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, 503 insertions, 0 deletions

diff --git a/drivers/ipack/ipack.c b/drivers/ipack/ipack.c
new file mode 100644
index 000000000..28214f862
--- /dev/null
+++ b/drivers/ipack/ipack.c
@@ -0,0 +1,503 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Industry-pack bus support functions.
+ *
+ * Copyright (C) 2011-2012 CERN (www.cern.ch)
+ * Author: Samuel Iglesias Gonsalvez <siglesias@igalia.com>
+ */
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/idr.h>
+#include <linux/io.h>
+#include <linux/ipack.h>
+
+#define to_ipack_dev(device) container_of(device, struct ipack_device, dev)
+#define to_ipack_driver(drv) container_of_const(drv, struct ipack_driver, driver)
+
+static DEFINE_IDA(ipack_ida);
+
+static void ipack_device_release(struct device *dev)
+{
+	struct ipack_device *device = to_ipack_dev(dev);
+	kfree(device->id);
+	device->release(device);
+}
+
+static inline const struct ipack_device_id *
+ipack_match_one_device(const struct ipack_device_id *id,
+		       const struct ipack_device *device)
+{
+	if ((id->format == IPACK_ANY_FORMAT ||
+				id->format == device->id_format) &&
+	    (id->vendor == IPACK_ANY_ID || id->vendor == device->id_vendor) &&
+	    (id->device == IPACK_ANY_ID || id->device == device->id_device))
+		return id;
+	return NULL;
+}
+
+static const struct ipack_device_id *
+ipack_match_id(const struct ipack_device_id *ids, struct ipack_device *idev)
+{
+	if (ids) {
+		while (ids->vendor || ids->device) {
+			if (ipack_match_one_device(ids, idev))
+				return ids;
+			ids++;
+		}
+	}
+	return NULL;
+}
+
+static int ipack_bus_match(struct device *dev, const struct device_driver *drv)
+{
+	struct ipack_device *idev = to_ipack_dev(dev);
+	const struct ipack_driver *idrv = to_ipack_driver(drv);
+	const struct ipack_device_id *found_id;
+
+	found_id = ipack_match_id(idrv->id_table, idev);
+	return found_id ? 1 : 0;
+}
+
+static int ipack_bus_probe(struct device *device)
+{
+	struct ipack_device *dev = to_ipack_dev(device);
+	struct ipack_driver *drv = to_ipack_driver(device->driver);
+
+	return drv->ops->probe(dev);
+}
+
+static void ipack_bus_remove(struct device *device)
+{
+	struct ipack_device *dev = to_ipack_dev(device);
+	struct ipack_driver *drv = to_ipack_driver(device->driver);
+
+	if (drv->ops->remove)
+		drv->ops->remove(dev);
+}
+
+static int ipack_uevent(const struct device *dev, struct kobj_uevent_env *env)
+{
+	const struct ipack_device *idev;
+
+	if (!dev)
+		return -ENODEV;
+
+	idev = to_ipack_dev(dev);
+
+	if (add_uevent_var(env,
+			   "MODALIAS=ipack:f%02Xv%08Xd%08X", idev->id_format,
+			   idev->id_vendor, idev->id_device))
+		return -ENOMEM;
+
+	return 0;
+}
+
+#define ipack_device_attr(field, format_string)				\
+static ssize_t								\
+field##_show(struct device *dev, struct device_attribute *attr,		\
+		char *buf)						\
+{									\
+	struct ipack_device *idev = to_ipack_dev(dev);			\
+	return sprintf(buf, format_string, idev->field);		\
+}
+
+static ssize_t id_show(struct device *dev,
+		       struct device_attribute *attr, char *buf)
+{
+	unsigned int i, c, l, s;
+	struct ipack_device *idev = to_ipack_dev(dev);
+
+
+	switch (idev->id_format) {
+	case IPACK_ID_VERSION_1:
+		l = 0x7; s = 1; break;
+	case IPACK_ID_VERSION_2:
+		l = 0xf; s = 2; break;
+	default:
+		return -EIO;
+	}
+	c = 0;
+	for (i = 0; i < idev->id_avail; i++) {
+		if (i > 0) {
+			if ((i & l) == 0)
+				buf[c++] = '\n';
+			else if ((i & s) == 0)
+				buf[c++] = ' ';
+		}
