[RFC PATCH v3 20/22] rust: add support for file system parameters
From: Ariel Miculas
Date: Thu May 16 2024 - 15:06:23 EST
From: Wedson Almeida Filho <wedsonaf@xxxxxxxxxx>
This allows file system contexts to be further initialised with
parameters from userspace before a fs is mounted or reconfigured.
Signed-off-by: Wedson Almeida Filho <wedsonaf@xxxxxxxxxx>
[
Changes made:
* adapt for upstream
* replace UnsafeCell with Opaque,
* replace from_kernel_result with from_result
* replace Type with FileSystem
* add Context in FileSystem from [1]
* add the EmptyContext from [1]
* add the free_callback from [2]
* add count_paren_items from [3]
* add PAGE_SIZE constant from [4]
* initialize the Context in init_fs_context_callback
* get the data Context in fill_super_callback and pass it to super_params
* avoid freeing s_fs_info in free_callback, it's already freed in
kill_sb_callback
[1] https://github.com/wedsonaf/linux/commit/6633c50b345f388a07b4c551f752efe34c15c089
[2] https://github.com/wedsonaf/linux/commit/3c3ccce85af9aae9dfc0e17e2331674da520177c
[3] https://github.com/wedsonaf/linux/commit/c3f395b1b0126b4db7eb833bdee769212c8c79d8
[4] https://github.com/wedsonaf/linux/commit/4021d947dea69506d11b148486e1565961a85e53
]
Signed-off-by: Ariel Miculas <amiculas@xxxxxxxxx>
---
fs/puzzlefs/puzzlefs.rs | 1 +
rust/bindings/bindings_helper.h | 1 +
rust/kernel/fs.rs | 212 +++++++++++-
rust/kernel/fs/param.rs | 576 ++++++++++++++++++++++++++++++++
rust/kernel/lib.rs | 7 +
samples/rust/rust_rofs.rs | 32 +-
6 files changed, 821 insertions(+), 8 deletions(-)
create mode 100644 rust/kernel/fs/param.rs
diff --git a/fs/puzzlefs/puzzlefs.rs b/fs/puzzlefs/puzzlefs.rs
index 9622ea71eda0..f4e94568c9cc 100644
--- a/fs/puzzlefs/puzzlefs.rs
+++ b/fs/puzzlefs/puzzlefs.rs
@@ -103,6 +103,7 @@ impl fs::FileSystem for PuzzleFsModule {
const NAME: &'static CStr = c_str!("puzzlefs");
fn fill_super(
+ _data: (),
sb: &mut sb::SuperBlock<Self, sb::New>,
_: Option<inode::Mapper>,
) -> Result<Box<PuzzleFS>> {
diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
index 0491bb05270c..3f18e5abcc5c 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -27,6 +27,7 @@
#include <linux/wait.h>
#include <linux/workqueue.h>
#include <linux/xattr.h>
+#include <linux/fs_parser.h>
/* `bindgen` gets confused at certain things. */
const size_t RUST_CONST_HELPER_ARCH_SLAB_MINALIGN = ARCH_SLAB_MINALIGN;
diff --git a/rust/kernel/fs.rs b/rust/kernel/fs.rs
index b7a654546d23..9ca653f64388 100644
--- a/rust/kernel/fs.rs
+++ b/rust/kernel/fs.rs
@@ -12,7 +12,7 @@
use core::{ffi, marker::PhantomData, mem::size_of, mem::ManuallyDrop, pin::Pin, ptr};
use dentry::DEntry;
use inode::INode;
-use macros::{pin_data, pinned_drop};
+use macros::{pin_data, pinned_drop, vtable};
use sb::SuperBlock;
pub mod address_space;
@@ -20,6 +20,7 @@
pub mod file;
pub mod inode;
pub mod iomap;
+pub mod param;
pub mod sb;
/// The offset of a file in a file system.
@@ -59,11 +60,52 @@ pub mod mode {
pub const S_IFSOCK: u16 = bindings::S_IFSOCK as u16;
}
+/// A file system context.
+///
+/// It is used to gather configuration to then mount or reconfigure a file system.
+#[vtable]
+pub trait Context<T: FileSystem + ?Sized> {
+ /// Type of the data associated with the context.
+ type Data: ForeignOwnable + Send + Sync + 'static;
+
+ /// The typed file system parameters.
+ ///
+ /// Users are encouraged to define it using the [`crate::define_fs_params`] macro.
+ const PARAMS: param::SpecTable<'static, Self::Data> = param::SpecTable::empty();
+
+ /// Creates a new context.
+ fn try_new() -> Result<Self::Data>;
+
+ /// Parses a parameter that wasn't specified in [`Self::PARAMS`].
+ fn parse_unknown_param(
+ _data: &mut <Self::Data as ForeignOwnable>::BorrowedMut<'_>,
+ _name: &CStr,
+ _value: param::Value<'_>,
+ ) -> Result {
+ Err(ENOPARAM)
+ }
+
+ /// Parses the whole parameter block, potentially skipping regular handling for parts of it.
+ ///
+ /// The return value is the portion of the input buffer for which the regular handling
+ /// (involving [`Self::PARAMS`] and [`Self::parse_unknown_param`]) will still be carried out.
