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, 452 insertions, 0 deletions

diff --git a/drivers/usb/common/common.c b/drivers/usb/common/common.c
new file mode 100644
index 000000000..fc0845f68
--- /dev/null
+++ b/drivers/usb/common/common.c
@@ -0,0 +1,452 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Provides code common for host and device side USB.
+ *
+ * If either host side (ie. CONFIG_USB=y) or device side USB stack
+ * (ie. CONFIG_USB_GADGET=y) is compiled in the kernel, this module is
+ * compiled-in as well.  Otherwise, if either of the two stacks is
+ * compiled as module, this file is compiled as module as well.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/usb/ch9.h>
+#include <linux/usb/of.h>
+#include <linux/usb/otg.h>
+#include <linux/of_platform.h>
+#include <linux/debugfs.h>
+#include "common.h"
+
+static const char *const ep_type_names[] = {
+	[USB_ENDPOINT_XFER_CONTROL] = "ctrl",
+	[USB_ENDPOINT_XFER_ISOC] = "isoc",
+	[USB_ENDPOINT_XFER_BULK] = "bulk",
+	[USB_ENDPOINT_XFER_INT] = "intr",
+};
+
+/**
+ * usb_ep_type_string() - Returns human readable-name of the endpoint type.
+ * @ep_type: The endpoint type to return human-readable name for.  If it's not
+ *   any of the types: USB_ENDPOINT_XFER_{CONTROL, ISOC, BULK, INT},
+ *   usually got by usb_endpoint_type(), the string 'unknown' will be returned.
+ */
+const char *usb_ep_type_string(int ep_type)
+{
+	if (ep_type < 0 || ep_type >= ARRAY_SIZE(ep_type_names))
+		return "unknown";
+
+	return ep_type_names[ep_type];
+}
+EXPORT_SYMBOL_GPL(usb_ep_type_string);
+
+/**
+ * usb_otg_state_string() - returns human readable name of OTG state.
+ * @state: the OTG state to return the human readable name of. If it's not
+ *    any of the states defined in usb_otg_state enum, 'UNDEFINED' will be
+ *    returned.
+ */
+const char *usb_otg_state_string(enum usb_otg_state state)
+{
+	static const char *const names[] = {
+		[OTG_STATE_A_IDLE] = "a_idle",
+		[OTG_STATE_A_WAIT_VRISE] = "a_wait_vrise",
+		[OTG_STATE_A_WAIT_BCON] = "a_wait_bcon",
+		[OTG_STATE_A_HOST] = "a_host",
+		[OTG_STATE_A_SUSPEND] = "a_suspend",
+		[OTG_STATE_A_PERIPHERAL] = "a_peripheral",
+		[OTG_STATE_A_WAIT_VFALL] = "a_wait_vfall",
+		[OTG_STATE_A_VBUS_ERR] = "a_vbus_err",
+		[OTG_STATE_B_IDLE] = "b_idle",
+		[OTG_STATE_B_SRP_INIT] = "b_srp_init",
+		[OTG_STATE_B_PERIPHERAL] = "b_peripheral",
+		[OTG_STATE_B_WAIT_ACON] = "b_wait_acon",
+		[OTG_STATE_B_HOST] = "b_host",
+	};
+
+	if (state < 0 || state >= ARRAY_SIZE(names))
+		return "UNDEFINED";
+
+	return names[state];
+}
+EXPORT_SYMBOL_GPL(usb_otg_state_string);
+
+static const char *const speed_names[] = {
+	[USB_SPEED_UNKNOWN] = "UNKNOWN",
+	[USB_SPEED_LOW] = "low-speed",
+	[USB_SPEED_FULL] = "full-speed",
+	[USB_SPEED_HIGH] = "high-speed",
+	[USB_SPEED_WIRELESS] = "wireless",
+	[USB_SPEED_SUPER] = "super-speed",
+	[USB_SPEED_SUPER_PLUS] = "super-speed-plus",
+};
+
+static const char *const ssp_rate[] = {
+	[USB_SSP_GEN_UNKNOWN] = "UNKNOWN",
+	[USB_SSP_GEN_2x1] = "super-speed-plus-gen2x1",
+	[USB_SSP_GEN_1x2] = "super-speed-plus-gen1x2",
+	[USB_SSP_GEN_2x2] = "super-speed-plus-gen2x2",
+};
+
+/**
+ * usb_speed_string() - Returns human readable-name of the speed.
