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, 298 insertions, 0 deletions

diff --git a/net/mac802154/trace.h b/net/mac802154/trace.h
new file mode 100644
index 000000000..1574ecc48
--- /dev/null
+++ b/net/mac802154/trace.h
@@ -0,0 +1,298 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Based on net/mac80211/trace.h */
+
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM mac802154
+
+#if !defined(__MAC802154_DRIVER_TRACE) || defined(TRACE_HEADER_MULTI_READ)
+#define __MAC802154_DRIVER_TRACE
+
+#include <linux/tracepoint.h>
+
+#include <net/mac802154.h>
+#include "ieee802154_i.h"
+
+#define MAXNAME		32
+#define LOCAL_ENTRY	__array(char, wpan_phy_name, MAXNAME)
+#define LOCAL_ASSIGN	strscpy(__entry->wpan_phy_name, \
+				wpan_phy_name(local->hw.phy), MAXNAME)
+#define LOCAL_PR_FMT	"%s"
+#define LOCAL_PR_ARG	__entry->wpan_phy_name
+
+#define CCA_ENTRY __field(enum nl802154_cca_modes, cca_mode) \
+		  __field(enum nl802154_cca_opts, cca_opt)
+#define CCA_ASSIGN \
+	do {                                     \
+		(__entry->cca_mode) = cca->mode; \
+		(__entry->cca_opt) = cca->opt;   \
+	} while (0)
+#define CCA_PR_FMT "cca_mode: %d, cca_opt: %d"
+#define CCA_PR_ARG __entry->cca_mode, __entry->cca_opt
+
+#define BOOL_TO_STR(bo) (bo) ? "true" : "false"
+
+/* Tracing for driver callbacks */
+
+DECLARE_EVENT_CLASS(local_only_evt4,
+	TP_PROTO(struct ieee802154_local *local),
+	TP_ARGS(local),
+	TP_STRUCT__entry(
+		LOCAL_ENTRY
+	),
+	TP_fast_assign(
+		LOCAL_ASSIGN;
+	),
+	TP_printk(LOCAL_PR_FMT, LOCAL_PR_ARG)
+);
+
+DEFINE_EVENT(local_only_evt4, 802154_drv_return_void,
+	TP_PROTO(struct ieee802154_local *local),
+	TP_ARGS(local)
+);
+
+TRACE_EVENT(802154_drv_return_int,
+	TP_PROTO(struct ieee802154_local *local, int ret),
+	TP_ARGS(local, ret),
+	TP_STRUCT__entry(
+		LOCAL_ENTRY
+		__field(int, ret)
+	),
+	TP_fast_assign(
+		LOCAL_ASSIGN;
+		__entry->ret = ret;
+	),
+	TP_printk(LOCAL_PR_FMT ", returned: %d", LOCAL_PR_ARG,
+		  __entry->ret)
+);
+
+DEFINE_EVENT(local_only_evt4, 802154_drv_start,
+	TP_PROTO(struct ieee802154_local *local),
+	TP_ARGS(local)
+);
+
+DEFINE_EVENT(local_only_evt4, 802154_drv_stop,
+	TP_PROTO(struct ieee802154_local *local),
+	TP_ARGS(local)
+);
+
+TRACE_EVENT(802154_drv_set_channel,
+	TP_PROTO(struct ieee802154_local *local, u8 page, u8 channel),
+	TP_ARGS(local, page, channel),
+	TP_STRUCT__entry(
+		LOCAL_ENTRY
+		__field(u8, page)
+		__field(u8, channel)
+	),
+	TP_fast_assign(
+		LOCAL_ASSIGN;
+		__entry->page = page;
+		__entry->channel = channel;
+	),
+	TP_printk(LOCAL_PR_FMT ", page: %d, channel: %d", LOCAL_PR_ARG,
