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, 390 insertions, 0 deletions

diff --git a/drivers/regulator/s2mpa01.c b/drivers/regulator/s2mpa01.c
new file mode 100644
index 000000000..817150386
--- /dev/null
+++ b/drivers/regulator/s2mpa01.c
@@ -0,0 +1,390 @@
+// SPDX-License-Identifier: GPL-2.0+
+//
+// Copyright (c) 2013 Samsung Electronics Co., Ltd
+//		http://www.samsung.com
+
+#include <linux/bug.h>
+#include <linux/err.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/regmap.h>
+#include <linux/platform_device.h>
+#include <linux/regulator/driver.h>
+#include <linux/regulator/machine.h>
+#include <linux/regulator/of_regulator.h>
+#include <linux/mfd/samsung/core.h>
+#include <linux/mfd/samsung/s2mpa01.h>
+
+struct s2mpa01_info {
+	int ramp_delay24;
+	int ramp_delay3;
+	int ramp_delay5;
+	int ramp_delay16;
+	int ramp_delay7;
+	int ramp_delay8910;
+};
+
+static int get_ramp_delay(int ramp_delay)
+{
+	unsigned char cnt = 0;
+
+	ramp_delay /= 6250;
+
+	while (true) {
+		ramp_delay = ramp_delay >> 1;
+		if (ramp_delay == 0)
+			break;
+		cnt++;
+	}
+
+	if (cnt > 3)
+		cnt = 3;
+
+	return cnt;
+}
+
+static int s2mpa01_regulator_set_voltage_time_sel(struct regulator_dev *rdev,
+				   unsigned int old_selector,
+				   unsigned int new_selector)
+{
+	struct s2mpa01_info *s2mpa01 = rdev_get_drvdata(rdev);
+	unsigned int ramp_delay = 0;
+	int old_volt, new_volt;
+
+	switch (rdev_get_id(rdev)) {
+	case S2MPA01_BUCK2:
+	case S2MPA01_BUCK4:
+		ramp_delay = s2mpa01->ramp_delay24;
+		break;
+	case S2MPA01_BUCK3:
+		ramp_delay = s2mpa01->ramp_delay3;
+		break;
+	case S2MPA01_BUCK5:
+		ramp_delay = s2mpa01->ramp_delay5;
+		break;
+	case S2MPA01_BUCK1:
+	case S2MPA01_BUCK6:
+		ramp_delay = s2mpa01->ramp_delay16;
+		break;
+	case S2MPA01_BUCK7:
+		ramp_delay = s2mpa01->ramp_delay7;
+		break;
+	case S2MPA01_BUCK8:
+	case S2MPA01_BUCK9:
+	case S2MPA01_BUCK10:
+		ramp_delay = s2mpa01->ramp_delay8910;
+		break;
+	}
+
+	if (ramp_delay == 0)
+		ramp_delay = rdev->desc->ramp_delay;
+
+	old_volt = rdev->desc->min_uV + (rdev->desc->uV_step * old_selector);
+	new_volt = rdev->desc->min_uV + (rdev->desc->uV_step * new_selector);
+
+	return DIV_ROUND_UP(abs(new_volt - old_volt), ramp_delay);
+}
+
+static int s2mpa01_set_ramp_delay(struct regulator_dev *rdev, int ramp_delay)
+{
+	struct s2mpa01_info *s2mpa01 = rdev_get_drvdata(rdev);
+	unsigned int ramp_val, ramp_shift, ramp_reg = S2MPA01_REG_RAMP2;
+	unsigned int ramp_enable = 1, enable_shift = 0;
+	int ret;
+
+	switch (rdev_get_id(rdev)) {
+	case S2MPA01_BUCK1:
+		enable_shift = S2MPA01_BUCK1_RAMP_EN_SHIFT;
+		if (!ramp_delay) {
+			ramp_enable = 0;
+			break;
+		}
+
+		if (ramp_delay > s2mpa01->ramp_delay16)
+			s2mpa01->ramp_delay16 = ramp_delay;
+		else
