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, 253 insertions, 0 deletions

diff --git a/net/bluetooth/hci_codec.c b/net/bluetooth/hci_codec.c
new file mode 100644
index 000000000..5bc5003c3
--- /dev/null
+++ b/net/bluetooth/hci_codec.c
@@ -0,0 +1,253 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/* Copyright (C) 2021 Intel Corporation */
+
+#include <net/bluetooth/bluetooth.h>
+#include <net/bluetooth/hci_core.h>
+#include "hci_codec.h"
+
+static int hci_codec_list_add(struct list_head *list,
+			      struct hci_op_read_local_codec_caps *sent,
+			      struct hci_rp_read_local_codec_caps *rp,
+			      void *caps,
+			      __u32 len)
+{
+	struct codec_list *entry;
+
+	entry = kzalloc(sizeof(*entry) + len, GFP_KERNEL);
+	if (!entry)
+		return -ENOMEM;
+
+	entry->id = sent->id;
+	if (sent->id == 0xFF) {
+		entry->cid = __le16_to_cpu(sent->cid);
+		entry->vid = __le16_to_cpu(sent->vid);
+	}
+	entry->transport = sent->transport;
+	entry->len = len;
+	entry->num_caps = 0;
+	if (rp) {
+		entry->num_caps = rp->num_caps;
+		memcpy(entry->caps, caps, len);
+	}
+	list_add(&entry->list, list);
+
+	return 0;
+}
+
+void hci_codec_list_clear(struct list_head *codec_list)
+{
+	struct codec_list *c, *n;
+
+	list_for_each_entry_safe(c, n, codec_list, list) {
+		list_del(&c->list);
+		kfree(c);
+	}
+}
+
+static void hci_read_codec_capabilities(struct hci_dev *hdev, __u8 transport,
+					struct hci_op_read_local_codec_caps
+					*cmd)
+{
+	__u8 i;
+
+	for (i = 0; i < TRANSPORT_TYPE_MAX; i++) {
+		if (transport & BIT(i)) {
+			struct hci_rp_read_local_codec_caps *rp;
+			struct hci_codec_caps *caps;
+			struct sk_buff *skb;
+			__u8 j;
+			__u32 len;
+
+			cmd->transport = i;
+
+			/* If Read_Codec_Capabilities command is not supported
+			 * then just add codec to the list without caps
+			 */
+			if (!(hdev->commands[45] & 0x08)) {
+				hci_dev_lock(hdev);
+				hci_codec_list_add(&hdev->local_codecs, cmd,
+						   NULL, NULL, 0);
+				hci_dev_unlock(hdev);
+				continue;
+			}
+
+			skb = __hci_cmd_sync_sk(hdev, HCI_OP_READ_LOCAL_CODEC_CAPS,
+						sizeof(*cmd), cmd, 0, HCI_CMD_TIMEOUT, NULL);
+			if (IS_ERR(skb)) {
+				bt_dev_err(hdev, "Failed to read codec capabilities (%ld)",
+					   PTR_ERR(skb));
+				continue;
+			}
+
+			if (skb->len < sizeof(*rp))
+				goto error;
+
+			rp = (void *)skb->data;
+
+			if (rp->status)
+				goto error;
+
+			if (!rp->num_caps) {
+				len = 0;
+				/* this codec doesn't have capabilities */
+				goto skip_caps_parse;
+			}
+
+			skb_pull(skb, sizeof(*rp));
+
+			for (j = 0, len = 0; j < rp->num_caps; j++) {
+				caps = (void *)skb->data;
+				if (skb->len < sizeof(*caps))
+					goto error;
+				if (skb->len < sizeof(caps->len) + caps->len)
+					goto error;
+				len += sizeof(caps->len) + caps->len;
+				skb_pull(skb,  sizeof(caps->len) + caps->len);
+			}
+
+skip_caps_parse:
+			hci_dev_lock(hdev);
+			hci_codec_list_add(&hdev->local_codecs, cmd, rp,
+					   (__u8 *)rp + sizeof(*rp), len);
+			hci_dev_unlock(hdev);
+error:
+			kfree_skb(skb);
+		}
+	}
+}
+
+void hci_read_supported_codecs(struct hci_dev *hdev)
+{
+	struct sk_buff *skb;
+	struct hci_rp_read_local_supported_codecs *rp;
+	struct hci_std_codecs *std_codecs;
+	struct hci_vnd_codecs *vnd_codecs;
