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authorGary Guo <gary@garyguo.net>2024-09-13 22:29:24 +0100
committerMiguel Ojeda <ojeda@kernel.org>2024-12-16 21:49:33 +0100
commit1bae8729e50a900f41e9a1c17ae81113e4cf62b8 (patch)
treef9a6239a2d8e118cd373bf6f1e19a8267da18444
parent27c7518e7f1ccaaa43eb5f25dc362779d2dc2ccb (diff)
rust: map `long` to `isize` and `char` to `u8`
The following FFI types are replaced compared to `core::ffi`: 1. `char` type is now always mapped to `u8`, since kernel uses `-funsigned-char` on the C code. `core::ffi` maps it to platform default ABI, which can be either signed or unsigned. 2. `long` is now always mapped to `isize`. It's very common in the kernel to use `long` to represent a pointer-sized integer, and in fact `intptr_t` is a typedef of `long` in the kernel. Enforce this mapping rather than mapping to `i32/i64` depending on platform can save us a lot of unnecessary casts. Signed-off-by: Gary Guo <gary@garyguo.net> Reviewed-by: Alice Ryhl <aliceryhl@google.com> Link: https://lore.kernel.org/r/20240913213041.395655-5-gary@garyguo.net [ Moved `uaccess` changes from the next commit, since they were irrefutable patterns that Rust >= 1.82.0 warns about. Reworded slightly and reformatted a few documentation comments. Rebased on top of `rust-next`. Added the removal of two casts to avoid Clippy warnings. - Miguel ] Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
-rw-r--r--rust/ffi.rs37
-rw-r--r--rust/kernel/error.rs5
-rw-r--r--rust/kernel/firmware.rs2
-rw-r--r--rust/kernel/miscdevice.rs4
-rw-r--r--rust/kernel/uaccess.rs27
5 files changed, 47 insertions, 28 deletions
diff --git a/rust/ffi.rs b/rust/ffi.rs
index be153c4d551b..584f75b49862 100644
--- a/rust/ffi.rs
+++ b/rust/ffi.rs
@@ -10,4 +10,39 @@
#![no_std]
-pub use core::ffi::*;
+macro_rules! alias {
+ ($($name:ident = $ty:ty;)*) => {$(
+ #[allow(non_camel_case_types, missing_docs)]
+ pub type $name = $ty;
+
+ // Check size compatibility with `core`.
+ const _: () = assert!(
+ core::mem::size_of::<$name>() == core::mem::size_of::<core::ffi::$name>()
+ );
+ )*}
+}
+
+alias! {
+ // `core::ffi::c_char` is either `i8` or `u8` depending on architecture. In the kernel, we use
+ // `-funsigned-char` so it's always mapped to `u8`.
+ c_char = u8;
+
+ c_schar = i8;
+ c_uchar = u8;
+
+ c_short = i16;
+ c_ushort = u16;
+
+ c_int = i32;
+ c_uint = u32;
+
+ // In the kernel, `intptr_t` is defined to be `long` in all platforms, so we can map the type to
+ // `isize`.
+ c_long = isize;
+ c_ulong = usize;
+
+ c_longlong = i64;
+ c_ulonglong = u64;
+}
+
+pub use core::ffi::c_void;
diff --git a/rust/kernel/error.rs b/rust/kernel/error.rs
index 52c502432447..5fece574ec02 100644
--- a/rust/kernel/error.rs
+++ b/rust/kernel/error.rs
@@ -153,11 +153,8 @@ impl Error {
/// Returns the error encoded as a pointer.
pub fn to_ptr<T>(self) -> *mut T {
- #[cfg_attr(target_pointer_width = "32", allow(clippy::useless_conversion))]
// SAFETY: `self.0` is a valid error due to its invariant.
- unsafe {
- bindings::ERR_PTR(self.0.get().into()) as *mut _
- }
+ unsafe { bindings::ERR_PTR(self.0.get() as _) as *mut _ }
}
/// Returns a string representing the error, if one exists.
diff --git a/rust/kernel/firmware.rs b/rust/kernel/firmware.rs
index 13a374a5cdb7..c5162fdc95ff 100644
--- a/rust/kernel/firmware.rs
+++ b/rust/kernel/firmware.rs
@@ -12,7 +12,7 @@ use core::ptr::NonNull;
/// One of the following: `bindings::request_firmware`, `bindings::firmware_request_nowarn`,
/// `bindings::firmware_request_platform`, `bindings::request_firmware_direct`.