+		sprintf(&buf[c], "%02x", idev->id[i]);
+		c += 2;
+	}
+	buf[c++] = '\n';
+	return c;
+}
+
+static ssize_t
+id_vendor_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct ipack_device *idev = to_ipack_dev(dev);
+	switch (idev->id_format) {
+	case IPACK_ID_VERSION_1:
+		return sprintf(buf, "0x%02x\n", idev->id_vendor);
+	case IPACK_ID_VERSION_2:
+		return sprintf(buf, "0x%06x\n", idev->id_vendor);
+	default:
+		return -EIO;
+	}
+}
+
+static ssize_t
+id_device_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct ipack_device *idev = to_ipack_dev(dev);
+	switch (idev->id_format) {
+	case IPACK_ID_VERSION_1:
+		return sprintf(buf, "0x%02x\n", idev->id_device);
+	case IPACK_ID_VERSION_2:
+		return sprintf(buf, "0x%04x\n", idev->id_device);
+	default:
+		return -EIO;
+	}
+}
+
+static ssize_t modalias_show(struct device *dev, struct device_attribute *attr,
+			     char *buf)
+{
+	struct ipack_device *idev = to_ipack_dev(dev);
+
+	return sprintf(buf, "ipac:f%02Xv%08Xd%08X", idev->id_format,
+		       idev->id_vendor, idev->id_device);
+}
+
+ipack_device_attr(id_format, "0x%hhx\n");
+
+static DEVICE_ATTR_RO(id);
+static DEVICE_ATTR_RO(id_device);
+static DEVICE_ATTR_RO(id_format);
+static DEVICE_ATTR_RO(id_vendor);
+static DEVICE_ATTR_RO(modalias);
+
+static struct attribute *ipack_attrs[] = {
+	&dev_attr_id.attr,
+	&dev_attr_id_device.attr,
+	&dev_attr_id_format.attr,
+	&dev_attr_id_vendor.attr,
+	&dev_attr_modalias.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(ipack);
+
+static const struct bus_type ipack_bus_type = {
+	.name      = "ipack",
+	.probe     = ipack_bus_probe,
+	.match     = ipack_bus_match,
+	.remove    = ipack_bus_remove,
+	.dev_groups = ipack_groups,
+	.uevent	   = ipack_uevent,
+};
+
+struct ipack_bus_device *ipack_bus_register(struct device *parent, int slots,
+					    const struct ipack_bus_ops *ops,
+					    struct module *owner)
+{
+	int bus_nr;
+	struct ipack_bus_device *bus;
+
+	bus = kzalloc_obj(*bus);
+	if (!bus)
+		return NULL;
+
+	bus_nr = ida_alloc(&ipack_ida, GFP_KERNEL);
+	if (bus_nr < 0) {
+		kfree(bus);
+		return NULL;
+	}
+
+	bus->bus_nr = bus_nr;
+	bus->parent = parent;
+	bus->slots = slots;
+	bus->ops = ops;
+	bus->owner = owner;
+	return bus;
+}
+EXPORT_SYMBOL_GPL(ipack_bus_register);
+
+static int ipack_unregister_bus_member(struct device *dev, void *data)
+{
+	struct ipack_device *idev = to_ipack_dev(dev);
+	struct ipack_bus_device *bus = data;
+
+	if (idev->bus == bus)
+		ipack_device_del(idev);
+
+	return 1;
+}
+
+int ipack_bus_unregister(struct ipack_bus_device *bus)
+{
+	bus_for_each_dev(&ipack_bus_type, NULL, bus,
+		ipack_unregister_bus_member);
+	ida_free(&ipack_ida, bus->bus_nr);
+	kfree(bus);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(ipack_bus_unregister);
+
+int ipack_driver_register(struct ipack_driver *edrv, struct module *owner,
+			  const char *name)
+{
+	if (!edrv->ops->probe)
+		return -EINVAL;
+
+	edrv->driver.owner = owner;
+	edrv->driver.name = name;
+	edrv->driver.bus = &ipack_bus_type;
+	return driver_register(&edrv->driver);
+}
+EXPORT_SYMBOL_GPL(ipack_driver_register);
+
+void ipack_driver_unregister(struct ipack_driver *edrv)
+{
+	driver_unregister(&edrv->driver);
+}
+EXPORT_SYMBOL_GPL(ipack_driver_unregister);
+
+static u16 ipack_crc_byte(u16 crc, u8 c)
+{
+	int i;
+
+	crc ^= c << 8;
+	for (i = 0; i < 8; i++)
+		crc = (crc << 1) ^ ((crc & 0x8000) ? 0x1021 : 0);
+	return crc;
+}
+
+/*
+ * The algorithm in lib/crc-ccitt.c does not seem to apply since it uses the
+ * opposite bit ordering.
