added pinned_drop

drivers/android/transaction.rs

@@ -7,6 +7,7 @@ use kernel::{
     io_buffer::IoBufferWriter,
     linked_list::List,
     linked_list::{GetLinks, Links},
+    macros::pinned_drop,
     new_spinlock,
     prelude::*,
     sync::{Arc, SpinLock, UniqueArc},
@@ -27,7 +28,7 @@ struct TransactionInner {
     file_list: List<Box<FileInfo>>,
 }
 
-#[pin_project]
+#[pin_project(PinnedDrop)]
 pub(crate) struct Transaction {
     #[pin]
     inner: SpinLock<TransactionInner>,
@@ -276,8 +277,9 @@ impl DeliverToRead for Transaction {
     }
 }
 
-impl Drop for Transaction {
-    fn drop(&mut self) {
+#[pinned_drop]
+impl PinnedDrop for Transaction {
+    fn drop(self: Pin<&mut Self>) {
         if self.free_allocation.load(Ordering::Relaxed) {
             self.to.buffer_get(self.data_address);
         }

rust/kernel/init.rs

@@ -641,6 +641,18 @@ where
     }
 }
 
+/// Trait facilitating pinned destruction.
+///
+/// Use [`pinned_drop`] to implement this trait safely.
+pub unsafe trait PinnedDrop {
+    /// # Safety
+    ///
+    /// Only call this from `<Self as Drop>::drop`.
+    unsafe fn drop(self: Pin<&mut Self>);
+    #[doc(hidden)]
+    fn __ensure_no_unsafe_op_in_drop(self: Pin<&mut Self>);
+}
+
 /// Smart pointer that can initialize memory in-place.
 pub trait InPlaceInit<T>: Sized {
     /// Use the given initializer to in-place initialize a `T`.

rust/macros/lib.rs

@@ -6,6 +6,7 @@ mod concat_idents;
 mod helpers;
 mod module;
 mod pin_project;
+mod pinned_drop;
 mod vtable;
 
 use proc_macro::TokenStream;
@@ -211,3 +212,9 @@ pub fn concat_idents(ts: TokenStream) -> TokenStream {
 pub fn pin_project(inner: TokenStream, item: TokenStream) -> TokenStream {
     pin_project::pin_project(inner, item)
 }
+
+/// TODO
+#[proc_macro_attribute]
+pub fn pinned_drop(args: TokenStream, input: TokenStream) -> TokenStream {
+    pinned_drop::pinned_drop(args, input)
+}

