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, 377 insertions, 0 deletions

diff --git a/net/mac80211/led.c b/net/mac80211/led.c
new file mode 100644
index 000000000..b5600d223
--- /dev/null
+++ b/net/mac80211/led.c
@@ -0,0 +1,377 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2006, Johannes Berg <johannes@sipsolutions.net>
+ */
+
+/* just for IFNAMSIZ */
+#include <linux/if.h>
+#include <linux/slab.h>
+#include <linux/export.h>
+#include "led.h"
+
+void ieee80211_led_assoc(struct ieee80211_local *local, bool associated)
+{
+	if (!atomic_read(&local->assoc_led_active))
+		return;
+	if (associated)
+		led_trigger_event(&local->assoc_led, LED_FULL);
+	else
+		led_trigger_event(&local->assoc_led, LED_OFF);
+}
+
+void ieee80211_led_radio(struct ieee80211_local *local, bool enabled)
+{
+	if (!atomic_read(&local->radio_led_active))
+		return;
+	if (enabled)
+		led_trigger_event(&local->radio_led, LED_FULL);
+	else
+		led_trigger_event(&local->radio_led, LED_OFF);
+}
+
+void ieee80211_alloc_led_names(struct ieee80211_local *local)
+{
+	local->rx_led.name = kasprintf(GFP_KERNEL, "%srx",
+				       wiphy_name(local->hw.wiphy));
+	local->tx_led.name = kasprintf(GFP_KERNEL, "%stx",
+				       wiphy_name(local->hw.wiphy));
+	local->assoc_led.name = kasprintf(GFP_KERNEL, "%sassoc",
+					  wiphy_name(local->hw.wiphy));
+	local->radio_led.name = kasprintf(GFP_KERNEL, "%sradio",
+					  wiphy_name(local->hw.wiphy));
+}
+
+void ieee80211_free_led_names(struct ieee80211_local *local)
+{
+	kfree(local->rx_led.name);
+	kfree(local->tx_led.name);
+	kfree(local->assoc_led.name);
+	kfree(local->radio_led.name);
+}
+
+static int ieee80211_tx_led_activate(struct led_classdev *led_cdev)
+{
+	struct ieee80211_local *local = container_of(led_cdev->trigger,
+						     struct ieee80211_local,
+						     tx_led);
+
+	atomic_inc(&local->tx_led_active);
+
+	return 0;
+}
+
+static void ieee80211_tx_led_deactivate(struct led_classdev *led_cdev)
+{
+	struct ieee80211_local *local = container_of(led_cdev->trigger,
+						     struct ieee80211_local,
+						     tx_led);
+
+	atomic_dec(&local->tx_led_active);
+}
+
+static int ieee80211_rx_led_activate(struct led_classdev *led_cdev)
+{
+	struct ieee80211_local *local = container_of(led_cdev->trigger,
+						     struct ieee80211_local,
+						     rx_led);
+
+	atomic_inc(&local->rx_led_active);
+
+	return 0;
+}
+
+static void ieee80211_rx_led_deactivate(struct led_classdev *led_cdev)
+{
+	struct ieee80211_local *local = container_of(led_cdev->trigger,
+						     struct ieee80211_local,
+						     rx_led);
+
+	atomic_dec(&local->rx_led_active);
+}
+
+static int ieee80211_assoc_led_activate(struct led_classdev *led_cdev)
+{
+	struct ieee80211_local *local = container_of(led_cdev->trigger,
+						     struct ieee80211_local,
+						     assoc_led);
+
+	atomic_inc(&local->assoc_led_active);
+
+	return 0;
+}
+
+static void ieee80211_assoc_led_deactivate(struct led_classdev *led_cdev)
+{
+	struct ieee80211_local *local = container_of(led_cdev->trigger,
+						     struct ieee80211_local,
+						     assoc_led);
+
+	atomic_dec(&local->assoc_led_active);
+}
+
+static int ieee80211_radio_led_activate(struct led_classdev *led_cdev)
+{
+	struct ieee80211_local *local = container_of(led_cdev->trigger,
+						     struct ieee80211_local,
+						     radio_led);
+
+	atomic_inc(&local->radio_led_active);
+
+	return 0;
+}
+
+static void ieee80211_radio_led_deactivate(struct led_classdev *led_cdev)
+{
