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, 312 insertions, 0 deletions

diff --git a/drivers/mfd/mt6370.c b/drivers/mfd/mt6370.c
new file mode 100644
index 000000000..c7c2efe35
--- /dev/null
+++ b/drivers/mfd/mt6370.c
@@ -0,0 +1,312 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2022 Richtek Technology Corp.
+ *
+ * Author: ChiYuan Huang <cy_huang@richtek.com>
+ */
+
+#include <linux/bits.h>
+#include <linux/bitfield.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/mfd/core.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+
+#include "mt6370.h"
+
+#define MT6370_REG_DEV_INFO	0x100
+#define MT6370_REG_CHG_IRQ1	0x1C0
+#define MT6370_REG_CHG_MASK1	0x1E0
+#define MT6370_REG_MAXADDR	0x1FF
+
+#define MT6370_VENID_MASK	GENMASK(7, 4)
+
+#define MT6370_NUM_IRQREGS	16
+#define MT6370_USBC_I2CADDR	0x4E
+#define MT6370_MAX_ADDRLEN	2
+
+#define MT6370_VENID_RT5081	0x8
+#define MT6370_VENID_RT5081A	0xA
+#define MT6370_VENID_MT6370	0xE
+#define MT6370_VENID_MT6371	0xF
+#define MT6370_VENID_MT6372P	0x9
+#define MT6370_VENID_MT6372CP	0xB
+
+static const struct regmap_irq mt6370_irqs[] = {
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_DIRCHGON, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_CHG_TREG, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_CHG_AICR, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_CHG_MIVR, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_PWR_RDY, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_FL_CHG_VINOVP, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_CHG_VSYSUV, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_CHG_VSYSOV, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_CHG_VBATOV, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_CHG_VINOVPCHG, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_TS_BAT_COLD, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_TS_BAT_COOL, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_TS_BAT_WARM, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_TS_BAT_HOT, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_TS_STATC, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_CHG_FAULT, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_CHG_STATC, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_CHG_TMR, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_CHG_BATABS, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_CHG_ADPBAD, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_CHG_RVP, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_TSHUTDOWN, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_CHG_IINMEAS, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_CHG_ICCMEAS, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_CHGDET_DONE, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_WDTMR, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_SSFINISH, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_CHG_RECHG, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_CHG_TERM, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_CHG_IEOC, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_ADC_DONE, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_PUMPX_DONE, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_BST_BATUV, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_BST_MIDOV, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_BST_OLP, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_ATTACH, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_DETACH, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_HVDCP_STPDONE, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_HVDCP_VBUSDET_DONE, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_HVDCP_DET, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_CHGDET, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_DCDT, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_DIRCHG_VGOK, