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, 351 insertions, 0 deletions

diff --git a/crypto/rmd160.c b/crypto/rmd160.c
new file mode 100644
index 000000000..9860b60c9
--- /dev/null
+++ b/crypto/rmd160.c
@@ -0,0 +1,351 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Cryptographic API.
+ *
+ * RIPEMD-160 - RACE Integrity Primitives Evaluation Message Digest.
+ *
+ * Based on the reference implementation by Antoon Bosselaers, ESAT-COSIC
+ *
+ * Copyright (c) 2008 Adrian-Ken Rueegsegger <ken@codelabs.ch>
+ */
+#include <crypto/internal/hash.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/string.h>
+#include "ripemd.h"
+
+struct rmd160_ctx {
+	u64 byte_count;
+	u32 state[5];
+};
+
+#define K1  RMD_K1
+#define K2  RMD_K2
+#define K3  RMD_K3
+#define K4  RMD_K4
+#define K5  RMD_K5
+#define KK1 RMD_K6
+#define KK2 RMD_K7
+#define KK3 RMD_K8
+#define KK4 RMD_K9
+#define KK5 RMD_K1
+
+#define F1(x, y, z) (x ^ y ^ z)		/* XOR */
+#define F2(x, y, z) (z ^ (x & (y ^ z)))	/* x ? y : z */
+#define F3(x, y, z) ((x | ~y) ^ z)
+#define F4(x, y, z) (y ^ (z & (x ^ y)))	/* z ? x : y */
+#define F5(x, y, z) (x ^ (y | ~z))
+
+#define ROUND(a, b, c, d, e, f, k, x, s)  { \
+	(a) += f((b), (c), (d)) + le32_to_cpup(&(x)) + (k); \
+	(a) = rol32((a), (s)) + (e); \
+	(c) = rol32((c), 10); \
+}
+
+static void rmd160_transform(u32 *state, const __le32 *in)
+{
+	u32 aa, bb, cc, dd, ee, aaa, bbb, ccc, ddd, eee;
+
+	/* Initialize left lane */
+	aa = state[0];
+	bb = state[1];
+	cc = state[2];
+	dd = state[3];
+	ee = state[4];
+
+	/* Initialize right lane */
+	aaa = state[0];
+	bbb = state[1];
+	ccc = state[2];
+	ddd = state[3];
+	eee = state[4];
+
+	/* round 1: left lane */
+	ROUND(aa, bb, cc, dd, ee, F1, K1, in[0],  11);
+	ROUND(ee, aa, bb, cc, dd, F1, K1, in[1],  14);
+	ROUND(dd, ee, aa, bb, cc, F1, K1, in[2],  15);
+	ROUND(cc, dd, ee, aa, bb, F1, K1, in[3],  12);
+	ROUND(bb, cc, dd, ee, aa, F1, K1, in[4],   5);
+	ROUND(aa, bb, cc, dd, ee, F1, K1, in[5],   8);
+	ROUND(ee, aa, bb, cc, dd, F1, K1, in[6],   7);
+	ROUND(dd, ee, aa, bb, cc, F1, K1, in[7],   9);
+	ROUND(cc, dd, ee, aa, bb, F1, K1, in[8],  11);
+	ROUND(bb, cc, dd, ee, aa, F1, K1, in[9],  13);
+	ROUND(aa, bb, cc, dd, ee, F1, K1, in[10], 14);
+	ROUND(ee, aa, bb, cc, dd, F1, K1, in[11], 15);
+	ROUND(dd, ee, aa, bb, cc, F1, K1, in[12],  6);
+	ROUND(cc, dd, ee, aa, bb, F1, K1, in[13],  7);
+	ROUND(bb, cc, dd, ee, aa, F1, K1, in[14],  9);
+	ROUND(aa, bb, cc, dd, ee, F1, K1, in[15],  8);
+
+	/* round 2: left lane" */
+	ROUND(ee, aa, bb, cc, dd, F2, K2, in[7],   7);
+	ROUND(dd, ee, aa, bb, cc, F2, K2, in[4],   6);
