From 7498159226772d66f150dd406be462d75964a366 Mon Sep 17 00:00:00 2001 From: Miguel Ojeda Date: Sat, 12 Jul 2025 18:01:03 +0200 Subject: rust: use `#[used(compiler)]` to fix build and `modpost` with Rust >= 1.89.0 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Starting with Rust 1.89.0 (expected 2025-08-07), the Rust compiler fails to build the `rusttest` target due to undefined references such as: kernel...-cgu.0:(.text....+0x116): undefined reference to `rust_helper_kunit_get_current_test' Moreover, tooling like `modpost` gets confused: WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/gpu/drm/nova/nova.o ERROR: modpost: missing MODULE_LICENSE() in drivers/gpu/nova-core/nova_core.o The reason behind both issues is that the Rust compiler will now [1] treat `#[used]` as `#[used(linker)]` instead of `#[used(compiler)]` for our targets. This means that the retain section flag (`R`, `SHF_GNU_RETAIN`) will be used and that they will be marked as `unique` too, with different IDs. In turn, that means we end up with undefined references that did not get discarded in `rusttest` and that multiple `.modinfo` sections are generated, which confuse tooling like `modpost` because they only expect one. Thus start using `#[used(compiler)]` to keep the previous behavior and to be explicit about what we want. Sadly, it is an unstable feature (`used_with_arg`) [2] -- we will talk to upstream Rust about it. The good news is that it has been available for a long time (Rust >= 1.60) [3]. The changes should also be fine for previous Rust versions, since they behave the same way as before [4]. Alternatively, we could use `#[no_mangle]` or `#[export_name = ...]` since those still behave like `#[used(compiler)]`, but of course it is not really what we want to express, and it requires other changes to avoid symbol conflicts. Cc: David Wood Cc: Wesley Wiser Cc: stable@vger.kernel.org # Needed in 6.12.y and later (Rust is pinned in older LTSs). Link: https://github.com/rust-lang/rust/pull/140872 [1] Link: https://github.com/rust-lang/rust/issues/93798 [2] Link: https://github.com/rust-lang/rust/pull/91504 [3] Link: https://godbolt.org/z/sxzWTMfzW [4] Reviewed-by: Alice Ryhl Acked-by: Björn Roy Baron Link: https://lore.kernel.org/r/20250712160103.1244945-3-ojeda@kernel.org Signed-off-by: Miguel Ojeda --- scripts/Makefile.build | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'scripts/Makefile.build') diff --git a/scripts/Makefile.build b/scripts/Makefile.build index a6461ea411f7..ba71b27aa363 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -312,10 +312,11 @@ $(obj)/%.lst: $(obj)/%.c FORCE # - Stable since Rust 1.82.0: `feature(asm_const)`, `feature(raw_ref_op)`. # - Stable since Rust 1.87.0: `feature(asm_goto)`. # - Expected to become stable: `feature(arbitrary_self_types)`. +# - To be determined: `feature(used_with_arg)`. # # Please see https://github.com/Rust-for-Linux/linux/issues/2 for details on # the unstable features in use. -rust_allowed_features := asm_const,asm_goto,arbitrary_self_types,lint_reasons,raw_ref_op +rust_allowed_features := asm_const,asm_goto,arbitrary_self_types,lint_reasons,raw_ref_op,used_with_arg # `--out-dir` is required to avoid temporaries being created by `rustc` in the # current working directory, which may be not accessible in the out-of-tree -- cgit v1.2.3 From 5d840b4c4935cd5100be97b6df565b4b159970a5 Mon Sep 17 00:00:00 2001 From: Tamir Duberstein Date: Wed, 9 Jul 2025 15:31:15 -0400 Subject: rust: list: add `impl_list_item!` examples There's a comprehensive example in `rust/kernel/list.rs` but it doesn't exercise the `using ListLinksSelfPtr` variant nor the generic cases. Add that here. Generalize `impl_has_list_links_self_ptr` to handle nested fields in the same manner as `impl_has_list_links`. Tested-by: Alice Ryhl Reviewed-by: Alice Ryhl Signed-off-by: Tamir Duberstein Link: https://lore.kernel.org/r/20250709-list-no-offset-v4-5-a429e75840a9@gmail.com [ Fixed Rust < 1.82 build by enabling the `offset_of_nested` feature. - Miguel ] Signed-off-by: Miguel Ojeda --- rust/kernel/list/impl_list_item_mod.rs | 96 ++++++++++++++++++++++++++++++++-- scripts/Makefile.build | 5 +- 2 files changed, 96 insertions(+), 5 deletions(-) (limited to 'scripts/Makefile.build') diff --git a/rust/kernel/list/impl_list_item_mod.rs b/rust/kernel/list/impl_list_item_mod.rs index 6717b614e896..374b3dd812d0 100644 --- a/rust/kernel/list/impl_list_item_mod.rs +++ b/rust/kernel/list/impl_list_item_mod.rs @@ -82,20 +82,20 @@ macro_rules! impl_has_list_links_self_ptr { ($(impl$({$($generics:tt)*})? HasSelfPtr<$item_type:ty $(, $id:tt)?