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, 347 insertions, 0 deletions

diff --git a/drivers/spmi/hisi-spmi-controller.c b/drivers/spmi/hisi-spmi-controller.c
new file mode 100644
index 000000000..122140b97
--- /dev/null
+++ b/drivers/spmi/hisi-spmi-controller.c
@@ -0,0 +1,347 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/seq_file.h>
+#include <linux/slab.h>
+#include <linux/spmi.h>
+
+/*
+ * SPMI register addr
+ */
+#define SPMI_CHANNEL_OFFSET				0x0300
+#define SPMI_SLAVE_OFFSET				0x20
+
+#define SPMI_APB_SPMI_CMD_BASE_ADDR			0x0100
+
+#define SPMI_APB_SPMI_WDATA0_BASE_ADDR			0x0104
+#define SPMI_APB_SPMI_WDATA1_BASE_ADDR			0x0108
+#define SPMI_APB_SPMI_WDATA2_BASE_ADDR			0x010c
+#define SPMI_APB_SPMI_WDATA3_BASE_ADDR			0x0110
+
+#define SPMI_APB_SPMI_STATUS_BASE_ADDR			0x0200
+
+#define SPMI_APB_SPMI_RDATA0_BASE_ADDR			0x0204
+#define SPMI_APB_SPMI_RDATA1_BASE_ADDR			0x0208
+#define SPMI_APB_SPMI_RDATA2_BASE_ADDR			0x020c
+#define SPMI_APB_SPMI_RDATA3_BASE_ADDR			0x0210
+
+#define SPMI_PER_DATAREG_BYTE				4
+/*
+ * SPMI cmd register
+ */
+#define SPMI_APB_SPMI_CMD_EN				BIT(31)
+#define SPMI_APB_SPMI_CMD_TYPE_OFFSET			24
+#define SPMI_APB_SPMI_CMD_LENGTH_OFFSET			20
+#define SPMI_APB_SPMI_CMD_SLAVEID_OFFSET		16
+#define SPMI_APB_SPMI_CMD_ADDR_OFFSET			0
+
+/* Command Opcodes */
+
+enum spmi_controller_cmd_op_code {
+	SPMI_CMD_REG_ZERO_WRITE = 0,
+	SPMI_CMD_REG_WRITE = 1,
+	SPMI_CMD_REG_READ = 2,
+	SPMI_CMD_EXT_REG_WRITE = 3,
+	SPMI_CMD_EXT_REG_READ = 4,
+	SPMI_CMD_EXT_REG_WRITE_L = 5,
+	SPMI_CMD_EXT_REG_READ_L = 6,
+	SPMI_CMD_REG_RESET = 7,
+	SPMI_CMD_REG_SLEEP = 8,
+	SPMI_CMD_REG_SHUTDOWN = 9,
+	SPMI_CMD_REG_WAKEUP = 10,
+};
+
+/*
+ * SPMI status register
+ */
+#define SPMI_APB_TRANS_DONE			BIT(0)
+#define SPMI_APB_TRANS_FAIL			BIT(2)
+
+/* Command register fields */
+#define SPMI_CONTROLLER_CMD_MAX_BYTE_COUNT	16
+
+/* Maximum number of support PMIC peripherals */
+#define SPMI_CONTROLLER_TIMEOUT_US		1000
+#define SPMI_CONTROLLER_MAX_TRANS_BYTES		16
+
+struct spmi_controller_dev {
+	struct spmi_controller	*controller;
+	struct device		*dev;
+	void __iomem		*base;
+	spinlock_t		lock;
+	u32			channel;
+};
+
+static int spmi_controller_wait_for_done(struct device *dev,
+					 struct spmi_controller_dev *ctrl_dev,
+					 void __iomem *base, u8 sid, u16 addr)
+{
+	u32 timeout = SPMI_CONTROLLER_TIMEOUT_US;
+	u32 status, offset;
+
+	offset  = SPMI_APB_SPMI_STATUS_BASE_ADDR;
+	offset += SPMI_CHANNEL_OFFSET * ctrl_dev->channel + SPMI_SLAVE_OFFSET * sid;
+
+	do {
+		status = readl(base + offset);
+
+		if (status & SPMI_APB_TRANS_DONE) {
+			if (status & SPMI_APB_TRANS_FAIL) {
+				dev_err(dev, "%s: transaction failed (0x%x)\n",
+					__func__, status);
+				return -EIO;
+			}
+			dev_dbg(dev, "%s: status 0x%x\n", __func__, status);
+			return 0;
+		}
+		udelay(1);
+	} while (timeout--);
+
+	dev_err(dev, "%s: timeout, status 0x%x\n", __func__, status);
+	return -ETIMEDOUT;
+}
+
+static int spmi_read_cmd(struct spmi_controller *ctrl,
+			 u8 opc, u8 slave_id, u16 slave_addr, u8 *__buf, size_t bc)
+{
+	struct spmi_controller_dev *spmi_controller = dev_get_drvdata(&ctrl->dev);
+	u32 chnl_ofst = SPMI_CHANNEL_OFFSET * spmi_controller->channel;
+	unsigned long flags;
+	u8 *buf = __buf;
+	u32 cmd, data;
+	int rc;
+	u8 op_code, i;
+
