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, 447 insertions, 0 deletions

diff --git a/net/dsa/trace.h b/net/dsa/trace.h
new file mode 100644
index 000000000..83f3e5f78
--- /dev/null
+++ b/net/dsa/trace.h
@@ -0,0 +1,447 @@
+/* SPDX-License-Identifier: GPL-2.0
+ * Copyright 2022-2023 NXP
+ */
+
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM	dsa
+
+#if !defined(_NET_DSA_TRACE_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _NET_DSA_TRACE_H
+
+#include <net/dsa.h>
+#include <net/switchdev.h>
+#include <linux/etherdevice.h>
+#include <linux/if_bridge.h>
+#include <linux/refcount.h>
+#include <linux/tracepoint.h>
+
+/* Enough to fit "bridge %s num %d" where num has 3 digits */
+#define DSA_DB_BUFSIZ	(IFNAMSIZ + 16)
+
+void dsa_db_print(const struct dsa_db *db, char buf[DSA_DB_BUFSIZ]);
+const char *dsa_port_kind(const struct dsa_port *dp);
+
+DECLARE_EVENT_CLASS(dsa_port_addr_op_hw,
+
+	TP_PROTO(const struct dsa_port *dp, const unsigned char *addr, u16 vid,
+		 const struct dsa_db *db, int err),
+
+	TP_ARGS(dp, addr, vid, db, err),
+
+	TP_STRUCT__entry(
+		__string(dev, dev_name(dp->ds->dev))
+		__string(kind, dsa_port_kind(dp))
+		__field(int, port)
+		__array(unsigned char, addr, ETH_ALEN)
+		__field(u16, vid)
+		__array(char, db_buf, DSA_DB_BUFSIZ)
+		__field(int, err)
+	),
+
+	TP_fast_assign(
+		__assign_str(dev);
+		__assign_str(kind);
+		__entry->port = dp->index;
+		ether_addr_copy(__entry->addr, addr);
+		__entry->vid = vid;
+		dsa_db_print(db, __entry->db_buf);
+		__entry->err = err;
+	),
+
+	TP_printk("%s %s port %d addr %pM vid %u db \"%s\" err %d",
+		  __get_str(dev), __get_str(kind), __entry->port, __entry->addr,
+		  __entry->vid, __entry->db_buf, __entry->err)
+);
+
+/* Add unicast/multicast address to hardware, either on user ports
+ * (where no refcounting is kept), or on shared ports when the entry
+ * is first seen and its refcount is 1.
+ */
+DEFINE_EVENT(dsa_port_addr_op_hw, dsa_fdb_add_hw,
+	     TP_PROTO(const struct dsa_port *dp, const unsigned char *addr,
+		      u16 vid, const struct dsa_db *db, int err),
+	     TP_ARGS(dp, addr, vid, db, err));
+
+DEFINE_EVENT(dsa_port_addr_op_hw, dsa_mdb_add_hw,
+	     TP_PROTO(const struct dsa_port *dp, const unsigned char *addr,
+		      u16 vid, const struct dsa_db *db, int err),
+	     TP_ARGS(dp, addr, vid, db, err));
+
+/* Delete unicast/multicast address from hardware, either on user ports or
+ * when the refcount on shared ports reaches 0
+ */
+DEFINE_EVENT(dsa_port_addr_op_hw, dsa_fdb_del_hw,
+	     TP_PROTO(const struct dsa_port *dp, const unsigned char *addr,
+		      u16 vid, const struct dsa_db *db, int err),
+	     TP_ARGS(dp, addr, vid, db, err));
+
+DEFINE_EVENT(dsa_port_addr_op_hw, dsa_mdb_del_hw,
+	     TP_PROTO(const struct dsa_port *dp, const unsigned char *addr,
+		      u16 vid, const struct dsa_db *db, int err),
+	     TP_ARGS(dp, addr, vid, db, err));
+
+DECLARE_EVENT_CLASS(dsa_port_addr_op_refcount,
+
+	TP_PROTO(const struct dsa_port *dp, const unsigned char *addr, u16 vid,
+		 const struct dsa_db *db, const refcount_t *refcount),
+
+	TP_ARGS(dp, addr, vid, db, refcount),
+
+	TP_STRUCT__entry(
+		__string(dev, dev_name(dp->ds->dev))
+		__string(kind, dsa_port_kind(dp))
+		__field(int, port)
+		__array(unsigned char, addr, ETH_ALEN)
+		__field(u16, vid)
+		__array(char, db_buf, DSA_DB_BUFSIZ)
