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, 248 insertions, 0 deletions

diff --git a/net/mac80211/ocb.c b/net/mac80211/ocb.c
new file mode 100644
index 000000000..e9bf4ba3e
--- /dev/null
+++ b/net/mac80211/ocb.c
@@ -0,0 +1,248 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * OCB mode implementation
+ *
+ * Copyright: (c) 2014 Czech Technical University in Prague
+ *            (c) 2014 Volkswagen Group Research
+ * Copyright (C) 2022 - 2024, 2026 Intel Corporation
+ * Author:    Rostislav Lisovy <rostislav.lisovy@fel.cvut.cz>
+ * Funded by: Volkswagen Group Research
+ */
+
+#include <linux/delay.h>
+#include <linux/if_ether.h>
+#include <linux/skbuff.h>
+#include <linux/if_arp.h>
+#include <linux/etherdevice.h>
+#include <linux/rtnetlink.h>
+#include <net/mac80211.h>
+#include <linux/unaligned.h>
+
+#include "ieee80211_i.h"
+#include "driver-ops.h"
+#include "rate.h"
+
+#define IEEE80211_OCB_HOUSEKEEPING_INTERVAL		(60 * HZ)
+#define IEEE80211_OCB_PEER_INACTIVITY_LIMIT		(240 * HZ)
+#define IEEE80211_OCB_MAX_STA_ENTRIES			128
+
+/**
+ * enum ocb_deferred_task_flags - mac80211 OCB deferred tasks
+ * @OCB_WORK_HOUSEKEEPING: run the periodic OCB housekeeping tasks
+ *
+ * These flags are used in @wrkq_flags field of &struct ieee80211_if_ocb
+ */
+enum ocb_deferred_task_flags {
+	OCB_WORK_HOUSEKEEPING,
+};
+
+void ieee80211_ocb_rx_no_sta(struct ieee80211_sub_if_data *sdata,
+			     const u8 *bssid, const u8 *addr,
+			     u32 supp_rates)
+{
+	struct ieee80211_if_ocb *ifocb = &sdata->u.ocb;
+	struct ieee80211_local *local = sdata->local;
+	struct ieee80211_chanctx_conf *chanctx_conf;
+	struct ieee80211_supported_band *sband;
+	struct sta_info *sta;
+	int band;
+
+	if (!ifocb->joined)
+		return;
+
+	/* XXX: Consider removing the least recently used entry and
+	 *      allow new one to be added.
+	 */
+	if (local->num_sta >= IEEE80211_OCB_MAX_STA_ENTRIES) {
+		net_info_ratelimited("%s: No room for a new OCB STA entry %pM\n",
+				     sdata->name, addr);
+		return;
+	}
+
+	ocb_dbg(sdata, "Adding new OCB station %pM\n", addr);
+
+	rcu_read_lock();
+	chanctx_conf = rcu_dereference(sdata->vif.bss_conf.chanctx_conf);
+	if (WARN_ON_ONCE(!chanctx_conf)) {
+		rcu_read_unlock();
+		return;
+	}
+	band = chanctx_conf->def.chan->band;
+	rcu_read_unlock();
+
+	sta = sta_info_alloc(sdata, addr, GFP_ATOMIC);
+	if (!sta)
+		return;
+
+	/* Add only mandatory rates for now */
+	sband = local->hw.wiphy->bands[band];
+	sta->sta.deflink.supp_rates[band] = ieee80211_mandatory_rates(sband);
+
+	spin_lock(&ifocb->incomplete_lock);
+	list_add(&sta->list, &ifocb->incomplete_stations);
+	spin_unlock(&ifocb->incomplete_lock);
+	wiphy_work_queue(local->hw.wiphy, &sdata->work);
+}
+
+static struct sta_info *ieee80211_ocb_finish_sta(struct sta_info *sta)
+	__acquires(RCU)
+{
+	struct ieee80211_sub_if_data *sdata = sta->sdata;
+	u8 addr[ETH_ALEN];
+
+	memcpy(addr, sta->sta.addr, ETH_ALEN);
+
+	ieee80211_sta_init_nss_bw_capa(&sta->deflink,
+				       &sdata->deflink.conf->chanreq.oper);
+
+	ocb_dbg(sdata, "Adding new IBSS station %pM (dev=%s)\n",
+		addr, sdata->name);
+
+	sta_info_move_state(sta, IEEE80211_STA_AUTH);
+	sta_info_move_state(sta, IEEE80211_STA_ASSOC);
+	sta_info_move_state(sta, IEEE80211_STA_AUTHORIZED);
+
+	rate_control_rate_init(&sta->deflink);
+
+	/* If it fails, maybe we raced another insertion? */
+	if (sta_info_insert_rcu(sta))
+		return sta_info_get(sdata, addr);
+	return sta;
+}
+
+static void ieee80211_ocb_housekeeping(struct ieee80211_sub_if_data *sdata)
+{
+	struct ieee80211_if_ocb *ifocb = &sdata->u.ocb;
+
+	ocb_dbg(sdata, "Running ocb housekeeping\n");
+
+	ieee80211_sta_expire(sdata, IEEE80211_OCB_PEER_INACTIVITY_LIMIT);
+
+	mod_timer(&ifocb->housekeeping_timer,
