Merge tag 'rust-6.7' of https://github.com/Rust-for-Linux/linux

Pull rust updates from Miguel Ojeda:
 "A small one compared to the previous one in terms of features. In
  terms of lines, as usual, the 'alloc' version upgrade accounts for
  most of them.

  Toolchain and infrastructure:

   - Upgrade to Rust 1.73.0

     This time around, due to how the kernel and Rust schedules have
     aligned, there are two upgrades in fact. They contain the fixes for
     a few issues we reported to the Rust project.

     In addition, a few cleanups indicated by the upgraded compiler or
     possible thanks to it. For instance, the compiler now detects
     redundant explicit links.

   - A couple changes to the Rust 'Makefile' so that it can be used with
     toybox tools, allowing Rust to be used in the Android kernel build.

  x86:

   - Enable IBT if enabled in C

  Documentation:

   - Add "The Rust experiment" section to the Rust index page

  MAINTAINERS:

   - Add Maintainer Entry Profile field ('P:').

   - Update our 'W:' field to point to the webpage we have been building
     this year"

* tag 'rust-6.7' of https://github.com/Rust-for-Linux/linux:
  docs: rust: add "The Rust experiment" section
  x86: Enable IBT in Rust if enabled in C
  rust: Use grep -Ev rather than relying on GNU grep
  rust: Use awk instead of recent xargs
  rust: upgrade to Rust 1.73.0
  rust: print: use explicit link in documentation
  rust: task: remove redundant explicit link
  rust: kernel: remove `#[allow(clippy::new_ret_no_self)]`
  MAINTAINERS: add Maintainer Entry Profile field for Rust
  MAINTAINERS: update Rust webpage
  rust: upgrade to Rust 1.72.1
  rust: arc: add explicit `drop()` around `Box::from_raw()`

Author: torvalds

Documentation/process/changes.rst

@@ -31,7 +31,7 @@ you probably needn't concern yourself with pcmciautils.
 ====================== ===============  ========================================
 GNU C                  5.1              gcc --version
 Clang/LLVM (optional)  11.0.0           clang --version
-Rust (optional)        1.71.1           rustc --version
+Rust (optional)        1.73.0           rustc --version
 bindgen (optional)     0.65.1           bindgen --version
 GNU make               3.82             make --version
 bash                   4.2              bash --version

Documentation/rust/index.rst

@@ -6,6 +6,25 @@ Rust
 Documentation related to Rust within the kernel. To start using Rust
 in the kernel, please read the quick-start.rst guide.
 
+
+The Rust experiment
+-------------------
+
+The Rust support was merged in v6.1 into mainline in order to help in
+determining whether Rust as a language was suitable for the kernel, i.e. worth
+the tradeoffs.
+
+Currently, the Rust support is primarily intended for kernel developers and
+maintainers interested in the Rust support, so that they can start working on
+abstractions and drivers, as well as helping the development of infrastructure
+and tools.
+
+If you are an end user, please note that there are currently no in-tree
+drivers/modules suitable or intended for production use, and that the Rust
+support is still in development/experimental, especially for certain kernel
+configurations.
+
+
 .. only:: rustdoc and html
 
 	You can also browse `rustdoc documentation <rustdoc/kernel/index.html>`_.

MAINTAINERS

@@ -18734,9 +18734,10 @@ R:	Andreas Hindborg <a.hindborg@samsung.com>
 R:	Alice Ryhl <aliceryhl@google.com>
 L:	rust-for-linux@vger.kernel.org
 S:	Supported
-W:	https://github.com/Rust-for-Linux/linux
+W:	https://rust-for-linux.com
 B:	https://github.com/Rust-for-Linux/linux/issues
 C:	zulip://rust-for-linux.zulipchat.com
+P:	https://rust-for-linux.com/contributing
 T:	git https://github.com/Rust-for-Linux/linux.git rust-next
 F:	Documentation/rust/
 F:	rust/

arch/x86/Makefile

@@ -81,6 +81,7 @@ ifeq ($(CONFIG_X86_KERNEL_IBT),y)
 #   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104816
 #
 KBUILD_CFLAGS += $(call cc-option,-fcf-protection=branch -fno-jump-tables)
+KBUILD_RUSTFLAGS += -Zcf-protection=branch -Zno-jump-tables
 else
 KBUILD_CFLAGS += $(call cc-option,-fcf-protection=none)
 endif

rust/Makefile

@@ -336,13 +336,13 @@ quiet_cmd_bindgen = BINDGEN $@
 		$(bindgen_target_cflags) $(bindgen_target_extra)
 
