Merge tag 'rust-6.10' of https://github.com/Rust-for-Linux/linux

Pull Rust updates from Miguel Ojeda:
 "The most notable change is the drop of the 'alloc' in-tree fork. This
  is nicely reflected in the diffstat as a ~10k lines drop. In turn,
  this makes the version upgrades way simpler and smaller in the future,
  e.g. the latest one in commit 56f64b370612 ("rust: upgrade to Rust
  1.78.0").

  More importantly, this increases the chances that a newer compiler
  version just works, which in turn means supporting several compiler
  versions is easier now. Thus we will look into finally setting a
  minimum version in the near future.

  Toolchain and infrastructure:

   - Upgrade to Rust 1.78.0

     This time around, due to how the kernel and Rust schedules have
     aligned, there are two upgrades in fact. These allow us to remove
     one more unstable feature ('offset_of') from the list, among other
     improvements

   - Drop 'alloc' in-tree fork of the standard library crate, which
     means all the unstable features used by 'alloc' (~30 language ones,
     ~60 library ones) are not a concern anymore

   - Support DWARFv5 via the '-Zdwarf-version' flag

   - Support zlib and zstd debuginfo compression via the
     '-Zdebuginfo-compression' flag

  'kernel' crate:

   - Support allocation flags ('GFP_*'), particularly in 'Box' (via
     'BoxExt'), 'Vec' (via 'VecExt'), 'Arc' and 'UniqueArc', as well as
     in the 'init' module APIs

   - Remove usage of the 'allocator_api' unstable feature

   - Remove 'try_' prefix in allocation APIs' names

   - Add 'VecExt' (an extension trait) to be able to drop the 'alloc'
     fork

   - Add the '{make,to}_{upper,lower}case()' methods to 'CStr'/'CString'

   - Add the 'as_ptr' method to 'ThisModule'

   - Add the 'from_raw' method to 'ArcBorrow'

   - Add the 'into_unique_or_drop' method to 'Arc'

   - Display column number in the 'dbg!' macro output by applying the
     equivalent change done to the standard library one

   - Migrate 'Work' to '#[pin_data]' thanks to the changes in the
     'macros' crate, which allows to remove an unsafe call in its 'new'
     associated function

   - Prevent namespacing issues when using the '[try_][pin_]init!'
     macros by changing the generated name of guard variables

   - Make the 'get' method in 'Opaque' const

   - Implement the 'Default' trait for 'LockClassKey'

   - Remove unneeded 'kernel::prelude' imports from doctests

   - Remove redundant imports

  'macros' crate:

   - Add 'decl_generics' to 'parse_generics()' to support default
     values, and use that to allow them in '#[pin_data]'

  Helpers:

   - Trivial English grammar fix

  Documentation:

   - Add section on Rust Kselftests to the 'Testing' document

   - Expand the 'Abstractions vs. bindings' section of the 'General
     Information' document"

* tag 'rust-6.10' of https://github.com/Rust-for-Linux/linux: (31 commits)
  rust: alloc: fix dangling pointer in VecExt<T>::reserve()
  rust: upgrade to Rust 1.78.0
  rust: kernel: remove redundant imports
  rust: sync: implement `Default` for `LockClassKey`
  docs: rust: extend abstraction and binding documentation
  docs: rust: Add instructions for the Rust kselftest
  rust: remove unneeded `kernel::prelude` imports from doctests
  rust: update `dbg!()` to format column number
  rust: helpers: Fix grammar in comment
  rust: init: change the generated name of guard variables
  rust: sync: add `Arc::into_unique_or_drop`
  rust: sync: add `ArcBorrow::from_raw`
  rust: types: Make Opaque::get const
  rust: kernel: remove usage of `allocator_api` unstable feature
  rust: init: update `init` module to take allocation flags
  rust: sync: update `Arc` and `UniqueArc` to take allocation flags
  rust: alloc: update `VecExt` to take allocation flags
  rust: alloc: introduce the `BoxExt` trait
  rust: alloc: introduce allocation flags
  rust: alloc: remove our fork of the `alloc` crate
  ...