> for $self:ty - { self.$field:ident } + { self$(.$field:ident)* } )*) => {$( // SAFETY: The implementation of `raw_get_list_links` only compiles if the field has the // right type. unsafe impl$(<$($generics)*>)? $crate::list::HasSelfPtr<$item_type $(, $id)?> for $self {} unsafe impl$(<$($generics)*>)? $crate::list::HasListLinks$(<$id>)? for $self { - const OFFSET: usize = ::core::mem::offset_of!(Self, $field) as usize; + const OFFSET: usize = ::core::mem::offset_of!(Self, $($field).*) as usize; #[inline] unsafe fn raw_get_list_links(ptr: *mut Self) -> *mut $crate::list::ListLinks$(<$id>)? { // SAFETY: The caller promises that the pointer is not dangling. let ptr: *mut $crate::list::ListLinksSelfPtr<$item_type $(, $id)?> = - unsafe { ::core::ptr::addr_of_mut!((*ptr).$field) }; + unsafe { ::core::ptr::addr_of_mut!((*ptr)$(.$field)*) }; ptr.cast() } } @@ -109,6 +109,96 @@ pub use impl_has_list_links_self_ptr; /// implement that trait. /// /// [`ListItem`]: crate::list::ListItem +/// +/// # Examples +/// +/// ``` +/// #[pin_data] +/// struct SimpleListItem { +/// value: u32, +/// #[pin] +/// links: kernel::list::ListLinks, +/// } +/// +/// kernel::list::impl_has_list_links! { +/// impl HasListLinks<0> for SimpleListItem { self.links } +/// } +/// +/// kernel::list::impl_list_arc_safe! { +/// impl ListArcSafe<0> for SimpleListItem { untracked; } +/// } +/// +/// kernel::list::impl_list_item! { +/// impl ListItem<0> for SimpleListItem { using ListLinks; } +/// } +/// +/// struct ListLinksHolder { +/// inner: kernel::list::ListLinks, +/// } +/// +/// #[pin_data] +/// struct ComplexListItem { +/// value: Result, +/// #[pin] +/// links: ListLinksHolder, +/// } +/// +/// kernel::list::impl_has_list_links! { +/// impl{T, U} HasListLinks<0> for ComplexListItem { self.links.inner } +/// } +/// +/// kernel::list::impl_list_arc_safe! { +/// impl{T, U} ListArcSafe<0> for ComplexListItem { untracked; } +/// } +/// +/// kernel::list::impl_list_item! { +/// impl{T, U} ListItem<0> for ComplexListItem { using ListLinks; } +/// } +/// ``` +/// +/// ``` +/// #[pin_data] +/// struct SimpleListItem { +/// value: u32, +/// #[pin] +/// links: kernel::list::ListLinksSelfPtr, +/// } +/// +/// kernel::list::impl_list_arc_safe! { +/// impl ListArcSafe<0> for SimpleListItem { untracked; } +/// } +/// +/// kernel::list::impl_has_list_links_self_ptr! { +/// impl HasSelfPtr for SimpleListItem { self.links } +/// } +/// +/// kernel::list::impl_list_item! { +/// impl ListItem<0> for SimpleListItem { using ListLinksSelfPtr; } +/// } +/// +/// struct ListLinksSelfPtrHolder { +/// inner: kernel::list::ListLinksSelfPtr>, +/// } +/// +/// #[pin_data] +/// struct ComplexListItem { +/// value: Result, +/// #[pin] +/// links: ListLinksSelfPtrHolder, +/// } +/// +/// kernel::list::impl_list_arc_safe! { +/// impl{T, U} ListArcSafe<0> for ComplexListItem { untracked; } +/// } +/// +/// kernel::list::impl_has_list_links_self_ptr! { +/// impl{T, U} HasSelfPtr> for ComplexListItem { self.links.inner } +/// } +/// +/// kernel::list::impl_list_item! { +/// impl{T, U} ListItem<0> for ComplexListItem { using ListLinksSelfPtr; } +/// } +/// ``` #[macro_export] macro_rules! impl_list_item { ( diff --git a/scripts/Makefile.build b/scripts/Makefile.build index a6461ea411f7..79c40af6f399 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -309,13 +309,14 @@ $(obj)/%.lst: $(obj)/%.c FORCE # The features in this list are the ones allowed for non-`rust/` code. # # - Stable since Rust 1.81.0: `feature(lint_reasons)`. -# - Stable since Rust 1.82.0: `feature(asm_const)`, `feature(raw_ref_op)`. +# - Stable since Rust 1.82.0: `feature(asm_const)`, +# `feature(offset_of_nested)`, `feature(raw_ref_op)`. # - Stable since Rust 1.87.0: `feature(asm_goto)`. # - Expected to become stable: `feature(arbitrary_self_types)`. # # Please see https://github.com/Rust-for-Linux/linux/issues/2 for details on # the unstable features in use. -rust_allowed_features := asm_const,asm_goto,arbitrary_self_types,lint_reasons,raw_ref_op +rust_allowed_features := asm_const,asm_goto,arbitrary_self_types,lint_reasons,offset_of_nested,raw_ref_op # `--out-dir` is required to avoid temporaries being created by `rustc` in the # current working directory, which may be not accessible in the out-of-tree -- cgit v1.2.3