OpenE2K
/
rust
2
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

Make functions dependent only on shared root avoidance safe

This commit is contained in:
Mark Rousskov 2020-03-18 10:45:35 -04:00
parent 1c44f852df
commit 3c04fda751
3 changed files with 58 additions and 58 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
src/liballoc/collections/btree/map.rs
View File

@ -1349,7 +1349,8 @@ impl<K: Ord, V> BTreeMap<K, V> {
self.fix_top();
}
/// If the root node is the shared root node, allocate our own node.
/// If the root node is the empty (non-allocated) root node, allocate our
/// own node.
fn ensure_root_is_owned(&mut self) {
if self.root.is_none() {
self.root = Some(node::Root::new_leaf());
@ -1509,7 +1510,6 @@ impl<K, V> Drop for IntoIter<K, V> {
// don't have to care about panics this time (they'll abort).
while let Some(_) = self.0.next() {}
// No need to avoid the shared root, because the tree was definitely not empty.
unsafe {
let mut node =
unwrap_unchecked(ptr::read(&self.0.front)).into_node().forget_type();

107
src/liballoc/collections/btree/node.rs
View File

@ -169,8 +169,9 @@ impl<K, V> BoxedNode<K, V> {
}
}
/// Either an owned tree or a shared, empty tree. Note that this does not have a destructor,
/// and must be cleaned up manually if it is an owned tree.
/// An owned tree.
///
/// Note that this does not have a destructor, and must be cleaned up manually.
pub struct Root<K, V> {
node: BoxedNode<K, V>,
/// The number of levels below the root node.
@ -278,10 +279,7 @@ impl<K, V> Root<K, V> {
/// `Leaf`, the `NodeRef` points to a leaf node, when this is `Internal` the
/// `NodeRef` points to an internal node, and when this is `LeafOrInternal` the
/// `NodeRef` could be pointing to either type of node.
/// Note that in case of a leaf node, this might still be the shared root!
/// Only turn this into a `LeafNode` reference if you know it is not the shared root!
/// Shared references must be dereferenceable *for the entire size of their pointee*,
/// so '&LeafNode` or `&InternalNode` pointing to the shared root is undefined behavior.
///
/// Turning this into a `NodeHeader` reference is always safe.
pub struct NodeRef<BorrowType, K, V, Type> {
/// The number of levels below the node.
@ -344,14 +342,15 @@ impl<BorrowType, K, V, Type> NodeRef<BorrowType, K, V, Type> {
NodeRef { height: self.height, node: self.node, root: self.root, _marker: PhantomData }
}
/// Exposes the leaf "portion" of any leaf or internal node that is not the shared root.
/// Exposes the leaf "portion" of any leaf or internal node.
/// If the node is a leaf, this function simply opens up its data.
/// If the node is an internal node, so not a leaf, it does have all the data a leaf has
/// (header, keys and values), and this function exposes that.
/// Unsafe because the node must not be the shared root. For more information,
/// see the `NodeRef` comments.
unsafe fn as_leaf(&self) -> &LeafNode<K, V> {
self.node.as_ref()
fn as_leaf(&self) -> &LeafNode<K, V> {
// The node must be valid for at least the LeafNode portion.
// This is not a reference in the NodeRef type because we don't know if
// it should be unique or shared.
unsafe { self.node.as_ref() }
}
fn as_header(&self) -> &NodeHeader<K, V> {
@ -359,14 +358,12 @@ impl<BorrowType, K, V, Type> NodeRef<BorrowType, K, V, Type> {
}
/// Borrows a view into the keys stored in the node.
/// Unsafe because the caller must ensure that the node is not the shared root.
pub unsafe fn keys(&self) -> &[K] {
pub fn keys(&self) -> &[K] {
self.reborrow().into_key_slice()
}
/// Borrows a view into the values stored in the node.
/// Unsafe because the caller must ensure that the node is not the shared root.
unsafe fn vals(&self) -> &[V] {
fn vals(&self) -> &[V] {
self.reborrow().into_val_slice()
}
@ -470,39 +467,37 @@ impl<'a, K, V, Type> NodeRef<marker::Mut<'a>, K, V, Type> {
/// (header, keys and values), and this function exposes that.
///
/// Returns a raw ptr to avoid asserting exclusive access to the entire node.
/// This also implies you can invoke this member on the shared root, but the resulting pointer
/// might not be properly aligned and definitely would not allow accessing keys and values.
fn as_leaf_mut(&mut self) -> *mut LeafNode<K, V> {
self.node.as_ptr()
}
/// Unsafe because the caller must ensure that the node is not the shared root.
unsafe fn keys_mut(&mut self) -> &mut [K] {
self.reborrow_mut().into_key_slice_mut()
fn keys_mut(&mut self) -> &mut [K] {
// SAFETY: the caller will not be able to call further methods on self
// until the key slice reference is dropped, as we have unique access
// for the lifetime of the borrow.
unsafe { self.reborrow_mut().into_key_slice_mut() }
}
/// Unsafe because the caller must ensure that the node is not the shared root.
