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, 78 insertions, 0 deletions

diff --git a/lib/crypto/fips-aes.h b/lib/crypto/fips-aes.h
new file mode 100644
index 000000000..2a1746606
--- /dev/null
+++ b/lib/crypto/fips-aes.h
@@ -0,0 +1,78 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* This file was generated by: gen-fips-testvecs.py */
+/* clang-format off */
+
+#include <linux/fips.h>
+
+static const u8 fips_test_data[] __initconst __maybe_unused = {
+	0x66, 0x69, 0x70, 0x73, 0x20, 0x74, 0x65, 0x73,
+	0x74, 0x20, 0x64, 0x61, 0x74, 0x61, 0x00, 0x00,
+};
+
+static const u8 fips_test_ad[] __initconst __maybe_unused = {
+	0x66, 0x69, 0x70, 0x73, 0x20, 0x74, 0x65, 0x73,
+	0x74, 0x20, 0x61, 0x64, 0x00, 0x00, 0x00, 0x00,
+};
+
+static const u8 fips_test_iv[] __initconst __maybe_unused = {
+	0x66, 0x69, 0x70, 0x73, 0x20, 0x74, 0x65, 0x73,
+	0x74, 0x20, 0x69, 0x76, 0x00, 0x00, 0x00, 0x00,
+};
+
+static const u8 fips_test_key[] __initconst __maybe_unused = {
+	0x66, 0x69, 0x70, 0x73, 0x20, 0x74, 0x65, 0x73,
+	0x74, 0x20, 0x6b, 0x65, 0x79, 0x00, 0x00, 0x00,
+};
+
+static const u8 fips_test_xts_key[] __initconst __maybe_unused = {
+	0x6b, 0x65, 0x79, 0x31, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x6b, 0x65, 0x79, 0x32, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+};
+
+static const u8 fips_test_aes_cmac_value[] __initconst __maybe_unused = {
+	0xc5, 0x88, 0x28, 0x55, 0xd7, 0x2c, 0x00, 0xb6,
+	0x6a, 0xa7, 0xfc, 0x82, 0x90, 0x81, 0xcf, 0x18,
+};
+
+static const u8 fips_test_aes_ecb_ctext[] __initconst __maybe_unused = {
+	0x47, 0x76, 0x48, 0xaf, 0x1b, 0xd8, 0x4c, 0xe6,
+	0xb5, 0xa7, 0x20, 0x8d, 0x64, 0x88, 0xbc, 0x3f,
+};
+
+static const u8 fips_test_aes_cbc_ctext[] __initconst __maybe_unused = {
+	0xc8, 0x7d, 0x7c, 0x25, 0xba, 0x15, 0xf7, 0xe1,
+	0x08, 0xa0, 0xd0, 0x7a, 0x20, 0x37, 0xaf, 0x5e,
+};
+
+static const u8 fips_test_aes_cbc_cts_ctext[] __initconst __maybe_unused = {
+	0x36, 0x8e, 0x37, 0xb4, 0x78, 0xe2, 0x88, 0x59,
+	0xd5, 0xe8, 0x17, 0x65, 0x5c, 0xa1, 0x25, 0xe6,
+	0xc8, 0x7d, 0x7c, 0x25, 0xba, 0x15, 0xf7, 0xe1,
+	0x08, 0xa0, 0xd0, 0x7a, 0x20, 0x37, 0xaf, 0x5e,
+};
+
+static const u8 fips_test_aes_ctr_ctext[] __initconst __maybe_unused = {
+	0x95, 0xf4, 0xf4, 0x7a, 0xc8, 0xa2, 0x53, 0x73,
+	0x53, 0x8f, 0x95, 0xfc, 0x18, 0xfe, 0x58, 0x2f,
+};
+
+static const u8 fips_test_aes_xts_ctext[] __initconst __maybe_unused = {
+	0xd4, 0x51, 0x7f, 0x01, 0x14, 0x91, 0x16, 0x29,
+	0x26, 0xbe, 0xec, 0x9b, 0x90, 0xed, 0x59, 0x30,
+};
+
+static const u8 fips_test_aes_gcm_ctext_and_tag[] __initconst __maybe_unused = {
+	0x12, 0x0c, 0x5d, 0x03, 0x32, 0x93, 0x13, 0x44,
+	0x06, 0x35, 0x26, 0x9d, 0xe0, 0xea, 0xbc, 0xe2,
+	0x30, 0xa9, 0xa4, 0x15, 0xc5, 0x3d, 0xb3, 0xf9,
+	0x30, 0x82, 0xdf, 0x9c, 0xd8, 0xc4, 0x3f, 0x2f,
+};
+
+static const u8 fips_test_aes_ccm_ctext_and_tag[] __initconst __maybe_unused = {
+	0x11, 0x8e, 0x01, 0xcb, 0xb5, 0x22, 0x6d, 0xb4,
+	0x66, 0x98, 0x97, 0x1d, 0x35, 0x53, 0x78, 0xdd,
+	0xd1, 0xc5, 0xff, 0xb6, 0x90, 0xcf, 0xb1, 0xf2,
+	0x87, 0x99, 0xd6, 0x1e, 0xd5, 0xd1, 0xed, 0x63,
+};