From: Gary Guo <gary@xxxxxxxxxxx> commit 1bae8729e50a900f41e9a1c17ae81113e4cf62b8 upstream. 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@xxxxxxxxxxx> Reviewed-by: Alice Ryhl <aliceryhl@xxxxxxxxxx> Link: https://lore.kernel.org/r/20240913213041.395655-5-gary@xxxxxxxxxxx [ 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@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- rust/ffi.rs | 37 ++++++++++++++++++++++++++++++++++++- rust/kernel/error.rs | 5 +---- rust/kernel/firmware.rs | 2 +- rust/kernel/uaccess.rs | 27 +++++++-------------------- 4 files changed, 45 insertions(+), 26 deletions(-) --- 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; --- 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. --- 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 { --- 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::*, types::{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 { Patches currently in stable-queue which might be from ojeda@xxxxxxxxxx are queue-6.12/rust-fix-size_t-in-bindgen-prototypes-of-c-builtins.patch queue-6.12/rust-alloc-add-box-to-prelude.patch queue-6.12/drm-panic-correctly-indent-continuation-of-line-in-list-item.patch queue-6.12/rust-replace-clippy-dbg_macro-with-disallowed_macros.patch queue-6.12/rust-error-use-core-alloc-layouterror.patch queue-6.12/rust-alloc-add-allocator-trait.patch queue-6.12/rust-alloc-fix-arraylayout-allocations.patch queue-6.12/rust-alloc-update-module-comment-of-alloc.rs.patch queue-6.12/rust-map-__kernel_size_t-and-friends-also-to-usize-isize.patch queue-6.12/rust-sync-remove-unneeded.patch queue-6.12/drm-panic-remove-unnecessary-borrow-in-alignment_pattern.patch queue-6.12/rust-error-make-conversion-functions-public.patch queue-6.12/rust-alloc-implement-intoiterator-for-vec.patch queue-6.12/rust-alloc-introduce-arraylayout.patch queue-6.12/rust-alloc-implement-kernel-box.patch queue-6.12/rust-alloc-remove-vecext-extension.patch queue-6.12/rust-alloc-make-allocator-module-public.patch queue-6.12/rust-alloc-add-vec-to-prelude.patch queue-6.12/rust-alloc-implement-vmalloc-allocator.patch queue-6.12/rust-alloc-implement-collect-for-intoiter.patch queue-6.12/rust-enable-rustdoc-unescaped_backticks-lint.patch queue-6.12/rust-error-optimize-error-type-to-use-nonzero.patch queue-6.12/rust-treewide-switch-to-the-kernel-vec-type.patch queue-6.12/rust-alloc-implement-contains-for-flags.patch queue-6.12/rust-start-using-the-attribute.patch queue-6.12/rust-alloc-implement-cmalloc-in-module-allocator_test.patch queue-6.12/rust-introduce-.clippy.toml.patch queue-6.12/rust-alloc-implement-kernel-vec-type.patch queue-6.12/documentation-rust-discuss-in-the-guidelines.patch queue-6.12/rust-alloc-add-module-allocator_test.patch queue-6.12/rust-alloc-implement-allocator-for-kmalloc.patch queue-6.12/rust-treewide-switch-to-our-kernel-box-type.patch queue-6.12/rust-alloc-separate-aligned_size-from-krealloc_aligned.patch queue-6.12/rust-enable-clippy-unnecessary_safety_comment-lint.patch queue-6.12/rust-alloc-remove-extension-of-std-s-box.patch queue-6.12/rust-provide-proper-code-documentation-titles.patch queue-6.12/rust-str-test-replace-alloc-format.patch queue-6.12/rust-enable-clippy-s-check-private-items.patch queue-6.12/drm-panic-avoid-reimplementing-iterator-find.patch queue-6.12/drm-panic-allow-verbose-version-check.patch queue-6.12/rust-enable-clippy-undocumented_unsafe_blocks-lint.patch queue-6.12/rust-enable-clippy-unnecessary_safety_doc-lint.patch queue-6.12/rust-sort-global-rust-flags.patch queue-6.12/maintainers-add-entry-for-the-rust-alloc-module.patch queue-6.12/drm-panic-prefer-eliding-lifetimes.patch queue-6.12/documentation-rust-add-coding-guidelines-on-lints.patch queue-6.12/kbuild-rust-remove-the-alloc-crate-and-globalalloc.patch queue-6.12/rust-kbuild-expand-rusttest-target-for-macros.patch queue-6.12/drm-panic-allow-verbose-boolean-for-clarity.patch queue-6.12/rust-block-fix-formatting-in-gendisk-doc.patch queue-6.12/rust-alloc-add-__gfp_nowarn-to-flags.patch queue-6.12/drm-panic-remove-redundant-field-when-assigning-value.patch queue-6.12/rust-workqueue-remove-unneeded.patch queue-6.12/rust-use-custom-ffi-integer-types.patch queue-6.12/rust-alloc-implement-kvmalloc-allocator.patch queue-6.12/rust-alloc-implement-reallocfunc.patch queue-6.12/loongarch-use-asm_reachable.patch queue-6.12/rust-init-remove-unneeded.patch queue-6.12/rust-enable-clippy-ignored_unit_patterns-lint.patch queue-6.12/rust-map-long-to-isize-and-char-to-u8.patch queue-6.12/rust-alloc-rename-kernelallocator-to-kmalloc.patch queue-6.12/rust-finish-using-custom-ffi-integer-types.patch queue-6.12/rust-error-check-for-config-test-in-error-name.patch queue-6.12/rust-types-avoid-repetition-in-as-from-bytes-impls.patch