unsafe fn vals_mut(&mut self) -> &mut [V] {
self.reborrow_mut().into_val_slice_mut()
fn vals_mut(&mut self) -> &mut [V] {
// SAFETY: the caller will not be able to call further methods on self
// until the value slice reference is dropped, as we have unique access
// for the lifetime of the borrow.
unsafe { self.reborrow_mut().into_val_slice_mut() }
}
}
impl<'a, K: 'a, V: 'a, Type> NodeRef<marker::Immut<'a>, K, V, Type> {
/// Unsafe because the caller must ensure that the node is not the shared root.
unsafe fn into_key_slice(self) -> &'a [K] {
// We cannot be the shared root, so `as_leaf` is okay.
slice::from_raw_parts(MaybeUninit::first_ptr(&self.as_leaf().keys), self.len())
fn into_key_slice(self) -> &'a [K] {
unsafe { slice::from_raw_parts(MaybeUninit::first_ptr(&self.as_leaf().keys), self.len()) }
}
/// Unsafe because the caller must ensure that the node is not the shared root.
unsafe fn into_val_slice(self) -> &'a [V] {
// We cannot be the shared root, so `as_leaf` is okay.
slice::from_raw_parts(MaybeUninit::first_ptr(&self.as_leaf().vals), self.len())
fn into_val_slice(self) -> &'a [V] {
unsafe { slice::from_raw_parts(MaybeUninit::first_ptr(&self.as_leaf().vals), self.len()) }
}
/// Unsafe because the caller must ensure that the node is not the shared root.
unsafe fn into_slices(self) -> (&'a [K], &'a [V]) {
let k = ptr::read(&self);
fn into_slices(self) -> (&'a [K], &'a [V]) {
// SAFETY: equivalent to reborrow() except not requiring Type: 'a
let k = unsafe { ptr::read(&self) };
(k.into_key_slice(), self.into_val_slice())
}
}
@ -514,25 +509,27 @@ impl<'a, K: 'a, V: 'a, Type> NodeRef<marker::Mut<'a>, K, V, Type> {
unsafe { &mut *(self.root as *mut Root<K, V>) }
}
/// Unsafe because the caller must ensure that the node is not the shared root.
unsafe fn into_key_slice_mut(mut self) -> &'a mut [K] {
// We cannot be the shared root, so `as_leaf_mut` is okay.
slice::from_raw_parts_mut(
MaybeUninit::first_ptr_mut(&mut (*self.as_leaf_mut()).keys),
self.len(),
)
fn into_key_slice_mut(mut self) -> &'a mut [K] {
// SAFETY: The keys of a node must always be initialized up to length.
unsafe {
slice::from_raw_parts_mut(
MaybeUninit::first_ptr_mut(&mut (*self.as_leaf_mut()).keys),
self.len(),
)
}
}
/// Unsafe because the caller must ensure that the node is not the shared root.
unsafe fn into_val_slice_mut(mut self) -> &'a mut [V] {
slice::from_raw_parts_mut(
MaybeUninit::first_ptr_mut(&mut (*self.as_leaf_mut()).vals),
self.len(),
)
fn into_val_slice_mut(mut self) -> &'a mut [V] {
// SAFETY: The values of a node must always be initialized up to length.
unsafe {
slice::from_raw_parts_mut(
MaybeUninit::first_ptr_mut(&mut (*self.as_leaf_mut()).vals),
self.len(),
)
}
}
/// Unsafe because the caller must ensure that the node is not the shared root.
unsafe fn into_slices_mut(mut self) -> (&'a mut [K], &'a mut [V]) {
fn into_slices_mut(mut self) -> (&'a mut [K], &'a mut [V]) {
// We cannot use the getters here, because calling the second one
// invalidates the reference returned by the first.
// More precisely, it is the call to `len` that is the culprit,
@ -540,8 +537,13 @@ impl<'a, K: 'a, V: 'a, Type> NodeRef<marker::Mut<'a>, K, V, Type> {
// overlap with the keys (and even the values, for ZST keys).
let len = self.len();
let leaf = self.as_leaf_mut();
let keys = slice::from_raw_parts_mut(MaybeUninit::first_ptr_mut(&mut (*leaf).keys), len);
let vals = slice::from_raw_parts_mut(MaybeUninit::first_ptr_mut(&mut (*leaf).vals), len);
// SAFETY: The keys and values of a node must always be initialized up to length.
let keys = unsafe {
slice::from_raw_parts_mut(MaybeUninit::first_ptr_mut(&mut (*leaf).keys), len)
};
let vals = unsafe {
slice::from_raw_parts_mut(MaybeUninit::first_ptr_mut(&mut (*leaf).vals), len)
};
(keys, vals)
}
}
@ -698,8 +700,7 @@ impl<'a, K, V> NodeRef<marker::Mut<'a>, K, V, marker::LeafOrInternal> {
}
}
/// Unsafe because the caller must ensure that the node is not the shared root.
unsafe fn into_kv_pointers_mut(mut self) -> (*mut K, *mut V) {
fn into_kv_pointers_mut(mut self) -> (*mut K, *mut V) {
(self.keys_mut().as_mut_ptr(), self.vals_mut().as_mut_ptr())
}
}

5
src/liballoc/collections/btree/search.rs
View File

@ -67,12 +67,11 @@ where
Q: Ord,
K: Borrow<Q>,
{
// This function is defined over all borrow types (immutable, mutable, owned),
// and may be called on the shared root in each case.
// This function is defined over all borrow types (immutable, mutable, owned).
// Using `keys()` is fine here even if BorrowType is mutable, as all we return
// is an index -- not a reference.
let len = node.len();
let keys = unsafe { node.keys() }; // safe because a non-empty node cannot be the shared root
let keys = node.keys();
for (i, k) in keys.iter().enumerate() {
match key.cmp(k.borrow()) {
Ordering::Greater => {}