[PATCH] rust: add `module_params` macro

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From: Andreas Hindborg <a.hindborg@xxxxxxxxxxx>

This patch includes changes required for Rust kernel modules to utilize
module parameters. This code implements read only support for integer
types without `sysfs` support.

This code is a reduced and updated version of code by Adam available in the
original `rust` branch [1].

[1] https://github.com/Rust-for-Linux/linux/tree/bc22545f38d74473cfef3e9fd65432733435b79f

Cc: Adam Bratschi-Kaye <ark.email@xxxxxxxxx>
Signed-off-by: Andreas Hindborg <a.hindborg@xxxxxxxxxxx>

---

I have patches queued up for `rnull` that depend on this patch.
---
 rust/bindings/bindings_helper.h |   1 +
 rust/kernel/lib.rs              |   2 +
 rust/kernel/module_param.rs     | 339 ++++++++++++++++++++++++++++++++
 rust/macros/helpers.rs          |   8 +
 rust/macros/module.rs           | 230 ++++++++++++++++++++--
 samples/rust/rust_minimal.rs    |  10 +
 6 files changed, 571 insertions(+), 19 deletions(-)
 create mode 100644 rust/kernel/module_param.rs

diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
index ddb5644d4fd9..767169f46f10 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -25,3 +25,4 @@ const gfp_t RUST_CONST_HELPER_GFP_KERNEL = GFP_KERNEL;
 const gfp_t RUST_CONST_HELPER_GFP_KERNEL_ACCOUNT = GFP_KERNEL_ACCOUNT;
 const gfp_t RUST_CONST_HELPER_GFP_NOWAIT = GFP_NOWAIT;
 const gfp_t RUST_CONST_HELPER___GFP_ZERO = __GFP_ZERO;
+const size_t RUST_CONST_HELPER_PAGE_SIZE = PAGE_SIZE;
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index fbd91a48ff8b..7cc2730e572f 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -33,6 +33,8 @@
 pub mod ioctl;
 #[cfg(CONFIG_KUNIT)]
 pub mod kunit;
+#[doc(hidden)]
+pub mod module_param;
 #[cfg(CONFIG_NET)]
 pub mod net;
 pub mod prelude;
diff --git a/rust/kernel/module_param.rs b/rust/kernel/module_param.rs
new file mode 100644
index 000000000000..dc1108d20723
--- /dev/null
+++ b/rust/kernel/module_param.rs
@@ -0,0 +1,339 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Types for module parameters.
+//!
+//! C header: [`include/linux/moduleparam.h`](../../../include/linux/moduleparam.h)
+
+use crate::{error::code::*, str::CStr};
+
+/// Types that can be used for module parameters.
+///
+/// Note that displaying the type in `sysfs` will fail if
+/// [`core::str::from_utf8`] (as implemented through the [`core::fmt::Display`]
+/// trait) writes more than [`PAGE_SIZE`] bytes (including an additional null
+/// terminator).
+///
+/// [`PAGE_SIZE`]: `bindings::PAGE_SIZE`
+pub trait ModuleParam: core::fmt::Display + core::marker::Sized {
+    /// The `ModuleParam` will be used by the kernel module through this type.
+    ///
+    /// This may differ from `Self` if, for example, `Self` needs to track
+    /// ownership without exposing it or allocate extra space for other possible
+    /// parameter values. This is required to support string parameters in the
+    /// future.
+    type Value: ?Sized;
+
+    /// Whether the parameter is allowed to be set without an argument.
+    ///
+    /// Setting this to `true` allows the parameter to be passed without an
+    /// argument (e.g. just `module.param` instead of `module.param=foo`).
+    const NOARG_ALLOWED: bool;
+
+    /// Convert a parameter argument into the parameter value.
+    ///
+    /// `None` should be returned when parsing of the argument fails.
+    /// `arg == None` indicates that the parameter was passed without an
+    /// argument. If `NOARG_ALLOWED` is set to `false` then `arg` is guaranteed
+    /// to always be `Some(_)`.
+    ///
+    /// Parameters passed at boot time will be set before [`kmalloc`] is
+    /// available (even if the module is loaded at a later time). However, in
+    /// this case, the argument buffer will be valid for the entire lifetime of
+    /// the kernel. So implementations of this method which need to allocate
+    /// should first check that the allocator is available (with
+    /// [`crate::bindings::slab_is_available`]) and when it is not available
+    /// provide an alternative implementation which doesn't allocate. In cases
+    /// where the allocator is not available it is safe to save references to
+    /// `arg` in `Self`, but in other cases a copy should be made.
+    ///
+    /// [`kmalloc`]: ../../../include/linux/slab.h
+    fn try_from_param_arg(arg: Option<&'static [u8]>) -> Option<Self>;
+
+    /// Get the current value of the parameter for use in the kernel module.
+    ///
+    /// This function should not be used directly. Instead use the wrapper
+    /// `read` which will be generated by [`macros::module`].
+    fn value(&self) -> &Self::Value;
+
+    /// Set the module parameter from a string.
+    ///