3 files changed, 319 insertions, 0 deletions

diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs
new file mode 100644
index 000000000000..229642960cd1
--- /dev/null
+++ b/rust/kernel/alloc/allocator.rs
@@ -0,0 +1,81 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Allocator support.
+
+use super::{flags::*, Flags};
+use core::alloc::{GlobalAlloc, Layout};
+use core::ptr;
+
+struct KernelAllocator;
+
+/// Calls `krealloc` with a proper size to alloc a new object aligned to `new_layout`'s alignment.
+///
+/// # Safety
+///
+/// - `ptr` can be either null or a pointer which has been allocated by this allocator.
+/// - `new_layout` must have a non-zero size.
+pub(crate) unsafe fn krealloc_aligned(ptr: *mut u8, new_layout: Layout, flags: Flags) -> *mut u8 {
+    // Customized layouts from `Layout::from_size_align()` can have size < align, so pad first.
+    let layout = new_layout.pad_to_align();
+
+    let mut size = layout.size();
+
+    if layout.align() > bindings::ARCH_SLAB_MINALIGN {
+        // The alignment requirement exceeds the slab guarantee, thus try to enlarge the size
+        // to use the "power-of-two" size/alignment guarantee (see comments in `kmalloc()` for
+        // more information).
+        //
+        // Note that `layout.size()` (after padding) is guaranteed to be a multiple of
+        // `layout.align()`, so `next_power_of_two` gives enough alignment guarantee.
+        size = size.next_power_of_two();
+    }
+
+    // SAFETY:
+    // - `ptr` is either null or a pointer returned from a previous `k{re}alloc()` by the
+    //   function safety requirement.
+    // - `size` is greater than 0 since it's either a `layout.size()` (which cannot be zero
+    //   according to the function safety requirement) or a result from `next_power_of_two()`.
+    unsafe { bindings::krealloc(ptr as *const core::ffi::c_void, size, flags.0) as *mut u8 }
+}
+
+unsafe impl GlobalAlloc for KernelAllocator {
+    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
+        // SAFETY: `ptr::null_mut()` is null and `layout` has a non-zero size by the function safety
+        // requirement.
+        unsafe { krealloc_aligned(ptr::null_mut(), layout, GFP_KERNEL) }
+    }
+
+    unsafe fn dealloc(&self, ptr: *mut u8, _layout: Layout) {
+        unsafe {
+            bindings::kfree(ptr as *const core::ffi::c_void);
+        }
+    }
+
+    unsafe fn realloc(&self, ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 {
+        // SAFETY:
+        // - `new_size`, when rounded up to the nearest multiple of `layout.align()`, will not
+        //   overflow `isize` by the function safety requirement.
+        // - `layout.align()` is a proper alignment (i.e. not zero and must be a power of two).
+        let layout = unsafe { Layout::from_size_align_unchecked(new_size, layout.align()) };
+
+        // SAFETY:
+        // - `ptr` is either null or a pointer allocated by this allocator by the function safety
+        //   requirement.
+        // - the size of `layout` is not zero because `new_size` is not zero by the function safety
+        //   requirement.
+        unsafe { krealloc_aligned(ptr, layout, GFP_KERNEL) }
+    }
+
+    unsafe fn alloc_zeroed(&self, layout: Layout) -> *mut u8 {
+        // SAFETY: `ptr::null_mut()` is null and `layout` has a non-zero size by the function safety
+        // requirement.
+        unsafe { krealloc_aligned(ptr::null_mut(), layout, GFP_KERNEL | __GFP_ZERO) }
+    }
+}
+
+#[global_allocator]
+static ALLOCATOR: KernelAllocator = KernelAllocator;
+
+// See <https://github.com/rust-lang/rust/pull/86844>.
+#[no_mangle]
+static __rust_no_alloc_shim_is_unstable: u8 = 0;
diff --git a/rust/kernel/alloc/box_ext.rs b/rust/kernel/alloc/box_ext.rs
new file mode 100644
index 000000000000..829cb1c1cf9e
--- /dev/null
+++ b/rust/kernel/alloc/box_ext.rs
@@ -0,0 +1,56 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Extensions to [`Box`] for fallible allocations.
+
+use super::{AllocError, Flags};
+use alloc::boxed::Box;
+use core::mem::MaybeUninit;
+
+/// Extensions to [`Box`].
+pub trait BoxExt<T>: Sized {
+    /// Allocates a new box.
+    ///
+    /// The allocation may fail, in which case an error is returned.
