kbuild: rust: keep Rust objects out of Clang LTO with inline helpersgrafted

Under `CONFIG_LTO_CLANG` + `CONFIG_RUST_INLINE_HELPERS`, one may hit
`objtool` errors such as:

    vmlinux.o: error: objtool: _R..._3Gsp4boot+0xd6a:
    can't find jump dest instruction at .text._R..._3Gsp4boot+0x1dfd

The reason is that in such builds, the Clang invocation that compiles
the combined Rust plus helpers bitcode emits LLVM bitcode (again) --
the final code generation happens in the linker's LTO step, which the
`-mllvm` trap options passed to Clang do not reach.

This, in turn, means that unreachable traps are missing, and the
impossible paths do not merely fallthrough to the next symbol, but past
the end of their own section, since LTO builds place each function in
its own section.

Thus filter `CC_FLAGS_LTO` out of the Clang invocation, so that it always
emits machine code directly, with the traps in place.

Assisted-by: LLM
Cc: Gary Guo <gary@garyguo.net>
Cc: Boqun Feng <boqun@kernel.org>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Matthew Maurer <mmaurer@google.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers into Rust")
Acked-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260816133233.197500-2-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

1 files changed, 31 insertions, 0 deletions

diff --git a/fs/hfsplus/Kconfig b/fs/hfsplus/Kconfig
new file mode 100644
index 000000000..ca8401cb6
--- /dev/null
+++ b/fs/hfsplus/Kconfig
@@ -0,0 +1,31 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config HFSPLUS_FS
+	tristate "Apple Extended HFS file system support"
+	depends on BLOCK
+	select BUFFER_HEAD
+	select NLS
+	select NLS_UTF8
+	select LEGACY_DIRECT_IO
+	help
+	  If you say Y here, you will be able to mount extended format
+	  Macintosh-formatted hard drive partitions with full read-write access.
+
+	  This file system is often called HFS+ and was introduced with
+	  MacOS 8. It includes all Mac specific filesystem data such as
+	  data forks and creator codes, but it also has several UNIX
+	  style features such as file ownership and permissions.
+
+config HFSPLUS_KUNIT_TEST
+	tristate "KUnit tests for HFS+ filesystem" if !KUNIT_ALL_TESTS
+	depends on HFSPLUS_FS && KUNIT
+	default KUNIT_ALL_TESTS
+	help
+	  This builds KUnit tests for the HFS+ filesystem.
+
+	  KUnit tests run during boot and output the results to the debug
+	  log in TAP format (https://testanything.org/). Only useful for
+	  kernel devs running KUnit test harness and are not for inclusion
+	  into a production build.
+
+	  For more information on KUnit and unit tests in general please
+	  refer to the KUnit documentation in Documentation/dev-tools/kunit/.