+    /// Used to set the parameter value at kernel initialization, when loading
+    /// the module or when set through `sysfs`.
+    ///
+    /// `param.arg` is a pointer to `*mut Self` as set up by the [`module!`]
+    /// macro.
+    ///
+    /// See `struct kernel_param_ops.set`.
+    ///
+    /// # Safety
+    ///
+    /// If `val` is non-null then it must point to a valid null-terminated
+    /// string. The `arg` field of `param` must be an instance of `Self`.
+    ///
+    /// # Invariants
+    ///
+    /// Currently, we only support read-only parameters that are not readable
+    /// from `sysfs`. Thus, this function is only called at kernel
+    /// initialization time, or at module load time, and we have exclusive
+    /// access to the parameter for the duration of the function.
+    ///
+    /// [`module!`]: macros::module
+    unsafe extern "C" fn set_param(
+        val: *const core::ffi::c_char,
+        param: *const crate::bindings::kernel_param,
+    ) -> core::ffi::c_int {
+        let arg = if val.is_null() {
+            None
+        } else {
+            // SAFETY: By function safety requirement, val is non-null and
+            // null-terminated. By C API contract, `val` is live and valid for
+            // reads for the duration of this function.
+            Some(unsafe { CStr::from_char_ptr(val).as_bytes() })
+        };
+        match Self::try_from_param_arg(arg) {
+            Some(new_value) => {
+                // SAFETY: `param` is guaranteed to be valid by C API contract
+                // and `arg` is guaranteed to point to an instance of `Self`.
+                let old_value = unsafe { (*param).__bindgen_anon_1.arg as *mut Self };
+                // SAFETY: `old_value` is valid for writes, as we have exclusive
+                // access. `old_value` is pointing to an initialized static, an
+                // so it is properly initialized.
+                let _ = unsafe { core::ptr::replace(old_value, new_value) };
+                0
+            }
+            None => EINVAL.to_errno(),
+        }
+    }
+
+    /// Write a string representation of the current parameter value to `buf`.
+    ///
+    /// # Safety
+    ///
+    /// Must not be called.
+    ///
+    /// # Note
+    ///
+    /// This should not be called as we declare all parameters as read only.
+    unsafe extern "C" fn get_param(
+        _buf: *mut core::ffi::c_char,
+        _param: *const crate::bindings::kernel_param,
+    ) -> core::ffi::c_int {
+        0
+    }
+
+    /// Drop the parameter.
+    ///
+    /// Called when unloading a module.
+    ///
+    /// # Safety
+    ///
+    /// The `arg` field of `param` must be an initialized instance of `Self`.
+    unsafe extern "C" fn free(arg: *mut core::ffi::c_void) {
+        // SAFETY: By function safety requirement, `arg` is an initialized
+        // instance of `Self`. By C API contract, `arg` will not be used after
+        // this function returns.
+        unsafe { core::ptr::drop_in_place(arg as *mut Self) };
+    }
+}
+
+/// Trait for parsing integers.
+///
+/// Strings beginning with `0x`, `0o`, or `0b` are parsed as hex, octal, or
+/// binary respectively. Strings beginning with `0` otherwise are parsed as
+/// octal. Anything else is parsed as decimal. A leading `+` or `-` is also
+/// permitted. Any string parsed by [`kstrtol()`] or [`kstrtoul()`] will be
+/// successfully parsed.
+///
+/// [`kstrtol()`]: https://www.kernel.org/doc/html/latest/core-api/kernel-api.html#c.kstrtol
+/// [`kstrtoul()`]: https://www.kernel.org/doc/html/latest/core-api/kernel-api.html#c.kstrtoul
+trait ParseInt: Sized {
+    fn from_str_radix(src: &str, radix: u32) -> Result<Self, core::num::ParseIntError>;
+    fn checked_neg(self) -> Option<Self>;
+
+    fn from_str_unsigned(src: &str) -> Result<Self, core::num::ParseIntError> {
+        let (radix, digits) = if let Some(n) = src.strip_prefix("0x") {
+            (16, n)
+        } else if let Some(n) = src.strip_prefix("0X") {
+            (16, n)
+        } else if let Some(n) = src.strip_prefix("0o") {
+            (8, n)
+        } else if let Some(n) = src.strip_prefix("0O") {
+            (8, n)
+        } else if let Some(n) = src.strip_prefix("0b") {
+            (2, n)
+        } else if let Some(n) = src.strip_prefix("0B") {
+            (2, n)
+        } else if src.starts_with('0') {
+            (8, src)
+        } else {
+            (10, src)
+        };
+        Self::from_str_radix(digits, radix)
+    }
+
+    fn from_str(src: &str) -> Option<Self> {
+        match src.bytes().next() {
+            None => None,
+            Some(b'-') => Self::from_str_unsigned(&src[1..]).ok()?.checked_neg(),
+            Some(b'+') => Some(Self::from_str_unsigned(&src[1..]).ok()?),