+    fn new(x: T, flags: Flags) -> Result<Self, AllocError>;
+
+    /// Allocates a new uninitialised box.
+    ///
+    /// The allocation may fail, in which case an error is returned.
+    fn new_uninit(flags: Flags) -> Result<Box<MaybeUninit<T>>, AllocError>;
+}
+
+impl<T> BoxExt<T> for Box<T> {
+    fn new(x: T, flags: Flags) -> Result<Self, AllocError> {
+        let b = <Self as BoxExt<_>>::new_uninit(flags)?;
+        Ok(Box::write(b, x))
+    }
+
+    #[cfg(any(test, testlib))]
+    fn new_uninit(_flags: Flags) -> Result<Box<MaybeUninit<T>>, AllocError> {
+        Ok(Box::new_uninit())
+    }
+
+    #[cfg(not(any(test, testlib)))]
+    fn new_uninit(flags: Flags) -> Result<Box<MaybeUninit<T>>, AllocError> {
+        let ptr = if core::mem::size_of::<MaybeUninit<T>>() == 0 {
+            core::ptr::NonNull::<_>::dangling().as_ptr()
+        } else {
+            let layout = core::alloc::Layout::new::<MaybeUninit<T>>();
+
+            // SAFETY: Memory is being allocated (first arg is null). The only other source of
+            // safety issues is sleeping on atomic context, which is addressed by klint. Lastly,
+            // the type is not a SZT (checked above).
+            let ptr =
+                unsafe { super::allocator::krealloc_aligned(core::ptr::null_mut(), layout, flags) };
+            if ptr.is_null() {
+                return Err(AllocError);
+            }
+
+            ptr.cast::<MaybeUninit<T>>()
+        };
+
+        // SAFETY: For non-zero-sized types, we allocate above using the global allocator. For
+        // zero-sized types, we use `NonNull::dangling`.
+        Ok(unsafe { Box::from_raw(ptr) })
+    }
+}
diff --git a/rust/kernel/alloc/vec_ext.rs b/rust/kernel/alloc/vec_ext.rs
new file mode 100644
index 000000000000..e9a81052728a
--- /dev/null
+++ b/rust/kernel/alloc/vec_ext.rs
@@ -0,0 +1,182 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Extensions to [`Vec`] for fallible allocations.
+
+use super::{AllocError, Flags};
+use alloc::vec::Vec;
+use core::ptr;
+
+/// Extensions to [`Vec`].
+pub trait VecExt<T>: Sized {
+    /// Creates a new [`Vec`] instance with at least the given capacity.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let v = Vec::<u32>::with_capacity(20, GFP_KERNEL)?;
+    ///
+    /// assert!(v.capacity() >= 20);
+    /// # Ok::<(), Error>(())
+    /// ```
+    fn with_capacity(capacity: usize, flags: Flags) -> Result<Self, AllocError>;
+
+    /// Appends an element to the back of the [`Vec`] instance.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let mut v = Vec::new();
+    /// v.push(1, GFP_KERNEL)?;
+    /// assert_eq!(&v, &[1]);
+    ///
+    /// v.push(2, GFP_KERNEL)?;
+    /// assert_eq!(&v, &[1, 2]);
+    /// # Ok::<(), Error>(())
+    /// ```
+    fn push(&mut self, v: T, flags: Flags) -> Result<(), AllocError>;
+
+    /// Pushes clones of the elements of slice into the [`Vec`] instance.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let mut v = Vec::new();
+    /// v.push(1, GFP_KERNEL)?;
+    ///
+    /// v.extend_from_slice(&[20, 30, 40], GFP_KERNEL)?;
+    /// assert_eq!(&v, &[1, 20, 30, 40]);
+    ///
+    /// v.extend_from_slice(&[50, 60], GFP_KERNEL)?;
+    /// assert_eq!(&v, &[1, 20, 30, 40, 50, 60]);
+    /// # Ok::<(), Error>(())
+    /// ```
+    fn extend_from_slice(&mut self, other: &[T], flags: Flags) -> Result<(), AllocError>
+    where
+        T: Clone;
+
+    /// Ensures that the capacity exceeds the length by at least `additional` elements.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let mut v = Vec::new();
+    /// v.push(1, GFP_KERNEL)?;
+    ///
+    /// v.reserve(10, GFP_KERNEL)?;
+    /// let cap = v.capacity();
+    /// assert!(cap >= 10);
+    ///
+    /// v.reserve(10, GFP_KERNEL)?;
+    /// let new_cap = v.capacity();
+    /// assert_eq!(new_cap, cap);
+    ///
+    /// # Ok::<(), Error>(())
+    /// ```
+    fn reserve(&mut self, additional: usize, flags: Flags) -> Result<(), AllocError>;
+}
+
+impl<T> VecExt<T> for Vec<T> {
+    fn with_capacity(capacity: usize, flags: Flags) -> Result<Self, AllocError> {
+        let mut v = Vec::new();
+        <Self as VecExt<_>>::reserve(&mut v, capacity, flags)?;
