rust: CStr overhaul

`CStr` is overhauled to make using it more similar to use a `str`. Signed-off-by: Gary Guo <gary@garyguo.net>

Author: nbdd0121

drivers/android/rust_binder.rs

@@ -10,7 +10,7 @@
 use alloc::{boxed::Box, sync::Arc};
 use core::pin::Pin;
 use kernel::{
- cstr,
+ c_str,
  io_buffer::IoBufferWriter,
  linked_list::{GetLinks, GetLinksWrapped, Links},
  miscdev::Registration,
@@ -111,7 +111,7 @@ impl KernelModule for BinderModule {
  let pinned_ctx = Context::new()?;
  let ctx = unsafe { Pin::into_inner_unchecked(pinned_ctx) };
  let reg = Registration::<Arc<Context>>::new_pinned::<process::Process>(
- cstr!("rust_binder"),
+ c_str!("rust_binder"),
  None,
  ctx,
  )?;

drivers/char/hw_random/bcm2835_rng_rust.rs

@@ -9,7 +9,7 @@ use alloc::boxed::Box;
 use core::pin::Pin;
 use kernel::of::OfMatchTable;
 use kernel::prelude::*;
-use kernel::{cstr, platdev};
+use kernel::{c_str, platdev};
 
 module! {
  type: RngModule,
@@ -25,7 +25,7 @@ struct RngModule {
 
 impl KernelModule for RngModule {
  fn init() -> Result<Self> {
- let of_match_tbl = OfMatchTable::new(&cstr!("brcm,bcm2835-rng"))?;
+ let of_match_tbl = OfMatchTable::new(&c_str!("brcm,bcm2835-rng"))?;
 
  let pdev = platdev::Registration::new_pinned(
  cstr!("bcm2835-rng-rust"),

rust/kernel/c_types.rs

@@ -117,18 +117,3 @@ mod c {
 }
 
 pub use c::*;
-
-/// Reads string until null byte is reached and returns slice excluding the
-/// terminating null.
-///
-/// # Safety
-///
-/// The data from the pointer until the null terminator must be valid for reads
-/// and not mutated for all of `'a`. The length of the string must also be less
-/// than `isize::MAX`. See the documentation on
-/// [`core::slice::from_raw_parts()`] for further details on safety of
-/// converting a pointer to a slice.
-pub unsafe fn c_string_bytes<'a>(ptr: *const crate::c_types::c_char) -> &'a [u8] {
- let length = crate::bindings::strlen(ptr) as usize;
- &core::slice::from_raw_parts(ptr as *const u8, length)
-}

rust/kernel/chrdev.rs

@@ -17,7 +17,7 @@ use crate::bindings;
 use crate::c_types;
 use crate::error::{Error, Result};
 use crate::file_operations;
-use crate::types::CStr;
+use crate::str::CStr;
 
 /// Character device.
 ///
@@ -87,7 +87,7 @@ struct RegistrationInner<const N: usize> {
 ///
 /// May contain up to a fixed number (`N`) of devices. Must be pinned.
 pub struct Registration<const N: usize> {
- name: CStr<'static>,
+ name: &'static CStr,
  minors_start: u16,
  this_module: &'static crate::ThisModule,
  inner: Option<RegistrationInner<N>>,
@@ -104,7 +104,7 @@ impl<const N: usize> Registration<{ N }> {
  /// are going to pin the registration right away, call
  /// [`Self::new_pinned()`] instead.
  pub fn new(
- name: CStr<'static>,
+ name: &'static CStr,
  minors_start: u16,
  this_module: &'static crate::ThisModule,
  ) -> Self {
@@ -120,7 +120,7 @@ impl<const N: usize> Registration<{ N }> {
  ///
  /// This does *not* register the device: see [`Self::register()`].
  pub fn new_pinned(
- name: CStr<'static>,
+ name: &'static CStr,
  minors_start: u16,
  this_module: &'static crate::ThisModule,
  ) -> Result<Pin<Box<Self>>> {
@@ -146,7 +146,7 @@ impl<const N: usize> Registration<{ N }> {
  &mut dev,
  this.minors_start.into(),
  N.try_into()?,
- this.name.as_ptr() as *const c_types::c_char,
+ this.name.as_char_ptr(),
  )
  };
  if res != 0 {

rust/kernel/lib.rs

@@ -19,6 +19,7 @@
  const_fn,
  const_mut_refs,
  const_panic,
+ const_raw_ptr_deref,
  try_reserve
 )]
 #![deny(clippy::complexity)]
@@ -44,6 +45,7 @@ pub mod file;
 pub mod file_operations;
 pub mod miscdev;
 pub mod pages;
+pub mod str;
 
 pub mod linked_list;
 mod raw_list;
@@ -72,7 +74,7 @@ pub mod user_ptr;
 pub use build_error::build_error;
 
 pub use crate::error::{Error, Result};
-pub use crate::types::{CStr, Mode};
+pub use crate::types::Mode;
 
 /// Page size defined in terms of the `PAGE_SHIFT` macro from C.
 ///

rust/kernel/miscdev.rs

@@ -6,9 +6,10 @@
 //!
 //! Reference: <https://www.kernel.org/doc/html/latest/driver-api/misc_devices.html>
 
