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, 184 insertions, 0 deletions

diff --git a/drivers/regulator/max8893.c b/drivers/regulator/max8893.c
new file mode 100644
index 000000000..5a90633d8
--- /dev/null
+++ b/drivers/regulator/max8893.c
@@ -0,0 +1,184 @@
+// SPDX-License-Identifier: GPL-2.0+
+#include <linux/module.h>
+#include <linux/i2c.h>
+#include <linux/of.h>
+#include <linux/regmap.h>
+#include <linux/regulator/driver.h>
+
+static const struct regulator_ops max8893_ops = {
+	.is_enabled		= regulator_is_enabled_regmap,
+	.enable			= regulator_enable_regmap,
+	.disable		= regulator_disable_regmap,
+	.get_voltage_sel	= regulator_get_voltage_sel_regmap,
+	.set_voltage_sel	= regulator_set_voltage_sel_regmap,
+	.list_voltage		= regulator_list_voltage_linear,
+	.map_voltage		= regulator_map_voltage_linear,
+};
+
+static const struct regulator_desc max8893_regulators[] = {
+	{
+		.name = "BUCK",
+		.supply_name = "in-buck",
+		.of_match = of_match_ptr("buck"),
+		.regulators_node = of_match_ptr("regulators"),
+		.n_voltages = 0x11,
+		.id = 6,
+		.ops = &max8893_ops,
+		.type = REGULATOR_VOLTAGE,
+		.owner = THIS_MODULE,
+		.min_uV = 800000,
+		.uV_step = 100000,
+		.vsel_reg = 0x4,
+		.vsel_mask = 0x1f,
+		.enable_reg = 0x0,
+		.enable_mask = BIT(7),
+	},
+	{
+		.name = "LDO1",
+		.supply_name = "in-ldo1",
+		.of_match = of_match_ptr("ldo1"),
+		.regulators_node = of_match_ptr("regulators"),
+		.n_voltages = 0x12,
+		.id = 1,
+		.ops = &max8893_ops,
+		.type = REGULATOR_VOLTAGE,
+		.owner = THIS_MODULE,
+		.min_uV = 1600000,
+		.uV_step = 100000,
+		.vsel_reg = 0x5,
+		.vsel_mask = 0x1f,
+		.enable_reg = 0x0,
+		.enable_mask = BIT(5),
+	},
+	{
+		.name = "LDO2",
+		.supply_name = "in-ldo2",
+		.of_match = of_match_ptr("ldo2"),
+		.regulators_node = of_match_ptr("regulators"),
+		.n_voltages = 0x16,
+		.id = 2,
+		.ops = &max8893_ops,
+		.type = REGULATOR_VOLTAGE,
+		.owner = THIS_MODULE,
+		.min_uV = 1200000,
+		.uV_step = 100000,
+		.vsel_reg = 0x6,
+		.vsel_mask = 0x1f,
+		.enable_reg = 0x0,
+		.enable_mask = BIT(4),
+	},
+	{
+		.name = "LDO3",
+		.supply_name = "in-ldo3",
+		.of_match = of_match_ptr("ldo3"),
+		.regulators_node = of_match_ptr("regulators"),
+		.n_voltages = 0x12,
+		.id = 3,
+		.ops = &max8893_ops,
+		.type = REGULATOR_VOLTAGE,
+		.owner = THIS_MODULE,
+		.min_uV = 1600000,
+		.uV_step = 100000,
+		.vsel_reg = 0x7,
+		.vsel_mask = 0x1f,
+		.enable_reg = 0x0,
+		.enable_mask = BIT(3),
+	},
+	{
+		.name = "LDO4",
+		.supply_name = "in-ldo4",
+		.of_match = of_match_ptr("ldo4"),
+		.regulators_node = of_match_ptr("regulators"),
+		.n_voltages = 0x1a,
+		.id = 4,
+		.ops = &max8893_ops,
+		.type = REGULATOR_VOLTAGE,
+		.owner = THIS_MODULE,
+		.min_uV = 800000,
+		.uV_step = 100000,
+		.vsel_reg = 0x8,
+		.vsel_mask = 0x1f,
+		.enable_reg = 0x0,
+		.enable_mask = BIT(2),
+	},
+	{
+		.name = "LDO5",
+		.supply_name = "in-ldo5",
+		.of_match = of_match_ptr("ldo5"),
+		.regulators_node = of_match_ptr("regulators"),
+		.n_voltages = 0x1a,
+		.id = 5,
+		.ops = &max8893_ops,
+		.type = REGULATOR_VOLTAGE,
+		.owner = THIS_MODULE,
+		.min_uV = 800000,
+		.uV_step = 100000,
+		.vsel_reg = 0x9,
+		.vsel_mask = 0x1f,
+		.enable_reg = 0x0,
+		.enable_mask = BIT(1),
+	}
+};
+
+static const struct regmap_config max8893_regmap = {
+	.reg_bits = 8,
+	.val_bits = 8,
+};
+
+static int max8893_probe(struct i2c_client *i2c)
+{
+	int id, ret;
+	struct regulator_config config = {.dev = &i2c->dev};
+	struct regmap *regmap = devm_regmap_init_i2c(i2c, &max8893_regmap);
+
+	if (IS_ERR(regmap)) {
+		ret = PTR_ERR(regmap);
+		dev_err(&i2c->dev, "regmap init failed: %d\n", ret);
+		return ret;
+	}
+
+	for (id = 0; id < ARRAY_SIZE(max8893_regulators); id++) {
+		struct regulator_dev *rdev;
+		rdev = devm_regulator_register(&i2c->dev,
+					       &max8893_regulators[id],
+					       &config);
+		if (IS_ERR(rdev)) {
+			ret = PTR_ERR(rdev);
+			dev_err(&i2c->dev, "failed to register %s: %d\n",
+				max8893_regulators[id].name, ret);
+			return ret;
+		}
+	}
+
+	return 0;
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id max8893_dt_match[] = {
+	{ .compatible = "maxim,max8893" },
+	{ /* sentinel */ },
+};
+MODULE_DEVICE_TABLE(of, max8893_dt_match);
+#endif
+
+static const struct i2c_device_id max8893_ids[] = {
+	{ "max8893" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, max8893_ids);
+
+static struct i2c_driver max8893_driver = {
+	.probe		= max8893_probe,
+	.driver		= {
+		.name	= "max8893",
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
+		.of_match_table = of_match_ptr(max8893_dt_match),
+	},
+	.id_table	= max8893_ids,
+};
+
+module_i2c_driver(max8893_driver);
+
+MODULE_DESCRIPTION("Maxim MAX8893 PMIC driver");
+MODULE_AUTHOR("Sergey Larin <cerg2010cerg2010@mail.ru>");
+MODULE_LICENSE("GPL");