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, 47 insertions, 0 deletions

diff --git a/Documentation/admin-guide/sysctl/crypto.rst b/Documentation/admin-guide/sysctl/crypto.rst
new file mode 100644
index 000000000..b707bd314
--- /dev/null
+++ b/Documentation/admin-guide/sysctl/crypto.rst
@@ -0,0 +1,47 @@
+=================
+/proc/sys/crypto/
+=================
+
+These files show up in ``/proc/sys/crypto/``, depending on the
+kernel configuration:
+
+.. contents:: :local:
+
+fips_enabled
+============
+
+Read-only flag that indicates whether FIPS mode is enabled.
+
+- ``0``: FIPS mode is disabled (default).
+- ``1``: FIPS mode is enabled.
+
+This value is set at boot time via the ``fips=1`` kernel command line
+parameter. When enabled, the cryptographic API will restrict the use
+of certain algorithms and perform self-tests to ensure compliance with
+FIPS (Federal Information Processing Standards) requirements, such as
+FIPS 140-2 and the newer FIPS 140-3, depending on the kernel
+configuration and the module in use.
+
+fips_name
+=========
+
+Read-only file that contains the name of the FIPS module currently in use.
+The value is typically configured via the ``CONFIG_CRYPTO_FIPS_NAME``
+kernel configuration option.
+
+fips_version
+============
+
+Read-only file that contains the version string of the FIPS module.
+If ``CONFIG_CRYPTO_FIPS_CUSTOM_VERSION`` is set, it uses the value from
+``CONFIG_CRYPTO_FIPS_VERSION``. Otherwise, it defaults to the kernel
+release version (``UTS_RELEASE``).
+
+Copyright (c) 2026, Shubham Chakraborty <chakrabortyshubham66@gmail.com>
+
+For general info and legal blurb, please look in
+Documentation/admin-guide/sysctl/index.rst.
+
+.. See scripts/check-sysctl-docs to keep this up to date:
+.. scripts/check-sysctl-docs -vtable="crypto" \
+..         $(git grep -l register_sysctl_)