+use crate::bindings;
 use crate::error::{Error, Result};
 use crate::file_operations::{FileOpenAdapter, FileOpener, FileOperationsVtable};
-use crate::{bindings, c_types, CStr};
+use crate::str::CStr;
 use alloc::boxed::Box;
 use core::marker::PhantomPinned;
 use core::pin::Pin;
@@ -41,7 +42,7 @@ impl<T: Sync> Registration<T> {
  ///
  /// Returns a pinned heap-allocated representation of the registration.
  pub fn new_pinned<F: FileOpener<T>>(
- name: CStr<'static>,
+ name: &'static CStr,
  minor: Option<i32>,
  context: T,
  ) -> Result<Pin<Box<Self>>> {
@@ -56,7 +57,7 @@ impl<T: Sync> Registration<T> {
  /// self-referential. If a minor is not given, the kernel allocates a new one if possible.
  pub fn register<F: FileOpener<T>>(
  self: Pin<&mut Self>,
- name: CStr<'static>,
+ name: &'static CStr,
  minor: Option<i32>,
  ) -> Result {
  // SAFETY: We must ensure that we never move out of `this`.
@@ -68,7 +69,7 @@ impl<T: Sync> Registration<T> {
 
  // SAFETY: The adapter is compatible with `misc_register`.
  this.mdev.fops = unsafe { FileOperationsVtable::<Self, F>::build() };
- this.mdev.name = name.as_ptr() as *const c_types::c_char;
+ this.mdev.name = name.as_char_ptr();
  this.mdev.minor = minor.unwrap_or(bindings::MISC_DYNAMIC_MINOR as i32);
 
  let ret = unsafe { bindings::misc_register(&mut this.mdev) };

rust/kernel/module_param.rs

@@ -4,6 +4,7 @@
 //!
 //! C header: [`include/linux/moduleparam.h`](../../../include/linux/moduleparam.h)
 
+use crate::str::CStr;
 use core::fmt::Write;
 
 /// Types that can be used for module parameters.
@@ -70,7 +71,7 @@ pub trait ModuleParam: core::fmt::Display + core::marker::Sized {
  let arg = if val.is_null() {
  None
  } else {
- Some(crate::c_types::c_string_bytes(val))
+ Some(CStr::from_char_ptr(val).as_bytes())
  };
  match Self::try_from_param_arg(arg) {
  Some(new_value) => {

rust/kernel/of.rs

@@ -9,8 +9,8 @@ use alloc::boxed::Box;
 use crate::{
  bindings, c_types,
  error::{Error, Result},
+ str::CStr,
  types::PointerWrapper,
- CStr,
 };
 
 use core::mem::transmute;
@@ -32,7 +32,7 @@ pub struct OfMatchTable(InnerTable);
 
 impl OfMatchTable {
  /// Creates a [`OfMatchTable`] from a single `compatible` string.
- pub fn new(compatible: &CStr<'static>) -> Result<Self> {
+ pub fn new(compatible: &'static CStr) -> Result<Self> {
  let tbl = Box::try_new([
  Self::new_of_device_id(compatible)?,
  bindings::of_device_id::default(),
@@ -43,7 +43,7 @@ impl OfMatchTable {
  Ok(Self(tbl))
  }
 
- fn new_of_device_id(compatible: &CStr<'static>) -> Result<bindings::of_device_id> {
+ fn new_of_device_id(compatible: &'static CStr) -> Result<bindings::of_device_id> {
  let mut buf = [0_u8; 128];
  if compatible.len() > buf.len() {
  return Err(Error::EINVAL);

rust/kernel/platdev.rs

@@ -11,8 +11,8 @@ use crate::{
  error::{Error, Result},
  of::OfMatchTable,
  pr_info,
+ str::CStr,
  types::PointerWrapper,
- CStr,
 };
 use alloc::boxed::Box;
 use core::{marker::PhantomPinned, pin::Pin};
@@ -43,7 +43,7 @@ extern "C" fn remove_callback(_pdev: *mut bindings::platform_device) -> c_types:
 impl Registration {
  fn register(
  self: Pin<&mut Self>,
- name: CStr<'static>,
+ name: &'static CStr,
  of_match_table: Option<OfMatchTable>,
  module: &'static crate::ThisModule,
  ) -> Result {
@@ -53,7 +53,7 @@ impl Registration {
  // Already registered.
  return Err(Error::EINVAL);
  }
- this.pdrv.driver.name = name.as_ptr() as *const c_types::c_char;
+ this.pdrv.driver.name = name.as_char_ptr();
  if let Some(tbl) = of_match_table {
  let ptr = tbl.into_pointer();
  this.of_table = Some(ptr);
@@ -82,7 +82,7 @@ impl Registration {
  ///
  /// Returns a pinned heap-allocated representation of the registration.
  pub fn new_pinned(
- name: CStr<'static>,
+ name: &'static CStr,
  of_match_tbl: Option<OfMatchTable>,
  module: &'static crate::ThisModule,
  ) -> Result<Pin<Box<Self>>> {