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, 464 insertions, 0 deletions

diff --git a/crypto/authencesn.c b/crypto/authencesn.c
new file mode 100644
index 000000000..ca063576f
--- /dev/null
+++ b/crypto/authencesn.c
@@ -0,0 +1,464 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * authencesn.c - AEAD wrapper for IPsec with extended sequence numbers,
+ *                 derived from authenc.c
+ *
+ * Copyright (C) 2010 secunet Security Networks AG
+ * Copyright (C) 2010 Steffen Klassert <steffen.klassert@secunet.com>
+ * Copyright (c) 2015 Herbert Xu <herbert@gondor.apana.org.au>
+ */
+
+#include <crypto/internal/aead.h>
+#include <crypto/internal/hash.h>
+#include <crypto/internal/skcipher.h>
+#include <crypto/authenc.h>
+#include <crypto/scatterwalk.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/rtnetlink.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+
+struct authenc_esn_instance_ctx {
+	struct crypto_ahash_spawn auth;
+	struct crypto_skcipher_spawn enc;
+};
+
+struct crypto_authenc_esn_ctx {
+	unsigned int reqoff;
+	struct crypto_ahash *auth;
+	struct crypto_skcipher *enc;
+};
+
+struct authenc_esn_request_ctx {
+	struct scatterlist src[2];
+	struct scatterlist dst[2];
+	char tail[];
+};
+
+static void authenc_esn_request_complete(struct aead_request *req, int err)
+{
+	if (err != -EINPROGRESS)
+		aead_request_complete(req, err);
+}
+
+static int crypto_authenc_esn_setauthsize(struct crypto_aead *authenc_esn,
+					  unsigned int authsize)
+{
+	if (authsize > 0 && authsize < 4)
+		return -EINVAL;
+
+	return 0;
+}
+
+static int crypto_authenc_esn_setkey(struct crypto_aead *authenc_esn, const u8 *key,
+				     unsigned int keylen)
+{
+	struct crypto_authenc_esn_ctx *ctx = crypto_aead_ctx(authenc_esn);
+	struct crypto_ahash *auth = ctx->auth;
+	struct crypto_skcipher *enc = ctx->enc;
+	struct crypto_authenc_keys keys;
+	int err = -EINVAL;
+
+	if (crypto_authenc_extractkeys(&keys, key, keylen) != 0)
+		goto out;
+
+	crypto_ahash_clear_flags(auth, CRYPTO_TFM_REQ_MASK);
+	crypto_ahash_set_flags(auth, crypto_aead_get_flags(authenc_esn) &
+				     CRYPTO_TFM_REQ_MASK);
+	err = crypto_ahash_setkey(auth, keys.authkey, keys.authkeylen);
+	if (err)
+		goto out;
+
+	crypto_skcipher_clear_flags(enc, CRYPTO_TFM_REQ_MASK);
+	crypto_skcipher_set_flags(enc, crypto_aead_get_flags(authenc_esn) &
+					 CRYPTO_TFM_REQ_MASK);
+	err = crypto_skcipher_setkey(enc, keys.enckey, keys.enckeylen);
+out:
+	memzero_explicit(&keys, sizeof(keys));
+	return err;
+}
+
+static int crypto_authenc_esn_genicv_tail(struct aead_request *req,
+					  unsigned int flags)
+{
+	struct crypto_aead *authenc_esn = crypto_aead_reqtfm(req);
+	struct authenc_esn_request_ctx *areq_ctx = aead_request_ctx(req);
+	u8 *hash = areq_ctx->tail;
+	unsigned int authsize = crypto_aead_authsize(authenc_esn);
