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, 465 insertions, 0 deletions

diff --git a/net/sched/act_vlan.c b/net/sched/act_vlan.c
new file mode 100644
index 000000000..6a375fdc6
--- /dev/null
+++ b/net/sched/act_vlan.c
@@ -0,0 +1,465 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2014 Jiri Pirko <jiri@resnulli.us>
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/skbuff.h>
+#include <linux/rtnetlink.h>
+#include <linux/if_vlan.h>
+#include <net/netlink.h>
+#include <net/pkt_sched.h>
+#include <net/pkt_cls.h>
+#include <net/tc_wrapper.h>
+
+#include <linux/tc_act/tc_vlan.h>
+#include <net/tc_act/tc_vlan.h>
+
+static struct tc_action_ops act_vlan_ops;
+
+TC_INDIRECT_SCOPE int tcf_vlan_act(struct sk_buff *skb,
+				   const struct tc_action *a,
+				   struct tcf_result *res)
+{
+	struct tcf_vlan *v = to_vlan(a);
+	struct tcf_vlan_params *p;
+	int err;
+	u16 tci;
+
+	tcf_lastuse_update(&v->tcf_tm);
+	tcf_action_update_bstats(&v->common, skb);
+
+	/* Ensure 'data' points at mac_header prior calling vlan manipulating
+	 * functions.
+	 */
+	if (skb_at_tc_ingress(skb))
+		skb_push_rcsum(skb, skb->mac_len);
+
+	p = rcu_dereference_bh(v->vlan_p);
+
+	switch (p->tcfv_action) {
+	case TCA_VLAN_ACT_POP:
+		err = skb_vlan_pop(skb);
+		if (err)
+			goto drop;
+		break;
+	case TCA_VLAN_ACT_PUSH:
+		err = skb_vlan_push(skb, p->tcfv_push_proto, p->tcfv_push_vid |
+				    (p->tcfv_push_prio << VLAN_PRIO_SHIFT));
+		if (err)
+			goto drop;
+		break;
+	case TCA_VLAN_ACT_MODIFY:
+		/* No-op if no vlan tag (either hw-accel or in-payload) */
+		if (!skb_vlan_tagged(skb))
+			goto out;
+		/* extract existing tag (and guarantee no hw-accel tag) */
+		if (skb_vlan_tag_present(skb)) {
+			tci = skb_vlan_tag_get(skb);
+			__vlan_hwaccel_clear_tag(skb);
+		} else {
+			/* in-payload vlan tag, pop it */
+			err = __skb_vlan_pop(skb, &tci);
+			if (err)
+				goto drop;
+		}
+		/* replace the vid */
+		tci = (tci & ~VLAN_VID_MASK) | p->tcfv_push_vid;
+		/* replace prio bits, if tcfv_push_prio specified */
+		if (p->tcfv_push_prio_exists) {
+			tci &= ~VLAN_PRIO_MASK;
+			tci |= p->tcfv_push_prio << VLAN_PRIO_SHIFT;
+		}
+		/* put updated tci as hwaccel tag */
+		__vlan_hwaccel_put_tag(skb, p->tcfv_push_proto, tci);
+		break;
+	case TCA_VLAN_ACT_POP_ETH:
+		err = skb_eth_pop(skb);
+		if (err)
+			goto drop;
+		break;
+	case TCA_VLAN_ACT_PUSH_ETH:
+		err = skb_eth_push(skb, p->tcfv_push_dst, p->tcfv_push_src);
+		if (err)
+			goto drop;
+		break;
+	default:
+		BUG();
+	}
+
+out:
+	if (skb_at_tc_ingress(skb))
+		skb_pull_rcsum(skb, skb->mac_len);
+
+	skb_reset_mac_len(skb);
+	return p->action;
+
+drop:
+	tcf_action_inc_drop_qstats(&v->common);
+	return TC_ACT_SHOT;
+}
+
+static const struct nla_policy vlan_policy[TCA_VLAN_MAX + 1] = {
+	[TCA_VLAN_UNSPEC]		= { .strict_start_type = TCA_VLAN_PUSH_ETH_DST },
+	[TCA_VLAN_PARMS]		= { .len = sizeof(struct tc_vlan) },
+	[TCA_VLAN_PUSH_VLAN_ID]		= { .type = NLA_U16 },
+	[TCA_VLAN_PUSH_VLAN_PROTOCOL]	= { .type = NLA_U16 },
+	[TCA_VLAN_PUSH_VLAN_PRIORITY]	= { .type = NLA_U8 },
+	[TCA_VLAN_PUSH_ETH_DST]		= NLA_POLICY_ETH_ADDR,