+		__field(unsigned int, refcount)
+	),
+
+	TP_fast_assign(
+		__assign_str(dev);
+		__assign_str(kind);
+		__entry->port = dp->index;
+		ether_addr_copy(__entry->addr, addr);
+		__entry->vid = vid;
+		dsa_db_print(db, __entry->db_buf);
+		__entry->refcount = refcount_read(refcount);
+	),
+
+	TP_printk("%s %s port %d addr %pM vid %u db \"%s\" refcount %u",
+		  __get_str(dev), __get_str(kind), __entry->port, __entry->addr,
+		  __entry->vid, __entry->db_buf, __entry->refcount)
+);
+
+/* Bump the refcount of an existing unicast/multicast address on shared ports */
+DEFINE_EVENT(dsa_port_addr_op_refcount, dsa_fdb_add_bump,
+	     TP_PROTO(const struct dsa_port *dp, const unsigned char *addr,
+		      u16 vid, const struct dsa_db *db,
+		      const refcount_t *refcount),
+	     TP_ARGS(dp, addr, vid, db, refcount));
+
+DEFINE_EVENT(dsa_port_addr_op_refcount, dsa_mdb_add_bump,
+	     TP_PROTO(const struct dsa_port *dp, const unsigned char *addr,
+		      u16 vid, const struct dsa_db *db,
+		      const refcount_t *refcount),
+	     TP_ARGS(dp, addr, vid, db, refcount));
+
+/* Drop the refcount of a multicast address that we still keep on
+ * shared ports
+ */
+DEFINE_EVENT(dsa_port_addr_op_refcount, dsa_fdb_del_drop,
+	     TP_PROTO(const struct dsa_port *dp, const unsigned char *addr,
+		      u16 vid, const struct dsa_db *db,
+		      const refcount_t *refcount),
+	     TP_ARGS(dp, addr, vid, db, refcount));
+
+DEFINE_EVENT(dsa_port_addr_op_refcount, dsa_mdb_del_drop,
+	     TP_PROTO(const struct dsa_port *dp, const unsigned char *addr,
+		      u16 vid, const struct dsa_db *db,
+		      const refcount_t *refcount),
+	     TP_ARGS(dp, addr, vid, db, refcount));
+
+DECLARE_EVENT_CLASS(dsa_port_addr_del_not_found,
+
+	TP_PROTO(const struct dsa_port *dp, const unsigned char *addr, u16 vid,
+		 const struct dsa_db *db),
+
+	TP_ARGS(dp, addr, vid, db),
+
+	TP_STRUCT__entry(
+		__string(dev, dev_name(dp->ds->dev))
+		__string(kind, dsa_port_kind(dp))
+		__field(int, port)
+		__array(unsigned char, addr, ETH_ALEN)
+		__field(u16, vid)
+		__array(char, db_buf, DSA_DB_BUFSIZ)
+	),
+
+	TP_fast_assign(
+		__assign_str(dev);
+		__assign_str(kind);
+		__entry->port = dp->index;
+		ether_addr_copy(__entry->addr, addr);
+		__entry->vid = vid;
+		dsa_db_print(db, __entry->db_buf);
+	),
+
+	TP_printk("%s %s port %d addr %pM vid %u db \"%s\"",
+		  __get_str(dev), __get_str(kind), __entry->port,
+		  __entry->addr, __entry->vid, __entry->db_buf)
+);
+
+/* Attempt to delete a unicast/multicast address on shared ports for which
+ * the delete operation was called more times than the addition
+ */
+DEFINE_EVENT(dsa_port_addr_del_not_found, dsa_fdb_del_not_found,
+	     TP_PROTO(const struct dsa_port *dp, const unsigned char *addr,
+		      u16 vid, const struct dsa_db *db),
+	     TP_ARGS(dp, addr, vid, db));
+
+DEFINE_EVENT(dsa_port_addr_del_not_found, dsa_mdb_del_not_found,
+	     TP_PROTO(const struct dsa_port *dp, const unsigned char *addr,
+		      u16 vid, const struct dsa_db *db),
+	     TP_ARGS(dp, addr, vid, db));
+
+TRACE_EVENT(dsa_lag_fdb_add_hw,
+
+	TP_PROTO(const struct net_device *lag_dev, const unsigned char *addr,
+		 u16 vid, const struct dsa_db *db, int err),
+
+	TP_ARGS(lag_dev, addr, vid, db, err),
+
+	TP_STRUCT__entry(
+		__string(dev, lag_dev->name)
+		__array(unsigned char, addr, ETH_ALEN)
+		__field(u16, vid)
