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, 454 insertions, 0 deletions

diff --git a/crypto/authenc.c b/crypto/authenc.c
new file mode 100644
index 000000000..ac679ce2c
--- /dev/null
+++ b/crypto/authenc.c
@@ -0,0 +1,454 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Authenc: Simple AEAD wrapper for IPsec
+ *
+ * Copyright (c) 2007-2015 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_instance_ctx {
+	struct crypto_ahash_spawn auth;
+	struct crypto_skcipher_spawn enc;
+	unsigned int reqoff;
+};
+
+struct crypto_authenc_ctx {
+	struct crypto_ahash *auth;
+	struct crypto_skcipher *enc;
+};
+
+struct authenc_request_ctx {
+	struct scatterlist src[2];
+	struct scatterlist dst[2];
+	char tail[];
+};
+
+static void authenc_request_complete(struct aead_request *req, int err)
+{
+	if (err != -EINPROGRESS && err != -EBUSY)
+		aead_request_complete(req, err);
+}
+
+int crypto_authenc_extractkeys(struct crypto_authenc_keys *keys, const u8 *key,
+			       unsigned int keylen)
+{
+	struct rtattr *rta = (struct rtattr *)key;
+	struct crypto_authenc_key_param *param;
+
+	if (!RTA_OK(rta, keylen))
+		return -EINVAL;
+	if (rta->rta_type != CRYPTO_AUTHENC_KEYA_PARAM)
+		return -EINVAL;
+
+	/*
+	 * RTA_OK() didn't align the rtattr's payload when validating that it
+	 * fits in the buffer.  Yet, the keys should start on the next 4-byte
+	 * aligned boundary.  To avoid confusion, require that the rtattr
+	 * payload be exactly the param struct, which has a 4-byte aligned size.
+	 */
+	if (RTA_PAYLOAD(rta) != sizeof(*param))
+		return -EINVAL;
+	BUILD_BUG_ON(sizeof(*param) % RTA_ALIGNTO);
+
+	param = RTA_DATA(rta);
+	keys->enckeylen = be32_to_cpu(param->enckeylen);
+
+	key += rta->rta_len;
+	keylen -= rta->rta_len;
+
+	if (keylen < keys->enckeylen)
+		return -EINVAL;
+
+	keys->authkeylen = keylen - keys->enckeylen;
+	keys->authkey = key;
+	keys->enckey = key + keys->authkeylen;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(crypto_authenc_extractkeys);
+
+static int crypto_authenc_setkey(struct crypto_aead *authenc, const u8 *key,
+				 unsigned int keylen)
+{
+	struct crypto_authenc_ctx *ctx = crypto_aead_ctx(authenc);
+	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) &
+				    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) &
+				       CRYPTO_TFM_REQ_MASK);
+	err = crypto_skcipher_setkey(enc, keys.enckey, keys.enckeylen);
+out:
+	memzero_explicit(&keys, sizeof(keys));
+	return err;
+}
+
+static void authenc_geniv_ahash_finish(struct aead_request *req)
+{
+	struct crypto_aead *authenc = crypto_aead_reqtfm(req);
+	struct aead_instance *inst = aead_alg_instance(authenc);
+	struct authenc_instance_ctx *ictx = aead_instance_ctx(inst);
+	struct authenc_request_ctx *areq_ctx = aead_request_ctx(req);
+	struct ahash_request *ahreq = (void *)(areq_ctx->tail + ictx->reqoff);
+
+	scatterwalk_map_and_copy(ahreq->result, req->dst,
+				 req->assoclen + req->cryptlen,
+				 crypto_aead_authsize(authenc), 1);
+}
+
+static void authenc_geniv_ahash_done(void *data, int err)
+{
+	struct aead_request *req = data;
+
+	if (!err)
+		authenc_geniv_ahash_finish(req);
+	aead_request_complete(req, err);
+}
+
+/*
+ * Used when the ahash request was invoked in the async callback context
+ * of the previous skcipher request.  Eat any EINPROGRESS notifications.
