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, 144 insertions, 0 deletions

diff --git a/net/mac802154/mac_cmd.c b/net/mac802154/mac_cmd.c
new file mode 100644
index 000000000..8ea5b6402
--- /dev/null
+++ b/net/mac802154/mac_cmd.c
@@ -0,0 +1,144 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * MAC commands interface
+ *
+ * Copyright 2007-2012 Siemens AG
+ *
+ * Written by:
+ * Sergey Lapin <slapin@ossfans.org>
+ * Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
+ * Alexander Smirnov <alex.bluesman.smirnov@gmail.com>
+ */
+
+#include <linux/skbuff.h>
+#include <linux/if_arp.h>
+#include <linux/ieee802154.h>
+
+#include <net/ieee802154_netdev.h>
+#include <net/cfg802154.h>
+#include <net/mac802154.h>
+
+#include "ieee802154_i.h"
+#include "driver-ops.h"
+
+static int mac802154_mlme_start_req(struct net_device *dev,
+				    struct ieee802154_addr *addr,
+				    u8 channel, u8 page,
+				    u8 bcn_ord, u8 sf_ord,
+				    u8 pan_coord, u8 blx,
+				    u8 coord_realign)
+{
+	struct ieee802154_llsec_params params;
+	int changed = 0;
+
+	ASSERT_RTNL();
+
+	BUG_ON(addr->mode != IEEE802154_ADDR_SHORT);
+
+	dev->ieee802154_ptr->pan_id = addr->pan_id;
+	dev->ieee802154_ptr->short_addr = addr->short_addr;
+	mac802154_dev_set_page_channel(dev, page, channel);
+
+	params.pan_id = addr->pan_id;
+	changed |= IEEE802154_LLSEC_PARAM_PAN_ID;
+
+	params.hwaddr = ieee802154_devaddr_from_raw(dev->dev_addr);
+	changed |= IEEE802154_LLSEC_PARAM_HWADDR;
+
+	params.coord_hwaddr = params.hwaddr;
+	changed |= IEEE802154_LLSEC_PARAM_COORD_HWADDR;
+
+	params.coord_shortaddr = addr->short_addr;
+	changed |= IEEE802154_LLSEC_PARAM_COORD_SHORTADDR;
+
+	return mac802154_set_params(dev, &params, changed);
+}
+
+static int mac802154_set_mac_params(struct net_device *dev,
+				    const struct ieee802154_mac_params *params)
+{
+	struct ieee802154_sub_if_data *sdata = IEEE802154_DEV_TO_SUB_IF(dev);
+	struct ieee802154_local *local = sdata->local;
+	struct wpan_dev *wpan_dev = &sdata->wpan_dev;
+	int ret;
+
+	ASSERT_RTNL();
+
+	/* PHY */
+	wpan_dev->wpan_phy->transmit_power = params->transmit_power;
+	wpan_dev->wpan_phy->cca = params->cca;
+	wpan_dev->wpan_phy->cca_ed_level = params->cca_ed_level;
+
+	/* MAC */
+	wpan_dev->min_be = params->min_be;
+	wpan_dev->max_be = params->max_be;
+	wpan_dev->csma_retries = params->csma_retries;
+	wpan_dev->frame_retries = params->frame_retries;
+	wpan_dev->lbt = params->lbt;
+
+	if (local->hw.phy->flags & WPAN_PHY_FLAG_TXPOWER) {
+		ret = drv_set_tx_power(local, params->transmit_power);
+		if (ret < 0)
+			return ret;
+	}
+
+	if (local->hw.phy->flags & WPAN_PHY_FLAG_CCA_MODE) {
+		ret = drv_set_cca_mode(local, &params->cca);
+		if (ret < 0)
+			return ret;
+	}
+
+	if (local->hw.phy->flags & WPAN_PHY_FLAG_CCA_ED_LEVEL) {
+		ret = drv_set_cca_ed_level(local, params->cca_ed_level);
+		if (ret < 0)
+			return ret;
+	}
+
+	return 0;
+}
+
+static void mac802154_get_mac_params(struct net_device *dev,
+				     struct ieee802154_mac_params *params)
+{
+	struct ieee802154_sub_if_data *sdata = IEEE802154_DEV_TO_SUB_IF(dev);
+	struct wpan_dev *wpan_dev = &sdata->wpan_dev;
+
+	ASSERT_RTNL();
+
+	/* PHY */
+	params->transmit_power = wpan_dev->wpan_phy->transmit_power;
+	params->cca = wpan_dev->wpan_phy->cca;
+	params->cca_ed_level = wpan_dev->wpan_phy->cca_ed_level;
+
+	/* MAC */
+	params->min_be = wpan_dev->min_be;
+	params->max_be = wpan_dev->max_be;
+	params->csma_retries = wpan_dev->csma_retries;
+	params->frame_retries = wpan_dev->frame_retries;
+	params->lbt = wpan_dev->lbt;
+}
+
+static const struct ieee802154_llsec_ops mac802154_llsec_ops = {
+	.get_params = mac802154_get_params,
+	.set_params = mac802154_set_params,
+	.add_key = mac802154_add_key,
+	.del_key = mac802154_del_key,
+	.add_dev = mac802154_add_dev,
+	.del_dev = mac802154_del_dev,
+	.add_devkey = mac802154_add_devkey,
+	.del_devkey = mac802154_del_devkey,
+	.add_seclevel = mac802154_add_seclevel,
+	.del_seclevel = mac802154_del_seclevel,
+	.lock_table = mac802154_lock_table,
+	.get_table = mac802154_get_table,
+	.unlock_table = mac802154_unlock_table,
+};
+
+struct ieee802154_mlme_ops mac802154_mlme_wpan = {
+	.start_req = mac802154_mlme_start_req,
+
+	.llsec = &mac802154_llsec_ops,
+
+	.set_mac_params = mac802154_set_mac_params,
+	.get_mac_params = mac802154_get_mac_params,
+};