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, 454 insertions, 0 deletions

diff --git a/include/net/ndisc.h b/include/net/ndisc.h
new file mode 100644
index 000000000..3da1a6f8d
--- /dev/null
+++ b/include/net/ndisc.h
@@ -0,0 +1,454 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _NDISC_H
+#define _NDISC_H
+
+/*
+ *	ICMP codes for neighbour discovery messages
+ */
+
+#define NDISC_ROUTER_SOLICITATION	133
+#define NDISC_ROUTER_ADVERTISEMENT	134
+#define NDISC_NEIGHBOUR_SOLICITATION	135
+#define NDISC_NEIGHBOUR_ADVERTISEMENT	136
+#define NDISC_REDIRECT			137
+
+/*
+ * Router type: cross-layer information from link-layer to
+ * IPv6 layer reported by certain link types (e.g., RFC4214).
+ */
+#define NDISC_NODETYPE_UNSPEC		0	/* unspecified (default) */
+#define NDISC_NODETYPE_HOST		1	/* host or unauthorized router */
+#define NDISC_NODETYPE_NODEFAULT	2	/* non-default router */
+#define NDISC_NODETYPE_DEFAULT		3	/* default router */
+
+/*
+ *	ndisc options
+ */
+
+enum {
+	__ND_OPT_PREFIX_INFO_END = 0,
+	ND_OPT_SOURCE_LL_ADDR = 1,	/* RFC2461 */
+	ND_OPT_TARGET_LL_ADDR = 2,	/* RFC2461 */
+	ND_OPT_PREFIX_INFO = 3,		/* RFC2461 */
+	ND_OPT_REDIRECT_HDR = 4,	/* RFC2461 */
+	ND_OPT_MTU = 5,			/* RFC2461 */
+	ND_OPT_NONCE = 14,              /* RFC7527 */
+	__ND_OPT_ARRAY_MAX,
+	ND_OPT_ROUTE_INFO = 24,		/* RFC4191 */
+	ND_OPT_RDNSS = 25,		/* RFC5006 */
+	ND_OPT_DNSSL = 31,		/* RFC6106 */
+	ND_OPT_6CO = 34,		/* RFC6775 */
+	ND_OPT_CAPTIVE_PORTAL = 37,	/* RFC7710 */
+	ND_OPT_PREF64 = 38,		/* RFC8781 */
+	__ND_OPT_MAX
+};
+
+#define MAX_RTR_SOLICITATION_DELAY	HZ
+
+#define ND_REACHABLE_TIME		(30*HZ)
+#define ND_RETRANS_TIMER		HZ
+
+#include <linux/compiler.h>
+#include <linux/icmpv6.h>
+#include <linux/in6.h>
+#include <linux/types.h>
+#include <linux/if_arp.h>
+#include <linux/netdevice.h>
+#include <linux/hash.h>
+
+#include <net/neighbour.h>
+
+struct ctl_table;
+struct inet6_dev;
+struct net_device;
+struct net_proto_family;
+struct sk_buff;
+struct prefix_info;
+
+extern struct neigh_table nd_tbl;
+
+struct nd_msg {
+        struct icmp6hdr	icmph;
+        struct in6_addr	target;
+	__u8		opt[];
+};
+
+struct rs_msg {
+	struct icmp6hdr	icmph;
+	__u8		opt[];
+};
+
+struct ra_msg {
+        struct icmp6hdr		icmph;
+	__be32			reachable_time;
+	__be32			retrans_timer;
+};
+
+struct rd_msg {
+	struct icmp6hdr icmph;
+	struct in6_addr	target;
+	struct in6_addr	dest;
+	__u8		opt[];
+};
+
+struct nd_opt_hdr {
+	__u8		nd_opt_type;
+	__u8		nd_opt_len;
+} __packed;
+
+/* ND options */
+struct ndisc_options {
+	struct nd_opt_hdr *nd_opt_array[__ND_OPT_ARRAY_MAX];
+#ifdef CONFIG_IPV6_ROUTE_INFO
+	struct nd_opt_hdr *nd_opts_ri;
+	struct nd_opt_hdr *nd_opts_ri_end;
+#endif
+	struct nd_opt_hdr *nd_useropts;
+	struct nd_opt_hdr *nd_useropts_end;
+#if IS_ENABLED(CONFIG_IEEE802154_6LOWPAN)
