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, 440 insertions, 0 deletions

diff --git a/lib/crypto/sha512.c b/lib/crypto/sha512.c
new file mode 100644
index 000000000..0dd6fb4ca
--- /dev/null
+++ b/lib/crypto/sha512.c
@@ -0,0 +1,440 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * SHA-384, SHA-512, HMAC-SHA384, and HMAC-SHA512 library functions
+ *
+ * Copyright (c) Jean-Luc Cooke <jlcooke@certainkey.com>
+ * Copyright (c) Andrew McDonald <andrew@mcdonald.org.uk>
+ * Copyright (c) 2003 Kyle McMartin <kyle@debian.org>
+ * Copyright 2025 Google LLC
+ */
+
+#include <crypto/hmac.h>
+#include <crypto/sha2.h>
+#include <linux/export.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/overflow.h>
+#include <linux/string.h>
+#include <linux/unaligned.h>
+#include <linux/wordpart.h>
+#include "fips-sha.h"
+
+static const struct sha512_block_state sha384_iv = {
+	.h = {
+		SHA384_H0, SHA384_H1, SHA384_H2, SHA384_H3,
+		SHA384_H4, SHA384_H5, SHA384_H6, SHA384_H7,
+	},
+};
+
+static const struct sha512_block_state sha512_iv = {
+	.h = {
+		SHA512_H0, SHA512_H1, SHA512_H2, SHA512_H3,
+		SHA512_H4, SHA512_H5, SHA512_H6, SHA512_H7,
+	},
+};
+
+static const u64 sha512_K[80] = {
+	0x428a2f98d728ae22ULL, 0x7137449123ef65cdULL, 0xb5c0fbcfec4d3b2fULL,
+	0xe9b5dba58189dbbcULL, 0x3956c25bf348b538ULL, 0x59f111f1b605d019ULL,
+	0x923f82a4af194f9bULL, 0xab1c5ed5da6d8118ULL, 0xd807aa98a3030242ULL,
+	0x12835b0145706fbeULL, 0x243185be4ee4b28cULL, 0x550c7dc3d5ffb4e2ULL,
+	0x72be5d74f27b896fULL, 0x80deb1fe3b1696b1ULL, 0x9bdc06a725c71235ULL,
+	0xc19bf174cf692694ULL, 0xe49b69c19ef14ad2ULL, 0xefbe4786384f25e3ULL,
+	0x0fc19dc68b8cd5b5ULL, 0x240ca1cc77ac9c65ULL, 0x2de92c6f592b0275ULL,
+	0x4a7484aa6ea6e483ULL, 0x5cb0a9dcbd41fbd4ULL, 0x76f988da831153b5ULL,
+	0x983e5152ee66dfabULL, 0xa831c66d2db43210ULL, 0xb00327c898fb213fULL,
+	0xbf597fc7beef0ee4ULL, 0xc6e00bf33da88fc2ULL, 0xd5a79147930aa725ULL,
+	0x06ca6351e003826fULL, 0x142929670a0e6e70ULL, 0x27b70a8546d22ffcULL,
+	0x2e1b21385c26c926ULL, 0x4d2c6dfc5ac42aedULL, 0x53380d139d95b3dfULL,
+	0x650a73548baf63deULL, 0x766a0abb3c77b2a8ULL, 0x81c2c92e47edaee6ULL,
+	0x92722c851482353bULL, 0xa2bfe8a14cf10364ULL, 0xa81a664bbc423001ULL,
+	0xc24b8b70d0f89791ULL, 0xc76c51a30654be30ULL, 0xd192e819d6ef5218ULL,
+	0xd69906245565a910ULL, 0xf40e35855771202aULL, 0x106aa07032bbd1b8ULL,
+	0x19a4c116b8d2d0c8ULL, 0x1e376c085141ab53ULL, 0x2748774cdf8eeb99ULL,
+	0x34b0bcb5e19b48a8ULL, 0x391c0cb3c5c95a63ULL, 0x4ed8aa4ae3418acbULL,
+	0x5b9cca4f7763e373ULL, 0x682e6ff3d6b2b8a3ULL, 0x748f82ee5defb2fcULL,
+	0x78a5636f43172f60ULL, 0x84c87814a1f0ab72ULL, 0x8cc702081a6439ecULL,
+	0x90befffa23631e28ULL, 0xa4506cebde82bde9ULL, 0xbef9a3f7b2c67915ULL,
+	0xc67178f2e372532bULL, 0xca273eceea26619cULL, 0xd186b8c721c0c207ULL,
+	0xeada7dd6cde0eb1eULL, 0xf57d4f7fee6ed178ULL, 0x06f067aa72176fbaULL,
+	0x0a637dc5a2c898a6ULL, 0x113f9804bef90daeULL, 0x1b710b35131c471bULL,
