Hello Miguel,
On Fri, May 02, 2025 at 04:02:33PM +0200, Miguel Ojeda wrote:
Starting with Rust 1.87.0 (expected 2025-05-15), `objtool` may report:
rust/core.o: warning: objtool: _R..._4core9panicking9panic_fmt() falls through to next function _R..._4core9panicking18panic_nounwind_fmt() rust/core.o: warning: objtool: _R..._4core9panicking18panic_nounwind_fmt() falls through to next function _R..._4core9panicking5panic()
We are seeing a similar issue with the patch [1]:
RUSTC [M] drivers/gpu/nova-core/nova_core.o drivers/gpu/nova-core/nova_core.o: warning: objtool: <nova_core::vbios::PciAtBiosImage as core::convert::TryFrom<nova_core::vbios::BiosImageBase>>::try_from() falls through to next function <nova_core::vbios::FwSecBiosImage>::fwsec_header()
The code in concern is implementing try_from(): + +impl TryFrom<BiosImageBase> for PciAtBiosImage { + type Error = Error; + + fn try_from(base: BiosImageBase) -> Result<Self> {
I dumped the codegen [2] for this function and at the end of the codegen, there is a call instruction to to the fwsec_header() function.
Any thoughts on how to fix the warning?
thanks,
- Joel
[1] https://lore.kernel.org/all/20250420-nova-frts-v1-13-ecd1cca23963@nvidia.com... [2] https://paste.debian.net/1374516/
The reason is that `rust_begin_unwind` is now mangled:
_R..._7___rustc17rust_begin_unwindThus add the mangled one to the list so that `objtool` knows it is actually `noreturn`.
See commit 56d680dd23c3 ("objtool/rust: list `noreturn` Rust functions") for more details.
Alternatively, we could remove the fixed one in `noreturn.h` and relax this test to cover both, but it seems best to be strict as long as we can.
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 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 3a411064fa34..b21b12ec88d9 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -227,6 +227,7 @@ static bool is_rust_noreturn(const struct symbol *func) 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") ||
str_ends_with(func->name, "_7___rustc17rust_begin_unwind") || strstr(func->name, "_4core9panicking13assert_failed") || strstr(func->name, "_4core9panicking11panic_const24panic_const_") || (strstr(func->name, "_4core5slice5index24slice_") &&-- 2.49.0