+	ROUND(cc, dd, ee, aa, bb, F2, K2, in[13],  8);
+	ROUND(bb, cc, dd, ee, aa, F2, K2, in[1],  13);
+	ROUND(aa, bb, cc, dd, ee, F2, K2, in[10], 11);
+	ROUND(ee, aa, bb, cc, dd, F2, K2, in[6],   9);
+	ROUND(dd, ee, aa, bb, cc, F2, K2, in[15],  7);
+	ROUND(cc, dd, ee, aa, bb, F2, K2, in[3],  15);
+	ROUND(bb, cc, dd, ee, aa, F2, K2, in[12],  7);
+	ROUND(aa, bb, cc, dd, ee, F2, K2, in[0],  12);
+	ROUND(ee, aa, bb, cc, dd, F2, K2, in[9],  15);
+	ROUND(dd, ee, aa, bb, cc, F2, K2, in[5],   9);
+	ROUND(cc, dd, ee, aa, bb, F2, K2, in[2],  11);
+	ROUND(bb, cc, dd, ee, aa, F2, K2, in[14],  7);
+	ROUND(aa, bb, cc, dd, ee, F2, K2, in[11], 13);
+	ROUND(ee, aa, bb, cc, dd, F2, K2, in[8],  12);
+
+	/* round 3: left lane" */
+	ROUND(dd, ee, aa, bb, cc, F3, K3, in[3],  11);
+	ROUND(cc, dd, ee, aa, bb, F3, K3, in[10], 13);
+	ROUND(bb, cc, dd, ee, aa, F3, K3, in[14],  6);
+	ROUND(aa, bb, cc, dd, ee, F3, K3, in[4],   7);
+	ROUND(ee, aa, bb, cc, dd, F3, K3, in[9],  14);
+	ROUND(dd, ee, aa, bb, cc, F3, K3, in[15],  9);
+	ROUND(cc, dd, ee, aa, bb, F3, K3, in[8],  13);
+	ROUND(bb, cc, dd, ee, aa, F3, K3, in[1],  15);
+	ROUND(aa, bb, cc, dd, ee, F3, K3, in[2],  14);
+	ROUND(ee, aa, bb, cc, dd, F3, K3, in[7],   8);
+	ROUND(dd, ee, aa, bb, cc, F3, K3, in[0],  13);
+	ROUND(cc, dd, ee, aa, bb, F3, K3, in[6],   6);
+	ROUND(bb, cc, dd, ee, aa, F3, K3, in[13],  5);
+	ROUND(aa, bb, cc, dd, ee, F3, K3, in[11], 12);
+	ROUND(ee, aa, bb, cc, dd, F3, K3, in[5],   7);
+	ROUND(dd, ee, aa, bb, cc, F3, K3, in[12],  5);
+
+	/* round 4: left lane" */
+	ROUND(cc, dd, ee, aa, bb, F4, K4, in[1],  11);
+	ROUND(bb, cc, dd, ee, aa, F4, K4, in[9],  12);
+	ROUND(aa, bb, cc, dd, ee, F4, K4, in[11], 14);
+	ROUND(ee, aa, bb, cc, dd, F4, K4, in[10], 15);
+	ROUND(dd, ee, aa, bb, cc, F4, K4, in[0],  14);
+	ROUND(cc, dd, ee, aa, bb, F4, K4, in[8],  15);
+	ROUND(bb, cc, dd, ee, aa, F4, K4, in[12],  9);
+	ROUND(aa, bb, cc, dd, ee, F4, K4, in[4],   8);
+	ROUND(ee, aa, bb, cc, dd, F4, K4, in[13],  9);
+	ROUND(dd, ee, aa, bb, cc, F4, K4, in[3],  14);
+	ROUND(cc, dd, ee, aa, bb, F4, K4, in[7],   5);
+	ROUND(bb, cc, dd, ee, aa, F4, K4, in[15],  6);
+	ROUND(aa, bb, cc, dd, ee, F4, K4, in[14],  8);
+	ROUND(ee, aa, bb, cc, dd, F4, K4, in[5],   6);
+	ROUND(dd, ee, aa, bb, cc, F4, K4, in[6],   5);
+	ROUND(cc, dd, ee, aa, bb, F4, K4, in[2],  12);
+
+	/* round 5: left lane" */
+	ROUND(bb, cc, dd, ee, aa, F5, K5, in[4],   9);
+	ROUND(aa, bb, cc, dd, ee, F5, K5, in[0],  15);
+	ROUND(ee, aa, bb, cc, dd, F5, K5, in[5],   5);
+	ROUND(dd, ee, aa, bb, cc, F5, K5, in[9],  11);
+	ROUND(cc, dd, ee, aa, bb, F5, K5, in[7],   6);
+	ROUND(bb, cc, dd, ee, aa, F5, K5, in[12],  8);