+	0x28db77f523047d84ULL, 0x32caab7b40c72493ULL, 0x3c9ebe0a15c9bebcULL,
+	0x431d67c49c100d4cULL, 0x4cc5d4becb3e42b6ULL, 0x597f299cfc657e2aULL,
+	0x5fcb6fab3ad6faecULL, 0x6c44198c4a475817ULL,
+};
+
+#define Ch(x, y, z) ((z) ^ ((x) & ((y) ^ (z))))
+#define Maj(x, y, z) (((x) & (y)) | ((z) & ((x) | (y))))
+#define e0(x) (ror64((x), 28) ^ ror64((x), 34) ^ ror64((x), 39))
+#define e1(x) (ror64((x), 14) ^ ror64((x), 18) ^ ror64((x), 41))
+#define s0(x) (ror64((x), 1) ^ ror64((x), 8) ^ ((x) >> 7))
+#define s1(x) (ror64((x), 19) ^ ror64((x), 61) ^ ((x) >> 6))
+
+static void sha512_block_generic(struct sha512_block_state *state,
+				 const u8 *data)
+{
+	u64 a = state->h[0];
+	u64 b = state->h[1];
+	u64 c = state->h[2];
+	u64 d = state->h[3];
+	u64 e = state->h[4];
+	u64 f = state->h[5];
+	u64 g = state->h[6];
+	u64 h = state->h[7];
+	u64 t1, t2;
+	u64 W[16];
+
+	for (int j = 0; j < 16; j++)
+		W[j] = get_unaligned_be64(data + j * sizeof(u64));
+
+	for (int i = 0; i < 80; i += 8) {
+		if ((i & 15) == 0 && i != 0) {
+			for (int j = 0; j < 16; j++) {
+				W[j & 15] += s1(W[(j - 2) & 15]) +
+					     W[(j - 7) & 15] +
+					     s0(W[(j - 15) & 15]);
+			}
+		}
+		t1 = h + e1(e) + Ch(e, f, g) + sha512_K[i]   + W[(i & 15)];
+		t2 = e0(a) + Maj(a, b, c);    d += t1;    h = t1 + t2;
+		t1 = g + e1(d) + Ch(d, e, f) + sha512_K[i+1] + W[(i & 15) + 1];
+		t2 = e0(h) + Maj(h, a, b);    c += t1;    g = t1 + t2;
+		t1 = f + e1(c) + Ch(c, d, e) + sha512_K[i+2] + W[(i & 15) + 2];
+		t2 = e0(g) + Maj(g, h, a);    b += t1;    f = t1 + t2;
+		t1 = e + e1(b) + Ch(b, c, d) + sha512_K[i+3] + W[(i & 15) + 3];
+		t2 = e0(f) + Maj(f, g, h);    a += t1;    e = t1 + t2;
+		t1 = d + e1(a) + Ch(a, b, c) + sha512_K[i+4] + W[(i & 15) + 4];
+		t2 = e0(e) + Maj(e, f, g);    h += t1;    d = t1 + t2;
+		t1 = c + e1(h) + Ch(h, a, b) + sha512_K[i+5] + W[(i & 15) + 5];
+		t2 = e0(d) + Maj(d, e, f);    g += t1;    c = t1 + t2;
+		t1 = b + e1(g) + Ch(g, h, a) + sha512_K[i+6] + W[(i & 15) + 6];
+		t2 = e0(c) + Maj(c, d, e);    f += t1;    b = t1 + t2;
+		t1 = a + e1(f) + Ch(f, g, h) + sha512_K[i+7] + W[(i & 15) + 7];
+		t2 = e0(b) + Maj(b, c, d);    e += t1;    a = t1 + t2;
+	}
+
+	state->h[0] += a;
+	state->h[1] += b;
+	state->h[2] += c;
+	state->h[3] += d;
+	state->h[4] += e;
+	state->h[5] += f;
+	state->h[6] += g;
+	state->h[7] += h;
+}
+
+static void __maybe_unused
+sha512_blocks_generic(struct sha512_block_state *state,
+		      const u8 *data, size_t nblocks)
+{
+	do {
+		sha512_block_generic(state, data);
+		data += SHA512_BLOCK_SIZE;
+	} while (--nblocks);
+}
+
+#ifdef CONFIG_CRYPTO_LIB_SHA512_ARCH
+#include "sha512.h" /* $(SRCARCH)/sha512.h */
+#else
+#define sha512_blocks sha512_blocks_generic
+#endif
+
+static void __sha512_init(struct __sha512_ctx *ctx,
+			  const struct sha512_block_state *iv,
+			  u64 initial_bytecount)
+{
+	ctx->state = *iv;