+ /// If it's `None`, the regular handling is not performed at all.
+ fn parse_monolithic<'a>(
+ _data: &mut <Self::Data as ForeignOwnable>::BorrowedMut<'_>,
+ _buf: Option<&'a mut [u8]>,
+ ) -> Result<Option<&'a mut [u8]>> {
+ Ok(None)
+ }
+}
+
/// Maximum size of an inode.
pub const MAX_LFS_FILESIZE: Offset = bindings::MAX_LFS_FILESIZE;
/// A file system type.
pub trait FileSystem {
+ /// The context used to build fs configuration before it is mounted or reconfigured.
+ type Context: Context<Self> + ?Sized = EmptyContext;
+
/// Data associated with each file system instance (super-block).
type Data: ForeignOwnable + Send + Sync;
@@ -84,6 +126,7 @@ pub trait FileSystem {
/// Initialises the new superblock and returns the data to attach to it.
fn fill_super(
+ data: <Self::Context as Context<Self>>::Data,
sb: &mut SuperBlock<Self, sb::New>,
mapper: Option<inode::Mapper>,
) -> Result<Self::Data>;
@@ -143,7 +186,11 @@ impl FileSystem for UnspecifiedFS {
type INodeData = ();
const NAME: &'static CStr = crate::c_str!("unspecified");
const IS_UNSPECIFIED: bool = true;
- fn fill_super(_: &mut SuperBlock<Self, sb::New>, _: Option<inode::Mapper>) -> Result {
+ fn fill_super(
+ _: <Self::Context as Context<Self>>::Data,
+ _: &mut SuperBlock<Self, sb::New>,
+ _: Option<inode::Mapper>,
+ ) -> Result<()> {
Err(ENOTSUPP)
}
@@ -199,9 +246,11 @@ pub fn new<T: FileSystem + ?Sized>(module: &'static ThisModule) -> impl PinInit<
fc_ptr: *mut bindings::fs_context,
) -> ffi::c_int {
from_result(|| {
+ let data = T::Context::try_new()?;
// SAFETY: The C callback API guarantees that `fc_ptr` is valid.
let fc = unsafe { &mut *fc_ptr };
fc.ops = &Tables::<T>::CONTEXT;
+ fc.fs_private = data.into_foreign() as _;
Ok(0)
})
}
@@ -242,14 +291,32 @@ fn drop(self: Pin<&mut Self>) {
}
}
+/// An empty file system context.
+///
+/// That is, one that doesn't take any arguments and doesn't hold any state. It is a convenience
+/// type for file systems that don't need context for mounting/reconfiguring.
+pub struct EmptyContext;
+
+#[vtable]
+impl<T: FileSystem + ?Sized> Context<T> for EmptyContext {
+ type Data = ();
+ fn try_new() -> Result {
+ Ok(())
+ }
+}
+
struct Tables<T: FileSystem + ?Sized>(T);
impl<T: FileSystem + ?Sized> Tables<T> {
const CONTEXT: bindings::fs_context_operations = bindings::fs_context_operations {
- free: None,
- parse_param: None,
+ free: Some(Self::free_callback),
+ parse_param: Some(Self::parse_param_callback),
get_tree: Some(Self::get_tree_callback),
reconfigure: None,
- parse_monolithic: None,
+ parse_monolithic: if <T::Context as Context<T>>::HAS_PARSE_MONOLITHIC {
+ Some(Self::parse_monolithic_callback)
+ } else {
+ None
+ },
dup: None,
};
@@ -268,9 +335,73 @@ impl<T: FileSystem + ?Sized> Tables<T> {
}
}
+ unsafe extern "C" fn free_callback(fc: *mut bindings::fs_context) {
+ // SAFETY: The callback contract guarantees that `fc` is valid.
+ let fc = unsafe { &*fc };
+
+ let ptr = fc.fs_private;
+ if !ptr.is_null() {
+ // SAFETY: `fs_private` was initialised with the result of a `to_pointer` call in
+ // `init_fs_context_callback`, so it's ok to call `from_foreign` here.
+ unsafe { <T::Context as Context<T>>::Data::from_foreign(ptr) };
+ }
+ }
+
+ unsafe extern "C" fn parse_param_callback(
+ fc: *mut bindings::fs_context,
+ param: *mut bindings::fs_parameter,
+ ) -> core::ffi::c_int {
+ from_result(|| {
+ // SAFETY: The callback contract guarantees that `fc` is valid.
+ let ptr = unsafe { (*fc).fs_private };
+
+ // SAFETY: The value of `ptr` (coming from `fs_private` was initialised in
+ // `init_fs_context_callback` to the result of an `into_foreign` call. Since the
+ // context is valid, `from_foreign` wasn't called yet, so `ptr` is valid. Additionally,
+ // the callback contract guarantees that callbacks are serialised, so it is ok to
+ // mutably reference it.
+ let mut data =
+ unsafe { <<T::Context as Context<T>>::Data as ForeignOwnable>::borrow_mut(ptr) };
+ let mut result = bindings::fs_parse_result::default();
+ // SAFETY: All parameters are valid at least for the duration of the call.