+ * @speed: The speed to return human-readable name for.  If it's not
+ *   any of the speeds defined in usb_device_speed enum, string for
+ *   USB_SPEED_UNKNOWN will be returned.
+ */
+const char *usb_speed_string(enum usb_device_speed speed)
+{
+	if (speed < 0 || speed >= ARRAY_SIZE(speed_names))
+		speed = USB_SPEED_UNKNOWN;
+	return speed_names[speed];
+}
+EXPORT_SYMBOL_GPL(usb_speed_string);
+
+/**
+ * usb_get_maximum_speed - Get maximum requested speed for a given USB
+ * controller.
+ * @dev: Pointer to the given USB controller device
+ *
+ * The function gets the maximum speed string from property "maximum-speed",
+ * and returns the corresponding enum usb_device_speed.
+ */
+enum usb_device_speed usb_get_maximum_speed(struct device *dev)
+{
+	const char *p = "maximum-speed";
+	int ret;
+
+	ret = device_property_match_property_string(dev, p, ssp_rate, ARRAY_SIZE(ssp_rate));
+	if (ret > 0)
+		return USB_SPEED_SUPER_PLUS;
+
+	ret = device_property_match_property_string(dev, p, speed_names, ARRAY_SIZE(speed_names));
+	if (ret > 0)
+		return ret;
+
+	return USB_SPEED_UNKNOWN;
+}
+EXPORT_SYMBOL_GPL(usb_get_maximum_speed);
+
+/**
+ * usb_get_maximum_ssp_rate - Get the signaling rate generation and lane count
+ *	of a SuperSpeed Plus capable device.
+ * @dev: Pointer to the given USB controller device
+ *
+ * If the string from "maximum-speed" property is super-speed-plus-genXxY where
+ * 'X' is the generation number and 'Y' is the number of lanes, then this
+ * function returns the corresponding enum usb_ssp_rate.
+ */
+enum usb_ssp_rate usb_get_maximum_ssp_rate(struct device *dev)
+{
+	const char *maximum_speed;
+	int ret;
+
+	ret = device_property_read_string(dev, "maximum-speed", &maximum_speed);
+	if (ret < 0)
+		return USB_SSP_GEN_UNKNOWN;
+
+	ret = match_string(ssp_rate, ARRAY_SIZE(ssp_rate), maximum_speed);
+	return (ret < 0) ? USB_SSP_GEN_UNKNOWN : ret;
+}
+EXPORT_SYMBOL_GPL(usb_get_maximum_ssp_rate);
+
+/**
+ * usb_state_string - Returns human readable name for the state.
+ * @state: The state to return a human-readable name for. If it's not
+ *	any of the states devices in usb_device_state_string enum,
+ *	the string UNKNOWN will be returned.
+ */
+const char *usb_state_string(enum usb_device_state state)
+{
+	static const char *const names[] = {
+		[USB_STATE_NOTATTACHED] = "not attached",
+		[USB_STATE_ATTACHED] = "attached",
+		[USB_STATE_POWERED] = "powered",
+		[USB_STATE_RECONNECTING] = "reconnecting",
+		[USB_STATE_UNAUTHENTICATED] = "unauthenticated",
+		[USB_STATE_DEFAULT] = "default",
+		[USB_STATE_ADDRESS] = "addressed",
+		[USB_STATE_CONFIGURED] = "configured",
+		[USB_STATE_SUSPENDED] = "suspended",
+	};
+
+	if (state < 0 || state >= ARRAY_SIZE(names))
+		return "UNKNOWN";
+
+	return names[state];
+}
+EXPORT_SYMBOL_GPL(usb_state_string);
+
+static const char *const usb_dr_modes[] = {
+	[USB_DR_MODE_UNKNOWN]		= "",
+	[USB_DR_MODE_HOST]		= "host",
+	[USB_DR_MODE_PERIPHERAL]	= "peripheral",
+	[USB_DR_MODE_OTG]		= "otg",
+};
+
+/**
+ * usb_get_dr_mode_from_string() - Get dual role mode for given string
+ * @str: String to find the corresponding dual role mode for
+ *
+ * This function performs a lookup for the given string and returns the
+ * corresponding enum usb_dr_mode. If no match for the string could be found,
+ * 'USB_DR_MODE_UNKNOWN' is returned.