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_DIRCHG_WDTMR, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_DIRCHG_UC, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_DIRCHG_OC, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_DIRCHG_OV, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_OVPCTRL_SWON, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_OVPCTRL_UVP_D, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_OVPCTRL_UVP, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_OVPCTRL_OVP_D, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_OVPCTRL_OVP, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_FLED_STRBPIN, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_FLED_TORPIN, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_FLED_TX, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_FLED_LVF, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_FLED2_SHORT, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_FLED1_SHORT, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_FLED2_STRB, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_FLED1_STRB, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_FLED2_STRB_TO, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_FLED1_STRB_TO, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_FLED2_TOR, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_FLED1_TOR, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_OTP, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_VDDA_OVP, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_VDDA_UV, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_LDO_OC, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_BLED_OCP, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_BLED_OVP, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_DSV_VNEG_OCP, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_DSV_VPOS_OCP, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_DSV_BST_OCP, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_DSV_VNEG_SCP, 8),
+	REGMAP_IRQ_REG_LINE(MT6370_IRQ_DSV_VPOS_SCP, 8),
+};
+
+static const struct regmap_irq_chip mt6370_irq_chip = {
+	.name		= "mt6370-irqs",
+	.status_base	= MT6370_REG_CHG_IRQ1,
+	.mask_base	= MT6370_REG_CHG_MASK1,
+	.num_regs	= MT6370_NUM_IRQREGS,
+	.irqs		= mt6370_irqs,
+	.num_irqs	= ARRAY_SIZE(mt6370_irqs),
+};
+
+static const struct resource mt6370_regulator_irqs[] = {
+	DEFINE_RES_IRQ_NAMED(MT6370_IRQ_DSV_VPOS_SCP, "db_vpos_scp"),
+	DEFINE_RES_IRQ_NAMED(MT6370_IRQ_DSV_VNEG_SCP, "db_vneg_scp"),
+	DEFINE_RES_IRQ_NAMED(MT6370_IRQ_DSV_BST_OCP, "db_vbst_ocp"),
+	DEFINE_RES_IRQ_NAMED(MT6370_IRQ_DSV_VPOS_OCP, "db_vpos_ocp"),
+	DEFINE_RES_IRQ_NAMED(MT6370_IRQ_DSV_VNEG_OCP, "db_vneg_ocp"),
+	DEFINE_RES_IRQ_NAMED(MT6370_IRQ_LDO_OC, "ldo_oc"),
+};
+
+static const struct mfd_cell mt6370_devices[] = {
+	MFD_CELL_OF("mt6370-adc",
+		    NULL, NULL, 0, 0, "mediatek,mt6370-adc"),
+	MFD_CELL_OF("mt6370-charger",
+		    NULL, NULL, 0, 0, "mediatek,mt6370-charger"),
+	MFD_CELL_OF("mt6370-flashlight",
+		    NULL, NULL, 0, 0, "mediatek,mt6370-flashlight"),
+	MFD_CELL_OF("mt6370-indicator",
+		    NULL, NULL, 0, 0, "mediatek,mt6370-indicator"),
+	MFD_CELL_OF("mt6370-tcpc",
+		    NULL, NULL, 0, 0, "mediatek,mt6370-tcpc"),
+	MFD_CELL_RES("mt6370-regulator", mt6370_regulator_irqs),
+};
+
+static const struct mfd_cell mt6370_exclusive_devices[] = {
+	MFD_CELL_OF("mt6370-backlight",
+		    NULL, NULL, 0, 0, "mediatek,mt6370-backlight"),
+};
+
+static const struct mfd_cell mt6372_exclusive_devices[] = {
+	MFD_CELL_OF("mt6370-backlight",
+		    NULL, NULL, 0, 0, "mediatek,mt6372-backlight"),
+};
+
+static int mt6370_check_vendor_info(struct device *dev, struct regmap *rmap,
+				    int *vid)
+{
+	unsigned int devinfo;
+	int ret;
+
+	ret = regmap_read(rmap, MT6370_REG_DEV_INFO, &devinfo);
+	if (ret)
+		return ret;
+
+	*vid = FIELD_GET(MT6370_VENID_MASK, devinfo);
+	switch (*vid) {