+            Some(_) => Some(Self::from_str_unsigned(src).ok()?),
+        }
+    }
+}
+
+macro_rules! impl_parse_int {
+    ($ty:ident) => {
+        impl ParseInt for $ty {
+            fn from_str_radix(src: &str, radix: u32) -> Result<Self, core::num::ParseIntError> {
+                $ty::from_str_radix(src, radix)
+            }
+
+            fn checked_neg(self) -> Option<Self> {
+                self.checked_neg()
+            }
+        }
+    };
+}
+
+impl_parse_int!(i8);
+impl_parse_int!(u8);
+impl_parse_int!(i16);
+impl_parse_int!(u16);
+impl_parse_int!(i32);
+impl_parse_int!(u32);
+impl_parse_int!(i64);
+impl_parse_int!(u64);
+impl_parse_int!(isize);
+impl_parse_int!(usize);
+
+macro_rules! impl_module_param {
+    ($ty:ident) => {
+        impl ModuleParam for $ty {
+            type Value = $ty;
+
+            const NOARG_ALLOWED: bool = false;
+
+            fn try_from_param_arg(arg: Option<&'static [u8]>) -> Option<Self> {
+                let bytes = arg?;
+                let utf8 = core::str::from_utf8(bytes).ok()?;
+                <$ty as crate::module_param::ParseInt>::from_str(utf8)
+            }
+
+            #[inline(always)]
+            fn value(&self) -> &Self::Value {
+                self
+            }
+        }
+    };
+}
+
+#[doc(hidden)]
+#[macro_export]
+/// Generate a static [`kernel_param_ops`](../../../include/linux/moduleparam.h) struct.
+///
+/// # Examples
+///
+/// ```ignore
+/// make_param_ops!(
+///     /// Documentation for new param ops.
+///     PARAM_OPS_MYTYPE, // Name for the static.
+///     MyType // A type which implements [`ModuleParam`].
+/// );
+/// ```
+macro_rules! make_param_ops {
+    ($ops:ident, $ty:ty) => {
+        $crate::make_param_ops!(
+            #[doc=""]
+            $ops,
+            $ty
+        );
+    };
+    ($(#[$meta:meta])* $ops:ident, $ty:ty) => {
+        $(#[$meta])*
+        ///
+        /// Static [`kernel_param_ops`](../../../include/linux/moduleparam.h)
+        /// struct generated by [`make_param_ops`].
+        pub static $ops: $crate::bindings::kernel_param_ops = $crate::bindings::kernel_param_ops {
+            flags: if <$ty as $crate::module_param::ModuleParam>::NOARG_ALLOWED {
+                $crate::bindings::KERNEL_PARAM_OPS_FL_NOARG
+            } else {
+                0
+            },
+            set: Some(<$ty as $crate::module_param::ModuleParam>::set_param),
+            get: Some(<$ty as $crate::module_param::ModuleParam>::get_param),
+            free: Some(<$ty as $crate::module_param::ModuleParam>::free),
+        };
+    };
+}
+
+impl_module_param!(i8);
+impl_module_param!(u8);
+impl_module_param!(i16);
+impl_module_param!(u16);
+impl_module_param!(i32);
+impl_module_param!(u32);
+impl_module_param!(i64);
+impl_module_param!(u64);
+impl_module_param!(isize);
+impl_module_param!(usize);
+
+make_param_ops!(
+    /// Rust implementation of [`kernel_param_ops`](../../../include/linux/moduleparam.h)
+    /// for [`i8`].
+    PARAM_OPS_I8,
+    i8
+);
+make_param_ops!(
+    /// Rust implementation of [`kernel_param_ops`](../../../include/linux/moduleparam.h)
+    /// for [`u8`].
+    PARAM_OPS_U8,
+    u8
+);
+make_param_ops!(
+    /// Rust implementation of [`kernel_param_ops`](../../../include/linux/moduleparam.h)
+    /// for [`i16`].
+    PARAM_OPS_I16,
+    i16
+);
+make_param_ops!(
+    /// Rust implementation of [`kernel_param_ops`](../../../include/linux/moduleparam.h)
+    /// for [`u16`].
+    PARAM_OPS_U16,
+    u16
+);
+make_param_ops!(
+    /// Rust implementation of [`kernel_param_ops`](../../../include/linux/moduleparam.h)
+    /// for [`i32`].
+    PARAM_OPS_I32,
+    i32
+);
+make_param_ops!(
+    /// Rust implementation of [`kernel_param_ops`](../../../include/linux/moduleparam.h)
+    /// for [`u32`].
+    PARAM_OPS_U32,
+    u32
+);
+make_param_ops!(
+    /// Rust implementation of [`kernel_param_ops`](../../../include/linux/moduleparam.h)
+    /// for [`i64`].
+    PARAM_OPS_I64,
+    i64
+);
+make_param_ops!(
+    /// Rust implementation of [`kernel_param_ops`](../../../include/linux/moduleparam.h)
+    /// for [`u64`].
+    PARAM_OPS_U64,
+    u64
+);
+make_param_ops!(
+    /// Rust implementation of [`kernel_param_ops`](../../../include/linux/moduleparam.h)
+    /// for [`isize`].
+    PARAM_OPS_ISIZE,
+    isize
+);
+make_param_ops!(
+    /// Rust implementation of [`kernel_param_ops`](../../../include/linux/moduleparam.h)
+    /// for [`usize`].
+    PARAM_OPS_USIZE,
+    usize
+);
diff --git a/rust/macros/helpers.rs b/rust/macros/helpers.rs
index 563dcd2b7ace..dc0b47879a8c 100644
--- a/rust/macros/helpers.rs
+++ b/rust/macros/helpers.rs
@@ -107,6 +107,14 @@ pub(crate) struct Generics {
     pub(crate) ty_generics: Vec<TokenTree>,
 }
 