struct FwFunc(
- unsafe extern "C" fn(*mut *const bindings::firmware, *const i8, *mut bindings::device) -> i32,
+ unsafe extern "C" fn(*mut *const bindings::firmware, *const u8, *mut bindings::device) -> i32,
);
impl FwFunc {
diff --git a/rust/kernel/miscdevice.rs b/rust/kernel/miscdevice.rs
index fbd761380384..8f88891fb1d2 100644
--- a/rust/kernel/miscdevice.rs
+++ b/rust/kernel/miscdevice.rs
@@ -225,7 +225,7 @@ unsafe extern "C" fn fops_ioctl<T: MiscDevice>(
// SAFETY: Ioctl calls can borrow the private data of the file.
let device = unsafe { <T::Ptr as ForeignOwnable>::borrow(private) };
- match T::ioctl(device, cmd, arg as usize) {
+ match T::ioctl(device, cmd, arg) {
Ok(ret) => ret as c_long,
Err(err) => err.to_errno() as c_long,
}
@@ -245,7 +245,7 @@ unsafe extern "C" fn fops_compat_ioctl<T: MiscDevice>(
// SAFETY: Ioctl calls can borrow the private data of the file.
let device = unsafe { <T::Ptr as ForeignOwnable>::borrow(private) };
- match T::compat_ioctl(device, cmd, arg as usize) {
+ match T::compat_ioctl(device, cmd, arg) {
Ok(ret) => ret as c_long,
Err(err) => err.to_errno() as c_long,
}
diff --git a/rust/kernel/uaccess.rs b/rust/kernel/uaccess.rs
index 05b0b8d13b10..cc044924867b 100644
--- a/rust/kernel/uaccess.rs
+++ b/rust/kernel/uaccess.rs
@@ -8,7 +8,7 @@ use crate::{
alloc::Flags,
bindings,
error::Result,
- ffi::{c_ulong, c_void},
+ ffi::c_void,
prelude::*,
transmute::{AsBytes, FromBytes},
};
@@ -224,13 +224,9 @@ impl UserSliceReader {
if len > self.length {
return Err(EFAULT);
}
- let Ok(len_ulong) = c_ulong::try_from(len) else {
- return Err(EFAULT);
- };
- // SAFETY: `out_ptr` points into a mutable slice of length `len_ulong`, so we may write
+ // SAFETY: `out_ptr` points into a mutable slice of length `len`, so we may write
// that many bytes to it.
- let res =
- unsafe { bindings::copy_from_user(out_ptr, self.ptr as *const c_void, len_ulong) };
+ let res = unsafe { bindings::copy_from_user(out_ptr, self.ptr as *const c_void, len) };
if res != 0 {
return Err(EFAULT);
}
@@ -259,9 +255,6 @@ impl UserSliceReader {
if len > self.length {
return Err(EFAULT);
}
- let Ok(len_ulong) = c_ulong::try_from(len) else {
- return Err(EFAULT);
- };
let mut out: MaybeUninit<T> = MaybeUninit::uninit();
// SAFETY: The local variable `out` is valid for writing `size_of::<T>()` bytes.
//
@@ -272,7 +265,7 @@ impl UserSliceReader {
bindings::_copy_from_user(
out.as_mut_ptr().cast::<c_void>(),
self.ptr as *const c_void,
- len_ulong,
+ len,
)
};
if res != 0 {
@@ -335,12 +328,9 @@ impl UserSliceWriter {
if len > self.length {
return Err(EFAULT);
}
- let Ok(len_ulong) = c_ulong::try_from(len) else {
- return Err(EFAULT);
- };
- // SAFETY: `data_ptr` points into an immutable slice of length `len_ulong`, so we may read
+ // SAFETY: `data_ptr` points into an immutable slice of length `len`, so we may read
// that many bytes from it.
- let res = unsafe { bindings::copy_to_user(self.ptr as *mut c_void, data_ptr, len_ulong) };
+ let res = unsafe { bindings::copy_to_user(self.ptr as *mut c_void, data_ptr, len) };
if res != 0 {
return Err(EFAULT);
}
@@ -359,9 +349,6 @@ impl UserSliceWriter {
if len > self.length {
return Err(EFAULT);
}
- let Ok(len_ulong) = c_ulong::try_from(len) else {
- return Err(EFAULT);
- };
// SAFETY: The reference points to a value of type `T`, so it is valid for reading
// `size_of::<T>()` bytes.
//
@@ -372,7 +359,7 @@ impl UserSliceWriter {
bindings::_copy_to_user(
self.ptr as *mut c_void,
(value as *const T).cast::<c_void>(),
- len_ulong,
+ len,
)
};
if res != 0 {