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, 411 insertions, 0 deletions

diff --git a/lib/crypto/sha3.c b/lib/crypto/sha3.c
new file mode 100644
index 000000000..286a2373c
--- /dev/null
+++ b/lib/crypto/sha3.c
@@ -0,0 +1,411 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * SHA-3, as specified in
+ * https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.202.pdf
+ *
+ * SHA-3 code by Jeff Garzik <jeff@garzik.org>
+ *               Ard Biesheuvel <ard.biesheuvel@linaro.org>
+ *               David Howells <dhowells@redhat.com>
+ *
+ * See also Documentation/crypto/sha3.rst
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+#include <crypto/sha3.h>
+#include <crypto/utils.h>
+#include <linux/export.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/unaligned.h>
+#include "fips-sha.h"
+
+/*
+ * On some 32-bit architectures, such as h8300, GCC ends up using over 1 KB of
+ * stack if the round calculation gets inlined into the loop in
+ * sha3_keccakf_generic().  On the other hand, on 64-bit architectures with
+ * plenty of [64-bit wide] general purpose registers, not inlining it severely
+ * hurts performance.  So let's use 64-bitness as a heuristic to decide whether
+ * to inline or not.
+ */
+#ifdef CONFIG_64BIT
+#define SHA3_INLINE inline
+#else
+#define SHA3_INLINE noinline
+#endif
+
+#define SHA3_KECCAK_ROUNDS 24
+
+static const u64 sha3_keccakf_rndc[SHA3_KECCAK_ROUNDS] = {
+	0x0000000000000001ULL, 0x0000000000008082ULL, 0x800000000000808aULL,
+	0x8000000080008000ULL, 0x000000000000808bULL, 0x0000000080000001ULL,
+	0x8000000080008081ULL, 0x8000000000008009ULL, 0x000000000000008aULL,
+	0x0000000000000088ULL, 0x0000000080008009ULL, 0x000000008000000aULL,
+	0x000000008000808bULL, 0x800000000000008bULL, 0x8000000000008089ULL,
+	0x8000000000008003ULL, 0x8000000000008002ULL, 0x8000000000000080ULL,
+	0x000000000000800aULL, 0x800000008000000aULL, 0x8000000080008081ULL,
+	0x8000000000008080ULL, 0x0000000080000001ULL, 0x8000000080008008ULL
+};
+
+/*
+ * Perform a single round of Keccak mixing.
+ */
+static SHA3_INLINE void sha3_keccakf_one_round_generic(u64 st[25], int round)
+{
+	u64 t[5], tt, bc[5];
+
+	/* Theta */
+	bc[0] = st[0] ^ st[5] ^ st[10] ^ st[15] ^ st[20];
+	bc[1] = st[1] ^ st[6] ^ st[11] ^ st[16] ^ st[21];
+	bc[2] = st[2] ^ st[7] ^ st[12] ^ st[17] ^ st[22];
+	bc[3] = st[3] ^ st[8] ^ st[13] ^ st[18] ^ st[23];
+	bc[4] = st[4] ^ st[9] ^ st[14] ^ st[19] ^ st[24];
+
+	t[0] = bc[4] ^ rol64(bc[1], 1);
+	t[1] = bc[0] ^ rol64(bc[2], 1);
+	t[2] = bc[1] ^ rol64(bc[3], 1);
+	t[3] = bc[2] ^ rol64(bc[4], 1);
+	t[4] = bc[3] ^ rol64(bc[0], 1);
+
+	st[0] ^= t[0];
+
+	/* Rho Pi */
+	tt = st[1];
+	st[ 1] = rol64(st[ 6] ^ t[1], 44);
+	st[ 6] = rol64(st[ 9] ^ t[4], 20);
+	st[ 9] = rol64(st[22] ^ t[2], 61);
+	st[22] = rol64(st[14] ^ t[4], 39);
+	st[14] = rol64(st[20] ^ t[0], 18);