+ let opt =
+ unsafe { bindings::fs_parse(fc, T::Context::PARAMS.first, param, &mut result) };
+
+ // SAFETY: The callback contract guarantees that `param` is valid for the duration of
+ // the callback.
+ let param = unsafe { &*param };
+ if opt >= 0 {
+ let opt = opt as usize;
+ if opt >= T::Context::PARAMS.handlers.len() {
+ return Err(EINVAL);
+ }
+ T::Context::PARAMS.handlers[opt].handle_param(&mut data, param, &result)?;
+ return Ok(0);
+ }
+
+ if opt != ENOPARAM.to_errno() {
+ return Err(Error::from_errno(opt));
+ }
+
+ if !T::Context::HAS_PARSE_UNKNOWN_PARAM {
+ return Err(ENOPARAM);
+ }
+
+ let val = param::Value::from_fs_parameter(param);
+ // SAFETY: The callback contract guarantees the parameter key to be valid and last at
+ // least the duration of the callback.
+ T::Context::parse_unknown_param(
+ &mut data,
+ unsafe { CStr::from_char_ptr(param.key) },
+ val,
+ )?;
+ Ok(0)
+ })
+ }
+
unsafe extern "C" fn fill_super_callback(
sb_ptr: *mut bindings::super_block,
- _fc: *mut bindings::fs_context,
+ fc: *mut bindings::fs_context,
) -> ffi::c_int {
from_result(|| {
// SAFETY: The callback contract guarantees that `sb_ptr` is a unique pointer to a
@@ -280,6 +411,20 @@ impl<T: FileSystem + ?Sized> Tables<T> {
// SAFETY: The callback contract guarantees that `sb_ptr`, from which `new_sb` is
// derived, is valid for write.
let sb = unsafe { &mut *new_sb.0.get() };
+
+ // SAFETY: The callback contract guarantees that `fc` is valid. It also guarantees that
+ // the callbacks are serialised for a given `fc`, so it is safe to mutably dereference
+ // it.
+ let fc = unsafe { &mut *fc };
+ let ptr = core::mem::replace(&mut fc.fs_private, ptr::null_mut());
+
+ // SAFETY: The value of `ptr` (coming from `fs_private` was initialised in
+ // `init_fs_context_callback` to the result of an `into_foreign` call. The context is
+ // being used to initialise a superblock, so we took over `ptr` (`fs_private` is set to
+ // null now) and call `from_foreign` below.
+ let data =
+ unsafe { <<T::Context as Context<T>>::Data as ForeignOwnable>::from_foreign(ptr) };
+
sb.s_op = &Tables::<T>::SUPER_BLOCK;
sb.s_xattr = &Tables::<T>::XATTR_HANDLERS[0];
sb.s_flags |= bindings::SB_RDONLY;
@@ -291,7 +436,7 @@ impl<T: FileSystem + ?Sized> Tables<T> {
None
};
- let data = T::fill_super(new_sb, mapper)?;
+ let data = T::fill_super(data, new_sb, mapper)?;
// N.B.: Even on failure, `kill_sb` is called and frees the data.
sb.s_fs_info = data.into_foreign().cast_mut();
@@ -317,6 +462,41 @@ impl<T: FileSystem + ?Sized> Tables<T> {
})
}
+ unsafe extern "C" fn parse_monolithic_callback(
+ fc: *mut bindings::fs_context,
+ buf: *mut core::ffi::c_void,
+ ) -> core::ffi::c_int {
+ from_result(|| {
+ // SAFETY: The callback contract guarantees that `fc` is valid.
+ let ptr = unsafe { (*fc).fs_private };
+
+ // SAFETY: The value of `ptr` (coming from `fs_private` was initialised in
+ // `init_fs_context_callback` to the result of an `into_pointer` call. Since the
+ // context is valid, `from_pointer` wasn't called yet, so `ptr` is valid. Additionally,
+ // the callback contract guarantees that callbacks are serialised, so it is ok to
+ // mutably reference it.
+ let mut data =
+ unsafe { <<T::Context as Context<T>>::Data as ForeignOwnable>::borrow_mut(ptr) };
+ let page = if buf.is_null() {
+ None
+ } else {
+ // SAFETY: This callback is called to handle the `mount` syscall, which takes a
+ // page-sized buffer as data.
+ Some(unsafe { &mut *ptr::slice_from_raw_parts_mut(buf.cast(), crate::PAGE_SIZE) })
+ };
+ let regular = T::Context::parse_monolithic(&mut data, page)?;
+ if let Some(buf) = regular {
+ // SAFETY: Both `fc` and `buf` are guaranteed to be valid; the former because the
+ // callback is still ongoing and the latter because its lifefime is tied to that of
+ // `page`, which is also valid for the duration of the callback.
+ to_result(unsafe {
+ bindings::generic_parse_monolithic(fc, buf.as_mut_ptr().cast())
+ })?;
+ }
+ Ok(0)
+ })
+ }
+
const SUPER_BLOCK: bindings::super_operations = bindings::super_operations {
alloc_inode: if size_of::<T::INodeData>() != 0 {
Some(INode::<T>::alloc_inode_callback)
@@ -490,3 +670,21 @@ macro_rules! module_fs {
}
}
}
+
+/// Wraps the kernel's `struct filename`.
