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, 170 insertions, 0 deletions

diff --git a/include/net/bond_options.h b/include/net/bond_options.h
new file mode 100644
index 000000000..52b966e92
--- /dev/null
+++ b/include/net/bond_options.h
@@ -0,0 +1,170 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * drivers/net/bond/bond_options.h - bonding options
+ * Copyright (c) 2013 Nikolay Aleksandrov <nikolay@redhat.com>
+ */
+
+#ifndef _NET_BOND_OPTIONS_H
+#define _NET_BOND_OPTIONS_H
+
+#include <linux/bits.h>
+#include <linux/limits.h>
+#include <linux/types.h>
+#include <linux/string.h>
+
+struct netlink_ext_ack;
+struct nlattr;
+
+#define BOND_OPT_MAX_NAMELEN 32
+#define BOND_OPT_VALID(opt) ((opt) < BOND_OPT_LAST)
+#define BOND_MODE_ALL_EX(x) (~(x))
+
+/* Option flags:
+ * BOND_OPTFLAG_NOSLAVES - check if the bond device is empty before setting
+ * BOND_OPTFLAG_IFDOWN - check if the bond device is down before setting
+ * BOND_OPTFLAG_RAWVAL - the option parses the value itself
+ */
+enum {
+	BOND_OPTFLAG_NOSLAVES	= BIT(0),
+	BOND_OPTFLAG_IFDOWN	= BIT(1),
+	BOND_OPTFLAG_RAWVAL	= BIT(2)
+};
+
+/* Value type flags:
+ * BOND_VALFLAG_DEFAULT - mark the value as default
+ * BOND_VALFLAG_(MIN|MAX) - mark the value as min/max
+ */
+enum {
+	BOND_VALFLAG_DEFAULT	= BIT(0),
+	BOND_VALFLAG_MIN	= BIT(1),
+	BOND_VALFLAG_MAX	= BIT(2)
+};
+
+/* Option IDs, their bit positions correspond to their IDs */
+enum {
+	BOND_OPT_MODE,
+	BOND_OPT_PACKETS_PER_SLAVE,
+	BOND_OPT_XMIT_HASH,
+	BOND_OPT_ARP_VALIDATE,
+	BOND_OPT_ARP_ALL_TARGETS,
+	BOND_OPT_FAIL_OVER_MAC,
+	BOND_OPT_ARP_INTERVAL,
+	BOND_OPT_ARP_TARGETS,
+	BOND_OPT_DOWNDELAY,
+	BOND_OPT_UPDELAY,
+	BOND_OPT_LACP_RATE,
+	BOND_OPT_MINLINKS,
+	BOND_OPT_AD_SELECT,
+	BOND_OPT_NUM_PEER_NOTIF,
+	BOND_OPT_MIIMON,
+	BOND_OPT_PRIMARY,
+	BOND_OPT_PRIMARY_RESELECT,
+	BOND_OPT_USE_CARRIER,
+	BOND_OPT_ACTIVE_SLAVE,
+	BOND_OPT_QUEUE_ID,
+	BOND_OPT_ALL_SLAVES_ACTIVE,
+	BOND_OPT_RESEND_IGMP,
+	BOND_OPT_LP_INTERVAL,
+	BOND_OPT_SLAVES,
+	BOND_OPT_TLB_DYNAMIC_LB,
+	BOND_OPT_AD_ACTOR_SYS_PRIO,
+	BOND_OPT_AD_ACTOR_SYSTEM,
+	BOND_OPT_AD_USER_PORT_KEY,
+	BOND_OPT_NUM_PEER_NOTIF_ALIAS,
+	BOND_OPT_PEER_NOTIF_DELAY,
+	BOND_OPT_LACP_ACTIVE,
+	BOND_OPT_MISSED_MAX,
+	BOND_OPT_NS_TARGETS,
+	BOND_OPT_PRIO,
+	BOND_OPT_COUPLED_CONTROL,
+	BOND_OPT_BROADCAST_NEIGH,
+	BOND_OPT_ACTOR_PORT_PRIO,
+	BOND_OPT_LACP_STRICT,
+	BOND_OPT_LAST
+};
+
+/* This structure is used for storing option values and for passing option
+ * values when changing an option. The logic when used as an arg is as follows:
+ * - if value != ULLONG_MAX -> parse value
+ * - if string != NULL -> parse string
+ * - if the opt is RAW data and length less than maxlen,
+ *   copy the data to extra storage
+ */
+
+#define BOND_OPT_EXTRA_MAXLEN 16
+struct bond_opt_value {
+	char *string;
+	u64 value;
+	u32 flags;
+	union {
+		char extra[BOND_OPT_EXTRA_MAXLEN];
+		struct net_device *slave_dev;
+	};
+};
+
+struct bonding;
+
+struct bond_option {
+	int id;
+	const char *name;
+	const char *desc;
+	u32 flags;
+
+	/* unsuppmodes is used to denote modes in which the option isn't
+	 * supported.