+	st[20] = rol64(st[ 2] ^ t[2], 62);
+	st[ 2] = rol64(st[12] ^ t[2], 43);
+	st[12] = rol64(st[13] ^ t[3], 25);
+	st[13] = rol64(st[19] ^ t[4],  8);
+	st[19] = rol64(st[23] ^ t[3], 56);
+	st[23] = rol64(st[15] ^ t[0], 41);
+	st[15] = rol64(st[ 4] ^ t[4], 27);
+	st[ 4] = rol64(st[24] ^ t[4], 14);
+	st[24] = rol64(st[21] ^ t[1],  2);
+	st[21] = rol64(st[ 8] ^ t[3], 55);
+	st[ 8] = rol64(st[16] ^ t[1], 45);
+	st[16] = rol64(st[ 5] ^ t[0], 36);
+	st[ 5] = rol64(st[ 3] ^ t[3], 28);
+	st[ 3] = rol64(st[18] ^ t[3], 21);
+	st[18] = rol64(st[17] ^ t[2], 15);
+	st[17] = rol64(st[11] ^ t[1], 10);
+	st[11] = rol64(st[ 7] ^ t[2],  6);
+	st[ 7] = rol64(st[10] ^ t[0],  3);
+	st[10] = rol64(    tt ^ t[1],  1);
+
+	/* Chi */
+	bc[ 0] = ~st[ 1] & st[ 2];
+	bc[ 1] = ~st[ 2] & st[ 3];
+	bc[ 2] = ~st[ 3] & st[ 4];
+	bc[ 3] = ~st[ 4] & st[ 0];
+	bc[ 4] = ~st[ 0] & st[ 1];
+	st[ 0] ^= bc[ 0];
+	st[ 1] ^= bc[ 1];
+	st[ 2] ^= bc[ 2];
+	st[ 3] ^= bc[ 3];
+	st[ 4] ^= bc[ 4];
+
+	bc[ 0] = ~st[ 6] & st[ 7];
+	bc[ 1] = ~st[ 7] & st[ 8];
+	bc[ 2] = ~st[ 8] & st[ 9];
+	bc[ 3] = ~st[ 9] & st[ 5];
+	bc[ 4] = ~st[ 5] & st[ 6];
+	st[ 5] ^= bc[ 0];
+	st[ 6] ^= bc[ 1];
+	st[ 7] ^= bc[ 2];
+	st[ 8] ^= bc[ 3];
+	st[ 9] ^= bc[ 4];
+
+	bc[ 0] = ~st[11] & st[12];
+	bc[ 1] = ~st[12] & st[13];
+	bc[ 2] = ~st[13] & st[14];
+	bc[ 3] = ~st[14] & st[10];
+	bc[ 4] = ~st[10] & st[11];
+	st[10] ^= bc[ 0];
+	st[11] ^= bc[ 1];
+	st[12] ^= bc[ 2];
+	st[13] ^= bc[ 3];
+	st[14] ^= bc[ 4];
+
+	bc[ 0] = ~st[16] & st[17];
+	bc[ 1] = ~st[17] & st[18];
+	bc[ 2] = ~st[18] & st[19];
+	bc[ 3] = ~st[19] & st[15];
+	bc[ 4] = ~st[15] & st[16];
+	st[15] ^= bc[ 0];
+	st[16] ^= bc[ 1];
+	st[17] ^= bc[ 2];
+	st[18] ^= bc[ 3];
+	st[19] ^= bc[ 4];
+
+	bc[ 0] = ~st[21] & st[22];
+	bc[ 1] = ~st[22] & st[23];
+	bc[ 2] = ~st[23] & st[24];
+	bc[ 3] = ~st[24] & st[20];
+	bc[ 4] = ~st[20] & st[21];
+	st[20] ^= bc[ 0];
+	st[21] ^= bc[ 1];
+	st[22] ^= bc[ 2];
+	st[23] ^= bc[ 3];
+	st[24] ^= bc[ 4];
+
+	/* Iota */
+	st[0] ^= sha3_keccakf_rndc[round];
+}
+
+/* Generic implementation of the Keccak-f[1600] permutation */
+static void sha3_keccakf_generic(struct sha3_state *state)
+{
+	/*
+	 * Temporarily convert the state words from little-endian to native-
+	 * endian so that they can be operated on.  Note that on little-endian
+	 * machines this conversion is a no-op and is optimized out.
+	 */
+
+	for (int i = 0; i < ARRAY_SIZE(state->words); i++)
+		state->native_words[i] = le64_to_cpu(state->words[i]);
+
+	for (int round = 0; round < SHA3_KECCAK_ROUNDS; round++)
+		sha3_keccakf_one_round_generic(state->native_words, round);
+
+	for (int i = 0; i < ARRAY_SIZE(state->words); i++)
+		state->words[i] = cpu_to_le64(state->native_words[i]);
+}
+
+/*
+ * Generic implementation of absorbing the given nonzero number of full blocks
+ * into the sponge function Keccak[r=8*block_size, c=1600-8*block_size].
