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, 309 insertions, 0 deletions

diff --git a/net/bluetooth/hidp/sock.c b/net/bluetooth/hidp/sock.c
new file mode 100644
index 000000000..b75bea3cf
--- /dev/null
+++ b/net/bluetooth/hidp/sock.c
@@ -0,0 +1,309 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+   HIDP implementation for Linux Bluetooth stack (BlueZ).
+   Copyright (C) 2003-2004 Marcel Holtmann <marcel@holtmann.org>
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+   OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT OF THIRD PARTY RIGHTS.
+   IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) AND AUTHOR(S) BE LIABLE FOR ANY
+   CLAIM, OR ANY SPECIAL INDIRECT OR CONSEQUENTIAL DAMAGES, OR ANY DAMAGES
+   WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+   ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+   OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+   ALL LIABILITY, INCLUDING LIABILITY FOR INFRINGEMENT OF ANY PATENTS,
+   COPYRIGHTS, TRADEMARKS OR OTHER RIGHTS, RELATING TO USE OF THIS
+   SOFTWARE IS DISCLAIMED.
+*/
+
+#include <linux/compat.h>
+#include <linux/export.h>
+#include <linux/file.h>
+
+#include "hidp.h"
+
+static struct bt_sock_list hidp_sk_list = {
+	.lock = __RW_LOCK_UNLOCKED(hidp_sk_list.lock)
+};
+
+static int hidp_sock_release(struct socket *sock)
+{
+	struct sock *sk = sock->sk;
+
+	BT_DBG("sock %p sk %p", sock, sk);
+
+	if (!sk)
+		return 0;
+
+	bt_sock_unlink(&hidp_sk_list, sk);
+
+	sock_orphan(sk);
+	sock_put(sk);
+
+	return 0;
+}
+
+static int do_hidp_sock_ioctl(struct socket *sock, unsigned int cmd, void __user *argp)
+{
+	struct hidp_connadd_req ca;
+	struct hidp_conndel_req cd;
+	struct hidp_connlist_req cl;
+	struct hidp_conninfo ci;
+	struct socket *csock;
+	struct socket *isock;
+	int err;
+
+	BT_DBG("cmd %x arg %p", cmd, argp);
+
+	switch (cmd) {
+	case HIDPCONNADD:
+		if (!capable(CAP_NET_ADMIN))
+			return -EPERM;
+
+		if (copy_from_user(&ca, argp, sizeof(ca)))
+			return -EFAULT;
+
+		csock = sockfd_lookup(ca.ctrl_sock, &err);
+		if (!csock)
+			return err;
+
+		isock = sockfd_lookup(ca.intr_sock, &err);
+		if (!isock) {
+			sockfd_put(csock);
+			return err;
+		}
+		ca.name[sizeof(ca.name)-1] = 0;
+
+		err = hidp_connection_add(&ca, csock, isock);
+		if (!err && copy_to_user(argp, &ca, sizeof(ca)))
+			err = -EFAULT;
+
+		sockfd_put(csock);
+		sockfd_put(isock);
+
+		return err;
+
+	case HIDPCONNDEL:
+		if (!capable(CAP_NET_ADMIN))
+			return -EPERM;
+
+		if (copy_from_user(&cd, argp, sizeof(cd)))
+			return -EFAULT;
+
+		return hidp_connection_del(&cd);
+
+	case HIDPGETCONNLIST:
+		if (copy_from_user(&cl, argp, sizeof(cl)))
+			return -EFAULT;
+
+		if (cl.cnum <= 0)
+			return -EINVAL;
+
+		err = hidp_get_connlist(&cl);
+		if (!err && copy_to_user(argp, &cl, sizeof(cl)))
+			return -EFAULT;
+
+		return err;
+
+	case HIDPGETCONNINFO:
+		if (copy_from_user(&ci, argp, sizeof(ci)))
+			return -EFAULT;
+
+		err = hidp_get_conninfo(&ci);
+		if (!err && copy_to_user(argp, &ci, sizeof(ci)))
+			return -EFAULT;
+
+		return err;
+	}
+
+	return -EINVAL;
+}
+
+static int hidp_sock_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
+{
+	return do_hidp_sock_ioctl(sock, cmd, (void __user *)arg);
+}
+
+#ifdef CONFIG_COMPAT
+struct compat_hidp_connadd_req {
+	int   ctrl_sock;	/* Connected control socket */
+	int   intr_sock;	/* Connected interrupt socket */
+	__u16 parser;
+	__u16 rd_size;
+	compat_uptr_t rd_data;
+	__u8  country;
+	__u8  subclass;
+	__u16 vendor;
+	__u16 product;
+	__u16 version;
+	__u32 flags;
+	__u32 idle_to;
+	char  name[128];
+};
+