+	struct nd_opt_hdr *nd_802154_opt_array[ND_OPT_TARGET_LL_ADDR + 1];
+#endif
+};
+
+#define nd_opts_src_lladdr		nd_opt_array[ND_OPT_SOURCE_LL_ADDR]
+#define nd_opts_tgt_lladdr		nd_opt_array[ND_OPT_TARGET_LL_ADDR]
+#define nd_opts_pi			nd_opt_array[ND_OPT_PREFIX_INFO]
+#define nd_opts_pi_end			nd_opt_array[__ND_OPT_PREFIX_INFO_END]
+#define nd_opts_rh			nd_opt_array[ND_OPT_REDIRECT_HDR]
+#define nd_opts_mtu			nd_opt_array[ND_OPT_MTU]
+#define nd_opts_nonce			nd_opt_array[ND_OPT_NONCE]
+#define nd_802154_opts_src_lladdr	nd_802154_opt_array[ND_OPT_SOURCE_LL_ADDR]
+#define nd_802154_opts_tgt_lladdr	nd_802154_opt_array[ND_OPT_TARGET_LL_ADDR]
+
+#define NDISC_OPT_SPACE(len) (((len)+2+7)&~7)
+
+struct ndisc_options *ndisc_parse_options(const struct net_device *dev,
+					  u8 *opt, int opt_len,
+					  struct ndisc_options *ndopts);
+
+void __ndisc_fill_addr_option(struct sk_buff *skb, int type, const void *data,
+			      int data_len, int pad);
+
+#define NDISC_OPS_REDIRECT_DATA_SPACE	2
+
+/*
+ * This structure defines the hooks for IPv6 neighbour discovery.
+ * The following hooks can be defined; unless noted otherwise, they are
+ * optional and can be filled with a null pointer.
+ *
+ * int (*parse_options)(const struct net_device *dev,
+ *			struct nd_opt_hdr *nd_opt,
+ *			struct ndisc_options *ndopts):
+ *     This function is called while parsing ndisc ops and put each position
+ *     as pointer into ndopts. If this function return unequal 0, then this
+ *     function took care about the ndisc option, if 0 then the IPv6 ndisc
+ *     option parser will take care about that option.
+ *
+ * void (*update)(const struct net_device *dev, struct neighbour *n,
+ *		  u32 flags, u8 icmp6_type,
+ *		  const struct ndisc_options *ndopts):
+ *     This function is called when IPv6 ndisc updates the neighbour cache
+ *     entry. Additional options which can be updated may be previously
+ *     parsed by parse_opts callback and accessible over ndopts parameter.
+ *
+ * int (*opt_addr_space)(const struct net_device *dev, u8 icmp6_type,
+ *			 struct neighbour *neigh, u8 *ha_buf,
+ *			 u8 **ha):
+ *     This function is called when the necessary option space will be
+ *     calculated before allocating a skb. The parameters neigh, ha_buf
+ *     abd ha are available on NDISC_REDIRECT messages only.
+ *
+ * void (*fill_addr_option)(const struct net_device *dev,
+ *			    struct sk_buff *skb, u8 icmp6_type,
+ *			    const u8 *ha):
+ *     This function is called when the skb will finally fill the option
+ *     fields inside skb. NOTE: this callback should fill the option
+ *     fields to the skb which are previously indicated by opt_space
+ *     parameter. That means the decision to add such option should
+ *     not lost between these two callbacks, e.g. protected by interface
+ *     up state.