+ */
+static void __maybe_unused
+sha3_absorb_blocks_generic(struct sha3_state *state, const u8 *data,
+			   size_t nblocks, size_t block_size)
+{
+	do {
+		for (size_t i = 0; i < block_size; i += 8)
+			state->words[i / 8] ^= get_unaligned((__le64 *)&data[i]);
+		sha3_keccakf_generic(state);
+		data += block_size;
+	} while (--nblocks);
+}
+
+#ifdef CONFIG_CRYPTO_LIB_SHA3_ARCH
+#include "sha3.h" /* $(SRCARCH)/sha3.h */
+#else
+#define sha3_keccakf		sha3_keccakf_generic
+#define sha3_absorb_blocks	sha3_absorb_blocks_generic
+#endif
+
+void __sha3_update(struct __sha3_ctx *ctx, const u8 *in, size_t in_len)
+{
+	const size_t block_size = ctx->block_size;
+	size_t absorb_offset = ctx->absorb_offset;
+
+	/* Warn if squeezing has already begun. */
+	WARN_ON_ONCE(absorb_offset >= block_size);
+
+	if (absorb_offset && absorb_offset + in_len >= block_size) {
+		crypto_xor(&ctx->state.bytes[absorb_offset], in,
+			   block_size - absorb_offset);
+		in += block_size - absorb_offset;
+		in_len -= block_size - absorb_offset;
+		sha3_keccakf(&ctx->state);
+		absorb_offset = 0;
+	}
+
+	if (in_len >= block_size) {
+		size_t nblocks = in_len / block_size;
+
+		sha3_absorb_blocks(&ctx->state, in, nblocks, block_size);
+		in += nblocks * block_size;
+		in_len -= nblocks * block_size;
+	}
+
+	if (in_len) {
+		crypto_xor(&ctx->state.bytes[absorb_offset], in, in_len);
+		absorb_offset += in_len;
+	}
+	ctx->absorb_offset = absorb_offset;
+}
+EXPORT_SYMBOL_GPL(__sha3_update);
+
+void sha3_final(struct sha3_ctx *sha3_ctx, u8 *out)
+{
+	struct __sha3_ctx *ctx = &sha3_ctx->ctx;
+
+	ctx->state.bytes[ctx->absorb_offset] ^= 0x06;
+	ctx->state.bytes[ctx->block_size - 1] ^= 0x80;
+	sha3_keccakf(&ctx->state);
+	memcpy(out, ctx->state.bytes, ctx->digest_size);
+	sha3_zeroize_ctx(sha3_ctx);
+}
+EXPORT_SYMBOL_GPL(sha3_final);
+
+void shake_squeeze(struct shake_ctx *shake_ctx, u8 *out, size_t out_len)
+{
+	struct __sha3_ctx *ctx = &shake_ctx->ctx;
+	const size_t block_size = ctx->block_size;
+	size_t squeeze_offset = ctx->squeeze_offset;
+
+	if (ctx->absorb_offset < block_size) {
+		/* First squeeze: */
+
+		/* Add the domain separation suffix and padding. */
+		ctx->state.bytes[ctx->absorb_offset] ^= 0x1f;
+		ctx->state.bytes[block_size - 1] ^= 0x80;
+
+		/* Indicate that squeezing has begun. */
+		ctx->absorb_offset = block_size;
+
+		/*
+		 * Indicate that no output is pending yet, i.e. sha3_keccakf()
+		 * will need to be called before the first copy.