rust/macros/pinned_drop.rs

@@ -0,0 +1,101 @@
+// SPDX-License-Identifier: GPL-2.0
+
+use proc_macro::{Delimiter, Group, Ident, Punct, Spacing, Span, TokenStream, TokenTree};
+
+pub(crate) fn pinned_drop(_args: TokenStream, input: TokenStream) -> TokenStream {
+    let mut toks = input.into_iter().collect::<Vec<_>>();
+    assert!(!toks.is_empty());
+    // ensure that we have an impl item
+    assert!(matches!(&toks[0], TokenTree::Ident(i) if i.to_string() == "impl"));
+    // ensure that we are implementing `PinnedDrop`
+    let mut nesting: usize = 0;
+    let mut pinned_drop_idx = None;
+    for (i, tt) in toks.iter().enumerate() {
+        match tt {
+            TokenTree::Punct(p) if p.as_char() == '<' => {
+                nesting += 1;
+            }
+            TokenTree::Punct(p) if p.as_char() == '>' => {
+                nesting = nesting.checked_sub(1).unwrap();
+            }
+            _ => {}
+        }
+        if i >= 1 && nesting == 0 {
+            assert!(matches!(tt, TokenTree::Ident(i) if i.to_string() == "PinnedDrop"));
+            pinned_drop_idx = Some(i);
+            break;
+        }
+    }
+    let idx = pinned_drop_idx.unwrap();
+    //inserting `::kernel::init::` in reverse order
+    toks.insert(idx, TokenTree::Punct(Punct::new(':', Spacing::Alone)));
+    toks.insert(idx, TokenTree::Punct(Punct::new(':', Spacing::Joint)));
+    toks.insert(idx, TokenTree::Ident(Ident::new("init", Span::call_site())));
+    toks.insert(idx, TokenTree::Punct(Punct::new(':', Spacing::Alone)));
+    toks.insert(idx, TokenTree::Punct(Punct::new(':', Spacing::Joint)));
+    toks.insert(
+        idx,
+        TokenTree::Ident(Ident::new("kernel", Span::call_site())),
+    );
+    toks.insert(idx, TokenTree::Punct(Punct::new(':', Spacing::Alone)));
+    toks.insert(idx, TokenTree::Punct(Punct::new(':', Spacing::Joint)));
+    if let Some(TokenTree::Group(last)) = toks.pop() {
+        let mut inner = last.stream().into_iter().collect::<Vec<_>>();
+        if let Some(TokenTree::Group(inner_last)) = inner.pop() {
+            // make the impl unsafe
+            toks.insert(0, TokenTree::Ident(Ident::new("unsafe", Span::call_site())));
+            // make the first function unsafe
+            inner.insert(0, TokenTree::Ident(Ident::new("unsafe", Span::call_site())));
+            // re-add the body
+            inner.push(TokenTree::Group(inner_last.clone()));
+            add_ensure_no_unsafe_op_in_drop(&mut inner, inner_last);
+            toks.push(TokenTree::Group(Group::new(
+                Delimiter::Brace,
+                TokenStream::from_iter(inner),
+            )));
+            TokenStream::from_iter(toks)
+        } else {
+            toks.push(TokenTree::Group(last));
+            TokenStream::from_iter(toks)
+        }
+    } else {
+        TokenStream::from_iter(toks)
+    }
+}
+
+fn add_ensure_no_unsafe_op_in_drop(v: &mut Vec<TokenTree>, inner_last: Group) {
+    v.push(TokenTree::Ident(Ident::new("fn", Span::call_site())));
+    v.push(TokenTree::Ident(Ident::new(
+        "__ensure_no_unsafe_op_in_drop",
+        Span::call_site(),
+    )));
+    v.push(TokenTree::Group(Group::new(
+        Delimiter::Parenthesis,
+        TokenStream::from_iter(vec![
+            TokenTree::Ident(Ident::new("self", Span::call_site())),
+            TokenTree::Punct(Punct::new(':', Spacing::Alone)),
+            TokenTree::Punct(Punct::new(':', Spacing::Joint)),
+            TokenTree::Punct(Punct::new(':', Spacing::Alone)),
+            TokenTree::Ident(Ident::new("core", Span::call_site())),
+            TokenTree::Punct(Punct::new(':', Spacing::Joint)),
+            TokenTree::Punct(Punct::new(':', Spacing::Alone)),
+            TokenTree::Ident(Ident::new("pin", Span::call_site())),
+            TokenTree::Punct(Punct::new(':', Spacing::Joint)),
+            TokenTree::Punct(Punct::new(':', Spacing::Alone)),
+            TokenTree::Ident(Ident::new("Pin", Span::call_site())),
+            TokenTree::Punct(Punct::new('<', Spacing::Alone)),
+            TokenTree::Punct(Punct::new('&', Spacing::Alone)),
+            TokenTree::Ident(Ident::new("mut", Span::call_site())),
+            TokenTree::Ident(Ident::new("Self", Span::call_site())),
+            TokenTree::Punct(Punct::new('>', Spacing::Alone)),
+        ]),
+    )));
+    v.push(TokenTree::Group(Group::new(
+        Delimiter::Brace,
+        TokenStream::from_iter(vec![
+            TokenTree::Ident(Ident::new("if", Span::call_site())),
+            TokenTree::Ident(Ident::new("false", Span::call_site())),
+            TokenTree::Group(inner_last),
+        ]),
+    )));
+}