+	[TCA_VLAN_PUSH_ETH_SRC]		= NLA_POLICY_ETH_ADDR,
+};
+
+static int tcf_vlan_init(struct net *net, struct nlattr *nla,
+			 struct nlattr *est, struct tc_action **a,
+			 struct tcf_proto *tp, u32 flags,
+			 struct netlink_ext_ack *extack)
+{
+	struct tc_action_net *tn = net_generic(net, act_vlan_ops.net_id);
+	bool bind = flags & TCA_ACT_FLAGS_BIND;
+	struct nlattr *tb[TCA_VLAN_MAX + 1];
+	struct tcf_chain *goto_ch = NULL;
+	bool push_prio_exists = false;
+	struct tcf_vlan_params *p;
+	struct tc_vlan *parm;
+	struct tcf_vlan *v;
+	int action;
+	u16 push_vid = 0;
+	__be16 push_proto = 0;
+	u8 push_prio = 0;
+	bool exists = false;
+	int ret = 0, err;
+	u32 index;
+
+	if (!nla)
+		return -EINVAL;
+
+	err = nla_parse_nested_deprecated(tb, TCA_VLAN_MAX, nla, vlan_policy,
+					  NULL);
+	if (err < 0)
+		return err;
+
+	if (!tb[TCA_VLAN_PARMS])
+		return -EINVAL;
+	parm = nla_data(tb[TCA_VLAN_PARMS]);
+	index = parm->index;
+	err = tcf_idr_check_alloc(tn, &index, a, bind);
+	if (err < 0)
+		return err;
+	exists = err;
+	if (exists && bind)
+		return ACT_P_BOUND;
+
+	switch (parm->v_action) {
+	case TCA_VLAN_ACT_POP:
+		break;
+	case TCA_VLAN_ACT_PUSH:
+	case TCA_VLAN_ACT_MODIFY:
+		if (!tb[TCA_VLAN_PUSH_VLAN_ID]) {
+			if (exists)
+				tcf_idr_release(*a, bind);
+			else
+				tcf_idr_cleanup(tn, index);
+			return -EINVAL;
+		}
+		push_vid = nla_get_u16(tb[TCA_VLAN_PUSH_VLAN_ID]);
+		if (push_vid >= VLAN_VID_MASK) {
+			if (exists)
+				tcf_idr_release(*a, bind);
+			else
+				tcf_idr_cleanup(tn, index);
+			return -ERANGE;
+		}
+
+		if (tb[TCA_VLAN_PUSH_VLAN_PROTOCOL]) {
+			push_proto = nla_get_be16(tb[TCA_VLAN_PUSH_VLAN_PROTOCOL]);
+			switch (push_proto) {
+			case htons(ETH_P_8021Q):
+			case htons(ETH_P_8021AD):
+				break;
+			default:
+				if (exists)
+					tcf_idr_release(*a, bind);
+				else
+					tcf_idr_cleanup(tn, index);
+				return -EPROTONOSUPPORT;
+			}
+		} else {
+			push_proto = htons(ETH_P_8021Q);
+		}
+
+		push_prio_exists = !!tb[TCA_VLAN_PUSH_VLAN_PRIORITY];
+		if (push_prio_exists)
+			push_prio = nla_get_u8(tb[TCA_VLAN_PUSH_VLAN_PRIORITY]);
+		break;
+	case TCA_VLAN_ACT_POP_ETH:
+		break;
+	case TCA_VLAN_ACT_PUSH_ETH:
+		if (!tb[TCA_VLAN_PUSH_ETH_DST] || !tb[TCA_VLAN_PUSH_ETH_SRC]) {
+			if (exists)
+				tcf_idr_release(*a, bind);
+			else
+				tcf_idr_cleanup(tn, index);
+			return -EINVAL;
+		}
+		break;
+	default:
+		if (exists)
+			tcf_idr_release(*a, bind);
+		else
+			tcf_idr_cleanup(tn, index);
+		return -EINVAL;
+	}
+	action = parm->v_action;
+
+	if (!exists) {
+		ret = tcf_idr_create_from_flags(tn, index, est, a,
+						&act_vlan_ops, bind, flags);
+		if (ret) {
+			tcf_idr_cleanup(tn, index);
+			return ret;
+		}
+
+		ret = ACT_P_CREATED;
+	} else if (!(flags & TCA_ACT_FLAGS_REPLACE)) {
+		tcf_idr_release(*a, bind);
+		return -EEXIST;
+	}
+
+	err = tcf_action_check_ctrlact(parm->action, tp, &goto_ch, extack);
+	if (err < 0)
+		goto release_idr;
+
+	v = to_vlan(*a);
+
+	p = kzalloc_obj(*p);
+	if (!p) {
+		err = -ENOMEM;
+		goto put_chain;
+	}
+
+	p->tcfv_action = action;
+	p->tcfv_push_vid = push_vid;
