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>

3 files changed, 380 insertions, 0 deletions

diff --git a/drivers/firmware/meson/Kconfig b/drivers/firmware/meson/Kconfig
new file mode 100644
index 000000000..179f5d46d
--- /dev/null
+++ b/drivers/firmware/meson/Kconfig
@@ -0,0 +1,11 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Amlogic Secure Monitor driver
+#
+config MESON_SM
+	tristate "Amlogic Secure Monitor driver"
+	depends on ARCH_MESON || COMPILE_TEST
+	default ARCH_MESON
+	depends on ARM64_4K_PAGES
+	help
+	  Say y here to enable the Amlogic secure monitor driver
diff --git a/drivers/firmware/meson/Makefile b/drivers/firmware/meson/Makefile
new file mode 100644
index 000000000..c6c09483b
--- /dev/null
+++ b/drivers/firmware/meson/Makefile
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+obj-$(CONFIG_MESON_SM) +=	meson_sm.o
diff --git a/drivers/firmware/meson/meson_sm.c b/drivers/firmware/meson/meson_sm.c
new file mode 100644
index 000000000..ab9751a59
--- /dev/null
+++ b/drivers/firmware/meson/meson_sm.c
@@ -0,0 +1,367 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Amlogic Secure Monitor driver
+ *
+ * Copyright (C) 2016 Endless Mobile, Inc.
+ * Author: Carlo Caione <carlo@endlessm.com>
+ */
+
+#define pr_fmt(fmt) "meson-sm: " fmt
+
+#include <linux/arm-smccc.h>
+#include <linux/bug.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/printk.h>
+#include <linux/property.h>
+#include <linux/types.h>
+#include <linux/sizes.h>
+ #include <linux/slab.h>
+
+#include <linux/firmware/meson/meson_sm.h>
+
+struct meson_sm_cmd {
+	unsigned int index;
+	u32 smc_id;
+};
+#define CMD(d, s) { .index = (d), .smc_id = (s), }
+
+struct meson_sm_chip {
+	unsigned int shmem_size;
+	u32 cmd_shmem_in_base;
+	u32 cmd_shmem_out_base;
+	struct meson_sm_cmd cmd[];
+};
+
+static const struct meson_sm_chip gxbb_chip = {
+	.shmem_size		= SZ_4K,
+	.cmd_shmem_in_base	= 0x82000020,
+	.cmd_shmem_out_base	= 0x82000021,
+	.cmd = {
+		CMD(SM_EFUSE_READ,		0x82000030),
+		CMD(SM_EFUSE_WRITE,		0x82000031),
+		CMD(SM_EFUSE_USER_MAX,	0x82000033),
+		CMD(SM_GET_CHIP_ID,		0x82000044),
+		CMD(SM_THERMAL_CALIB_READ,	0x82000047),
+		CMD(SM_A1_PWRC_SET,		0x82000093),
+		CMD(SM_A1_PWRC_GET,		0x82000095),
+		{ /* sentinel */ },
+	},
+};
+
+struct meson_sm_firmware {
+	const struct meson_sm_chip *chip;
+	void __iomem *sm_shmem_in_base;
+	void __iomem *sm_shmem_out_base;
+};
+
+static u32 meson_sm_get_cmd(const struct meson_sm_chip *chip,
+			    unsigned int cmd_index)
+{
+	const struct meson_sm_cmd *cmd = chip->cmd;
+
+	while (cmd->smc_id && cmd->index != cmd_index)
+		cmd++;
+
+	return cmd->smc_id;
+}
+
+static s32 __meson_sm_call(u32 cmd, u32 arg0, u32 arg1, u32 arg2,
+			   u32 arg3, u32 arg4)
+{
+	struct arm_smccc_res res;
+
+	arm_smccc_smc(cmd, arg0, arg1, arg2, arg3, arg4, 0, 0, &res);
+	return res.a0;
+}
+
+static void __iomem *meson_sm_map_shmem(u32 cmd_shmem, unsigned int size)
+{
+	u32 sm_phy_base;
+
+	sm_phy_base = __meson_sm_call(cmd_shmem, 0, 0, 0, 0, 0);
+	if (!sm_phy_base)
+		return NULL;
+
+	return ioremap_cache(sm_phy_base, size);
+}
+
+/**
+ * meson_sm_call - generic SMC32 call to the secure-monitor
+ *
+ * @fw:		Pointer to secure-monitor firmware
+ * @cmd_index:	Index of the SMC32 function ID
+ * @ret:	Returned value
+ * @arg0:	SMC32 Argument 0
