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, 98 insertions, 0 deletions

diff --git a/include/acpi/acpi_drivers.h b/include/acpi/acpi_drivers.h
new file mode 100644
index 000000000..bff2ca035
--- /dev/null
+++ b/include/acpi/acpi_drivers.h
@@ -0,0 +1,98 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ *  acpi_drivers.h  ($Revision: 31 $)
+ *
+ *  Copyright (C) 2001, 2002 Andy Grover <andrew.grover@intel.com>
+ *  Copyright (C) 2001, 2002 Paul Diefenbaugh <paul.s.diefenbaugh@intel.com>
+ */
+
+#ifndef __ACPI_DRIVERS_H__
+#define __ACPI_DRIVERS_H__
+
+#define ACPI_MAX_STRING			80
+
+/*
+ * _HID definitions
+ * HIDs must conform to ACPI spec(6.1.4)
+ * Linux specific HIDs do not apply to this and begin with LNX:
+ */
+
+#define ACPI_POWER_HID			"LNXPOWER"
+#define ACPI_PROCESSOR_OBJECT_HID	"LNXCPU"
+#define ACPI_SYSTEM_HID			"LNXSYSTM"
+#define ACPI_THERMAL_HID		"LNXTHERM"
+#define ACPI_BUTTON_HID_POWERF		"LNXPWRBN"
+#define ACPI_BUTTON_HID_SLEEPF		"LNXSLPBN"
+#define ACPI_VIDEO_HID			"LNXVIDEO"
+#define ACPI_BAY_HID			"LNXIOBAY"
+#define ACPI_DOCK_HID			"LNXDOCK"
+#define ACPI_ECDT_HID			"LNXEC"
+/* SMBUS HID definition as supported by Microsoft Windows */
+#define ACPI_SMBUS_MS_HID		"SMB0001"
+/* Quirk for broken IBM BIOSes */
+#define ACPI_SMBUS_IBM_HID		"SMBUSIBM"
+
+/*
+ * For fixed hardware buttons, we fabricate acpi_devices with HID
+ * ACPI_BUTTON_HID_POWERF or ACPI_BUTTON_HID_SLEEPF.  Fixed hardware
+ * signals only an event; it doesn't supply a notification value.
+ * To allow drivers to treat notifications from fixed hardware the
+ * same as those from real devices, we turn the events into this
+ * notification value.
+ */
+#define ACPI_FIXED_HARDWARE_EVENT	0x100
+
+/* --------------------------------------------------------------------------
+                                       PCI
+   -------------------------------------------------------------------------- */
+
+
+/* ACPI PCI Interrupt Link */
+
+int acpi_irq_penalty_init(void);
+int acpi_pci_link_allocate_irq(acpi_handle handle, int index, int *triggering,
+			       int *polarity, char **name, u32 *gsi);
+int acpi_pci_link_free_irq(acpi_handle handle);
+
+/* ACPI PCI Device Binding */
+
+struct pci_bus;
+
+#ifdef CONFIG_PCI
+struct pci_dev *acpi_dev_get_pci_dev(struct acpi_device *adev);
+#else
+static inline struct pci_dev *acpi_dev_get_pci_dev(struct acpi_device *adev)
+{
+	return NULL;
+}
+#endif
+
+static inline struct pci_dev *acpi_get_pci_dev(acpi_handle handle)
+{
+	return acpi_dev_get_pci_dev(acpi_fetch_acpi_dev(handle));
+}
+
+/* Arch-defined function to add a bus to the system */
+
+struct pci_bus *pci_acpi_scan_root(struct acpi_pci_root *root);
+
+#ifdef CONFIG_X86
+void pci_acpi_crs_quirks(void);
+#else
+static inline void pci_acpi_crs_quirks(void) { }
+#endif
+
+/*--------------------------------------------------------------------------
+                                  Dock Station
+  -------------------------------------------------------------------------- */
+
+#ifdef CONFIG_ACPI_DOCK
+extern int is_dock_device(struct acpi_device *adev);
+#else
+static inline int is_dock_device(struct acpi_device *adev)
+{
+	return 0;
+}
+#endif /* CONFIG_ACPI_DOCK */
+
+#endif /*__ACPI_DRIVERS_H__*/