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, 282 insertions, 0 deletions

diff --git a/drivers/pinctrl/pinctrl-generic.c b/drivers/pinctrl/pinctrl-generic.c
new file mode 100644
index 000000000..9759b0186
--- /dev/null
+++ b/drivers/pinctrl/pinctrl-generic.c
@@ -0,0 +1,282 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#define pr_fmt(fmt) "generic pinconfig core: " fmt
+
+#include <linux/array_size.h>
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/slab.h>
+
+#include <linux/pinctrl/pinconf-generic.h>
+#include <linux/pinctrl/pinconf.h>
+#include <linux/pinctrl/pinctrl.h>
+
+#include "core.h"
+#include "pinconf.h"
+#include "pinctrl-utils.h"
+#include "pinmux.h"
+
+int pinctrl_generic_to_map(struct pinctrl_dev *pctldev, struct device_node *parent,
+			   struct device_node *np, struct pinctrl_map **maps,
+			   unsigned int *num_maps, unsigned int *num_reserved_maps,
+			   const char **group_names, unsigned int ngroups,
+			   void *data, unsigned int *pins, unsigned int npins)
+{
+	struct device *dev = pctldev->dev;
+	unsigned int num_configs;
+	const char *group_name;
+	unsigned long *configs;
+	int ret, reserve = 1;
+
+	group_name = devm_kasprintf(dev, GFP_KERNEL, "%pOFn.%pOFn", parent, np);
+	if (!group_name)
+		return -ENOMEM;
+
+	group_names[ngroups] = group_name;
+
+	ret = pinctrl_utils_reserve_map(pctldev, maps, num_reserved_maps, num_maps, reserve);
+	if (ret)
+		return ret;
+
+	ret = pinctrl_utils_add_map_mux(pctldev, maps, num_reserved_maps, num_maps, group_name,
+					parent->name);
+	if (ret < 0)
+		return ret;
+
+	ret = pinctrl_generic_add_group(pctldev, group_name, pins, npins, data);
+	if (ret < 0)
+		return dev_err_probe(dev, ret, "failed to add group %s: %d\n",
+				     group_name, ret);
+
+	ret = pinconf_generic_parse_dt_config(np, pctldev, &configs, &num_configs);
+	if (ret)
+		return dev_err_probe(dev, ret, "failed to parse pin config of group %s\n",
+			group_name);
+
+	if (num_configs == 0)
+		return 0;
+
+	ret = pinctrl_utils_reserve_map(pctldev, maps, num_reserved_maps, num_maps, reserve);
+	if (ret)
+		return ret;
+
+	ret = pinctrl_utils_add_map_configs(pctldev, maps, num_reserved_maps, num_maps, group_name,
+					    configs,
+			num_configs, PIN_MAP_TYPE_CONFIGS_GROUP);
+	kfree(configs);
+	if (ret)
+		return ret;
+
+	return 0;
+};
+EXPORT_SYMBOL_GPL(pinctrl_generic_to_map);
+
+static int pinctrl_generic_pins_function_dt_subnode_to_map(struct pinctrl_dev *pctldev,
+							   struct device_node *parent,
+							   struct device_node *np,
+							   struct pinctrl_map **maps,
+							   unsigned int *num_maps,
+							   unsigned int *num_reserved_maps,
+							   const char **group_names,
+							   unsigned int ngroups)
+{
+	struct device *dev = pctldev->dev;
+	unsigned int pin, *pins;
+	const char **functions;
+	int npins, ret;
+
+	npins = of_property_count_u32_elems(np, "pins");
+
+	if (npins < 1) {
+		dev_err(dev, "invalid pinctrl group %pOFn.%pOFn %d\n",
+			parent, np, npins);
+		return npins;
+	}
+
+	pins = devm_kcalloc(dev, npins, sizeof(*pins), GFP_KERNEL);
+	if (!pins)
+		return -ENOMEM;
+
+	functions = devm_kcalloc(dev, npins, sizeof(*functions), GFP_KERNEL);
+	if (!functions)
+		return -ENOMEM;
+
+	for (int i = 0; i < npins; i++) {
+		ret = of_property_read_u32_index(np, "pins", i, &pin);
+		if (ret)
+			return ret;
+
+		pins[i] = pin;
+
+		ret = of_property_read_string(np, "function", &functions[i]);
+		if (ret)
+			return ret;
+	}
+
+	return pinctrl_generic_to_map(pctldev, parent, np, maps, num_maps,
+				      num_reserved_maps, group_names, ngroups,
+				      functions, pins, npins);
+}
+
+static int pinctrl_generic_pinmux_dt_subnode_to_map(struct pinctrl_dev *pctldev,
+						    struct device_node *parent,
+						    struct device_node *np,
+						    struct pinctrl_map **maps,
+						    unsigned int *num_maps,
+						    unsigned int *num_reserved_maps,
+						    const char **group_names,
+						    unsigned int ngroups)
+{
+	struct device *dev = pctldev->dev;
+	unsigned int *pins, *muxes;
+	int npins, ret;
+
+	npins = of_property_count_u32_elems(np, "pinmux");
+
+	if (npins < 1) {
+		dev_err(dev, "invalid pinctrl group %pOFn.%pOFn %d\n",
+			parent, np, npins);
+		return npins;
+	}
+
+	pins = devm_kcalloc(dev, npins, sizeof(*pins), GFP_KERNEL);