+	unsigned int assoclen = req->assoclen;
+	unsigned int cryptlen = req->cryptlen;
+	struct scatterlist *dst = req->dst;
+	u32 tmp[2];
+
+	/* Move high-order bits of sequence number back. */
+	memcpy_from_sglist(tmp, dst, 4, 4);
+	memcpy_from_sglist(tmp + 1, dst, assoclen + cryptlen, 4);
+	memcpy_to_sglist(dst, 0, tmp, 8);
+
+	memcpy_to_sglist(dst, assoclen + cryptlen, hash, authsize);
+	return 0;
+}
+
+static void authenc_esn_geniv_ahash_done(void *data, int err)
+{
+	struct aead_request *req = data;
+
+	err = err ?: crypto_authenc_esn_genicv_tail(req, 0);
+	aead_request_complete(req, err);
+}
+
+static int crypto_authenc_esn_genicv(struct aead_request *req,
+				     unsigned int flags)
+{
+	struct crypto_aead *authenc_esn = crypto_aead_reqtfm(req);
+	struct authenc_esn_request_ctx *areq_ctx = aead_request_ctx(req);
+	struct crypto_authenc_esn_ctx *ctx = crypto_aead_ctx(authenc_esn);
+	struct crypto_ahash *auth = ctx->auth;
+	u8 *hash = areq_ctx->tail;
+	struct ahash_request *ahreq = (void *)(areq_ctx->tail + ctx->reqoff);
+	unsigned int authsize = crypto_aead_authsize(authenc_esn);
+	unsigned int assoclen = req->assoclen;
+	unsigned int cryptlen = req->cryptlen;
+	struct scatterlist *dst = req->dst;
+	u32 tmp[2];
+
+	if (!authsize)
+		return 0;
+
+	/* Move high-order bits of sequence number to the end. */
+	memcpy_from_sglist(tmp, dst, 0, 8);
+	memcpy_to_sglist(dst, 4, tmp, 4);
+	memcpy_to_sglist(dst, assoclen + cryptlen, tmp + 1, 4);
+
+	sg_init_table(areq_ctx->dst, 2);
+	dst = scatterwalk_ffwd(areq_ctx->dst, dst, 4);
+
+	ahash_request_set_tfm(ahreq, auth);
+	ahash_request_set_crypt(ahreq, dst, hash, assoclen + cryptlen);
+	ahash_request_set_callback(ahreq, flags,
+				   authenc_esn_geniv_ahash_done, req);
+
+	return crypto_ahash_digest(ahreq) ?:
+	       crypto_authenc_esn_genicv_tail(req, aead_request_flags(req));
+}
+
+
+static void crypto_authenc_esn_encrypt_done(void *data, int err)
+{
+	struct aead_request *areq = data;
+
+	if (!err)
+		err = crypto_authenc_esn_genicv(areq, 0);
+
+	authenc_esn_request_complete(areq, err);
+}
+
+static int crypto_authenc_esn_encrypt(struct aead_request *req)
+{
+	struct crypto_aead *authenc_esn = crypto_aead_reqtfm(req);
+	struct authenc_esn_request_ctx *areq_ctx = aead_request_ctx(req);
+	struct crypto_authenc_esn_ctx *ctx = crypto_aead_ctx(authenc_esn);
+	struct skcipher_request *skreq = (void *)(areq_ctx->tail +
+						  ctx->reqoff);
+	struct crypto_skcipher *enc = ctx->enc;
+	unsigned int assoclen = req->assoclen;
+	unsigned int cryptlen = req->cryptlen;
+	struct scatterlist *src, *dst;
+	int err;
+
+	if (assoclen < 8)
+		return -EINVAL;
+
+	sg_init_table(areq_ctx->src, 2);
+	src = scatterwalk_ffwd(areq_ctx->src, req->src, assoclen);
+	dst = src;
+
+	if (req->src != req->dst) {
+		memcpy_sglist(req->dst, req->src, assoclen);
