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, 281 insertions, 0 deletions

diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
new file mode 100644
index 000000000..0c581c03c
--- /dev/null
+++ b/security/integrity/integrity.h
@@ -0,0 +1,281 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2009-2010 IBM Corporation
+ *
+ * Authors:
+ * Mimi Zohar <zohar@us.ibm.com>
+ */
+
+#ifdef pr_fmt
+#undef pr_fmt
+#endif
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/types.h>
+#include <linux/integrity.h>
+#include <linux/secure_boot.h>
+#include <crypto/sha1.h>
+#include <crypto/hash.h>
+#include <linux/key.h>
+#include <linux/audit.h>
+#include <linux/lsm_hooks.h>
+
+enum evm_ima_xattr_type {
+	IMA_XATTR_DIGEST = 0x01,
+	EVM_XATTR_HMAC,
+	EVM_IMA_XATTR_DIGSIG,
+	IMA_XATTR_DIGEST_NG,
+	EVM_XATTR_PORTABLE_DIGSIG,
+	IMA_VERITY_DIGSIG,
+	IMA_XATTR_LAST
+};
+
+struct evm_ima_xattr_data {
+	/* New members must be added within the __struct_group() macro below. */
+	__struct_group(evm_ima_xattr_data_hdr, hdr, __packed,
+		u8 type;
+	);
+	u8 data[];
+} __packed;
+static_assert(offsetof(struct evm_ima_xattr_data, data) == sizeof(struct evm_ima_xattr_data_hdr),
+	      "struct member likely outside of __struct_group()");
+
+/* Only used in the EVM HMAC code. */
+struct evm_xattr {
+	struct evm_ima_xattr_data_hdr data;
+	u8 digest[SHA1_DIGEST_SIZE];
+} __packed;
+
+#define IMA_MAX_DIGEST_SIZE	HASH_MAX_DIGESTSIZE
+
+struct ima_digest_data {
+	/* New members must be added within the __struct_group() macro below. */
+	__struct_group(ima_digest_data_hdr, hdr, __packed,
+	u8 algo;
+	u8 length;
+	union {
+		struct {
+			u8 unused;
+			u8 type;
+		} sha1;
+		struct {
+			u8 type;
+			u8 algo;
+		} ng;
+		u8 data[2];
+	} xattr;
+	);
+	u8 digest[];
+} __packed;
+static_assert(offsetof(struct ima_digest_data, digest) == sizeof(struct ima_digest_data_hdr),
+	      "struct member likely outside of __struct_group()");
+
+/*
+ * Instead of wrapping the ima_digest_data struct inside a local structure
+ * with the maximum hash size, define ima_max_digest_data struct.
+ */
+struct ima_max_digest_data {
+	struct ima_digest_data_hdr hdr;
+	u8 digest[HASH_MAX_DIGESTSIZE];
+} __packed;
+
+/*
+ * signature header format v2 - for using with asymmetric keys
+ *
+ * The signature_v2_hdr struct includes a signature format version
+ * to simplify defining new signature formats.
+ *
+ * signature format:
+ * version 2: regular file data hash based signature
+ * version 3: struct ima_file_id data based signature
+ */
+struct signature_v2_hdr {
+	uint8_t type;		/* xattr type */
+	uint8_t version;	/* signature format version */
+	uint8_t	hash_algo;	/* Digest algorithm [enum hash_algo] */
+	__be32 keyid;		/* IMA key identifier - not X509/PGP specific */
+	__be16 sig_size;	/* signature size */
+	uint8_t sig[];		/* signature payload */
+} __packed;
+
+/*
+ * IMA signature version 3 disambiguates the data that is signed, by
+ * indirectly signing the hash of the ima_file_id structure data,
+ * containing either the fsverity_descriptor struct digest or, in the
+ * future, the regular IMA file hash.
+ *
+ * (The hash of the ima_file_id structure is only of the portion used.)