+		__array(char, db_buf, DSA_DB_BUFSIZ)
+		__field(int, err)
+	),
+
+	TP_fast_assign(
+		__assign_str(dev);
+		ether_addr_copy(__entry->addr, addr);
+		__entry->vid = vid;
+		dsa_db_print(db, __entry->db_buf);
+		__entry->err = err;
+	),
+
+	TP_printk("%s addr %pM vid %u db \"%s\" err %d",
+		  __get_str(dev), __entry->addr, __entry->vid,
+		  __entry->db_buf, __entry->err)
+);
+
+TRACE_EVENT(dsa_lag_fdb_add_bump,
+
+	TP_PROTO(const struct net_device *lag_dev, const unsigned char *addr,
+		 u16 vid, const struct dsa_db *db, const refcount_t *refcount),
+
+	TP_ARGS(lag_dev, addr, vid, db, refcount),
+
+	TP_STRUCT__entry(
+		__string(dev, lag_dev->name)
+		__array(unsigned char, addr, ETH_ALEN)
+		__field(u16, vid)
+		__array(char, db_buf, DSA_DB_BUFSIZ)
+		__field(unsigned int, refcount)
+	),
+
+	TP_fast_assign(
+		__assign_str(dev);
+		ether_addr_copy(__entry->addr, addr);
+		__entry->vid = vid;
+		dsa_db_print(db, __entry->db_buf);
+		__entry->refcount = refcount_read(refcount);
+	),
+
+	TP_printk("%s addr %pM vid %u db \"%s\" refcount %u",
+		  __get_str(dev), __entry->addr, __entry->vid,
+		  __entry->db_buf, __entry->refcount)
+);
+
+TRACE_EVENT(dsa_lag_fdb_del_hw,
+
+	TP_PROTO(const struct net_device *lag_dev, const unsigned char *addr,
+		 u16 vid, const struct dsa_db *db, int err),
+
+	TP_ARGS(lag_dev, addr, vid, db, err),
+
+	TP_STRUCT__entry(
+		__string(dev, lag_dev->name)
+		__array(unsigned char, addr, ETH_ALEN)
+		__field(u16, vid)
+		__array(char, db_buf, DSA_DB_BUFSIZ)
+		__field(int, err)
+	),
+
+	TP_fast_assign(
+		__assign_str(dev);
+		ether_addr_copy(__entry->addr, addr);
+		__entry->vid = vid;
+		dsa_db_print(db, __entry->db_buf);
+		__entry->err = err;
+	),
+
+	TP_printk("%s addr %pM vid %u db \"%s\" err %d",
+		  __get_str(dev), __entry->addr, __entry->vid,
+		  __entry->db_buf, __entry->err)
+);
+
+TRACE_EVENT(dsa_lag_fdb_del_drop,
+
+	TP_PROTO(const struct net_device *lag_dev, const unsigned char *addr,
+		 u16 vid, const struct dsa_db *db, const refcount_t *refcount),
+
+	TP_ARGS(lag_dev, addr, vid, db, refcount),
+
+	TP_STRUCT__entry(
+		__string(dev, lag_dev->name)
+		__array(unsigned char, addr, ETH_ALEN)
+		__field(u16, vid)
+		__array(char, db_buf, DSA_DB_BUFSIZ)
+		__field(unsigned int, refcount)
+	),
+
+	TP_fast_assign(
+		__assign_str(dev);
+		ether_addr_copy(__entry->addr, addr);
+		__entry->vid = vid;
+		dsa_db_print(db, __entry->db_buf);
+		__entry->refcount = refcount_read(refcount);
+	),
+
+	TP_printk("%s addr %pM vid %u db \"%s\" refcount %u",
+		  __get_str(dev), __entry->addr, __entry->vid,
+		  __entry->db_buf, __entry->refcount)
+);
+
+TRACE_EVENT(dsa_lag_fdb_del_not_found,
+
+	TP_PROTO(const struct net_device *lag_dev, const unsigned char *addr,
+		 u16 vid, const struct dsa_db *db),
+
+	TP_ARGS(lag_dev, addr, vid, db),
+
+	TP_STRUCT__entry(
+		__string(dev, lag_dev->name)
+		__array(unsigned char, addr, ETH_ALEN)
+		__field(u16, vid)
+		__array(char, db_buf, DSA_DB_BUFSIZ)
+	),
+
+	TP_fast_assign(
+		__assign_str(dev);
+		ether_addr_copy(__entry->addr, addr);
+		__entry->vid = vid;
+		dsa_db_print(db, __entry->db_buf);
+	),
+
+	TP_printk("%s addr %pM vid %u db \"%s\"",
+		  __get_str(dev), __entry->addr, __entry->vid, __entry->db_buf)
+);
+
+DECLARE_EVENT_CLASS(dsa_vlan_op_hw,
+
+	TP_PROTO(const struct dsa_port *dp,
+		 const struct switchdev_obj_port_vlan *vlan, int err),
+
+	TP_ARGS(dp, vlan, err),