+	struct ieee80211_local *local = container_of(led_cdev->trigger,
+						     struct ieee80211_local,
+						     radio_led);
+
+	atomic_dec(&local->radio_led_active);
+}
+
+static int ieee80211_tpt_led_activate(struct led_classdev *led_cdev)
+{
+	struct ieee80211_local *local = container_of(led_cdev->trigger,
+						     struct ieee80211_local,
+						     tpt_led);
+
+	atomic_inc(&local->tpt_led_active);
+
+	return 0;
+}
+
+static void ieee80211_tpt_led_deactivate(struct led_classdev *led_cdev)
+{
+	struct ieee80211_local *local = container_of(led_cdev->trigger,
+						     struct ieee80211_local,
+						     tpt_led);
+
+	atomic_dec(&local->tpt_led_active);
+}
+
+void ieee80211_led_init(struct ieee80211_local *local)
+{
+	atomic_set(&local->rx_led_active, 0);
+	local->rx_led.activate = ieee80211_rx_led_activate;
+	local->rx_led.deactivate = ieee80211_rx_led_deactivate;
+	if (local->rx_led.name && led_trigger_register(&local->rx_led)) {
+		kfree(local->rx_led.name);
+		local->rx_led.name = NULL;
+	}
+
+	atomic_set(&local->tx_led_active, 0);
+	local->tx_led.activate = ieee80211_tx_led_activate;
+	local->tx_led.deactivate = ieee80211_tx_led_deactivate;
+	if (local->tx_led.name && led_trigger_register(&local->tx_led)) {
+		kfree(local->tx_led.name);
+		local->tx_led.name = NULL;
+	}
+
+	atomic_set(&local->assoc_led_active, 0);
+	local->assoc_led.activate = ieee80211_assoc_led_activate;
+	local->assoc_led.deactivate = ieee80211_assoc_led_deactivate;
+	if (local->assoc_led.name && led_trigger_register(&local->assoc_led)) {
+		kfree(local->assoc_led.name);
+		local->assoc_led.name = NULL;
+	}
+
+	atomic_set(&local->radio_led_active, 0);
+	local->radio_led.activate = ieee80211_radio_led_activate;
+	local->radio_led.deactivate = ieee80211_radio_led_deactivate;
+	if (local->radio_led.name && led_trigger_register(&local->radio_led)) {
+		kfree(local->radio_led.name);
+		local->radio_led.name = NULL;
+	}
+
+	atomic_set(&local->tpt_led_active, 0);
+	if (local->tpt_led_trigger) {
+		local->tpt_led.activate = ieee80211_tpt_led_activate;
+		local->tpt_led.deactivate = ieee80211_tpt_led_deactivate;
+		if (led_trigger_register(&local->tpt_led)) {
+			kfree(local->tpt_led_trigger);
+			local->tpt_led_trigger = NULL;
+		}
+	}
+}
+
+void ieee80211_led_exit(struct ieee80211_local *local)
+{
+	if (local->radio_led.name)
+		led_trigger_unregister(&local->radio_led);
+	if (local->assoc_led.name)
+		led_trigger_unregister(&local->assoc_led);
+	if (local->tx_led.name)
+		led_trigger_unregister(&local->tx_led);
+	if (local->rx_led.name)
+		led_trigger_unregister(&local->rx_led);
+
+	if (local->tpt_led_trigger) {
+		led_trigger_unregister(&local->tpt_led);
+		kfree(local->tpt_led_trigger);
+	}
+}
+
+const char *__ieee80211_get_radio_led_name(struct ieee80211_hw *hw)
+{
+	struct ieee80211_local *local = hw_to_local(hw);
+
+	return local->radio_led.name;
+}
+EXPORT_SYMBOL(__ieee80211_get_radio_led_name);
+
+const char *__ieee80211_get_assoc_led_name(struct ieee80211_hw *hw)
+{
+	struct ieee80211_local *local = hw_to_local(hw);
+
+	return local->assoc_led.name;
+}
+EXPORT_SYMBOL(__ieee80211_get_assoc_led_name);
+
+const char *__ieee80211_get_tx_led_name(struct ieee80211_hw *hw)
+{
+	struct ieee80211_local *local = hw_to_local(hw);
+
+	return local->tx_led.name;
+}
+EXPORT_SYMBOL(__ieee80211_get_tx_led_name);
+
+const char *__ieee80211_get_rx_led_name(struct ieee80211_hw *hw)
+{
+	struct ieee80211_local *local = hw_to_local(hw);
+
+	return local->rx_led.name;
