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, 386 insertions, 0 deletions

diff --git a/drivers/pinctrl/pinconf.c b/drivers/pinctrl/pinconf.c
new file mode 100644
index 000000000..81686844d
--- /dev/null
+++ b/drivers/pinctrl/pinconf.c
@@ -0,0 +1,386 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Core driver for the pin config portions of the pin control subsystem
+ *
+ * Copyright (C) 2011 ST-Ericsson SA
+ * Written on behalf of Linaro for ST-Ericsson
+ *
+ * Author: Linus Walleij <linus.walleij@linaro.org>
+ */
+#define pr_fmt(fmt) "pinconfig core: " fmt
+
+#include <linux/array_size.h>
+#include <linux/debugfs.h>
+#include <linux/device.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/seq_file.h>
+#include <linux/slab.h>
+
+#include <linux/pinctrl/machine.h>
+#include <linux/pinctrl/pinconf.h>
+#include <linux/pinctrl/pinctrl.h>
+
+#include "core.h"
+#include "pinconf.h"
+
+int pinconf_check_ops(struct pinctrl_dev *pctldev)
+{
+	const struct pinconf_ops *ops = pctldev->desc->confops;
+
+	/* We have to be able to config the pins in SOME way */
+	if (!ops->pin_config_set && !ops->pin_config_group_set) {
+		dev_err(pctldev->dev,
+			"pinconf has to be able to set a pins config\n");
+		return -EINVAL;
+	}
+	return 0;
+}
+
+int pinconf_validate_map(const struct pinctrl_map *map, int i)
+{
+	if (!map->data.configs.group_or_pin) {
+		pr_err("failed to register map %s (%d): no group/pin given\n",
+		       map->name, i);
+		return -EINVAL;
+	}
+
+	if (!map->data.configs.num_configs ||
+			!map->data.configs.configs) {
+		pr_err("failed to register map %s (%d): no configs given\n",
+		       map->name, i);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+int pin_config_get_for_pin(struct pinctrl_dev *pctldev, unsigned int pin,
+			   unsigned long *config)
+{
+	const struct pinconf_ops *ops = pctldev->desc->confops;
+
+	if (!ops || !ops->pin_config_get) {
+		dev_dbg(pctldev->dev,
+			"cannot get pin configuration, .pin_config_get missing in driver\n");
+		return -ENOTSUPP;
+	}
+
+	return ops->pin_config_get(pctldev, pin, config);
+}
+
+int pin_config_group_get(const char *dev_name, const char *pin_group,
+			 unsigned long *config)
+{
+	struct pinctrl_dev *pctldev;
+	const struct pinconf_ops *ops;
+	int selector, ret;
+
+	pctldev = get_pinctrl_dev_from_devname(dev_name);
+	if (!pctldev) {
+		ret = -EINVAL;
+		return ret;
+	}
+
+	mutex_lock(&pctldev->mutex);
+
+	ops = pctldev->desc->confops;
+
+	if (!ops || !ops->pin_config_group_get) {
+		dev_dbg(pctldev->dev,
+			"cannot get configuration for pin group, missing group config get function in driver\n");
+		ret = -ENOTSUPP;
+		goto unlock;
+	}
+
+	selector = pinctrl_get_group_selector(pctldev, pin_group);
+	if (selector < 0) {
+		ret = selector;
+		goto unlock;
+	}
+
+	ret = ops->pin_config_group_get(pctldev, selector, config);
+
+unlock:
+	mutex_unlock(&pctldev->mutex);
+	return ret;
+}
+
+int pinconf_map_to_setting(const struct pinctrl_map *map,
+			  struct pinctrl_setting *setting)
+{
+	struct pinctrl_dev *pctldev = setting->pctldev;
+	int pin;
+
+	switch (setting->type) {
+	case PIN_MAP_TYPE_CONFIGS_PIN:
+		pin = pin_get_from_name(pctldev,
+					map->data.configs.group_or_pin);
+		if (pin < 0) {
+			dev_err(pctldev->dev, "could not map pin config for \"%s\"",
+				map->data.configs.group_or_pin);
+			return pin;
+		}
+		setting->data.configs.group_or_pin = pin;
+		break;
+	case PIN_MAP_TYPE_CONFIGS_GROUP:
+		pin = pinctrl_get_group_selector(pctldev,
+					 map->data.configs.group_or_pin);
+		if (pin < 0) {
+			dev_err(pctldev->dev, "could not map group config for \"%s\"",
+				map->data.configs.group_or_pin);
+			return pin;
+		}
+		setting->data.configs.group_or_pin = pin;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	setting->data.configs.num_configs = map->data.configs.num_configs;