+	if (!pins)
+		return -ENOMEM;
+
+	muxes = devm_kcalloc(dev, npins, sizeof(*muxes), GFP_KERNEL);
+	if (!muxes)
+		return -ENOMEM;
+
+	for (int i = 0; i < npins; i++) {
+		unsigned int pinmux;
+
+		ret = of_property_read_u32_index(np, "pinmux", i, &pinmux);
+		if (ret)
+			return ret;
+
+		pins[i] = pinmux >> 16;
+		muxes[i] = pinmux & GENMASK(15, 0);
+	}
+
+	return pinctrl_generic_to_map(pctldev, parent, np, maps, num_maps,
+				      num_reserved_maps, group_names, ngroups,
+				      muxes, pins, npins);
+}
+
+static int pinctrl_generic_dt_node_to_map(struct pinctrl_dev *pctldev,
+					  struct device_node *np,
+					  struct pinctrl_map **maps,
+					  unsigned int *num_maps,
+					  int (dt_subnode_to_map)(
+						  struct pinctrl_dev *,
+						  struct device_node *,
+						  struct device_node *,
+						  struct pinctrl_map **,
+						  unsigned int *,
+						  unsigned int *,
+						  const char **,
+						  unsigned int))
+{
+	struct device *dev = pctldev->dev;
+	struct device_node *child_np;
+	const char **group_names;
+	unsigned int num_reserved_maps = 0;
+	int ngroups = 0;
+	int ret;
+
+	*maps = NULL;
+	*num_maps = 0;
+
+	/*
+	 * Check if this is actually the pins node, or a parent containing
+	 * multiple pins nodes.
+	 */
+	if (!of_property_present(np, "pins"))
+		goto parent;
+
+	group_names = devm_kcalloc(dev, 1, sizeof(*group_names), GFP_KERNEL);
+	if (!group_names)
+		return -ENOMEM;
+
+	ret = dt_subnode_to_map(pctldev, np, np, maps, num_maps,
+				&num_reserved_maps, group_names, ngroups);
+	if (ret) {
+		pinctrl_utils_free_map(pctldev, *maps, *num_maps);
+		return dev_err_probe(dev, ret, "error figuring out mappings for %s\n", np->name);
+	}
+
+	ret = pinmux_generic_add_function(pctldev, np->name, group_names, 1, NULL);
+	if (ret < 0) {
+		pinctrl_utils_free_map(pctldev, *maps, *num_maps);
+		return dev_err_probe(dev, ret, "error adding function %s\n", np->name);
+	}
+
+	return 0;
+
+parent:
+	for_each_available_child_of_node(np, child_np)
+		ngroups += 1;
+
+	group_names = devm_kcalloc(dev, ngroups, sizeof(*group_names), GFP_KERNEL);
+	if (!group_names)
+		return -ENOMEM;
+
+	ngroups = 0;
+	for_each_available_child_of_node_scoped(np, child_np) {
+		ret = dt_subnode_to_map(pctldev, np, child_np, maps, num_maps,
+					&num_reserved_maps, group_names, ngroups);
+		if (ret) {
+			pinctrl_utils_free_map(pctldev, *maps, *num_maps);
+			return dev_err_probe(dev, ret, "error figuring out mappings for %s\n",
+					     np->name);
+		}
+
+		ngroups++;
+	}
+
+	ret = pinmux_generic_add_function(pctldev, np->name, group_names, ngroups, NULL);
+	if (ret < 0) {
+		pinctrl_utils_free_map(pctldev, *maps, *num_maps);
+		return dev_err_probe(dev, ret, "error adding function %s\n", np->name);
+	}
+
+	return 0;
+}
+
+/*
+ * For platforms that do not define groups or functions in the driver, but
+ * instead use the devicetree to describe them. This function will, unlike
+ * pinconf_generic_dt_node_to_map() etc which rely on driver defined groups
+ * and functions, create them in addition to parsing pinconf properties and
+ * adding mappings.
+ */
+int pinctrl_generic_pins_function_dt_node_to_map(struct pinctrl_dev *pctldev,
+						 struct device_node *np,
+						 struct pinctrl_map **maps,
+						 unsigned int *num_maps)
+{
+	return pinctrl_generic_dt_node_to_map(pctldev, np, maps, num_maps,
+					      &pinctrl_generic_pins_function_dt_subnode_to_map);
+}
+EXPORT_SYMBOL_GPL(pinctrl_generic_pins_function_dt_node_to_map);
+
+/*
+ * For platforms that do not define groups or functions in the driver, but
+ * instead use the devicetree to describe them. This function will, unlike
+ * pinconf_generic_dt_node_to_map() etc which rely on driver defined groups
+ * and functions, create them in addition to parsing pinconf properties and
+ * adding mappings.
+ *
+ * It assumes that the upper 16 bits of the pinmux items contain the pin
+ * and the lower 16 the mux setting.
+ */
+int pinctrl_generic_pinmux_dt_node_to_map(struct pinctrl_dev *pctldev,
+					  struct device_node *np,
+					  struct pinctrl_map **maps,
+					  unsigned int *num_maps)
+{
+	return pinctrl_generic_dt_node_to_map(pctldev, np, maps, num_maps,
+					      &pinctrl_generic_pinmux_dt_subnode_to_map);
+};
+EXPORT_SYMBOL_GPL(pinctrl_generic_pinmux_dt_node_to_map);