On Mon, 18 Nov 2024 20:27:26 +0000
Alice Ryhl <[email protected]> wrote:
> When building the rust_print sample with CONFIG_JUMP_LABEL=n, the Rust
> static key support falls back to using static_key_count. This function
> accepts a mutable pointer to the `struct static_key`, but the Rust
> abstractions are incorrectly passing a const pointer.
>
> This means that builds using CONFIG_JUMP_LABEL=n and SAMPLE_RUST_PRINT=y
> fail with the following error message:
>
> error[E0308]: mismatched types
> --> <root>/samples/rust/rust_print_main.rs:87:5
> |
> 87 | / kernel::declare_trace! {
> 88 | | /// # Safety
> 89 | | ///
> 90 | | /// Always safe to call.
> 91 | | unsafe fn rust_sample_loaded(magic: c_int);
> 92 | | }
> | | ^
> | | |
> | |_____types differ in mutability
> | arguments to this function are incorrect
> |
> = note: expected raw pointer `*mut kernel::bindings::static_key`
> found raw pointer `*const kernel::bindings::static_key`
> note: function defined here
> --> <root>/rust/bindings/bindings_helpers_generated.rs:33:12
> |
> 33 | pub fn static_key_count(key: *mut static_key) -> c_int;
> | ^^^^^^^^^^^^^^^^
>
> To fix this, insert a pointer cast so that the pointer is mutable.
Hi Alice,
BTW, how do you test the sample tracepoint? I see you add a tracepoint in
the module load call, but currently we can enable module tracepoints on
module load. How do you enable it when the rust_print module gets loaded?
-- Steve
>
> Reported-by: kernel test robot <[email protected]>
> Closes:
> https://lore.kernel.org/oe-kbuild-all/[email protected]/
> Fixes: 169484ab6677 ("rust: add arch_static_branch")
> Signed-off-by: Alice Ryhl <[email protected]>
> ---
> rust/kernel/jump_label.rs | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/rust/kernel/jump_label.rs b/rust/kernel/jump_label.rs
> index 2f2df03a3275..b5aff632ecc7 100644
> --- a/rust/kernel/jump_label.rs
> +++ b/rust/kernel/jump_label.rs
> @@ -26,7 +26,7 @@ macro_rules! static_branch_unlikely {
>
> #[cfg(not(CONFIG_JUMP_LABEL))]
> {
> - $crate::bindings::static_key_count(_key) > 0
> + $crate::bindings::static_key_count(_key.cast_mut()) > 0
> }
>
> #[cfg(CONFIG_JUMP_LABEL)]
>
> base-commit: 22193c586b43ee88d66954395885742a6e4a49a9