+		sg_init_table(areq_ctx->dst, 2);
+		dst = scatterwalk_ffwd(areq_ctx->dst, req->dst, assoclen);
+	}
+
+	skcipher_request_set_tfm(skreq, enc);
+	skcipher_request_set_callback(skreq, aead_request_flags(req),
+				      crypto_authenc_esn_encrypt_done, req);
+	skcipher_request_set_crypt(skreq, src, dst, cryptlen, req->iv);
+
+	err = crypto_skcipher_encrypt(skreq);
+	if (err)
+		return err;
+
+	return crypto_authenc_esn_genicv(req, aead_request_flags(req));
+}
+
+static int crypto_authenc_esn_decrypt_tail(struct aead_request *req,
+					   unsigned int flags)
+{
+	struct crypto_aead *authenc_esn = crypto_aead_reqtfm(req);
+	unsigned int authsize = crypto_aead_authsize(authenc_esn);
+	struct authenc_esn_request_ctx *areq_ctx = aead_request_ctx(req);
+	struct crypto_authenc_esn_ctx *ctx = crypto_aead_ctx(authenc_esn);
+	struct skcipher_request *skreq = (void *)(areq_ctx->tail +
+						  ctx->reqoff);
+	struct crypto_ahash *auth = ctx->auth;
+	u8 *ohash = areq_ctx->tail;
+	unsigned int cryptlen = req->cryptlen - authsize;
+	unsigned int assoclen = req->assoclen;
+	struct scatterlist *src = req->src;
+	struct scatterlist *dst = req->dst;
+	u8 *ihash = ohash + crypto_ahash_digestsize(auth);
+	u32 tmp[2];
+
+	if (!authsize)
+		goto decrypt;
+
+	if (src == dst) {
+		/* Move high-order bits of sequence number back. */
+		memcpy_from_sglist(tmp, dst, 4, 4);
+		memcpy_from_sglist(tmp + 1, dst, assoclen + cryptlen, 4);
+		memcpy_to_sglist(dst, 0, tmp, 8);
+	} else
+		memcpy_sglist(dst, src, assoclen);
+
+	if (crypto_memneq(ihash, ohash, authsize))
+		return -EBADMSG;
+
+decrypt:
+
+	dst = scatterwalk_ffwd(areq_ctx->dst, dst, assoclen);
+	if (req->src == req->dst)
+		src = dst;
+	else
+		src = scatterwalk_ffwd(areq_ctx->src, src, assoclen);
+
+	skcipher_request_set_tfm(skreq, ctx->enc);
+	skcipher_request_set_callback(skreq, flags,
+				      req->base.complete, req->base.data);
+	skcipher_request_set_crypt(skreq, src, dst, cryptlen, req->iv);
+
+	return crypto_skcipher_decrypt(skreq);
+}
+
+static void authenc_esn_verify_ahash_done(void *data, int err)
+{
+	struct aead_request *req = data;
+
+	err = err ?: crypto_authenc_esn_decrypt_tail(req, 0);
+	authenc_esn_request_complete(req, err);
+}
+
+static int crypto_authenc_esn_decrypt(struct aead_request *req)
+{
+	struct crypto_aead *authenc_esn = crypto_aead_reqtfm(req);
+	struct authenc_esn_request_ctx *areq_ctx = aead_request_ctx(req);
+	struct crypto_authenc_esn_ctx *ctx = crypto_aead_ctx(authenc_esn);
+	struct ahash_request *ahreq = (void *)(areq_ctx->tail + ctx->reqoff);
+	unsigned int authsize = crypto_aead_authsize(authenc_esn);
+	struct crypto_ahash *auth = ctx->auth;
+	u8 *ohash = areq_ctx->tail;
+	unsigned int assoclen = req->assoclen;
+	unsigned int cryptlen = req->cryptlen;
+	u8 *ihash = ohash + crypto_ahash_digestsize(auth);