+pub(crate) fn get_string(it: &mut token_stream::IntoIter, expected_name: &str) -> String {
+    assert_eq!(expect_ident(it), expected_name);
+    assert_eq!(expect_punct(it), ':');
+    let string = expect_string(it);
+    assert_eq!(expect_punct(it), ',');
+    string
+}
+
 /// Parses the given `TokenStream` into `Generics` and the rest.
 ///
 /// The generics are not present in the rest, but a where clause might remain.
diff --git a/rust/macros/module.rs b/rust/macros/module.rs
index acd0393b5095..fc794855b99e 100644
--- a/rust/macros/module.rs
+++ b/rust/macros/module.rs
@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 
 use crate::helpers::*;
-use proc_macro::{token_stream, Delimiter, Literal, TokenStream, TokenTree};
+use proc_macro::{token_stream, Delimiter, Group, Literal, TokenStream, TokenTree};
 use std::fmt::Write;
 
 fn expect_string_array(it: &mut token_stream::IntoIter) -> Vec<String> {
@@ -26,6 +26,7 @@ struct ModInfoBuilder<'a> {
     module: &'a str,
     counter: usize,
     buffer: String,
+    param_buffer: String,
 }
 
 impl<'a> ModInfoBuilder<'a> {
@@ -34,10 +35,11 @@ fn new(module: &'a str) -> Self {
             module,
             counter: 0,
             buffer: String::new(),
+            param_buffer: String::new(),
         }
     }
 