+#[repr(transparent)]
+pub struct Filename(pub(crate) Opaque<bindings::filename>);
+
+impl Filename {
+ /// Creates a reference to a [`Filename`] from a valid pointer.
+ ///
+ /// # Safety
+ ///
+ /// The caller must ensure that `ptr` is valid and remains valid for the lifetime of the
+ /// returned [`Filename`] instance.
+ pub(crate) unsafe fn from_ptr<'a>(ptr: *const bindings::filename) -> &'a Filename {
+ // SAFETY: The safety requirements guarantee the validity of the dereference, while the
+ // `Filename` type being transparent makes the cast ok.
+ unsafe { &*ptr.cast() }
+ }
+}
diff --git a/rust/kernel/fs/param.rs b/rust/kernel/fs/param.rs
new file mode 100644
index 000000000000..590fdaaab0ad
--- /dev/null
+++ b/rust/kernel/fs/param.rs
@@ -0,0 +1,576 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! File system parameters and parsing them.
+//!
+//! C headers: [`include/linux/fs_parser.h`](../../../../../include/linux/fs_parser.h)
+
+use crate::types::ForeignOwnable;
+use crate::{bindings, error::Result, file, fs, str::CStr};
+use core::{marker::PhantomData, ptr};
+
+/// The value of a file system parameter.
+pub enum Value<'a> {
+ /// The value is undefined.
+ Undefined,
+
+ /// There is no value, but parameter itself is a flag.
+ Flag,
+
+ /// The value is the given string.
+ String(&'a CStr),
+
+ /// The value is the given binary blob.
+ Blob(&'a mut [u8]),
+
+ /// The value is the given file.
+ File(&'a file::File),
+
+ /// The value is the given filename and the given directory file descriptor (which may be
+ /// `AT_FDCWD`, to indicate the current directory).
+ Filename(&'a fs::Filename, i32),
+}
+
+impl<'a> Value<'a> {
+ pub(super) fn from_fs_parameter(p: &'a bindings::fs_parameter) -> Self {
+ match p.type_() {
+ bindings::fs_value_type_fs_value_is_string => {
+ // SAFETY: `type_` is string, so it is ok to use the union field. Additionally, it
+ // is guaranteed to be valid while `p` is valid.
+ Self::String(unsafe { CStr::from_char_ptr(p.__bindgen_anon_1.string) })
+ }
+ bindings::fs_value_type_fs_value_is_flag => Self::Flag,
+ bindings::fs_value_type_fs_value_is_blob => {
+ // SAFETY: `type_` is blob, so it is ok to use the union field and size.
+ // Additionally, it is guaranteed to be valid while `p` is valid.
+ let slice = unsafe {
+ &mut *ptr::slice_from_raw_parts_mut(p.__bindgen_anon_1.blob.cast(), p.size)
+ };
+ Self::Blob(slice)
+ }
+ bindings::fs_value_type_fs_value_is_file => {
+ // SAFETY: `type_` is file, so it is ok to use the union field. Additionally, it is
+ // guaranteed to be valid while `p` is valid.
+ let file_ptr = unsafe { p.__bindgen_anon_1.file };
+ if file_ptr.is_null() {
+ Self::Undefined
+ } else {
+ // SAFETY: `file_ptr` is non-null and guaranteed to be valid while `p` is.
+ Self::File(unsafe { file::File::from_ptr(file_ptr) })
+ }
+ }
+ bindings::fs_value_type_fs_value_is_filename => {
+ // SAFETY: `type_` is filename, so it is ok to use the union field. Additionally,
+ // it is guaranteed to be valid while `p` is valid.
+ let filename_ptr = unsafe { p.__bindgen_anon_1.name };
+ if filename_ptr.is_null() {
+ Self::Undefined
+ } else {
+ // SAFETY: `filename_ptr` is non-null and guaranteed to be valid while `p` is.
+ Self::Filename(unsafe { fs::Filename::from_ptr(filename_ptr) }, p.dirfd)
+ }
+ }
+ _ => Self::Undefined,
+ }
+ }
+}
+
+/// A specification of a file system parameter.
+pub struct Spec {
+ name: &'static CStr,
+ flags: u16,
+ type_: bindings::fs_param_type,
+ extra: *const core::ffi::c_void,
+}
+
+const DEFAULT: Spec = Spec {
+ name: crate::c_str!(""),
+ flags: 0,
+ type_: None,
+ extra: core::ptr::null(),
+};
+
+macro_rules! define_param_type {
+ ($name:ident, $fntype:ty, $spec:expr, |$param:ident, $result:ident| $value:expr) => {
+ /// Module to support `$name` parameter types.
