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, 280 insertions, 0 deletions

diff --git a/drivers/usb/phy/phy-ulpi.c b/drivers/usb/phy/phy-ulpi.c
new file mode 100644
index 000000000..4df63e67b
--- /dev/null
+++ b/drivers/usb/phy/phy-ulpi.c
@@ -0,0 +1,280 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Generic ULPI USB transceiver support
+ *
+ * Copyright (C) 2009 Daniel Mack <daniel@caiaq.de>
+ *
+ * Based on sources from
+ *
+ *   Sascha Hauer <s.hauer@pengutronix.de>
+ *   Freescale Semiconductors
+ */
+
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/export.h>
+#include <linux/usb.h>
+#include <linux/usb/otg.h>
+#include <linux/usb/ulpi.h>
+
+
+struct ulpi_info {
+	unsigned int	id;
+	char		*name;
+};
+
+#define ULPI_ID(vendor, product) (((vendor) << 16) | (product))
+#define ULPI_INFO(_id, _name)		\
+	{				\
+		.id	= (_id),	\
+		.name	= (_name),	\
+	}
+
+/* ULPI hardcoded IDs, used for probing */
+static struct ulpi_info ulpi_ids[] = {
+	ULPI_INFO(ULPI_ID(0x04cc, 0x1504), "NXP ISP1504"),
+	ULPI_INFO(ULPI_ID(0x0424, 0x0006), "SMSC USB331x"),
+	ULPI_INFO(ULPI_ID(0x0424, 0x0007), "SMSC USB3320"),
+	ULPI_INFO(ULPI_ID(0x0424, 0x0009), "SMSC USB334x"),
+	ULPI_INFO(ULPI_ID(0x0451, 0x1507), "TI TUSB1210"),
+};
+
+static int ulpi_set_otg_flags(struct usb_phy *phy)
+{
+	unsigned int flags = ULPI_OTG_CTRL_DP_PULLDOWN |
+			     ULPI_OTG_CTRL_DM_PULLDOWN;
+
+	if (phy->flags & ULPI_OTG_ID_PULLUP)
+		flags |= ULPI_OTG_CTRL_ID_PULLUP;
+
+	/*
+	 * ULPI Specification rev.1.1 default
+	 * for Dp/DmPulldown is enabled.
+	 */
+	if (phy->flags & ULPI_OTG_DP_PULLDOWN_DIS)
+		flags &= ~ULPI_OTG_CTRL_DP_PULLDOWN;
+
+	if (phy->flags & ULPI_OTG_DM_PULLDOWN_DIS)
+		flags &= ~ULPI_OTG_CTRL_DM_PULLDOWN;
+
+	if (phy->flags & ULPI_OTG_EXTVBUSIND)
+		flags |= ULPI_OTG_CTRL_EXTVBUSIND;
+
+	return usb_phy_io_write(phy, flags, ULPI_OTG_CTRL);
+}
+
+static int ulpi_set_fc_flags(struct usb_phy *phy)
+{
+	unsigned int flags = 0;
+
+	/*
+	 * ULPI Specification rev.1.1 default
+	 * for XcvrSelect is Full Speed.
+	 */
+	if (phy->flags & ULPI_FC_HS)
+		flags |= ULPI_FUNC_CTRL_HIGH_SPEED;
+	else if (phy->flags & ULPI_FC_LS)
+		flags |= ULPI_FUNC_CTRL_LOW_SPEED;
+	else if (phy->flags & ULPI_FC_FS4LS)
+		flags |= ULPI_FUNC_CTRL_FS4LS;
+	else
+		flags |= ULPI_FUNC_CTRL_FULL_SPEED;
+
+	if (phy->flags & ULPI_FC_TERMSEL)
+		flags |= ULPI_FUNC_CTRL_TERMSELECT;
+
+	/*
+	 * ULPI Specification rev.1.1 default
+	 * for OpMode is Normal Operation.
+	 */
+	if (phy->flags & ULPI_FC_OP_NODRV)
+		flags |= ULPI_FUNC_CTRL_OPMODE_NONDRIVING;
+	else if (phy->flags & ULPI_FC_OP_DIS_NRZI)
+		flags |= ULPI_FUNC_CTRL_OPMODE_DISABLE_NRZI;
+	else if (phy->flags & ULPI_FC_OP_NSYNC_NEOP)
+		flags |= ULPI_FUNC_CTRL_OPMODE_NOSYNC_NOEOP;
+	else
+		flags |= ULPI_FUNC_CTRL_OPMODE_NORMAL;
+
+	/*
+	 * ULPI Specification rev.1.1 default
+	 * for SuspendM is Powered.