+ */
+static u8 ipack_calc_crc1(struct ipack_device *dev)
+{
+	u8 c;
+	u16 crc;
+	unsigned int i;
+
+	crc = 0xffff;
+	for (i = 0; i < dev->id_avail; i++) {
+		c = (i != 11) ? dev->id[i] : 0;
+		crc = ipack_crc_byte(crc, c);
+	}
+	crc = ~crc;
+	return crc & 0xff;
+}
+
+static u16 ipack_calc_crc2(struct ipack_device *dev)
+{
+	u8 c;
+	u16 crc;
+	unsigned int i;
+
+	crc = 0xffff;
+	for (i = 0; i < dev->id_avail; i++) {
+		c = ((i != 0x18) && (i != 0x19)) ? dev->id[i] : 0;
+		crc = ipack_crc_byte(crc, c);
+	}
+	crc = ~crc;
+	return crc;
+}
+
+static void ipack_parse_id1(struct ipack_device *dev)
+{
+	u8 *id = dev->id;
+	u8 crc;
+
+	dev->id_vendor = id[4];
+	dev->id_device = id[5];
+	dev->speed_8mhz = 1;
+	dev->speed_32mhz = (id[7] == 'H');
+	crc = ipack_calc_crc1(dev);
+	dev->id_crc_correct = (crc == id[11]);
+	if (!dev->id_crc_correct) {
+		dev_warn(&dev->dev, "ID CRC invalid found 0x%x, expected 0x%x.\n",
+				id[11], crc);
+	}
+}
+
+static void ipack_parse_id2(struct ipack_device *dev)
+{
+	__be16 *id = (__be16 *) dev->id;
+	u16 flags, crc;
+
+	dev->id_vendor = ((be16_to_cpu(id[3]) & 0xff) << 16)
+			 + be16_to_cpu(id[4]);
+	dev->id_device = be16_to_cpu(id[5]);
+	flags = be16_to_cpu(id[10]);
+	dev->speed_8mhz = !!(flags & 2);
+	dev->speed_32mhz = !!(flags & 4);
+	crc = ipack_calc_crc2(dev);
+	dev->id_crc_correct = (crc == be16_to_cpu(id[12]));
+	if (!dev->id_crc_correct) {
+		dev_warn(&dev->dev, "ID CRC invalid found 0x%x, expected 0x%x.\n",
+				id[11], crc);
+	}
+}
+
+static int ipack_device_read_id(struct ipack_device *dev)
+{
+	u8 __iomem *idmem;
+	int i;
+	int ret = 0;
+
+	idmem = ioremap(dev->region[IPACK_ID_SPACE].start,
+			dev->region[IPACK_ID_SPACE].size);
+	if (!idmem) {
+		dev_err(&dev->dev, "error mapping memory\n");
+		return -ENOMEM;
+	}
+
+	/* Determine ID PROM Data Format.  If we find the ids "IPAC" or "IPAH"
+	 * we are dealing with a IndustryPack  format 1 device.  If we detect
+	 * "VITA4 " (16 bit big endian formatted) we are dealing with a
+	 * IndustryPack format 2 device */
+	if ((ioread8(idmem + 1) == 'I') &&
+			(ioread8(idmem + 3) == 'P') &&
+			(ioread8(idmem + 5) == 'A') &&
+			((ioread8(idmem + 7) == 'C') ||
+			 (ioread8(idmem + 7) == 'H'))) {
+		dev->id_format = IPACK_ID_VERSION_1;
+		dev->id_avail = ioread8(idmem + 0x15);
+		if ((dev->id_avail < 0x0c) || (dev->id_avail > 0x40)) {
+			dev_warn(&dev->dev, "invalid id size");
+			dev->id_avail = 0x0c;
+		}
+	} else if ((ioread8(idmem + 0) == 'I') &&
+			(ioread8(idmem + 1) == 'V') &&
+			(ioread8(idmem + 2) == 'A') &&
+			(ioread8(idmem + 3) == 'T') &&
+			(ioread8(idmem + 4) == ' ') &&
+			(ioread8(idmem + 5) == '4')) {
+		dev->id_format = IPACK_ID_VERSION_2;
+		dev->id_avail = ioread16be(idmem + 0x16);
+		if ((dev->id_avail < 0x1a) || (dev->id_avail > 0x40)) {