+ pub mod $name {
+ use super::*;
+
+ #[doc(hidden)]
+ pub const fn spec(name: &'static CStr) -> Spec {
+ const GIVEN: Spec = $spec;
+ Spec { name, ..GIVEN }
+ }
+
+ #[doc(hidden)]
+ pub const fn handler<S: ForeignOwnable>(
+ setfn: fn(&mut <S as ForeignOwnable>::BorrowedMut<'_>, $fntype) -> Result,
+ ) -> impl Handler<S> {
+ let c =
+ move |s: &mut <S as ForeignOwnable>::BorrowedMut<'_>,
+ $param: &bindings::fs_parameter,
+ $result: &bindings::fs_parse_result| { setfn(s, $value) };
+ ConcreteHandler {
+ setfn: c,
+ _p: PhantomData,
+ }
+ }
+ }
+ };
+}
+
+// SAFETY: This is only called when the parse result is a boolean, so it is ok to access to union
+// field.
+define_param_type!(flag, bool, Spec { ..DEFAULT }, |_p, r| unsafe {
+ r.__bindgen_anon_1.boolean
+});
+
+define_param_type!(
+ flag_no,
+ bool,
+ Spec {
+ flags: bindings::fs_param_neg_with_no as _,
+ ..DEFAULT
+ },
+ // SAFETY: This is only called when the parse result is a boolean, so it is ok to access to
+ // union field.
+ |_p, r| unsafe { r.__bindgen_anon_1.boolean }
+);
+
+define_param_type!(
+ bool,
+ bool,
+ Spec {
+ type_: Some(bindings::fs_param_is_bool),
+ ..DEFAULT
+ },
+ // SAFETY: This is only called when the parse result is a boolean, so it is ok to access to
+ // union field.
+ |_p, r| unsafe { r.__bindgen_anon_1.boolean }
+);
+
+define_param_type!(
+ u32,
+ u32,
+ Spec {
+ type_: Some(bindings::fs_param_is_u32),
+ ..DEFAULT
+ },
+ // SAFETY: This is only called when the parse result is a u32, so it is ok to access to union
+ // field.
+ |_p, r| unsafe { r.__bindgen_anon_1.uint_32 }
+);
+
+define_param_type!(
+ u32oct,
+ u32,
+ Spec {
+ type_: Some(bindings::fs_param_is_u32),
+ extra: 8 as _,
+ ..DEFAULT
+ },
+ // SAFETY: This is only called when the parse result is a u32, so it is ok to access to union
+ // field.
+ |_p, r| unsafe { r.__bindgen_anon_1.uint_32 }
+);
+
+define_param_type!(
+ u32hex,
+ u32,
+ Spec {
+ type_: Some(bindings::fs_param_is_u32),
+ extra: 16 as _,
+ ..DEFAULT
+ },
+ // SAFETY: This is only called when the parse result is a u32, so it is ok to access to union
+ // field.
+ |_p, r| unsafe { r.__bindgen_anon_1.uint_32 }
+);
+
+define_param_type!(
+ s32,
+ i32,
+ Spec {
+ type_: Some(bindings::fs_param_is_s32),
+ ..DEFAULT
+ },
+ // SAFETY: This is only called when the parse result is an i32, so it is ok to access to union
+ // field.
+ |_p, r| unsafe { r.__bindgen_anon_1.int_32 }
+);
+
+define_param_type!(
+ u64,
+ u64,
+ Spec {
+ type_: Some(bindings::fs_param_is_u64),
+ extra: 16 as _,
+ ..DEFAULT
+ },
+ // SAFETY: This is only called when the parse result is a u32, so it is ok to access to union
+ // field.
+ |_p, r| unsafe { r.__bindgen_anon_1.uint_64 }
+);
+
+define_param_type!(
+ string,
+ &CStr,
+ Spec {
+ type_: Some(bindings::fs_param_is_string),
+ ..DEFAULT
+ },
+ // SAFETY: This is only called when the parse result is a string, so it is ok to access to
+ // union field.
+ |p, _r| unsafe { CStr::from_char_ptr(p.__bindgen_anon_1.string) }
+);
+
+/// Module to support `enum` parameter types.
+pub mod enum_ {
+ use super::*;
+
+ #[doc(hidden)]
+ pub const fn spec(name: &'static CStr, options: ConstantTable<'static>) -> Spec {
+ Spec {
+ name,
+ type_: Some(bindings::fs_param_is_enum),
+ extra: options.first as *const _ as _,
+ ..DEFAULT
+ }
+ }
+
+ #[doc(hidden)]
+ pub const fn handler<S: ForeignOwnable>(
+ setfn: fn(&mut <S as ForeignOwnable>::BorrowedMut<'_>, u32) -> Result,
+ ) -> impl Handler<S> {
+ let c = move |s: &mut <S as ForeignOwnable>::BorrowedMut<'_>,
+ _p: &bindings::fs_parameter,
+ r: &bindings::fs_parse_result| {
+ // SAFETY: This is only called when the parse result is an enum, so it is ok to access
+ // to union field.
+ setfn(s, unsafe { r.__bindgen_anon_1.uint_32 })
+ };
+ ConcreteHandler {
+ setfn: c,
+ _p: PhantomData,
+ }
+ }
+}
+
+const ZERO_SPEC: bindings::fs_parameter_spec = bindings::fs_parameter_spec {
+ name: core::ptr::null(),
+ type_: None,
+ opt: 0,
+ flags: 0,
+ data: core::ptr::null(),
+};
+
+/// A zero-terminated parameter spec array, followed by handlers.