+	struct scatterlist *src = req->src;
+	struct scatterlist *dst = req->dst;
+	u32 tmp[2];
+	int err;
+
+	if (assoclen < 8)
+		return -EINVAL;
+
+	if (!authsize)
+		goto tail;
+
+	cryptlen -= authsize;
+	memcpy_from_sglist(ihash, req->src, assoclen + cryptlen, authsize);
+
+	/* Move high-order bits of sequence number to the end. */
+	memcpy_from_sglist(tmp, src, 0, 8);
+	if (src == dst) {
+		memcpy_to_sglist(dst, 4, tmp, 4);
+		memcpy_to_sglist(dst, assoclen + cryptlen, tmp + 1, 4);
+		dst = scatterwalk_ffwd(areq_ctx->dst, dst, 4);
+	} else {
+		memcpy_to_sglist(dst, 0, tmp, 4);
+		memcpy_to_sglist(dst, assoclen + cryptlen - 4, tmp + 1, 4);
+
+		src = scatterwalk_ffwd(areq_ctx->src, src, 8);
+		dst = scatterwalk_ffwd(areq_ctx->dst, dst, 4);
+		memcpy_sglist(dst, src, assoclen + cryptlen - 8);
+		dst = req->dst;
+	}
+
+	ahash_request_set_tfm(ahreq, auth);
+	ahash_request_set_crypt(ahreq, dst, ohash, assoclen + cryptlen);
+	ahash_request_set_callback(ahreq, aead_request_flags(req),
+				   authenc_esn_verify_ahash_done, req);
+
+	err = crypto_ahash_digest(ahreq);
+	if (err)
+		return err;
+
+tail:
+	return crypto_authenc_esn_decrypt_tail(req, aead_request_flags(req));
+}
+
+static int crypto_authenc_esn_init_tfm(struct crypto_aead *tfm)
+{
+	struct aead_instance *inst = aead_alg_instance(tfm);
+	struct authenc_esn_instance_ctx *ictx = aead_instance_ctx(inst);
+	struct crypto_authenc_esn_ctx *ctx = crypto_aead_ctx(tfm);
+	struct crypto_ahash *auth;
+	struct crypto_skcipher *enc;
+	int err;
+
+	auth = crypto_spawn_ahash(&ictx->auth);
+	if (IS_ERR(auth))
+		return PTR_ERR(auth);
+
+	enc = crypto_spawn_skcipher(&ictx->enc);
+	err = PTR_ERR(enc);
+	if (IS_ERR(enc))
+		goto err_free_ahash;
+
+	ctx->auth = auth;
+	ctx->enc = enc;
+
+	ctx->reqoff = 2 * crypto_ahash_digestsize(auth);
+
+	crypto_aead_set_reqsize(
+		tfm,
+		sizeof(struct authenc_esn_request_ctx) +
+		ctx->reqoff +
+		max_t(unsigned int,
+		      crypto_ahash_reqsize(auth) +
+		      sizeof(struct ahash_request),
+		      sizeof(struct skcipher_request) +
+		      crypto_skcipher_reqsize(enc)));
+
+	return 0;
+
+err_free_ahash:
+	crypto_free_ahash(auth);
+	return err;
+}
+
+static void crypto_authenc_esn_exit_tfm(struct crypto_aead *tfm)
+{
+	struct crypto_authenc_esn_ctx *ctx = crypto_aead_ctx(tfm);
+
+	crypto_free_ahash(ctx->auth);
+	crypto_free_skcipher(ctx->enc);
+}
+
+static void crypto_authenc_esn_free(struct aead_instance *inst)
+{
+	struct authenc_esn_instance_ctx *ctx = aead_instance_ctx(inst);
+
+	crypto_drop_skcipher(&ctx->enc);
+	crypto_drop_ahash(&ctx->auth);
+	kfree(inst);
+}
+
+static int crypto_authenc_esn_create(struct crypto_template *tmpl,
+				     struct rtattr **tb)
+{
+	u32 mask;
+	struct aead_instance *inst;
+	struct authenc_esn_instance_ctx *ctx;
+	struct skcipher_alg_common *enc;