+ * @arg1:	SMC32 Argument 1
+ * @arg2:	SMC32 Argument 2
+ * @arg3:	SMC32 Argument 3
+ * @arg4:	SMC32 Argument 4
+ *
+ * Return:	0 on success, a negative value on error
+ */
+int meson_sm_call(struct meson_sm_firmware *fw, unsigned int cmd_index,
+		  s32 *ret, u32 arg0, u32 arg1, u32 arg2, u32 arg3, u32 arg4)
+{
+	u32 cmd;
+	s32 lret;
+
+	if (!fw->chip)
+		return -ENOENT;
+
+	cmd = meson_sm_get_cmd(fw->chip, cmd_index);
+	if (!cmd)
+		return -EINVAL;
+
+	lret = __meson_sm_call(cmd, arg0, arg1, arg2, arg3, arg4);
+
+	if (ret)
+		*ret = lret;
+
+	return 0;
+}
+EXPORT_SYMBOL(meson_sm_call);
+
+/**
+ * meson_sm_call_read - retrieve data from secure-monitor
+ *
+ * @fw:		Pointer to secure-monitor firmware
+ * @buffer:	Buffer to store the retrieved data
+ * @bsize:	Size of the buffer
+ * @cmd_index:	Index of the SMC32 function ID
+ * @arg0:	SMC32 Argument 0
+ * @arg1:	SMC32 Argument 1
+ * @arg2:	SMC32 Argument 2
+ * @arg3:	SMC32 Argument 3
+ * @arg4:	SMC32 Argument 4
+ *
+ * Return:	size of read data on success, a negative value on error
+ *		When 0 is returned there is no guarantee about the amount of
+ *		data read and bsize bytes are copied in buffer.
+ */
+int meson_sm_call_read(struct meson_sm_firmware *fw, void *buffer,
+		       unsigned int bsize, unsigned int cmd_index, u32 arg0,
+		       u32 arg1, u32 arg2, u32 arg3, u32 arg4)
+{
+	s32 size;
+	int ret;
+
+	if (!fw->chip)
+		return -ENOENT;
+
+	if (!fw->chip->cmd_shmem_out_base)
+		return -EINVAL;
+
+	if (bsize > fw->chip->shmem_size)
+		return -EINVAL;
+
+	if (meson_sm_call(fw, cmd_index, &size, arg0, arg1, arg2, arg3, arg4) < 0)
+		return -EINVAL;
+
+	if (size < 0 || size > bsize)
+		return -EINVAL;
+
+	ret = size;
+
+	/* In some cases (for example GET_CHIP_ID command),
+	 * SMC doesn't return the number of bytes read, even
+	 * though the bytes were actually read into sm_shmem_out.
+	 * So this check is needed.
+	 */
+	if (!size)
+		size = bsize;
+
+	if (buffer)
+		memcpy(buffer, fw->sm_shmem_out_base, size);
+
+	return ret;
+}
+EXPORT_SYMBOL(meson_sm_call_read);
+
+/**
+ * meson_sm_call_write - send data to secure-monitor
+ *
+ * @fw:		Pointer to secure-monitor firmware
+ * @buffer:	Buffer containing data to send
+ * @size:	Size of the data to send
+ * @cmd_index:	Index of the SMC32 function ID
+ * @arg0:	SMC32 Argument 0
+ * @arg1:	SMC32 Argument 1
+ * @arg2:	SMC32 Argument 2
+ * @arg3:	SMC32 Argument 3
+ * @arg4:	SMC32 Argument 4
+ *
+ * Return:	size of sent data on success, a negative value on error
+ */
+int meson_sm_call_write(struct meson_sm_firmware *fw, void *buffer,
+			unsigned int size, unsigned int cmd_index, u32 arg0,
+			u32 arg1, u32 arg2, u32 arg3, u32 arg4)
+{
+	s32 written;
+
+	if (!fw->chip)
+		return -ENOENT;
+
+	if (size > fw->chip->shmem_size)
+		return -EINVAL;
+
+	if (!fw->chip->cmd_shmem_in_base)
+		return -EINVAL;
+
+	memcpy(fw->sm_shmem_in_base, buffer, size);
+
+	if (meson_sm_call(fw, cmd_index, &written, arg0, arg1, arg2, arg3, arg4) < 0)
+		return -EINVAL;
+
+	if (written <= 0 || written > size)
+		return -EINVAL;
+
+	return written;
+}
+EXPORT_SYMBOL(meson_sm_call_write);
+
+/**
+ * meson_sm_get - get pointer to meson_sm_firmware structure.
+ *
+ * @sm_node:		Pointer to the secure-monitor Device Tree node.
+ *
+ * Return:		NULL is the secure-monitor device is not ready.
