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, 143 insertions, 0 deletions

diff --git a/drivers/acpi/proc.c b/drivers/acpi/proc.c
new file mode 100644
index 000000000..c08ead072
--- /dev/null
+++ b/drivers/acpi/proc.c
@@ -0,0 +1,143 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include <linux/string_choices.h>
+#include <linux/suspend.h>
+#include <linux/bcd.h>
+#include <linux/acpi.h>
+#include <linux/uaccess.h>
+
+#include "sleep.h"
+#include "internal.h"
+
+/*
+ * this file provides support for:
+ * /proc/acpi/wakeup
+ */
+
+static int
+acpi_system_wakeup_device_seq_show(struct seq_file *seq, void *offset)
+{
+	struct acpi_device *dev, *tmp;
+
+	seq_printf(seq, "Device\tS-state\t  Status   Sysfs node\n");
+
+	mutex_lock(&acpi_device_lock);
+	list_for_each_entry_safe(dev, tmp, &acpi_wakeup_device_list,
+				 wakeup_list) {
+		struct acpi_device_physical_node *entry;
+
+		if (!dev->wakeup.flags.valid)
+			continue;
+
+		seq_printf(seq, "%s\t  S%llu\t",
+			   dev->pnp.bus_id,
+			   dev->wakeup.sleep_state);
+
+		mutex_lock(&dev->physical_node_lock);
+
+		if (!dev->physical_node_count) {
+			seq_printf(seq, "%c%-8s\n",
+				dev->wakeup.flags.valid ? '*' : ' ',
+				str_enabled_disabled(device_may_wakeup(&dev->dev)));
+		} else {
+			struct device *ldev;
+			list_for_each_entry(entry, &dev->physical_node_list,
+					node) {
+				ldev = get_device(entry->dev);
+				if (!ldev)
+					continue;
+
+				if (&entry->node !=
+						dev->physical_node_list.next)
+					seq_printf(seq, "\t\t");
+
+				seq_printf(seq, "%c%-8s  %s:%s\n",
+					dev->wakeup.flags.valid ? '*' : ' ',
+					str_enabled_disabled(device_may_wakeup(ldev) ||
+							     device_may_wakeup(&dev->dev)),
+					ldev->bus ? ldev->bus->name :
+					"no-bus", dev_name(ldev));
+				put_device(ldev);
+			}
+		}
+
+		mutex_unlock(&dev->physical_node_lock);
+	}
+	mutex_unlock(&acpi_device_lock);
+	return 0;
+}
+
+static void physical_device_enable_wakeup(struct acpi_device *adev)
+{
+	struct acpi_device_physical_node *entry;
+
+	mutex_lock(&adev->physical_node_lock);
+
+	list_for_each_entry(entry,
+		&adev->physical_node_list, node)
+		if (entry->dev && device_can_wakeup(entry->dev)) {
+			bool enable = !device_may_wakeup(entry->dev);
+			device_set_wakeup_enable(entry->dev, enable);
+		}
+
+	mutex_unlock(&adev->physical_node_lock);
+}
+
+static ssize_t
+acpi_system_write_wakeup_device(struct file *file,
+				const char __user * buffer,
+				size_t count, loff_t * ppos)
+{
+	struct acpi_device *dev, *tmp;
+	char strbuf[5];
+	char str[5] = "";
+
+	if (count > 4)
+		count = 4;
+
+	if (copy_from_user(strbuf, buffer, count))
+		return -EFAULT;
+	strbuf[count] = '\0';
+	sscanf(strbuf, "%s", str);
+
+	mutex_lock(&acpi_device_lock);
+	list_for_each_entry_safe(dev, tmp, &acpi_wakeup_device_list,
+				 wakeup_list) {
+		if (!dev->wakeup.flags.valid)
+			continue;
+
+		if (!strncmp(dev->pnp.bus_id, str, 4)) {
+			if (device_can_wakeup(&dev->dev)) {
+				bool enable = !device_may_wakeup(&dev->dev);
+				device_set_wakeup_enable(&dev->dev, enable);
+			} else {
+				physical_device_enable_wakeup(dev);
+			}
+			break;
+		}
+	}
+	mutex_unlock(&acpi_device_lock);
+	return count;
+}
+
+static int
+acpi_system_wakeup_device_open_fs(struct inode *inode, struct file *file)
+{
+	return single_open(file, acpi_system_wakeup_device_seq_show,
+			   pde_data(inode));
+}
+
+static const struct proc_ops acpi_system_wakeup_device_proc_ops = {
+	.proc_open	= acpi_system_wakeup_device_open_fs,
+	.proc_read	= seq_read,
+	.proc_write	= acpi_system_write_wakeup_device,
+	.proc_lseek	= seq_lseek,
+	.proc_release	= single_release,
+};
+
+void __init acpi_sleep_proc_init(void)
+{
+	/* 'wakeup device' [R/W] */
+	proc_create("wakeup", 0644, acpi_root_dir, &acpi_system_wakeup_device_proc_ops);
+}