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, 388 insertions, 0 deletions

diff --git a/net/bluetooth/eir.c b/net/bluetooth/eir.c
new file mode 100644
index 000000000..1de5f9df6
--- /dev/null
+++ b/net/bluetooth/eir.c
@@ -0,0 +1,388 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * BlueZ - Bluetooth protocol stack for Linux
+ *
+ * Copyright (C) 2021 Intel Corporation
+ */
+
+#include <net/bluetooth/bluetooth.h>
+#include <net/bluetooth/hci_core.h>
+#include <net/bluetooth/mgmt.h>
+
+#include "eir.h"
+
+#define PNP_INFO_SVCLASS_ID		0x1200
+
+u8 eir_append_local_name(struct hci_dev *hdev, u8 *ptr, u8 ad_len)
+{
+	size_t short_len;
+	size_t complete_len;
+
+	/* no space left for name (+ type + len) */
+	if ((max_adv_len(hdev) - ad_len) < HCI_MAX_SHORT_NAME_LENGTH + 2)
+		return ad_len;
+
+	/* use complete name if present and fits */
+	complete_len = strnlen(hdev->dev_name, sizeof(hdev->dev_name));
+	if (complete_len && complete_len <= HCI_MAX_SHORT_NAME_LENGTH)
+		return eir_append_data(ptr, ad_len, EIR_NAME_COMPLETE,
+				       hdev->dev_name, complete_len);
+
+	/* use short name if present */
+	short_len = strnlen(hdev->short_name, sizeof(hdev->short_name));
+	if (short_len)
+		return eir_append_data(ptr, ad_len, EIR_NAME_SHORT,
+				       hdev->short_name,
+				       short_len);
+
+	/* use shortened full name if present, we already know that name
+	 * is longer then HCI_MAX_SHORT_NAME_LENGTH
+	 */
+	if (complete_len)
+		return eir_append_data(ptr, ad_len, EIR_NAME_SHORT,
+				       hdev->dev_name,
+				       HCI_MAX_SHORT_NAME_LENGTH);
+
+	return ad_len;
+}
+
+u8 eir_append_appearance(struct hci_dev *hdev, u8 *ptr, u8 ad_len)
+{
+	return eir_append_le16(ptr, ad_len, EIR_APPEARANCE, hdev->appearance);
+}
+
+u8 eir_append_service_data(u8 *eir, u16 eir_len, u16 uuid, u8 *data,
+			   u8 data_len)
+{
+	eir[eir_len++] = sizeof(u8) + sizeof(uuid) + data_len;
+	eir[eir_len++] = EIR_SERVICE_DATA;
+	put_unaligned_le16(uuid, &eir[eir_len]);
+	eir_len += sizeof(uuid);
+	memcpy(&eir[eir_len], data, data_len);
+	eir_len += data_len;
+
+	return eir_len;
+}
+
+static u8 *create_uuid16_list(struct hci_dev *hdev, u8 *data, ptrdiff_t len)
+{
+	u8 *ptr = data, *uuids_start = NULL;
+	struct bt_uuid *uuid;
+
+	if (len < 4)
+		return ptr;
+
+	list_for_each_entry(uuid, &hdev->uuids, list) {
+		u16 uuid16;
+
+		if (uuid->size != 16)
+			continue;
+
+		uuid16 = get_unaligned_le16(&uuid->uuid[12]);
+		if (uuid16 < 0x1100)
+			continue;
+
+		if (uuid16 == PNP_INFO_SVCLASS_ID)
+			continue;
+
+		if (!uuids_start) {
+			uuids_start = ptr;
+			uuids_start[0] = 1;
+			uuids_start[1] = EIR_UUID16_ALL;
+			ptr += 2;
+		}
+
+		/* Stop if not enough space to put next UUID */
+		if ((ptr - data) + sizeof(u16) > len) {
+			uuids_start[1] = EIR_UUID16_SOME;
+			break;
+		}
+
+		*ptr++ = (uuid16 & 0x00ff);
+		*ptr++ = (uuid16 & 0xff00) >> 8;
+		uuids_start[0] += sizeof(uuid16);
+	}
+
+	return ptr;
+}
+
+static u8 *create_uuid32_list(struct hci_dev *hdev, u8 *data, ptrdiff_t len)
+{
+	u8 *ptr = data, *uuids_start = NULL;
+	struct bt_uuid *uuid;
+
+	if (len < 6)
+		return ptr;
+
+	list_for_each_entry(uuid, &hdev->uuids, list) {
