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Miguel Ojeda
993f235c4a
When the pointer formatting series [1] is applied and KUnit tests
are enabled, `objtool` would report an error with any of our
supported Rust versions. For instance, with Rust 1.97.1:
rust/kernel.o: error: objtool: _R..._4core3fmt7Pointer3fmtB7_()
falls through to next function _R..._4core7convert5AsRefNtB5_4BStrE6as_ref()
Or, with Rust 1.85.0:
rust/kernel.o: error: objtool: _R..._4core3fmt7Pointer3fmtB7_()
falls through to next function _R..._4core3ffi5c_str4CStrENtNtBS_3fmt7Display3fmtB7_()
This happens due to calls to the `noreturn` symbol:
core::str::slice_error_fail
Thus add the mangled one to the list so that `objtool` knows it is
actually `noreturn`.
See commit 56d680dd23 ("objtool/rust: list `noreturn` Rust functions")
for more details.
[ While the series [1] mentioned above was not applied in a way
that triggered this, Gary found another case [2]:
I am seeing this function causing issue on my 1.85.1 -Os build, although the
error message is different this time:
rust/kernel.o: warning: objtool: _R..._5range9RangeFromjEE5indexCsldbe0TGTmNx_6kernel+0x1d:
stack state mismatch: cfa1=4+8 cfa2=4+16
Disassembly shows that the function call before the warning location
is a call to _4core3str16slice_error_fail, and objtool thought it can
return (which will end up with a unbalanced stack if it does return).
Thus apply it. - Miguel ]
Cc: stable@vger.kernel.org # Needed in 6.12.y and later (Rust is pinned in older LTSs).
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Reported-by: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/rust-for-linux/anLxXvCKBcAVf91_@google.com/
Link: https://lore.kernel.org/rust-for-linux/20260706-hashedptr-v13-0-377a07f2f78d@kylinos.cn/ [1]
Link: https://lore.kernel.org/rust-for-linux/DKS7U9UHY6XR.2JC0EBIPCI06Z@garyguo.net/ [2]
Link: https://patch.msgid.link/20260805144524.233362-1-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>