+			ramp_delay = s2mpa01->ramp_delay16;
+
+		ramp_shift = S2MPA01_BUCK16_RAMP_SHIFT;
+		break;
+	case S2MPA01_BUCK2:
+		enable_shift = S2MPA01_BUCK2_RAMP_EN_SHIFT;
+		if (!ramp_delay) {
+			ramp_enable = 0;
+			break;
+		}
+
+		if (ramp_delay > s2mpa01->ramp_delay24)
+			s2mpa01->ramp_delay24 = ramp_delay;
+		else
+			ramp_delay = s2mpa01->ramp_delay24;
+
+		ramp_shift = S2MPA01_BUCK24_RAMP_SHIFT;
+		ramp_reg = S2MPA01_REG_RAMP1;
+		break;
+	case S2MPA01_BUCK3:
+		enable_shift = S2MPA01_BUCK3_RAMP_EN_SHIFT;
+		if (!ramp_delay) {
+			ramp_enable = 0;
+			break;
+		}
+
+		s2mpa01->ramp_delay3 = ramp_delay;
+		ramp_shift = S2MPA01_BUCK3_RAMP_SHIFT;
+		ramp_reg = S2MPA01_REG_RAMP1;
+		break;
+	case S2MPA01_BUCK4:
+		enable_shift = S2MPA01_BUCK4_RAMP_EN_SHIFT;
+		if (!ramp_delay) {
+			ramp_enable = 0;
+			break;
+		}
+
+		if (ramp_delay > s2mpa01->ramp_delay24)
+			s2mpa01->ramp_delay24 = ramp_delay;
+		else
+			ramp_delay = s2mpa01->ramp_delay24;
+
+		ramp_shift = S2MPA01_BUCK24_RAMP_SHIFT;
+		ramp_reg = S2MPA01_REG_RAMP1;
+		break;
+	case S2MPA01_BUCK5:
+		s2mpa01->ramp_delay5 = ramp_delay;
+		ramp_shift = S2MPA01_BUCK5_RAMP_SHIFT;
+		break;
+	case S2MPA01_BUCK6:
+		if (ramp_delay > s2mpa01->ramp_delay16)
+			s2mpa01->ramp_delay16 = ramp_delay;
+		else
+			ramp_delay = s2mpa01->ramp_delay16;
+
+		ramp_shift = S2MPA01_BUCK16_RAMP_SHIFT;
+		break;
+	case S2MPA01_BUCK7:
+		s2mpa01->ramp_delay7 = ramp_delay;
+		ramp_shift = S2MPA01_BUCK7_RAMP_SHIFT;
+		break;
+	case S2MPA01_BUCK8:
+	case S2MPA01_BUCK9:
+	case S2MPA01_BUCK10:
+		if (ramp_delay > s2mpa01->ramp_delay8910)
+			s2mpa01->ramp_delay8910 = ramp_delay;
+		else
+			ramp_delay = s2mpa01->ramp_delay8910;
+
+		ramp_shift = S2MPA01_BUCK8910_RAMP_SHIFT;
+		break;
+	default:
+		return 0;
+	}
+
+	if (!ramp_enable)
+		goto ramp_disable;
+
+	/* Ramp delay can be enabled/disabled only for buck[1234] */
+	if (rdev_get_id(rdev) >= S2MPA01_BUCK1 &&
+			rdev_get_id(rdev) <= S2MPA01_BUCK4) {
+		ret = regmap_update_bits(rdev->regmap, S2MPA01_REG_RAMP1,
+					 1 << enable_shift, 1 << enable_shift);
+		if (ret) {
+			dev_err(&rdev->dev, "failed to enable ramp rate\n");
+			return ret;
+		}
+	}
+
+	ramp_val = get_ramp_delay(ramp_delay);
+
+	return regmap_update_bits(rdev->regmap, ramp_reg, 0x3 << ramp_shift,
+				  ramp_val << ramp_shift);
+
+ramp_disable:
+	return regmap_update_bits(rdev->regmap, S2MPA01_REG_RAMP1,
+				  1 << enable_shift, 0);
+}
+
+static const struct regulator_ops s2mpa01_ldo_ops = {
+	.list_voltage		= regulator_list_voltage_linear,
+	.map_voltage		= regulator_map_voltage_linear,
+	.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,
+	.set_voltage_time_sel	= regulator_set_voltage_time_sel,
+};
+
+static const struct regulator_ops s2mpa01_buck_ops = {