+
+	TP_STRUCT__entry(
+		__string(dev, dev_name(dp->ds->dev))
+		__string(kind, dsa_port_kind(dp))
+		__field(int, port)
+		__field(u16, vid)
+		__field(u16, flags)
+		__field(bool, changed)
+		__field(int, err)
+	),
+
+	TP_fast_assign(
+		__assign_str(dev);
+		__assign_str(kind);
+		__entry->port = dp->index;
+		__entry->vid = vlan->vid;
+		__entry->flags = vlan->flags;
+		__entry->changed = vlan->changed;
+		__entry->err = err;
+	),
+
+	TP_printk("%s %s port %d vid %u%s%s%s",
+		  __get_str(dev), __get_str(kind), __entry->port, __entry->vid,
+		  __entry->flags & BRIDGE_VLAN_INFO_PVID ? " pvid" : "",
+		  __entry->flags & BRIDGE_VLAN_INFO_UNTAGGED ? " untagged" : "",
+		  __entry->changed ? " (changed)" : "")
+);
+
+DEFINE_EVENT(dsa_vlan_op_hw, dsa_vlan_add_hw,
+	     TP_PROTO(const struct dsa_port *dp,
+		      const struct switchdev_obj_port_vlan *vlan, int err),
+	     TP_ARGS(dp, vlan, err));
+
+DEFINE_EVENT(dsa_vlan_op_hw, dsa_vlan_del_hw,
+	     TP_PROTO(const struct dsa_port *dp,
+		      const struct switchdev_obj_port_vlan *vlan, int err),
+	     TP_ARGS(dp, vlan, err));
+
+DECLARE_EVENT_CLASS(dsa_vlan_op_refcount,
+
+	TP_PROTO(const struct dsa_port *dp,
+		 const struct switchdev_obj_port_vlan *vlan,
+		 const refcount_t *refcount),
+
+	TP_ARGS(dp, vlan, refcount),
+
+	TP_STRUCT__entry(
+		__string(dev, dev_name(dp->ds->dev))
+		__string(kind, dsa_port_kind(dp))
+		__field(int, port)
+		__field(u16, vid)
+		__field(u16, flags)
+		__field(bool, changed)
+		__field(unsigned int, refcount)
+	),
+
+	TP_fast_assign(
+		__assign_str(dev);
+		__assign_str(kind);
+		__entry->port = dp->index;
+		__entry->vid = vlan->vid;
+		__entry->flags = vlan->flags;
+		__entry->changed = vlan->changed;
+		__entry->refcount = refcount_read(refcount);
+	),
+
+	TP_printk("%s %s port %d vid %u%s%s%s refcount %u",
+		  __get_str(dev), __get_str(kind), __entry->port, __entry->vid,
+		  __entry->flags & BRIDGE_VLAN_INFO_PVID ? " pvid" : "",
+		  __entry->flags & BRIDGE_VLAN_INFO_UNTAGGED ? " untagged" : "",
+		  __entry->changed ? " (changed)" : "", __entry->refcount)
+);
+
+DEFINE_EVENT(dsa_vlan_op_refcount, dsa_vlan_add_bump,
+	     TP_PROTO(const struct dsa_port *dp,
+		      const struct switchdev_obj_port_vlan *vlan,
+		      const refcount_t *refcount),
+	     TP_ARGS(dp, vlan, refcount));
+
+DEFINE_EVENT(dsa_vlan_op_refcount, dsa_vlan_del_drop,
+	     TP_PROTO(const struct dsa_port *dp,
+		      const struct switchdev_obj_port_vlan *vlan,
+		      const refcount_t *refcount),
+	     TP_ARGS(dp, vlan, refcount));
+
+TRACE_EVENT(dsa_vlan_del_not_found,
+
+	TP_PROTO(const struct dsa_port *dp,
+		 const struct switchdev_obj_port_vlan *vlan),
+
+	TP_ARGS(dp, vlan),
+
+	TP_STRUCT__entry(
+		__string(dev, dev_name(dp->ds->dev))
+		__string(kind, dsa_port_kind(dp))
+		__field(int, port)
+		__field(u16, vid)
+	),
+
+	TP_fast_assign(
+		__assign_str(dev);
+		__assign_str(kind);
+		__entry->port = dp->index;
+		__entry->vid = vlan->vid;
+	),
+
+	TP_printk("%s %s port %d vid %u",
+		  __get_str(dev), __get_str(kind), __entry->port, __entry->vid)
+);
+
+#endif /* _NET_DSA_TRACE_H */
+
+/* We don't want to use include/trace/events */
+#undef TRACE_INCLUDE_PATH
+#define TRACE_INCLUDE_PATH .
+#undef TRACE_INCLUDE_FILE
+#define TRACE_INCLUDE_FILE	trace
+/* This part must be outside protection */
+#include <trace/define_trace.h>