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, 136 insertions, 0 deletions

diff --git a/include/net/dcbnl.h b/include/net/dcbnl.h
new file mode 100644
index 000000000..42207fc44
--- /dev/null
+++ b/include/net/dcbnl.h
@@ -0,0 +1,136 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (c) 2008, Intel Corporation.
+ *
+ * Author: Lucy Liu <lucy.liu@intel.com>
+ */
+
+#ifndef __NET_DCBNL_H__
+#define __NET_DCBNL_H__
+
+#include <linux/dcbnl.h>
+
+struct net_device;
+
+struct dcb_app_type {
+	int	ifindex;
+	struct dcb_app	  app;
+	struct list_head  list;
+	u8	dcbx;
+};
+
+u16 dcb_getrewr(struct net_device *dev, struct dcb_app *app);
+int dcb_setrewr(struct net_device *dev, struct dcb_app *app);
+int dcb_delrewr(struct net_device *dev, struct dcb_app *app);
+
+int dcb_setapp(struct net_device *, struct dcb_app *);
+u8 dcb_getapp(struct net_device *, struct dcb_app *);
+int dcb_ieee_setapp(struct net_device *, struct dcb_app *);
+int dcb_ieee_delapp(struct net_device *, struct dcb_app *);
+u8 dcb_ieee_getapp_mask(struct net_device *, struct dcb_app *);
+
+struct dcb_rewr_prio_pcp_map {
+	u16 map[IEEE_8021QAZ_MAX_TCS];
+};
+
+void dcb_getrewr_prio_pcp_mask_map(const struct net_device *dev,
+				   struct dcb_rewr_prio_pcp_map *p_map);
+
+struct dcb_ieee_app_prio_map {
+	u64 map[IEEE_8021QAZ_MAX_TCS];
+};
+void dcb_ieee_getapp_prio_dscp_mask_map(const struct net_device *dev,
+					struct dcb_ieee_app_prio_map *p_map);
+
+void dcb_getrewr_prio_dscp_mask_map(const struct net_device *dev,
+				    struct dcb_ieee_app_prio_map *p_map);
+
+struct dcb_ieee_app_dscp_map {
+	u8 map[64];
+};
+void dcb_ieee_getapp_dscp_prio_mask_map(const struct net_device *dev,
+					struct dcb_ieee_app_dscp_map *p_map);
+u8 dcb_ieee_getapp_default_prio_mask(const struct net_device *dev);
+
+int dcbnl_ieee_notify(struct net_device *dev, int event, int cmd,
+		      u32 seq, u32 pid);
+int dcbnl_cee_notify(struct net_device *dev, int event, int cmd,
+		     u32 seq, u32 pid);
+
+/*
+ * Ops struct for the netlink callbacks.  Used by DCB-enabled drivers through
+ * the netdevice struct.
+ */
+struct dcbnl_rtnl_ops {
+	/* IEEE 802.1Qaz std */
+	int (*ieee_getets) (struct net_device *, struct ieee_ets *);
+	int (*ieee_setets) (struct net_device *, struct ieee_ets *);
+	int (*ieee_getmaxrate) (struct net_device *, struct ieee_maxrate *);
+	int (*ieee_setmaxrate) (struct net_device *, struct ieee_maxrate *);
+	int (*ieee_getqcn) (struct net_device *, struct ieee_qcn *);
+	int (*ieee_setqcn) (struct net_device *, struct ieee_qcn *);
+	int (*ieee_getqcnstats) (struct net_device *, struct ieee_qcn_stats *);
+	int (*ieee_getpfc) (struct net_device *, struct ieee_pfc *);
+	int (*ieee_setpfc) (struct net_device *, struct ieee_pfc *);
+	int (*ieee_getapp) (struct net_device *, struct dcb_app *);
+	int (*ieee_setapp) (struct net_device *, struct dcb_app *);
+	int (*ieee_delapp) (struct net_device *, struct dcb_app *);
+	int (*ieee_peer_getets) (struct net_device *, struct ieee_ets *);
+	int (*ieee_peer_getpfc) (struct net_device *, struct ieee_pfc *);
+
+	/* CEE std */
+	u8   (*getstate)(struct net_device *);
+	u8   (*setstate)(struct net_device *, u8);
+	void (*getpermhwaddr)(struct net_device *, u8 *);
+	void (*setpgtccfgtx)(struct net_device *, int, u8, u8, u8, u8);
+	void (*setpgbwgcfgtx)(struct net_device *, int, u8);
+	void (*setpgtccfgrx)(struct net_device *, int, u8, u8, u8, u8);
+	void (*setpgbwgcfgrx)(struct net_device *, int, u8);
+	void (*getpgtccfgtx)(struct net_device *, int, u8 *, u8 *, u8 *, u8 *);
+	void (*getpgbwgcfgtx)(struct net_device *, int, u8 *);
+	void (*getpgtccfgrx)(struct net_device *, int, u8 *, u8 *, u8 *, u8 *);
+	void (*getpgbwgcfgrx)(struct net_device *, int, u8 *);
+	void (*setpfccfg)(struct net_device *, int, u8);
+	void (*getpfccfg)(struct net_device *, int, u8 *);
+	u8   (*setall)(struct net_device *);
+	u8   (*getcap)(struct net_device *, int, u8 *);
+	int  (*getnumtcs)(struct net_device *, int, u8 *);
+	int  (*setnumtcs)(struct net_device *, int, u8);
+	u8   (*getpfcstate)(struct net_device *);
+	void (*setpfcstate)(struct net_device *, u8);
+	void (*getbcncfg)(struct net_device *, int, u32 *);
+	void (*setbcncfg)(struct net_device *, int, u32);
+	void (*getbcnrp)(struct net_device *, int, u8 *);
+	void (*setbcnrp)(struct net_device *, int, u8);
+	int  (*setapp)(struct net_device *, u8, u16, u8);
+	int  (*getapp)(struct net_device *, u8, u16);
+	u8   (*getfeatcfg)(struct net_device *, int, u8 *);
+	u8   (*setfeatcfg)(struct net_device *, int, u8);
+
+	/* DCBX configuration */
+	u8   (*getdcbx)(struct net_device *);
+	u8   (*setdcbx)(struct net_device *, u8);
+
+	/* peer apps */
+	int (*peer_getappinfo)(struct net_device *, struct dcb_peer_app_info *,
+			       u16 *);
+	int (*peer_getapptable)(struct net_device *, struct dcb_app *);
+
+	/* CEE peer */
+	int (*cee_peer_getpg) (struct net_device *, struct cee_pg *);
+	int (*cee_peer_getpfc) (struct net_device *, struct cee_pfc *);
+
+	/* buffer settings */
+	int (*dcbnl_getbuffer)(struct net_device *, struct dcbnl_buffer *);
+	int (*dcbnl_setbuffer)(struct net_device *, struct dcbnl_buffer *);
+
+	/* apptrust */
+	int (*dcbnl_setapptrust)(struct net_device *, u8 *, int);
+	int (*dcbnl_getapptrust)(struct net_device *, u8 *, int *);
+
+	/* rewrite */
+	int (*dcbnl_setrewr)(struct net_device *dev, struct dcb_app *app);
+	int (*dcbnl_delrewr)(struct net_device *dev, struct dcb_app *app);
+};
+
+#endif /* __NET_DCBNL_H__ */