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, 313 insertions, 0 deletions

diff --git a/crypto/aead.c b/crypto/aead.c
new file mode 100644
index 000000000..045b74c37
--- /dev/null
+++ b/crypto/aead.c
@@ -0,0 +1,313 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * AEAD: Authenticated Encryption with Associated Data
+ *
+ * This file provides API support for AEAD algorithms.
+ *
+ * Copyright (c) 2007-2015 Herbert Xu <herbert@gondor.apana.org.au>
+ */
+
+#include <crypto/internal/aead.h>
+#include <linux/cryptouser.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/seq_file.h>
+#include <linux/string.h>
+#include <linux/string_choices.h>
+#include <net/netlink.h>
+
+#include "internal.h"
+
+static int setkey_unaligned(struct crypto_aead *tfm, const u8 *key,
+			    unsigned int keylen)
+{
+	unsigned long alignmask = crypto_aead_alignmask(tfm);
+	int ret;
+	u8 *buffer, *alignbuffer;
+	unsigned long absize;
+
+	absize = keylen + alignmask;
+	buffer = kmalloc(absize, GFP_ATOMIC);
+	if (!buffer)
+		return -ENOMEM;
+
+	alignbuffer = (u8 *)ALIGN((unsigned long)buffer, alignmask + 1);
+	memcpy(alignbuffer, key, keylen);
+	ret = crypto_aead_alg(tfm)->setkey(tfm, alignbuffer, keylen);
+	kfree_sensitive(buffer);
+	return ret;
+}
+
+int crypto_aead_setkey(struct crypto_aead *tfm,
+		       const u8 *key, unsigned int keylen)
+{
+	unsigned long alignmask = crypto_aead_alignmask(tfm);
+	int err;
+
+	if ((unsigned long)key & alignmask)
+		err = setkey_unaligned(tfm, key, keylen);
+	else
+		err = crypto_aead_alg(tfm)->setkey(tfm, key, keylen);
+
+	if (unlikely(err)) {
+		crypto_aead_set_flags(tfm, CRYPTO_TFM_NEED_KEY);
+		return err;
+	}
+
+	crypto_aead_clear_flags(tfm, CRYPTO_TFM_NEED_KEY);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(crypto_aead_setkey);
+
+int crypto_aead_setauthsize(struct crypto_aead *tfm, unsigned int authsize)
+{
+	int err;
+
+	if ((!authsize && crypto_aead_maxauthsize(tfm)) ||
+	    authsize > crypto_aead_maxauthsize(tfm))
+		return -EINVAL;
+
+	if (crypto_aead_alg(tfm)->setauthsize) {
+		err = crypto_aead_alg(tfm)->setauthsize(tfm, authsize);
+		if (err)
+			return err;
+	}
+
+	tfm->authsize = authsize;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(crypto_aead_setauthsize);
+
+int crypto_aead_encrypt(struct aead_request *req)
+{
+	struct crypto_aead *aead = crypto_aead_reqtfm(req);
+
+	if (crypto_aead_get_flags(aead) & CRYPTO_TFM_NEED_KEY)
+		return -ENOKEY;
+
+	return crypto_aead_alg(aead)->encrypt(req);
+}
+EXPORT_SYMBOL_GPL(crypto_aead_encrypt);
+
+int crypto_aead_decrypt(struct aead_request *req)
+{
+	struct crypto_aead *aead = crypto_aead_reqtfm(req);
+
+	if (crypto_aead_get_flags(aead) & CRYPTO_TFM_NEED_KEY)
+		return -ENOKEY;
+
+	if (req->cryptlen < crypto_aead_authsize(aead))
+		return -EINVAL;
+
+	return crypto_aead_alg(aead)->decrypt(req);
+}
+EXPORT_SYMBOL_GPL(crypto_aead_decrypt);
+
+static void crypto_aead_exit_tfm(struct crypto_tfm *tfm)
+{
+	struct crypto_aead *aead = __crypto_aead_cast(tfm);
+	struct aead_alg *alg = crypto_aead_alg(aead);
+
+	alg->exit(aead);
+}
+
+static int crypto_aead_init_tfm(struct crypto_tfm *tfm)
+{
+	struct crypto_aead *aead = __crypto_aead_cast(tfm);
+	struct aead_alg *alg = crypto_aead_alg(aead);
+
+	crypto_aead_set_flags(aead, CRYPTO_TFM_NEED_KEY);
+	crypto_aead_set_reqsize(aead, crypto_tfm_alg_reqsize(tfm));
+
+	aead->authsize = alg->maxauthsize;
+
+	if (alg->exit)
+		aead->base.exit = crypto_aead_exit_tfm;
+
+	if (alg->init)
+		return alg->init(aead);
+
+	return 0;
+}
+
+static int __maybe_unused crypto_aead_report(
+	struct sk_buff *skb, struct crypto_alg *alg)
+{
+	struct aead_alg *aead = container_of(alg, struct aead_alg, base);
+	struct crypto_report_aead raead = {
+		.type = "aead",
+		.geniv = "<none>",
+	};
+
+	raead.blocksize = alg->cra_blocksize;
+	raead.maxauthsize = aead->maxauthsize;
+	raead.ivsize = aead->ivsize;
+
+	return nla_put(skb, CRYPTOCFGA_REPORT_AEAD, sizeof(raead), &raead);
+}
+
+static void __maybe_unused crypto_aead_show(struct seq_file *m,
+					    struct crypto_alg *alg)
+{