+ *
+ * void (*prefix_rcv_add_addr)(struct net *net, struct net_device *dev,
+ *			       const struct prefix_info *pinfo,
+ *			       struct inet6_dev *in6_dev,
+ *			       struct in6_addr *addr,
+ *			       int addr_type, u32 addr_flags,
+ *			       bool sllao, bool tokenized,
+ *			       __u32 valid_lft, u32 prefered_lft,
+ *			       bool dev_addr_generated):
+ *     This function is called when a RA messages is received with valid
+ *     PIO option fields and an IPv6 address will be added to the interface
+ *     for autoconfiguration. The parameter dev_addr_generated reports about
+ *     if the address was based on dev->dev_addr or not. This can be used
+ *     to add a second address if link-layer operates with two link layer
+ *     addresses. E.g. 802.15.4 6LoWPAN.
+ */
+struct ndisc_ops {
+	int	(*parse_options)(const struct net_device *dev,
+				 struct nd_opt_hdr *nd_opt,
+				 struct ndisc_options *ndopts);
+	void	(*update)(const struct net_device *dev, struct neighbour *n,
+			  u32 flags, u8 icmp6_type,
+			  const struct ndisc_options *ndopts);
+	int	(*opt_addr_space)(const struct net_device *dev, u8 icmp6_type,
+				  struct neighbour *neigh, u8 *ha_buf,
+				  u8 **ha);
+	void	(*fill_addr_option)(const struct net_device *dev,
+				    struct sk_buff *skb, u8 icmp6_type,
+				    const u8 *ha);
+	void	(*prefix_rcv_add_addr)(struct net *net, struct net_device *dev,
+				       const struct prefix_info *pinfo,
+				       struct inet6_dev *in6_dev,
+				       struct in6_addr *addr,
+				       int addr_type, u32 addr_flags,
+				       bool sllao, bool tokenized,
+				       __u32 valid_lft, u32 prefered_lft,
+				       bool dev_addr_generated);
+};
+
+#if IS_ENABLED(CONFIG_IPV6)
+static inline int ndisc_ops_parse_options(const struct net_device *dev,
+					  struct nd_opt_hdr *nd_opt,
+					  struct ndisc_options *ndopts)
+{
+	if (dev->ndisc_ops && dev->ndisc_ops->parse_options)
+		return dev->ndisc_ops->parse_options(dev, nd_opt, ndopts);
+	else
+		return 0;
+}
+
+static inline void ndisc_ops_update(const struct net_device *dev,
+					  struct neighbour *n, u32 flags,
+					  u8 icmp6_type,
+					  const struct ndisc_options *ndopts)
+{
+	if (dev->ndisc_ops && dev->ndisc_ops->update)
+		dev->ndisc_ops->update(dev, n, flags, icmp6_type, ndopts);
+}
+
+static inline int ndisc_ops_opt_addr_space(const struct net_device *dev,
+					   u8 icmp6_type)
+{
+	if (dev->ndisc_ops && dev->ndisc_ops->opt_addr_space &&
+	    icmp6_type != NDISC_REDIRECT)
+		return dev->ndisc_ops->opt_addr_space(dev, icmp6_type, NULL,
+						      NULL, NULL);
+	else
+		return 0;
+}
+
+static inline int ndisc_ops_redirect_opt_addr_space(const struct net_device *dev,
+						    struct neighbour *neigh,
+						    u8 *ha_buf, u8 **ha)
+{
+	if (dev->ndisc_ops && dev->ndisc_ops->opt_addr_space)
+		return dev->ndisc_ops->opt_addr_space(dev, NDISC_REDIRECT,
+						      neigh, ha_buf, ha);
+	else
+		return 0;
