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, 210 insertions, 0 deletions

diff --git a/drivers/net/ipvlan/ipvlan.h b/drivers/net/ipvlan/ipvlan.h
new file mode 100644
index 000000000..80f84fc87
--- /dev/null
+++ b/drivers/net/ipvlan/ipvlan.h
@@ -0,0 +1,210 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (c) 2014 Mahesh Bandewar <maheshb@google.com>
+ */
+#ifndef __IPVLAN_H
+#define __IPVLAN_H
+
+#include <linux/kernel.h>
+#include <linux/types.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/rculist.h>
+#include <linux/notifier.h>
+#include <linux/netdevice.h>
+#include <linux/etherdevice.h>
+#include <linux/if_arp.h>
+#include <linux/if_link.h>
+#include <linux/if_vlan.h>
+#include <linux/ip.h>
+#include <linux/inetdevice.h>
+#include <linux/netfilter.h>
+#include <net/ip.h>
+#include <net/ip6_route.h>
+#include <net/netns/generic.h>
+#include <net/rtnetlink.h>
+#include <net/route.h>
+#include <net/addrconf.h>
+#include <net/l3mdev.h>
+
+#define IPVLAN_DRV	"ipvlan"
+#define IPV_DRV_VER	"0.1"
+
+#define IPVLAN_HASH_SIZE	(1 << BITS_PER_BYTE)
+#define IPVLAN_HASH_MASK	(IPVLAN_HASH_SIZE - 1)
+
+#define IPVLAN_MAC_FILTER_BITS	8
+#define IPVLAN_MAC_FILTER_SIZE	(1 << IPVLAN_MAC_FILTER_BITS)
+#define IPVLAN_MAC_FILTER_MASK	(IPVLAN_MAC_FILTER_SIZE - 1)
+
+#define IPVLAN_QBACKLOG_LIMIT	1000
+
+typedef enum {
+	IPVL_IPV6 = 0,
+	IPVL_ICMPV6,
+	IPVL_IPV4,
+	IPVL_ARP,
+} ipvl_hdr_type;
+
+struct ipvl_pcpu_stats {
+	u64_stats_t		rx_pkts;
+	u64_stats_t		rx_bytes;
+	u64_stats_t		rx_mcast;
+	u64_stats_t		tx_pkts;
+	u64_stats_t		tx_bytes;
+	struct u64_stats_sync	syncp;
+	u32			rx_errs;
+	u32			tx_drps;
+};
+
+struct ipvl_port;
+
+struct ipvl_dev {
+	struct net_device	*dev;
+	struct list_head	pnode;
+	struct ipvl_port	*port;
+	struct net_device	*phy_dev;
+	struct list_head	addrs;
+	struct ipvl_pcpu_stats	__percpu *pcpu_stats;
+	DECLARE_BITMAP(mac_filters, IPVLAN_MAC_FILTER_SIZE);
+	netdev_features_t	sfeatures;
+	u32			msg_enable;
+};
+
+struct ipvl_addr {
+	struct ipvl_dev		*master; /* Back pointer to master */
+	union {
+		struct in6_addr	ip6;	 /* IPv6 address on logical interface */
+		struct in_addr	ip4;	 /* IPv4 address on logical interface */
+	} ipu;
+#define ip6addr	ipu.ip6
+#define ip4addr ipu.ip4
+	struct hlist_node	hlnode;  /* Hash-table linkage */
+	struct list_head	anode;   /* logical-interface linkage */
+	ipvl_hdr_type		atype;
+	struct rcu_head		rcu;
+};
+
+struct ipvl_port {
+	struct net_device	*dev;
+	possible_net_t		pnet;
+	struct hlist_head	hlhead[IPVLAN_HASH_SIZE];
+	spinlock_t		addrs_lock; /* guards hash-table and addrs */
+	struct list_head	ipvlans;
+	u16			mode;
+	u16			flags;
+	u16			dev_id_start;
+	struct work_struct	wq;
+	struct sk_buff_head	backlog;
+	int			count;
+	struct ida		ida;
+	netdevice_tracker	dev_tracker;
+};
+
+struct ipvl_skb_cb {
+	bool tx_pkt;
+};
+#define IPVL_SKB_CB(_skb) ((struct ipvl_skb_cb *)&((_skb)->cb[0]))
+
+static inline struct ipvl_port *ipvlan_port_get_rcu(const struct net_device *d)
+{