+        Ok(v)
+    }
+
+    fn push(&mut self, v: T, flags: Flags) -> Result<(), AllocError> {
+        <Self as VecExt<_>>::reserve(self, 1, flags)?;
+        let s = self.spare_capacity_mut();
+        s[0].write(v);
+
+        // SAFETY: We just initialised the first spare entry, so it is safe to increase the length
+        // by 1. We also know that the new length is <= capacity because of the previous call to
+        // `reserve` above.
+        unsafe { self.set_len(self.len() + 1) };
+        Ok(())
+    }
+
+    fn extend_from_slice(&mut self, other: &[T], flags: Flags) -> Result<(), AllocError>
+    where
+        T: Clone,
+    {
+        <Self as VecExt<_>>::reserve(self, other.len(), flags)?;
+        for (slot, item) in core::iter::zip(self.spare_capacity_mut(), other) {
+            slot.write(item.clone());
+        }
+
+        // SAFETY: We just initialised the `other.len()` spare entries, so it is safe to increase
+        // the length by the same amount. We also know that the new length is <= capacity because
+        // of the previous call to `reserve` above.
+        unsafe { self.set_len(self.len() + other.len()) };
+        Ok(())
+    }
+
+    #[cfg(any(test, testlib))]
+    fn reserve(&mut self, additional: usize, _flags: Flags) -> Result<(), AllocError> {
+        Vec::reserve(self, additional);
+        Ok(())
+    }
+
+    #[cfg(not(any(test, testlib)))]
+    fn reserve(&mut self, additional: usize, flags: Flags) -> Result<(), AllocError> {
+        let len = self.len();
+        let cap = self.capacity();
+
+        if cap - len >= additional {
+            return Ok(());
+        }
+
+        if core::mem::size_of::<T>() == 0 {
+            // The capacity is already `usize::MAX` for SZTs, we can't go higher.
+            return Err(AllocError);
+        }
+
+        // We know cap is <= `isize::MAX` because `Layout::array` fails if the resulting byte size
+        // is greater than `isize::MAX`. So the multiplication by two won't overflow.
+        let new_cap = core::cmp::max(cap * 2, len.checked_add(additional).ok_or(AllocError)?);
+        let layout = core::alloc::Layout::array::<T>(new_cap).map_err(|_| AllocError)?;
+
+        let (old_ptr, len, cap) = destructure(self);
+
+        // We need to make sure that `ptr` is either NULL or comes from a previous call to
+        // `krealloc_aligned`. A `Vec<T>`'s `ptr` value is not guaranteed to be NULL and might be
+        // dangling after being created with `Vec::new`. Instead, we can rely on `Vec<T>`'s capacity
+        // to be zero if no memory has been allocated yet.
+        let ptr = if cap == 0 { ptr::null_mut() } else { old_ptr };
+
+        // SAFETY: `ptr` is valid because it's either NULL or comes from a previous call to
+        // `krealloc_aligned`. We also verified that the type is not a ZST.
+        let new_ptr = unsafe { super::allocator::krealloc_aligned(ptr.cast(), layout, flags) };
+        if new_ptr.is_null() {
+            // SAFETY: We are just rebuilding the existing `Vec` with no changes.
+            unsafe { rebuild(self, old_ptr, len, cap) };
+            Err(AllocError)
+        } else {
+            // SAFETY: `ptr` has been reallocated with the layout for `new_cap` elements. New cap
+            // is greater than `cap`, so it continues to be >= `len`.
+            unsafe { rebuild(self, new_ptr.cast::<T>(), len, new_cap) };
+            Ok(())
+        }
+    }
+}
+
+#[cfg(not(any(test, testlib)))]
+fn destructure<T>(v: &mut Vec<T>) -> (*mut T, usize, usize) {
+    let mut tmp = Vec::new();
+    core::mem::swap(&mut tmp, v);
+    let mut tmp = core::mem::ManuallyDrop::new(tmp);
+    let len = tmp.len();
+    let cap = tmp.capacity();
+    (tmp.as_mut_ptr(), len, cap)
+}
+
+/// Rebuilds a `Vec` from a pointer, length, and capacity.
+///
+/// # Safety
+///
+/// The same as [`Vec::from_raw_parts`].
+#[cfg(not(any(test, testlib)))]
+unsafe fn rebuild<T>(v: &mut Vec<T>, ptr: *mut T, len: usize, cap: usize) {
+    // SAFETY: The safety requirements from this function satisfy those of `from_raw_parts`.
+    let mut tmp = unsafe { Vec::from_raw_parts(ptr, len, cap) };
+    core::mem::swap(&mut tmp, v);
+}