+	ROUND(aa, bb, cc, dd, ee, F5, K5, in[2],  13);
+	ROUND(ee, aa, bb, cc, dd, F5, K5, in[10], 12);
+	ROUND(dd, ee, aa, bb, cc, F5, K5, in[14],  5);
+	ROUND(cc, dd, ee, aa, bb, F5, K5, in[1],  12);
+	ROUND(bb, cc, dd, ee, aa, F5, K5, in[3],  13);
+	ROUND(aa, bb, cc, dd, ee, F5, K5, in[8],  14);
+	ROUND(ee, aa, bb, cc, dd, F5, K5, in[11], 11);
+	ROUND(dd, ee, aa, bb, cc, F5, K5, in[6],   8);
+	ROUND(cc, dd, ee, aa, bb, F5, K5, in[15],  5);
+	ROUND(bb, cc, dd, ee, aa, F5, K5, in[13],  6);
+
+	/* round 1: right lane */
+	ROUND(aaa, bbb, ccc, ddd, eee, F5, KK1, in[5],   8);
+	ROUND(eee, aaa, bbb, ccc, ddd, F5, KK1, in[14],  9);
+	ROUND(ddd, eee, aaa, bbb, ccc, F5, KK1, in[7],   9);
+	ROUND(ccc, ddd, eee, aaa, bbb, F5, KK1, in[0],  11);
+	ROUND(bbb, ccc, ddd, eee, aaa, F5, KK1, in[9],  13);
+	ROUND(aaa, bbb, ccc, ddd, eee, F5, KK1, in[2],  15);
+	ROUND(eee, aaa, bbb, ccc, ddd, F5, KK1, in[11], 15);
+	ROUND(ddd, eee, aaa, bbb, ccc, F5, KK1, in[4],   5);
+	ROUND(ccc, ddd, eee, aaa, bbb, F5, KK1, in[13],  7);
+	ROUND(bbb, ccc, ddd, eee, aaa, F5, KK1, in[6],   7);
+	ROUND(aaa, bbb, ccc, ddd, eee, F5, KK1, in[15],  8);
+	ROUND(eee, aaa, bbb, ccc, ddd, F5, KK1, in[8],  11);
+	ROUND(ddd, eee, aaa, bbb, ccc, F5, KK1, in[1],  14);
+	ROUND(ccc, ddd, eee, aaa, bbb, F5, KK1, in[10], 14);
+	ROUND(bbb, ccc, ddd, eee, aaa, F5, KK1, in[3],  12);
+	ROUND(aaa, bbb, ccc, ddd, eee, F5, KK1, in[12],  6);
+
+	/* round 2: right lane */
+	ROUND(eee, aaa, bbb, ccc, ddd, F4, KK2, in[6],   9);
+	ROUND(ddd, eee, aaa, bbb, ccc, F4, KK2, in[11], 13);
+	ROUND(ccc, ddd, eee, aaa, bbb, F4, KK2, in[3],  15);
+	ROUND(bbb, ccc, ddd, eee, aaa, F4, KK2, in[7],   7);
+	ROUND(aaa, bbb, ccc, ddd, eee, F4, KK2, in[0],  12);
+	ROUND(eee, aaa, bbb, ccc, ddd, F4, KK2, in[13],  8);
+	ROUND(ddd, eee, aaa, bbb, ccc, F4, KK2, in[5],   9);
+	ROUND(ccc, ddd, eee, aaa, bbb, F4, KK2, in[10], 11);
+	ROUND(bbb, ccc, ddd, eee, aaa, F4, KK2, in[14],  7);
+	ROUND(aaa, bbb, ccc, ddd, eee, F4, KK2, in[15],  7);
+	ROUND(eee, aaa, bbb, ccc, ddd, F4, KK2, in[8],  12);
+	ROUND(ddd, eee, aaa, bbb, ccc, F4, KK2, in[12],  7);
+	ROUND(ccc, ddd, eee, aaa, bbb, F4, KK2, in[4],   6);
+	ROUND(bbb, ccc, ddd, eee, aaa, F4, KK2, in[9],  15);
+	ROUND(aaa, bbb, ccc, ddd, eee, F4, KK2, in[1],  13);
+	ROUND(eee, aaa, bbb, ccc, ddd, F4, KK2, in[2],  11);
+
+	/* round 3: right lane */
+	ROUND(ddd, eee, aaa, bbb, ccc, F3, KK3, in[15],  9);
+	ROUND(ccc, ddd, eee, aaa, bbb, F3, KK3, in[5],   7);
+	ROUND(bbb, ccc, ddd, eee, aaa, F3, KK3, in[1],  15);
+	ROUND(aaa, bbb, ccc, ddd, eee, F3, KK3, in[3],  11);
+	ROUND(eee, aaa, bbb, ccc, ddd, F3, KK3, in[7],   8);