+	.list_voltage		= regulator_list_voltage_linear,
+	.map_voltage		= regulator_map_voltage_linear,
+	.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,
+	.set_voltage_time_sel	= s2mpa01_regulator_set_voltage_time_sel,
+	.set_ramp_delay		= s2mpa01_set_ramp_delay,
+};
+
+#define regulator_desc_ldo(num, step) {			\
+	.name		= "LDO"#num,			\
+	.of_match	= of_match_ptr("LDO"#num),	\
+	.regulators_node = of_match_ptr("regulators"),	\
+	.id		= S2MPA01_LDO##num,		\
+	.ops		= &s2mpa01_ldo_ops,		\
+	.type		= REGULATOR_VOLTAGE,		\
+	.owner		= THIS_MODULE,			\
+	.min_uV		= MIN_800_MV,			\
+	.uV_step	= step,				\
+	.n_voltages	= S2MPA01_LDO_N_VOLTAGES,	\
+	.vsel_reg	= S2MPA01_REG_L1CTRL + num - 1,	\
+	.vsel_mask	= S2MPA01_LDO_VSEL_MASK,	\
+	.enable_reg	= S2MPA01_REG_L1CTRL + num - 1,	\
+	.enable_mask	= S2MPA01_ENABLE_MASK		\
+}
+
+#define regulator_desc_buck1_4(num)	{			\
+	.name		= "BUCK"#num,				\
+	.of_match	= of_match_ptr("BUCK"#num),		\
+	.regulators_node = of_match_ptr("regulators"),		\
+	.id		= S2MPA01_BUCK##num,			\
+	.ops		= &s2mpa01_buck_ops,			\
+	.type		= REGULATOR_VOLTAGE,			\
+	.owner		= THIS_MODULE,				\
+	.min_uV		= MIN_600_MV,				\
+	.uV_step	= STEP_6_25_MV,				\
+	.n_voltages	= S2MPA01_BUCK_N_VOLTAGES,		\
+	.ramp_delay	= S2MPA01_RAMP_DELAY,			\
+	.vsel_reg	= S2MPA01_REG_B1CTRL2 + (num - 1) * 2,	\
+	.vsel_mask	= S2MPA01_BUCK_VSEL_MASK,		\
+	.enable_reg	= S2MPA01_REG_B1CTRL1 + (num - 1) * 2,	\
+	.enable_mask	= S2MPA01_ENABLE_MASK			\
+}
+
+#define regulator_desc_buck5	{				\
+	.name		= "BUCK5",				\
+	.of_match	= of_match_ptr("BUCK5"),		\
+	.regulators_node = of_match_ptr("regulators"),		\
+	.id		= S2MPA01_BUCK5,			\
+	.ops		= &s2mpa01_buck_ops,			\
+	.type		= REGULATOR_VOLTAGE,			\
+	.owner		= THIS_MODULE,				\
+	.min_uV		= MIN_800_MV,				\
+	.uV_step	= STEP_6_25_MV,				\
+	.n_voltages	= S2MPA01_BUCK_N_VOLTAGES,		\
+	.ramp_delay	= S2MPA01_RAMP_DELAY,			\
+	.vsel_reg	= S2MPA01_REG_B5CTRL2,			\
+	.vsel_mask	= S2MPA01_BUCK_VSEL_MASK,		\
+	.enable_reg	= S2MPA01_REG_B5CTRL1,			\
+	.enable_mask	= S2MPA01_ENABLE_MASK			\
+}
+
+#define regulator_desc_buck6_10(num, min, step) {			\
+	.name		= "BUCK"#num,				\
+	.of_match	= of_match_ptr("BUCK"#num),		\
+	.regulators_node = of_match_ptr("regulators"),		\
+	.id		= S2MPA01_BUCK##num,			\
+	.ops		= &s2mpa01_buck_ops,			\
+	.type		= REGULATOR_VOLTAGE,			\
+	.owner		= THIS_MODULE,				\
+	.min_uV		= min,					\
+	.uV_step	= step,					\
+	.n_voltages	= S2MPA01_BUCK_N_VOLTAGES,		\
+	.ramp_delay	= S2MPA01_RAMP_DELAY,			\
+	.vsel_reg	= S2MPA01_REG_B6CTRL2 + (num - 6) * 2,	\
+	.vsel_mask	= S2MPA01_BUCK_VSEL_MASK,		\
+	.enable_reg	= S2MPA01_REG_B6CTRL1 + (num - 6) * 2,	\
+	.enable_mask	= S2MPA01_ENABLE_MASK			\
+}
+
+static const struct regulator_desc regulators[] = {