+	 */
+	unsigned long unsuppmodes;
+	/* supported values which this option can have, can be a subset of
+	 * BOND_OPTVAL_RANGE's value range
+	 */
+	const struct bond_opt_value *values;
+
+	int (*set)(struct bonding *bond, const struct bond_opt_value *val);
+};
+
+int __bond_opt_set(struct bonding *bond, unsigned int option,
+		   struct bond_opt_value *val,
+		   struct nlattr *bad_attr, struct netlink_ext_ack *extack);
+int __bond_opt_set_notify(struct bonding *bond, unsigned int option,
+			  struct bond_opt_value *val);
+int bond_opt_tryset_rtnl(struct bonding *bond, unsigned int option, char *buf);
+
+const struct bond_opt_value *bond_opt_parse(const struct bond_option *opt,
+					    struct bond_opt_value *val);
+const struct bond_option *bond_opt_get(unsigned int option);
+const struct bond_option *bond_opt_get_by_name(const char *name);
+const struct bond_opt_value *bond_opt_get_val(unsigned int option, u64 val);
+
+/* This helper is used to initialize a bond_opt_value structure for parameter
+ * passing. There should be either a valid string or value, but not both.
+ * When value is ULLONG_MAX then string will be used.
+ */
+static inline void __bond_opt_init(struct bond_opt_value *optval,
+				   char *string, u64 value,
+				   void *extra, size_t extra_len)
+{
+	memset(optval, 0, sizeof(*optval));
+	optval->value = ULLONG_MAX;
+	if (value != ULLONG_MAX)
+		optval->value = value;
+	else if (string)
+		optval->string = string;
+
+	if (extra && extra_len <= BOND_OPT_EXTRA_MAXLEN)
+		memcpy(optval->extra, extra, extra_len);
+}
+#define bond_opt_initval(optval, value) __bond_opt_init(optval, NULL, value, NULL, 0)
+#define bond_opt_initstr(optval, str) __bond_opt_init(optval, str, ULLONG_MAX, NULL, 0)
+#define bond_opt_initextra(optval, extra, extra_len) \
+	__bond_opt_init(optval, NULL, ULLONG_MAX, extra, extra_len)
+#define bond_opt_slave_initval(optval, slave_dev, value) \
+	__bond_opt_init(optval, NULL, value, slave_dev, sizeof(struct net_device *))
+
+void bond_option_arp_ip_targets_clear(struct bonding *bond);
+#if IS_ENABLED(CONFIG_IPV6)
+void bond_option_ns_ip6_targets_clear(struct bonding *bond);
+#endif
+void bond_slave_ns_maddrs_add(struct bonding *bond, struct slave *slave);
+void bond_slave_ns_maddrs_del(struct bonding *bond, struct slave *slave);
+
+#endif /* _NET_BOND_OPTIONS_H */