1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
|
// SPDX-License-Identifier: GPL-2.0
//! Support for module parameters.
//!
//! C header: [`include/linux/moduleparam.h`](srctree/include/linux/moduleparam.h)
use crate::prelude::*;
use crate::str::BStr;
use bindings;
use kernel::sync::SetOnce;
/// Newtype to make `bindings::kernel_param` [`Sync`].
#[repr(transparent)]
#[doc(hidden)]
pub struct KernelParam(bindings::kernel_param);
impl KernelParam {
#[doc(hidden)]
pub const fn new(val: bindings::kernel_param) -> Self {
Self(val)
}
}
// SAFETY: C kernel handles serializing access to this type. We never access it
// from Rust module.
unsafe impl Sync for KernelParam {}
/// Types that can be used for module parameters.
// NOTE: This trait is `Copy` because drop could produce unsoundness during teardown.
pub trait ModuleParam: Sized + Copy {
/// Parse a parameter argument into the parameter value.
fn try_from_param_arg(arg: &BStr) -> Result<Self>;
}
/// 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`.
///
/// See `struct kernel_param_ops.set`.
///
/// # Safety
///
/// - If `val` is non-null then it must point to a valid null-terminated string that must be valid
/// for reads for the duration of the call.
/// - `param` must be a pointer to a `bindings::kernel_param` initialized by the rust module macro.
/// The pointee must be valid for reads for the duration of the call.
///
/// # Note
///
/// - The safety requirements are satisfied by C API contract when this function is invoked by the
/// module subsystem C code.
/// - 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<T>(val: *const c_char, param: *const bindings::kernel_param) -> c_int
where
T: ModuleParam,
{
// NOTE: If we start supporting arguments without values, val _is_ allowed
// to be null here.
if val.is_null() {
// TODO: Use pr_warn_once available.
crate::pr_warn!("Null pointer passed to `module_param::set_param`");
return EINVAL.to_errno();
}
// SAFETY: By function safety requirement, val is non-null, null-terminated
// and valid for reads for the duration of this function.
let arg = unsafe { CStr::from_char_ptr(val) };
let arg: &BStr = arg.as_ref();
crate::error::from_result(|| {
let new_value = T::try_from_param_arg(arg)?;
// SAFETY: By function safety requirements, this access is safe.
let container = unsafe { &*((*param).__bindgen_anon_1.arg.cast::<SetOnce<T>>()) };
container
.populate(new_value)
.then_some(0)
.ok_or(kernel::error::code::EEXIST)
})
}
macro_rules! impl_int_module_param {
($ty:ident) => {
impl ModuleParam for $ty {
fn try_from_param_arg(arg: &BStr) -> Result<Self> {
<$ty as crate::str::parse_int::ParseInt>::from_str(arg)
}
}
};
}
impl_int_module_param!(i8);
impl_int_module_param!(u8);
impl_int_module_param!(i16);
impl_int_module_param!(u16);
impl_int_module_param!(i32);
impl_int_module_param!(u32);
impl_int_module_param!(i64);
impl_int_module_param!(u64);
impl_int_module_param!(isize);
impl_int_module_param!(usize);
/// A wrapper for kernel parameters.
///
/// This type is instantiated by the [`module!`] macro when module parameters are
/// defined. You should never need to instantiate this type directly.
///
/// Note: This type is `pub` because it is used by module crates to access
/// parameter values.
pub struct ModuleParamAccess<T> {
value: SetOnce<T>,
default: T,
}
// SAFETY: We only create shared references to the contents of this container,
// so if `T` is `Sync`, so is `ModuleParamAccess`.
unsafe impl<T: Sync> Sync for ModuleParamAccess<T> {}
impl<T> ModuleParamAccess<T> {
#[doc(hidden)]
pub const fn new(default: T) -> Self {
Self {
value: SetOnce::new(),
default,
}
}
/// Get a shared reference to the parameter value.
// Note: When sysfs access to parameters are enabled, we have to pass in a
// held lock guard here.
pub fn value(&self) -> &T {
self.value.as_ref().unwrap_or(&self.default)
}
/// Get a mutable pointer to `self`.
///
/// NOTE: In most cases it is not safe deref the returned pointer.
pub const fn as_void_ptr(&self) -> *mut c_void {
core::ptr::from_ref(self).cast_mut().cast()
}
}
#[doc(hidden)]
/// Generate a static [`kernel_param_ops`](srctree/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) => {
#[doc(hidden)]
pub static $ops: $crate::bindings::kernel_param_ops = $crate::bindings::kernel_param_ops {
flags: 0,
set: Some(set_param::<$ty>),
get: None,
free: None,
};
};
}
make_param_ops!(PARAM_OPS_I8, i8);
make_param_ops!(PARAM_OPS_U8, u8);
make_param_ops!(PARAM_OPS_I16, i16);
make_param_ops!(PARAM_OPS_U16, u16);
make_param_ops!(PARAM_OPS_I32, i32);
make_param_ops!(PARAM_OPS_U32, u32);
make_param_ops!(PARAM_OPS_I64, i64);
make_param_ops!(PARAM_OPS_U64, u64);
make_param_ops!(PARAM_OPS_ISIZE, isize);
make_param_ops!(PARAM_OPS_USIZE, usize);
|
