
+}
+
 /// A trait for types that can be updated from a user slice.
 ///
 /// This works similarly to `FromStr`, but operates on a `UserSliceReader` rather than a &str.
@@ -81,3 +190,130 @@ where
         Ok(())
     }
 }
+
+/// Trait for types that can be constructed from a binary representation.
+///
+/// See also [`BinaryReader`] for interior mutability.
+pub trait BinaryReaderMut {
+    /// Reads the binary form of `self` from `reader`.
+    ///
+    /// Same as [`BinaryReader::read_from_slice`], but takes a mutable reference.
+    ///
+    /// `offset` is the requested offset into the binary representation of `self`.
+    ///
+    /// On success, returns the number of bytes read from `reader`.
+    fn read_from_slice_mut(
+        &mut self,
+        reader: &mut UserSliceReader,
+        offset: &mut file::Offset,
+    ) -> Result<usize>;
+}
+
+// Base implementation for any `T: AsBytes + FromBytes`.
+impl<T: AsBytes + FromBytes> BinaryReaderMut for T {
+    fn read_from_slice_mut(
+        &mut self,
+        reader: &mut UserSliceReader,
+        offset: &mut file::Offset,
+    ) -> Result<usize> {
+        reader.read_slice_file(self.as_bytes_mut(), offset)
+    }
+}
+
+// Delegate for `Box<T, A>`: Support a `Box<T, A>` with an outer lock.
+impl<T: ?Sized + BinaryReaderMut, A: Allocator> BinaryReaderMut for Box<T, A> {
+    fn read_from_slice_mut(
+        &mut self,
+        reader: &mut UserSliceReader,
+        offset: &mut file::Offset,
+    ) -> Result<usize> {
+        self.deref_mut().read_from_slice_mut(reader, offset)
+    }
+}
+
+// Delegate for `Vec<T, A>`: Support a `Vec<T, A>` with an outer lock.
+impl<T, A> BinaryReaderMut for Vec<T, A>
+where
+    T: AsBytes + FromBytes,
+    A: Allocator,
+{
+    fn read_from_slice_mut(
+        &mut self,
+        reader: &mut UserSliceReader,
+        offset: &mut file::Offset,
+    ) -> Result<usize> {
+        let slice = self.as_mut_slice();
+
+        // SAFETY: `T: AsBytes + FromBytes` allows us to treat `&mut [T]` as `&mut [u8]`.
+        let buffer = unsafe {
+            core::slice::from_raw_parts_mut(
+                slice.as_mut_ptr().cast(),
+                core::mem::size_of_val(slice),
+            )
+        };
+
+        reader.read_slice_file(buffer, offset)
+    }
+}
+
+/// Trait for types that can be constructed from a binary representation.
+///
+/// See also [`BinaryReaderMut`] for the mutable version.
+pub trait BinaryReader {
+    /// Reads the binary form of `self` from `reader`.
+    ///
+    /// `offset` is the requested offset into the binary representation of `self`.
+    ///
+    /// On success, returns the number of bytes read from `reader`.
+    fn read_from_slice(
+        &self,
+        reader: &mut UserSliceReader,
+        offset: &mut file::Offset,
+    ) -> Result<usize>;
+}
+
+// Delegate for `Mutex<T>`: Support a `T` with an outer `Mutex`.
+impl<T: BinaryReaderMut + Unpin> BinaryReader for Mutex<T> {
+    fn read_from_slice(
+        &self,
+        reader: &mut UserSliceReader,
+        offset: &mut file::Offset,
+    ) -> Result<usize> {
+        let mut this = self.lock();
+
+        this.read_from_slice_mut(reader, offset)
+    }
+}
+
+// Delegate for `Box<T, A>`: Support a `Box<T, A>` with an inner lock.
+impl<T: ?Sized + BinaryReader, A: Allocator> BinaryReader for Box<T, A> {
+    fn read_from_slice(
+        &self,
+        reader: &mut UserSliceReader,
+        offset: &mut file::Offset,
+    ) -> Result<usize> {
+        self.deref().read_from_slice(reader, offset)
+    }
+}
+
+// Delegate for `Pin<Box<T, A>>`: Support a `Pin<Box<T, A>>` with an inner lock.
+impl<T: ?Sized + BinaryReader, A: Allocator> BinaryReader for Pin<Box<T, A>> {
+    fn read_from_slice(
+        &self,
+        reader: &mut UserSliceReader,
+        offset: &mut file::Offset,
+    ) -> Result<usize> {
+        self.deref().read_from_slice(reader, offset)
+    }
+}
+
+// Delegate for `Arc<T>`: Support an `Arc<T>` with an inner lock.
+impl<T: ?Sized + BinaryReader> BinaryReader for Arc<T> {
+    fn read_from_slice(
+        &self,
+        reader: &mut UserSliceReader,
+        offset: &mut file::Offset,
+    ) -> Result<usize> {
+        self.deref().read_from_slice(reader, offset)
+    }
+}