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, 86 insertions, 0 deletions

diff --git a/net/mac80211/led.h b/net/mac80211/led.h
new file mode 100644
index 000000000..d25f13346
--- /dev/null
+++ b/net/mac80211/led.h
@@ -0,0 +1,86 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright 2006, Johannes Berg <johannes@sipsolutions.net>
+ */
+
+#include <linux/list.h>
+#include <linux/spinlock.h>
+#include <linux/leds.h>
+#include "ieee80211_i.h"
+
+#define MAC80211_BLINK_DELAY 50 /* ms */
+
+static inline void ieee80211_led_rx(struct ieee80211_local *local)
+{
+#ifdef CONFIG_MAC80211_LEDS
+	if (!atomic_read(&local->rx_led_active))
+		return;
+	led_trigger_blink_oneshot(&local->rx_led, MAC80211_BLINK_DELAY, MAC80211_BLINK_DELAY, 0);
+#endif
+}
+
+static inline void ieee80211_led_tx(struct ieee80211_local *local)
+{
+#ifdef CONFIG_MAC80211_LEDS
+	if (!atomic_read(&local->tx_led_active))
+		return;
+	led_trigger_blink_oneshot(&local->tx_led, MAC80211_BLINK_DELAY, MAC80211_BLINK_DELAY, 0);
+#endif
+}
+
+#ifdef CONFIG_MAC80211_LEDS
+void ieee80211_led_assoc(struct ieee80211_local *local,
+			 bool associated);
+void ieee80211_led_radio(struct ieee80211_local *local,
+			 bool enabled);
+void ieee80211_alloc_led_names(struct ieee80211_local *local);
+void ieee80211_free_led_names(struct ieee80211_local *local);
+void ieee80211_led_init(struct ieee80211_local *local);
+void ieee80211_led_exit(struct ieee80211_local *local);
+void ieee80211_mod_tpt_led_trig(struct ieee80211_local *local,
+				unsigned int types_on, unsigned int types_off);
+#else
+static inline void ieee80211_led_assoc(struct ieee80211_local *local,
+				       bool associated)
+{
+}
+static inline void ieee80211_led_radio(struct ieee80211_local *local,
+				       bool enabled)
+{
+}
+static inline void ieee80211_alloc_led_names(struct ieee80211_local *local)
+{
+}
+static inline void ieee80211_free_led_names(struct ieee80211_local *local)
+{
+}
+static inline void ieee80211_led_init(struct ieee80211_local *local)
+{
+}
+static inline void ieee80211_led_exit(struct ieee80211_local *local)
+{
+}
+static inline void ieee80211_mod_tpt_led_trig(struct ieee80211_local *local,
+					      unsigned int types_on,
+					      unsigned int types_off)
+{
+}
+#endif
+
+static inline void
+ieee80211_tpt_led_trig_tx(struct ieee80211_local *local, int bytes)
+{
+#ifdef CONFIG_MAC80211_LEDS
+	if (atomic_read(&local->tpt_led_active))
+		local->tpt_led_trigger->tx_bytes += bytes;
+#endif
+}
+
+static inline void
+ieee80211_tpt_led_trig_rx(struct ieee80211_local *local, int bytes)
+{
+#ifdef CONFIG_MAC80211_LEDS
+	if (atomic_read(&local->tpt_led_active))
+		local->tpt_led_trigger->rx_bytes += bytes;
+#endif
+}