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: <20240723-linked-list-v3-7-89db92c7dbf4@google.com>
Date: Tue, 23 Jul 2024 08:22:08 +0000
From: Alice Ryhl <aliceryhl@...gle.com>
To: Miguel Ojeda <ojeda@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>
Cc: Alex Gaynor <alex.gaynor@...il.com>, Wedson Almeida Filho <wedsonaf@...il.com>, 
	Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>, 
	"Björn Roy Baron" <bjorn3_gh@...tonmail.com>, Benno Lossin <benno.lossin@...ton.me>, 
	Andreas Hindborg <a.hindborg@...sung.com>, Marco Elver <elver@...gle.com>, Coly Li <colyli@...e.de>, 
	Paolo Abeni <pabeni@...hat.com>, Pierre Gondois <pierre.gondois@....com>, 
	Ingo Molnar <mingo@...nel.org>, Jakub Kicinski <kuba@...nel.org>, Wei Yang <richard.weiyang@...il.com>, 
	Matthew Wilcox <willy@...radead.org>, linux-kernel@...r.kernel.org, 
	rust-for-linux@...r.kernel.org, Alice Ryhl <aliceryhl@...gle.com>, 
	Kees Cook <kees@...nel.org>
Subject: [PATCH v3 07/10] rust: list: add iterators

Rust Binder has lists containing stuff such as all contexts or all
processes, and sometimes needs to iterate over them. This patch enables
Rust Binder to do that using a normal for loop.

The iterator returns the ArcBorrow type, so it is possible to grab a
refcount to values while iterating.

Reviewed-by: Benno Lossin <benno.lossin@...ton.me>
Signed-off-by: Alice Ryhl <aliceryhl@...gle.com>
---
 rust/kernel/list.rs | 102 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 102 insertions(+)

diff --git a/rust/kernel/list.rs b/rust/kernel/list.rs
index d3f8e38d9ff4..e320da063c07 100644
--- a/rust/kernel/list.rs
+++ b/rust/kernel/list.rs
@@ -5,7 +5,9 @@
 //! A linked list implementation.
 
 use crate::init::PinInit;
+use crate::sync::ArcBorrow;
 use crate::types::Opaque;
+use core::iter::{DoubleEndedIterator, FusedIterator};
 use core::marker::PhantomData;
 use core::ptr;
 
@@ -436,6 +438,17 @@ pub fn push_all_back(&mut self, other: &mut List<T, ID>) {
         // INVARIANT: The other list is now empty, so update its pointer.
         other.first = ptr::null_mut();
     }
+
+    /// Creates an iterator over the list.
+    pub fn iter(&self) -> Iter<'_, T, ID> {
+        // INVARIANT: If the list is empty, both pointers are null. Otherwise, both pointers point
+        // at the first element of the same list.
+        Iter {
+            current: self.first,
+            stop: self.first,
+            _ty: PhantomData,
+        }
+    }
 }
 
 impl<T: ?Sized + ListItem<ID>, const ID: u64> Default for List<T, ID> {
@@ -451,3 +464,92 @@ fn drop(&mut self) {
         }
     }
 }
+
+/// An iterator over a [`List`].
+///
+/// # Invariants
+///
+/// * There must be a [`List`] that is immutably borrowed for the duration of `'a`.
+/// * The `current` pointer is null or points at a value in that [`List`].
+/// * The `stop` pointer is equal to the `first` field of that [`List`].
+#[derive(Clone)]
+pub struct Iter<'a, T: ?Sized + ListItem<ID>, const ID: u64 = 0> {
+    current: *mut ListLinksFields,
+    stop: *mut ListLinksFields,
+    _ty: PhantomData<&'a ListArc<T, ID>>,
+}
+
+impl<'a, T: ?Sized + ListItem<ID>, const ID: u64> Iterator for Iter<'a, T, ID> {
+    type Item = ArcBorrow<'a, T>;
+
+    fn next(&mut self) -> Option<ArcBorrow<'a, T>> {
+        if self.current.is_null() {
+            return None;
+        }
+
+        let current = self.current;
+
+        // SAFETY: We just checked that `current` is not null, so it is in a list, and hence not
+        // dangling. There's no race because the iterator holds an immutable borrow to the list.
+        let next = unsafe { (*current).next };
+        // INVARIANT: If `current` was the last element of the list, then this updates it to null.
+        // Otherwise, we update it to the next element.
+        self.current = if next != self.stop {
+            next
+        } else {
+            ptr::null_mut()
+        };
+
+        // SAFETY: The `current` pointer points at a value in the list.
+        let item = unsafe { T::view_value(ListLinks::from_fields(current)) };
+        // SAFETY:
+        // * All values in a list are stored in an `Arc`.
+        // * The value cannot be removed from the list for the duration of the lifetime annotated
+        //   on the returned `ArcBorrow`, because removing it from the list would require mutable
+        //   access to the list. However, the `ArcBorrow` is annotated with the iterator's
+        //   lifetime, and the list is immutably borrowed for that lifetime.
+        // * Values in a list never have a `UniqueArc` reference.
+        Some(unsafe { ArcBorrow::from_raw(item) })
+    }
+}
+
+impl<'a, T: ?Sized + ListItem<ID>, const ID: u64> FusedIterator for Iter<'a, T, ID> {}
+
+impl<'a, T: ?Sized + ListItem<ID>, const ID: u64> IntoIterator for &'a List<T, ID> {
+    type IntoIter = Iter<'a, T, ID>;
+    type Item = ArcBorrow<'a, T>;
+
+    fn into_iter(self) -> Iter<'a, T, ID> {
+        self.iter()
+    }
+}
+
+/// An owning iterator into a [`List`].
+pub struct IntoIter<T: ?Sized + ListItem<ID>, const ID: u64 = 0> {
+    list: List<T, ID>,
+}
+
+impl<T: ?Sized + ListItem<ID>, const ID: u64> Iterator for IntoIter<T, ID> {
+    type Item = ListArc<T, ID>;
+
+    fn next(&mut self) -> Option<ListArc<T, ID>> {
+        self.list.pop_front()
+    }
+}
+
+impl<T: ?Sized + ListItem<ID>, const ID: u64> FusedIterator for IntoIter<T, ID> {}
+
+impl<T: ?Sized + ListItem<ID>, const ID: u64> DoubleEndedIterator for IntoIter<T, ID> {
+    fn next_back(&mut self) -> Option<ListArc<T, ID>> {
+        self.list.pop_back()
+    }
+}
+
+impl<T: ?Sized + ListItem<ID>, const ID: u64> IntoIterator for List<T, ID> {
+    type IntoIter = IntoIter<T, ID>;
+    type Item = ListArc<T, ID>;
+
+    fn into_iter(self) -> IntoIter<T, ID> {
+        IntoIter { list: self }
+    }
+}

-- 
2.45.2.1089.g2a221341d9-goog


Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