+	if (bc > SPMI_CONTROLLER_MAX_TRANS_BYTES) {
+		dev_err(&ctrl->dev,
+			"spmi_controller supports 1..%d bytes per trans, but:%zu requested\n",
+			SPMI_CONTROLLER_MAX_TRANS_BYTES, bc);
+		return  -EINVAL;
+	}
+
+	switch (opc) {
+	case SPMI_CMD_READ:
+		op_code = SPMI_CMD_REG_READ;
+		break;
+	case SPMI_CMD_EXT_READ:
+		op_code = SPMI_CMD_EXT_REG_READ;
+		break;
+	case SPMI_CMD_EXT_READL:
+		op_code = SPMI_CMD_EXT_REG_READ_L;
+		break;
+	default:
+		dev_err(&ctrl->dev, "invalid read cmd 0x%x\n", opc);
+		return -EINVAL;
+	}
+
+	cmd = SPMI_APB_SPMI_CMD_EN |
+	     (op_code << SPMI_APB_SPMI_CMD_TYPE_OFFSET) |
+	     ((bc - 1) << SPMI_APB_SPMI_CMD_LENGTH_OFFSET) |
+	     ((slave_id & 0xf) << SPMI_APB_SPMI_CMD_SLAVEID_OFFSET) |  /* slvid */
+	     ((slave_addr & 0xffff)  << SPMI_APB_SPMI_CMD_ADDR_OFFSET); /* slave_addr */
+
+	spin_lock_irqsave(&spmi_controller->lock, flags);
+
+	writel(cmd, spmi_controller->base + chnl_ofst + SPMI_APB_SPMI_CMD_BASE_ADDR);
+
+	rc = spmi_controller_wait_for_done(&ctrl->dev, spmi_controller,
+					   spmi_controller->base, slave_id, slave_addr);
+	if (rc)
+		goto done;
+
+	for (i = 0; bc > i * SPMI_PER_DATAREG_BYTE; i++) {
+		data = readl(spmi_controller->base + chnl_ofst +
+			     SPMI_SLAVE_OFFSET * slave_id +
+			     SPMI_APB_SPMI_RDATA0_BASE_ADDR +
+			     i * SPMI_PER_DATAREG_BYTE);
+		data = be32_to_cpu((__be32 __force)data);
+		if ((bc - i * SPMI_PER_DATAREG_BYTE) >> 2) {
+			memcpy(buf, &data, sizeof(data));
+			buf += sizeof(data);
+		} else {
+			memcpy(buf, &data, bc % SPMI_PER_DATAREG_BYTE);
+			buf += (bc % SPMI_PER_DATAREG_BYTE);
+		}
+	}
+
+done:
+	spin_unlock_irqrestore(&spmi_controller->lock, flags);
+	if (rc)
+		dev_err(&ctrl->dev,
+			"spmi read wait timeout op:0x%x slave_id:%d slave_addr:0x%x bc:%zu\n",
+			opc, slave_id, slave_addr, bc + 1);
+	else
+		dev_dbg(&ctrl->dev, "%s: id:%d slave_addr:0x%x, read value: %*ph\n",
+			__func__, slave_id, slave_addr, (int)bc, __buf);
+
+	return rc;
+}
+
+static int spmi_write_cmd(struct spmi_controller *ctrl,
+			  u8 opc, u8 slave_id, u16 slave_addr, const u8 *__buf, size_t bc)
+{
+	struct spmi_controller_dev *spmi_controller = dev_get_drvdata(&ctrl->dev);
+	u32 chnl_ofst = SPMI_CHANNEL_OFFSET * spmi_controller->channel;
+	const u8 *buf = __buf;
+	unsigned long flags;
+	u32 cmd, data;
+	int rc;
+	u8 op_code, i;
+
+	if (bc > SPMI_CONTROLLER_MAX_TRANS_BYTES) {
+		dev_err(&ctrl->dev,
+			"spmi_controller supports 1..%d bytes per trans, but:%zu requested\n",
+			SPMI_CONTROLLER_MAX_TRANS_BYTES, bc);
+		return  -EINVAL;
+	}
+
+	switch (opc) {
+	case SPMI_CMD_WRITE:
+		op_code = SPMI_CMD_REG_WRITE;
+		break;
+	case SPMI_CMD_EXT_WRITE:
+		op_code = SPMI_CMD_EXT_REG_WRITE;
+		break;
+	case SPMI_CMD_EXT_WRITEL:
+		op_code = SPMI_CMD_EXT_REG_WRITE_L;
+		break;
+	default:
+		dev_err(&ctrl->dev, "invalid write cmd 0x%x\n", opc);
+		return -EINVAL;
+	}
+
+	cmd = SPMI_APB_SPMI_CMD_EN |
+	      (op_code << SPMI_APB_SPMI_CMD_TYPE_OFFSET) |
+	      ((bc - 1) << SPMI_APB_SPMI_CMD_LENGTH_OFFSET) |
+	      ((slave_id & 0xf) << SPMI_APB_SPMI_CMD_SLAVEID_OFFSET) |
+	      ((slave_addr & 0xffff)  << SPMI_APB_SPMI_CMD_ADDR_OFFSET);
+
+	/* Write data to FIFOs */
+	spin_lock_irqsave(&spmi_controller->lock, flags);
+
+	for (i = 0; bc > i * SPMI_PER_DATAREG_BYTE; i++) {
+		data = 0;
