linux.git/rust/kernel/list, branch v6.18.21

rust: list: Add unsafe blocks for container_of and safety comments

2026-03-04T12:21:35+00:00

[ Upstream commit 97b281d7edb2ae662365be2809cd728470119720 ]

impl_list_item_mod.rs calls container_of! without unsafe blocks at a
couple of places. Since container_of! is unsafe, the blocks are strictly
necessary.

The problem was so far not visible because the "unsafe-op-in-unsafe-fn"
check is a lint rather than a hard compiler error, and Rust suppresses
lints triggered inside of a macro from another crate.

Thus, the error becomes only visible once someone from within the kernel
crate tries to use linked lists:

    error[E0133]: call to unsafe function `core::ptr::mut_ptr::::byte_sub`
    is unsafe and requires unsafe block
       --> rust/kernel/lib.rs:252:29
        |
    252 |           let container_ptr = field_ptr.byte_sub(offset).cast::<$Container>();
        |                               ^^^^^^^^^^^^^^^^^^^^^^^^^^ call to unsafe function
        |
       ::: rust/kernel/drm/jq.rs:98:1
        |
    98  | / impl_list_item! {
    99  | |     impl ListItem<0> for BasicItem { using ListLinks { self.links }; }
    100 | | }
        | |_- in this macro invocation
        |
    note: an unsafe function restricts its caller, but its body is safe by default
       --> rust/kernel/list/impl_list_item_mod.rs:216:13
        |
    216 |               unsafe fn view_value(me: *mut $crate::list::ListLinks<$num>) -> *const Self {
        |               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        |
       ::: rust/kernel/drm/jq.rs:98:1
        |
    98  | / impl_list_item! {
    99  | |     impl ListItem<0> for BasicItem { using ListLinks { self.links }; }
    100 | | }
        | |_- in this macro invocation
        = note: requested on the command line with `-D unsafe-op-in-unsafe-fn`
        = note: this error originates in the macro `$crate::container_of` which comes
        from the expansion of the macro `impl_list_item`

Therefore, add unsafe blocks to container_of! calls to fix the issue.

[ As discussed, let's fix the build for those that want to use the
  macro within the `kernel` crate now and we can discuss the proper
  safety comments afterwards. Thus I removed the ones from the patch.

  However, we cannot just avoid the comments with `CLIPPY=1`, so I
  provided placeholders for now, like we did in the past. They were
  also needed for an `unsafe impl`.

  While I am not happy about it, it isn't worse than the current
  status (the comments were meant to be there), and at least this
  shows what is missing -- our pre-existing "good first issue" [1]
  may motivate new contributors to complete them properly.

  Finally, I moved one of the existing safety comments one line down
  so that Clippy could locate it.

  Link: https://github.com/Rust-for-Linux/linux/issues/351 [1]

    - Miguel ]

Cc: stable@vger.kernel.org
Fixes: c77f85b347dd ("rust: list: remove OFFSET constants")
Suggested-by: Alice Ryhl 
Signed-off-by: Philipp Stanner 
Reviewed-by: Gary Guo 
Reviewed-by: Alice Ryhl 
Link: https://patch.msgid.link/20260216131613.45344-3-phasta@kernel.org
[ Fixed formatting. Reworded to fix the lint suppression
  explanation. Indent build error. - Miguel ]
Signed-off-by: Miguel Ojeda 
Signed-off-by: Sasha Levin

rust: list: remove nonexistent generic parameter in link

2025-07-20T17:29:19+00:00

`ListLinks` does not take a `T` generic parameter, unlike
`ListLinksSelfPtr`.

Thus fix it, which makes it also consistent with the rest of the links
in the file.

Fixes: 40c53294596b ("rust: list: add macro for implementing ListItem")
Reviewed-by: Tamir Duberstein 
Link: https://lore.kernel.org/r/20250719232500.822313-1-ojeda@kernel.org
Signed-off-by: Miguel Ojeda

rust: list: remove OFFSET constants

2025-07-19T21:18:18+00:00

Replace `ListLinksSelfPtr::LIST_LINKS_SELF_PTR_OFFSET` with `unsafe fn
raw_get_self_ptr` which returns a pointer to the field rather than
requiring the caller to do pointer arithmetic.

Implement `HasListLinks::raw_get_list_links` in `impl_has_list_links!`,
narrowing the interface of `HasListLinks` and replacing pointer
arithmetic with `container_of!`.

Modify `impl_list_item` to also invoke `impl_has_list_links!` or
`impl_has_list_links_self_ptr!`. This is necessary to allow
`impl_list_item` to see more of the tokens used by
`impl_has_list_links{,_self_ptr}!`.

A similar API change was discussed on the hrtimer series[1].