+#[repr(C)]
+pub struct SpecArray<const N: usize, S: 'static> {
+ specs: [bindings::fs_parameter_spec; N],
+ sentinel: bindings::fs_parameter_spec,
+ handlers: [&'static dyn Handler<S>; N],
+}
+
+impl<const N: usize, S: 'static> SpecArray<N, S> {
+ /// Creates a new spec array.
+ ///
+ /// Users are encouraged to use the [`define_fs_params`] macro to define the
+ /// [`super::Context::PARAMS`] constant.
+ ///
+ /// # Safety
+ ///
+ /// The type of the elements in `handlers` must be compatible with the types in specs. For
+ /// example, if `specs` declares that the i-th element is a bool then the i-th handler
+ /// should be for a bool.
+ pub const unsafe fn new(specs: [Spec; N], handlers: [&'static dyn Handler<S>; N]) -> Self {
+ let mut array = Self {
+ specs: [ZERO_SPEC; N],
+ sentinel: ZERO_SPEC,
+ handlers,
+ };
+ let mut i = 0usize;
+ while i < N {
+ array.specs[i] = bindings::fs_parameter_spec {
+ name: specs[i].name.as_char_ptr(),
+ type_: specs[i].type_,
+ opt: i as _,
+ flags: specs[i].flags,
+ data: specs[i].extra,
+ };
+ i += 1;
+ }
+ array
+ }
+
+ /// Returns a [`SpecTable`] backed by `self`.
+ ///
+ /// This is used to essentially erase the array size.
+ pub const fn as_table(&self) -> SpecTable<'_, S> {
+ SpecTable {
+ first: &self.specs[0],
+ handlers: &self.handlers,
+ _p: PhantomData,
+ }
+ }
+}
+
+/// A parameter spec table.
+///
+/// The table is guaranteed to be zero-terminated.
+///
+/// Users are encouraged to use the [`define_fs_params`] macro to define the
+/// [`super::Context::PARAMS`] constant.
+pub struct SpecTable<'a, S: 'static> {
+ pub(super) first: &'a bindings::fs_parameter_spec,
+ pub(super) handlers: &'a [&'static dyn Handler<S>],
+ _p: PhantomData<S>,
+}
+
+impl<S> SpecTable<'static, S> {
+ pub(super) const fn empty() -> Self {
+ Self {
+ first: &ZERO_SPEC,
+ handlers: &[],
+ _p: PhantomData,
+ }
+ }
+}
+
+/// A zero-terminated parameter constant array.
+#[repr(C)]
+pub struct ConstantArray<const N: usize> {
+ consts: [bindings::constant_table; N],
+ sentinel: bindings::constant_table,
+}
+
+impl<const N: usize> ConstantArray<N> {
+ /// Creates a new constant array.
+ ///
+ /// Users are encouraged to use the [`define_fs_params`] macro to define the
+ /// [`super::Context::PARAMS`] constant.
+ pub const fn new(consts: [(&'static CStr, u32); N]) -> Self {
+ const ZERO: bindings::constant_table = bindings::constant_table {
+ name: core::ptr::null(),
+ value: 0,
+ };
+ let mut array = Self {
+ consts: [ZERO; N],
+ sentinel: ZERO,
+ };
+ let mut i = 0usize;
+ while i < N {
+ array.consts[i] = bindings::constant_table {
+ name: consts[i].0.as_char_ptr(),
+ value: consts[i].1 as _,
+ };
+ i += 1;
+ }
+ array
+ }
+
+ /// Returns a [`ConstantTable`] backed by `self`.
+ ///
+ /// This is used to essentially erase the array size.
+ pub const fn as_table(&self) -> ConstantTable<'_> {
+ ConstantTable {
+ first: &self.consts[0],
+ }
+ }
+}
+
+/// A parameter constant table.
+///
+/// The table is guaranteed to be zero-terminated.
+pub struct ConstantTable<'a> {
+ pub(super) first: &'a bindings::constant_table,
+}
+
+#[doc(hidden)]
+pub trait Handler<S: ForeignOwnable> {
+ fn handle_param(
+ &self,
+ state: &mut <S as ForeignOwnable>::BorrowedMut<'_>,
+ p: &bindings::fs_parameter,
+ r: &bindings::fs_parse_result,
+ ) -> Result;
+}
+
+struct ConcreteHandler<
+ S: ForeignOwnable,
+ T: Fn(
+ &mut <S as ForeignOwnable>::BorrowedMut<'_>,
+ &bindings::fs_parameter,
+ &bindings::fs_parse_result,
+ ) -> Result,
+> {
+ setfn: T,
+ _p: PhantomData<S>,
+}
+
+impl<
+ S: ForeignOwnable,
+ T: Fn(
+ &mut <S as ForeignOwnable>::BorrowedMut<'_>,
+ &bindings::fs_parameter,
+ &bindings::fs_parse_result,
+ ) -> Result,
+ > Handler<S> for ConcreteHandler<S, T>
+{
+ fn handle_param(
+ &self,
+ state: &mut <S as ForeignOwnable>::BorrowedMut<'_>,
+ p: &bindings::fs_parameter,
+ r: &bindings::fs_parse_result,
+ ) -> Result {
+ (self.setfn)(state, p, r)
+ }
+}
+
+/// Counts the number of parenthesis-delimited, comma-separated items.