+	struct aead_alg *aead = container_of(alg, struct aead_alg, base);
+
+	seq_printf(m, "type         : aead\n");
+	seq_printf(m, "async        : %s\n",
+		   str_yes_no(alg->cra_flags & CRYPTO_ALG_ASYNC));
+	seq_printf(m, "blocksize    : %u\n", alg->cra_blocksize);
+	seq_printf(m, "ivsize       : %u\n", aead->ivsize);
+	seq_printf(m, "maxauthsize  : %u\n", aead->maxauthsize);
+	seq_printf(m, "geniv        : <none>\n");
+}
+
+static void crypto_aead_free_instance(struct crypto_instance *inst)
+{
+	struct aead_instance *aead = aead_instance(inst);
+
+	aead->free(aead);
+}
+
+static const struct crypto_type crypto_aead_type = {
+	.extsize = crypto_alg_extsize,
+	.init_tfm = crypto_aead_init_tfm,
+	.free = crypto_aead_free_instance,
+#ifdef CONFIG_PROC_FS
+	.show = crypto_aead_show,
+#endif
+#if IS_ENABLED(CONFIG_CRYPTO_USER)
+	.report = crypto_aead_report,
+#endif
+	.maskclear = ~CRYPTO_ALG_TYPE_MASK,
+	.maskset = CRYPTO_ALG_TYPE_MASK,
+	.type = CRYPTO_ALG_TYPE_AEAD,
+	.tfmsize = offsetof(struct crypto_aead, base),
+	.algsize = offsetof(struct aead_alg, base),
+};
+
+int crypto_grab_aead(struct crypto_aead_spawn *spawn,
+		     struct crypto_instance *inst,
+		     const char *name, u32 type, u32 mask)
+{
+	spawn->base.frontend = &crypto_aead_type;
+	return crypto_grab_spawn(&spawn->base, inst, name, type, mask);
+}
+EXPORT_SYMBOL_GPL(crypto_grab_aead);
+
+struct crypto_aead *crypto_alloc_aead(const char *alg_name, u32 type, u32 mask)
+{
+	return crypto_alloc_tfm(alg_name, &crypto_aead_type, type, mask);
+}
+EXPORT_SYMBOL_GPL(crypto_alloc_aead);
+
+struct crypto_sync_aead *crypto_alloc_sync_aead(const char *alg_name, u32 type, u32 mask)
+{
+	struct crypto_aead *tfm;
+
+	/* Only sync algorithms are allowed. */
+	mask |= CRYPTO_ALG_ASYNC;
+	type &= ~(CRYPTO_ALG_ASYNC);
+
+	tfm = crypto_alloc_tfm(alg_name, &crypto_aead_type, type, mask);
+
+	if (!IS_ERR(tfm) && WARN_ON(crypto_aead_reqsize(tfm) > MAX_SYNC_AEAD_REQSIZE)) {
+		crypto_free_aead(tfm);
+		return ERR_PTR(-EINVAL);
+	}
+
+	return (struct crypto_sync_aead *)tfm;
+}
+EXPORT_SYMBOL_GPL(crypto_alloc_sync_aead);
+
+int crypto_has_aead(const char *alg_name, u32 type, u32 mask)
+{
+	return crypto_type_has_alg(alg_name, &crypto_aead_type, type, mask);
+}
+EXPORT_SYMBOL_GPL(crypto_has_aead);
+
+static int aead_prepare_alg(struct aead_alg *alg)
+{
+	struct crypto_alg *base = &alg->base;
+
+	if (max3(alg->maxauthsize, alg->ivsize, alg->chunksize) >
+	    PAGE_SIZE / 8)
+		return -EINVAL;
+
+	if (!alg->chunksize)
+		alg->chunksize = base->cra_blocksize;
+
+	base->cra_type = &crypto_aead_type;
+	base->cra_flags &= ~CRYPTO_ALG_TYPE_MASK;
+	base->cra_flags |= CRYPTO_ALG_TYPE_AEAD;
+
+	return 0;
+}
+
+int crypto_register_aead(struct aead_alg *alg)
+{
+	struct crypto_alg *base = &alg->base;
+	int err;
+
+	err = aead_prepare_alg(alg);
+	if (err)
+		return err;
+
+	return crypto_register_alg(base);
+}
+EXPORT_SYMBOL_GPL(crypto_register_aead);
+
+void crypto_unregister_aead(struct aead_alg *alg)
+{
+	crypto_unregister_alg(&alg->base);
+}
+EXPORT_SYMBOL_GPL(crypto_unregister_aead);
+
+int crypto_register_aeads(struct aead_alg *algs, int count)
+{
+	int i, ret;
+
+	for (i = 0; i < count; i++) {
+		ret = crypto_register_aead(&algs[i]);
+		if (ret)
+			goto err;
+	}
+
+	return 0;
+
+err:
+	for (--i; i >= 0; --i)
+		crypto_unregister_aead(&algs[i]);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(crypto_register_aeads);
+
+void crypto_unregister_aeads(struct aead_alg *algs, int count)
+{
+	int i;
+
+	for (i = count - 1; i >= 0; --i)
+		crypto_unregister_aead(&algs[i]);
+}
+EXPORT_SYMBOL_GPL(crypto_unregister_aeads);
+
+int aead_register_instance(struct crypto_template *tmpl,
+			   struct aead_instance *inst)
+{
+	int err;
+
+	if (WARN_ON(!inst->free))
+		return -EINVAL;
+
+	err = aead_prepare_alg(&inst->alg);
+	if (err)
+		return err;
+
+	return crypto_register_instance(tmpl, aead_crypto_instance(inst));
+}
+EXPORT_SYMBOL_GPL(aead_register_instance);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Authenticated Encryption with Associated Data (AEAD)");