+}
+
+static inline void ndisc_ops_fill_addr_option(const struct net_device *dev,
+					      struct sk_buff *skb,
+					      u8 icmp6_type)
+{
+	if (dev->ndisc_ops && dev->ndisc_ops->fill_addr_option &&
+	    icmp6_type != NDISC_REDIRECT)
+		dev->ndisc_ops->fill_addr_option(dev, skb, icmp6_type, NULL);
+}
+
+static inline void ndisc_ops_fill_redirect_addr_option(const struct net_device *dev,
+						       struct sk_buff *skb,
+						       const u8 *ha)
+{
+	if (dev->ndisc_ops && dev->ndisc_ops->fill_addr_option)
+		dev->ndisc_ops->fill_addr_option(dev, skb, NDISC_REDIRECT, ha);
+}
+
+static inline void ndisc_ops_prefix_rcv_add_addr(struct net *net,
+						 struct net_device *dev,
+						 const struct prefix_info *pinfo,
+						 struct inet6_dev *in6_dev,
+						 struct in6_addr *addr,
+						 int addr_type, u32 addr_flags,
+						 bool sllao, bool tokenized,
+						 __u32 valid_lft,
+						 u32 prefered_lft,
+						 bool dev_addr_generated)
+{
+	if (dev->ndisc_ops && dev->ndisc_ops->prefix_rcv_add_addr)
+		dev->ndisc_ops->prefix_rcv_add_addr(net, dev, pinfo, in6_dev,
+						    addr, addr_type,
+						    addr_flags, sllao,
+						    tokenized, valid_lft,
+						    prefered_lft,
+						    dev_addr_generated);
+}
+#endif
+
+/*
+ * Return the padding between the option length and the start of the
+ * link addr.  Currently only IP-over-InfiniBand needs this, although
+ * if RFC 3831 IPv6-over-Fibre Channel is ever implemented it may
+ * also need a pad of 2.
+ */
+static inline int ndisc_addr_option_pad(unsigned short type)
+{
+	switch (type) {
+	case ARPHRD_INFINIBAND: return 2;
+	default:                return 0;
+	}
+}
+
+static inline int __ndisc_opt_addr_space(unsigned char addr_len, int pad)
+{
+	return NDISC_OPT_SPACE(addr_len + pad);
+}
+
+#if IS_ENABLED(CONFIG_IPV6)
+static inline int ndisc_opt_addr_space(struct net_device *dev, u8 icmp6_type)
+{
+	return __ndisc_opt_addr_space(dev->addr_len,
+				      ndisc_addr_option_pad(dev->type)) +
+		ndisc_ops_opt_addr_space(dev, icmp6_type);
+}
+
+static inline int ndisc_redirect_opt_addr_space(struct net_device *dev,
+						struct neighbour *neigh,
+						u8 *ops_data_buf,
+						u8 **ops_data)
+{
+	return __ndisc_opt_addr_space(dev->addr_len,
+				      ndisc_addr_option_pad(dev->type)) +
+		ndisc_ops_redirect_opt_addr_space(dev, neigh, ops_data_buf,
+						  ops_data);
+}
+#endif
+
+static inline u8 *__ndisc_opt_addr_data(struct nd_opt_hdr *p,
+					unsigned char addr_len, int prepad)
+{
+	u8 *lladdr = (u8 *)(p + 1);
+	int lladdrlen = p->nd_opt_len << 3;
+	if (lladdrlen != __ndisc_opt_addr_space(addr_len, prepad))
+		return NULL;
+	return lladdr + prepad;
+}
+
+static inline u8 *ndisc_opt_addr_data(struct nd_opt_hdr *p,
+				      struct net_device *dev)
+{
+	return __ndisc_opt_addr_data(p, dev->addr_len,
+				     ndisc_addr_option_pad(dev->type));
+}
+
+static inline u32 ndisc_hashfn(const void *pkey, const struct net_device *dev, __u32 *hash_rnd)