+ */
+static void authenc_geniv_ahash_done2(void *data, int err)
+{
+	struct aead_request *req = data;
+
+	if (!err)
+		authenc_geniv_ahash_finish(req);
+	authenc_request_complete(req, err);
+}
+
+static int crypto_authenc_genicv(struct aead_request *req, unsigned int mask)
+{
+	struct crypto_aead *authenc = crypto_aead_reqtfm(req);
+	struct aead_instance *inst = aead_alg_instance(authenc);
+	struct crypto_authenc_ctx *ctx = crypto_aead_ctx(authenc);
+	struct authenc_instance_ctx *ictx = aead_instance_ctx(inst);
+	struct crypto_ahash *auth = ctx->auth;
+	struct authenc_request_ctx *areq_ctx = aead_request_ctx(req);
+	struct ahash_request *ahreq = (void *)(areq_ctx->tail + ictx->reqoff);
+	unsigned int flags = aead_request_flags(req) & ~mask;
+	u8 *hash = areq_ctx->tail;
+	int err;
+
+	ahash_request_set_tfm(ahreq, auth);
+	ahash_request_set_crypt(ahreq, req->dst, hash,
+				req->assoclen + req->cryptlen);
+	ahash_request_set_callback(ahreq, flags,
+				   mask ? authenc_geniv_ahash_done2 :
+					  authenc_geniv_ahash_done, req);
+
+	err = crypto_ahash_digest(ahreq);
+	if (err)
+		return err;
+
+	scatterwalk_map_and_copy(hash, req->dst, req->assoclen + req->cryptlen,
+				 crypto_aead_authsize(authenc), 1);
+
+	return 0;
+}
+
+static void crypto_authenc_encrypt_done(void *data, int err)
+{
+	struct aead_request *areq = data;
+
+	if (err) {
+		aead_request_complete(areq, err);
+		return;
+	}
+	err = crypto_authenc_genicv(areq, CRYPTO_TFM_REQ_MAY_SLEEP);
+	authenc_request_complete(areq, err);
+}
+
+static int crypto_authenc_encrypt(struct aead_request *req)
+{
+	struct crypto_aead *authenc = crypto_aead_reqtfm(req);
+	struct aead_instance *inst = aead_alg_instance(authenc);
+	struct crypto_authenc_ctx *ctx = crypto_aead_ctx(authenc);
+	struct authenc_instance_ctx *ictx = aead_instance_ctx(inst);
+	struct authenc_request_ctx *areq_ctx = aead_request_ctx(req);
+	struct crypto_skcipher *enc = ctx->enc;
+	unsigned int cryptlen = req->cryptlen;
+	struct skcipher_request *skreq = (void *)(areq_ctx->tail +
+						  ictx->reqoff);
+	struct scatterlist *src, *dst;
+	int err;
+
+	src = scatterwalk_ffwd(areq_ctx->src, req->src, req->assoclen);
+	dst = src;
+
+	if (req->src != req->dst) {
+		memcpy_sglist(req->dst, req->src, req->assoclen);
+		dst = scatterwalk_ffwd(areq_ctx->dst, req->dst, req->assoclen);
+	}
+
+	skcipher_request_set_tfm(skreq, enc);
+	skcipher_request_set_callback(skreq, aead_request_flags(req),
+				      crypto_authenc_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_genicv(req, 0);
+}
+
+static void authenc_decrypt_tail_done(void *data, int err)
+{
+	struct aead_request *req = data;
+
+	authenc_request_complete(req, err);
+}
+
+static int crypto_authenc_decrypt_tail(struct aead_request *req,
+				       unsigned int mask)
+{
+	struct crypto_aead *authenc = crypto_aead_reqtfm(req);
+	struct aead_instance *inst = aead_alg_instance(authenc);
+	struct crypto_authenc_ctx *ctx = crypto_aead_ctx(authenc);
+	struct authenc_instance_ctx *ictx = aead_instance_ctx(inst);
+	struct authenc_request_ctx *areq_ctx = aead_request_ctx(req);
+	struct ahash_request *ahreq = (void *)(areq_ctx->tail + ictx->reqoff);
+	struct skcipher_request *skreq = (void *)(areq_ctx->tail +
+						  ictx->reqoff);
+	unsigned int authsize = crypto_aead_authsize(authenc);
+	unsigned int flags = aead_request_flags(req) & ~mask;
+	u8 *ihash = ahreq->result + authsize;
+	struct scatterlist *src, *dst;
+
+	scatterwalk_map_and_copy(ihash, req->src, ahreq->nbytes, authsize, 0);
+
+	if (crypto_memneq(ihash, ahreq->result, authsize))
+		return -EBADMSG;
+
+	src = scatterwalk_ffwd(areq_ctx->src, req->src, req->assoclen);
+	dst = src;
+
+	if (req->src != req->dst)
+		dst = scatterwalk_ffwd(areq_ctx->dst, req->dst, req->assoclen);
+
+	skcipher_request_set_tfm(skreq, ctx->enc);
+	skcipher_request_set_callback(skreq, flags,