+		if ((bc - i * SPMI_PER_DATAREG_BYTE) >> 2) {
+			memcpy(&data, buf, sizeof(data));
+			buf += sizeof(data);
+		} else {
+			memcpy(&data, buf, bc % SPMI_PER_DATAREG_BYTE);
+			buf += (bc % SPMI_PER_DATAREG_BYTE);
+		}
+
+		writel((u32 __force)cpu_to_be32(data),
+		       spmi_controller->base + chnl_ofst +
+		       SPMI_APB_SPMI_WDATA0_BASE_ADDR +
+		       SPMI_PER_DATAREG_BYTE * i);
+	}
+
+	/* Start the transaction */
+	writel(cmd, spmi_controller->base + chnl_ofst + SPMI_APB_SPMI_CMD_BASE_ADDR);
+
+	rc = spmi_controller_wait_for_done(&ctrl->dev, spmi_controller,
+					   spmi_controller->base, slave_id,
+					   slave_addr);
+	spin_unlock_irqrestore(&spmi_controller->lock, flags);
+
+	if (rc)
+		dev_err(&ctrl->dev, "spmi write wait timeout op:0x%x slave_id:%d slave_addr:0x%x bc:%zu\n",
+			opc, slave_id, slave_addr, bc);
+	else
+		dev_dbg(&ctrl->dev, "%s: id:%d slave_addr:0x%x, wrote value: %*ph\n",
+			__func__, slave_id, slave_addr, (int)bc, __buf);
+
+	return rc;
+}
+
+static int spmi_controller_probe(struct platform_device *pdev)
+{
+	struct spmi_controller_dev *spmi_controller;
+	struct spmi_controller *ctrl;
+	struct resource *iores;
+	int ret;
+
+	ctrl = devm_spmi_controller_alloc(&pdev->dev, sizeof(*spmi_controller));
+	if (IS_ERR(ctrl)) {
+		dev_err(&pdev->dev, "can not allocate spmi_controller data\n");
+		return PTR_ERR(ctrl);
+	}
+	spmi_controller = spmi_controller_get_drvdata(ctrl);
+	spmi_controller->controller = ctrl;
+
+	iores = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!iores) {
+		dev_err(&pdev->dev, "can not get resource!\n");
+		return -EINVAL;
+	}
+
+	spmi_controller->base = devm_ioremap(&pdev->dev, iores->start,
+					     resource_size(iores));
+	if (!spmi_controller->base) {
+		dev_err(&pdev->dev, "can not remap base addr!\n");
+		return -EADDRNOTAVAIL;
+	}
+
+	ret = of_property_read_u32(pdev->dev.of_node, "hisilicon,spmi-channel",
+				   &spmi_controller->channel);
+	if (ret) {
+		dev_err(&pdev->dev, "can not get channel\n");
+		return -ENODEV;
+	}
+
+	platform_set_drvdata(pdev, spmi_controller);
+	dev_set_drvdata(&ctrl->dev, spmi_controller);
+
+	spin_lock_init(&spmi_controller->lock);
+
+	/* Callbacks */
+	ctrl->read_cmd = spmi_read_cmd;
+	ctrl->write_cmd = spmi_write_cmd;
+
+	ret = devm_spmi_controller_add(&pdev->dev, ctrl);
+	if (ret) {
+		dev_err(&pdev->dev, "spmi_controller_add failed with error %d!\n", ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+static const struct of_device_id spmi_controller_match_table[] = {
+	{
+		.compatible = "hisilicon,kirin970-spmi-controller",
+	},
+	{}
+};
+MODULE_DEVICE_TABLE(of, spmi_controller_match_table);
+
+static struct platform_driver spmi_controller_driver = {
+	.probe		= spmi_controller_probe,
+	.driver		= {
+		.name	= "hisi_spmi_controller",
+		.of_match_table = spmi_controller_match_table,
+	},
+};
+
+static int __init spmi_controller_init(void)
+{
+	return platform_driver_register(&spmi_controller_driver);
+}
+postcore_initcall(spmi_controller_init);
+
+static void __exit spmi_controller_exit(void)
+{
+	platform_driver_unregister(&spmi_controller_driver);
+}
+module_exit(spmi_controller_exit);
+
+MODULE_DESCRIPTION("Hisilicon 3670 SPMI Controller driver");
+MODULE_LICENSE("GPL v2");
+MODULE_VERSION("1.0");
+MODULE_ALIAS("platform:spmi_controller");