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, 228 insertions, 0 deletions

diff --git a/security/integrity/digsig.c b/security/integrity/digsig.c
new file mode 100644
index 000000000..1ed686154
--- /dev/null
+++ b/security/integrity/digsig.c
@@ -0,0 +1,228 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2011 Intel Corporation
+ *
+ * Author:
+ * Dmitry Kasatkin <dmitry.kasatkin@intel.com>
+ */
+
+#include <linux/err.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/cred.h>
+#include <linux/kernel_read_file.h>
+#include <linux/key-type.h>
+#include <linux/digsig.h>
+#include <linux/vmalloc.h>
+#include <crypto/public_key.h>
+#include <keys/system_keyring.h>
+
+#include "integrity.h"
+
+static struct key *keyring[INTEGRITY_KEYRING_MAX];
+
+static const char * const keyring_name[INTEGRITY_KEYRING_MAX] = {
+#ifndef CONFIG_INTEGRITY_TRUSTED_KEYRING
+	"_evm",
+	"_ima",
+#else
+	".evm",
+	".ima",
+#endif
+	".platform",
+	".machine",
+};
+
+#ifdef CONFIG_IMA_KEYRINGS_PERMIT_SIGNED_BY_BUILTIN_OR_SECONDARY
+#define restrict_link_to_ima restrict_link_by_digsig_builtin_and_secondary
+#else
+#define restrict_link_to_ima restrict_link_by_digsig_builtin
+#endif
+
+static struct key *integrity_keyring_from_id(const unsigned int id)
+{
+	if (id >= INTEGRITY_KEYRING_MAX)
+		return ERR_PTR(-EINVAL);
+
+	if (!keyring[id]) {
+		keyring[id] =
+			request_key(&key_type_keyring, keyring_name[id], NULL);
+		if (IS_ERR(keyring[id])) {
+			int err = PTR_ERR(keyring[id]);
+			pr_err("no %s keyring: %d\n", keyring_name[id], err);
+			keyring[id] = NULL;
+			return ERR_PTR(err);
+		}
+	}
+
+	return keyring[id];
+}
+
+int integrity_digsig_verify(const unsigned int id, const char *sig, int siglen,
+			    const char *digest, int digestlen, u8 algo)
+{
+	struct key *keyring;
+
+	if (siglen < 2)
+		return -EINVAL;
+
+	keyring = integrity_keyring_from_id(id);
+	if (IS_ERR(keyring))
+		return PTR_ERR(keyring);
+
+	switch (sig[1]) {
+	case 1:
+		/* v1 API expect signature without xattr type */
+		return digsig_verify(keyring, sig + 1, siglen - 1, digest,
+				     digestlen);
+	case 2: /* regular file data hash based signature */
+		return asymmetric_verify(keyring, sig, siglen, digest,
+					    digestlen);
+	case 3: /* struct ima_file_id data based signature */
+		return asymmetric_verify_v3(keyring, sig, siglen, digest,
+					    digestlen, algo);
+	}
+
+	return -EOPNOTSUPP;
+}
+
+int integrity_modsig_verify(const unsigned int id, const struct modsig *modsig)
+{
+	struct key *keyring;
+
+	keyring = integrity_keyring_from_id(id);
+	if (IS_ERR(keyring))
+		return PTR_ERR(keyring);
+
+	return ima_modsig_verify(keyring, modsig);
+}
+
+static int __init __integrity_init_keyring(const unsigned int id,
+					   key_perm_t perm,
+					   struct key_restriction *restriction)
+{
+	const struct cred *cred = current_cred();
+	int err = 0;
+
+	keyring[id] = keyring_alloc(keyring_name[id], KUIDT_INIT(0),
+				    KGIDT_INIT(0), cred, perm,
+				    KEY_ALLOC_NOT_IN_QUOTA, restriction, NULL);