+	return rcu_dereference(d->rx_handler_data);
+}
+
+static inline struct ipvl_port *ipvlan_port_get_rcu_bh(const struct net_device *d)
+{
+	return rcu_dereference_bh(d->rx_handler_data);
+}
+
+static inline struct ipvl_port *ipvlan_port_get_rtnl(const struct net_device *d)
+{
+	return rtnl_dereference(d->rx_handler_data);
+}
+
+static inline bool ipvlan_is_private(const struct ipvl_port *port)
+{
+	return !!(port->flags & IPVLAN_F_PRIVATE);
+}
+
+static inline void ipvlan_mark_private(struct ipvl_port *port)
+{
+	port->flags |= IPVLAN_F_PRIVATE;
+}
+
+static inline void ipvlan_clear_private(struct ipvl_port *port)
+{
+	port->flags &= ~IPVLAN_F_PRIVATE;
+}
+
+static inline bool ipvlan_is_vepa(const struct ipvl_port *port)
+{
+	return !!(port->flags & IPVLAN_F_VEPA);
+}
+
+static inline void ipvlan_mark_vepa(struct ipvl_port *port)
+{
+	port->flags |= IPVLAN_F_VEPA;
+}
+
+static inline void ipvlan_clear_vepa(struct ipvl_port *port)
+{
+	port->flags &= ~IPVLAN_F_VEPA;
+}
+
+void ipvlan_init_secret(void);
+unsigned int ipvlan_mac_hash(const unsigned char *addr);
+rx_handler_result_t ipvlan_handle_frame(struct sk_buff **pskb);
+void ipvlan_process_multicast(struct work_struct *work);
+int ipvlan_queue_xmit(struct sk_buff *skb, struct net_device *dev);
+void ipvlan_ht_addr_add(struct ipvl_dev *ipvlan, struct ipvl_addr *addr);
+struct ipvl_addr *ipvlan_find_addr(const struct ipvl_dev *ipvlan,
+				   const void *iaddr, bool is_v6);
+bool ipvlan_addr_busy(struct ipvl_port *port, void *iaddr, bool is_v6);
+void ipvlan_ht_addr_del(struct ipvl_addr *addr);
+struct ipvl_addr *ipvlan_addr_lookup(struct ipvl_port *port, void *lyr3h,
+				     int addr_type, bool use_dest);
+void *ipvlan_get_L3_hdr(struct ipvl_port *port, struct sk_buff *skb, int *type);
+void ipvlan_count_rx(const struct ipvl_dev *ipvlan,
+		     unsigned int len, bool success, bool mcast);
+int ipvlan_link_new(struct net_device *dev, struct rtnl_newlink_params *params,
+		    struct netlink_ext_ack *extack);
+void ipvlan_link_delete(struct net_device *dev, struct list_head *head);
+void ipvlan_link_setup(struct net_device *dev);
+int ipvlan_link_register(struct rtnl_link_ops *ops);
+#ifdef CONFIG_IPVLAN_L3S
+int ipvlan_l3s_register(struct ipvl_port *port);
+void ipvlan_l3s_unregister(struct ipvl_port *port);
+void ipvlan_migrate_l3s_hook(struct net *oldnet, struct net *newnet);
+int ipvlan_l3s_init(void);
+void ipvlan_l3s_cleanup(void);
+#else
+static inline int ipvlan_l3s_register(struct ipvl_port *port)
+{
+	return -ENOTSUPP;
+}
+
+static inline void ipvlan_l3s_unregister(struct ipvl_port *port)
+{
+}
+
+static inline void ipvlan_migrate_l3s_hook(struct net *oldnet,
+					   struct net *newnet)
+{
+}
+
+static inline int ipvlan_l3s_init(void)
+{
+	return 0;
+}
+
+static inline void ipvlan_l3s_cleanup(void)
+{
+}
+#endif /* CONFIG_IPVLAN_L3S */
+
+static inline bool netif_is_ipvlan_port(const struct net_device *dev)
+{
+	return rcu_access_pointer(dev->rx_handler) == ipvlan_handle_frame;
+}
+
+#endif /* __IPVLAN_H */