-    fn emit_base(&mut self, field: &str, content: &str, builtin: bool) {
+    fn emit_base(&mut self, field: &str, content: &str, builtin: bool, param: bool) {
         let string = if builtin {
             // Built-in modules prefix their modinfo strings by `module.`.
             format!(
@@ -51,8 +53,14 @@ fn emit_base(&mut self, field: &str, content: &str, builtin: bool) {
             format!("{field}={content}\0", field = field, content = content)
         };
 
+        let buffer = if param {
+            &mut self.param_buffer
+        } else {
+            &mut self.buffer
+        };
+
         write!(
-            &mut self.buffer,
+            buffer,
             "
                 {cfg}
                 #[doc(hidden)]
@@ -75,20 +83,190 @@ fn emit_base(&mut self, field: &str, content: &str, builtin: bool) {
         self.counter += 1;
     }
 
-    fn emit_only_builtin(&mut self, field: &str, content: &str) {
-        self.emit_base(field, content, true)
+    fn emit_only_builtin(&mut self, field: &str, content: &str, param: bool) {
+        self.emit_base(field, content, true, param)
     }
 
-    fn emit_only_loadable(&mut self, field: &str, content: &str) {
-        self.emit_base(field, content, false)
+    fn emit_only_loadable(&mut self, field: &str, content: &str, param: bool) {
+        self.emit_base(field, content, false, param)
     }
 
