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// SPDX-License-Identifier: GPL-2.0
use alloc::boxed::Box;
use alloc::vec;
use core::mem;
use core::ptr;
use core::sync::atomic;
use crate::bindings;
use crate::c_types;
use crate::error;
use crate::types;
use crate::user_ptr::{UserSlicePtr, UserSlicePtrWriter};
pub trait SysctlStorage: Sync {
fn store_value(&self, data: &[u8]) -> (usize, error::KernelResult<()>);
fn read_value(&self, data: &mut UserSlicePtrWriter) -> (usize, error::KernelResult<()>);
}
fn trim_whitespace(mut data: &[u8]) -> &[u8] {
while !data.is_empty() && (data[0] == b' ' || data[0] == b'\t' || data[0] == b'\n') {
data = &data[1..];
}
while !data.is_empty()
&& (data[data.len() - 1] == b' '
|| data[data.len() - 1] == b'\t'
|| data[data.len() - 1] == b'\n')
{
data = &data[..data.len() - 1];
}
data
}
impl<T> SysctlStorage for &T
where
T: SysctlStorage,
{
fn store_value(&self, data: &[u8]) -> (usize, error::KernelResult<()>) {
(*self).store_value(data)
}
fn read_value(&self, data: &mut UserSlicePtrWriter) -> (usize, error::KernelResult<()>) {
(*self).read_value(data)
}
}
impl SysctlStorage for atomic::AtomicBool {
fn store_value(&self, data: &[u8]) -> (usize, error::KernelResult<()>) {
let result = match trim_whitespace(data) {
b"0" => {
self.store(false, atomic::Ordering::Relaxed);
Ok(())
}
b"1" => {
self.store(true, atomic::Ordering::Relaxed);
Ok(())
}
_ => Err(error::Error::EINVAL),
};
(data.len(), result)
}
fn read_value(&self, data: &mut UserSlicePtrWriter) -> (usize, error::KernelResult<()>) {
let value = if self.load(atomic::Ordering::Relaxed) {
b"1\n"
} else {
b"0\n"
};
(value.len(), data.write(value))
}
}
pub struct Sysctl<T: SysctlStorage> {
inner: Box<T>,
// Responsible for keeping the ctl_table alive.
_table: Box<[bindings::ctl_table]>,
header: *mut bindings::ctl_table_header,
}
// This is safe because the only public method we have is get(), which returns
// &T, and T: Sync. Any new methods must adhere to this requirement.
unsafe impl<T: SysctlStorage> Sync for Sysctl<T> {}
unsafe extern "C" fn proc_handler<T: SysctlStorage>(
ctl: *mut bindings::ctl_table,
write: c_types::c_int,
buffer: *mut c_types::c_void,
len: *mut usize,
ppos: *mut bindings::loff_t,
) -> c_types::c_int {
// If we're reading from some offset other than the beginning of the file,
// return an empty read to signal EOF.
if *ppos != 0 && write == 0 {
*len = 0;
return 0;
}
let data = match UserSlicePtr::new(buffer, *len) {
Ok(ptr) => ptr,
Err(e) => return e.to_kernel_errno(),
};
let storage = &*((*ctl).data as *const T);
let (bytes_processed, result) = if write != 0 {
let data = match data.read_all() {
Ok(r) => r,
Err(e) => return e.to_kernel_errno(),
};
storage.store_value(&data)
} else {
let mut writer = data.writer();
storage.read_value(&mut writer)
};
*len = bytes_processed;
*ppos += *len as bindings::loff_t;
match result {
Ok(()) => 0,
Err(e) => e.to_kernel_errno(),
}
}
impl<T: SysctlStorage> Sysctl<T> {
pub fn register(
path: &'static types::CStr,
name: &'static types::CStr,
storage: T,
mode: types::Mode,
) -> error::KernelResult<Sysctl<T>> {
if name.contains('/') {
return Err(error::Error::EINVAL);
}
let storage = Box::new(storage);
let mut table = vec![
bindings::ctl_table {
procname: name.as_ptr() as *const i8,
mode: mode.as_int(),
data: &*storage as *const T as *mut c_types::c_void,
proc_handler: Some(proc_handler::<T>),
maxlen: 0,
child: ptr::null_mut(),
poll: ptr::null_mut(),
extra1: ptr::null_mut(),
extra2: ptr::null_mut(),
},
unsafe { mem::zeroed() },
]
.into_boxed_slice();
let result =
unsafe { bindings::register_sysctl(path.as_ptr() as *const i8, table.as_mut_ptr()) };
if result.is_null() {
return Err(error::Error::ENOMEM);
}
Ok(Sysctl {
inner: storage,
_table: table,
header: result,
})
}
pub fn get(&self) -> &T {
&self.inner
}
}
impl<T: SysctlStorage> Drop for Sysctl<T> {
fn drop(&mut self) {
unsafe {
bindings::unregister_sysctl_table(self.header);
}
self.header = ptr::null_mut();
}
}
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