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, 37 insertions, 0 deletions

diff --git a/security/landlock/Kconfig b/security/landlock/Kconfig
new file mode 100644
index 000000000..3f1493402
--- /dev/null
+++ b/security/landlock/Kconfig
@@ -0,0 +1,37 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+config SECURITY_LANDLOCK
+	bool "Landlock support"
+	depends on SECURITY
+	select SECURITY_NETWORK
+	select SECURITY_PATH
+	help
+	  Landlock is a sandboxing mechanism that enables processes to restrict
+	  themselves (and their future children) by gradually enforcing
+	  tailored access control policies.  A Landlock security policy is a
+	  set of access rights (e.g. open a file in read-only, make a
+	  directory, etc.) tied to a file hierarchy.  Such policy can be
+	  configured and enforced by any processes for themselves using the
+	  dedicated system calls: landlock_create_ruleset(),
+	  landlock_add_rule(), and landlock_restrict_self().
+
+	  See Documentation/userspace-api/landlock.rst for further information.
+
+	  If you are unsure how to answer this question, answer N.  Otherwise,
+	  you should also prepend "landlock," to the content of CONFIG_LSM to
+	  enable Landlock at boot time.
+
+config SECURITY_LANDLOCK_KUNIT_TEST
+	bool "KUnit tests for Landlock" if !KUNIT_ALL_TESTS
+	depends on KUNIT=y
+	depends on SECURITY_LANDLOCK
+	default KUNIT_ALL_TESTS
+	help
+	  Build KUnit tests for Landlock.
+
+	  See the KUnit documentation in Documentation/dev-tools/kunit
+
+	  Run all KUnit tests for Landlock with:
+	  ./tools/testing/kunit/kunit.py run --kunitconfig security/landlock
+
+	  If you are unsure how to answer this question, answer N.