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, 56 insertions, 0 deletions

diff --git a/rust/zerocopy/rustdoc/style.css b/rust/zerocopy/rustdoc/style.css
new file mode 100644
index 000000000..d2d55ad2e
--- /dev/null
+++ b/rust/zerocopy/rustdoc/style.css
@@ -0,0 +1,56 @@
+/* SPDX-License-Identifier: (BSD-2-Clause OR Apache-2.0) OR MIT */
+/*
+Copyright 2026 The Fuchsia Authors
+
+Licensed under a BSD-style license <LICENSE-BSD>, Apache License, Version 2.0
+<LICENSE-APACHE or https://www.apache.org/licenses/LICENSE-2.0>, or the MIT
+license <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your option.
+This file may not be copied, modified, or distributed except according to
+those terms.
+*/
+
+.codegen-tabs {
+    display: grid;
+    grid-template-columns: repeat(var(--arity), minmax(200px, 1fr));
+    grid-template-rows: auto 1fr;
+    column-gap: 1rem;
+}
+
+.codegen-tabs:not(:has(> details[open]))::after {
+    grid-column: 1/-1;
+    content: 'Click one of the above headers to expand its contents.';
+    font-style: italic;
+    font-size: small;
+    text-align: center;
+}
+
+.codegen-tabs details {
+    display: grid;
+    grid-column: 1 / -1;
+    grid-row: 1 / span 2;
+    grid-template-columns: subgrid;
+    grid-template-rows: subgrid;
+}
+
+.codegen-tabs summary {
+    display: grid;
+    grid-column: var(--n) / span 1;
+    grid-row: 1;
+    z-index: 1;
+    border-bottom: 2px solid var(--headings-border-bottom-color);
+    cursor: pointer;
+}
+
+.codegen-tabs details[open] > summary {
+    background-color: var(--code-block-background-color);
+    border-bottom-color: var(--target-border-color);
+}
+
+.codegen-tabs details::details-content {
+    grid-column: 1 / -1;
+    grid-row: 2;
+}
+
+.codegen-tabs details:not([open])::details-content {
+    display: none;
+}