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, 315 insertions, 0 deletions

diff --git a/include/crypto/internal/skcipher.h b/include/crypto/internal/skcipher.h
new file mode 100644
index 000000000..a965b6aab
--- /dev/null
+++ b/include/crypto/internal/skcipher.h
@@ -0,0 +1,315 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Symmetric key ciphers.
+ * 
+ * Copyright (c) 2007 Herbert Xu <herbert@gondor.apana.org.au>
+ */
+
+#ifndef _CRYPTO_INTERNAL_SKCIPHER_H
+#define _CRYPTO_INTERNAL_SKCIPHER_H
+
+#include <crypto/algapi.h>
+#include <crypto/internal/cipher.h>
+#include <crypto/skcipher.h>
+#include <linux/types.h>
+
+/*
+ * Set this if your algorithm is sync but needs a reqsize larger
+ * than MAX_SYNC_SKCIPHER_REQSIZE.
+ *
+ * Reuse bit that is specific to hash algorithms.
+ */
+#define CRYPTO_ALG_SKCIPHER_REQSIZE_LARGE CRYPTO_ALG_OPTIONAL_KEY
+
+struct aead_request;
+struct rtattr;
+
+struct skcipher_instance {
+	void (*free)(struct skcipher_instance *inst);
+	union {
+		struct {
+			char head[offsetof(struct skcipher_alg, base)];
+			struct crypto_instance base;
+		} s;
+		struct skcipher_alg alg;
+	};
+};
+
+struct lskcipher_instance {
+	void (*free)(struct lskcipher_instance *inst);
+	union {
+		struct {
+			char head[offsetof(struct lskcipher_alg, co.base)];
+			struct crypto_instance base;
+		} s;
+		struct lskcipher_alg alg;
+	};
+};
+
+struct crypto_skcipher_spawn {
+	struct crypto_spawn base;
+};
+
+struct crypto_lskcipher_spawn {
+	struct crypto_spawn base;
+};
+
+struct skcipher_walk {
+	union {
+		/* Virtual address of the source. */
+		struct {
+			struct {
+				const void *const addr;
+			} virt;
+		} src;
+
+		/* Private field for the API, do not use. */
+		struct scatter_walk in;
+	};
+
+	union {
+		/* Virtual address of the destination. */
+		struct {
+			struct {
+				void *const addr;
+			} virt;
+		} dst;
+
+		/* Private field for the API, do not use. */
+		struct scatter_walk out;
+	};
+
+	unsigned int nbytes;
+	unsigned int total;
+
+	u8 *page;
+	u8 *buffer;
+	u8 *oiv;
+	void *iv;
+
+	unsigned int ivsize;
+
+	int flags;
+	unsigned int blocksize;
+	unsigned int stride;
+	unsigned int alignmask;
+};
+
+static inline struct crypto_instance *skcipher_crypto_instance(
+	struct skcipher_instance *inst)
+{
+	return &inst->s.base;
+}
+
+static inline struct crypto_instance *lskcipher_crypto_instance(
+	struct lskcipher_instance *inst)
+{
+	return &inst->s.base;
+}
+
+static inline struct skcipher_instance *skcipher_alg_instance(
+	struct crypto_skcipher *skcipher)
+{
+	return container_of(crypto_skcipher_alg(skcipher),
+			    struct skcipher_instance, alg);
+}
+
+static inline struct lskcipher_instance *lskcipher_alg_instance(
+	struct crypto_lskcipher *lskcipher)
+{
+	return container_of(crypto_lskcipher_alg(lskcipher),
+			    struct lskcipher_instance, alg);
+}
+
+static inline void *skcipher_instance_ctx(struct skcipher_instance *inst)
+{
+	return crypto_instance_ctx(skcipher_crypto_instance(inst));
+}
+
+static inline void *lskcipher_instance_ctx(struct lskcipher_instance *inst)
+{
+	return crypto_instance_ctx(lskcipher_crypto_instance(inst));
+}
+
+static inline void skcipher_request_complete(struct skcipher_request *req, int err)
+{
+	crypto_request_complete(&req->base, err);
+}
+
+int crypto_grab_skcipher(struct crypto_skcipher_spawn *spawn,
+			 struct crypto_instance *inst,
+			 const char *name, u32 type, u32 mask);
+
+int crypto_grab_lskcipher(struct crypto_lskcipher_spawn *spawn,
+			  struct crypto_instance *inst,
+			  const char *name, u32 type, u32 mask);
+
+static inline void crypto_drop_skcipher(struct crypto_skcipher_spawn *spawn)
+{
+	crypto_drop_spawn(&spawn->base);
+}
+
+static inline void crypto_drop_lskcipher(struct crypto_lskcipher_spawn *spawn)
+{
+	crypto_drop_spawn(&spawn->base);
+}
+
+static inline struct lskcipher_alg *crypto_lskcipher_spawn_alg(
+	struct crypto_lskcipher_spawn *spawn)
+{
+	return container_of(spawn->base.alg, struct lskcipher_alg, co.base);
+}
+
+static inline struct skcipher_alg_common *crypto_spawn_skcipher_alg_common(
+	struct crypto_skcipher_spawn *spawn)
+{
+	return container_of(spawn->base.alg, struct skcipher_alg_common, base);
+}
+
+static inline struct lskcipher_alg *crypto_spawn_lskcipher_alg(
+	struct crypto_lskcipher_spawn *spawn)
