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()`

1 files changed, 39 insertions, 17 deletions

diff --git a/rust/alloc/boxed.rs b/rust/alloc/boxed.rs
index c8173cea8317..9620eba17268 100644
--- a/rust/alloc/boxed.rs
+++ b/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))
         })
     }
 }