+		if (uuid->size != 32)
+			continue;
+
+		if (!uuids_start) {
+			uuids_start = ptr;
+			uuids_start[0] = 1;
+			uuids_start[1] = EIR_UUID32_ALL;
+			ptr += 2;
+		}
+
+		/* Stop if not enough space to put next UUID */
+		if ((ptr - data) + sizeof(u32) > len) {
+			uuids_start[1] = EIR_UUID32_SOME;
+			break;
+		}
+
+		memcpy(ptr, &uuid->uuid[12], sizeof(u32));
+		ptr += sizeof(u32);
+		uuids_start[0] += sizeof(u32);
+	}
+
+	return ptr;
+}
+
+static u8 *create_uuid128_list(struct hci_dev *hdev, u8 *data, ptrdiff_t len)
+{
+	u8 *ptr = data, *uuids_start = NULL;
+	struct bt_uuid *uuid;
+
+	if (len < 18)
+		return ptr;
+
+	list_for_each_entry(uuid, &hdev->uuids, list) {
+		if (uuid->size != 128)
+			continue;
+
+		if (!uuids_start) {
+			uuids_start = ptr;
+			uuids_start[0] = 1;
+			uuids_start[1] = EIR_UUID128_ALL;
+			ptr += 2;
+		}
+
+		/* Stop if not enough space to put next UUID */
+		if ((ptr - data) + 16 > len) {
+			uuids_start[1] = EIR_UUID128_SOME;
+			break;
+		}
+
+		memcpy(ptr, uuid->uuid, 16);
+		ptr += 16;
+		uuids_start[0] += 16;
+	}
+
+	return ptr;
+}
+
+void eir_create(struct hci_dev *hdev, u8 *data)
+{
+	u8 *ptr = data;
+	size_t name_len;
+
+	name_len = strnlen(hdev->dev_name, sizeof(hdev->dev_name));
+
+	if (name_len > 0) {
+		/* EIR Data type */
+		if (name_len > 48) {
+			name_len = 48;
+			ptr[1] = EIR_NAME_SHORT;
+		} else {
+			ptr[1] = EIR_NAME_COMPLETE;
+		}
+
+		/* EIR Data length */
+		ptr[0] = name_len + 1;
+
+		memcpy(ptr + 2, hdev->dev_name, name_len);
+
+		ptr += (name_len + 2);
+	}
+
+	if (hdev->inq_tx_power != HCI_TX_POWER_INVALID) {
+		ptr[0] = 2;
+		ptr[1] = EIR_TX_POWER;
+		ptr[2] = (u8)hdev->inq_tx_power;
+
+		ptr += 3;
+	}
+
+	if (hdev->devid_source > 0) {
+		ptr[0] = 9;
+		ptr[1] = EIR_DEVICE_ID;
+
+		put_unaligned_le16(hdev->devid_source, ptr + 2);
+		put_unaligned_le16(hdev->devid_vendor, ptr + 4);
+		put_unaligned_le16(hdev->devid_product, ptr + 6);
+		put_unaligned_le16(hdev->devid_version, ptr + 8);
+
+		ptr += 10;
+	}
+
+	ptr = create_uuid16_list(hdev, ptr, HCI_MAX_EIR_LENGTH - (ptr - data));
+	ptr = create_uuid32_list(hdev, ptr, HCI_MAX_EIR_LENGTH - (ptr - data));
+	ptr = create_uuid128_list(hdev, ptr, HCI_MAX_EIR_LENGTH - (ptr - data));
+}
+
+u8 eir_create_per_adv_data(struct hci_dev *hdev, u8 instance, u8 *ptr)
+{
+	struct adv_info *adv = NULL;
+	u8 ad_len = 0;
+
+	/* Return 0 when the current instance identifier is invalid. */
+	if (instance) {
+		adv = hci_find_adv_instance(hdev, instance);
+		if (!adv)
+			return 0;
+	}
+
+	if (adv) {
+		memcpy(ptr, adv->per_adv_data, adv->per_adv_data_len);
+		ad_len += adv->per_adv_data_len;
+		ptr += adv->per_adv_data_len;
+	}
+
+	return ad_len;
+}
+
+u8 eir_create_adv_data(struct hci_dev *hdev, u8 instance, u8 *ptr, u8 size)
+{
+	struct adv_info *adv = NULL;
+	u8 ad_len = 0, flags = 0;
+	u32 instance_flags;
+
+	/* Return 0 when the current instance identifier is invalid. */
+	if (instance) {
+		adv = hci_find_adv_instance(hdev, instance);
+		if (!adv)
+			return 0;
+	}
+
+	instance_flags = hci_adv_instance_flags(hdev, instance);
+
+	/* If instance already has the flags set skip adding it once
+	 * again.