+	regulator_desc_ldo(1, STEP_25_MV),
+	regulator_desc_ldo(2, STEP_50_MV),
+	regulator_desc_ldo(3, STEP_50_MV),
+	regulator_desc_ldo(4, STEP_50_MV),
+	regulator_desc_ldo(5, STEP_25_MV),
+	regulator_desc_ldo(6, STEP_25_MV),
+	regulator_desc_ldo(7, STEP_50_MV),
+	regulator_desc_ldo(8, STEP_50_MV),
+	regulator_desc_ldo(9, STEP_50_MV),
+	regulator_desc_ldo(10, STEP_50_MV),
+	regulator_desc_ldo(11, STEP_50_MV),
+	regulator_desc_ldo(12, STEP_50_MV),
+	regulator_desc_ldo(13, STEP_50_MV),
+	regulator_desc_ldo(14, STEP_50_MV),
+	regulator_desc_ldo(15, STEP_50_MV),
+	regulator_desc_ldo(16, STEP_50_MV),
+	regulator_desc_ldo(17, STEP_50_MV),
+	regulator_desc_ldo(18, STEP_50_MV),
+	regulator_desc_ldo(19, STEP_50_MV),
+	regulator_desc_ldo(20, STEP_50_MV),
+	regulator_desc_ldo(21, STEP_50_MV),
+	regulator_desc_ldo(22, STEP_50_MV),
+	regulator_desc_ldo(23, STEP_50_MV),
+	regulator_desc_ldo(24, STEP_50_MV),
+	regulator_desc_ldo(25, STEP_50_MV),
+	regulator_desc_ldo(26, STEP_25_MV),
+	regulator_desc_buck1_4(1),
+	regulator_desc_buck1_4(2),
+	regulator_desc_buck1_4(3),
+	regulator_desc_buck1_4(4),
+	regulator_desc_buck5,
+	regulator_desc_buck6_10(6, MIN_600_MV, STEP_6_25_MV),
+	regulator_desc_buck6_10(7, MIN_600_MV, STEP_6_25_MV),
+	regulator_desc_buck6_10(8, MIN_800_MV, STEP_12_5_MV),
+	regulator_desc_buck6_10(9, MIN_1500_MV, STEP_12_5_MV),
+	regulator_desc_buck6_10(10, MIN_1000_MV, STEP_12_5_MV),
+};
+
+static int s2mpa01_pmic_probe(struct platform_device *pdev)
+{
+	struct sec_pmic_dev *iodev = dev_get_drvdata(pdev->dev.parent);
+	struct regulator_config config = { };
+	struct s2mpa01_info *s2mpa01;
+	int i;
+
+	s2mpa01 = devm_kzalloc(&pdev->dev, sizeof(*s2mpa01), GFP_KERNEL);
+	if (!s2mpa01)
+		return -ENOMEM;
+
+	config.dev = iodev->dev;
+	config.regmap = iodev->regmap_pmic;
+	config.driver_data = s2mpa01;
+
+	for (i = 0; i < S2MPA01_REGULATOR_MAX; i++) {
+		struct regulator_dev *rdev;
+
+		rdev = devm_regulator_register(&pdev->dev,
+						&regulators[i], &config);
+		if (IS_ERR(rdev)) {
+			dev_err(&pdev->dev, "regulator init failed for %d\n",
+				i);
+			return PTR_ERR(rdev);
+		}
+	}
+
+	return 0;
+}
+
+static const struct platform_device_id s2mpa01_pmic_id[] = {
+	{ .name = "s2mpa01-pmic" },
+	{ }
+};
+MODULE_DEVICE_TABLE(platform, s2mpa01_pmic_id);
+
+static struct platform_driver s2mpa01_pmic_driver = {
+	.driver = {
+		.name = "s2mpa01-pmic",
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
+	},
+	.probe = s2mpa01_pmic_probe,
+	.id_table = s2mpa01_pmic_id,
+};
+
+module_platform_driver(s2mpa01_pmic_driver);
+
+/* Module information */
+MODULE_AUTHOR("Sangbeom Kim <sbkim73@samsung.com>");
+MODULE_AUTHOR("Sachin Kamat <sachin.kamat@samsung.com>");
+MODULE_DESCRIPTION("Samsung S2MPA01 Regulator Driver");
+MODULE_LICENSE("GPL");