+	ctx->bytecount_lo = initial_bytecount;
+	ctx->bytecount_hi = 0;
+}
+
+void sha384_init(struct sha384_ctx *ctx)
+{
+	__sha512_init(&ctx->ctx, &sha384_iv, 0);
+}
+EXPORT_SYMBOL_GPL(sha384_init);
+
+void sha512_init(struct sha512_ctx *ctx)
+{
+	__sha512_init(&ctx->ctx, &sha512_iv, 0);
+}
+EXPORT_SYMBOL_GPL(sha512_init);
+
+void __sha512_update(struct __sha512_ctx *ctx, const u8 *data, size_t len)
+{
+	size_t partial = ctx->bytecount_lo % SHA512_BLOCK_SIZE;
+
+	if (check_add_overflow(ctx->bytecount_lo, len, &ctx->bytecount_lo))
+		ctx->bytecount_hi++;
+
+	if (partial + len >= SHA512_BLOCK_SIZE) {
+		size_t nblocks;
+
+		if (partial) {
+			size_t l = SHA512_BLOCK_SIZE - partial;
+
+			memcpy(&ctx->buf[partial], data, l);
+			data += l;
+			len -= l;
+
+			sha512_blocks(&ctx->state, ctx->buf, 1);
+		}
+
+		nblocks = len / SHA512_BLOCK_SIZE;
+		len %= SHA512_BLOCK_SIZE;
+
+		if (nblocks) {
+			sha512_blocks(&ctx->state, data, nblocks);
+			data += nblocks * SHA512_BLOCK_SIZE;
+		}
+		partial = 0;
+	}
+	if (len)
+		memcpy(&ctx->buf[partial], data, len);
+}
+EXPORT_SYMBOL_GPL(__sha512_update);
+
+static void __sha512_final(struct __sha512_ctx *ctx,
+			   u8 *out, size_t digest_size)
+{
+	u64 bitcount_hi = (ctx->bytecount_hi << 3) | (ctx->bytecount_lo >> 61);
+	u64 bitcount_lo = ctx->bytecount_lo << 3;
+	size_t partial = ctx->bytecount_lo % SHA512_BLOCK_SIZE;
+
+	ctx->buf[partial++] = 0x80;
+	if (partial > SHA512_BLOCK_SIZE - 16) {
+		memset(&ctx->buf[partial], 0, SHA512_BLOCK_SIZE - partial);
+		sha512_blocks(&ctx->state, ctx->buf, 1);
+		partial = 0;
+	}
+	memset(&ctx->buf[partial], 0, SHA512_BLOCK_SIZE - 16 - partial);
+	*(__be64 *)&ctx->buf[SHA512_BLOCK_SIZE - 16] = cpu_to_be64(bitcount_hi);
+	*(__be64 *)&ctx->buf[SHA512_BLOCK_SIZE - 8] = cpu_to_be64(bitcount_lo);
+	sha512_blocks(&ctx->state, ctx->buf, 1);
+
+	for (size_t i = 0; i < digest_size; i += 8)
+		put_unaligned_be64(ctx->state.h[i / 8], out + i);
+}
+
+void sha384_final(struct sha384_ctx *ctx, u8 out[SHA384_DIGEST_SIZE])
+{
+	__sha512_final(&ctx->ctx, out, SHA384_DIGEST_SIZE);
+	memzero_explicit(ctx, sizeof(*ctx));
+}
+EXPORT_SYMBOL_GPL(sha384_final);
+
+void sha512_final(struct sha512_ctx *ctx, u8 out[SHA512_DIGEST_SIZE])
+{
+	__sha512_final(&ctx->ctx, out, SHA512_DIGEST_SIZE);
+	memzero_explicit(ctx, sizeof(*ctx));
+}
+EXPORT_SYMBOL_GPL(sha512_final);
+
+void sha384(const u8 *data, size_t len, u8 out[SHA384_DIGEST_SIZE])
+{
+	struct sha384_ctx ctx;
+
+	sha384_init(&ctx);
+	sha384_update(&ctx, data, len);
+	sha384_final(&ctx, out);
+}
+EXPORT_SYMBOL_GPL(sha384);
+
+void sha512(const u8 *data, size_t len, u8 out[SHA512_DIGEST_SIZE])
+{
+	struct sha512_ctx ctx;
+
+	sha512_init(&ctx);
+	sha512_update(&ctx, data, len);
+	sha512_final(&ctx, out);
+}
+EXPORT_SYMBOL_GPL(sha512);
+
+static void __hmac_sha512_preparekey(struct sha512_block_state *istate,
+				     struct sha512_block_state *ostate,