+	 */
+	if (adv && eir_get_data(adv->adv_data, adv->adv_data_len, EIR_FLAGS,
+				NULL))
+		goto skip_flags;
+
+	/* The Add Advertising command allows userspace to set both the general
+	 * and limited discoverable flags.
+	 */
+	if (instance_flags & MGMT_ADV_FLAG_DISCOV)
+		flags |= LE_AD_GENERAL;
+
+	if (instance_flags & MGMT_ADV_FLAG_LIMITED_DISCOV)
+		flags |= LE_AD_LIMITED;
+
+	if (!hci_dev_test_flag(hdev, HCI_BREDR_ENABLED))
+		flags |= LE_AD_NO_BREDR;
+
+	if (flags || (instance_flags & MGMT_ADV_FLAG_MANAGED_FLAGS)) {
+		/* If a discovery flag wasn't provided, simply use the global
+		 * settings.
+		 */
+		if (!flags)
+			flags |= mgmt_get_adv_discov_flags(hdev);
+
+		/* Only add the "Flags" if it fits together with the instance
+		 * advertising data; drop it rather than overflow the buffer.
+		 */
+		if (flags &&
+		    (ad_len + eir_precalc_len(1) +
+		     (adv ? adv->adv_data_len : 0) <= size)) {
+			ptr[0] = 0x02;
+			ptr[1] = EIR_FLAGS;
+			ptr[2] = flags;
+
+			ad_len += 3;
+			ptr += 3;
+		}
+	}
+
+skip_flags:
+	if (adv) {
+		memcpy(ptr, adv->adv_data, adv->adv_data_len);
+		ad_len += adv->adv_data_len;
+		ptr += adv->adv_data_len;
+	}
+
+	if (instance_flags & MGMT_ADV_FLAG_TX_POWER) {
+		s8 adv_tx_power;
+
+		if (ext_adv_capable(hdev)) {
+			if (adv)
+				adv_tx_power = adv->tx_power;
+			else
+				adv_tx_power = hdev->adv_tx_power;
+		} else {
+			adv_tx_power = hdev->adv_tx_power;
+		}
+
+		/* Provide Tx Power only if we can provide a valid value for it */
+		if (adv_tx_power != HCI_TX_POWER_INVALID &&
+		    (ad_len + eir_precalc_len(1) <= size)) {
+			ptr[0] = 0x02;
+			ptr[1] = EIR_TX_POWER;
+			ptr[2] = (u8)adv_tx_power;
+
+			ad_len += 3;
+			ptr += 3;
+		}
+	}
+
+	return ad_len;
+}
+
+static u8 create_default_scan_rsp(struct hci_dev *hdev, u8 *ptr)
+{
+	u8 scan_rsp_len = 0;
+
+	if (hdev->appearance)
+		scan_rsp_len = eir_append_appearance(hdev, ptr, scan_rsp_len);
+
+	return eir_append_local_name(hdev, ptr, scan_rsp_len);
+}
+
+u8 eir_create_scan_rsp(struct hci_dev *hdev, u8 instance, u8 *ptr)
+{
+	struct adv_info *adv;
+	u8 scan_rsp_len = 0;
+
+	if (!instance)
+		return create_default_scan_rsp(hdev, ptr);
+
+	adv = hci_find_adv_instance(hdev, instance);
+	if (!adv)
+		return 0;
+
+	if ((adv->flags & MGMT_ADV_FLAG_APPEARANCE) && hdev->appearance)
+		scan_rsp_len = eir_append_appearance(hdev, ptr, scan_rsp_len);
+
+	memcpy(&ptr[scan_rsp_len], adv->scan_rsp_data, adv->scan_rsp_len);
+
+	scan_rsp_len += adv->scan_rsp_len;
+
+	if (adv->flags & MGMT_ADV_FLAG_LOCAL_NAME)
+		scan_rsp_len = eir_append_local_name(hdev, ptr, scan_rsp_len);
+
+	return scan_rsp_len;
+}
+
+void *eir_get_service_data(u8 *eir, size_t eir_len, u16 uuid, size_t *len)
+{
+	size_t dlen;
+
+	while ((eir = eir_get_data(eir, eir_len, EIR_SERVICE_DATA, &dlen))) {
+		u16 value = get_unaligned_le16(eir);
+
+		if (uuid == value) {
+			if (len)
+				*len = dlen - 2;
+			return &eir[2];
+		}
+
+		eir += dlen;
+		eir_len -= dlen;
+	}
+
+	return NULL;
+}