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, 27 insertions, 0 deletions

diff --git a/fs/minix/Kconfig b/fs/minix/Kconfig
new file mode 100644
index 000000000..90ddfad2a
--- /dev/null
+++ b/fs/minix/Kconfig
@@ -0,0 +1,27 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config MINIX_FS
+	tristate "Minix file system support"
+	depends on BLOCK
+	select BUFFER_HEAD
+	help
+	  Minix is a simple operating system used in many classes about OS's.
+	  The minix file system (method to organize files on a hard disk
+	  partition or a floppy disk) was the original file system for Linux,
+	  but has been superseded by the second extended file system ext2fs.
+	  You don't want to use the minix file system on your hard disk
+	  because of certain built-in restrictions, but it is sometimes found
+	  on older Linux floppy disks.  This option will enlarge your kernel
+	  by about 28 KB. If unsure, say N.
+
+	  To compile this file system support as a module, choose M here: the
+	  module will be called minix.  Note that the file system of your root
+	  partition (the one containing the directory /) cannot be compiled as
+	  a module.
+
+config MINIX_FS_NATIVE_ENDIAN
+	def_bool MINIX_FS
+	depends on MICROBLAZE || MIPS || S390 || SUPERH || SPARC || XTENSA || (M68K && !MMU)
+
+config MINIX_FS_BIG_ENDIAN_16BIT_INDEXED
+	def_bool MINIX_FS
+	depends on M68K && MMU