+///
+/// # Examples
+///
+/// ```
+/// # use kernel::count_paren_items;
+///
+/// assert_eq!(0, count_paren_items!());
+/// assert_eq!(1, count_paren_items!((A)));
+/// assert_eq!(1, count_paren_items!((A),));
+/// assert_eq!(2, count_paren_items!((A), (B)));
+/// assert_eq!(2, count_paren_items!((A), (B),));
+/// assert_eq!(3, count_paren_items!((A), (B), (C)));
+/// assert_eq!(3, count_paren_items!((A), (B), (C),));
+/// ```
+#[macro_export]
+macro_rules! count_paren_items {
+ (($($item:tt)*), $($remaining:tt)*) => { 1 + $crate::count_paren_items!($($remaining)*) };
+ (($($item:tt)*)) => { 1 };
+ () => { 0 };
+}
+
+/// Counts the number of comma-separated entries surrounded by braces.
+///
+/// # Examples
+///
+/// ```
+/// # use kernel::count_brace_items;
+///
+/// assert_eq!(0, count_brace_items!());
+/// assert_eq!(1, count_brace_items!({A}));
+/// assert_eq!(1, count_brace_items!({A},));
+/// assert_eq!(2, count_brace_items!({A}, {B}));
+/// assert_eq!(2, count_brace_items!({A}, {B},));
+/// assert_eq!(3, count_brace_items!({A}, {B}, {C}));
+/// assert_eq!(3, count_brace_items!({A}, {B}, {C},));
+/// ```
+#[macro_export]
+macro_rules! count_brace_items {
+ ({$($item:tt)*}, $($remaining:tt)*) => { 1 + $crate::count_brace_items!($($remaining)*) };
+ ({$($item:tt)*}) => { 1 };
+ () => { 0 };
+}
+
+/// Defines the file system parameters of a given file system context.
+///
+/// # Examples
+/// ```
+/// # use kernel::prelude::*;
+/// # use kernel::{c_str, fs, str::CString};
+///
+/// #[derive(Default)]
+/// struct State {
+/// flag: Option<bool>,
+/// flag_no: Option<bool>,
+/// bool_value: Option<bool>,
+/// u32_value: Option<u32>,
+/// i32_value: Option<i32>,
+/// u64_value: Option<u64>,
+/// str_value: Option<CString>,
+/// enum_value: Option<u32>,
+/// }
+///
+/// fn set_u32(s: &mut Box<State>, v: u32) -> Result {
+/// s.u32_value = Some(v);
+/// Ok(())
+/// }
+///
+/// struct Example;
+///
+/// #[vtable]
+/// impl fs::Context<Self> for Example {
+/// type Data = Box<State>;
+///
+/// kernel::define_fs_params!{Box<State>,
+/// {flag, "flag", |s, v| { s.flag = Some(v); Ok(()) } },
+/// {flag_no, "flagno", |s, v| { s.flag_no = Some(v); Ok(()) } },
+/// {bool, "bool", |s, v| { s.bool_value = Some(v); Ok(()) } },
+/// {u32, "u32", set_u32 },
+/// {u32oct, "u32oct", set_u32 },
+/// {u32hex, "u32hex", set_u32 },
+/// {s32, "s32", |s, v| { s.i32_value = Some(v); Ok(()) } },
+/// {u64, "u64", |s, v| { s.u64_value = Some(v); Ok(()) } },
+/// {string, "string", |s, v| {
+/// s.str_value = Some(CString::try_from_fmt(fmt!("{v}"))?);
+/// Ok(())
+/// }},
+/// {enum, "enum", [("first", 10), ("second", 20)], |s, v| {
+/// s.enum_value = Some(v);
+/// Ok(())
+/// }},
+/// }
+///
+/// fn try_new() -> Result<Self::Data> {
+/// Ok(Box::try_new(State::default())?)
+/// }
+/// }
+///
+/// # impl fs::Type for Example {
+/// # type Context = Self;
+/// # const NAME: &'static CStr = c_str!("example");
+/// # const FLAGS: i32 = 0;
+/// # const MAGIC: u32 = 0x6578616d;
+/// # }
+/// ```
+#[macro_export]
+macro_rules! define_fs_params {
+ ($data_type:ty, $({$($t:tt)*}),+ $(,)?) => {
+ const PARAMS: $crate::fs::param::SpecTable<'static, $data_type> =
+ {
+ use $crate::fs::param::{self, ConstantArray, Spec, SpecArray, Handler};
+ use $crate::c_str;
+ const COUNT: usize = $crate::count_brace_items!($({$($t)*},)*);
+ const SPECS: [Spec; COUNT] = $crate::define_fs_params!(@specs $({$($t)*},)*);
+ const HANDLERS: [&dyn Handler<$data_type>; COUNT] =
+ $crate::define_fs_params!(@handlers $data_type, $({$($t)*},)*);
+ // SAFETY: We defined matching specs and handlers above.