+				      mask ? authenc_decrypt_tail_done :
+					     req->base.complete,
+				      mask ? req : req->base.data);
+	skcipher_request_set_crypt(skreq, src, dst,
+				   req->cryptlen - authsize, req->iv);
+
+	return crypto_skcipher_decrypt(skreq);
+}
+
+static void authenc_verify_ahash_done(void *data, int err)
+{
+	struct aead_request *req = data;
+
+	if (err) {
+		aead_request_complete(req, err);
+		return;
+	}
+	err = crypto_authenc_decrypt_tail(req, CRYPTO_TFM_REQ_MAY_SLEEP);
+	authenc_request_complete(req, err);
+}
+
+static int crypto_authenc_decrypt(struct aead_request *req)
+{
+	struct crypto_aead *authenc = crypto_aead_reqtfm(req);
+	unsigned int authsize = crypto_aead_authsize(authenc);
+	struct aead_instance *inst = aead_alg_instance(authenc);
+	struct crypto_authenc_ctx *ctx = crypto_aead_ctx(authenc);
+	struct authenc_instance_ctx *ictx = aead_instance_ctx(inst);
+	struct crypto_ahash *auth = ctx->auth;
+	struct authenc_request_ctx *areq_ctx = aead_request_ctx(req);
+	struct ahash_request *ahreq = (void *)(areq_ctx->tail + ictx->reqoff);
+	u8 *hash = areq_ctx->tail;
+	int err;
+
+	ahash_request_set_tfm(ahreq, auth);
+	ahash_request_set_crypt(ahreq, req->src, hash,
+				req->assoclen + req->cryptlen - authsize);
+	ahash_request_set_callback(ahreq, aead_request_flags(req),
+				   authenc_verify_ahash_done, req);
+
+	err = crypto_ahash_digest(ahreq);
+	if (err)
+		return err;
+
+	return crypto_authenc_decrypt_tail(req, 0);
+}
+
+static int crypto_authenc_init_tfm(struct crypto_aead *tfm)
+{
+	struct aead_instance *inst = aead_alg_instance(tfm);
+	struct authenc_instance_ctx *ictx = aead_instance_ctx(inst);
+	struct crypto_authenc_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;
+
+	crypto_aead_set_reqsize(
+		tfm,
+		sizeof(struct authenc_request_ctx) +
+		ictx->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_exit_tfm(struct crypto_aead *tfm)
+{
+	struct crypto_authenc_ctx *ctx = crypto_aead_ctx(tfm);
+
+	crypto_free_ahash(ctx->auth);
+	crypto_free_skcipher(ctx->enc);
+}
+
+static void crypto_authenc_free(struct aead_instance *inst)
+{
+	struct authenc_instance_ctx *ctx = aead_instance_ctx(inst);
+
+	crypto_drop_skcipher(&ctx->enc);
+	crypto_drop_ahash(&ctx->auth);
+	kfree(inst);
+}
+
+static int crypto_authenc_create(struct crypto_template *tmpl,
+				 struct rtattr **tb)
+{
+	u32 mask;
+	struct aead_instance *inst;
+	struct authenc_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;
+
+	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);
+
+	ctx->reqoff = 2 * auth->digestsize;
+
+	err = -ENAMETOOLONG;
+	if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
+		     "authenc(%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,
+		     "authenc(%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_ctx);
+
+	inst->alg.ivsize = enc->ivsize;
+	inst->alg.chunksize = enc->chunksize;
+	inst->alg.maxauthsize = auth->digestsize;
+
+	inst->alg.init = crypto_authenc_init_tfm;
+	inst->alg.exit = crypto_authenc_exit_tfm;
+
+	inst->alg.setkey = crypto_authenc_setkey;
+	inst->alg.encrypt = crypto_authenc_encrypt;
+	inst->alg.decrypt = crypto_authenc_decrypt;
+
+	inst->free = crypto_authenc_free;
+
+	err = aead_register_instance(tmpl, inst);
+	if (err) {
+err_free_inst:
+		crypto_authenc_free(inst);
+	}
+	return err;
+}
+
+static struct crypto_template crypto_authenc_tmpl = {
+	.name = "authenc",
+	.create = crypto_authenc_create,
+	.module = THIS_MODULE,
+};
+
+static int __init crypto_authenc_module_init(void)
+{
+	return crypto_register_template(&crypto_authenc_tmpl);
+}
+
+static void __exit crypto_authenc_module_exit(void)
+{
+	crypto_unregister_template(&crypto_authenc_tmpl);
+}
+
+module_init(crypto_authenc_module_init);
+module_exit(crypto_authenc_module_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Simple AEAD wrapper for IPsec");
+MODULE_ALIAS_CRYPTO("authenc");