 $(obj)/bindings/bindings_generated.rs: private bindgen_target_flags = \
-    $(shell grep -v '^#\|^$$' $(srctree)/$(src)/bindgen_parameters)
+    $(shell grep -Ev '^#|^$$' $(srctree)/$(src)/bindgen_parameters)
 $(obj)/bindings/bindings_generated.rs: $(src)/bindings/bindings_helper.h \
     $(src)/bindgen_parameters FORCE
 	$(call if_changed_dep,bindgen)
 
 $(obj)/uapi/uapi_generated.rs: private bindgen_target_flags = \
-    $(shell grep -v '^#\|^$$' $(srctree)/$(src)/bindgen_parameters)
+    $(shell grep -Ev '^#|^$$' $(srctree)/$(src)/bindgen_parameters)
 $(obj)/uapi/uapi_generated.rs: $(src)/uapi/uapi_helper.h \
     $(src)/bindgen_parameters FORCE
 	$(call if_changed_dep,bindgen)
@@ -364,9 +364,7 @@ $(obj)/bindings/bindings_helpers_generated.rs: $(src)/helpers.c FORCE
 quiet_cmd_exports = EXPORTS $@
       cmd_exports = \
 	$(NM) -p --defined-only $< \
-		| grep -E ' (T|R|D) ' | cut -d ' ' -f 3 \
-		| xargs -Isymbol \
-		echo 'EXPORT_SYMBOL_RUST_GPL(symbol);' > $@
+		| awk '/ (T|R|D) / {printf "EXPORT_SYMBOL_RUST_GPL(%s);\n",$$3}' > $@
 
 $(obj)/exports_core_generated.h: $(obj)/core.o FORCE
 	$(call if_changed,exports)

rust/alloc/alloc.rs

@@ -6,9 +6,7 @@
 
 #[cfg(not(test))]
 use core::intrinsics;
-use core::intrinsics::{min_align_of_val, size_of_val};
 
-use core::ptr::Unique;
 #[cfg(not(test))]
 use core::ptr::{self, NonNull};
 
@@ -40,7 +38,6 @@ extern "Rust" {
     #[rustc_nounwind]
     fn __rust_alloc_zeroed(size: usize, align: usize) -> *mut u8;
 
-    #[cfg(not(bootstrap))]
     static __rust_no_alloc_shim_is_unstable: u8;
 }
 
@@ -98,7 +95,6 @@ pub unsafe fn alloc(layout: Layout) -> *mut u8 {
     unsafe {
         // Make sure we don't accidentally allow omitting the allocator shim in
         // stable code until it is actually stabilized.
-        #[cfg(not(bootstrap))]
         core::ptr::read_volatile(&__rust_no_alloc_shim_is_unstable);
 
         __rust_alloc(layout.size(), layout.align())
@@ -339,22 +335,6 @@ unsafe fn exchange_malloc(size: usize, align: usize) -> *mut u8 {
     }
 }
 
-#[cfg_attr(not(test), lang = "box_free")]
-#[inline]
-// This signature has to be the same as `Box`, otherwise an ICE will happen.
-// When an additional parameter to `Box` is added (like `A: Allocator`), this has to be added here as
-// well.
-// For example if `Box` is changed to  `struct Box<T: ?Sized, A: Allocator>(Unique<T>, A)`,
-// this function has to be changed to `fn box_free<T: ?Sized, A: Allocator>(Unique<T>, A)` as well.
-pub(crate) unsafe fn box_free<T: ?Sized, A: Allocator>(ptr: Unique<T>, alloc: A) {
-    unsafe {
-        let size = size_of_val(ptr.as_ref());
-        let align = min_align_of_val(ptr.as_ref());
-        let layout = Layout::from_size_align_unchecked(size, align);
-        alloc.deallocate(From::from(ptr.cast()), layout)
-    }
-}
-
 // # Allocation error handler
 
 #[cfg(not(no_global_oom_handling))]
@@ -414,7 +394,6 @@ pub mod __alloc_error_handler {
             static __rust_alloc_error_handler_should_panic: u8;
         }
 
-        #[allow(unused_unsafe)]
         if unsafe { __rust_alloc_error_handler_should_panic != 0 } {
             panic!("memory allocation of {size} bytes failed")
         } else {

rust/alloc/boxed.rs

@@ -159,12 +159,12 @@ use core::hash::{Hash, Hasher};
 use core::iter::FusedIterator;
 use core::marker::Tuple;
 use core::marker::Unsize;
-use core::mem;
+use core::mem::{self, SizedTypeProperties};
 use core::ops::{
     CoerceUnsized, Deref, DerefMut, DispatchFromDyn, Generator, GeneratorState, Receiver,
 };
 use core::pin::Pin;
-use core::ptr::{self, Unique};
+use core::ptr::{self, NonNull, Unique};
 use core::task::{Context, Poll};
 