+	p->tcfv_push_prio = push_prio;
+	p->tcfv_push_prio_exists = push_prio_exists || action == TCA_VLAN_ACT_PUSH;
+	p->tcfv_push_proto = push_proto;
+
+	if (action == TCA_VLAN_ACT_PUSH_ETH) {
+		nla_memcpy(&p->tcfv_push_dst, tb[TCA_VLAN_PUSH_ETH_DST],
+			   ETH_ALEN);
+		nla_memcpy(&p->tcfv_push_src, tb[TCA_VLAN_PUSH_ETH_SRC],
+			   ETH_ALEN);
+	}
+
+	p->action = parm->action;
+	spin_lock_bh(&v->tcf_lock);
+	goto_ch = tcf_action_set_ctrlact(*a, parm->action, goto_ch);
+	p = rcu_replace_pointer(v->vlan_p, p, lockdep_is_held(&v->tcf_lock));
+	spin_unlock_bh(&v->tcf_lock);
+
+	if (goto_ch)
+		tcf_chain_put_by_act(goto_ch);
+	if (p)
+		kfree_rcu(p, rcu);
+
+	return ret;
+put_chain:
+	if (goto_ch)
+		tcf_chain_put_by_act(goto_ch);
+release_idr:
+	tcf_idr_release(*a, bind);
+	return err;
+}
+
+static void tcf_vlan_cleanup(struct tc_action *a)
+{
+	struct tcf_vlan *v = to_vlan(a);
+	struct tcf_vlan_params *p;
+
+	p = rcu_dereference_protected(v->vlan_p, 1);
+	if (p)
+		kfree_rcu(p, rcu);
+}
+
+static int tcf_vlan_dump(struct sk_buff *skb, struct tc_action *a,
+			 int bind, int ref)
+{
+	unsigned char *b = skb_tail_pointer(skb);
+	struct tcf_vlan *v = to_vlan(a);
+	struct tcf_vlan_params *p;
+	struct tc_vlan opt = {
+		.index    = v->tcf_index,
+		.refcnt   = refcount_read(&v->tcf_refcnt) - ref,
+		.bindcnt  = atomic_read(&v->tcf_bindcnt) - bind,
+	};
+	struct tcf_t t;
+
+	rcu_read_lock();
+	p = rcu_dereference(v->vlan_p);
+	opt.action = p->action;
+	opt.v_action = p->tcfv_action;
+	if (nla_put(skb, TCA_VLAN_PARMS, sizeof(opt), &opt))
+		goto nla_put_failure;
+
+	if ((p->tcfv_action == TCA_VLAN_ACT_PUSH ||
+	     p->tcfv_action == TCA_VLAN_ACT_MODIFY) &&
+	    (nla_put_u16(skb, TCA_VLAN_PUSH_VLAN_ID, p->tcfv_push_vid) ||
+	     nla_put_be16(skb, TCA_VLAN_PUSH_VLAN_PROTOCOL,
+			  p->tcfv_push_proto) ||
+	     (p->tcfv_push_prio_exists &&
+	      nla_put_u8(skb, TCA_VLAN_PUSH_VLAN_PRIORITY, p->tcfv_push_prio))))
+		goto nla_put_failure;
+
+	if (p->tcfv_action == TCA_VLAN_ACT_PUSH_ETH) {
+		if (nla_put(skb, TCA_VLAN_PUSH_ETH_DST, ETH_ALEN,
+			    p->tcfv_push_dst))
+			goto nla_put_failure;
+		if (nla_put(skb, TCA_VLAN_PUSH_ETH_SRC, ETH_ALEN,
+			    p->tcfv_push_src))
+			goto nla_put_failure;
+	}
+
+	tcf_tm_dump(&t, &v->tcf_tm);
+	if (nla_put_64bit(skb, TCA_VLAN_TM, sizeof(t), &t, TCA_VLAN_PAD))
+		goto nla_put_failure;
+	rcu_read_unlock();
+
+	return skb->len;
+
+nla_put_failure:
+	rcu_read_unlock();
+	nlmsg_trim(skb, b);
+	return -1;
+}
+
+static void tcf_vlan_stats_update(struct tc_action *a, u64 bytes, u64 packets,
+				  u64 drops, u64 lastuse, bool hw)
+{
+	struct tcf_vlan *v = to_vlan(a);
+	struct tcf_t *tm = &v->tcf_tm;
+
+	tcf_action_update_stats(a, bytes, packets, drops, hw);
+	tm->lastuse = max_t(u64, tm->lastuse, lastuse);
+}
+
+static size_t tcf_vlan_get_fill_size(const struct tc_action *act)
+{
+	return nla_total_size(sizeof(struct tc_vlan))
+		+ nla_total_size(sizeof(u16)) /* TCA_VLAN_PUSH_VLAN_ID */
+		+ nla_total_size(sizeof(u16)) /* TCA_VLAN_PUSH_VLAN_PROTOCOL */
+		+ nla_total_size(sizeof(u8)); /* TCA_VLAN_PUSH_VLAN_PRIORITY */