+{
+	return crypto_lskcipher_spawn_alg(spawn);
+}
+
+static inline struct crypto_skcipher *crypto_spawn_skcipher(
+	struct crypto_skcipher_spawn *spawn)
+{
+	return crypto_spawn_tfm2(&spawn->base);
+}
+
+static inline struct crypto_lskcipher *crypto_spawn_lskcipher(
+	struct crypto_lskcipher_spawn *spawn)
+{
+	return crypto_spawn_tfm2(&spawn->base);
+}
+
+static inline void crypto_skcipher_set_reqsize(
+	struct crypto_skcipher *skcipher, unsigned int reqsize)
+{
+	skcipher->reqsize = reqsize;
+}
+
+static inline void crypto_skcipher_set_reqsize_dma(
+	struct crypto_skcipher *skcipher, unsigned int reqsize)
+{
+	reqsize += crypto_dma_align() & ~(crypto_tfm_ctx_alignment() - 1);
+	skcipher->reqsize = reqsize;
+}
+
+int crypto_register_skcipher(struct skcipher_alg *alg);
+void crypto_unregister_skcipher(struct skcipher_alg *alg);
+int crypto_register_skciphers(struct skcipher_alg *algs, int count);
+void crypto_unregister_skciphers(struct skcipher_alg *algs, int count);
+int skcipher_register_instance(struct crypto_template *tmpl,
+			       struct skcipher_instance *inst);
+
+int crypto_register_lskcipher(struct lskcipher_alg *alg);
+void crypto_unregister_lskcipher(struct lskcipher_alg *alg);
+int crypto_register_lskciphers(struct lskcipher_alg *algs, int count);
+void crypto_unregister_lskciphers(struct lskcipher_alg *algs, int count);
+int lskcipher_register_instance(struct crypto_template *tmpl,
+				struct lskcipher_instance *inst);
+
+int skcipher_walk_done(struct skcipher_walk *walk, int res);
+int skcipher_walk_virt(struct skcipher_walk *__restrict walk,
+		       struct skcipher_request *__restrict req,
+		       bool atomic);
+int skcipher_walk_aead_encrypt(struct skcipher_walk *__restrict walk,
+			       struct aead_request *__restrict req,
+			       bool atomic);
+int skcipher_walk_aead_decrypt(struct skcipher_walk *__restrict walk,
+			       struct aead_request *__restrict req,
+			       bool atomic);
+
+static inline void skcipher_walk_abort(struct skcipher_walk *walk)
+{
+	skcipher_walk_done(walk, -ECANCELED);
+}
+
+static inline void *crypto_skcipher_ctx(struct crypto_skcipher *tfm)
+{
+	return crypto_tfm_ctx(&tfm->base);
+}
+
+static inline void *crypto_lskcipher_ctx(struct crypto_lskcipher *tfm)
+{
+	return crypto_tfm_ctx(&tfm->base);
+}
+
+static inline void *crypto_skcipher_ctx_dma(struct crypto_skcipher *tfm)
+{
+	return crypto_tfm_ctx_dma(&tfm->base);
+}
+
+static inline bool crypto_skcipher_tested(struct crypto_skcipher *tfm)
+{
+	struct crypto_tfm *tfm_base = crypto_skcipher_tfm(tfm);
+
+	return tfm_base->__crt_alg->cra_flags & CRYPTO_ALG_TESTED;
+}
+
+static inline void *skcipher_request_ctx(struct skcipher_request *req)
+{
+	return req->__ctx;
+}
+
+static inline void *skcipher_request_ctx_dma(struct skcipher_request *req)
+{
+	unsigned int align = crypto_dma_align();
+
+	if (align <= crypto_tfm_ctx_alignment())
+		align = 1;
+
+	return PTR_ALIGN(skcipher_request_ctx(req), align);
+}
+
+static inline u32 skcipher_request_flags(struct skcipher_request *req)
+{
+	return req->base.flags;
+}
+
+/* Helpers for simple block cipher modes of operation */
+struct skcipher_ctx_simple {
+	struct crypto_cipher *cipher;	/* underlying block cipher */
+};
+static inline struct crypto_cipher *
+skcipher_cipher_simple(struct crypto_skcipher *tfm)
+{
+	struct skcipher_ctx_simple *ctx = crypto_skcipher_ctx(tfm);
+
+	return ctx->cipher;
+}
+
+struct skcipher_instance *skcipher_alloc_instance_simple(
+	struct crypto_template *tmpl, struct rtattr **tb);
+
+static inline struct crypto_alg *skcipher_ialg_simple(
+	struct skcipher_instance *inst)
+{
+	struct crypto_cipher_spawn *spawn = skcipher_instance_ctx(inst);
+
+	return crypto_spawn_cipher_alg(spawn);
+}
+
+static inline struct crypto_lskcipher *lskcipher_cipher_simple(
+	struct crypto_lskcipher *tfm)
+{
+	struct crypto_lskcipher **ctx = crypto_lskcipher_ctx(tfm);
+
+	return *ctx;
+}
+
+struct lskcipher_instance *lskcipher_alloc_instance_simple(
+	struct crypto_template *tmpl, struct rtattr **tb);
+
+static inline struct lskcipher_alg *lskcipher_ialg_simple(
+	struct lskcipher_instance *inst)
+{
+	struct crypto_lskcipher_spawn *spawn = lskcipher_instance_ctx(inst);
+
+	return crypto_lskcipher_spawn_alg(spawn);
+}
+
+#endif	/* _CRYPTO_INTERNAL_SKCIPHER_H */
+