 #[cfg(not(no_global_oom_handling))]
@@ -483,8 +483,12 @@ impl<T, A: Allocator> Box<T, A> {
     where
         A: Allocator,
     {
-        let layout = Layout::new::<mem::MaybeUninit<T>>();
-        let ptr = alloc.allocate(layout)?.cast();
+        let ptr = if T::IS_ZST {
+            NonNull::dangling()
+        } else {
+            let layout = Layout::new::<mem::MaybeUninit<T>>();
+            alloc.allocate(layout)?.cast()
+        };
         unsafe { Ok(Box::from_raw_in(ptr.as_ptr(), alloc)) }
     }
 
@@ -553,8 +557,12 @@ impl<T, A: Allocator> Box<T, A> {
     where
         A: Allocator,
     {
-        let layout = Layout::new::<mem::MaybeUninit<T>>();
-        let ptr = alloc.allocate_zeroed(layout)?.cast();
+        let ptr = if T::IS_ZST {
+            NonNull::dangling()
+        } else {
+            let layout = Layout::new::<mem::MaybeUninit<T>>();
+            alloc.allocate_zeroed(layout)?.cast()
+        };
         unsafe { Ok(Box::from_raw_in(ptr.as_ptr(), alloc)) }
     }
 
@@ -679,14 +687,16 @@ impl<T> Box<[T]> {
     #[unstable(feature = "allocator_api", issue = "32838")]
     #[inline]
     pub fn try_new_uninit_slice(len: usize) -> Result<Box<[mem::MaybeUninit<T>]>, AllocError> {
-        unsafe {
+        let ptr = if T::IS_ZST || len == 0 {
+            NonNull::dangling()
+        } else {
             let layout = match Layout::array::<mem::MaybeUninit<T>>(len) {
                 Ok(l) => l,
                 Err(_) => return Err(AllocError),
             };
-            let ptr = Global.allocate(layout)?;
-            Ok(RawVec::from_raw_parts_in(ptr.as_mut_ptr() as *mut _, len, Global).into_box(len))
-        }
+            Global.allocate(layout)?.cast()
+        };
+        unsafe { Ok(RawVec::from_raw_parts_in(ptr.as_ptr(), len, Global).into_box(len)) }
     }
 
     /// Constructs a new boxed slice with uninitialized contents, with the memory
@@ -711,14 +721,16 @@ impl<T> Box<[T]> {
     #[unstable(feature = "allocator_api", issue = "32838")]
     #[inline]
     pub fn try_new_zeroed_slice(len: usize) -> Result<Box<[mem::MaybeUninit<T>]>, AllocError> {
-        unsafe {
+        let ptr = if T::IS_ZST || len == 0 {
+            NonNull::dangling()
+        } else {
             let layout = match Layout::array::<mem::MaybeUninit<T>>(len) {
                 Ok(l) => l,
                 Err(_) => return Err(AllocError),
             };
-            let ptr = Global.allocate_zeroed(layout)?;
-            Ok(RawVec::from_raw_parts_in(ptr.as_mut_ptr() as *mut _, len, Global).into_box(len))
-        }
+            Global.allocate_zeroed(layout)?.cast()
+        };
+        unsafe { Ok(RawVec::from_raw_parts_in(ptr.as_ptr(), len, Global).into_box(len)) }
     }
 }
 
@@ -1215,8 +1227,18 @@ impl<T: ?Sized, A: Allocator> Box<T, A> {
 
 #[stable(feature = "rust1", since = "1.0.0")]
 unsafe impl<#[may_dangle] T: ?Sized, A: Allocator> Drop for Box<T, A> {
+    #[inline]
     fn drop(&mut self) {
-        // FIXME: Do nothing, drop is currently performed by compiler.
+        // the T in the Box is dropped by the compiler before the destructor is run
+
+        let ptr = self.0;
+
+        unsafe {
+            let layout = Layout::for_value_raw(ptr.as_ptr());
+            if layout.size() != 0 {
+                self.1.deallocate(From::from(ptr.cast()), layout);
+            }
+        }
     }
 }
 