+ */
+struct meson_sm_firmware *meson_sm_get(struct device_node *sm_node)
+{
+	struct platform_device *pdev = of_find_device_by_node(sm_node);
+	struct meson_sm_firmware *fw;
+
+	if (!pdev)
+		return NULL;
+
+	fw = platform_get_drvdata(pdev);
+
+	put_device(&pdev->dev);
+
+	return fw;
+}
+EXPORT_SYMBOL_GPL(meson_sm_get);
+
+/**
+ * meson_sm_get_thermal_calib - Read thermal sensor calibration data.
+ * @fw:		Pointer to secure-monitor firmware.
+ * @trim_info:	Pointer to store the returned calibration data.
+ * @tsensor_id:	Sensor index to identify which sensor's calibration data
+ *		to retrieve
+ *
+ * Return: 0 on success, negative error code on failure.
+ */
+int meson_sm_get_thermal_calib(struct meson_sm_firmware *fw, u32 *trim_info,
+			       u32 tsensor_id)
+{
+	return meson_sm_call(fw, SM_THERMAL_CALIB_READ, trim_info, tsensor_id,
+			     0, 0, 0, 0);
+}
+EXPORT_SYMBOL_GPL(meson_sm_get_thermal_calib);
+
+#define SM_CHIP_ID_LENGTH	119
+#define SM_CHIP_ID_OFFSET	4
+#define SM_CHIP_ID_SIZE		12
+
+static ssize_t serial_show(struct device *dev, struct device_attribute *attr,
+			 char *buf)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+	struct meson_sm_firmware *fw;
+	uint8_t *id_buf;
+	int ret;
+
+	fw = platform_get_drvdata(pdev);
+
+	id_buf = kmalloc(SM_CHIP_ID_LENGTH, GFP_KERNEL);
+	if (!id_buf)
+		return -ENOMEM;
+
+	ret = meson_sm_call_read(fw, id_buf, SM_CHIP_ID_LENGTH, SM_GET_CHIP_ID,
+				 0, 0, 0, 0, 0);
+	if (ret < 0) {
+		kfree(id_buf);
+		return ret;
+	}
+
+	ret = sprintf(buf, "%12phN\n", &id_buf[SM_CHIP_ID_OFFSET]);
+
+	kfree(id_buf);
+
+	return ret;
+}
+
+static DEVICE_ATTR_RO(serial);
+
+static struct attribute *meson_sm_sysfs_attrs[] = {
+	&dev_attr_serial.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(meson_sm_sysfs);
+
+static const struct of_device_id meson_sm_ids[] = {
+	{ .compatible = "amlogic,meson-gxbb-sm", .data = &gxbb_chip },
+	{ /* sentinel */ },
+};
+
+static int __init meson_sm_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	const struct meson_sm_chip *chip;
+	struct meson_sm_firmware *fw;
+
+	fw = devm_kzalloc(dev, sizeof(*fw), GFP_KERNEL);
+	if (!fw)
+		return -ENOMEM;
+
+	chip = device_get_match_data(dev);
+	if (!chip)
+		return -EINVAL;
+
+	if (chip->cmd_shmem_in_base) {
+		fw->sm_shmem_in_base = meson_sm_map_shmem(chip->cmd_shmem_in_base,
+							  chip->shmem_size);
+		if (WARN_ON(!fw->sm_shmem_in_base))
+			goto out;
+	}
+
+	if (chip->cmd_shmem_out_base) {
+		fw->sm_shmem_out_base = meson_sm_map_shmem(chip->cmd_shmem_out_base,
+							   chip->shmem_size);
+		if (WARN_ON(!fw->sm_shmem_out_base))
+			goto unmap_in_base;
+	}
+
+	fw->chip = chip;
+
+	platform_set_drvdata(pdev, fw);
+
+	if (devm_of_platform_populate(dev))
+		goto unmap_out_base;
+
+	pr_info("secure-monitor enabled\n");
+
+	return 0;
+
+unmap_out_base:
+	iounmap(fw->sm_shmem_out_base);
+unmap_in_base:
+	iounmap(fw->sm_shmem_in_base);
+out:
+	return -EINVAL;
+}
+
+static struct platform_driver meson_sm_driver = {
+	.driver = {
+		.name = "meson-sm",
+		.of_match_table = of_match_ptr(meson_sm_ids),
+		.dev_groups = meson_sm_sysfs_groups,
+	},
+};
+module_platform_driver_probe(meson_sm_driver, meson_sm_probe);
+MODULE_DESCRIPTION("Amlogic Secure Monitor driver");
+MODULE_LICENSE("GPL v2");