+	 */
+	flags |= ULPI_FUNC_CTRL_SUSPENDM;
+
+	return usb_phy_io_write(phy, flags, ULPI_FUNC_CTRL);
+}
+
+static int ulpi_set_ic_flags(struct usb_phy *phy)
+{
+	unsigned int flags = 0;
+
+	if (phy->flags & ULPI_IC_AUTORESUME)
+		flags |= ULPI_IFC_CTRL_AUTORESUME;
+
+	if (phy->flags & ULPI_IC_EXTVBUS_INDINV)
+		flags |= ULPI_IFC_CTRL_EXTERNAL_VBUS;
+
+	if (phy->flags & ULPI_IC_IND_PASSTHRU)
+		flags |= ULPI_IFC_CTRL_PASSTHRU;
+
+	if (phy->flags & ULPI_IC_PROTECT_DIS)
+		flags |= ULPI_IFC_CTRL_PROTECT_IFC_DISABLE;
+
+	return usb_phy_io_write(phy, flags, ULPI_IFC_CTRL);
+}
+
+static int ulpi_set_flags(struct usb_phy *phy)
+{
+	int ret;
+
+	ret = ulpi_set_otg_flags(phy);
+	if (ret)
+		return ret;
+
+	ret = ulpi_set_ic_flags(phy);
+	if (ret)
+		return ret;
+
+	return ulpi_set_fc_flags(phy);
+}
+
+static int ulpi_check_integrity(struct usb_phy *phy)
+{
+	int ret, i;
+	unsigned int val = 0x55;
+
+	for (i = 0; i < 2; i++) {
+		ret = usb_phy_io_write(phy, val, ULPI_SCRATCH);
+		if (ret < 0)
+			return ret;
+
+		ret = usb_phy_io_read(phy, ULPI_SCRATCH);
+		if (ret < 0)
+			return ret;
+
+		if (ret != val) {
+			pr_err("ULPI integrity check: failed!");
+			return -ENODEV;
+		}
+		val = val << 1;
+	}
+
+	pr_info("ULPI integrity check: passed.\n");
+
+	return 0;
+}
+
+static int ulpi_init(struct usb_phy *phy)
+{
+	int i, vid, pid, ret;
+	u32 ulpi_id = 0;
+
+	for (i = 0; i < 4; i++) {
+		ret = usb_phy_io_read(phy, ULPI_PRODUCT_ID_HIGH - i);
+		if (ret < 0)
+			return ret;
+		ulpi_id = (ulpi_id << 8) | ret;
+	}
+	vid = ulpi_id & 0xffff;
+	pid = ulpi_id >> 16;
+
+	pr_info("ULPI transceiver vendor/product ID 0x%04x/0x%04x\n", vid, pid);
+
+	for (i = 0; i < ARRAY_SIZE(ulpi_ids); i++) {
+		if (ulpi_ids[i].id == ULPI_ID(vid, pid)) {
+			pr_info("Found %s ULPI transceiver.\n",
+				ulpi_ids[i].name);
+			break;
+		}
+	}
+
+	ret = ulpi_check_integrity(phy);
+	if (ret)
+		return ret;
+
+	return ulpi_set_flags(phy);
+}
+
+static int ulpi_set_host(struct usb_otg *otg, struct usb_bus *host)
+{
+	struct usb_phy *phy = otg->usb_phy;
+	unsigned int flags = usb_phy_io_read(phy, ULPI_IFC_CTRL);
+
+	if (!host) {
+		otg->host = NULL;
+		return 0;
+	}
+
+	otg->host = host;
+
+	flags &= ~(ULPI_IFC_CTRL_6_PIN_SERIAL_MODE |
+		   ULPI_IFC_CTRL_3_PIN_SERIAL_MODE |
+		   ULPI_IFC_CTRL_CARKITMODE);
+
+	if (phy->flags & ULPI_IC_6PIN_SERIAL)
+		flags |= ULPI_IFC_CTRL_6_PIN_SERIAL_MODE;
+	else if (phy->flags & ULPI_IC_3PIN_SERIAL)
+		flags |= ULPI_IFC_CTRL_3_PIN_SERIAL_MODE;
+	else if (phy->flags & ULPI_IC_CARKIT)
+		flags |= ULPI_IFC_CTRL_CARKITMODE;
+
+	return usb_phy_io_write(phy, flags, ULPI_IFC_CTRL);
+}
+
+static int ulpi_set_vbus(struct usb_otg *otg, bool on)
+{
+	struct usb_phy *phy = otg->usb_phy;
+	unsigned int flags = usb_phy_io_read(phy, ULPI_OTG_CTRL);
+
+	flags &= ~(ULPI_OTG_CTRL_DRVVBUS | ULPI_OTG_CTRL_DRVVBUS_EXT);
+
+	if (on) {
+		if (phy->flags & ULPI_OTG_DRVVBUS)
+			flags |= ULPI_OTG_CTRL_DRVVBUS;
+
+		if (phy->flags & ULPI_OTG_DRVVBUS_EXT)
+			flags |= ULPI_OTG_CTRL_DRVVBUS_EXT;
+	}
+
+	return usb_phy_io_write(phy, flags, ULPI_OTG_CTRL);
+}
+
+static void otg_ulpi_init(struct usb_phy *phy, struct usb_otg *otg,
+			  struct usb_phy_io_ops *ops,
+			  unsigned int flags)
+{
+	phy->label	= "ULPI";
+	phy->flags	= flags;
+	phy->io_ops	= ops;
+	phy->otg	= otg;
+	phy->init	= ulpi_init;
+
+	otg->usb_phy	= phy;
+	otg->set_host	= ulpi_set_host;
+	otg->set_vbus	= ulpi_set_vbus;
+}
+
+struct usb_phy *
+devm_otg_ulpi_create(struct device *dev,
+		     struct usb_phy_io_ops *ops,
+		     unsigned int flags)
+{
+	struct usb_phy *phy;
+	struct usb_otg *otg;
+
+	phy = devm_kzalloc(dev, sizeof(*phy), GFP_KERNEL);
+	if (!phy)
+		return NULL;
+
+	otg = devm_kzalloc(dev, sizeof(*otg), GFP_KERNEL);
+	if (!otg) {
+		devm_kfree(dev, phy);
+		return NULL;
+	}
+
+	otg_ulpi_init(phy, otg, ops, flags);
+
+	return phy;
+}
+EXPORT_SYMBOL_GPL(devm_otg_ulpi_create);