+ */
+struct ima_file_id {
+	__u8 hash_type;		/* xattr type [enum evm_ima_xattr_type] */
+	__u8 hash_algorithm;	/* Digest algorithm [enum hash_algo] */
+	__u8 hash[HASH_MAX_DIGESTSIZE];
+} __packed;
+
+int integrity_kernel_read(struct file *file, loff_t offset,
+			  void *addr, unsigned long count);
+int __init integrity_fs_init(void);
+void __init integrity_fs_fini(void);
+
+#define INTEGRITY_KEYRING_EVM		0
+#define INTEGRITY_KEYRING_IMA		1
+#define INTEGRITY_KEYRING_PLATFORM	2
+#define INTEGRITY_KEYRING_MACHINE	3
+#define INTEGRITY_KEYRING_MAX		4
+
+extern struct dentry *integrity_dir;
+
+struct modsig;
+
+#ifdef CONFIG_INTEGRITY_SIGNATURE
+
+int integrity_digsig_verify(const unsigned int id, const char *sig, int siglen,
+			    const char *digest, int digestlen, u8 algo);
+int integrity_modsig_verify(unsigned int id, const struct modsig *modsig);
+
+int __init integrity_init_keyring(const unsigned int id);
+int __init integrity_load_x509(const unsigned int id, const char *path);
+int __init integrity_load_cert(const unsigned int id, const char *source,
+			       const void *data, size_t len, key_perm_t perm);
+#else
+
+static inline int integrity_digsig_verify(const unsigned int id,
+					  const char *sig, int siglen,
+					  const char *digest, int digestlen,
+					  u8 algo)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int integrity_modsig_verify(unsigned int id,
+					  const struct modsig *modsig)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int integrity_init_keyring(const unsigned int id)
+{
+	return 0;
+}
+
+static inline int __init integrity_load_cert(const unsigned int id,
+					     const char *source,
+					     const void *data, size_t len,
+					     key_perm_t perm)
+{
+	return 0;
+}
+#endif /* CONFIG_INTEGRITY_SIGNATURE */
+
+#ifdef CONFIG_INTEGRITY_ASYMMETRIC_KEYS
+int asymmetric_verify(struct key *keyring, const char *sig,
+		      int siglen, const char *data, int datalen);
+int asymmetric_verify_v3(struct key *keyring, const char *sig,
+			 int siglen, const char *data, int datalen, u8 algo);
+#else
+static inline int asymmetric_verify(struct key *keyring, const char *sig,
+				    int siglen, const char *data, int datalen)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int asymmetric_verify_v3(struct key *keyring,
+				       const char *sig, int siglen,
+				       const char *data, int datalen, u8 algo)
+{
+	return -EOPNOTSUPP;
+}
+#endif
+
+#ifdef CONFIG_IMA_APPRAISE_MODSIG
+int ima_modsig_verify(struct key *keyring, const struct modsig *modsig);
+#else
+static inline int ima_modsig_verify(struct key *keyring,
+				    const struct modsig *modsig)
+{
+	return -EOPNOTSUPP;
+}
+#endif
+
+#ifdef CONFIG_IMA_LOAD_X509
+void __init ima_load_x509(void);
+#else
+static inline void ima_load_x509(void)
+{
+}
+#endif
+
+#ifdef CONFIG_EVM_LOAD_X509
+void __init evm_load_x509(void);
+#else
+static inline void evm_load_x509(void)
+{
+}
+#endif
+
+#ifdef CONFIG_INTEGRITY_AUDIT
+/* declarations */
+void integrity_audit_msg(int audit_msgno, struct inode *inode,
+			 const unsigned char *fname, const char *op,
+			 const char *cause, int result, int info);
+
+void integrity_audit_message(int audit_msgno, struct inode *inode,
+			     const unsigned char *fname, const char *op,
+			     const char *cause, int result, int info,
+			     int errno);
+
+static inline struct audit_buffer *
+integrity_audit_log_start(struct audit_context *ctx, gfp_t gfp_mask, int type)
+{
+	return audit_log_start(ctx, gfp_mask, type);
+}
+
+#else
+static inline void integrity_audit_msg(int audit_msgno, struct inode *inode,
+				       const unsigned char *fname,
+				       const char *op, const char *cause,
+				       int result, int info)
+{
+}
+
+static inline void integrity_audit_message(int audit_msgno,
+					   struct inode *inode,
+					   const unsigned char *fname,
+					   const char *op, const char *cause,
+					   int result, int info, int errno)
+{
+}
+
+static inline struct audit_buffer *
+integrity_audit_log_start(struct audit_context *ctx, gfp_t gfp_mask, int type)
+{
+	return NULL;
+}
+
+#endif
+
+#ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
+void __init add_to_platform_keyring(const char *source, const void *data,
+				    size_t len);
+#else
+static inline void __init add_to_platform_keyring(const char *source,
+						  const void *data, size_t len)
+{
+}
+#endif
+
+#ifdef CONFIG_INTEGRITY_MACHINE_KEYRING
+void __init add_to_machine_keyring(const char *source, const void *data, size_t len);
+bool __init imputed_trust_enabled(void);
+#else
+static inline void __init add_to_machine_keyring(const char *source,
+						  const void *data, size_t len)
+{
+}
+
+static inline bool __init imputed_trust_enabled(void)
+{
+	return false;
+}
+#endif