+	struct hash_alg_common *auth;
+	struct crypto_alg *auth_base;
+	int err;
+
+	err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_AEAD, &mask);
+	if (err)
+		return err;
+
+	inst = kzalloc(sizeof(*inst) + sizeof(*ctx), GFP_KERNEL);
+	if (!inst)
+		return -ENOMEM;
+	ctx = aead_instance_ctx(inst);
+
+	err = crypto_grab_ahash(&ctx->auth, aead_crypto_instance(inst),
+				crypto_attr_alg_name(tb[1]), 0, mask);
+	if (err)
+		goto err_free_inst;
+	auth = crypto_spawn_ahash_alg(&ctx->auth);
+	auth_base = &auth->base;
+
+	if (auth->digestsize > 0 && auth->digestsize < 4) {
+		err = -EINVAL;
+		goto err_free_inst;
+	}
+
+	err = crypto_grab_skcipher(&ctx->enc, aead_crypto_instance(inst),
+				   crypto_attr_alg_name(tb[2]), 0, mask);
+	if (err)
+		goto err_free_inst;
+	enc = crypto_spawn_skcipher_alg_common(&ctx->enc);
+
+	err = -ENAMETOOLONG;
+	if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
+		     "authencesn(%s,%s)", auth_base->cra_name,
+		     enc->base.cra_name) >= CRYPTO_MAX_ALG_NAME)
+		goto err_free_inst;
+
+	if (snprintf(inst->alg.base.cra_driver_name, CRYPTO_MAX_ALG_NAME,
+		     "authencesn(%s,%s)", auth_base->cra_driver_name,
+		     enc->base.cra_driver_name) >= CRYPTO_MAX_ALG_NAME)
+		goto err_free_inst;
+
+	inst->alg.base.cra_priority = enc->base.cra_priority * 10 +
+				      auth_base->cra_priority;
+	inst->alg.base.cra_blocksize = enc->base.cra_blocksize;
+	inst->alg.base.cra_alignmask = enc->base.cra_alignmask;
+	inst->alg.base.cra_ctxsize = sizeof(struct crypto_authenc_esn_ctx);
+
+	inst->alg.ivsize = enc->ivsize;
+	inst->alg.chunksize = enc->chunksize;
+	inst->alg.maxauthsize = auth->digestsize;
+
+	inst->alg.init = crypto_authenc_esn_init_tfm;
+	inst->alg.exit = crypto_authenc_esn_exit_tfm;
+
+	inst->alg.setkey = crypto_authenc_esn_setkey;
+	inst->alg.setauthsize = crypto_authenc_esn_setauthsize;
+	inst->alg.encrypt = crypto_authenc_esn_encrypt;
+	inst->alg.decrypt = crypto_authenc_esn_decrypt;
+
+	inst->free = crypto_authenc_esn_free;
+
+	err = aead_register_instance(tmpl, inst);
+	if (err) {
+err_free_inst:
+		crypto_authenc_esn_free(inst);
+	}
+	return err;
+}
+
+static struct crypto_template crypto_authenc_esn_tmpl = {
+	.name = "authencesn",
+	.create = crypto_authenc_esn_create,
+	.module = THIS_MODULE,
+};
+
+static int __init crypto_authenc_esn_module_init(void)
+{
+	return crypto_register_template(&crypto_authenc_esn_tmpl);
+}
+
+static void __exit crypto_authenc_esn_module_exit(void)
+{
+	crypto_unregister_template(&crypto_authenc_esn_tmpl);
+}
+
+module_init(crypto_authenc_esn_module_init);
+module_exit(crypto_authenc_esn_module_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Steffen Klassert <steffen.klassert@secunet.com>");
+MODULE_DESCRIPTION("AEAD wrapper for IPsec with extended sequence numbers");
+MODULE_ALIAS_CRYPTO("authencesn");