+				     const u8 *raw_key, size_t raw_key_len,
+				     const struct sha512_block_state *iv)
+{
+	union {
+		u8 b[SHA512_BLOCK_SIZE];
+		unsigned long w[SHA512_BLOCK_SIZE / sizeof(unsigned long)];
+	} derived_key = { 0 };
+
+	if (unlikely(raw_key_len > SHA512_BLOCK_SIZE)) {
+		if (iv == &sha384_iv)
+			sha384(raw_key, raw_key_len, derived_key.b);
+		else
+			sha512(raw_key, raw_key_len, derived_key.b);
+	} else {
+		memcpy(derived_key.b, raw_key, raw_key_len);
+	}
+
+	for (size_t i = 0; i < ARRAY_SIZE(derived_key.w); i++)
+		derived_key.w[i] ^= REPEAT_BYTE(HMAC_IPAD_VALUE);
+	*istate = *iv;
+	sha512_blocks(istate, derived_key.b, 1);
+
+	for (size_t i = 0; i < ARRAY_SIZE(derived_key.w); i++)
+		derived_key.w[i] ^= REPEAT_BYTE(HMAC_OPAD_VALUE ^
+						HMAC_IPAD_VALUE);
+	*ostate = *iv;
+	sha512_blocks(ostate, derived_key.b, 1);
+
+	memzero_explicit(&derived_key, sizeof(derived_key));
+}
+
+void hmac_sha384_preparekey(struct hmac_sha384_key *key,
+			    const u8 *raw_key, size_t raw_key_len)
+{
+	__hmac_sha512_preparekey(&key->key.istate, &key->key.ostate,
+				 raw_key, raw_key_len, &sha384_iv);
+}
+EXPORT_SYMBOL_GPL(hmac_sha384_preparekey);
+
+void hmac_sha512_preparekey(struct hmac_sha512_key *key,
+			    const u8 *raw_key, size_t raw_key_len)
+{
+	__hmac_sha512_preparekey(&key->key.istate, &key->key.ostate,
+				 raw_key, raw_key_len, &sha512_iv);
+}
+EXPORT_SYMBOL_GPL(hmac_sha512_preparekey);
+
+void __hmac_sha512_init(struct __hmac_sha512_ctx *ctx,
+			const struct __hmac_sha512_key *key)
+{
+	__sha512_init(&ctx->sha_ctx, &key->istate, SHA512_BLOCK_SIZE);
+	ctx->ostate = key->ostate;
+}
+EXPORT_SYMBOL_GPL(__hmac_sha512_init);
+
+void hmac_sha384_init_usingrawkey(struct hmac_sha384_ctx *ctx,
+				  const u8 *raw_key, size_t raw_key_len)
+{
+	__hmac_sha512_preparekey(&ctx->ctx.sha_ctx.state, &ctx->ctx.ostate,
+				 raw_key, raw_key_len, &sha384_iv);
+	ctx->ctx.sha_ctx.bytecount_lo = SHA512_BLOCK_SIZE;
+	ctx->ctx.sha_ctx.bytecount_hi = 0;
+}
+EXPORT_SYMBOL_GPL(hmac_sha384_init_usingrawkey);
+
+void hmac_sha512_init_usingrawkey(struct hmac_sha512_ctx *ctx,
+				  const u8 *raw_key, size_t raw_key_len)
+{
+	__hmac_sha512_preparekey(&ctx->ctx.sha_ctx.state, &ctx->ctx.ostate,
+				 raw_key, raw_key_len, &sha512_iv);
+	ctx->ctx.sha_ctx.bytecount_lo = SHA512_BLOCK_SIZE;
+	ctx->ctx.sha_ctx.bytecount_hi = 0;
+}
+EXPORT_SYMBOL_GPL(hmac_sha512_init_usingrawkey);
+
+static void __hmac_sha512_final(struct __hmac_sha512_ctx *ctx,
+				u8 *out, size_t digest_size)
+{
+	/* Generate the padded input for the outer hash in ctx->sha_ctx.buf. */
+	__sha512_final(&ctx->sha_ctx, ctx->sha_ctx.buf, digest_size);
+	memset(&ctx->sha_ctx.buf[digest_size], 0,
+	       SHA512_BLOCK_SIZE - digest_size);
+	ctx->sha_ctx.buf[digest_size] = 0x80;
+	*(__be32 *)&ctx->sha_ctx.buf[SHA512_BLOCK_SIZE - 4] =
+		cpu_to_be32(8 * (SHA512_BLOCK_SIZE + digest_size));
+