+		  round_jiffies(jiffies + IEEE80211_OCB_HOUSEKEEPING_INTERVAL));
+}
+
+void ieee80211_ocb_work(struct ieee80211_sub_if_data *sdata)
+{
+	struct ieee80211_if_ocb *ifocb = &sdata->u.ocb;
+	struct sta_info *sta;
+
+	lockdep_assert_wiphy(sdata->local->hw.wiphy);
+
+	if (ifocb->joined != true)
+		return;
+
+	spin_lock_bh(&ifocb->incomplete_lock);
+	while (!list_empty(&ifocb->incomplete_stations)) {
+		sta = list_first_entry(&ifocb->incomplete_stations,
+				       struct sta_info, list);
+		list_del(&sta->list);
+		spin_unlock_bh(&ifocb->incomplete_lock);
+
+		ieee80211_ocb_finish_sta(sta);
+		rcu_read_unlock();
+		spin_lock_bh(&ifocb->incomplete_lock);
+	}
+	spin_unlock_bh(&ifocb->incomplete_lock);
+
+	if (test_and_clear_bit(OCB_WORK_HOUSEKEEPING, &ifocb->wrkq_flags))
+		ieee80211_ocb_housekeeping(sdata);
+}
+
+static void ieee80211_ocb_housekeeping_timer(struct timer_list *t)
+{
+	struct ieee80211_sub_if_data *sdata =
+		timer_container_of(sdata, t, u.ocb.housekeeping_timer);
+	struct ieee80211_local *local = sdata->local;
+	struct ieee80211_if_ocb *ifocb = &sdata->u.ocb;
+
+	set_bit(OCB_WORK_HOUSEKEEPING, &ifocb->wrkq_flags);
+
+	wiphy_work_queue(local->hw.wiphy, &sdata->work);
+}
+
+void ieee80211_ocb_setup_sdata(struct ieee80211_sub_if_data *sdata)
+{
+	struct ieee80211_if_ocb *ifocb = &sdata->u.ocb;
+
+	timer_setup(&ifocb->housekeeping_timer,
+		    ieee80211_ocb_housekeeping_timer, 0);
+	INIT_LIST_HEAD(&ifocb->incomplete_stations);
+	spin_lock_init(&ifocb->incomplete_lock);
+}
+
+int ieee80211_ocb_join(struct ieee80211_sub_if_data *sdata,
+		       struct ocb_setup *setup)
+{
+	struct ieee80211_chan_req chanreq = { .oper = setup->chandef };
+	struct ieee80211_local *local = sdata->local;
+	struct ieee80211_if_ocb *ifocb = &sdata->u.ocb;
+	u64 changed = BSS_CHANGED_OCB | BSS_CHANGED_BSSID;
+	int err;
+
+	lockdep_assert_wiphy(sdata->local->hw.wiphy);
+
+	if (ifocb->joined == true)
+		return -EINVAL;
+
+	sdata->deflink.operating_11g_mode = true;
+	sdata->deflink.smps_mode = IEEE80211_SMPS_OFF;
+	sdata->deflink.needed_rx_chains = sdata->local->rx_chains;
+
+	err = ieee80211_link_use_channel(&sdata->deflink, &chanreq,
+					 IEEE80211_CHANCTX_SHARED);
+	if (err)
+		return err;
+
+	ieee80211_bss_info_change_notify(sdata, changed);
+
+	ifocb->joined = true;
+
+	set_bit(OCB_WORK_HOUSEKEEPING, &ifocb->wrkq_flags);
+	wiphy_work_queue(local->hw.wiphy, &sdata->work);
+
+	netif_carrier_on(sdata->dev);
+	return 0;
+}
+
+int ieee80211_ocb_leave(struct ieee80211_sub_if_data *sdata)
+{
+	struct ieee80211_if_ocb *ifocb = &sdata->u.ocb;
+	struct ieee80211_local *local = sdata->local;
+	struct sta_info *sta;
+
+	lockdep_assert_wiphy(sdata->local->hw.wiphy);
+
+	ifocb->joined = false;
+	sta_info_flush(sdata, -1);
+
+	spin_lock_bh(&ifocb->incomplete_lock);
+	while (!list_empty(&ifocb->incomplete_stations)) {
+		sta = list_first_entry(&ifocb->incomplete_stations,
+				       struct sta_info, list);
+		list_del(&sta->list);
+		spin_unlock_bh(&ifocb->incomplete_lock);
+
+		sta_info_free(local, sta);
+		spin_lock_bh(&ifocb->incomplete_lock);
+	}
+	spin_unlock_bh(&ifocb->incomplete_lock);
+
+	netif_carrier_off(sdata->dev);
+	clear_bit(SDATA_STATE_OFFCHANNEL, &sdata->state);
+	ieee80211_bss_info_change_notify(sdata, BSS_CHANGED_OCB);
+
+	ieee80211_link_release_channel(&sdata->deflink);
+
+	skb_queue_purge(&sdata->skb_queue);
+
+	timer_delete_sync(&sdata->u.ocb.housekeeping_timer);
+	/* If the timer fired while we waited for it, it will have
+	 * requeued the work. Now the work will be running again
+	 * but will not rearm the timer again because it checks
+	 * whether we are connected to the network or not -- at this
+	 * point we shouldn't be anymore.
+	 */
+
+	return 0;
+}