+		 */
+		squeeze_offset = block_size;
+	}
+	while (out_len) {
+		if (squeeze_offset == block_size) {
+			sha3_keccakf(&ctx->state);
+			squeeze_offset = 0;
+		}
+		size_t copy = min(out_len, block_size - squeeze_offset);
+
+		memcpy(out, &ctx->state.bytes[squeeze_offset], copy);
+		out += copy;
+		out_len -= copy;
+		squeeze_offset += copy;
+	}
+	ctx->squeeze_offset = squeeze_offset;
+}
+EXPORT_SYMBOL_GPL(shake_squeeze);
+
+#ifndef sha3_224_arch
+static inline bool sha3_224_arch(const u8 *in, size_t in_len,
+				 u8 out[SHA3_224_DIGEST_SIZE])
+{
+	return false;
+}
+#endif
+#ifndef sha3_256_arch
+static inline bool sha3_256_arch(const u8 *in, size_t in_len,
+				 u8 out[SHA3_256_DIGEST_SIZE])
+{
+	return false;
+}
+#endif
+#ifndef sha3_384_arch
+static inline bool sha3_384_arch(const u8 *in, size_t in_len,
+				 u8 out[SHA3_384_DIGEST_SIZE])
+{
+	return false;
+}
+#endif
+#ifndef sha3_512_arch
+static inline bool sha3_512_arch(const u8 *in, size_t in_len,
+				 u8 out[SHA3_512_DIGEST_SIZE])
+{
+	return false;
+}
+#endif
+
+void sha3_224(const u8 *in, size_t in_len, u8 out[SHA3_224_DIGEST_SIZE])
+{
+	struct sha3_ctx ctx;
+
+	if (sha3_224_arch(in, in_len, out))
+		return;
+	sha3_224_init(&ctx);
+	sha3_update(&ctx, in, in_len);
+	sha3_final(&ctx, out);
+}
+EXPORT_SYMBOL_GPL(sha3_224);
+
+void sha3_256(const u8 *in, size_t in_len, u8 out[SHA3_256_DIGEST_SIZE])
+{
+	struct sha3_ctx ctx;
+
+	if (sha3_256_arch(in, in_len, out))
+		return;
+	sha3_256_init(&ctx);
+	sha3_update(&ctx, in, in_len);
+	sha3_final(&ctx, out);
+}
+EXPORT_SYMBOL_GPL(sha3_256);
+
+void sha3_384(const u8 *in, size_t in_len, u8 out[SHA3_384_DIGEST_SIZE])
+{
+	struct sha3_ctx ctx;
+
+	if (sha3_384_arch(in, in_len, out))
+		return;
+	sha3_384_init(&ctx);
+	sha3_update(&ctx, in, in_len);
+	sha3_final(&ctx, out);
+}
+EXPORT_SYMBOL_GPL(sha3_384);
+
+void sha3_512(const u8 *in, size_t in_len, u8 out[SHA3_512_DIGEST_SIZE])
+{
+	struct sha3_ctx ctx;
+
+	if (sha3_512_arch(in, in_len, out))
+		return;
+	sha3_512_init(&ctx);
+	sha3_update(&ctx, in, in_len);
+	sha3_final(&ctx, out);
+}
+EXPORT_SYMBOL_GPL(sha3_512);
+
+void shake128(const u8 *in, size_t in_len, u8 *out, size_t out_len)
+{
+	struct shake_ctx ctx;
+
+	shake128_init(&ctx);
+	shake_update(&ctx, in, in_len);
+	shake_squeeze(&ctx, out, out_len);
+	shake_zeroize_ctx(&ctx);
+}
+EXPORT_SYMBOL_GPL(shake128);
+
+void shake256(const u8 *in, size_t in_len, u8 *out, size_t out_len)
+{
+	struct shake_ctx ctx;
+
+	shake256_init(&ctx);
+	shake_update(&ctx, in, in_len);
+	shake_squeeze(&ctx, out, out_len);
+	shake_zeroize_ctx(&ctx);
+}
+EXPORT_SYMBOL_GPL(shake256);
+
+#if defined(sha3_mod_init_arch) || defined(CONFIG_CRYPTO_FIPS)
+static int __init sha3_mod_init(void)
+{
+#ifdef sha3_mod_init_arch
+	sha3_mod_init_arch();
+#endif
+	if (fips_enabled) {
+		/*
+		 * FIPS cryptographic algorithm self-test.  As per the FIPS
+		 * Implementation Guidance, testing any SHA-3 algorithm
+		 * satisfies the test requirement for all of them.
+		 */
+		u8 hash[SHA3_256_DIGEST_SIZE];
+
+		sha3_256(fips_test_data, sizeof(fips_test_data), hash);
+		if (memcmp(fips_test_sha3_256_value, hash, sizeof(hash)) != 0)
+			panic("sha3: FIPS self-test failed\n");
+	}
+	return 0;
+}
+subsys_initcall(sha3_mod_init);
+
+static void __exit sha3_mod_exit(void)
+{
+}
+module_exit(sha3_mod_exit);
+#endif
+
+MODULE_DESCRIPTION("SHA-3 library functions");
+MODULE_LICENSE("GPL");