     fn emit(&mut self, field: &str, content: &str) {
-        self.emit_only_builtin(field, content);
-        self.emit_only_loadable(field, content);
+        self.emit_internal(field, content, false);
+    }
+
+    fn emit_internal(&mut self, field: &str, content: &str, param: bool) {
+        self.emit_only_builtin(field, content, param);
+        self.emit_only_loadable(field, content, param);
+    }
+
+    fn emit_param(&mut self, field: &str, param: &str, content: &str) {
+        let content = format!("{param}:{content}", param = param, content = content);
+        self.emit_internal(field, &content, true);
+    }
+
+    fn emit_params(&mut self, info: &ModuleInfo) {
+        if let Some(params) = &info.params {
+            assert_eq!(params.delimiter(), Delimiter::Brace);
+
+            let mut it = params.stream().into_iter();
+
+            loop {
+                let param_name = match it.next() {
+                    Some(TokenTree::Ident(ident)) => ident.to_string(),
+                    Some(_) => panic!("Expected Ident or end"),
+                    None => break,
+                };
+
+                assert_eq!(expect_punct(&mut it), ':');
+                let param_type = expect_ident(&mut it);
+                let group = expect_group(&mut it);
+                assert_eq!(expect_punct(&mut it), ',');
+
+                assert_eq!(group.delimiter(), Delimiter::Brace);
+
+                let mut param_it = group.stream().into_iter();
+                let param_default = get_param_default(&mut param_it);
+                let param_description = get_string(&mut param_it, "description");
+                expect_end(&mut param_it);
+
+                let (param_kernel_type, ops): (String, _) = (
+                    param_type.to_string(),
+                    param_ops_path(&param_type).to_string(),
+                );
+
+                self.emit_param("parmtype", &param_name, &param_kernel_type);
+                self.emit_param("parm", &param_name, &param_description);
+                let param_type_internal = param_type.clone();
+
+                let read_func = format!(
+                    "
+                        pub(crate) fn read(&self)
+                            -> &<{param_type_internal}
+                               as kernel::module_param::ModuleParam>::Value {{
+                            // Note: when we enable r/w parameters, we need to lock here.
+
+                            // SAFETY: Parameters do not need to be locked because they are
+                            // read only or sysfs is not enabled.
+                            unsafe {{
+                                <{param_type_internal} as kernel::module_param::ModuleParam>::value(
+                                    &__{name}_{param_name}_value
+                                )
+                            }}
+                        }}
+                    ",
+                    name = info.name,
+                    param_name = param_name,
+                    param_type_internal = param_type_internal,
+                );
+
+                let kparam = format!(
+                    "
+                    kernel::bindings::kernel_param__bindgen_ty_1 {{
+                        // SAFETY: Access through the resulting pointer is
+                        // serialized by C side and only happens before module
+                        // `init` or after module `drop` is called.
+                        arg: unsafe {{ &__{name}_{param_name}_value }}
+                            as *const _ as *mut core::ffi::c_void,
+                    }},
+                ",
+                    name = info.name,
+                    param_name = param_name,
+                );
+                write!(
+                    self.param_buffer,
+                    "
+                static mut __{name}_{param_name}_value: {param_type_internal} = {param_default};
+
+                pub(crate) struct __{name}_{param_name};
+
+                impl __{name}_{param_name} {{ {read_func} }}
+
+                pub(crate) const {param_name}: __{name}_{param_name} = __{name}_{param_name};
+
+                // Note: the C macro that generates the static structs for the `__param` section
+                // asks for them to be `aligned(sizeof(void *))`. However, that was put in place
+                // in 2003 in commit 38d5b085d2a0 (\"[PATCH] Fix over-alignment problem on x86-64\")
+                // to undo GCC over-alignment of static structs of >32 bytes. It seems that is
+                // not the case anymore, so we simplify to a transparent representation here
+                // in the expectation that it is not needed anymore.
+                // TODO: Revisit this to confirm the above comment and remove it if it happened.
+                /// Newtype to make `bindings::kernel_param` `Sync`.
+                #[repr(transparent)]
+                struct __{name}_{param_name}_RacyKernelParam(kernel::bindings::kernel_param);
+
+                // SAFETY: C kernel handles serializing access to this type. We
+                // never access from Rust module.
+                unsafe impl Sync for __{name}_{param_name}_RacyKernelParam {{
+                }}
+
+                #[cfg(not(MODULE))]
+                const __{name}_{param_name}_name: *const core::ffi::c_char =
+                    b\"{name}.{param_name}\\0\" as *const _ as *const core::ffi::c_char;
+
+                #[cfg(MODULE)]
+                const __{name}_{param_name}_name: *const core::ffi::c_char =
+                    b\"{param_name}\\0\" as *const _ as *const core::ffi::c_char;
+
+                #[link_section = \"__param\"]
+                #[used]
+                static __{name}_{param_name}_struct: __{name}_{param_name}_RacyKernelParam =
+                    __{name}_{param_name}_RacyKernelParam(kernel::bindings::kernel_param {{
+                        name: __{name}_{param_name}_name,
+                        // SAFETY: `__this_module` is constructed by the kernel at load time
+                        // and will not be freed until the module is unloaded.
+                        #[cfg(MODULE)]
+                        mod_: unsafe {{ &kernel::bindings::__this_module as *const _ as *mut _ }},
+                        #[cfg(not(MODULE))]
+                        mod_: core::ptr::null_mut(),
+                        // SAFETY: This static is actually constant as seen by
+                        // module code. But we need a unique address for it, so it
+                        // must be static.
+                        ops: unsafe {{ &{ops} }} as *const kernel::bindings::kernel_param_ops,
+                        perm: 0, // Will not appear in sysfs
+                        level: -1,
+                        flags: 0,
+                        __bindgen_anon_1: {kparam}
+                    }});
+                ",
+                    name = info.name,
+                    param_type_internal = param_type_internal,
+                    read_func = read_func,
+                    param_default = param_default,
+                    param_name = param_name,
+                    ops = ops,
+                    kparam = kparam,
+                )
+                .unwrap();
+            }
+        }
     }
 }
 
+fn param_ops_path(param_type: &str) -> &'static str {
+    match param_type {
+        "i8" => "::kernel::module_param::PARAM_OPS_I8",
+        "u8" => "::kernel::module_param::PARAM_OPS_U8",
+        "i16" => "::kernel::module_param::PARAM_OPS_I16",
+        "u16" => "::kernel::module_param::PARAM_OPS_U16",
+        "i32" => "::kernel::module_param::PARAM_OPS_I32",
+        "u32" => "::kernel::module_param::PARAM_OPS_U32",
+        "i64" => "::kernel::module_param::PARAM_OPS_I64",
+        "u64" => "::kernel::module_param::PARAM_OPS_U64",
+        "isize" => "::kernel::module_param::PARAM_OPS_ISIZE",
+        "usize" => "::kernel::module_param::PARAM_OPS_USIZE",
+        t => panic!("Unrecognized type {}", t),
+    }
+}
+
+fn get_param_default(param_it: &mut token_stream::IntoIter) -> String {
+    assert_eq!(expect_ident(param_it), "default");
+    assert_eq!(expect_punct(param_it), ':');
+    let default = try_literal(param_it).expect("Expected default param value");
+    assert_eq!(expect_punct(param_it), ',');
+    default
+}
+
 #[derive(Debug, Default)]
 struct ModuleInfo {
     type_: String,
@@ -97,14 +275,22 @@ struct ModuleInfo {
     author: Option<String>,
     description: Option<String>,
     alias: Option<Vec<String>>,
+    params: Option<Group>,
 }
 
 impl ModuleInfo {
     fn parse(it: &mut token_stream::IntoIter) -> Self {
         let mut info = ModuleInfo::default();
 