+}
+
+static int tcf_vlan_offload_act_setup(struct tc_action *act, void *entry_data,
+				      u32 *index_inc, bool bind,
+				      struct netlink_ext_ack *extack)
+{
+	if (bind) {
+		struct flow_action_entry *entry = entry_data;
+
+		switch (tcf_vlan_action(act)) {
+		case TCA_VLAN_ACT_PUSH:
+			entry->id = FLOW_ACTION_VLAN_PUSH;
+			entry->vlan.vid = tcf_vlan_push_vid(act);
+			entry->vlan.proto = tcf_vlan_push_proto(act);
+			entry->vlan.prio = tcf_vlan_push_prio(act);
+			break;
+		case TCA_VLAN_ACT_POP:
+			entry->id = FLOW_ACTION_VLAN_POP;
+			break;
+		case TCA_VLAN_ACT_MODIFY:
+			entry->id = FLOW_ACTION_VLAN_MANGLE;
+			entry->vlan.vid = tcf_vlan_push_vid(act);
+			entry->vlan.proto = tcf_vlan_push_proto(act);
+			entry->vlan.prio = tcf_vlan_push_prio(act);
+			break;
+		case TCA_VLAN_ACT_POP_ETH:
+			entry->id = FLOW_ACTION_VLAN_POP_ETH;
+			break;
+		case TCA_VLAN_ACT_PUSH_ETH:
+			entry->id = FLOW_ACTION_VLAN_PUSH_ETH;
+			tcf_vlan_push_eth(entry->vlan_push_eth.src, entry->vlan_push_eth.dst, act);
+			break;
+		default:
+			NL_SET_ERR_MSG_MOD(extack, "Unsupported vlan action mode offload");
+			return -EOPNOTSUPP;
+		}
+		*index_inc = 1;
+	} else {
+		struct flow_offload_action *fl_action = entry_data;
+
+		switch (tcf_vlan_action(act)) {
+		case TCA_VLAN_ACT_PUSH:
+			fl_action->id = FLOW_ACTION_VLAN_PUSH;
+			break;
+		case TCA_VLAN_ACT_POP:
+			fl_action->id = FLOW_ACTION_VLAN_POP;
+			break;
+		case TCA_VLAN_ACT_MODIFY:
+			fl_action->id = FLOW_ACTION_VLAN_MANGLE;
+			break;
+		case TCA_VLAN_ACT_POP_ETH:
+			fl_action->id = FLOW_ACTION_VLAN_POP_ETH;
+			break;
+		case TCA_VLAN_ACT_PUSH_ETH:
+			fl_action->id = FLOW_ACTION_VLAN_PUSH_ETH;
+			break;
+		default:
+			return -EOPNOTSUPP;
+		}
+	}
+
+	return 0;
+}
+
+static struct tc_action_ops act_vlan_ops = {
+	.kind		=	"vlan",
+	.id		=	TCA_ID_VLAN,
+	.owner		=	THIS_MODULE,
+	.act		=	tcf_vlan_act,
+	.dump		=	tcf_vlan_dump,
+	.init		=	tcf_vlan_init,
+	.cleanup	=	tcf_vlan_cleanup,
+	.stats_update	=	tcf_vlan_stats_update,
+	.get_fill_size	=	tcf_vlan_get_fill_size,
+	.offload_act_setup =	tcf_vlan_offload_act_setup,
+	.size		=	sizeof(struct tcf_vlan),
+};
+MODULE_ALIAS_NET_ACT("vlan");
+
+static __net_init int vlan_init_net(struct net *net)
+{
+	struct tc_action_net *tn = net_generic(net, act_vlan_ops.net_id);
+
+	return tc_action_net_init(net, tn, &act_vlan_ops);
+}
+
+static void __net_exit vlan_exit_net(struct list_head *net_list)
+{
+	tc_action_net_exit(net_list, act_vlan_ops.net_id);
+}
+
+static struct pernet_operations vlan_net_ops = {
+	.init = vlan_init_net,
+	.exit_batch = vlan_exit_net,
+	.id   = &act_vlan_ops.net_id,
+	.size = sizeof(struct tc_action_net),
+};
+
+static int __init vlan_init_module(void)
+{
+	return tcf_register_action(&act_vlan_ops, &vlan_net_ops);
+}
+
+static void __exit vlan_cleanup_module(void)
+{
+	tcf_unregister_action(&act_vlan_ops, &vlan_net_ops);
+}
+
+module_init(vlan_init_module);
+module_exit(vlan_cleanup_module);
+
+MODULE_AUTHOR("Jiri Pirko <jiri@resnulli.us>");
+MODULE_DESCRIPTION("vlan manipulation actions");
+MODULE_LICENSE("GPL v2");