linux-kernel - [PATCH v4 6/7] rust: alloc: add Vec::remove

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250429-vec-methods-v4-6-dad4436ff82d@google.com>
Date: Tue, 29 Apr 2025 14:44:26 +0000
From: Alice Ryhl <aliceryhl@...gle.com>
To: Danilo Krummrich <dakr@...nel.org>
Cc: Matthew Maurer <mmaurer@...gle.com>, rust-for-linux@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Alice Ryhl <aliceryhl@...gle.com>
Subject: [PATCH v4 6/7] rust: alloc: add Vec::remove

This is needed by Rust Binder in the range allocator, and by upcoming
GPU drivers during firmware initialization.

Signed-off-by: Alice Ryhl <aliceryhl@...gle.com>
---
 rust/kernel/alloc/kvec.rs | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/rust/kernel/alloc/kvec.rs b/rust/kernel/alloc/kvec.rs
index 357f5a37c7b1d15b709a10c162292841eed0e376..0682108951675cbee05faa130e5a9ce72fc343ba 100644
--- a/rust/kernel/alloc/kvec.rs
+++ b/rust/kernel/alloc/kvec.rs
@@ -386,6 +386,42 @@ pub fn pop(&mut self) -> Option<T> {
         Some(unsafe { removed.read() })
     }
 
+    /// Removes the element at the given index.
+    ///
+    /// # Panics
+    ///
+    /// Panics if the index is out of bounds.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let mut v = kernel::kvec![1, 2, 3]?;
+    /// assert_eq!(v.remove(1), 2);
+    /// assert_eq!(v, [1, 3]);
+    /// # Ok::<(), Error>(())
+    /// ```
+    pub fn remove(&mut self, i: usize) -> T {
+        // INVARIANT: This breaks the invariants by invalidating the value at index `i`, but we
+        // restore the invariants below.
+        // SAFETY: Since `&self[i]` did not result in a panic, the value at index `i` is valid.
+        let value = unsafe { ptr::read(&self[i]) };
+
+        // SAFETY: We checked that `i` is in-bounds.
+        let p = unsafe { self.as_mut_ptr().add(i) };
+
+        // INVARIANT: After this call, the invalid value is at the last slot, so the Vec invariants
+        // are restored after the below call to `dec_len(1)`.
+        // SAFETY: `p.add(1).add(self.len - i - 1)` is `i+1+len-i-1 == len` elements after the
+        // beginning of the vector, so this is in-bounds of the vector's allocation.
+        unsafe { ptr::copy(p.add(1), p, self.len - i - 1) };
+
+        // SAFETY: Since the access at the beginning of this call did not panic, the length is at
+        // least one.
+        unsafe { self.dec_len(1) };
+
+        value
+    }
+
     /// Creates a new [`Vec`] instance with at least the given capacity.
     ///
     /// # Examples

-- 
2.49.0.901.g37484f566f-goog