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, 244 insertions, 0 deletions

diff --git a/drivers/mfd/stpmic1.c b/drivers/mfd/stpmic1.c
new file mode 100644
index 000000000..7c677b034
--- /dev/null
+++ b/drivers/mfd/stpmic1.c
@@ -0,0 +1,244 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) STMicroelectronics 2018
+// Author: Pascal Paillet <p.paillet@st.com>
+
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/mfd/core.h>
+#include <linux/mfd/stpmic1.h>
+#include <linux/module.h>
+#include <linux/reboot.h>
+#include <linux/of.h>
+#include <linux/of_irq.h>
+#include <linux/of_platform.h>
+#include <linux/pm_wakeirq.h>
+#include <linux/regmap.h>
+
+#include <dt-bindings/mfd/st,stpmic1.h>
+
+#define STPMIC1_MAX_RETRIES 2
+
+#define STPMIC1_MAIN_IRQ 0
+
+static const struct regmap_range stpmic1_readable_ranges[] = {
+	regmap_reg_range(TURN_ON_SR, VERSION_SR),
+	regmap_reg_range(MAIN_CR, LDO6_STDBY_CR),
+	regmap_reg_range(BST_SW_CR, BST_SW_CR),
+	regmap_reg_range(INT_PENDING_R1, INT_PENDING_R4),
+	regmap_reg_range(INT_CLEAR_R1, INT_CLEAR_R4),
+	regmap_reg_range(INT_MASK_R1, INT_MASK_R4),
+	regmap_reg_range(INT_SET_MASK_R1, INT_SET_MASK_R4),
+	regmap_reg_range(INT_CLEAR_MASK_R1, INT_CLEAR_MASK_R4),
+	regmap_reg_range(INT_SRC_R1, INT_SRC_R1),
+};
+
+static const struct regmap_range stpmic1_writeable_ranges[] = {
+	regmap_reg_range(MAIN_CR, LDO6_STDBY_CR),
+	regmap_reg_range(BST_SW_CR, BST_SW_CR),
+	regmap_reg_range(INT_CLEAR_R1, INT_CLEAR_R4),
+	regmap_reg_range(INT_SET_MASK_R1, INT_SET_MASK_R4),
+	regmap_reg_range(INT_CLEAR_MASK_R1, INT_CLEAR_MASK_R4),
+};
+
+static const struct regmap_range stpmic1_volatile_ranges[] = {
+	regmap_reg_range(TURN_ON_SR, VERSION_SR),
+	regmap_reg_range(WCHDG_CR, WCHDG_CR),
+	regmap_reg_range(INT_PENDING_R1, INT_PENDING_R4),
+	regmap_reg_range(INT_SRC_R1, INT_SRC_R4),
+};
+
+static const struct regmap_access_table stpmic1_readable_table = {
+	.yes_ranges = stpmic1_readable_ranges,
+	.n_yes_ranges = ARRAY_SIZE(stpmic1_readable_ranges),
+};
+
+static const struct regmap_access_table stpmic1_writeable_table = {
+	.yes_ranges = stpmic1_writeable_ranges,
+	.n_yes_ranges = ARRAY_SIZE(stpmic1_writeable_ranges),
+};
+
+static const struct regmap_access_table stpmic1_volatile_table = {
+	.yes_ranges = stpmic1_volatile_ranges,
+	.n_yes_ranges = ARRAY_SIZE(stpmic1_volatile_ranges),
+};
+