+ const ARRAY: SpecArray<COUNT, $data_type> =
+ unsafe { SpecArray::new(SPECS, HANDLERS) };
+ ARRAY.as_table()
+ };
+ };
+
+ (@handlers $data_type:ty, $({$($t:tt)*},)*) => {
+ [ $($crate::define_fs_params!(@handler $data_type, $($t)*),)* ]
+ };
+ (@handler $data_type:ty, enum, $name:expr, $opts:expr, $closure:expr) => {
+ ¶m::enum_::handler::<$data_type>($closure)
+ };
+ (@handler $data_type:ty, $type:ident, $name:expr, $closure:expr) => {
+ ¶m::$type::handler::<$data_type>($closure)
+ };
+
+ (@specs $({$($t:tt)*},)*) => {[ $($crate::define_fs_params!(@spec $($t)*),)* ]};
+ (@spec enum, $name:expr, [$($opts:tt)*], $closure:expr) => {
+ {
+ const COUNT: usize = $crate::count_paren_items!($($opts)*);
+ const OPTIONS: ConstantArray<COUNT> =
+ ConstantArray::new($crate::define_fs_params!(@c_str_first $($opts)*));
+ param::enum_::spec(c_str!($name), OPTIONS.as_table())
+ }
+ };
+ (@spec $type:ident, $name:expr, $closure:expr) => { param::$type::spec(c_str!($name)) };
+
+ (@c_str_first $(($first:expr, $second:expr)),+ $(,)?) => {
+ [$((c_str!($first), $second),)*]
+ };
+}
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index ea1411a25ee4..59253f5390cd 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -12,11 +12,13 @@
//! do so first instead of bypassing this crate.
#![no_std]
+#![feature(associated_type_defaults)]
#![feature(coerce_unsized)]
#![feature(dispatch_from_dyn)]
#![feature(new_uninit)]
#![feature(receiver_trait)]
#![feature(unsize)]
+#![feature(const_mut_refs)]
// Ensure conditional compilation based on the kernel configuration works;
// otherwise we may silently break things like initcall handling.
@@ -62,6 +64,11 @@
#[doc(hidden)]
pub use build_error::build_error;
+/// Page size defined in terms of the `PAGE_SHIFT` macro from C.
+///
+/// [`PAGE_SHIFT`]: ../../../include/asm-generic/page.h
+pub const PAGE_SIZE: usize = 1 << bindings::PAGE_SHIFT;
+
/// Prefix to appear before log messages printed from within the `kernel` crate.
const __LOG_PREFIX: &[u8] = b"rust_kernel\0";
diff --git a/samples/rust/rust_rofs.rs b/samples/rust/rust_rofs.rs
index 5d0d1936459d..d81ea8fdf174 100644
--- a/samples/rust/rust_rofs.rs
+++ b/samples/rust/rust_rofs.rs
@@ -55,6 +55,31 @@ struct Entry {
const DIR_IOPS: inode::Ops<RoFs> = inode::Ops::new::<RoFs>();
const FILE_AOPS: address_space::Ops<RoFs> = address_space::Ops::new::<RoFs>();
+#[vtable]
+impl fs::Context<Self> for RoFs {
+ type Data = ();
+
+ kernel::define_fs_params! {(),
+ {flag, "flag", |_, v| { pr_info!("flag passed-in: {v}\n"); Ok(()) } },
+ {flag_no, "flagno", |_, v| { pr_info!("flagno passed-in: {v}\n"); Ok(()) } },
+ {bool, "bool", |_, v| { pr_info!("bool passed-in: {v}\n"); Ok(()) } },
+ {u32, "u32", |_, v| { pr_info!("u32 passed-in: {v}\n"); Ok(()) } },
+ {u32oct, "u32oct", |_, v| { pr_info!("u32oct passed-in: {v}\n"); Ok(()) } },
+ {u32hex, "u32hex", |_, v| { pr_info!("u32hex passed-in: {v}\n"); Ok(()) } },
+ {s32, "s32", |_, v| { pr_info!("s32 passed-in: {v}\n"); Ok(()) } },
+ {u64, "u64", |_, v| { pr_info!("u64 passed-in: {v}\n"); Ok(()) } },
+ {string, "string", |_, v| { pr_info!("string passed-in: {v}\n"); Ok(()) } },
+ {enum, "enum", [("first", 10), ("second", 20)], |_, v| {
+ pr_info!("enum passed-in: {v}\n"); Ok(()) }
+ },
+ }
+
+ fn try_new() -> Result {
+ pr_info!("context created!\n");
+ Ok(())
+ }
+}
+
struct RoFs;
impl RoFs {
@@ -103,11 +128,16 @@ fn iget(sb: &sb::SuperBlock<Self>, e: &'static Entry) -> Result<ARef<INode<Self>
}
impl fs::FileSystem for RoFs {
+ type Context = Self;
type Data = ();
type INodeData = &'static Entry;
const NAME: &'static CStr = c_str!("rust_rofs");
- fn fill_super(sb: &mut sb::SuperBlock<Self, sb::New>, _: Option<inode::Mapper>) -> Result {
+ fn fill_super(
+ _data: (),
+ sb: &mut sb::SuperBlock<Self, sb::New>,
+ _: Option<inode::Mapper>,
+ ) -> Result {
sb.set_magic(0x52555354);
Ok(())
}
--
2.34.1