+	ROUND(ddd, eee, aaa, bbb, ccc, F3, KK3, in[14],  6);
+	ROUND(ccc, ddd, eee, aaa, bbb, F3, KK3, in[6],   6);
+	ROUND(bbb, ccc, ddd, eee, aaa, F3, KK3, in[9],  14);
+	ROUND(aaa, bbb, ccc, ddd, eee, F3, KK3, in[11], 12);
+	ROUND(eee, aaa, bbb, ccc, ddd, F3, KK3, in[8],  13);
+	ROUND(ddd, eee, aaa, bbb, ccc, F3, KK3, in[12],  5);
+	ROUND(ccc, ddd, eee, aaa, bbb, F3, KK3, in[2],  14);
+	ROUND(bbb, ccc, ddd, eee, aaa, F3, KK3, in[10], 13);
+	ROUND(aaa, bbb, ccc, ddd, eee, F3, KK3, in[0],  13);
+	ROUND(eee, aaa, bbb, ccc, ddd, F3, KK3, in[4],   7);
+	ROUND(ddd, eee, aaa, bbb, ccc, F3, KK3, in[13],  5);
+
+	/* round 4: right lane */
+	ROUND(ccc, ddd, eee, aaa, bbb, F2, KK4, in[8],  15);
+	ROUND(bbb, ccc, ddd, eee, aaa, F2, KK4, in[6],   5);
+	ROUND(aaa, bbb, ccc, ddd, eee, F2, KK4, in[4],   8);
+	ROUND(eee, aaa, bbb, ccc, ddd, F2, KK4, in[1],  11);
+	ROUND(ddd, eee, aaa, bbb, ccc, F2, KK4, in[3],  14);
+	ROUND(ccc, ddd, eee, aaa, bbb, F2, KK4, in[11], 14);
+	ROUND(bbb, ccc, ddd, eee, aaa, F2, KK4, in[15],  6);
+	ROUND(aaa, bbb, ccc, ddd, eee, F2, KK4, in[0],  14);
+	ROUND(eee, aaa, bbb, ccc, ddd, F2, KK4, in[5],   6);
+	ROUND(ddd, eee, aaa, bbb, ccc, F2, KK4, in[12],  9);
+	ROUND(ccc, ddd, eee, aaa, bbb, F2, KK4, in[2],  12);
+	ROUND(bbb, ccc, ddd, eee, aaa, F2, KK4, in[13],  9);
+	ROUND(aaa, bbb, ccc, ddd, eee, F2, KK4, in[9],  12);
+	ROUND(eee, aaa, bbb, ccc, ddd, F2, KK4, in[7],   5);
+	ROUND(ddd, eee, aaa, bbb, ccc, F2, KK4, in[10], 15);
+	ROUND(ccc, ddd, eee, aaa, bbb, F2, KK4, in[14],  8);
+
+	/* round 5: right lane */
+	ROUND(bbb, ccc, ddd, eee, aaa, F1, KK5, in[12],  8);
+	ROUND(aaa, bbb, ccc, ddd, eee, F1, KK5, in[15],  5);
+	ROUND(eee, aaa, bbb, ccc, ddd, F1, KK5, in[10], 12);
+	ROUND(ddd, eee, aaa, bbb, ccc, F1, KK5, in[4],   9);
+	ROUND(ccc, ddd, eee, aaa, bbb, F1, KK5, in[1],  12);
+	ROUND(bbb, ccc, ddd, eee, aaa, F1, KK5, in[5],   5);
+	ROUND(aaa, bbb, ccc, ddd, eee, F1, KK5, in[8],  14);
+	ROUND(eee, aaa, bbb, ccc, ddd, F1, KK5, in[7],   6);
+	ROUND(ddd, eee, aaa, bbb, ccc, F1, KK5, in[6],   8);
+	ROUND(ccc, ddd, eee, aaa, bbb, F1, KK5, in[2],  13);
+	ROUND(bbb, ccc, ddd, eee, aaa, F1, KK5, in[13],  6);
+	ROUND(aaa, bbb, ccc, ddd, eee, F1, KK5, in[14],  5);
+	ROUND(eee, aaa, bbb, ccc, ddd, F1, KK5, in[0],  15);
+	ROUND(ddd, eee, aaa, bbb, ccc, F1, KK5, in[3],  13);
+	ROUND(ccc, ddd, eee, aaa, bbb, F1, KK5, in[9],  11);
+	ROUND(bbb, ccc, ddd, eee, aaa, F1, KK5, in[11], 11);
+
+	/* combine results */
+	ddd += cc + state[1];		/* final result for state[0] */
+	state[1] = state[2] + dd + eee;
+	state[2] = state[3] + ee + aaa;
+	state[3] = state[4] + aa + bbb;
