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, 209 insertions, 0 deletions

diff --git a/drivers/regulator/isl9305.c b/drivers/regulator/isl9305.c
new file mode 100644
index 000000000..5a234f25e
--- /dev/null
+++ b/drivers/regulator/isl9305.c
@@ -0,0 +1,209 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * isl9305 - Intersil ISL9305 DCDC regulator
+ *
+ * Copyright 2014 Linaro Ltd
+ *
+ * Author: Mark Brown <broonie@kernel.org>
+ */
+
+#include <linux/module.h>
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/of.h>
+#include <linux/platform_data/isl9305.h>
+#include <linux/regmap.h>
+#include <linux/regulator/driver.h>
+#include <linux/regulator/of_regulator.h>
+#include <linux/slab.h>
+
+/*
+ * Registers
+ */
+#define ISL9305_DCD1OUT          0x0
+#define ISL9305_DCD2OUT          0x1
+#define ISL9305_LDO1OUT          0x2
+#define ISL9305_LDO2OUT          0x3
+#define ISL9305_DCD_PARAMETER    0x4
+#define ISL9305_SYSTEM_PARAMETER 0x5
+#define ISL9305_DCD_SRCTL        0x6
+
+#define ISL9305_MAX_REG ISL9305_DCD_SRCTL
+
+/*
+ * DCD_PARAMETER
+ */
+#define ISL9305_DCD_PHASE   0x40
+#define ISL9305_DCD2_ULTRA  0x20
+#define ISL9305_DCD1_ULTRA  0x10
+#define ISL9305_DCD2_BLD    0x08
+#define ISL9305_DCD1_BLD    0x04
+#define ISL9305_DCD2_MODE   0x02
+#define ISL9305_DCD1_MODE   0x01
+
+/*
+ * SYSTEM_PARAMETER
+ */
+#define ISL9305_I2C_EN      0x40
+#define ISL9305_DCDPOR_MASK 0x30
+#define ISL9305_LDO2_EN     0x08
+#define ISL9305_LDO1_EN     0x04
+#define ISL9305_DCD2_EN     0x02
+#define ISL9305_DCD1_EN     0x01
+
+/*
+ * DCD_SRCTL
+ */
+#define ISL9305_DCD2SR_MASK 0xc0
+#define ISL9305_DCD1SR_MASK 0x07
+
+static const struct regulator_ops isl9305_ops = {
+	.enable = regulator_enable_regmap,
+	.disable = regulator_disable_regmap,
+	.is_enabled = regulator_is_enabled_regmap,
+	.list_voltage = regulator_list_voltage_linear,
+	.get_voltage_sel = regulator_get_voltage_sel_regmap,
+	.set_voltage_sel = regulator_set_voltage_sel_regmap,
+};
+
+static const struct regulator_desc isl9305_regulators[] = {
+	[ISL9305_DCD1] = {
+		.name =		"DCD1",
+		.of_match =	of_match_ptr("dcd1"),
+		.regulators_node = of_match_ptr("regulators"),
+		.n_voltages =	0x70,
+		.min_uV =	825000,
+		.uV_step =	25000,
+		.vsel_reg =	ISL9305_DCD1OUT,
+		.vsel_mask =	0x7f,
+		.enable_reg =	ISL9305_SYSTEM_PARAMETER,
+		.enable_mask =	ISL9305_DCD1_EN,
+		.supply_name =	"VINDCD1",
+		.ops =		&isl9305_ops,
+		.owner =	THIS_MODULE,
+	},
+	[ISL9305_DCD2] = {
+		.name =		"DCD2",
+		.of_match =	of_match_ptr("dcd2"),
+		.regulators_node = of_match_ptr("regulators"),
+		.n_voltages =	0x70,
+		.min_uV =	825000,
+		.uV_step =	25000,
+		.vsel_reg =	ISL9305_DCD2OUT,
+		.vsel_mask =	0x7f,
+		.enable_reg =	ISL9305_SYSTEM_PARAMETER,
+		.enable_mask =	ISL9305_DCD2_EN,
+		.supply_name =	"VINDCD2",
+		.ops =		&isl9305_ops,
+		.owner =	THIS_MODULE,
