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, 117 insertions, 0 deletions

diff --git a/drivers/acpi/container.c b/drivers/acpi/container.c
new file mode 100644
index 000000000..f138a4335
--- /dev/null
+++ b/drivers/acpi/container.c
@@ -0,0 +1,117 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * container.c  - ACPI Generic Container Driver
+ *
+ * Copyright (C) 2004 Anil S Keshavamurthy (anil.s.keshavamurthy@intel.com)
+ * Copyright (C) 2004 Keiichiro Tokunaga (tokunaga.keiich@jp.fujitsu.com)
+ * Copyright (C) 2004 Motoyuki Ito (motoyuki@soft.fujitsu.com)
+ * Copyright (C) 2004 FUJITSU LIMITED
+ * Copyright (C) 2004, 2013 Intel Corp.
+ * Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
+ */
+#include <linux/acpi.h>
+#include <linux/container.h>
+
+#include "internal.h"
+
+static const struct acpi_device_id container_device_ids[] = {
+	{"ACPI0004", 0},
+	{"PNP0A05", 0},
+	{"PNP0A06", 0},
+	{"", 0},
+};
+
+#ifdef CONFIG_ACPI_CONTAINER
+
+static int check_offline(struct acpi_device *adev, void *not_used)
+{
+	if (acpi_scan_is_offline(adev, false))
+		return 0;
+
+	return -EBUSY;
+}
+
+static int acpi_container_offline(struct container_dev *cdev)
+{
+	/* Check all of the dependent devices' physical companions. */
+	return acpi_dev_for_each_child(ACPI_COMPANION(&cdev->dev), check_offline, NULL);
+}
+
+static void acpi_container_release(struct device *dev)
+{
+	kfree(to_container_dev(dev));
+}
+
+static int container_device_attach(struct acpi_device *adev,
+				   const struct acpi_device_id *not_used)
+{
+	struct container_dev *cdev;
+	struct device *dev;
+	int ret;
+
+	if (adev->flags.is_dock_station)
+		return 0;
+
+	cdev = kzalloc_obj(*cdev);
+	if (!cdev)
+		return -ENOMEM;
+
+	cdev->offline = acpi_container_offline;
+	dev = &cdev->dev;
+	dev->bus = &container_subsys;
+	dev_set_name(dev, "%s", dev_name(&adev->dev));
+	ACPI_COMPANION_SET(dev, adev);
+	dev->release = acpi_container_release;
+	ret = device_register(dev);
+	if (ret) {
+		put_device(dev);
+		return ret;
+	}
+	adev->driver_data = dev;
+	return 1;
+}
+
+static void container_device_detach(struct acpi_device *adev)
+{
+	struct device *dev = acpi_driver_data(adev);
+
+	adev->driver_data = NULL;
+	if (dev)
+		device_unregister(dev);
+}
+
+static void container_device_online(struct acpi_device *adev)
+{
+	struct device *dev = acpi_driver_data(adev);
+
+	kobject_uevent(&dev->kobj, KOBJ_ONLINE);
+}
+
+static struct acpi_scan_handler container_handler = {
+	.ids = container_device_ids,
+	.attach = container_device_attach,
+	.detach = container_device_detach,
+	.hotplug = {
+		.enabled = true,
+		.demand_offline = true,
+		.notify_online = container_device_online,
+	},
+};
+
+void __init acpi_container_init(void)
+{
+	acpi_scan_add_handler(&container_handler);
+}
+
+#else
+
+static struct acpi_scan_handler container_handler = {
+	.ids = container_device_ids,
+};
+
+void __init acpi_container_init(void)
+{
+	acpi_scan_add_handler_with_hotplug(&container_handler, "container");
+}
+
+#endif /* CONFIG_ACPI_CONTAINER */