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, 246 insertions, 0 deletions

diff --git a/drivers/net/wireguard/timers.c b/drivers/net/wireguard/timers.c
new file mode 100644
index 000000000..4016a3065
--- /dev/null
+++ b/drivers/net/wireguard/timers.c
@@ -0,0 +1,246 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ */
+
+#include "timers.h"
+#include "device.h"
+#include "peer.h"
+#include "queueing.h"
+#include "socket.h"
+
+/*
+ * - Timer for retransmitting the handshake if we don't hear back after
+ * `REKEY_TIMEOUT + jitter` ms.
+ *
+ * - Timer for sending empty packet if we have received a packet but after have
+ * not sent one for `KEEPALIVE_TIMEOUT` ms.
+ *
+ * - Timer for initiating new handshake if we have sent a packet but after have
+ * not received one (even empty) for `(KEEPALIVE_TIMEOUT + REKEY_TIMEOUT) +
+ * jitter` ms.
+ *
+ * - Timer for zeroing out all ephemeral keys after `(REJECT_AFTER_TIME * 3)` ms
+ * if no new keys have been received.
+ *
+ * - Timer for, if enabled, sending an empty authenticated packet every user-
+ * specified seconds.
+ */
+
+static inline void mod_peer_timer(struct wg_peer *peer,
+				  struct timer_list *timer,
+				  unsigned long expires)
+{
+	rcu_read_lock_bh();
+	if (likely(netif_running(peer->device->dev) &&
+		   !READ_ONCE(peer->is_dead)))
+		mod_timer(timer, expires);
+	rcu_read_unlock_bh();
+}
+
+static void wg_expired_retransmit_handshake(struct timer_list *timer)
+{
+	struct wg_peer *peer = timer_container_of(peer, timer,
+						  timer_retransmit_handshake);
+
+	if (peer->timer_handshake_attempts > MAX_TIMER_HANDSHAKES) {
+		pr_debug("%s: Handshake for peer %llu (%pISpfsc) did not complete after %d attempts, giving up\n",
+			 peer->device->dev->name, peer->internal_id,
+			 &peer->endpoint.addr, (int)MAX_TIMER_HANDSHAKES + 2);
+
+		timer_delete(&peer->timer_send_keepalive);
+		/* We drop all packets without a keypair and don't try again,
+		 * if we try unsuccessfully for too long to make a handshake.
+		 */
+		wg_packet_purge_staged_packets(peer);
+
+		/* We set a timer for destroying any residue that might be left
+		 * of a partial exchange.
+		 */
+		if (!timer_pending(&peer->timer_zero_key_material))
+			mod_peer_timer(peer, &peer->timer_zero_key_material,
+				       jiffies + REJECT_AFTER_TIME * 3 * HZ);
+	} else {
+		++peer->timer_handshake_attempts;
+		pr_debug("%s: Handshake for peer %llu (%pISpfsc) did not complete after %d seconds, retrying (try %d)\n",
+			 peer->device->dev->name, peer->internal_id,
+			 &peer->endpoint.addr, (int)REKEY_TIMEOUT,
+			 peer->timer_handshake_attempts + 1);
+
+		/* We clear the endpoint address src address, in case this is
+		 * the cause of trouble.
+		 */
+		wg_socket_clear_peer_endpoint_src(peer);
+
+		wg_packet_send_queued_handshake_initiation(peer, true);
+	}
+}
+
+static void wg_expired_send_keepalive(struct timer_list *timer)
+{
+	struct wg_peer *peer = timer_container_of(peer, timer,
+						  timer_send_keepalive);
+
+	wg_packet_send_keepalive(peer);
+	if (peer->timer_need_another_keepalive) {
+		peer->timer_need_another_keepalive = false;
+		mod_peer_timer(peer, &peer->timer_send_keepalive,
+			       jiffies + KEEPALIVE_TIMEOUT * HZ);
+	}
+}
+
+static void wg_expired_new_handshake(struct timer_list *timer)
+{
+	struct wg_peer *peer = timer_container_of(peer, timer,
+						  timer_new_handshake);
+
+	pr_debug("%s: Retrying handshake with peer %llu (%pISpfsc) because we stopped hearing back after %d seconds\n",
+		 peer->device->dev->name, peer->internal_id,
+		 &peer->endpoint.addr, (int)(KEEPALIVE_TIMEOUT + REKEY_TIMEOUT));
+	/* We clear the endpoint address src address, in case this is the cause
+	 * of trouble.
+	 */
+	wg_socket_clear_peer_endpoint_src(peer);
+	wg_packet_send_queued_handshake_initiation(peer, false);
+}
+
+static void wg_expired_zero_key_material(struct timer_list *timer)
+{
+	struct wg_peer *peer = timer_container_of(peer, timer,
+						  timer_zero_key_material);
+
+	rcu_read_lock_bh();
+	if (!READ_ONCE(peer->is_dead)) {
+		wg_peer_get(peer);
+		if (!queue_work(peer->device->handshake_send_wq,
+				&peer->clear_peer_work))
+			/* If the work was already on the queue, we want to drop
+			 * the extra reference.