+	},
+	[ISL9305_LDO1] = {
+		.name =		"LDO1",
+		.of_match =	of_match_ptr("ldo1"),
+		.regulators_node = of_match_ptr("regulators"),
+		.n_voltages =	0x37,
+		.min_uV =	900000,
+		.uV_step =	50000,
+		.vsel_reg =	ISL9305_LDO1OUT,
+		.vsel_mask =	0x3f,
+		.enable_reg =	ISL9305_SYSTEM_PARAMETER,
+		.enable_mask =	ISL9305_LDO1_EN,
+		.supply_name =	"VINLDO1",
+		.ops =		&isl9305_ops,
+		.owner =	THIS_MODULE,
+	},
+	[ISL9305_LDO2] = {
+		.name =		"LDO2",
+		.of_match =	of_match_ptr("ldo2"),
+		.regulators_node = of_match_ptr("regulators"),
+		.n_voltages =	0x37,
+		.min_uV =	900000,
+		.uV_step =	50000,
+		.vsel_reg =	ISL9305_LDO2OUT,
+		.vsel_mask =	0x3f,
+		.enable_reg =	ISL9305_SYSTEM_PARAMETER,
+		.enable_mask =	ISL9305_LDO2_EN,
+		.supply_name =	"VINLDO2",
+		.ops =		&isl9305_ops,
+		.owner =	THIS_MODULE,
+	},
+};
+
+static const struct regmap_config isl9305_regmap = {
+	.reg_bits = 8,
+	.val_bits = 8,
+
+	.max_register = ISL9305_MAX_REG,
+	.cache_type = REGCACHE_MAPLE,
+};
+
+static int isl9305_i2c_probe(struct i2c_client *i2c)
+{
+	struct regulator_config config = { };
+	struct isl9305_pdata *pdata = i2c->dev.platform_data;
+	struct regulator_dev *rdev;
+	struct regmap *regmap;
+	int i, ret;
+
+	regmap = devm_regmap_init_i2c(i2c, &isl9305_regmap);
+	if (IS_ERR(regmap)) {
+		ret = PTR_ERR(regmap);
+		dev_err(&i2c->dev, "Failed to create regmap: %d\n", ret);
+		return ret;
+	}
+
+	config.dev = &i2c->dev;
+
+	for (i = 0; i < ARRAY_SIZE(isl9305_regulators); i++) {
+		if (pdata)
+			config.init_data = pdata->init_data[i];
+		else
+			config.init_data = NULL;
+
+		rdev = devm_regulator_register(&i2c->dev,
+					       &isl9305_regulators[i],
+					       &config);
+		if (IS_ERR(rdev)) {
+			ret = PTR_ERR(rdev);
+			dev_err(&i2c->dev, "Failed to register %s: %d\n",
+				isl9305_regulators[i].name, ret);
+			return ret;
+		}
+	}
+
+	return 0;
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id isl9305_dt_ids[] = {
+	{ .compatible = "isl,isl9305" }, /* for backward compat., don't use */
+	{ .compatible = "isil,isl9305" },
+	{ .compatible = "isl,isl9305h" }, /* for backward compat., don't use */
+	{ .compatible = "isil,isl9305h" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, isl9305_dt_ids);
+#endif
+
+static const struct i2c_device_id isl9305_i2c_id[] = {
+	{ "isl9305", },
+	{ "isl9305h", },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, isl9305_i2c_id);
+
+static struct i2c_driver isl9305_regulator_driver = {
+	.driver = {
+		.name = "isl9305",
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
+		.of_match_table	= of_match_ptr(isl9305_dt_ids),
+	},
+	.probe = isl9305_i2c_probe,
+	.id_table = isl9305_i2c_id,
+};
+
+module_i2c_driver(isl9305_regulator_driver);
+
+MODULE_AUTHOR("Mark Brown");
+MODULE_DESCRIPTION("Intersil ISL9305 DCDC regulator");
+MODULE_LICENSE("GPL");