+	struct hci_op_read_local_codec_caps caps;
+	__u8 i;
+
+	skb = __hci_cmd_sync_sk(hdev, HCI_OP_READ_LOCAL_CODECS, 0, NULL,
+				0, HCI_CMD_TIMEOUT, NULL);
+
+	if (IS_ERR(skb)) {
+		bt_dev_err(hdev, "Failed to read local supported codecs (%ld)",
+			   PTR_ERR(skb));
+		return;
+	}
+
+	if (skb->len < sizeof(*rp))
+		goto error;
+
+	rp = (void *)skb->data;
+
+	if (rp->status)
+		goto error;
+
+	skb_pull(skb, sizeof(rp->status));
+
+	std_codecs = (void *)skb->data;
+
+	/* validate codecs length before accessing */
+	if (skb->len < flex_array_size(std_codecs, codec, std_codecs->num)
+	    + sizeof(std_codecs->num))
+		goto error;
+
+	/* enumerate codec capabilities of standard codecs */
+	memset(&caps, 0, sizeof(caps));
+	for (i = 0; i < std_codecs->num; i++) {
+		caps.id = std_codecs->codec[i];
+		caps.direction = 0x00;
+		hci_read_codec_capabilities(hdev,
+					    LOCAL_CODEC_ACL_MASK | LOCAL_CODEC_SCO_MASK, &caps);
+	}
+
+	skb_pull(skb, flex_array_size(std_codecs, codec, std_codecs->num)
+		 + sizeof(std_codecs->num));
+
+	vnd_codecs = (void *)skb->data;
+
+	/* validate vendor codecs length before accessing */
+	if (skb->len <
+	    flex_array_size(vnd_codecs, codec, vnd_codecs->num)
+	    + sizeof(vnd_codecs->num))
+		goto error;
+
+	/* enumerate vendor codec capabilities */
+	for (i = 0; i < vnd_codecs->num; i++) {
+		caps.id = 0xFF;
+		caps.cid = vnd_codecs->codec[i].cid;
+		caps.vid = vnd_codecs->codec[i].vid;
+		caps.direction = 0x00;
+		hci_read_codec_capabilities(hdev,
+					    LOCAL_CODEC_ACL_MASK | LOCAL_CODEC_SCO_MASK, &caps);
+	}
+
+error:
+	kfree_skb(skb);
+}
+
+void hci_read_supported_codecs_v2(struct hci_dev *hdev)
+{
+	struct sk_buff *skb;
+	struct hci_rp_read_local_supported_codecs_v2 *rp;
+	struct hci_std_codecs_v2 *std_codecs;
+	struct hci_vnd_codecs_v2 *vnd_codecs;
+	struct hci_op_read_local_codec_caps caps;
+	__u8 i;
+
+	skb = __hci_cmd_sync_sk(hdev, HCI_OP_READ_LOCAL_CODECS_V2, 0, NULL,
+				0, HCI_CMD_TIMEOUT, NULL);
+
+	if (IS_ERR(skb)) {
+		bt_dev_err(hdev, "Failed to read local supported codecs (%ld)",
+			   PTR_ERR(skb));
+		return;
+	}
+
+	if (skb->len < sizeof(*rp))
+		goto error;
+
+	rp = (void *)skb->data;
+
+	if (rp->status)
+		goto error;
+
+	skb_pull(skb, sizeof(rp->status));
+
+	std_codecs = (void *)skb->data;
+
+	/* check for payload data length before accessing */
+	if (skb->len < flex_array_size(std_codecs, codec, std_codecs->num)
+	    + sizeof(std_codecs->num))
+		goto error;
+
+	memset(&caps, 0, sizeof(caps));
+
+	for (i = 0; i < std_codecs->num; i++) {
+		caps.id = std_codecs->codec[i].id;
+		hci_read_codec_capabilities(hdev, std_codecs->codec[i].transport,
+					    &caps);
+	}
+
+	skb_pull(skb, flex_array_size(std_codecs, codec, std_codecs->num)
+		 + sizeof(std_codecs->num));
+
+	vnd_codecs = (void *)skb->data;
+
+	/* check for payload data length before accessing */
+	if (skb->len <
+	    flex_array_size(vnd_codecs, codec, vnd_codecs->num)
+	    + sizeof(vnd_codecs->num))
+		goto error;
+
+	for (i = 0; i < vnd_codecs->num; i++) {
+		caps.id = 0xFF;
+		caps.cid = vnd_codecs->codec[i].cid;
+		caps.vid = vnd_codecs->codec[i].vid;
+		hci_read_codec_capabilities(hdev, vnd_codecs->codec[i].transport,
+					    &caps);
+	}
+
+error:
+	kfree_skb(skb);
+}