+	setting->data.configs.configs = map->data.configs.configs;
+
+	return 0;
+}
+
+void pinconf_free_setting(const struct pinctrl_setting *setting)
+{
+}
+
+int pinconf_apply_setting(const struct pinctrl_setting *setting)
+{
+	struct pinctrl_dev *pctldev = setting->pctldev;
+	const struct pinconf_ops *ops = pctldev->desc->confops;
+	int ret;
+
+	if (!ops) {
+		dev_err(pctldev->dev, "missing confops\n");
+		return -EINVAL;
+	}
+
+	switch (setting->type) {
+	case PIN_MAP_TYPE_CONFIGS_PIN:
+		if (!ops->pin_config_set) {
+			dev_err(pctldev->dev, "missing pin_config_set op\n");
+			return -EINVAL;
+		}
+		ret = ops->pin_config_set(pctldev,
+				setting->data.configs.group_or_pin,
+				setting->data.configs.configs,
+				setting->data.configs.num_configs);
+		if (ret < 0) {
+			dev_err(pctldev->dev,
+				"pin_config_set op failed for pin %d\n",
+				setting->data.configs.group_or_pin);
+			return ret;
+		}
+		break;
+	case PIN_MAP_TYPE_CONFIGS_GROUP:
+		if (!ops->pin_config_group_set) {
+			dev_err(pctldev->dev,
+				"missing pin_config_group_set op\n");
+			return -EINVAL;
+		}
+		ret = ops->pin_config_group_set(pctldev,
+				setting->data.configs.group_or_pin,
+				setting->data.configs.configs,
+				setting->data.configs.num_configs);
+		if (ret < 0) {
+			dev_err(pctldev->dev,
+				"pin_config_group_set op failed for group %d\n",
+				setting->data.configs.group_or_pin);
+			return ret;
+		}
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+int pinconf_set_config(struct pinctrl_dev *pctldev, unsigned int pin,
+		       unsigned long *configs, size_t nconfigs)
+{
+	const struct pinconf_ops *ops;
+
+	ops = pctldev->desc->confops;
+	if (!ops || !ops->pin_config_set)
+		return -ENOTSUPP;
+
+	return ops->pin_config_set(pctldev, pin, configs, nconfigs);
+}
+
+#ifdef CONFIG_DEBUG_FS
+
+static void pinconf_show_config(struct seq_file *s, struct pinctrl_dev *pctldev,
+				unsigned long *configs, unsigned int num_configs)
+{
+	const struct pinconf_ops *confops;
+	int i;
+
+	if (pctldev)
+		confops = pctldev->desc->confops;
+	else
+		confops = NULL;
+
+	for (i = 0; i < num_configs; i++) {
+		seq_puts(s, "config ");
+		if (confops && confops->pin_config_config_dbg_show)
+			confops->pin_config_config_dbg_show(pctldev, s,
+							    configs[i]);
+		else
+			seq_printf(s, "%08lx", configs[i]);
+		seq_putc(s, '\n');
+	}
+}
+
+void pinconf_show_map(struct seq_file *s, const struct pinctrl_map *map)
+{
+	struct pinctrl_dev *pctldev;
+
+	pctldev = get_pinctrl_dev_from_devname(map->ctrl_dev_name);
+
+	switch (map->type) {
+	case PIN_MAP_TYPE_CONFIGS_PIN:
+		seq_puts(s, "pin ");
+		break;
+	case PIN_MAP_TYPE_CONFIGS_GROUP:
+		seq_puts(s, "group ");
+		break;
+	default:
+		break;
+	}
+
+	seq_printf(s, "%s\n", map->data.configs.group_or_pin);
+
+	pinconf_show_config(s, pctldev, map->data.configs.configs,
+			    map->data.configs.num_configs);
+}
+
+void pinconf_show_setting(struct seq_file *s,
+			  const struct pinctrl_setting *setting)
+{
+	struct pinctrl_dev *pctldev = setting->pctldev;
+	const struct pinctrl_ops *pctlops = pctldev->desc->pctlops;
+	struct pin_desc *desc;
+
+	switch (setting->type) {
+	case PIN_MAP_TYPE_CONFIGS_PIN:
+		desc = pin_desc_get(setting->pctldev,
+				    setting->data.configs.group_or_pin);
+		seq_printf(s, "pin %s (%d)", desc->name,
+			   setting->data.configs.group_or_pin);
+		break;
+	case PIN_MAP_TYPE_CONFIGS_GROUP:
+		seq_printf(s, "group %s (%d)",
+			   pctlops->get_group_name(pctldev,
+						   setting->data.configs.group_or_pin),
+			   setting->data.configs.group_or_pin);
+		break;
+	default:
+		break;
+	}
+
+	/*
+	 * FIXME: We should really get the pin controller to dump the config
+	 * values, so they can be decoded to something meaningful.