+			dev_warn(&dev->dev, "invalid id size");
+			dev->id_avail = 0x1a;
+		}
+	} else {
+		dev->id_format = IPACK_ID_VERSION_INVALID;
+		dev->id_avail = 0;
+	}
+
+	if (!dev->id_avail) {
+		ret = -ENODEV;
+		goto out;
+	}
+
+	/* Obtain the amount of memory required to store a copy of the complete
+	 * ID ROM contents */
+	dev->id = kmalloc(dev->id_avail, GFP_KERNEL);
+	if (!dev->id) {
+		ret = -ENOMEM;
+		goto out;
+	}
+	for (i = 0; i < dev->id_avail; i++) {
+		if (dev->id_format == IPACK_ID_VERSION_1)
+			dev->id[i] = ioread8(idmem + (i << 1) + 1);
+		else
+			dev->id[i] = ioread8(idmem + i);
+	}
+
+	/* now we can finally work with the copy */
+	switch (dev->id_format) {
+	case IPACK_ID_VERSION_1:
+		ipack_parse_id1(dev);
+		break;
+	case IPACK_ID_VERSION_2:
+		ipack_parse_id2(dev);
+		break;
+	}
+
+out:
+	iounmap(idmem);
+
+	return ret;
+}
+
+int ipack_device_init(struct ipack_device *dev)
+{
+	int ret;
+
+	dev->dev.bus = &ipack_bus_type;
+	dev->dev.release = ipack_device_release;
+	dev->dev.parent = dev->bus->parent;
+	ret = dev_set_name(&dev->dev,
+		     "ipack-dev.%u.%u", dev->bus->bus_nr, dev->slot);
+	if (ret)
+		return ret;
+
+	device_initialize(&dev->dev);
+
+	if (dev->bus->ops->set_clockrate(dev, 8))
+		dev_warn(&dev->dev, "failed to switch to 8 MHz operation for reading of device ID.\n");
+	if (dev->bus->ops->reset_timeout(dev))
+		dev_warn(&dev->dev, "failed to reset potential timeout.");
+
+	ret = ipack_device_read_id(dev);
+	if (ret < 0) {
+		dev_err(&dev->dev, "error reading device id section.\n");
+		return ret;
+	}
+
+	/* if the device supports 32 MHz operation, use it. */
+	if (dev->speed_32mhz) {
+		ret = dev->bus->ops->set_clockrate(dev, 32);
+		if (ret < 0)
+			dev_err(&dev->dev, "failed to switch to 32 MHz operation.\n");
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(ipack_device_init);
+
+int ipack_device_add(struct ipack_device *dev)
+{
+	return device_add(&dev->dev);
+}
+EXPORT_SYMBOL_GPL(ipack_device_add);
+
+void ipack_device_del(struct ipack_device *dev)
+{
+	device_del(&dev->dev);
+	ipack_put_device(dev);
+}
+EXPORT_SYMBOL_GPL(ipack_device_del);
+
+void ipack_get_device(struct ipack_device *dev)
+{
+	get_device(&dev->dev);
+}
+EXPORT_SYMBOL_GPL(ipack_get_device);
+
+void ipack_put_device(struct ipack_device *dev)
+{
+	put_device(&dev->dev);
+}
+EXPORT_SYMBOL_GPL(ipack_put_device);
+
+static int __init ipack_init(void)
+{
+	ida_init(&ipack_ida);
+	return bus_register(&ipack_bus_type);
+}
+
+static void __exit ipack_exit(void)
+{
+	bus_unregister(&ipack_bus_type);
+	ida_destroy(&ipack_ida);
+}
+
+module_init(ipack_init);
+module_exit(ipack_exit);
+
+MODULE_AUTHOR("Samuel Iglesias Gonsalvez <siglesias@igalia.com>");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Industry-pack bus core");