+{
+	const u32 *p32 = pkey;
+
+	return (((p32[0] ^ hash32_ptr(dev)) * hash_rnd[0]) +
+		(p32[1] * hash_rnd[1]) +
+		(p32[2] * hash_rnd[2]) +
+		(p32[3] * hash_rnd[3]));
+}
+
+static inline struct neighbour *__ipv6_neigh_lookup_noref(struct net_device *dev, const void *pkey)
+{
+	return ___neigh_lookup_noref(&nd_tbl, neigh_key_eq128, ndisc_hashfn, pkey, dev);
+}
+
+static inline struct neighbour *__ipv6_neigh_lookup(struct net_device *dev, const void *pkey)
+{
+	struct neighbour *n;
+
+	rcu_read_lock();
+	n = __ipv6_neigh_lookup_noref(dev, pkey);
+	if (n && !refcount_inc_not_zero(&n->refcnt))
+		n = NULL;
+	rcu_read_unlock();
+
+	return n;
+}
+
+static inline void __ipv6_confirm_neigh(struct net_device *dev,
+					const void *pkey)
+{
+	struct neighbour *n;
+
+	rcu_read_lock();
+	n = __ipv6_neigh_lookup_noref(dev, pkey);
+	neigh_confirm(n);
+	rcu_read_unlock();
+}
+
+static inline struct neighbour *ip_neigh_gw6(struct net_device *dev,
+					     const void *addr)
+{
+#if IS_ENABLED(CONFIG_IPV6)
+	struct neighbour *neigh;
+
+	neigh = __ipv6_neigh_lookup_noref(dev, addr);
+	if (unlikely(!neigh))
+		neigh = __neigh_create(&nd_tbl, addr, dev, false);
+
+	return neigh;
+#else
+	return ERR_PTR(-EAFNOSUPPORT);
+#endif
+}
+
+int ndisc_init(void);
+int ndisc_late_init(void);
+
+void ndisc_late_cleanup(void);
+void ndisc_cleanup(void);
+
+enum skb_drop_reason ndisc_rcv(struct sk_buff *skb);
+
+struct sk_buff *ndisc_ns_create(struct net_device *dev, const struct in6_addr *solicit,
+				const struct in6_addr *saddr, u64 nonce);
+void ndisc_send_ns(struct net_device *dev, const struct in6_addr *solicit,
+		   const struct in6_addr *daddr, const struct in6_addr *saddr,
+		   u64 nonce);
+
+void ndisc_send_skb(struct sk_buff *skb, const struct in6_addr *daddr,
+		    const struct in6_addr *saddr);
+
+void ndisc_send_rs(struct net_device *dev,
+		   const struct in6_addr *saddr, const struct in6_addr *daddr);
+
+void ndisc_send_na(struct net_device *dev, const struct in6_addr *daddr,
+		   const struct in6_addr *solicited_addr,
+		   bool router, bool solicited, bool override, bool inc_opt);
+
+void ndisc_send_redirect(struct sk_buff *skb, const struct in6_addr *target);
+
+int ndisc_mc_map(const struct in6_addr *addr, char *buf, struct net_device *dev,
+		 int dir);
+
+void ndisc_update(const struct net_device *dev, struct neighbour *neigh,
+		  const u8 *lladdr, u8 new, u32 flags, u8 icmp6_type,
+		  struct ndisc_options *ndopts);
+
+/*
+ *	IGMP
+ */
+int igmp6_init(void);
+int igmp6_late_init(void);
+
+void igmp6_cleanup(void);
+void igmp6_late_cleanup(void);
+
+void igmp6_event_query(struct sk_buff *skb);
+
+void igmp6_event_report(struct sk_buff *skb);
+
+
+#ifdef CONFIG_SYSCTL
+int ndisc_ifinfo_sysctl_change(const struct ctl_table *ctl, int write,
+			       void *buffer, size_t *lenp, loff_t *ppos);
+#endif
+
+void inet6_ifinfo_notify(int event, struct inet6_dev *idev);
+
+#endif