+			 */
+			wg_peer_put(peer);
+	}
+	rcu_read_unlock_bh();
+}
+
+static void wg_queued_expired_zero_key_material(struct work_struct *work)
+{
+	struct wg_peer *peer = container_of(work, struct wg_peer,
+					    clear_peer_work);
+
+	pr_debug("%s: Zeroing out all keys for peer %llu (%pISpfsc), since we haven't received a new one in %d seconds\n",
+		 peer->device->dev->name, peer->internal_id,
+		 &peer->endpoint.addr, (int)REJECT_AFTER_TIME * 3);
+	wg_noise_handshake_clear(&peer->handshake);
+	wg_noise_keypairs_clear(&peer->keypairs);
+	wg_peer_put(peer);
+}
+
+static void wg_expired_send_persistent_keepalive(struct timer_list *timer)
+{
+	struct wg_peer *peer = timer_container_of(peer, timer,
+						  timer_persistent_keepalive);
+
+	if (likely(peer->persistent_keepalive_interval))
+		wg_packet_send_keepalive(peer);
+}
+
+/* Should be called after an authenticated data packet is sent. */
+void wg_timers_data_sent(struct wg_peer *peer)
+{
+	if (!timer_pending(&peer->timer_new_handshake))
+		mod_peer_timer(peer, &peer->timer_new_handshake,
+			jiffies + (KEEPALIVE_TIMEOUT + REKEY_TIMEOUT) * HZ +
+			get_random_u32_below(REKEY_TIMEOUT_JITTER_MAX_JIFFIES));
+}
+
+/* Should be called after an authenticated data packet is received. */
+void wg_timers_data_received(struct wg_peer *peer)
+{
+	if (likely(netif_running(peer->device->dev))) {
+		if (!timer_pending(&peer->timer_send_keepalive))
+			mod_peer_timer(peer, &peer->timer_send_keepalive,
+				       jiffies + KEEPALIVE_TIMEOUT * HZ);
+		else
+			peer->timer_need_another_keepalive = true;
+	}
+}
+
+/* Should be called after any type of authenticated packet is sent, whether
+ * keepalive, data, or handshake.
+ */
+void wg_timers_any_authenticated_packet_sent(struct wg_peer *peer)
+{
+	timer_delete(&peer->timer_send_keepalive);
+}
+
+/* Should be called after any type of authenticated packet is received, whether
+ * keepalive, data, or handshake.
+ */
+void wg_timers_any_authenticated_packet_received(struct wg_peer *peer)
+{
+	timer_delete(&peer->timer_new_handshake);
+}
+
+/* Should be called after a handshake initiation message is sent. */
+void wg_timers_handshake_initiated(struct wg_peer *peer)
+{
+	mod_peer_timer(peer, &peer->timer_retransmit_handshake,
+		       jiffies + REKEY_TIMEOUT * HZ +
+		       get_random_u32_below(REKEY_TIMEOUT_JITTER_MAX_JIFFIES));
+}
+
+/* Should be called after a handshake response message is received and processed
+ * or when getting key confirmation via the first data message.
+ */
+void wg_timers_handshake_complete(struct wg_peer *peer)
+{
+	timer_delete(&peer->timer_retransmit_handshake);
+	peer->timer_handshake_attempts = 0;
+	peer->sent_lastminute_handshake = false;
+	ktime_get_real_ts64(&peer->walltime_last_handshake);
+}
+
+/* Should be called after an ephemeral key is created, which is before sending a
+ * handshake response or after receiving a handshake response.
+ */
+void wg_timers_session_derived(struct wg_peer *peer)
+{
+	mod_peer_timer(peer, &peer->timer_zero_key_material,
+		       jiffies + REJECT_AFTER_TIME * 3 * HZ);
+}
+
+/* Should be called before a packet with authentication, whether
+ * keepalive, data, or handshakem is sent, or after one is received.
+ */
+void wg_timers_any_authenticated_packet_traversal(struct wg_peer *peer)
+{
+	if (peer->persistent_keepalive_interval)
+		mod_peer_timer(peer, &peer->timer_persistent_keepalive,
+			jiffies + peer->persistent_keepalive_interval * HZ);
+}
+
+void wg_timers_init(struct wg_peer *peer)
+{
+	timer_setup(&peer->timer_retransmit_handshake,
+		    wg_expired_retransmit_handshake, 0);
+	timer_setup(&peer->timer_send_keepalive, wg_expired_send_keepalive, 0);
+	timer_setup(&peer->timer_new_handshake, wg_expired_new_handshake, 0);
+	timer_setup(&peer->timer_zero_key_material,
+		    wg_expired_zero_key_material, 0);
+	timer_setup(&peer->timer_persistent_keepalive,
+		    wg_expired_send_persistent_keepalive, 0);
+	INIT_WORK(&peer->clear_peer_work, wg_queued_expired_zero_key_material);
+	peer->timer_handshake_attempts = 0;
+	peer->sent_lastminute_handshake = false;
+	peer->timer_need_another_keepalive = false;
+}
+
+void wg_timers_stop(struct wg_peer *peer)
+{
+	timer_delete_sync(&peer->timer_retransmit_handshake);
+	timer_delete_sync(&peer->timer_send_keepalive);
+	timer_delete_sync(&peer->timer_new_handshake);
+	timer_delete_sync(&peer->timer_zero_key_material);
+	timer_delete_sync(&peer->timer_persistent_keepalive);
+	flush_work(&peer->clear_peer_work);
+}