Link: https://lore.kernel.org/all/20250224-hrtimer-v3-v6-12-rc2-v9-1-5bd3bf0ce6cc@kernel.org/ [1]
Tested-by: Alice Ryhl 
Reviewed-by: Alice Ryhl 
Signed-off-by: Tamir Duberstein 
Link: https://lore.kernel.org/r/20250709-list-no-offset-v4-6-a429e75840a9@gmail.com
[ Fixed broken intra-doc links. Used the renamed
  `Opaque::cast_into`. - Miguel ]
Signed-off-by: Miguel Ojeda

rust: list: add `impl_list_item!` examples

2025-07-19T21:18:18+00:00

There's a comprehensive example in `rust/kernel/list.rs` but it doesn't
exercise the `using ListLinksSelfPtr` variant nor the generic cases. Add
that here. Generalize `impl_has_list_links_self_ptr` to handle nested
fields in the same manner as `impl_has_list_links`.

Tested-by: Alice Ryhl 
Reviewed-by: Alice Ryhl 
Signed-off-by: Tamir Duberstein 
Link: https://lore.kernel.org/r/20250709-list-no-offset-v4-5-a429e75840a9@gmail.com
[ Fixed Rust < 1.82 build by enabling the `offset_of_nested`
  feature. - Miguel ]
Signed-off-by: Miguel Ojeda

rust: list: use fully qualified path

2025-07-19T21:18:18+00:00

Use a fully qualified path rooted at `$crate` rather than relying on
imports in the invoking scope.

Tested-by: Alice Ryhl 
Reviewed-by: Alice Ryhl 
Signed-off-by: Tamir Duberstein 
Link: https://lore.kernel.org/r/20250709-list-no-offset-v4-4-a429e75840a9@gmail.com
Signed-off-by: Miguel Ojeda

rust: list: use consistent self parameter name

2025-07-19T21:18:18+00:00

Refer to the self parameter of `impl_list_item!` by the same name used
in `impl_has_list_links{,_self_ptr}!`.

Reviewed-by: Christian Schrefl 
Tested-by: Alice Ryhl 
Reviewed-by: Alice Ryhl 
Signed-off-by: Tamir Duberstein 
Link: https://lore.kernel.org/r/20250709-list-no-offset-v4-3-a429e75840a9@gmail.com
Signed-off-by: Miguel Ojeda

rust: list: use consistent type parameter style

2025-07-19T21:18:18+00:00

Refer to the type parameters of `impl_has_list_links{,_self_ptr}!` by
the same name used in `impl_list_item!`. Capture type parameters of
`impl_list_item!` as `tt` using `{}` to match the style of all other
macros that work with generics.

Reviewed-by: Christian Schrefl 
Tested-by: Alice Ryhl 
Reviewed-by: Alice Ryhl 
Signed-off-by: Tamir Duberstein 
Link: https://lore.kernel.org/r/20250709-list-no-offset-v4-2-a429e75840a9@gmail.com
Signed-off-by: Miguel Ojeda

rust: list: simplify macro capture

2025-07-19T21:18:18+00:00

Avoid manually capturing generics; use `ty` to capture the whole type
instead.

Reviewed-by: Christian Schrefl 
Tested-by: Alice Ryhl 
Reviewed-by: Alice Ryhl 
Signed-off-by: Tamir Duberstein 
Link: https://lore.kernel.org/r/20250709-list-no-offset-v4-1-a429e75840a9@gmail.com
Signed-off-by: Miguel Ojeda

rust: list: undo unintended replacement of method name

2025-07-19T21:18:16+00:00

When we renamed `Opaque::raw_get` to `cast_into`, there was one
replacement that was not supposed to be there.

It does not cause an issue so far because it is inside a macro rule (the
`ListLinksSelfPtr` one) that is unused so far. However, it will start
to be used soon.

Thus fix it now.

Fixes: 64fb810bce03 ("rust: types: rename Opaque::raw_get to cast_into")
Reviewed-by: Tamir Duberstein 
Link: https://lore.kernel.org/r/20250719183649.596051-1-ojeda@kernel.org
Signed-off-by: Miguel Ojeda

rust: types: rename Opaque::raw_get to cast_into

2025-07-15T20:26:11+00:00

In the previous patch we added Opaque::cast_from() that performs the
opposite operation to Opaque::raw_get(). For consistency with this
naming, rename raw_get() to cast_from().

There are a few other options such as calling cast_from() something
closer to raw_get() rather than renaming this method. However, I could
not find a great naming scheme that works with raw_get(). The previous
version of this patch used from_raw(), but functions of that name
typically have a different signature, so that's not a great option.

Suggested-by: Danilo Krummrich 
Signed-off-by: Alice Ryhl 
Acked-by: Benno Lossin 
Acked-by: Andreas Hindborg 
Acked-by: Boqun Feng 
Reviewed-by: Danilo Krummrich 
Acked-by: Danilo Krummrich 
Link: https://lore.kernel.org/r/20250624-opaque-from-raw-v2-2-e4da40bdc59c@google.com
[ Removed `HrTimer::raw_get` change. - Miguel ]
Signed-off-by: Miguel Ojeda