+	state[4] = state[0] + bb + ccc;
+	state[0] = ddd;
+}
+
+static int rmd160_init(struct shash_desc *desc)
+{
+	struct rmd160_ctx *rctx = shash_desc_ctx(desc);
+
+	rctx->byte_count = 0;
+
+	rctx->state[0] = RMD_H0;
+	rctx->state[1] = RMD_H1;
+	rctx->state[2] = RMD_H2;
+	rctx->state[3] = RMD_H3;
+	rctx->state[4] = RMD_H4;
+
+	return 0;
+}
+
+static int rmd160_update(struct shash_desc *desc, const u8 *data,
+			 unsigned int len)
+{
+	int remain = len - round_down(len, RMD160_BLOCK_SIZE);
+	struct rmd160_ctx *rctx = shash_desc_ctx(desc);
+	__le32 buffer[RMD160_BLOCK_SIZE / 4];
+
+	rctx->byte_count += len - remain;
+
+	do {
+		memcpy(buffer, data, sizeof(buffer));
+		rmd160_transform(rctx->state, buffer);
+		data += sizeof(buffer);
+		len -= sizeof(buffer);
+	} while (len >= sizeof(buffer));
+
+	memzero_explicit(buffer, sizeof(buffer));
+	return remain;
+}
+
+/* Add padding and return the message digest. */
+static int rmd160_finup(struct shash_desc *desc, const u8 *src,
+			unsigned int len, u8 *out)
+{
+	unsigned int bit_offset = RMD160_BLOCK_SIZE / 8 - 1;
+	struct rmd160_ctx *rctx = shash_desc_ctx(desc);
+	union {
+		__le64 l64[RMD160_BLOCK_SIZE / 4];
+		__le32 l32[RMD160_BLOCK_SIZE / 2];
+		u8 u8[RMD160_BLOCK_SIZE * 2];
+	} block = {};
+	__le32 *dst = (__le32 *)out;
+	u32 i;
+
+	rctx->byte_count += len;
+	if (len >= bit_offset * 8)
+		bit_offset += RMD160_BLOCK_SIZE / 8;
+	memcpy(&block, src, len);
+	block.u8[len] = 0x80;
+	block.l64[bit_offset] = cpu_to_le64(rctx->byte_count << 3);
+
+	rmd160_transform(rctx->state, block.l32);
+	if (bit_offset > RMD160_BLOCK_SIZE / 8)
+		rmd160_transform(rctx->state,
+				 block.l32 + RMD160_BLOCK_SIZE / 4);
+	memzero_explicit(&block, sizeof(block));
+
+	/* Store state in digest */
+	for (i = 0; i < 5; i++)
+		dst[i] = cpu_to_le32p(&rctx->state[i]);
+	return 0;
+}
+
+static struct shash_alg alg = {
+	.digestsize	=	RMD160_DIGEST_SIZE,
+	.init		=	rmd160_init,
+	.update		=	rmd160_update,
+	.finup		=	rmd160_finup,
+	.descsize	=	sizeof(struct rmd160_ctx),
+	.base		=	{
+		.cra_name	 =	"rmd160",
+		.cra_driver_name =	"rmd160-generic",
+		.cra_flags	 =	CRYPTO_AHASH_ALG_BLOCK_ONLY,
+		.cra_blocksize	 =	RMD160_BLOCK_SIZE,
+		.cra_module	 =	THIS_MODULE,
+	}
+};
+
+static int __init rmd160_mod_init(void)
+{
+	return crypto_register_shash(&alg);
+}
+
+static void __exit rmd160_mod_fini(void)
+{
+	crypto_unregister_shash(&alg);
+}
+
+module_init(rmd160_mod_init);
+module_exit(rmd160_mod_fini);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Adrian-Ken Rueegsegger <ken@codelabs.ch>");
+MODULE_DESCRIPTION("RIPEMD-160 Message Digest");
+MODULE_ALIAS_CRYPTO("rmd160");