+	case MT6370_VENID_RT5081:
+	case MT6370_VENID_RT5081A:
+	case MT6370_VENID_MT6370:
+	case MT6370_VENID_MT6371:
+	case MT6370_VENID_MT6372P:
+	case MT6370_VENID_MT6372CP:
+		return 0;
+	default:
+		dev_err(dev, "Unknown Vendor ID 0x%02x\n", devinfo);
+		return -ENODEV;
+	}
+}
+
+static int mt6370_regmap_read(void *context, const void *reg_buf,
+			      size_t reg_size, void *val_buf, size_t val_size)
+{
+	struct mt6370_info *info = context;
+	const u8 *u8_buf = reg_buf;
+	u8 bank_idx, bank_addr;
+	int ret;
+
+	bank_idx = u8_buf[0];
+	bank_addr = u8_buf[1];
+
+	ret = i2c_smbus_read_i2c_block_data(info->i2c[bank_idx], bank_addr,
+					    val_size, val_buf);
+	if (ret < 0)
+		return ret;
+
+	if (ret != val_size)
+		return -EIO;
+
+	return 0;
+}
+
+static int mt6370_regmap_write(void *context, const void *data, size_t count)
+{
+	struct mt6370_info *info = context;
+	const u8 *u8_buf = data;
+	u8 bank_idx, bank_addr;
+	int len = count - MT6370_MAX_ADDRLEN;
+
+	bank_idx = u8_buf[0];
+	bank_addr = u8_buf[1];
+
+	return i2c_smbus_write_i2c_block_data(info->i2c[bank_idx], bank_addr,
+					      len, data + MT6370_MAX_ADDRLEN);
+}
+
+static const struct regmap_bus mt6370_regmap_bus = {
+	.read		= mt6370_regmap_read,
+	.write		= mt6370_regmap_write,
+};
+
+static const struct regmap_config mt6370_regmap_config = {
+	.reg_bits		= 16,
+	.val_bits		= 8,
+	.reg_format_endian	= REGMAP_ENDIAN_BIG,
+	.max_register		= MT6370_REG_MAXADDR,
+};
+
+static int mt6370_probe(struct i2c_client *i2c)
+{
+	struct mt6370_info *info;
+	struct i2c_client *usbc_i2c;
+	struct regmap *regmap;
+	struct device *dev = &i2c->dev;
+	int ret, vid;
+
+	info = devm_kzalloc(dev, sizeof(*info), GFP_KERNEL);
+	if (!info)
+		return -ENOMEM;
+
+	usbc_i2c = devm_i2c_new_dummy_device(dev, i2c->adapter,
+					     MT6370_USBC_I2CADDR);
+	if (IS_ERR(usbc_i2c))
+		return dev_err_probe(dev, PTR_ERR(usbc_i2c),
+				     "Failed to register USBC I2C client\n");
+
+	/* Assign I2C client for PMU and TypeC */
+	info->i2c[MT6370_PMU_I2C] = i2c;
+	info->i2c[MT6370_USBC_I2C] = usbc_i2c;
+
+	regmap = devm_regmap_init(dev, &mt6370_regmap_bus,
+				  info, &mt6370_regmap_config);
+	if (IS_ERR(regmap))
+		return dev_err_probe(dev, PTR_ERR(regmap),
+				     "Failed to init regmap\n");
+
+	ret = mt6370_check_vendor_info(dev, regmap, &vid);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to check vendor info\n");
+
+	ret = devm_regmap_add_irq_chip(dev, regmap, i2c->irq,
+				       IRQF_ONESHOT, -1, &mt6370_irq_chip,
+				       &info->irq_data);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to add irq chip\n");
+
+	switch (vid) {
+	case MT6370_VENID_MT6372P:
+	case MT6370_VENID_MT6372CP:
+		ret = devm_mfd_add_devices(dev, PLATFORM_DEVID_AUTO,
+					   mt6372_exclusive_devices,
+					   ARRAY_SIZE(mt6372_exclusive_devices),
+					   NULL, 0,
+					   regmap_irq_get_domain(info->irq_data));
+		break;
+	default:
+		ret = devm_mfd_add_devices(dev, PLATFORM_DEVID_AUTO,
+					   mt6370_exclusive_devices,
+					   ARRAY_SIZE(mt6370_exclusive_devices),
+					   NULL, 0,
+					   regmap_irq_get_domain(info->irq_data));
+		break;
+	}
+
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to add the exclusive devices\n");
+
+	return devm_mfd_add_devices(dev, PLATFORM_DEVID_AUTO,
+				    mt6370_devices, ARRAY_SIZE(mt6370_devices),
+				    NULL, 0,
+				    regmap_irq_get_domain(info->irq_data));
+}
+
+static const struct of_device_id mt6370_match_table[] = {
+	{ .compatible = "mediatek,mt6370" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, mt6370_match_table);
+
+static struct i2c_driver mt6370_driver = {
+	.driver = {
+		.name = "mt6370",
+		.of_match_table = mt6370_match_table,
+	},
+	.probe = mt6370_probe,
+};
+module_i2c_driver(mt6370_driver);
+
+MODULE_AUTHOR("ChiYuan Huang <cy_huang@richtek.com>");
+MODULE_DESCRIPTION("MediaTek MT6370 SubPMIC Driver");
+MODULE_LICENSE("GPL v2");