+static int hidp_sock_compat_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
+{
+	void __user *argp = compat_ptr(arg);
+	int err;
+
+	if (cmd == HIDPGETCONNLIST) {
+		struct hidp_connlist_req cl;
+		u32 __user *p = argp;
+		u32 uci;
+
+		if (get_user(cl.cnum, p) || get_user(uci, p + 1))
+			return -EFAULT;
+
+		cl.ci = compat_ptr(uci);
+
+		if (cl.cnum <= 0)
+			return -EINVAL;
+
+		err = hidp_get_connlist(&cl);
+
+		if (!err && put_user(cl.cnum, p))
+			err = -EFAULT;
+
+		return err;
+	} else if (cmd == HIDPCONNADD) {
+		struct compat_hidp_connadd_req ca32;
+		struct hidp_connadd_req ca;
+		struct socket *csock;
+		struct socket *isock;
+
+		if (!capable(CAP_NET_ADMIN))
+			return -EPERM;
+
+		if (copy_from_user(&ca32, (void __user *) arg, sizeof(ca32)))
+			return -EFAULT;
+
+		ca.ctrl_sock = ca32.ctrl_sock;
+		ca.intr_sock = ca32.intr_sock;
+		ca.parser = ca32.parser;
+		ca.rd_size = ca32.rd_size;
+		ca.rd_data = compat_ptr(ca32.rd_data);
+		ca.country = ca32.country;
+		ca.subclass = ca32.subclass;
+		ca.vendor = ca32.vendor;
+		ca.product = ca32.product;
+		ca.version = ca32.version;
+		ca.flags = ca32.flags;
+		ca.idle_to = ca32.idle_to;
+		ca32.name[sizeof(ca32.name) - 1] = '\0';
+		memcpy(ca.name, ca32.name, 128);
+
+		csock = sockfd_lookup(ca.ctrl_sock, &err);
+		if (!csock)
+			return err;
+
+		isock = sockfd_lookup(ca.intr_sock, &err);
+		if (!isock) {
+			sockfd_put(csock);
+			return err;
+		}
+
+		err = hidp_connection_add(&ca, csock, isock);
+		if (!err && copy_to_user(argp, &ca32, sizeof(ca32)))
+			err = -EFAULT;
+
+		sockfd_put(csock);
+		sockfd_put(isock);
+
+		return err;
+	}
+
+	return hidp_sock_ioctl(sock, cmd, arg);
+}
+#endif
+
+static const struct proto_ops hidp_sock_ops = {
+	.family		= PF_BLUETOOTH,
+	.owner		= THIS_MODULE,
+	.release	= hidp_sock_release,
+	.ioctl		= hidp_sock_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl	= hidp_sock_compat_ioctl,
+#endif
+	.bind		= sock_no_bind,
+	.getname	= sock_no_getname,
+	.sendmsg	= sock_no_sendmsg,
+	.recvmsg	= sock_no_recvmsg,
+	.listen		= sock_no_listen,
+	.shutdown	= sock_no_shutdown,
+	.connect	= sock_no_connect,
+	.socketpair	= sock_no_socketpair,
+	.accept		= sock_no_accept,
+	.mmap		= sock_no_mmap
+};
+
+static struct proto hidp_proto = {
+	.name		= "HIDP",
+	.owner		= THIS_MODULE,
+	.obj_size	= sizeof(struct bt_sock)
+};
+
+static int hidp_sock_create(struct net *net, struct socket *sock, int protocol,
+			    int kern)
+{
+	struct sock *sk;
+
+	BT_DBG("sock %p", sock);
+
+	if (sock->type != SOCK_RAW)
+		return -ESOCKTNOSUPPORT;
+
+	sk = bt_sock_alloc(net, sock, &hidp_proto, protocol, GFP_ATOMIC, kern);
+	if (!sk)
+		return -ENOMEM;
+
+	sock->ops = &hidp_sock_ops;
+	sock->state = SS_UNCONNECTED;
+
+	bt_sock_link(&hidp_sk_list, sk);
+
+	return 0;
+}
+
+static const struct net_proto_family hidp_sock_family_ops = {
+	.family	= PF_BLUETOOTH,
+	.owner	= THIS_MODULE,
+	.create	= hidp_sock_create
+};
+
+int __init hidp_init_sockets(void)
+{
+	int err;
+
+	err = proto_register(&hidp_proto, 0);
+	if (err < 0)
+		return err;
+
+	err = bt_sock_register(BTPROTO_HIDP, &hidp_sock_family_ops);
+	if (err < 0) {
+		BT_ERR("Can't register HIDP socket");
+		goto error;
+	}
+
+	err = bt_procfs_init(&init_net, "hidp", &hidp_sk_list, NULL);
+	if (err < 0) {
+		BT_ERR("Failed to create HIDP proc file");
+		bt_sock_unregister(BTPROTO_HIDP);
+		goto error;
+	}
+
+	BT_INFO("HIDP socket layer initialized");
+
+	return 0;
+
+error:
+	proto_unregister(&hidp_proto);
+	return err;
+}
+
+void __exit hidp_cleanup_sockets(void)
+{
+	bt_procfs_cleanup(&init_net, "hidp");
+	bt_sock_unregister(BTPROTO_HIDP);
+	proto_unregister(&hidp_proto);
+}