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, 152 insertions, 0 deletions

diff --git a/fs/f2fs/Kconfig b/fs/f2fs/Kconfig
new file mode 100644
index 000000000..5916a02fb
--- /dev/null
+++ b/fs/f2fs/Kconfig
@@ -0,0 +1,152 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config F2FS_FS
+	tristate "F2FS filesystem support"
+	depends on BLOCK
+	select BUFFER_HEAD
+	select NLS
+	select CRC32
+	select F2FS_FS_XATTR if FS_ENCRYPTION
+	select FS_ENCRYPTION_ALGS if FS_ENCRYPTION
+	select FS_IOMAP
+	select LZ4_COMPRESS if F2FS_FS_LZ4
+	select LZ4_DECOMPRESS if F2FS_FS_LZ4
+	select LZ4HC_COMPRESS if F2FS_FS_LZ4HC
+	select LZO_COMPRESS if F2FS_FS_LZO
+	select LZO_DECOMPRESS if F2FS_FS_LZO
+	select ZSTD_COMPRESS if F2FS_FS_ZSTD
+	select ZSTD_DECOMPRESS if F2FS_FS_ZSTD
+	help
+	  F2FS is based on Log-structured File System (LFS), which supports
+	  versatile "flash-friendly" features. The design has been focused on
+	  addressing the fundamental issues in LFS, which are snowball effect
+	  of wandering tree and high cleaning overhead.
+
+	  Since flash-based storages show different characteristics according to
+	  the internal geometry or flash memory management schemes aka FTL, F2FS
+	  and tools support various parameters not only for configuring on-disk
+	  layout, but also for selecting allocation and cleaning algorithms.
+
+	  If unsure, say N.
+
+config F2FS_STAT_FS
+	bool "F2FS Status Information"
+	depends on F2FS_FS
+	default y
+	help
+	  /sys/kernel/debug/f2fs/ contains information about all the partitions
+	  mounted as f2fs. Each file shows the whole f2fs information.
+
+	  /sys/kernel/debug/f2fs/status includes:
+	    - major filesystem information managed by f2fs currently
+	    - average SIT information about whole segments
+	    - current memory footprint consumed by f2fs.
+
+config F2FS_FS_XATTR
+	bool "F2FS extended attributes"
+	depends on F2FS_FS
+	default y
+	help
+	  Extended attributes are name:value pairs associated with inodes by
+	  the kernel or by users (see the attr(5) manual page for details).
+
+	  If unsure, say N.
+
+config F2FS_FS_POSIX_ACL
+	bool "F2FS Access Control Lists"
+	depends on F2FS_FS_XATTR
+	select FS_POSIX_ACL
+	default y
+	help
+	  Posix Access Control Lists (ACLs) support permissions for users and
+	  groups beyond the owner/group/world scheme.
+
+	  If you don't know what Access Control Lists are, say N
+
+config F2FS_FS_SECURITY
+	bool "F2FS Security Labels"
+	depends on F2FS_FS_XATTR
+	help
+	  Security labels provide an access control facility to support Linux
+	  Security Models (LSMs) accepted by AppArmor, SELinux, Smack and TOMOYO
+	  Linux. This option enables an extended attribute handler for file
+	  security labels in the f2fs filesystem, so that it requires enabling
+	  the extended attribute support in advance. In particular you need this
+	  option if you use the setcap command to assign initial process capabi-
+	  lities to executables (the security.* extended attributes).
+
+	  If you are not using a security module, say N.
+
+config F2FS_CHECK_FS
+	bool "F2FS consistency checking feature"
+	depends on F2FS_FS
+	help
+	  Enables BUG_ONs which check the filesystem consistency in runtime.
+
+	  If you want to improve the performance, say N.
+
+config F2FS_FAULT_INJECTION
+	bool "F2FS fault injection facility"
+	depends on F2FS_FS
+	help
+	  Test F2FS to inject faults such as ENOMEM, ENOSPC, and so on.
+
+	  If unsure, say N.
+
+config F2FS_FS_COMPRESSION
+	bool "F2FS compression feature"
+	depends on F2FS_FS
+	help
+	  Enable filesystem-level compression on f2fs regular files,
+	  multiple back-end compression algorithms are supported.
+
+config F2FS_FS_LZO
+	bool "LZO compression support"
+	depends on F2FS_FS_COMPRESSION
+	default y
+	help
+	  Support LZO compress algorithm, if unsure, say Y.
+
+config F2FS_FS_LZORLE
+	bool "LZO-RLE compression support"
+	depends on F2FS_FS_LZO
+	default y
+	help
+	  Support LZO-RLE compress algorithm, if unsure, say Y.
+
+config F2FS_FS_LZ4
+	bool "LZ4 compression support"
+	depends on F2FS_FS_COMPRESSION
+	default y
+	help
+	  Support LZ4 compress algorithm, if unsure, say Y.
+
+config F2FS_FS_LZ4HC
+	bool "LZ4HC compression support"
+	depends on F2FS_FS_LZ4
+	default y
+	help
+	  Support LZ4HC compress algorithm, LZ4HC has compatible on-disk
+	  layout with LZ4, if unsure, say Y.
+
+config F2FS_FS_ZSTD
+	bool "ZSTD compression support"
+	depends on F2FS_FS_COMPRESSION
+	default y
+	help
+	  Support ZSTD compress algorithm, if unsure, say Y.
+
+config F2FS_IOSTAT
+	bool "F2FS IO statistics information"
+	depends on F2FS_FS
+	default y
+	help
+	  Support getting IO statistics through sysfs and printing out periodic
+	  IO statistics tracepoint events. You have to turn on "iostat_enable"
+	  sysfs node to enable this feature.
+
+config F2FS_UNFAIR_RWSEM
+	bool "F2FS unfair rw_semaphore"
+	depends on F2FS_FS && BLK_CGROUP
+	help
+	  Use unfair rw_semaphore, if system configured IO priority by block
+	  cgroup.