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, 182 insertions, 0 deletions

diff --git a/include/media/ipu-bridge.h b/include/media/ipu-bridge.h
new file mode 100644
index 000000000..16fac7654
--- /dev/null
+++ b/include/media/ipu-bridge.h
@@ -0,0 +1,182 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Author: Dan Scally <djrscally@gmail.com> */
+#ifndef __IPU_BRIDGE_H
+#define __IPU_BRIDGE_H
+
+#include <linux/mod_devicetable.h>
+#include <linux/property.h>
+#include <linux/types.h>
+#include <media/v4l2-fwnode.h>
+
+#define IPU_HID				"INT343E"
+#define IPU_MAX_LANES				4
+#define IPU_MAX_PORTS				4
+#define MAX_NUM_LINK_FREQS			3
+
+/* Values are educated guesses as we don't have a spec */
+#define IPU_SENSOR_ROTATION_NORMAL		0
+#define IPU_SENSOR_ROTATION_INVERTED		1
+
+#define IPU_SENSOR_CONFIG(_HID, _NR, ...)	\
+	(const struct ipu_sensor_config) {	\
+		.hid = _HID,			\
+		.nr_link_freqs = _NR,		\
+		.link_freqs = { __VA_ARGS__ }	\
+	}
+
+#define NODE_SENSOR(_HID, _PROPS)		\
+	(const struct software_node) {		\
+		.name = _HID,			\
+		.properties = _PROPS,		\
+	}
+
+#define NODE_PORT(_PORT, _SENSOR_NODE)		\
+	(const struct software_node) {		\
+		.name = _PORT,			\
+		.parent = _SENSOR_NODE,		\
+	}
+
+#define NODE_ENDPOINT(_EP, _PORT, _PROPS)	\
+	(const struct software_node) {		\
+		.name = _EP,			\
+		.parent = _PORT,		\
+		.properties = _PROPS,		\
+	}
+
+#define NODE_VCM(_TYPE)				\
+	(const struct software_node) {		\
+		.name = _TYPE,			\
+	}
+
+enum ipu_sensor_swnodes {
+	SWNODE_SENSOR_HID,
+	SWNODE_SENSOR_PORT,
+	SWNODE_SENSOR_ENDPOINT,
+	SWNODE_IPU_PORT,
+	SWNODE_IPU_ENDPOINT,
+	/* below are optional / maybe empty */
+	SWNODE_IVSC_HID,
+	SWNODE_IVSC_SENSOR_PORT,
+	SWNODE_IVSC_SENSOR_ENDPOINT,
+	SWNODE_IVSC_IPU_PORT,
+	SWNODE_IVSC_IPU_ENDPOINT,
+	SWNODE_VCM,
+	SWNODE_COUNT
+};
+
+/* Data representation as it is in ACPI SSDB buffer */
+struct ipu_sensor_ssdb {
+	u8 version;
+	u8 sku;
+	u8 guid_csi2[16];
+	u8 devfunction;
+	u8 bus;
+	u32 dphylinkenfuses;
+	u32 clockdiv;
+	u8 link;
+	u8 lanes;
+	u32 csiparams[10];
+	u32 maxlanespeed;
+	u8 sensorcalibfileidx;
+	u8 sensorcalibfileidxInMBZ[3];
+	u8 romtype;
+	u8 vcmtype;
+	u8 platforminfo;
+	u8 platformsubinfo;
+	u8 flash;
+	u8 privacyled;
+	u8 degree;
+	u8 mipilinkdefined;
+	u32 mclkspeed;
+	u8 controllogicid;
+	u8 reserved1[3];
+	u8 mclkport;
+	u8 reserved2[13];
+} __packed;
+
+struct ipu_property_names {
+	char clock_frequency[16];
+	char rotation[9];
+	char orientation[12];
+	char bus_type[9];
+	char data_lanes[11];
+	char remote_endpoint[16];
+	char link_frequencies[17];
+};
+
+struct ipu_node_names {
+	char port[7];
+	char ivsc_sensor_port[7];
+	char ivsc_ipu_port[7];
+	char endpoint[11];
+	char remote_port[9];
+	char vcm[16];
+};
+
+struct ipu_sensor_config {
+	const char *hid;
+	const u8 nr_link_freqs;
+	const u64 link_freqs[MAX_NUM_LINK_FREQS];
+};
+
+struct ipu_sensor {
+	/* append ssdb.link(u8) in "-%u" format as suffix of HID */
+	char name[ACPI_ID_LEN + 4];
+	struct acpi_device *adev;
+
+	struct device *csi_dev;
+	struct acpi_device *ivsc_adev;
+	char ivsc_name[ACPI_ID_LEN + 4];
+
+	/* SWNODE_COUNT + 1 for terminating NULL */
+	const struct software_node *group[SWNODE_COUNT + 1];
+	struct software_node swnodes[SWNODE_COUNT];
+	struct ipu_node_names node_names;
+
+	u8 link;
+	u8 lanes;
+	u32 mclkspeed;
+	u32 rotation;
+	enum v4l2_fwnode_orientation orientation;
+	const char *vcm_type;
+
+	struct ipu_property_names prop_names;
+	struct property_entry ep_properties[5];
+	struct property_entry dev_properties[5];
+	struct property_entry ipu_properties[3];
+	struct property_entry ivsc_properties[1];
+	struct property_entry ivsc_sensor_ep_properties[4];
+	struct property_entry ivsc_ipu_ep_properties[4];
+
+	struct software_node_ref_args local_ref[1];
+	struct software_node_ref_args remote_ref[1];
+	struct software_node_ref_args vcm_ref[1];
+	struct software_node_ref_args ivsc_sensor_ref[1];
+	struct software_node_ref_args ivsc_ipu_ref[1];
+};
+
+typedef int (*ipu_parse_sensor_fwnode_t)(struct acpi_device *adev,
+					 struct ipu_sensor *sensor);
+
+struct ipu_bridge {
+	struct device *dev;
+	ipu_parse_sensor_fwnode_t parse_sensor_fwnode;
+	char ipu_node_name[ACPI_ID_LEN];
+	struct software_node ipu_hid_node;
+	u32 data_lanes[4];
+	unsigned int n_sensors;
+	struct ipu_sensor sensors[IPU_MAX_PORTS];
+};
+
+#if IS_ENABLED(CONFIG_IPU_BRIDGE)
+int ipu_bridge_init(struct device *dev,
+		    ipu_parse_sensor_fwnode_t parse_sensor_fwnode);
+int ipu_bridge_parse_ssdb(struct acpi_device *adev, struct ipu_sensor *sensor);
+int ipu_bridge_instantiate_vcm(struct device *sensor);
+#else
+/* Use a define to avoid the @parse_sensor_fwnode argument getting evaluated */
+#define ipu_bridge_init(dev, parse_sensor_fwnode)	(0)
+static inline int ipu_bridge_instantiate_vcm(struct device *s) { return 0; }
+#endif
+
+#endif