+ */
+static enum usb_dr_mode usb_get_dr_mode_from_string(const char *str)
+{
+	int ret;
+
+	ret = match_string(usb_dr_modes, ARRAY_SIZE(usb_dr_modes), str);
+	return (ret < 0) ? USB_DR_MODE_UNKNOWN : ret;
+}
+
+enum usb_dr_mode usb_get_dr_mode(struct device *dev)
+{
+	const char *dr_mode;
+	int err;
+
+	err = device_property_read_string(dev, "dr_mode", &dr_mode);
+	if (err < 0)
+		return USB_DR_MODE_UNKNOWN;
+
+	return usb_get_dr_mode_from_string(dr_mode);
+}
+EXPORT_SYMBOL_GPL(usb_get_dr_mode);
+
+/**
+ * usb_get_role_switch_default_mode - Get default mode for given device
+ * @dev: Pointer to the given device
+ *
+ * The function gets string from property 'role-switch-default-mode',
+ * and returns the corresponding enum usb_dr_mode.
+ */
+enum usb_dr_mode usb_get_role_switch_default_mode(struct device *dev)
+{
+	const char *str;
+	int ret;
+
+	ret = device_property_read_string(dev, "role-switch-default-mode", &str);
+	if (ret < 0)
+		return USB_DR_MODE_UNKNOWN;
+
+	return usb_get_dr_mode_from_string(str);
+}
+EXPORT_SYMBOL_GPL(usb_get_role_switch_default_mode);
+
+/**
+ * usb_decode_interval - Decode bInterval into the time expressed in 1us unit
+ * @epd: The descriptor of the endpoint
+ * @speed: The speed that the endpoint works as
+ *
+ * Function returns the interval expressed in 1us unit for servicing
+ * endpoint for data transfers.
+ */
+unsigned int usb_decode_interval(const struct usb_endpoint_descriptor *epd,
+				 enum usb_device_speed speed)
+{
+	unsigned int interval = 0;
+
+	switch (usb_endpoint_type(epd)) {
+	case USB_ENDPOINT_XFER_CONTROL:
+		/* uframes per NAK */
+		if (speed == USB_SPEED_HIGH)
+			interval = epd->bInterval;
+		break;
+	case USB_ENDPOINT_XFER_ISOC:
+		interval = 1 << (epd->bInterval - 1);
+		break;
+	case USB_ENDPOINT_XFER_BULK:
+		/* uframes per NAK */
+		if (speed == USB_SPEED_HIGH && usb_endpoint_dir_out(epd))
+			interval = epd->bInterval;
+		break;
+	case USB_ENDPOINT_XFER_INT:
+		if (speed >= USB_SPEED_HIGH)
+			interval = 1 << (epd->bInterval - 1);
+		else
+			interval = epd->bInterval;
+		break;
+	}
+
+	interval *= (speed >= USB_SPEED_HIGH) ? 125 : 1000;
+
+	return interval;
+}
+EXPORT_SYMBOL_GPL(usb_decode_interval);
+
+#ifdef CONFIG_OF
+/**
+ * of_usb_get_dr_mode_by_phy - Get dual role mode for the controller device
+ * which is associated with the given phy device_node
+ * @np:	Pointer to the given phy device_node
+ * @arg0: phandle args[0] for phy's with #phy-cells >= 1, or -1 for
+ *        phys which do not have phy-cells
+ *
+ * In dts a usb controller associates with phy devices.  The function gets
+ * the string from property 'dr_mode' of the controller associated with the
+ * given phy device node, and returns the correspondig enum usb_dr_mode.
