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Diffstat (limited to 'rust/kernel/fs/param.rs')
| -rw-r--r-- | rust/kernel/fs/param.rs | 553 |
1 files changed, 553 insertions, 0 deletions
diff --git a/rust/kernel/fs/param.rs b/rust/kernel/fs/param.rs new file mode 100644 index 000000000000..445cea404bcd --- /dev/null +++ b/rust/kernel/fs/param.rs @@ -0,0 +1,553 @@ +// 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::{bindings, file, fs, str::CStr, Result}; +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>(setfn: fn(&mut S, $fntype) -> Result) -> impl Handler<S> { + let c = + move |s: &mut S, + $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>(setfn: fn(&mut S, u32) -> Result) -> impl Handler<S> { + let c = move |s: &mut S, _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> { + fn handle_param( + &self, + state: &mut S, + p: &bindings::fs_parameter, + r: &bindings::fs_parse_result, + ) -> Result; +} + +struct ConcreteHandler< + S, + T: Fn(&mut S, &bindings::fs_parameter, &bindings::fs_parse_result) -> Result, +> { + setfn: T, + _p: PhantomData<S>, +} + +impl<S, T: Fn(&mut S, &bindings::fs_parameter, &bindings::fs_parse_result) -> Result> Handler<S> + for ConcreteHandler<S, T> +{ + fn handle_param( + &self, + state: &mut S, + p: &bindings::fs_parameter, + r: &bindings::fs_parse_result, + ) -> Result { + (self.setfn)(state, p, r) + } +} + +/// 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 SUPER_TYPE: fs::Super = fs::Super::Independent; +/// # const NAME: &'static CStr = c_str!("example"); +/// # const FLAGS: i32 = 0; +/// # +/// # fn fill_super<'a>( +/// # _data: Box<State>, +/// # sb: fs::NewSuperBlock<'_, Self>, +/// # ) -> Result<&fs::SuperBlock<Self>> { +/// # let sb = sb.init( +/// # (), +/// # &fs::SuperParams { +/// # magic: 0x6578616d, +/// # ..fs::SuperParams::DEFAULT +/// # }, +/// # )?; +/// # let sb = sb.init_root()?; +/// # Ok(sb) +/// # } +/// # } +/// ``` +#[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),)*] + }; +} |