+}
+EXPORT_SYMBOL(__ieee80211_get_rx_led_name);
+
+static unsigned long tpt_trig_traffic(struct ieee80211_local *local,
+				      struct tpt_led_trigger *tpt_trig)
+{
+	unsigned long traffic, delta;
+
+	traffic = tpt_trig->tx_bytes + tpt_trig->rx_bytes;
+
+	delta = traffic - tpt_trig->prev_traffic;
+	tpt_trig->prev_traffic = traffic;
+	return DIV_ROUND_UP(delta, 1024 / 8);
+}
+
+static void tpt_trig_timer(struct timer_list *t)
+{
+	struct tpt_led_trigger *tpt_trig = timer_container_of(tpt_trig, t,
+							      timer);
+	struct ieee80211_local *local = tpt_trig->local;
+	unsigned long on, off, tpt;
+	int i;
+
+	if (!tpt_trig->running)
+		return;
+
+	mod_timer(&tpt_trig->timer, round_jiffies(jiffies + HZ));
+
+	tpt = tpt_trig_traffic(local, tpt_trig);
+
+	/* default to just solid on */
+	on = 1;
+	off = 0;
+
+	for (i = tpt_trig->blink_table_len - 1; i >= 0; i--) {
+		if (tpt_trig->blink_table[i].throughput < 0 ||
+		    tpt > tpt_trig->blink_table[i].throughput) {
+			off = tpt_trig->blink_table[i].blink_time / 2;
+			on = tpt_trig->blink_table[i].blink_time - off;
+			break;
+		}
+	}
+
+	led_trigger_blink(&local->tpt_led, on, off);
+}
+
+const char *
+__ieee80211_create_tpt_led_trigger(struct ieee80211_hw *hw,
+				   unsigned int flags,
+				   const struct ieee80211_tpt_blink *blink_table,
+				   unsigned int blink_table_len)
+{
+	struct ieee80211_local *local = hw_to_local(hw);
+	struct tpt_led_trigger *tpt_trig;
+
+	if (WARN_ON(local->tpt_led_trigger))
+		return NULL;
+
+	tpt_trig = kzalloc_obj(struct tpt_led_trigger);
+	if (!tpt_trig)
+		return NULL;
+
+	snprintf(tpt_trig->name, sizeof(tpt_trig->name),
+		 "%stpt", wiphy_name(local->hw.wiphy));
+
+	local->tpt_led.name = tpt_trig->name;
+
+	tpt_trig->blink_table = blink_table;
+	tpt_trig->blink_table_len = blink_table_len;
+	tpt_trig->want = flags;
+	tpt_trig->local = local;
+
+	timer_setup(&tpt_trig->timer, tpt_trig_timer, 0);
+
+	local->tpt_led_trigger = tpt_trig;
+
+	return tpt_trig->name;
+}
+EXPORT_SYMBOL(__ieee80211_create_tpt_led_trigger);
+
+static void ieee80211_start_tpt_led_trig(struct ieee80211_local *local)
+{
+	struct tpt_led_trigger *tpt_trig = local->tpt_led_trigger;
+
+	if (tpt_trig->running)
+		return;
+
+	/* reset traffic */
+	tpt_trig_traffic(local, tpt_trig);
+	tpt_trig->running = true;
+
+	tpt_trig_timer(&tpt_trig->timer);
+	mod_timer(&tpt_trig->timer, round_jiffies(jiffies + HZ));
+}
+
+static void ieee80211_stop_tpt_led_trig(struct ieee80211_local *local)
+{
+	struct tpt_led_trigger *tpt_trig = local->tpt_led_trigger;
+
+	if (!tpt_trig->running)
+		return;
+
+	tpt_trig->running = false;
+	timer_delete_sync(&tpt_trig->timer);
+
+	led_trigger_event(&local->tpt_led, LED_OFF);
+}
+
+void ieee80211_mod_tpt_led_trig(struct ieee80211_local *local,
+				unsigned int types_on, unsigned int types_off)
+{
+	struct tpt_led_trigger *tpt_trig = local->tpt_led_trigger;
+	bool allowed;
+
+	WARN_ON(types_on & types_off);
+
+	if (!tpt_trig)
+		return;
+
+	tpt_trig->active &= ~types_off;
+	tpt_trig->active |= types_on;
+
+	/*
+	 * Regardless of wanted state, we shouldn't blink when
+	 * the radio is disabled -- this can happen due to some
+	 * code ordering issues with __ieee80211_recalc_idle()
+	 * being called before the radio is started.
+	 */
+	allowed = tpt_trig->active & IEEE80211_TPT_LEDTRIG_FL_RADIO;
+
+	if (!allowed || !(tpt_trig->active & tpt_trig->want))
+		ieee80211_stop_tpt_led_trig(local);
+	else
+		ieee80211_start_tpt_led_trig(local);
+}