+		  __entry->page, __entry->channel)
+);
+
+TRACE_EVENT(802154_drv_set_cca_mode,
+	TP_PROTO(struct ieee802154_local *local,
+		 const struct wpan_phy_cca *cca),
+	TP_ARGS(local, cca),
+	TP_STRUCT__entry(
+		LOCAL_ENTRY
+		CCA_ENTRY
+	),
+	TP_fast_assign(
+		LOCAL_ASSIGN;
+		CCA_ASSIGN;
+	),
+	TP_printk(LOCAL_PR_FMT ", " CCA_PR_FMT, LOCAL_PR_ARG,
+		  CCA_PR_ARG)
+);
+
+TRACE_EVENT(802154_drv_set_cca_ed_level,
+	TP_PROTO(struct ieee802154_local *local, s32 mbm),
+	TP_ARGS(local, mbm),
+	TP_STRUCT__entry(
+		LOCAL_ENTRY
+		__field(s32, mbm)
+	),
+	TP_fast_assign(
+		LOCAL_ASSIGN;
+		__entry->mbm = mbm;
+	),
+	TP_printk(LOCAL_PR_FMT ", ed level: %d", LOCAL_PR_ARG,
+		  __entry->mbm)
+);
+
+TRACE_EVENT(802154_drv_set_tx_power,
+	TP_PROTO(struct ieee802154_local *local, s32 power),
+	TP_ARGS(local, power),
+	TP_STRUCT__entry(
+		LOCAL_ENTRY
+		__field(s32, power)
+	),
+	TP_fast_assign(
+		LOCAL_ASSIGN;
+		__entry->power = power;
+	),
+	TP_printk(LOCAL_PR_FMT ", mbm: %d", LOCAL_PR_ARG,
+		 __entry->power)
+);
+
+TRACE_EVENT(802154_drv_set_lbt_mode,
+	TP_PROTO(struct ieee802154_local *local, bool mode),
+	TP_ARGS(local, mode),
+	TP_STRUCT__entry(
+		LOCAL_ENTRY
+		__field(bool, mode)
+	),
+	TP_fast_assign(
+		LOCAL_ASSIGN;
+		__entry->mode = mode;
+	),
+	TP_printk(LOCAL_PR_FMT ", lbt mode: %s", LOCAL_PR_ARG,
+		  BOOL_TO_STR(__entry->mode))
+);
+
+TRACE_EVENT(802154_drv_set_short_addr,
+	TP_PROTO(struct ieee802154_local *local, __le16 short_addr),
+	TP_ARGS(local, short_addr),
+	TP_STRUCT__entry(
+		LOCAL_ENTRY
+		__field(__le16, short_addr)
+	),
+	TP_fast_assign(
+		LOCAL_ASSIGN;
+		__entry->short_addr = short_addr;
+	),
+	TP_printk(LOCAL_PR_FMT ", short addr: 0x%04x", LOCAL_PR_ARG,
+		  le16_to_cpu(__entry->short_addr))
+);
+
+TRACE_EVENT(802154_drv_set_pan_id,
+	TP_PROTO(struct ieee802154_local *local, __le16 pan_id),
+	TP_ARGS(local, pan_id),
+	TP_STRUCT__entry(
+		LOCAL_ENTRY
+		__field(__le16, pan_id)
+	),
+	TP_fast_assign(
+		LOCAL_ASSIGN;
+		__entry->pan_id = pan_id;
+	),
+	TP_printk(LOCAL_PR_FMT ", pan id: 0x%04x", LOCAL_PR_ARG,
+		  le16_to_cpu(__entry->pan_id))
+);
+
+TRACE_EVENT(802154_drv_set_extended_addr,
+	TP_PROTO(struct ieee802154_local *local, __le64 extended_addr),
+	TP_ARGS(local, extended_addr),
+	TP_STRUCT__entry(
+		LOCAL_ENTRY
+		__field(__le64, extended_addr)
+	),
+	TP_fast_assign(
+		LOCAL_ASSIGN;
+		__entry->extended_addr = extended_addr;
+	),
+	TP_printk(LOCAL_PR_FMT ", extended addr: 0x%llx", LOCAL_PR_ARG,
+		  le64_to_cpu(__entry->extended_addr))
+);
+
+TRACE_EVENT(802154_drv_set_pan_coord,
+	TP_PROTO(struct ieee802154_local *local, bool is_coord),