+static const struct regmap_config stpmic1_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.cache_type = REGCACHE_MAPLE,
+	.max_register = PMIC_MAX_REGISTER_ADDRESS,
+	.rd_table = &stpmic1_readable_table,
+	.wr_table = &stpmic1_writeable_table,
+	.volatile_table = &stpmic1_volatile_table,
+};
+
+static const struct regmap_irq stpmic1_irqs[] = {
+	REGMAP_IRQ_REG(IT_PONKEY_F, 0, 0x01),
+	REGMAP_IRQ_REG(IT_PONKEY_R, 0, 0x02),
+	REGMAP_IRQ_REG(IT_WAKEUP_F, 0, 0x04),
+	REGMAP_IRQ_REG(IT_WAKEUP_R, 0, 0x08),
+	REGMAP_IRQ_REG(IT_VBUS_OTG_F, 0, 0x10),
+	REGMAP_IRQ_REG(IT_VBUS_OTG_R, 0, 0x20),
+	REGMAP_IRQ_REG(IT_SWOUT_F, 0, 0x40),
+	REGMAP_IRQ_REG(IT_SWOUT_R, 0, 0x80),
+
+	REGMAP_IRQ_REG(IT_CURLIM_BUCK1, 1, 0x01),
+	REGMAP_IRQ_REG(IT_CURLIM_BUCK2, 1, 0x02),
+	REGMAP_IRQ_REG(IT_CURLIM_BUCK3, 1, 0x04),
+	REGMAP_IRQ_REG(IT_CURLIM_BUCK4, 1, 0x08),
+	REGMAP_IRQ_REG(IT_OCP_OTG, 1, 0x10),
+	REGMAP_IRQ_REG(IT_OCP_SWOUT, 1, 0x20),
+	REGMAP_IRQ_REG(IT_OCP_BOOST, 1, 0x40),
+	REGMAP_IRQ_REG(IT_OVP_BOOST, 1, 0x80),
+
+	REGMAP_IRQ_REG(IT_CURLIM_LDO1, 2, 0x01),
+	REGMAP_IRQ_REG(IT_CURLIM_LDO2, 2, 0x02),
+	REGMAP_IRQ_REG(IT_CURLIM_LDO3, 2, 0x04),
+	REGMAP_IRQ_REG(IT_CURLIM_LDO4, 2, 0x08),
+	REGMAP_IRQ_REG(IT_CURLIM_LDO5, 2, 0x10),
+	REGMAP_IRQ_REG(IT_CURLIM_LDO6, 2, 0x20),
+	REGMAP_IRQ_REG(IT_SHORT_SWOTG, 2, 0x40),
+	REGMAP_IRQ_REG(IT_SHORT_SWOUT, 2, 0x80),
+
+	REGMAP_IRQ_REG(IT_TWARN_F, 3, 0x01),
+	REGMAP_IRQ_REG(IT_TWARN_R, 3, 0x02),
+	REGMAP_IRQ_REG(IT_VINLOW_F, 3, 0x04),
+	REGMAP_IRQ_REG(IT_VINLOW_R, 3, 0x08),
+	REGMAP_IRQ_REG(IT_SWIN_F, 3, 0x40),
+	REGMAP_IRQ_REG(IT_SWIN_R, 3, 0x80),
+};
+
+static const struct regmap_irq_chip stpmic1_regmap_irq_chip = {
+	.name = "pmic_irq",
+	.status_base = INT_PENDING_R1,
+	.mask_base = INT_SET_MASK_R1,
+	.unmask_base = INT_CLEAR_MASK_R1,
+	.mask_unmask_non_inverted = true,
+	.ack_base = INT_CLEAR_R1,
+	.num_regs = STPMIC1_PMIC_NUM_IRQ_REGS,
+	.irqs = stpmic1_irqs,
+	.num_irqs = ARRAY_SIZE(stpmic1_irqs),
+};
+
+static int stpmic1_power_off(struct sys_off_data *data)
+{
+	struct stpmic1 *ddata = data->cb_data;
+	int ret;
+
+	/*
+	 * Attempt to shut down again, in case the first attempt failed.
+	 * The STPMIC1 might get confused and the first regmap_update_bits()
+	 * returns with -ETIMEDOUT / -110 . If that or similar transient
+	 * failure occurs, try to shut down again. If the second attempt
+	 * fails, there is some bigger problem, report it to user.