+ */
+enum usb_dr_mode of_usb_get_dr_mode_by_phy(struct device_node *np, int arg0)
+{
+	struct device_node *controller;
+	struct of_phandle_args args;
+	const char *dr_mode;
+	int index;
+	int err;
+
+	for_each_node_with_property(controller, "phys") {
+		if (!of_device_is_available(controller))
+			continue;
+		index = 0;
+		do {
+			if (arg0 == -1) {
+				args.np = of_parse_phandle(controller, "phys",
+							index);
+				args.args_count = 0;
+			} else {
+				err = of_parse_phandle_with_args(controller,
+							"phys", "#phy-cells",
+							index, &args);
+				if (err)
+					break;
+			}
+
+			of_node_put(args.np);
+			if (args.np == np && (args.args_count == 0 ||
+					      args.args[0] == arg0))
+				goto finish;
+			index++;
+		} while (args.np);
+	}
+
+finish:
+	err = of_property_read_string(controller, "dr_mode", &dr_mode);
+	of_node_put(controller);
+
+	if (err < 0)
+		return USB_DR_MODE_UNKNOWN;
+
+	return usb_get_dr_mode_from_string(dr_mode);
+}
+EXPORT_SYMBOL_GPL(of_usb_get_dr_mode_by_phy);
+
+/**
+ * of_usb_host_tpl_support - to get if Targeted Peripheral List is supported
+ * for given targeted hosts (non-PC hosts)
+ * @np: Pointer to the given device_node
+ *
+ * The function gets if the targeted hosts support TPL or not
+ */
+bool of_usb_host_tpl_support(struct device_node *np)
+{
+	return of_property_read_bool(np, "tpl-support");
+}
+EXPORT_SYMBOL_GPL(of_usb_host_tpl_support);
+
+/**
+ * of_usb_update_otg_caps - to update usb otg capabilities according to
+ * the passed properties in DT.
+ * @np: Pointer to the given device_node
+ * @otg_caps: Pointer to the target usb_otg_caps to be set
+ *
+ * The function updates the otg capabilities
+ */
+int of_usb_update_otg_caps(struct device_node *np,
+			struct usb_otg_caps *otg_caps)
+{
+	u32 otg_rev;
+
+	if (!otg_caps)
+		return -EINVAL;
+
+	if (!of_property_read_u32(np, "otg-rev", &otg_rev)) {
+		switch (otg_rev) {
+		case 0x0100:
+		case 0x0120:
+		case 0x0130:
+		case 0x0200:
+			/* Choose the lesser one if it's already been set */
+			if (otg_caps->otg_rev)
+				otg_caps->otg_rev = min_t(u16, otg_rev,
+							otg_caps->otg_rev);
+			else
+				otg_caps->otg_rev = otg_rev;
+			break;
+		default:
+			pr_err("%pOF: unsupported otg-rev: 0x%x\n",
+						np, otg_rev);
+			return -EINVAL;
+		}
+	} else {
+		/*
+		 * otg-rev is mandatory for otg properties, if not passed
+		 * we set it to be 0 and assume it's a legacy otg device.
+		 * Non-dt platform can set it afterwards.
+		 */
+		otg_caps->otg_rev = 0;
+	}
+
+	if (of_property_read_bool(np, "hnp-disable"))
+		otg_caps->hnp_support = false;
+	if (of_property_read_bool(np, "srp-disable"))
+		otg_caps->srp_support = false;
+	if (of_property_read_bool(np, "adp-disable") ||
+				(otg_caps->otg_rev < 0x0200))
+		otg_caps->adp_support = false;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(of_usb_update_otg_caps);
+
+/**
+ * usb_of_get_companion_dev - Find the companion device
+ * @dev: the device pointer to find a companion
+ *
+ * Find the companion device from platform bus.
+ *
+ * Takes a reference to the returned struct device which needs to be dropped
+ * after use.
+ *
+ * Return: On success, a pointer to the companion device, %NULL on failure.
+ */
+struct device *usb_of_get_companion_dev(struct device *dev)
+{
+	struct device_node *node;
+	struct platform_device *pdev = NULL;
+
+	node = of_parse_phandle(dev->of_node, "companion", 0);
+	if (node)
+		pdev = of_find_device_by_node(node);
+
+	of_node_put(node);
+
+	return pdev ? &pdev->dev : NULL;
+}
+EXPORT_SYMBOL_GPL(usb_of_get_companion_dev);
+#endif
+
+struct dentry *usb_debug_root;
+EXPORT_SYMBOL_GPL(usb_debug_root);
+
+DEFINE_MUTEX(usb_dynids_lock);
+EXPORT_SYMBOL_GPL(usb_dynids_lock);
+
+static int __init usb_common_init(void)
+{
+	usb_debug_root = debugfs_create_dir("usb", NULL);
+	ledtrig_usb_init();
+	return 0;
+}
+
+static void __exit usb_common_exit(void)
+{
+	ledtrig_usb_exit();
+	debugfs_remove_recursive(usb_debug_root);
+}
+
+subsys_initcall(usb_common_init);
+module_exit(usb_common_exit);
+
+MODULE_DESCRIPTION("Common code for host and device side USB");
+MODULE_LICENSE("GPL");