+	if (IS_ERR(keyring[id])) {
+		err = PTR_ERR(keyring[id]);
+		pr_info("Can't allocate %s keyring (%d)\n",
+			keyring_name[id], err);
+		keyring[id] = NULL;
+	} else {
+		if (id == INTEGRITY_KEYRING_PLATFORM)
+			set_platform_trusted_keys(keyring[id]);
+		if (id == INTEGRITY_KEYRING_MACHINE && imputed_trust_enabled())
+			set_machine_trusted_keys(keyring[id]);
+		if (id == INTEGRITY_KEYRING_IMA)
+			load_module_cert(keyring[id]);
+	}
+
+	return err;
+}
+
+int __init integrity_init_keyring(const unsigned int id)
+{
+	struct key_restriction *restriction;
+	key_perm_t perm;
+	int ret;
+
+	perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW
+		| KEY_USR_READ | KEY_USR_SEARCH;
+
+	if (id == INTEGRITY_KEYRING_PLATFORM ||
+	    (id == INTEGRITY_KEYRING_MACHINE &&
+	    !IS_ENABLED(CONFIG_INTEGRITY_CA_MACHINE_KEYRING))) {
+		restriction = NULL;
+		goto out;
+	}
+
+	if (!IS_ENABLED(CONFIG_INTEGRITY_TRUSTED_KEYRING))
+		return 0;
+
+	restriction = kzalloc_obj(struct key_restriction);
+	if (!restriction)
+		return -ENOMEM;
+
+	if (id == INTEGRITY_KEYRING_MACHINE)
+		restriction->check = restrict_link_by_ca;
+	else
+		restriction->check = restrict_link_to_ima;
+
+	/*
+	 * MOK keys can only be added through a read-only runtime services
+	 * UEFI variable during boot. No additional keys shall be allowed to
+	 * load into the machine keyring following init from userspace.
+	 */
+	if (id != INTEGRITY_KEYRING_MACHINE)
+		perm |= KEY_USR_WRITE;
+
+out:
+	ret = __integrity_init_keyring(id, perm, restriction);
+	if (ret)
+		kfree(restriction);
+	return ret;
+}
+
+static int __init integrity_add_key(const unsigned int id, const void *data,
+				    off_t size, key_perm_t perm)
+{
+	key_ref_t key;
+	int rc = 0;
+
+	if (!keyring[id])
+		return -EINVAL;
+
+	key = key_create_or_update(make_key_ref(keyring[id], 1), "asymmetric",
+				   NULL, data, size, perm,
+				   KEY_ALLOC_NOT_IN_QUOTA);
+	if (IS_ERR(key)) {
+		rc = PTR_ERR(key);
+		if (id != INTEGRITY_KEYRING_MACHINE)
+			pr_err("Problem loading X.509 certificate %d\n", rc);
+	} else {
+		pr_notice("Loaded X.509 cert '%s'\n",
+			  key_ref_to_ptr(key)->description);
+		key_ref_put(key);
+	}
+
+	return rc;
+
+}
+
+int __init integrity_load_x509(const unsigned int id, const char *path)
+{
+	void *data = NULL;
+	size_t size;
+	int rc;
+	key_perm_t perm;
+
+	rc = kernel_read_file_from_path(path, 0, &data, INT_MAX, NULL,
+					READING_X509_CERTIFICATE);
+	if (rc < 0) {
+		pr_err("Unable to open file: %s (%d)", path, rc);
+		return rc;
+	}
+	size = rc;
+
+	perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW | KEY_USR_READ;
+
+	pr_info("Loading X.509 certificate: %s\n", path);
+	rc = integrity_add_key(id, (const void *)data, size, perm);
+
+	vfree(data);
+	return rc;
+}
+
+int __init integrity_load_cert(const unsigned int id, const char *source,
+			       const void *data, size_t len, key_perm_t perm)
+{
+	if (!data)
+		return -EINVAL;
+
+	pr_info("Loading X.509 certificate: %s\n", source);
+	return integrity_add_key(id, data, len, perm);
+}