+	 */
+	for (int retries = 0; retries < STPMIC1_MAX_RETRIES; retries++) {
+		ret = regmap_update_bits(ddata->regmap, MAIN_CR, SOFTWARE_SWITCH_OFF,
+					 SOFTWARE_SWITCH_OFF);
+		if (!ret)
+			return NOTIFY_DONE;
+	}
+
+	dev_err(ddata->dev, "Failed to access PMIC I2C bus (%d)\n", ret);
+
+	return NOTIFY_DONE;
+}
+
+static int stpmic1_probe(struct i2c_client *i2c)
+{
+	struct stpmic1 *ddata;
+	struct device *dev = &i2c->dev;
+	int ret;
+	struct device_node *np = dev->of_node;
+	u32 reg;
+
+	ddata = devm_kzalloc(dev, sizeof(struct stpmic1), GFP_KERNEL);
+	if (!ddata)
+		return -ENOMEM;
+
+	i2c_set_clientdata(i2c, ddata);
+	ddata->dev = dev;
+
+	ddata->regmap = devm_regmap_init_i2c(i2c, &stpmic1_regmap_config);
+	if (IS_ERR(ddata->regmap))
+		return PTR_ERR(ddata->regmap);
+
+	ddata->irq = of_irq_get(np, STPMIC1_MAIN_IRQ);
+	if (ddata->irq < 0) {
+		dev_err(dev, "Failed to get main IRQ: %d\n", ddata->irq);
+		return ddata->irq;
+	}
+
+	ret = regmap_read(ddata->regmap, VERSION_SR, &reg);
+	if (ret) {
+		dev_err(dev, "Unable to read PMIC version\n");
+		return ret;
+	}
+	dev_info(dev, "PMIC Chip Version: 0x%x\n", reg);
+
+	/* Initialize PMIC IRQ Chip & associated IRQ domains */
+	ret = devm_regmap_add_irq_chip(dev, ddata->regmap, ddata->irq,
+				       IRQF_ONESHOT | IRQF_SHARED,
+				       0, &stpmic1_regmap_irq_chip,
+				       &ddata->irq_data);
+	if (ret) {
+		dev_err(dev, "IRQ Chip registration failed: %d\n", ret);
+		return ret;
+	}
+
+	ret = devm_register_power_off_handler(ddata->dev, stpmic1_power_off, ddata);
+	if (ret) {
+		dev_err(ddata->dev, "failed to register sys-off handler: %d\n", ret);
+		return ret;
+	}
+
+	return devm_of_platform_populate(dev);
+}
+
+static int stpmic1_suspend(struct device *dev)
+{
+	struct i2c_client *i2c = to_i2c_client(dev);
+	struct stpmic1 *pmic_dev = i2c_get_clientdata(i2c);
+
+	disable_irq(pmic_dev->irq);
+
+	return 0;
+}
+
+static int stpmic1_resume(struct device *dev)
+{
+	struct i2c_client *i2c = to_i2c_client(dev);
+	struct stpmic1 *pmic_dev = i2c_get_clientdata(i2c);
+	int ret;
+
+	ret = regcache_sync(pmic_dev->regmap);
+	if (ret)
+		return ret;
+
+	enable_irq(pmic_dev->irq);
+
+	return 0;
+}
+
+static DEFINE_SIMPLE_DEV_PM_OPS(stpmic1_pm, stpmic1_suspend, stpmic1_resume);
+
+static const struct of_device_id stpmic1_of_match[] = {
+	{ .compatible = "st,stpmic1", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, stpmic1_of_match);
+
+static struct i2c_driver stpmic1_driver = {
+	.driver = {
+		.name = "stpmic1",
+		.of_match_table = stpmic1_of_match,
+		.pm = pm_sleep_ptr(&stpmic1_pm),
+	},
+	.probe = stpmic1_probe,
+};
+
+module_i2c_driver(stpmic1_driver);
+
+MODULE_DESCRIPTION("STPMIC1 PMIC Driver");
+MODULE_AUTHOR("Pascal Paillet <p.paillet@st.com>");
+MODULE_LICENSE("GPL v2");