-        const EXPECTED_KEYS: &[&str] =
-            &["type", "name", "author", "description", "license", "alias"];
+        const EXPECTED_KEYS: &[&str] = &[
+            "type",
+            "name",
+            "author",
+            "description",
+            "license",
+            "alias",
+            "params",
+        ];
         const REQUIRED_KEYS: &[&str] = &["type", "name", "license"];
         let mut seen_keys = Vec::new();
 
@@ -131,6 +317,7 @@ fn parse(it: &mut token_stream::IntoIter) -> Self {
                 "description" => info.description = Some(expect_string(it)),
                 "license" => info.license = expect_string_ascii(it),
                 "alias" => info.alias = Some(expect_string_array(it)),
+                "params" => info.params = Some(expect_group(it)),
                 _ => panic!(
                     "Unknown key \"{}\". Valid keys are: {:?}.",
                     key, EXPECTED_KEYS
@@ -174,23 +361,25 @@ pub(crate) fn module(ts: TokenStream) -> TokenStream {
     let info = ModuleInfo::parse(&mut it);
 
     let mut modinfo = ModInfoBuilder::new(info.name.as_ref());
-    if let Some(author) = info.author {
-        modinfo.emit("author", &author);
+    if let Some(author) = &info.author {
+        modinfo.emit("author", author);
     }
-    if let Some(description) = info.description {
-        modinfo.emit("description", &description);
+    if let Some(description) = &info.description {
+        modinfo.emit("description", description);
     }
     modinfo.emit("license", &info.license);
-    if let Some(aliases) = info.alias {
+    if let Some(aliases) = &info.alias {
         for alias in aliases {
-            modinfo.emit("alias", &alias);
+            modinfo.emit("alias", alias);
         }
     }
 
     // Built-in modules also export the `file` modinfo string.
     let file =
         std::env::var("RUST_MODFILE").expect("Unable to fetch RUST_MODFILE environmental variable");
-    modinfo.emit_only_builtin("file", &file);
+    modinfo.emit_only_builtin("file", &file, false);
+
+    modinfo.emit_params(&info);
 
     format!(
         "
@@ -332,14 +521,17 @@ unsafe fn __exit() {{
                             __MOD = None;
                         }}
                     }}
-
                     {modinfo}
                 }}
             }}
+            mod module_parameters {{
+                {params}
+            }}
         ",
         type_ = info.type_,
         name = info.name,
         modinfo = modinfo.buffer,
+        params = modinfo.param_buffer,
         initcall_section = ".initcall6.init"
     )
     .parse()
diff --git a/samples/rust/rust_minimal.rs b/samples/rust/rust_minimal.rs
index 2a9eaab62d1c..359e6d8ec983 100644
--- a/samples/rust/rust_minimal.rs
+++ b/samples/rust/rust_minimal.rs
@@ -10,6 +10,12 @@
     author: "Rust for Linux Contributors",
     description: "Rust minimal sample",
     license: "GPL",
+    params: {
+        test_parameter: i64 {
+            default: 1,
+            description: "This parameter has a default of 1",
+        },
+    },
 }
 
 struct RustMinimal {
@@ -20,6 +26,10 @@ impl kernel::Module for RustMinimal {
     fn init(_module: &'static ThisModule) -> Result<Self> {
         pr_info!("Rust minimal sample (init)\n");
         pr_info!("Am I built-in? {}\n", !cfg!(MODULE));
+        pr_info!(
+            "My parameter: {}\n",
+            *module_parameters::test_parameter.read()
+        );
 
         let mut numbers = Vec::new();
         numbers.push(72, GFP_KERNEL)?;

base-commit: f2661062f16b2de5d7b6a5c42a9a5c96326b8454
-- 
2.45.2







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