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, 24 insertions, 0 deletions

diff --git a/fs/affs/Kconfig b/fs/affs/Kconfig
new file mode 100644
index 000000000..1ae432d26
--- /dev/null
+++ b/fs/affs/Kconfig
@@ -0,0 +1,24 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config AFFS_FS
+	tristate "Amiga FFS file system support"
+	depends on BLOCK
+	select BUFFER_HEAD
+	select LEGACY_DIRECT_IO
+	help
+	  The Fast File System (FFS) is the common file system used on hard
+	  disks by Amiga(tm) systems since AmigaOS Version 1.3 (34.20).  Say Y
+	  if you want to be able to read and write files from and to an Amiga
+	  FFS partition on your hard drive.  Amiga floppies however cannot be
+	  read with this driver due to an incompatibility of the floppy
+	  controller used in an Amiga and the standard floppy controller in
+	  PCs and workstations. Read <file:Documentation/filesystems/affs.rst>
+	  and <file:fs/affs/Changes>.
+
+	  With this driver you can also mount disk files used by Bernd
+	  Schmidt's Un*X Amiga Emulator
+	  (<http://www.freiburg.linux.de/~uae/>).
+	  If you want to do this, you will also need to say Y or M to "Loop
+	  device support", above.
+
+	  To compile this file system support as a module, choose M here: the
+	  module will be called affs.  If unsure, say N.