+	TP_ARGS(local, is_coord),
+	TP_STRUCT__entry(
+		LOCAL_ENTRY
+		__field(bool, is_coord)
+	),
+	TP_fast_assign(
+		LOCAL_ASSIGN;
+		__entry->is_coord = is_coord;
+	),
+	TP_printk(LOCAL_PR_FMT ", is_coord: %s", LOCAL_PR_ARG,
+		  BOOL_TO_STR(__entry->is_coord))
+);
+
+TRACE_EVENT(802154_drv_set_csma_params,
+	TP_PROTO(struct ieee802154_local *local, u8 min_be, u8 max_be,
+		 u8 max_csma_backoffs),
+	TP_ARGS(local, min_be, max_be, max_csma_backoffs),
+	TP_STRUCT__entry(
+		LOCAL_ENTRY
+		__field(u8, min_be)
+		__field(u8, max_be)
+		__field(u8, max_csma_backoffs)
+	),
+	TP_fast_assign(
+		LOCAL_ASSIGN,
+		__entry->min_be = min_be;
+		__entry->max_be = max_be;
+		__entry->max_csma_backoffs = max_csma_backoffs;
+	),
+	TP_printk(LOCAL_PR_FMT ", min be: %d, max be: %d, max csma backoffs: %d",
+		  LOCAL_PR_ARG, __entry->min_be, __entry->max_be,
+		  __entry->max_csma_backoffs)
+);
+
+TRACE_EVENT(802154_drv_set_max_frame_retries,
+	TP_PROTO(struct ieee802154_local *local, s8 max_frame_retries),
+	TP_ARGS(local, max_frame_retries),
+	TP_STRUCT__entry(
+		LOCAL_ENTRY
+		__field(s8, max_frame_retries)
+	),
+	TP_fast_assign(
+		LOCAL_ASSIGN;
+		__entry->max_frame_retries = max_frame_retries;
+	),
+	TP_printk(LOCAL_PR_FMT ", max frame retries: %d", LOCAL_PR_ARG,
+		  __entry->max_frame_retries)
+);
+
+TRACE_EVENT(802154_drv_set_promiscuous_mode,
+	TP_PROTO(struct ieee802154_local *local, bool on),
+	TP_ARGS(local, on),
+	TP_STRUCT__entry(
+		LOCAL_ENTRY
+		__field(bool, on)
+	),
+	TP_fast_assign(
+		LOCAL_ASSIGN;
+		__entry->on = on;
+	),
+	TP_printk(LOCAL_PR_FMT ", promiscuous mode: %s", LOCAL_PR_ARG,
+		  BOOL_TO_STR(__entry->on))
+);
+
+TRACE_EVENT(802154_new_scan_event,
+	TP_PROTO(struct ieee802154_coord_desc *desc),
+	TP_ARGS(desc),
+	TP_STRUCT__entry(
+		__field(__le16, pan_id)
+		__field(__le64, addr)
+		__field(u8, channel)
+		__field(u8, page)
+	),
+	TP_fast_assign(
+		__entry->page = desc->page;
+		__entry->channel = desc->channel;
+		__entry->pan_id = desc->addr.pan_id;
+		__entry->addr = desc->addr.extended_addr;
+	),
+	TP_printk("panid: %u, coord_addr: 0x%llx, page: %u, channel: %u",
+		  __le16_to_cpu(__entry->pan_id), __le64_to_cpu(__entry->addr),
+		  __entry->page, __entry->channel)
+);
+
+DEFINE_EVENT(802154_new_scan_event, 802154_scan_event,
+	TP_PROTO(struct ieee802154_coord_desc *desc),
+	TP_ARGS(desc)
+);
+
+#endif /* !__MAC802154_DRIVER_TRACE || TRACE_HEADER_MULTI_READ */
+
+#undef TRACE_INCLUDE_PATH
+#define TRACE_INCLUDE_PATH .
+#undef TRACE_INCLUDE_FILE
+#define TRACE_INCLUDE_FILE trace
+#include <trace/define_trace.h>