+	/* Compute the outer hash, which gives the HMAC value. */
+	sha512_blocks(&ctx->ostate, ctx->sha_ctx.buf, 1);
+	for (size_t i = 0; i < digest_size; i += 8)
+		put_unaligned_be64(ctx->ostate.h[i / 8], out + i);
+
+	memzero_explicit(ctx, sizeof(*ctx));
+}
+
+void hmac_sha384_final(struct hmac_sha384_ctx *ctx,
+		       u8 out[SHA384_DIGEST_SIZE])
+{
+	__hmac_sha512_final(&ctx->ctx, out, SHA384_DIGEST_SIZE);
+}
+EXPORT_SYMBOL_GPL(hmac_sha384_final);
+
+void hmac_sha512_final(struct hmac_sha512_ctx *ctx,
+		       u8 out[SHA512_DIGEST_SIZE])
+{
+	__hmac_sha512_final(&ctx->ctx, out, SHA512_DIGEST_SIZE);
+}
+EXPORT_SYMBOL_GPL(hmac_sha512_final);
+
+void hmac_sha384(const struct hmac_sha384_key *key,
+		 const u8 *data, size_t data_len, u8 out[SHA384_DIGEST_SIZE])
+{
+	struct hmac_sha384_ctx ctx;
+
+	hmac_sha384_init(&ctx, key);
+	hmac_sha384_update(&ctx, data, data_len);
+	hmac_sha384_final(&ctx, out);
+}
+EXPORT_SYMBOL_GPL(hmac_sha384);
+
+void hmac_sha512(const struct hmac_sha512_key *key,
+		 const u8 *data, size_t data_len, u8 out[SHA512_DIGEST_SIZE])
+{
+	struct hmac_sha512_ctx ctx;
+
+	hmac_sha512_init(&ctx, key);
+	hmac_sha512_update(&ctx, data, data_len);
+	hmac_sha512_final(&ctx, out);
+}
+EXPORT_SYMBOL_GPL(hmac_sha512);
+
+void hmac_sha384_usingrawkey(const u8 *raw_key, size_t raw_key_len,
+			     const u8 *data, size_t data_len,
+			     u8 out[SHA384_DIGEST_SIZE])
+{
+	struct hmac_sha384_ctx ctx;
+
+	hmac_sha384_init_usingrawkey(&ctx, raw_key, raw_key_len);
+	hmac_sha384_update(&ctx, data, data_len);
+	hmac_sha384_final(&ctx, out);
+}
+EXPORT_SYMBOL_GPL(hmac_sha384_usingrawkey);
+
+void hmac_sha512_usingrawkey(const u8 *raw_key, size_t raw_key_len,
+			     const u8 *data, size_t data_len,
+			     u8 out[SHA512_DIGEST_SIZE])
+{
+	struct hmac_sha512_ctx ctx;
+
+	hmac_sha512_init_usingrawkey(&ctx, raw_key, raw_key_len);
+	hmac_sha512_update(&ctx, data, data_len);
+	hmac_sha512_final(&ctx, out);
+}
+EXPORT_SYMBOL_GPL(hmac_sha512_usingrawkey);
+
+#if defined(sha512_mod_init_arch) || defined(CONFIG_CRYPTO_FIPS)
+static int __init sha512_mod_init(void)
+{
+#ifdef sha512_mod_init_arch
+	sha512_mod_init_arch();
+#endif
+	if (fips_enabled) {
+		/*
+		 * FIPS cryptographic algorithm self-test.  As per the FIPS
+		 * Implementation Guidance, testing HMAC-SHA512 satisfies the
+		 * test requirement for SHA-384, SHA-512, and HMAC-SHA384 too.
+		 */
+		u8 mac[SHA512_DIGEST_SIZE];
+
+		hmac_sha512_usingrawkey(fips_test_key, sizeof(fips_test_key),
+					fips_test_data, sizeof(fips_test_data),
+					mac);
+		if (memcmp(fips_test_hmac_sha512_value, mac, sizeof(mac)) != 0)
+			panic("sha512: FIPS self-test failed\n");
+	}
+	return 0;
+}
+subsys_initcall(sha512_mod_init);
+
+static void __exit sha512_mod_exit(void)
+{
+}
+module_exit(sha512_mod_exit);
+#endif
+
+MODULE_DESCRIPTION("SHA-384, SHA-512, HMAC-SHA384, and HMAC-SHA512 library functions");
+MODULE_LICENSE("GPL");