+	 */
+	pinconf_show_config(s, pctldev, setting->data.configs.configs,
+			    setting->data.configs.num_configs);
+}
+
+static void pinconf_dump_pin(struct pinctrl_dev *pctldev,
+			     struct seq_file *s, int pin)
+{
+	const struct pinconf_ops *ops = pctldev->desc->confops;
+
+	/* no-op when not using generic pin config */
+	pinconf_generic_dump_pins(pctldev, s, NULL, pin);
+	if (ops && ops->pin_config_dbg_show)
+		ops->pin_config_dbg_show(pctldev, s, pin);
+}
+
+static int pinconf_pins_show(struct seq_file *s, void *what)
+{
+	struct pinctrl_dev *pctldev = s->private;
+	unsigned int i, pin;
+
+	seq_puts(s, "Pin config settings per pin\n");
+	seq_puts(s, "Format: pin (name): configs\n");
+
+	mutex_lock(&pctldev->mutex);
+
+	/* The pin number can be retrived from the pin controller descriptor */
+	for (i = 0; i < pctldev->desc->npins; i++) {
+		struct pin_desc *desc;
+
+		pin = pctldev->desc->pins[i].number;
+		desc = pin_desc_get(pctldev, pin);
+		/* Skip if we cannot search the pin */
+		if (!desc)
+			continue;
+
+		seq_printf(s, "pin %d (%s): ", pin, desc->name);
+
+		pinconf_dump_pin(pctldev, s, pin);
+		seq_putc(s, '\n');
+	}
+
+	mutex_unlock(&pctldev->mutex);
+
+	return 0;
+}
+
+static void pinconf_dump_group(struct pinctrl_dev *pctldev,
+			       struct seq_file *s, unsigned int selector,
+			       const char *gname)
+{
+	const struct pinconf_ops *ops = pctldev->desc->confops;
+
+	/* no-op when not using generic pin config */
+	pinconf_generic_dump_pins(pctldev, s, gname, 0);
+	if (ops && ops->pin_config_group_dbg_show)
+		ops->pin_config_group_dbg_show(pctldev, s, selector);
+}
+
+static int pinconf_groups_show(struct seq_file *s, void *what)
+{
+	struct pinctrl_dev *pctldev = s->private;
+	const struct pinctrl_ops *pctlops = pctldev->desc->pctlops;
+	unsigned int selector = 0;
+	unsigned int ngroups;
+
+	if (!pctlops->get_groups_count || !pctlops->get_group_name)
+		return 0;
+
+	ngroups = pctlops->get_groups_count(pctldev);
+
+	seq_puts(s, "Pin config settings per pin group\n");
+	seq_puts(s, "Format: group (name): configs\n");
+
+	while (selector < ngroups) {
+		const char *gname = pctlops->get_group_name(pctldev, selector);
+
+		seq_printf(s, "%u (%s): ", selector, gname);
+		pinconf_dump_group(pctldev, s, selector, gname);
+		seq_putc(s, '\n');
+		selector++;
+	}
+
+	return 0;
+}
+
+DEFINE_SHOW_ATTRIBUTE(pinconf_pins);
+DEFINE_SHOW_ATTRIBUTE(pinconf_groups);
+
+void pinconf_init_device_debugfs(struct dentry *devroot,
+			 struct pinctrl_dev *pctldev)
+{
+	debugfs_create_file("pinconf-pins", 0444,
+			    devroot, pctldev, &pinconf_pins_fops);
+	debugfs_create_file("pinconf-groups", 0444,
+			    devroot, pctldev, &pinconf_groups_fops);
+}
+
+#endif