Starting with Rust 1.86.0 (see upstream commit b151b513ba2b ("Insert null
checks for pointer dereferences when debug assertions are enabled") [1]),
under some kernel configurations with `CONFIG_RUST_DEBUG_ASSERTIONS=y`,
one may trigger a new `objtool` warning:

    rust/kernel.o: warning: objtool: _R..._6kernel9workqueue6system()
    falls through to next function _R...9workqueue14system_highpri()

due to a call to the `noreturn` symbol:

    core::panicking::panic_null_pointer_dereference

Thus add it to the list so that `objtool` knows it is actually `noreturn`.

See commit 56d680dd23c3 ("objtool/rust: list `noreturn` Rust functions")
for more details.

Cc: stable@vger.kernel.org # Needed in 6.12.y and later (Rust is pinned in older LTSs).
Fixes: 56d680dd23c3 ("objtool/rust: list `noreturn` Rust functions")
Link: https://github.com/rust-lang/rust/commit/b151b513ba2b65c7506ec1a80f2712bbd09154d1 [1]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
---
 tools/objtool/check.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 4a1f6c3169b3..67006eeb30c8 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -225,6 +225,7 @@ static bool is_rust_noreturn(const struct symbol *func)
 	       str_ends_with(func->name, "_4core9panicking14panic_nounwind")				||
 	       str_ends_with(func->name, "_4core9panicking18panic_bounds_check")			||
 	       str_ends_with(func->name, "_4core9panicking19assert_failed_inner")			||
+	       str_ends_with(func->name, "_4core9panicking30panic_null_pointer_dereference")		||
 	       str_ends_with(func->name, "_4core9panicking36panic_misaligned_pointer_dereference")	||
 	       strstr(func->name, "_4core9panicking13assert_failed")					||
 	       strstr(func->name, "_4core9panicking11panic_const24panic_const_")			||

base-commit: 0af2f6be1b4281385b618cb86ad946eded089ac8
-- 
2.49.0

On Sun, Apr 13, 2025 at 2:26 AM Miguel Ojeda <ojeda@kernel.org> wrote:
>
> Thus add it to the list so that `objtool` knows it is actually `noreturn`.

Applied to `rust-fixes` -- thanks everyone! I applied it early to
start to get testing -- tags still welcomed for a day or so.

I changed the title a bit (adding "for Rust 1.86.0") to avoid
confusion with a previous patch (and future ones), since a bot already
got confused.

If `objtool` prefers to apply this instead, please let me know and I
will drop it!

Cheers,
Miguel

On Sun, Apr 13, 2025 at 02:23:38AM +0200, Miguel Ojeda wrote:
> Starting with Rust 1.86.0 (see upstream commit b151b513ba2b ("Insert null
> checks for pointer dereferences when debug assertions are enabled") [1]),
> under some kernel configurations with `CONFIG_RUST_DEBUG_ASSERTIONS=y`,
> one may trigger a new `objtool` warning:
> 
>     rust/kernel.o: warning: objtool: _R..._6kernel9workqueue6system()
>     falls through to next function _R...9workqueue14system_highpri()
> 
> due to a call to the `noreturn` symbol:
> 
>     core::panicking::panic_null_pointer_dereference
> 
> Thus add it to the list so that `objtool` knows it is actually `noreturn`.
> 
> See commit 56d680dd23c3 ("objtool/rust: list `noreturn` Rust functions")
> for more details.
> 
> Cc: stable@vger.kernel.org # Needed in 6.12.y and later (Rust is pinned in older LTSs).
> Fixes: 56d680dd23c3 ("objtool/rust: list `noreturn` Rust functions")
> Link: https://github.com/rust-lang/rust/commit/b151b513ba2b65c7506ec1a80f2712bbd09154d1 [1]
> Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

Reviewed-by: Alice Ryhl <aliceryhl@google.com>