@@ -2165,7 +2187,7 @@ impl dyn Error + Send {
         let err: Box<dyn Error> = self;
         <dyn Error>::downcast(err).map_err(|s| unsafe {
             // Reapply the `Send` marker.
-            mem::transmute::<Box<dyn Error>, Box<dyn Error + Send>>(s)
+            Box::from_raw(Box::into_raw(s) as *mut (dyn Error + Send))
         })
     }
 }
@@ -2179,7 +2201,7 @@ impl dyn Error + Send + Sync {
         let err: Box<dyn Error> = self;
         <dyn Error>::downcast(err).map_err(|s| unsafe {
             // Reapply the `Send + Sync` marker.
-            mem::transmute::<Box<dyn Error>, Box<dyn Error + Send + Sync>>(s)
+            Box::from_raw(Box::into_raw(s) as *mut (dyn Error + Send + Sync))
         })
     }
 }

rust/alloc/lib.rs

@@ -58,6 +58,11 @@
 //! [`Rc`]: rc
 //! [`RefCell`]: core::cell
 
+// To run alloc tests without x.py without ending up with two copies of alloc, Miri needs to be
+// able to "empty" this crate. See <https://github.com/rust-lang/miri-test-libstd/issues/4>.
+// rustc itself never sets the feature, so this line has no effect there.
+#![cfg(any(not(feature = "miri-test-libstd"), test, doctest))]
+//
 #![allow(unused_attributes)]
 #![stable(feature = "alloc", since = "1.36.0")]
 #![doc(
@@ -77,11 +82,6 @@
 ))]
 #![no_std]
 #![needs_allocator]
-// To run alloc tests without x.py without ending up with two copies of alloc, Miri needs to be
-// able to "empty" this crate. See <https://github.com/rust-lang/miri-test-libstd/issues/4>.
-// rustc itself never sets the feature, so this line has no affect there.
-#![cfg(any(not(feature = "miri-test-libstd"), test, doctest))]
-//
 // Lints:
 #![deny(unsafe_op_in_unsafe_fn)]
 #![deny(fuzzy_provenance_casts)]
@@ -90,6 +90,8 @@
 #![warn(missing_docs)]
 #![allow(explicit_outlives_requirements)]
 #![warn(multiple_supertrait_upcastable)]
+#![cfg_attr(not(bootstrap), allow(internal_features))]
+#![cfg_attr(not(bootstrap), allow(rustdoc::redundant_explicit_links))]
 //
 // Library features:
 // tidy-alphabetical-start
@@ -139,7 +141,6 @@
 #![feature(maybe_uninit_uninit_array_transpose)]
 #![feature(pattern)]
 #![feature(pointer_byte_offsets)]
-#![feature(provide_any)]
 #![feature(ptr_internals)]
 #![feature(ptr_metadata)]
 #![feature(ptr_sub_ptr)]

rust/alloc/raw_vec.rs

@@ -471,16 +471,26 @@ impl<T, A: Allocator> RawVec<T, A> {
         let (ptr, layout) = if let Some(mem) = self.current_memory() { mem } else { return Ok(()) };
         // See current_memory() why this assert is here
         let _: () = const { assert!(mem::size_of::<T>() % mem::align_of::<T>() == 0) };
-        let ptr = unsafe {
-            // `Layout::array` cannot overflow here because it would have
-            // overflowed earlier when capacity was larger.
-            let new_size = mem::size_of::<T>().unchecked_mul(cap);
-            let new_layout = Layout::from_size_align_unchecked(new_size, layout.align());
-            self.alloc
-                .shrink(ptr, layout, new_layout)
-                .map_err(|_| AllocError { layout: new_layout, non_exhaustive: () })?
-        };
-        self.set_ptr_and_cap(ptr, cap);
+
+        // If shrinking to 0, deallocate the buffer. We don't reach this point
+        // for the T::IS_ZST case since current_memory() will have returned
+        // None.
+        if cap == 0 {
+            unsafe { self.alloc.deallocate(ptr, layout) };
+            self.ptr = Unique::dangling();
+            self.cap = 0;
+        } else {
+            let ptr = unsafe {
+                // `Layout::array` cannot overflow here because it would have
+                // overflowed earlier when capacity was larger.
+                let new_size = mem::size_of::<T>().unchecked_mul(cap);
+                let new_layout = Layout::from_size_align_unchecked(new_size, layout.align());
+                self.alloc
+                    .shrink(ptr, layout, new_layout)
+                    .map_err(|_| AllocError { layout: new_layout, non_exhaustive: () })?
+            };
+            self.set_ptr_and_cap(ptr, cap);
+        }
         Ok(())
     }
 }